Food and Bio Process Engineering

IFood and Bio Process Engineering Dairy Technology H.G. Kessler = Fifth revised and extended edition with 923 figures and 109 tables ISBN 3-9802378-5-0 Verlag A. Kessler (Publishing House A. Kessler) • München II Professor Dr.-Ing. Heinz-Gerhard Kessler = Until his death 29. November 1998 he held positions as: Professor for food process engineering and dairy technology at the Technical University of Munich Head of the institute for dairy science and food process engineering Director of the institute for food process engineering at the research centre for dairy and food products Weihenstephan Technical University of Munich D-85350 Freising-Weihenstephan, Germany Copyright 2002 by Verlag A. Kessler (Publishing House A. Kessler) All rights are reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, translation or otherwise, without the prior written permission of the publisher. Die Deutsche Bibliothek - CIP-Einheitsaufnahme Die Deutsche Bibliothek - CIP-Catalguing-in-Publication-Data Printed in Germany 2002 Druckerei Rieder GmbH, 87437 Kempten-St. Mang, Germany; www.rieder-druck.de ISBN 3-9802378-5-0 kessler - food and bio process engineering - dairy technology D-80687 München Verlag A.Kessler (Publishing House A. Kessler), Agnes-Bernauer-Str. 174, D-80687 München (Munich) Germany Internet: www.verlag-kessler.de e-mail: [email protected] Build-up of gel structures effects of stabilisation and destabilisation. Due to its practical importance this chapter was significantly expanded and revised which led to the new name: “Heat Treatment. and the contents of calcium and lactose. This book provides students with the bridge between university and college on the one hand and industry on the other that they need by showing not only the theoretical background but also practical examples. For students often the link between the technologies learned during their study and the practical application in industry is missing. and ourselves it was a noble commitment to finish his work. Since the first edition. my mother. The progressive evolution can be seen best by comparing the number of figures with the previous editions: First Edition Second Edition Third Edition Fourth Edition Fifth Edition (1976) (1981) (1988) (1996) (2002) German English German German English 355 459 688 883 923 Figures Figures Figures Figures Figures In comparison with the first English edition in 1981 changes and additions made to the present edition can be summarised as follows: Chapter 6 From the beginning the main focus was set on heat treatment and effects. the book was continuously revised and updated to include latest developments in food processing. sealing materials and fats. which was published 1976. • Interactions between milk proteins and fat globules due to heating and environmental conditions.III Preface Preamble to the fifth edition Shortly before our father died November 1998 he finalised the manuscript of the fifth edition. Processes and Effects – Micro-organisms and Conditions of Inactivation”. ratio casein/ whey protein. • Heat induced whey protein denaturation as function of the protein concentration. The fifth edition of this popular textbook and handbook on food-. After 1981 the book is published in English for the second time. environmental conditions. The original idea of our father in the seventies was to create a book summarising the diverse technologies of food processing focusing especially on the processing impact on the product. This observation led to the practical character of the book targeting engineers and technologists in the food and dairy industry. For his former co-workers of his institute. The additions consider: • Special effects on the inactivation kinetics as the concentration of certain ingredients. unfortunately he was not able to complete the work on the book. relative humidity. bioprocessing and dairy technology was thoroughly revised and significantly expanded. Chapter 13 Completely revised was chapter 13 “ Radiation Treatment” which was renamed to “Alternative Methods of Preservation”. since it comprises additionally: • Ohmic and conductive heating • Microwave heating • High pressure treatment Chapter 15 “Technology of Cream and Butter” was expanded by the following topics: • • • Critical shear rated for the mechanical stability of fat globules Technological impacts on the whipability of cream Production clarified butter and cholesterol reduction in the milk fat . During his industrial period in the sixties our father recognised that it is of great importance to translate the scientific knowledge on products and processes into a practical language to be applied in the food manufacturing industry. C. D. Obermeyer. M. H. J. J. C. R. Hammelehle. B. Welchner. C. Trgo. J. W. J. B. Beyer. M. Post. Gernedel. B. Horak. Kersten. comprising salt. Borst. U. Fink. Nassauer. G. D. surfaces tension and physiologic calorific values of milk products Determination of total mass. Wilde.and protein fouling. concentration and composition impacts Concentration and composition of cleaning agents Rinsing and displacement of high viscous products Chapter 23 “Physical data” physical properties and composition data of milk were added: • • • • Constituents and composition of milk Viscosity. Eisenmann. Moosbauer. C. S. Especially we like to express our gratitude to the former Ph. Behringer. Hege. de Carvalho. S. Helming. pH.IV Chapter 17 Important changes were made on chapter 17 which now includes: • • • • • Influence of whey protein denaturation and homogenisation on gel structure Coagulation characteristics and gel structure due to direct acidification with impact of technology product composition Effect of shearing on gel structure Acidification and gel structure formation by Glucono-δ-lactone Production of yoghurt aroma concentrate Chapter 18 “ Manufacture of Ice Cream – Ice Crystals” was updated and extended by: • • • • Structure of ice cream Melting characteristic Heat transfer and residence time in scraped surface freezer Ice crystal growth Chapter 19 “ Whey processing” was renamed to “ Biotechnology and Whey Processing” due to the inclusion of: • • • • • Kinetics of cell growth Enzyme kinetics Aerobic bioprocesses – oxygen supply Starter cultures and enzymes Bioreactors Chapter 21 Due to its practical significance chapter 21 “Fouling – Cleaning – Sanitising – Rinsing and Associate Processes at the Interface” was expanded to include: • • • Fouling. I. Geyer. Boheim. Hager. Hegenauer. F. J. Schraml. Knapp. T. C. P. C. U. Kennel. Additionally we like to give our thanks to his former co–workers as H. C. Weber and many not explicitly mentioned. Bäurle. P. Plock. thermal conductivity. A. who supported and contributed significantly to the book with their research work and the computer aided layout of the diagrams. R. J. M. S. B. Schindler. H. Kulozik. R. J. Meier. Schreiber. Löffler. B. enthalpy. students of our father. Bals. F. G. density. Steffl. A. Eibel. S. K. R. Pietschmann. . Fink. H. Koxholt. J. Fertsch. Spiegel. A. who contributed importantly with their research work to the book. Baumgartner. A. Piepenstock. Rademacher. W. R. Schkoda. A. Huber. Huss. heat capacity. Schwab. J. B. S. Dannenberg. Eberhard. Hechler. Besner. M. Hinrichs. reaction kinetics. P. H. R.-J. F. Pfeiffer. Keim. mass fraction Solubility of gases in liquids Many research results included in this book were originated from the former institute of our father. Fiedler. Pfeifer. Dr. G. Sandu and M. 2002 Dr. Bäurle. This book is addressed both to food technologists working within the food industry and to students. Nassauer. The author’s purpose in writing such a book was to create a textbook for students of food technology and. I. It will be of interest to all who are concerned with food processing and the design of food processing plants: process engineers. Dr. which we wouldn’t have forgone. Also we like to point out the help of Prof. a basic practical guide for use within the industry. especially to H. Sandu we like to express our in dept gratitude for the scientific and English revision. and industrial managers. treatment of effluents. Prof. Jörg Hinrichs and Dr.-Ing. we like to give our thanks to Dr. Kammerlehner. which was published in German in 1976.V For the translation into the English language. Dr. Special attention has been paid to exact descriptions of processing methods in this book. principles of importance to the entire food processing industry are the major concern of the book. for which we are very grateful to them. is based upon the most up-to-date scientific and engineering knowledge.Ing. J. Ulrich Kulozik. Dr. Dr. P. at the same time. Horak. which is revised and extended. proved that for the first time the gap between food processing methods and technology for practical. Wotzilka. hygienists. bacteriologists. Emphasis is placed on dairy technology because on the dairy industry’s prominent position within the food industry. Munich. to ensure that the book does not become out-of-date too soon. Other topics dealt with which are of interest to those within the sphere of food technology and which are of environmental and legislative importance are drinking water. However. Heinz-Gerhard Kessler . Above all I would like to thank my secretary Mrs. design engineers. Dr. Especially Dr.-Ing. The author wishes to express his gratitude to his co-workers for their assistance and their aid in preparing this book. which would include many examples of practical applications and important data on materials. In the past three years we had to sacrifice our free time and holidays for finalising the book beside our professional obligations. The basic principles of processing methods and their effects upon food products are extensively treated. Hobmeier for typing this book. Munich-Weihenstephan. Ulrich Kessler and Nicole Kessler Preamble to the first English edition The great success of this book. it was an interesting and demanding period of time. he did for many chapters of the book. chemists. 1981 Prof. Helming.Gernedel.Walenta. research and teaching purposes has been bridged. W. in spite of rapid technological advances. W. cleaning and sterilizing. The English edition. J. Brigitte Rademacher for assisting us in final correction work. Dr. C. High Pressure Extraction (13 p..) [6→12] 23 Physical Data – Conversion Factors (23 p..) [27→28] 3 Centrifugation .Extraction . 26 t..Sorption Properties .) [23→46] 8 Climate .) [8→50] 16 Cheese Manufacture – Dairy Protein Products (33 p. 37 f. 5 tables) [18→24] *) 2 Principles of Heat Transfer and Thermodynamics (24 p.Homogenisation and Stability of Cream (24 p.. .Microorganisms and Conditions of Inactivation (86 p.. 24 f. 1 t. 17 f. 17 f.. Kessler . 5 t.VI Food and Bio Process Engineering . 147 f. 9 t..Separation . 1 t.) [14→17] 10 Drying ..2002 1 Principles of Flow Mechanics (16 pages.. 25 f.) [23→73] 22 Water and Effluent Treatment (14 p.. 43 f. 35 f.Cyclone Separation (15 p.) [17→20] 12 Distillation . 14 t...) [65→147] 7 Evaporation (27 p... 73 f.) [13→13] 9 Dry Products .Rinsing and Associate Processes at the Interface (50 p..Changes in the Condition of Moist Air (9 p.Instantising (37 p.. This consideration reflects well the technological development of the industry.. 20 f.. 2 t. shown by the numbers in the square brackets. 54 f. 7 t..) [19→25] 13 Alternative Methods of Preservation (27 p. 24 figures....Freeze Concentration (22 p.) [5→35] 20 Tanks – Pumps – Stirrers – Mixers – Grinders ( 18 p.. 39 f.Fifth Edition . 5 t. 1 t. 1 t.Dairy Technology H. 37 f.) [3→39] 14 Packaging . 18 f.) [8→18] 19 Biotechnology and Whey Processing (38 p. Processes and Effects .....Ice Crystals (12 p.Sanitising . 1 t.) [8→24] *) The ongoing development of the book and especially the extension of each chapter can be taken from the number of figures in comparison with the last English edition. 1 t. 13 f. 9 t.Drying processes and plants .) [29→37] 21 Fouling .) [13→37] 17 Technology of Cultured Milk Products – Structure of Gels – Direct Acidification – Special Milk Products and Use of Hydrocolloids (33 p. 28 f.. 6 t. 5 t.) [52→56] 11 Cooling – Freezing . 46 f.G. 12 f. 6 t.. 83 f..) [14→17] 4 Membrane Separation-Processes (50 p.. 50 f. 56 f..) [16→54] 18 Manufacture of Ice Cream ..Cleaning .Filling (21 p. 1 t.) [14→43] 6 Heat Treatment...Keeping Quality (9 p...) [46→83] 5 Emulsification .. 25 f. 3t..) [18→25] 15 Technology of Cream and Butter (40 p.. ....... 9 Diffusion ...................................................... 1 1........................................................................................ 31 Heat Penetration during Short Contact Time .............................VII Table of Content 1 Principles of Flow Mechanics and Residence Time Distributions in Pipe Systems ..........................................1 1..4........................................................................................ Stationary Substances ...............1 2.................................................9......................................................2 1..............................5 2......5...........................................Equivalent Diameter .............................................................8 2.......4.25 Heat Exchange .........18 2...............................2 General Concepts ....................................2..................... 6 Distribution of Liquid Velocities in Pipes ......39 ......................................... 3 Reynolds Number .. 27 Efficiency of Heat Exchange ...........................................4..................................................2......20 Thermal Radiation ........................4..........4 Velocity Distribution...................7 2............... Laminar and Turbulent Flow ...............2 2...........28 Unsteady Heat Flow in Homogeneous...3 1.......... 8 Turbulent Flow .......................................................................................Shear Stress ......3 2....2 2.................................... 38 2......... 8 Molecular Flow According to Knudsen ..................................................................................................2 1.............................................................................7........ 21 Heat Transmission by Convection – Heat Transfer ....................................................................23 Working Formulas for the Calculation of Heat Transfer ..............5 1..................................... 18 Balances for the Determination of the State of a Mixture ..................... 20 Heat Conduction ......... 17 2.....................9 2................9..................3 1.... 23 Dimensionless Ratios ................................................................. 22 Overall Heat Transfer ..................................4 1...... 30 Temperature Fields for Plates.......1 2.................................2 2.........................................3 Expansion of Solids and Liquids .....30 Pattern of Temperature Changes in te Area of Heat Penetration ...........................................3 1...............................................1 1.............4 2...........5.........................................................................3 2.... 8 Mass Flow for Various Types of Motion ...........................................1 1..................................................................................... 18 Expansion of Gases ................2 1.10 Changes of State and Cyclic Processes .............. Cylinders and Spheres ...9....................................................7............1 2.....................17 Thermal Expansion ............................12 2 Principles of Heat Transfer and Thermodynamics ..................................1 Equation of Motion ....... 4 Pressure Drop in Pipe Line Systems .......................2 2................................................................................ 10 1............................................................................27 Mean Logarithmic Temperature Difference ......................................................................................................................................8 Laminar Flow ................................................................4 Continuity Equation ..........................................................................1 Discharge Velocity -Momentum ...........................................................................................4........................................................... 27 Cooling and Heating of a Body which is at all Times in Thermal Equilibrium ..................2 Flow Through Pipe Systems ...........4 2......................................4.................................................................... 3 Viscosity ................................4....1 2....19 Heat Transfer ...10 Residence Time Distribution .....................5 1.............4.......................5..7 Mass Flow Through Aggregates and Porous Goods with Uniform Porosity .6 2.............6 1.........................................................................................4................................5.........3 1..........1 2.............................................................. ................... 41 3....................Cyclone Separation ................5 3..................53 Cyclones ....7...........1 4...................................................7..........................................................................................................................6.43 Disc Bowl Centrifuge ...................... 89 Effects Induced by Hyperfiltration Layers ............................. 52 Stabilisation of Liquid Milk .... 71 Relationship between Consistency Factor and Flow Behaviour Index . 73 Microfiltration .....................................1 4.....................72 Industrial Applications ...................... 49 Clarification of Milk ........5 3.....................4 4.........................................................96 .....................................4 4............41 Velocity of Particles in a Gravitational Field ................................... 52 3................................................................................................................2 4.6................... 48 Cream Separation and Adjustment of the Fat Content ...................................................................................41 Fat Globule Diameter Distribution in Milk .......... 61 Factors Influencing the Hydraulic Resistance ..........................................................................3.....................................60 4..............................................................................3....................7 3..............................................................5 4..........7.............5........................................................ 63 Factors Influencing the Deposit Thickness ................................................................................................................................................ 72 Ultrafiltration in Dairy Industry ......................................................3 3...................8 Other Types of Centrifuge and Methods of Application ....70 Effect of Total Solids Content ...... 68 Effect of Low Molecular Compounds in Milk ....................59 Process Parameters in Ultrafiltration ......6..............................................................5.............................................................................6 Flux of an aqueous Protein Suspension in Tubular and Annular Flow Systems ..............3 3...........................................56 Hydraulic Resistances in Filtration ...........................................................................3...........92 4............................................. and Whey ........................... 86 Effect of Deposition Layer ..........................................3 Basics of Membrane Separation .....................................................................8 Applications of Reverse Osmosis ............ 90 4..........6 3.......... 72 Ultrafiltration in Food Technology ..............3.41 Velocity of Particles in a Centrifugal Field ........................1 4................2 4.........2 4..........1 3......................................................................4 4.. 47 Regulating the Fat Content .........................42 Mechanical Strength of a Centrifuge Bowl ......... 51 Quark Separator .......................................................2 4..........................2 3.............5 4.......................VIII 3 Centrifugation ...................6...................................................54 4 Membrane Separation-Processes.........................................................6......4.......79 Reverse Osmosis .......... 65 Ultrafiltration of Skim Milk............................. 69 Rheological Properties of UF-Concentrates of Milk ..........9 Nanofiltration ....................................................4 3.............7 4.......2 3............... 70 Effect of Protein Denaturation .................................................................4............................................... 83 Impact of the Concentration Excess at the Membrane Surface on Mass Transfer .........6..........................1 3.......................5 4......................10 Pervaporation ...............................6 4....6 Application of Separation Processes in the Dairy Industry ......................................................................................................... 56 4...............7.............. 46 Power Requirement .....................44 3.......................... 86 Transport of Low Molecular Species ..........2 4............................6......3 4............................................3 4................................................................................4.....................7 Construction and principle of Operation .....1 4...........3..............................7......................................................................6........................... Whole Milk.....Separation from the Gas Phase ......82 Osmotic Pressure ................................. 83 Membrane Transport in Reverse Osmosis ..................Separation ...............3 4...........4 3..................................................................8 3.................................................95 4. 44 Separation and Mass Flow Rate .........1 4.....................7.................... ....113 Homogenisation of Cream ..............................................1 Radio Nuclids Elements in Milk ....................................141 Pasteurisation ........................................................ 121 Fat Globule Membrane and Quality of Homogenised Products ....................................................... Pasteurisation......................................... 106 5..........................................................................................................116 Effect of Homogenising Pressure ..............................6.....2 5................... Emulsions and Emulsifiers ..........123 Membrane of Fat Globules ..................................................................... 116 Concentration Effects .......... 119 Temperature Effect ..................127 General Effects of Homogenisation ...............................1....................................... 130 External Effects on the Behaviour of Microorganisms ................................... Applications .................................................. 102 4...1...130 6...................... 123 Heating-Induced Changes of Globule Membrane .... 103 4........................................99 Ionic Exchange .....................................................................................................12 4....................2............3..2...3.................................. 124 Heating............................... 111 Technical Aspects of Homogenisation ....................................1....................................................................................and z-Values of Psychrotrophic Bacteria and Their Enzymes ...........106 Manufacturing of Emulsions ....2.................... under Different Conditions ..............................................5.............................................3 5...............2 5...........14...............5....2 5......................................13 4........................................................................................................................ 104 5 Emulsification ....4 5............134 Reaction Kinetics ...................................... 118 Effect of Back-Pressure ....... 137 The Effect of Temperature on the Reaction .............................................................6.3 5.................1 5............................11 4..................7 5......................................................................97 Electrodialysis ......and Storage-Induced Changes of Globule Membrane ....................................1 5........... 130 6............................................................................6...............129 6 Heat Treatment......................................................Microorganisms and Their Behaviour Against External Effects .....................................1 6................................................1 6............4 5........................................................5................................1 6....................................1 5..... 145 ...5 5............................................................................3 6......... 130 Microorganisms and Enzymes .........8 Homogenisation of Acidic Dairy Products ...2............................4....................IX 4.................................2 5.................... Sterilisation ......................................3 6.............. 120 Effect of Homogenising Pressure....14 Technical Aspects of Membrane Separation ................................. 134 The Inactivation of Microorganisms ..........6............... 126 5.................................................5 5......................Homogenisation and Stability of Cream ...... 124 Homogenisation-Induced Changes of Globule Membrane .......................3........................................2 Decontamination by Electrodialysis ...........................2 Purpose of the Heat Treatment ....................................................3 6...1 Purpose of the Heat Treatment ...........3 Emulsification.............3 Decontamination by Ionic Exchange ................................................. 110 Size-Characterisation of Fat Globules ...............Microorganisms and Conditions of Inactivation ............102 4..........2 6.......The Effect of Time .................14............. 132 The Reaction Kinetics of Heat Induced Changes ............................2 6..................... Processes and Effects ..............................................101 Treatment of Radioactively Contaminated Milk .....................................3..........................5...........3 5........................................6 5......................... 142 Thermisation .............. 141 Heat Inactivation of Microorganisms .......................107 Homogenisation of Milk and Milk-Products ............................................4 6.........5...........................14.................................2 6........................ 110 Operation Basics ..................3..........................1 5. 139 D.....................................Thermisation.....109 5.................................... ..............................4 Temperature Patterns in the Package ......3 6........4.......................... 151 The Heat Resistance of Spores under Seals ........................4 6......................................................................................7 Determination of the Order of the Reaction ..............2 6........................9..................4 Sterilisation ...2 The Destruction of Bacillus Spores in Milk and Milk Concentrates ... 215 ............. 161 Hydroxymethylfurfural (HMF) ...7 6....................................... 174 Quantification of Pasteurisation Effects to obtain Objective Comparisons ...179 Heating Effects on Milk ...........................................4..................3 6........1 6................. 198 Heating Equipment....................................................................................................6 6............Reaction Kinetic Descriptions ............................ 209 6.......2 Influence of the Water Activity and the Environment ...... 147 The Effect of Changes in the Activity of Water on the Destruction of Microorganisms ... 6.....2.....................................................147 6............................2........................2.................5............................................................8....... 176 Changes in Milk and Cream Produced by Heating and Storage ..........................5...1....2 6.................................201 Heaters ..................8..................................4 6...8...3 6........ 169 6...................................1 6..............1 6.............X 6........3 6.......6.....2.......9 6.....................................4......3 6...............................1 6............................ 164 Effect of the Protein Concentration and of the Casein to Whey Protein Ratio on the Denaturation of Whey Proteins .......Batch Autoclaves .................................................................................. 214 Continuously Operating Sterilisers .170 Effect of Heating and Cooling on Concentration Change ....................5 Chemical Changes .....................................Areas of Application ..................................3 6. 211 Pressure Patterns in the Package ................6......................3 6................................... 155 6..........................................................................5......................2 6...............9....4...... 6....................................................................10... 145 Factors Affecting the Heat Inactivation of Microorganisms .......9..............................5............................. 207 UHT Method ........................................................................188 Interactions and Their Consequences........... 149 6.............. 189 Gels and Aggregates of Whey Proteins Produced by Heat ......... 195 The Effect of Lactose on Gel Formation ....5...................................... 204 UHT Method ....................5.........................9............................7.....8..............................................3.....................10..........................................7............................................... 149 The Effect of the Adsorption of Spores on Various Materials and of the Relative Humidity on Their Heat Resistance ..... 152 The Effect of Oils on the Heat Resistance of Spores .. 174 Standardisation of Heat Treatment Effects for given Limits ......................................4 Impact of Heating and Cooling on Heat Treatment ...................................................................1 6.....................4...... 6....................10....................1 6..2 6................... 6..........2.............Thermal Death Values ......................................................... 172 Establishment of an UHT Working Range . 212 Equipment for Sterilising Goods in the Package ............. 170 Death Time Lines ..................6...................... 156 The Loss of Thiamine .......................................6 6......... 6.............................................10.............................................................................................Direct Heating with Steam ...................... 168 Effect of the Casein/Whey Protein Ratio ...... 183 Heating and Environmental Interactions between Milk Proteins and Fat Globules ............. 160 Colour Changes ...........1 6.... 179 The Effect of Storage on Milk ......4 6..........................1 6.211 6............................................................................................................... 168 6...................5......................10 Sterilisation in the Package .........4........7..................................................3..................... 6................. 158 Losses of Lysine .............. 162 Whey Protein Denaturation ................................5.... 191 Effect of the Casein/Whey Protein Ratio and the Calcium Concentration on Structural Changes in Milk Protein Solutions .5 6...........................................2............................8.................156 6...5........................................6...........................Indirect Heating ...........................................7...............Water Treatment for the Production of Steam .2 Effect of the Whey Protein Concentration ..................6. Summary of Important Findings .................................... Design and Mode of Operation .............................. 201 Arrangement of Pasteurisation Plants ......... 182 The Effects of Heating and Storage on Cream .............................................................................................................................4 6...........................................7.........5.................. .............. 217 7....4 10 Sorption Isotherms ...........................2 7................................................................................................1 9...........................................................2 9...........................................................................................2 9.......3..................258 Establishment of Sorption Isotherms .Adsorption ...................Changes in the Condition of Moist Air..........3.....5 7.1 8.1 9......................................4 8........2 7............................................................ 224 Boiling Point .....5 Humidity ..............................265 10..................247 Heating of Humid Air .....................1 7..................................................... 232 Mechanical Vapour-Recompression ...............245 8....................4........217 Types of Evaporators ............................................................................................. 263 Chemical Changes .......253 9 Dry Products .................2 7...................................4 8.........255 Hygroscopic Properties of Dry Products...........................................1 8............................2 Water Binding Processes and the Lowering of Vapour Pressure ..................Dew Point .4...................................262 Growth of Microorganisms and aW-Values of Foods ........................................3 9..........1 8.1 7.......3 8...............2.......................................................................5 Air Conditioning at Varying External Air Conditions ......................2 9............... 262 Enzymatic Activity ............Sorption Properties ................................265 ...................... 231 Thermal Vapour-Recompression .....218 Heat Transfer and Boiling Point .....................................256 9....... 265 10.......................................................................... 252 8......................................................Drying processes and plants ........Keeping Quality ............................................3 7..4...........................................3...................Instantising ................................ 263 Drying ........1 9...............................3 8................................................................................ 258 Sorption Isotherms of Various Dry Products ...........243 8 Climate .......2 8..................................... 229 Evaporating Plants...............4..................................................................................................................... 235 Vapour Condensation and Vacuum Generation ............................................................................................................................ 245 The Enthalpy of Air ........................245 Characterisation of the Atmospheric Conditions .246 Changes in Condition ...................................2 8.............................3.... 255 9............. 257 Enthalpy of Binding .....4..........................................................................4.. 257 Desorption ..... Vapour Recompression and Energy Consumption ........ 263 Physical Changes .................... 260 Sensitivity to Moisture in the Region of Hygroscopicity ......................................................................2...........4........4................................... 245 8..................................... 247 Cooling of Moist Air and Dehumidifying of Air ............. 258 Sorption Isotherms ..239 Pre...................................................................... 246 Enthalpy/Humidity Diagram of Air ....................................4 9.. 247 Mixing of Two Volumes of Air .................2....230 Single and Multiple Effect Plants ....................... 250 Humidifying of Air .XI 7 Evaporation ...................................................................................and Post-Treatments in Milk Evaporation ...........2 Physical Basis of Drying .............................6 7. 251 Changes in Atmospheric Conditions at a Moist Surface ..........Hysteresis ...................................................2.................................................................4...........1 Application in the Dairy Industry .................237 Influence of Fouling upon Heat Transfer in Evaporating Plants......3 9..............2 Atmospheric Conditions in Dairy Processing .......................................................1 7................................................................................7 Overall Heat Transfer ..........................................................................Wet Bulb Temperature ..........4...3 Purpose and Practical Applications .........4........1 9............................................................4 7..4...........................................................3 9...2.......224 7.................................................................................................... ................................................................3..............299 10...............1 Milk and Dairy Products .........................Power Requirements ........................................4 10............................................307 11.............. 301 11 Cooling – Freezing .................................... 265 10.....3........................................................ 306 11.... 271 Air Flow .............310 Freeze Concentration ................................. 287 10...................................3.................3.................................................4.................4 Agglomeration .............................312 Freezing Time Calculations .4........................4............. 269 10...... 309 Reverse Osmosis and Ultrafiltration ..............4.. 302 11............................................2.................................. 290 10...................................................................2 10.....XII 10..................................Extraction .............................................................1........ 289 10.3........................................3.........................................................................................2...................................................................................... 302 11...................................................................................................................................2 11................................3............ 308 Processing Conditions ......................... 291 Drying Times and Means of Shortening it .............................................................................................................................................................................................................................................................2..........Danger of Fire and Explosion .........................................2 Effect on Individual Constituents ........................................................................................................2 Spray Drying .....................................3.....................3...........................2......3..............1 10..............................2 Fruits and Vegetables ....... 305 11.........................................................................................320 12 Distillation ..................................... 310 11.....Instantising .................1 Reconstitution Properties ........... 298 10.................2..............1 Cool Storage for Quality Preservation of Foods .........................................................................................................................................................1..................... 307 Composition of Milk ...............................4 Fluidised Bed Drying .....297 10......2............1 10.............................................................................................................3.......................2 Types of Fluidised Bed Drier ........................................2..................................4 Nature and Purpose of Freeze Drying .....5....................................................... 294 10.......................5 Milk Production .............. 324 ................................................................3.......................................................3 Roller Drying ................. 277 Spray Drying of Milk Products ....5 11.......... 287 10.......................5.....Freeze Concentration ........... 290 Heat and Mass Transfer ..................1 Radiation and Dielectric Drying .................2 The Drying Process ......... 285 Drying Characteristics ......................1.......................................................................3 Density of the Dry Product ....7 Freezing of Foods..........................................................................3.............................. 269 Design of a Spray Drier ................................................6 Construction of a Spray Drying Plant .4 Principle and Operating Characteristics ..............3....... 289 10...3............................................................................................................................1 Problems of Reconstitution .......3 10.3.......................................2 Parameters Influencing the Freezing Point of Milk . 277 Atomising .........................5.................Reduction of Loss of Fines ......................................................................6 11..................................... 300 10...................................1 10...........................................2 Methods of Agglomeration .....................................302 11.......................3................................5 10..........3.318 Freeze-Induced Changes to Foodstuffs ............ 269 10...............................2.............................................................................................................................................................5.................................High Pressure Extraction ....................4 11.....5 The Effect of Drying on Products ............................................................ 286 Special Roller Drying Procedures ...................3.................3.................................. 274 Discharge of the Dried Product ...2.................1 Evaporation and Vaporisation ........................................................................................................................................3..............................3.......5 Freeze Drying ..................5.........................................2 10......... 300 10..............5. 266 10................2 10......4 11............................................2.....4....................................3 Drying Methods .................315 Methods for Cooling and Freezing ........3 Controlled Atmosphere Storage .....3...................1 11.....................................................Energy Saving ..................................................... 307 Water ............2..................................................1 Principles of the Fluidised Bed Method ........ 297 10............................................2.........................................................................3 11........................2.........................3...3 Drying and Cooling Times in a Fluidised Bed ...........3 10..........................................5.........3. 293 Method of Operation and Design of Driers ........................................................................................ 286 10........................3 10................................... 280 10................................ 283 Types of Roller Drier ............3.............................. 283 10..........................3 11.....269 10.............................................. ........................................................................................................................................... 364 14....3 Heating by Means of Microwaves ....................................2.......................... 365 Vapour and Gas Permeability ... 352 13.............................2 14...............................................2 The Effect of High Hydrostatic Pressures on Melting Points and Changes in Temperature and Volume .................................... 327 Column with Concentrating Tower...................1 12..................4 Triangular Diagram and Areas of Application ...............................................................Application ..2......2............ 330 Countercurrent Extraction .....................1 14.......................1 Minimum Demands on Packaging Materials ... 327 Column with Stripping Section and Concentration Towers .....................1.......................................1..............................1...................................................................................................................................................4 12..................................................2 14..........................................2............... 364 Packaging of Concentrated Milk Products ...................5 Packaging of Milk and Cultured Milk Products ............................................ Rectification ...................................................................3 14..................................................1.................. Stripping Tower and Side Outlet ....3 14................................................................................... 327 Mixtures with Special Properties ...................................................................................................................... 338 13.1 14....................................................................................3 High Pressure Extraction ...................................................1.................4 Techniques of High Pressure Treatment .......................................................1.................. 344 The Process of Resistive Heating ................................ 364 Packaging of Cheese .... 365 14...... 354 13.....2...........XIII 12.................................................2 Packaging Materials ..........................................2.......................2 12.................... 330 The Influence of Diffusion on Extraction ...............................1.............2......................................................4 Principles ...............1............................................. 338 13............................344 13........2 13.................4..............................1.....333 13 Alternative Methods of Preservation..........325 12...............................................2 12....2........................................3 12...........4...... 368 Packaging Materials for Cheese ....................................... Extraction ........................................ 327 Exchange Processes in the Separating Tower and Example of a Plant .........2................................3 12............................1 Effects on Food .............................................................................. 328 12...........4 High Pressure Treatment ...................Filling .............2.... 326 Column with Stripping Section ..................1......2.................................330 12.................................. 345 The Electrical Conductivity of Food ................................... 364 Packaging of Butter .............................2 The Ohmic (or Resistive) Heating Process .......... 325 The Equilibrium Diagram ......................1 13.................. 346 Resistive Heating of Food .......................352 13......................... 369 Packaging Materials for Butter ..... 339 13............ 333 The Influence of Mass Transfer during Extraction .......1 Treatment by Irradiation ........................................3 13...............2..........................337 13...............................4...............................................................Properties ......2.........7 12..... 355 13............. 370 .........................8 Behaviour of Mixtures ............................1 12...... 337 13.....................................................350 13............................1. 333 12.......1..............1..........................4 14...........................................1...............................................................2...............Gas Permeability .5 Properties of Packaging Materials ...................................................................................................3 High Pressure Inactivation ................................................6 12...................1 Types of Radiation ............... 325 Column with a Concentrating Tower ........5 12.........................2.....................................................365 14......2 Effects of Radiation ...1 UV Radiation .......................... 367 Packaging Materials for Milk and Fermented Milk Products ......................364 14......................................................................................................................................................................................................................2............1................................................. 362 14 Packaging ........4.4 14................................................................. 364 Packaging of Dried Milk Products ..............1.....................1 Distillation.................................. 348 13............................................... 337 13.......................................1......2 Electron and Gamma Rays .............. ..........2 15................................................6.........................2......................................................................................... 409 Operation of Churning ......................................... 436 Salting of Cheese ...................................................427 16.....................................5 Disinfection of Packaging Material and the Danger of Possible Recontamination ...........................2..................6 16....... 374 Packaging in Cups .................4........................................................................6 14.................................2.................................................................................................................................................... 373 14........3 15.................................................................................................................................................................. 376 Packaging in Glass or Plastics Bottles .................................................2 Technology of Cheesemaking ... 425 16. 389 15.............XIV 14........................................420 15...................1 Cream Technology ..........2..........................................2..................1 Production of Clarified Butter .......................4.......................... 379 Packaging in Cans and Tubes ................................................ 406 15.....................................................................................................3.........2..7 Packaging Material for Dried Milk Products ...........................5 16.............. 386 15...........................................3.6 Butter Technology .3 14............. 373 Welding in Packaging Films ........................4..............................................................................................10 Selection of Milk ............4 14.......................2 16.........................4......................... 443 .............. 408 Processing of Cream for Butter Making ........385 15................... 416 15.........425 16........................................ 420 16 Cheese Manufacture – Dairy Protein Products...........7..............402 15................ 385 15...............................................2............4 Foam Formation and Stabilisation ..........................................................................5 Stability of Coffee Cream ................... 370 14.3 Whippability of Cream .............. 435 Turning and Pressing................................393 15........................................1 Free-Fat Content as Measure of Destabilisation ........ 436 Ripening and Final Treatment ...8 16.............................2.........................4 Process Flow Diagram ........... 428 Standardisation of the Fat Content ................5...........................................................................4 16....................................................................... 381 14.......................................................................................................1 16.......................6..........................................................2......................................................... 403 15........7 16.......7 Overwrapping with Packaging Film or Foil ..........2................6...............371 14...........2 Metering and Filling of Dry Product Capable of Flow ........................................5..................6................... 430 The Processing of the Curd ...........3 Filling and Metering ..4.................................................... 370 14.............................................4.....................................408 15......................2 Minimising Flocculation through Cream Technology ..........4 Packaging Methods ..................................................................................................................................3 16....................................................................... 427 Heat Treatment of Milk .............................................. 430 Renneting and Coagulation of Milk .......................... 429 Addition of Starter Culture and Ripening of Milk ...2......................................................................... 379 Packaging in Folding Boxes..........................2 14..................9 16................................. 413 Process of Butter Making ....................373 14...................................................................................................386 15........................2 Fat Composition and Crystallinity as Measures of Mechanical Stability ........................................................................1 15.2......................................... 371 14.....397 15.....1 14..................................................1 Metering and Filling of Liquids and Pastes ..............2.................. Bags and Sacks ..........1 Factors Influencing the Acid Content of Coffee .......................................4...................2..........5 14... 376 Packaging in Cartons and Pouches ..... 434 Filling and Shaping the Curd .......................................1 Classification of Cheeses .......382 15 Technology of Cream and Butter .......................7 Clarified Butter and Other Special Products ..................................2 Factors in Destabilisation of Fat-Globule Membrane ..........6 Packaging Materials for Concentrated Milk Products .......... ........... 477 The Effect of the Composition of the Product and its Pretreatment on Gel Properties ...3 17........7 16............................1 17.................444 16... 480 Acidification and Gel Formation by Glucono-d-lactone ........... 447 Processed Cheese .............................2 17............4 Continuous Production of Cheese Curd .459 17.....................2 Factors Affecting the Stability and Organoleptic Properties of Set Yoghurt ........ 493 ...................................................................................................................................................5 Hydrocolloids..............................................................3...........................2 The Use of Hydrocolloids in the Manufacture of Dairy Products ........................... 493 18.....................................................................................................................................................................................................2 Caseinates ....................................................... 468 17.....4.3...............5 17.....5 New Technologies – Inclusion of Whey-Protein Microparticulates ................................. 485 17.....1... 485 17.4........490 18 Manufacture of Ice Cream ........4.................... 478 Directly Acidified Milk Products and the Effect of Stress ...1 17.........1 Casein Co-Precipitates ................................... 456 17 Technology of Cultured Milk Products – Structure of Gels – Direct Acidification – Special Milk Products and Use of Hydrocolloids . 452 16........................................ Feta ................... 488 17.............................. Incubation and some Cultured Milk Products .......................... 466 Additives ..................................................................1 16..........5.................................................................................................................................. 475 Direct Acidification and Gel Firmness ................3....XV 16..................1.......................................................................................................4 16................4 17.... 483 Production of Yoghurt Aroma Concentrates for Directly Acidified Milk Products .....6 Colour Changes in Fruit-containing Cultured Milk Products .........Ice Crystals ... Texture ............................6 Production of Casein and other Milk-Protein Products ..................4...................................................................... 462 Cooling of the Incubated Milk .........................................................................................................4 17...........1 Process-Required Changes ...............................................................................3 17.................................... their Mode of Action and their Use in the Manufacture of Dairy Products ........3 Extrusion Technique ...5....................6................................................ 444 Schichtkäse (Layered Cheese) ........................... 459 Increasing the Solids Content ....4 Gel Structures in Yoghurts Produced by Direct Acidification ...........................................5...................................... 452 16.......3......6 17....5........................4. 450 16............. 476 The Influence of the Gelling Conditions on the Structure of Gels ........................... 446 Pickled Cheese......5 Raw Milk Supply and Adjustment of the Fat Content ...................................................7 Direct Acidification and the Coagulation of Casein ....................... 459 17.485 17.......... 445 Mascarpone ............................................................................................................................................................Quark (Curd Cheese) ......................... 455 16............3 16..... 447 Cooked cheese (Kochkäse) ...453 16.............................................5..450 16......................................................... 453 16......................493 18.....3.............2 16.....................1 Types of Ice Cream Ingredients.........1..................................................473 17..1.....1...............449 16....1 The Technology of the Production of Cultured Milk Products ...........................................5 16..3 Increasing the Shelf Life .3.........6............................. 445 Cottage Cheese .....................3...........1 Types and Ingredients ....8 Fresh Cheeses ......468 17..........3..................2 Ripening of Cheese containing Whey-Protein Microparticulates ................................................2 17.................................................474 17...4......4.................. 447 16................ 446 Cheeses made from Milk Coagulated byAcid ..................3 Special Cheese Varieties ..... 461 The Addition of Culture......6 16........................1 Hydrocolloids – Mode of Action ..............................................1.........................6..................3 Yield and the Attributes of Final Product ................................................................... ........................3 Final Freezing and Hardening ........................2 Fermentation of Whey to Lactic Acid (Lactate) ..............................3................... 511 The Effect of the Distribution of the Enzyme in the Substrate .....................7 Anaerobic Whey Processing ............................................................2 The Technological Functions of the Most Important Ingredients of Ice Cream ...... 495 18......7......................................537 19.........................................................................................Surface Freezer .................................................................................................................. 533 19.............. 500 18....1....5 Bioreactors ... 516 19....................3..............2 The Technology of Ice Cream Manufacture ...1 Preparation of the Ice Cream Mix .... 533 19............501 18......533 19.....................................................................................................1......................3.................518 19......................511 19....................................4 Melting Characteristics of the Ice Cream ..... Mass Exchange .........1.........................................4 19..Supply of Oxygen ..................................................541 19.... 523 19....... 493 18................................................2.........................................10 Heat-Acid Precipitation of Whey Proteins ..4.........3 19............. 499 18.........................................12 Brown Whey Cheese............. Rate of Products Formation ............497 18...................3... 497 18............3 Aerobic Bioprocesses ........................ 511 19......................................................................................... 514 Inhibition of Enzyme Reactions ......... 508 The Transition and Stationary Phase ...............................................................8 Aerobic Whey Processing ....................2........2 Areas of Application of Starter Cultures .................506 19............................................... 520 Heat Production during Fermentation .........527 19....2 19............XVI 18...........................................................1 19.3 The Structure of Ice Cream ....501 19 Biotechnology and Whey Processing .......................6 Purpose and Problems of Whey Processing ....1 19......................................................... 521 19.................................2.1 Composition of the Substrate .................................................................... 506 19..........3................................................................3...........................1.....................................530 19......2 19.......................................................1............................................... 515 Immobilised Enzymes............1......................................1 Types of Cultures..............................................................................................3 Discontinuous Growth (Batch Process) ..............3.....................3.......1...................................................................................................................541 19........ 506 19.................................................... 507 19...............................................2................................................................3 19...2 19.................1.......................................................................................4................................ 519 The Respiratory Quotient ... 508 The Formation of Products.......4 Starter Cultures and Enzymes ....2.........................................7...................................................................1 Fermentation to Methane ............ 495 18..........2 The Rate of Growth of Microorganisms and the Yield of Product .......................................................................1.....................1...................... Preparation and Problems with Phages ...........................4 Formation and Growth of Ice Crystals in Ice Cream ............................7..................................................3 Heat Transfer and Residence Time in Scraped.521 19...................2............................2 Partial Freezing in the Freezer ...................1 19. 514 The Effect of the pH Value and the Temperature on the Rate of Reaction .......4 19.....................4.............................................. 526 19....2............................................ 522 19............. 509 The Stationary Phase . 518 The Rate of Oxygen Transfer .............3.....................................Single Cell Protein Production Yeast Production ...................543 .......................................................................................4 Continuous Cell Growth in Stirred Reactors ...................1......................2 Enzyme Kinetics ............................................ 511 19...............................................................................3 Alcoholic Fermentation ..................3.........................................................................................4 The Solubility of Oxygen ............... 19..1 The Kinetics of Cell Growth ...............1........................... 535 19........................................................11 Production of Lactose .................................5 The Lag Phase ................ 507 19............... 508 The Exponential Phase ..................................................2........5 The Michaelis-Menten Kinetics and Fundamental Concepts ...3 Area of Application of Enzymes ................. ..........3...................3 Agitation and Mixing .....................3 Special Cleaning Procedures ......................................................................................................................................................................................1 Basic Principles in Cleaning ......... 576 21..................... 570 21....................3.......................................588 21......................................................................................................... 555 Hydrodynamics....2.544 20...4. 552 20.......................................................1....2.................Influence of Denaturation Degree .......2 Fouling of Salts in Heat Exchangers .............1 21.............................. and Heat Transfer .......... 588 21.....................................................5 Alkaline Cleaning Agents ............... 588 21...................4............................................1 Depositions in Milk Processing ...........3................................1..............1 20...4 21............................................. 599 21... 563 21..............................................3.................................................................................... 596 Cleaning of Evaporators ...........................................................................3.................................................... 575 Operation Time Effects ............................3...............................4 21...............Chemical Reaction .............3.........3 21.........................................................................................1 Positive Displacement Pumps ..1.................. 576 21.....................................1 Mass Transport Processes ................2 20..............................................................................................................2..........................1............................ 547 20................................................................... 553 Characterisation of Mixing Efficiency ......................................1 21............Construction Materials ......2 Salts Fouling .............583 21.............2............................................Crystallisation ...............................................................3..4 Fouling Due to Whey Concentrates ...................................................... 592 Cleaning of Glass Bottles ............561 21 Fouling ................. 568 21.........................4.......................................3 Corrosion .........................3 21.................................................... 571 Reaction Kinetics ............. 565 21........2 Types of Tanks ................................................................................................3.....................5............................563 21................................................... 559 20............................................................................................................................ 545 20.......2 21.............3 20........................................................ and Containers ....................................................1 Tank Design ......1....... 566 21............................................2...................................3...................3 21......................2 Cleaning and Sanitising Agents .........................................................................4............1.. 578 21...............................3........599 21........................... 550 20.................................. 544 20..........3................................................4 Cleaning Procedures ........................................................2 Selection of Cleaning Procedure .....................3 Protein Fouling ....1......................................................... 583 21................................................2..........................1 Fouling Resistance ....2 Centrifugal Pumps ............................................................................Sanitising .......2........................4.................. 581 21........... 600 ................................................................. 569 21.............................2..............1 21..............................................................6 Cleaning of Cans...............2............................................................................2.........................................2 21............................................................... 554 Design of Agitation Devices .2........... 544 20.............3........................2................1..............................................................553 20.............1.......................................Cleaning .............1.............3............................................... 582 Hot Water and Steam .......... 590 21.......................................2...........2.....................................................578 21.................2.................................. 598 Cleaning of Membrane Plants ................................................................................................ 581 Acid Cleaning Agents ....................4......5..............................................................2...................1........................................................................ 557 Mixing in the Technology of Milk Replacers ............Rinsing and Associate Processes at the Interface .........................1 Tanks in the Dairy Industry .....1 Salts Fouling in Falling Film Evaporators .......................................................................................4............... 582 Sterilising Agents ..............................Sanitising ....................... Power Input..............5 21...4 20.............................................................................................................4 Grinding ............................4...............................................................................3 Cavitation . 598 21.2 Displacement of Highly Viscous Products ..547 20.......................................... Tanks.......2 21..................................................................2 Pumps in Dairy Industry ..........Preventive Measures ................ 574 pH-Induced Effects .............4 Proteins Fouling at Heated Surfaces .1 Fouling ..............4................................................................. 596 Cleaning of Dryers ....3...............................XVII 20 Tanks – Pumps – Stirrers – Mixers – Grinders ..................................5 Product Displacement ..............1..................................2.................................................................................................2 Cleaning ............................................. 581 Surface Active Agents .................................................5 Basic Applications ......................... 590 Cleaning of Heat Exchangers ............. .........................................................3 23.............................................................................................................................................................3................................... 650 Evacuation time .. 614 22................ thermal conductivity enthalpy.........1 International unit system (SI-System................6 23............... 639 Viscosity and density of milk products .......................................................1 22....................................... 637 Constituents and composition of milk ..........5....................3 Rinsing of Tubular Surfaces .XVIII 21.....................................3 22... 621 Activated-Sludge Stabilisation Techniques ..................................... 652 23.....................5 Percolating Filters .............2 Effluent Pollution ...... vapour pressure curve of solvents and cooling agents.................................2 22.............................................5......... solubility curves of some salts ....................615 22....................................................... Surface tension and physiologic calorific values of milk............................... 641 Specific heat capacity............................................. cream and food constituents ........................................................................609 22 Water and Effluent Treatment .................10 23......................................................................... 651 Relative atomic mass of some elements and composition of the air .......................................................................3.........................11 23............................... 645 Determination of total mass........................................................................12 23..........618 22.............................8 23............................. 629 Water vapour table and enthalpy/entropy-diagram ........................................... 623 Anaerobic Purification ................. Système International d’Unités) conversion tables – important physical constants ............3........................ 604 21........................................................ 649 Vapour-liquid equilibrium.............. 625 23 Physical Data – Conversion Factors ................................. 633 Specific heat capacity................ 622 Modern Activated-Sludge Processes . 653 Index .................. 629 23.............................................................................................................................properties ................................1 Water Quality .................................................................................................................6 Adsorption at Solid Surfaces .................................... total amount of substance and molar fraction of product compositions .........................3 Methods of Treatment ..................................... 668 ............................ 619 Activated-Sludge Plant .614 22...... 608 21.......................... mass fraction............................... density and thermal conductivity of solids and liquids .............................................................................................................................................7 23................................. 651 Conversion correlation for the water content ..2 23..................................................4 22............... 635 physical data for some liquids and gases at 1 bar – calorific value of some substances ...3.....................................4 Final Rinse Processes .............................4 23........................13 Bibliography ........... 649 Solubility of gases in liquids ........................5 23.....................................................9 23.......3.... KS KOW l.XIX Symbols and Dimensionless Numbers A AM B* BM C C C* D D D D D* E E Ea F F F-value F* G# G’ G’’ H h. kg/kg or kg/m3 mol/m3 m m2/s s s V/m J/mol N min or s J/mol Pa Pa J m J/mol kg m/s A/m2 s-1 m/s mol/m3 Pa sn m kg/kmol m2 kg/m3s kg/m3 N/m W J W - Cross sectional area. Monod constant Ostwald factor Length Relative molecular mass (weight) Number Surface Oxygen transfer rate Product concentration Linear contact pressure Power Pasteurisation effect Heat Heat flow Dimensionless parameter from reaction kinetics . H H# I J K K KL KM. L M N O OTR P P P P* Q  Q Q10 m2 s/m m/s %. surface Membrane constant Bacteriological effect Membrane constant Concentration Molar Concentration Chemical effect Deformation Diameter Diffusion coefficient Decimal reduction time Permeation coefficient Degree of cream separation Electric field intensity Activation energy Fat content Force Sterilisation value Degree in colour change Free activation enthalpy Storage modulus Loss modulus Enthalpy Height Enthalpy of activation Momentum Current density Proportional factor Rate constant Mass transfer coefficient Michaelis-Menten constant. d’ f f f g h h h h’ k k k* l m m  m m2/m3 m m/s2 Pa-1 s s J/kgK m m Hz m/s2 J/kg m W/m2K m/s s-1 W/mK m m kg kg/m2s kg/s Universal gas constant Constant radius Fouling factor Individual gas constant Substrate concentration Unit of Length Activation entropy Absolute temperature Circumference Overall heat transfer coefficient Velocity Volume Volume flow Volume of activation Work Moisture content on the basis of dry matter Cell density. death rate constant Thermal conductivity Absolute roughness Length Mass Rate of drying Mass flow .XX R R RA Ri S S S# T U U V V  V ∆V# W X X X X* J/molK m m2K/W J/kgK kg/m3 m J/mol. thickness Moisture content based on total mass (water and dry matter) Yield factor Centrifugal constant Specific area Water activity Length. cell concentration Distance. width Acceleration Conversion factor Coefficient of flow Mass conductivity Specific heat Diameter Dimensionless diameter Equivalent. height.K K m W/m2K m/s m3 m3/s ml/mol Nm kg/m3 m - Y Z a aw b b b b b/µ c d d* de. hydraulic diameter Fat content Friction coefficient Frequency Acceleration due to gravity Specific enthalpy Length. width Heat transfer coefficient Mass transfer coefficient Rate constant. volume fraction Emittance. latent heat of sublimation or fusion Specific entropy Unit of length Time Reflux ratio Specific volume Velocity Dimensionless velocity Concentration. charge Moisture content of air Coordinate of length Coordinate of length Respiration rate Number of discs Coordinate of length Increase in temperature necessary to obtain the same effect in 1/10 of the time Angle m2/s Thermal diffusivity ° K-1 s-1 m °C S/m m Content of ice Angle Expansion coefficient Shear rate Activity coefficient Distance. thickness Difference Porosity. °C α ° Flow behaviour index.XXI n - n n p q q r r rIndex s s t v v w w* x x x y y z z z-Wert mol s-1 Pa J/kg W/m2 J/kg m J/kg J/kgK m s m3/kg m/s m m s-1 m K. performance coefficient Exchanger efficiency Relative dielectric loss factor Resistance coefficient Degree of effectiveness Temperature Dimensionless temperature. wetted angle (°) Constriction value Electric conductivity Proportion of specific heats Mean free path α= k cpρ α* β βIndex γ γi δ ∆ ε ε εA ε ′′r ζ η ϑ θ κ κ κ = cp/cV Λ . order of reaction Number of moles Number of revolutions Pressure Specific heat Heat flow rate Latent heat of evaporation or fusion Radius Binding enthalpy. number. exponent. ρ.cp) Th = ∆p2 / ∆p1 We = (w2.ν2) Bi = (h.h’.d3) / ν2 = Re2 / Fr Gr = (d3. interfacial tension Tension of the material Thermal radiation constant Osmotic pressure Shear stress Relative humidity Angular ratio Fraction of a volume Angular velocity Heat penetration factor Archimedes number Biot number Damköhler number Fick number Fourier number Froude number Froude number Galilei number Grashof number Knudsen number Laplace number Lewis number Newton number Nusselt number Péclet number Prandtl number Rayleigh number Reynolds number Schmidt number Sherwood number Stanton number Thoma number Weber number Thiele-Modul .α) = Gr.XXII µ µ µ ν ν ξA ξ ξ ξm ρ σ σ σ Π τ ϕ φ φ ω (λcρ)0.β. friction coefficient Specific productivity Kinematic viscosity Fouling resistance Specific flow resistance Mol fraction Mean salt content of cheese Density Surface tension.5 Dimensionless Numbers Ar = (d3.g.5 Pa s s-1 s-1 m2/s m-1 m-2 kg/m3 N/m N/m2 W/m2K4 Pa N/m2 s-1 Jm-2K-1s-0. absolute viscosity Specific rate of growth Diffusion resistance factor.g.Pr Re = (w.t) / d2 Fr = w2 / (g.d) Fr = (n2.d) / kfluid Pe = (w.d5) Nu = (h.d) / g Ga = (g.X) /ksolid Da = vmax/(A. = τ.d.d) / D St = h / (w.d) / α ν/α Pr = Ra = (d3.d / (4 σ) φ = R vmax 3 KM ⋅ D Dynamic.d) / ν ν/D Sc = Sh = (h’.g.∆ρ) / (ρ.∆ϑ.ρ) / σ.βV) /ν2 Kn = ∆/d La = (∆p.n3.d) / σ Le = α/D Ne = P / (ρ.t) / X2 Fo = (α.Sb) Fi = (D.∆ϑ) / (ν. A separate chapter contemplates enthalpy moisture diagram for air and air conditioning due to its importance in food technology for ripening. Separation technology is discussed in two different sections. butter.e. A further mechanical process follows with emulsion technology using homogenisation. Therefore. and decontamination. since processes but even products change with time. whey. separation of microorganisms. ohmic and microwave heating as well as the ultra-high-pressure technology. which required reducing the representation to only essential parts. additional added section on alternative methods of preservations shows and discusses possibilities and limits of the application of radiation treatment. The effect of single-unit operations on a total process is demonstrated in 4 chapters with the manufacturing of special dairy products such as cream. The increase of knowledge in the different fields of science has developed significantly in the past years. The next chapter focuses on concentration by evaporation and vacuum evaporation including thermal and mechanical vapour compression. it is more useful to individually reflect more on unit operations than on the extensive and complex processes of food manufacturing. In addition this unit approach allows the analysis of the process steps separately for solving problems in practical operation. Special attention was put on drying. For a long time there was a gap between the basic sciences focusing on the substrate and the engineering sciences considering especially the technique and physical basics of food processing. processes with control and measuring equipment and new methods for the manufacture of foods. Emphasis is on reaction kinetics. In a further section the moisture sensitivity and sorption characteristics of dried food are discussed. fermented milk products and ice cream. demineralisation. Under this scope the book focuses on the basic principles and the unit operations and their impact on food. apparatus. This transition was accompanied with intensive research activities comprising the fields of chemistry.and thermodynamic issues are handled in ensuing sections. Gentle thermal preservation and concentration methods i. The knowledge of the laws of interactions of the specific fields shall finally result in new and better processes.XXIII Introduction In the last decades the development of food manufacturing and especially of the dairy industry was characterised by concentration and formation of large food producing enterprises. freezing and freeze concentration. in which the basics of biotechnological processes are presented in . Several chapters are devoted to thermal unit operations also including measures for energy saving. In parallel engineers designed machines. new qualitatively improved foods and economic production. The first one considers technologies using centrifugal forces as separator and its application but also cyclones for dust separation. cooling. Packaging technology is one important processing step in food manufacturing and aseptic packaging and sterilisation of the packaging material are appropiately discussed. water purification. This gap was filled with the development of a more technological orientated basic science and a process focused evolution of engineering sciences. roller. Whey serves as substrate for several biotechnological processes. hygiene. biology. The second one contemplates membrane separation and filtration used for protein recovery. concentration of solutions. physics. and food technology. Heat treatment processes as pasteurisation and sterilisation and their impact on food are considered first. lactose. are also presented extensively. The intention of the book is to join even more basic sciences and process engineering. fluidised bed and freeze-drying are presented as well as product instanisation by agglomeration. casein. cheese. The new. In the first two chapters some principles of fluid mechanics and of heat and mass transfer are summarised being essential for basic calculations in practical applications. In all chapters special focus was put on application for food and impact on the product. Special hydro. To achieve such a goal it would be wrong to separately consider food-technological processes of some special products. spray. This was the reason for establishing a chapter on bioprocess technologies. storage and drying. The chapter on cleaning and disinfections was strongly extended including the description of product layers. mixers and stirrers are important elements in a food processing plant and are concisely summed up in a separate chapter. Special focus was devoted to water treatment and biological methods with their recent process engineering developments. formation kinetics and their control by process technical methods. An extensive collection of physicochemical properties. With this content the book may not only serve as book for education and information but also used as handbook for direct application. .XXIV a general way using the example of various whey-processing methods. pumps. conversion tables and calculation correlations concludes the book. Holdings tanks. Hygiene and water quality is a prerequisite for food processing and is reflected in more detail. Reactors and applications are described beside the kinetics of bacterial growth and enzymes.