525Characterization of Palm Acid Oil Ainie Kuntom*, Wai-Lin Slew and Yew-Ai Tan Chemistry and Technology Division, Palm Oil Research Institute of Malaysia, Ministry of Primary Industry, Kuala Lumpur, Malaysia Palm acid oil (PAO) is a by-product obtained from the alkaline refining of palm oil. It is used for making laundry soaps and for producing calcium soaps for animal feed fo~ mulations. The properties and composition of PAO may differ according to variations in the palm oil feedstock and the alkaline refining process. Because information on the characteristics of PAO is limited, this investigation aims to establish the properties of this product. Quality and oxidative parameters of 27 samples of PAO were determined. The six parameters analyzed were moisture and free fatty acid content, peroxide value, iodine value, saponification value and unsaponifiable matter. Headspace-gas~clmP matographic (HSGC) analysis and gas-chromatographic analysis of the extract from Likens-Nickerson steam distillation of the samples were also carried out. Mean moisture content was 0.98%, free fatty acids 62.6% (pahnitic acid), peroxide value 4.1 meq/kg, iodine value 50.2, saponification value 186 and unsaponifiable matter 0.53. HSGC profiles of a few samples showed the presence of one to three peaks, while the steam distillation extract showed the presence of aldehydes, ketones, furans and acids. KEY WORDS: Acids, aldehydes, FFA, furans, IV, ketones, palm acid oil, PV, saponification value, unsaponifiable matter and headspaceGC volatiles. Crude Palm Oil I Alkaline Neutralization I >Soap stock Neutralized Palm Oil Acidification with Sulfuric Acid Earth Bleaching Acid Oil Neutralized, Bleached Palm Oil Crude palm oil obtained from the mesocarp of the palm fruit must be processed before it is used in edible applications. Processing involves refining, bleaching and deodorizing the oil. There are two types of refining, namely physical and alkaline/chemical refining. Physical refining involves steam distillation under vacuum (2-6 mm Hg) at 240-260~ Alkaline refining (Fig. 1) involves neutralization with alkali such as caustic soda One of the by-products of alkaline refining is soapstock, which contains some emulsified neutral oil. The soapstock is easily separated from the neutralized oil by density-difference or centrifugal separation. Acidification of the soapstock gives the acid oil. The main components of palm acid oil (PAO) are free fatty acids (FFAs), neutral oil and moisture PAO is exported from Malaysia to Europa Japan, India and other countries. For the year 1991, PAO export from Malaysia totalled 37,154 million tons. In Africa, India and some other countries, it is used for making laundry soaps. It also is used to produce calcium soaps for animal feed fol~ mulations. At the moment, the Malaysian Custom Department defines PAO as oil with high FFAs, obtained from the soapstock of alkaline refining through acidolysis, usually with sulfuric acid. This definition is not specific enough, and therefore, there is a need to draw up certain specifications for a clear definition of PAO. With this in mind, PAO was subjected to a few quality and oxidative analyses besides determination of volatiles. Analysis of volatiles is widely used to characterize food (1-3), oils (4-11), meat (12-14), fruits (15-19), milk products (20), leaves (21-23), flowers (24) and drinks (25). One of the methods used to analyze volatiles is the headspace gas*To whom correspondence should be addressed. I Deodorization I NBD Palm Oil FIG. 1. Flow diagram of alkaline-refiningprocess of crude palm oil. NBD Palm Oil, neutralized, bleached, deodorized palm oil. l chromatographic (HSGC) method. Another method is the Likens-Nickerson simultaneous distillation-extraction (SDE) gas-chromatographic method. In this study, both methods were used to analyze PAO volatiles qualitatively to assess if this parameter could aid characterization of this oil. EXPERIMENTAL PROCEDURES Materials. PAO samples were derived from alkali-refining (Alfa Laval, Westfalia, Germany) of oil palm fruits, Elaeis guineensis, harvested in the year 1990. The samples were collected from refineries located in the North, West, Central and South of Peninsula Malaysia. In Malaysia, only eight refineries produced neutralized, bleached, deodorized palm oil by this process. Quality and oxidative parameter measurements. For moisture content, loss of moisture was measured according to a PORIM Test Method 1988, p 5.2 (26). For FFA, the acid value of the samples was determined according to the PORIM Test Method 1988, p 2.5 (26). Peroxide value (PV) determination was in accordance to the PORIM Test Method 1988, p 2.3 (26}. For IV, PORIM Test Method Copyright 9 1994 by AOCS Press JAOCS, Vol. 71, no. 5 (May 1994) SDE analysis. CA) simultaneous distillation-extraction apparatus was used to extract the volatiles.2 186 0. CA) with a 1-mL sampling loop installed in this model. Three unique ketone compounds.16% with a mean value of 0. 3.6 0. On JAOCS. A017. The extraction was carried out according to the instructions enclosed by the manufacturer. A05 and A029.6 4. A PAO sample (5 g) was weighed into a 12-mL vial and then tightly sealed.7. 0. PA). the headspace chromatographic profile can be used as an indicator of the quality of PAO. Helium carrier gas head pressure was 13 psi and the injector temperature was 250~ Initial temperature was 40~ (5 min). IV. Two samples.42 Range 54. had high PVs of 10. make-up gas 27 mL/min. The values ranged between 0. which had low values of 38. Three PAO samples. programmed to 100~ (5 min) at 8~ and then at 16~ to the final temperature of 220~ The MSD was a quadrupole" with electron impact at a voltage of 70 eV. PV. Table 1 lists the average moisture content of the 27 samples of PAO studied. Moisture content. injector temperature 250~ capillary column Supelco SPB-5 (cross-linked SE 54.53 11. had slightly higher PVs of 6. Saponification value. no. Likens-Nickerson simultaneous distillation-extraction.1 (26). and 0.6%.6. The vial was placed in a Hewlett-Packard Model 19395A headspace sampler (Palo Alto. The mean value was 0.98%. For unsaponifiable matter. Volatiles consisted of alkanals.6-dimethyl-2. The mean value was 50. On the other hand.33 pm film thickness. Headspace analysis. alkanones. The six parameters. PAO samples were steam-distilled. the PV of acid oil was less than 5.526 A. Samples with profile type (b) with only a few minor peaks can be projected as good-quality PAO.7. samples with profiles of type (a) and (c) are likely to be samples that have deteriorated slightly. The mean FFA of 27 samples is given in Table 1. FFA. PA) of 0. The mean saponification value of the PAOs studied was 186 and the range was 172-197 (Table 1). Figure 3 shows the gas chromatogram of the SDE profile of PAO.2 meq/kg.1 meq/kg with a range of 1. indicating the presence of a reasonable amount of unsaturated fatty acids.3 ~L of the sample was injected into the gas chromatograph. Table 1 lists the PVs for the PAO samples. Table 2 lists the compounds identified in the distillate. The PAO sample (50 g) was placed in a three-necked round-bottomed flask and 150 mL distilled water was added.9-20. pressurization time 10 s and venting time 10 s. In this experiment.2 (26) was used. most probably resulted from the degradation of carotenoids. The range of IVs of the PAO samples studies is shown in Table 1.. the FFA value of PAO was above 50% with the exception of two samples. p. A019 and A029. Fourteen percent of the samples had profile type (a).7 (26) was used.53 Standard deviation 0.1 50.d. respectively. The mean value was 4.67. 3. The saponification value of the samples was measured by P O R I M Test Method 1988. initial temperature 40~ rate of increase of temperature 10~ final temperature 200 oC. These three profile types suggest t h a t the quality of PAO varies slightly. alkadienals and hydrocarbons (28-34). had a slightly higher unsaponifiable matter of more than 1. The steam distillation-extraction was carried out for 6 h. p. carrier gas helium flow rate 8 mL/min. The vial containing PAO was thermostated in a carousel mounted in a silicone oil b a t h at 80~ and equilibrated for 30 min. septum purge 6 mL/min. 5 (May 1994) the average.6. and 30 m length.10-undecadione" mionone (29) and geranyl acetone.2 mm i. saponification value and unsaponifiable m a t t e r can be useful as specifications of PAO.01 79. p 2. FFA. and the volatiles were extracted with pentan~ The pentane was then evaporated under a stream of nitrogen until the total volume was 2.9 and 5. alkenals. and the value was 62. 71. 82% profile type (b) and 4% profile t y p e (c). CA) and a Hewlett-Packard HP-5 column (Avondale.5 3.2%. IV. HSGC analysis (27).56 3.08 18.00 (Table 1).25 RESULTS AND DISCUSSION The results of the six-parameter analysis of 27 samples of PAO are discussed below.6 and 20. The range was 27.0 mL. 6. and 30 mL pentane in a pear-shaped flask was placed in the warm (60~ waterbath. split flow ratio 1:4. moisture content. Supelc~ Bellefonte.15-2. Unsaponifiable matter. respectively. The potential use of these ketone compounds as a characterization tool seems . The PAO volatiles were collected in the sampling loop and injected into a Hewlett-Packard Model 5890 gas chromatograph via the 45~ transfer line.42 and the values of 27 samples ranged between 0. alkylfurans. PV. KUNTOM ET AL. P O R I M Test Method 1988.3. A027 and A028. carboxylic acids.49 92.1 and 27. A J&W Scientific (Folsom. This is supported by the low PV of less than five for these samples.68 10. The IVs ranged between 39.8 5. 25 m length and 0. The oil/water mixture was heated to 120~ in the oil bath. hydrogen 18 psi. On average. 1988. namely.98 62. respectively. while another two samples.3 5.d. the headspace procedure used was the static method. The chromatographic headspace profiles of 27 samples of PAO showed three profile types as illustrated in Figure 2. Vol. TABLE 1 Quality and Oxidative Parameters of Palm Acid Oil Parameter Moisture content (%) Free fatty acid (%) Peroxide value (meq/kg) Iodine value Saponification value Unsaponifiable matter Mean value of 27 samples 0. A020 and A025. air 60 psi. The headspace sampling operation was carried out under the following conditions: valve temperature and loop temperature 45 ~ vial pressurization 28 bar. detector temperature 250 oC.2-57. On this basis.6-81. depending most probably upon processing conditions.32 mm i.04-1. Gas chromatographic separation of the headspace gas sample was conducted under the following conditions: helium carrier gas head pressure of 15 psi. The volatiles were analyzed on a Hewlett-Packard gas chromatograph 5890 series II with a mass selective detector (MSD) 5971A (Palo Alto. 5 (May 1994) . I s A i 2o .n o n a n a l . . In summary. 71. (b) 82% and (c) 4%. 2 = h e p t a n a l . 20 = t e t r a d e c a n o i c acid. . 17 = p e n t a d e c a n e . 12 = d c c a d i e n a l . Chromatographic profile of Likens-Nickerson s t e a m distillate of p a l m acid oil. 21 = m e t h y l h e x a d e c a n o a t e .04-1. 22 . no.527 CHARACTERIZATION OF PALM ACID OIL I00 PALM ACID OIL (a) + 4" 4" 4" 44- 76 84 0 t-(N cq 44 ~ . 19 = eicosane. 3 = 2-pentylfuran. moisture content <2%. crude palm oil would also contain the same compounds. 14 -. .I 3o 35 4o FIG.10-undecadione.d o d e c a n o i c acid. PV <5. 18 -. practical but for the fact that. if carotenoids were their presumed source. 9 = decanal. _ _ ~ >1 Z~ 12 0 5 ]0 15 l 20 i 25 ~ 30 i 35 40 100 PALM ACID OIL 76 (b) 7 44 z m v 10 ~" 12 0 ~13411 15 12 I 5 I I I I I I 17 10 15 20 25 30 35 40 i00 u3 O Cq o3 PALM ACID OIL (c) 20 75 22 tD 44 u~ o. These values are based on the mean and ranges of 27 samples analyzed.67. 1 = hexanal. it is proposed t h a t PAO should have the following specifications: FFA >50%. Vol. 5 = 2-nonanonc. IV between 40-50. 7 = 2-nonenal. 16 = g e r a n y l acetone. saponification value 72-197 and unsaponifiable m a t t e r of 0. FIG. 11 = 6-.6-dimethyl-2.hexa d e c a n o i c acid. 3. JAOCS.undecenal. 10 = 2-decenal. 8 = dodecane. H e a d s p a c e c h r o m a t o g r a p h i c profiles of p a l m acid oih (a) 14%. 6 -. 15 = a-ionone. . 2. An analysis of the SDE volatiles of crude palm oil is now in progress to verify the source of these ketones. 4 = octanal.tetradecane. 13 = trans-2. G. VoI. Schamp. Hildebrand.H. Food Chem. Tsal. Soc. Takeoka. Bologa. 31.528 A. 12.637 19. Sanz.J.A. Wadsworth and G. L. Kuntom and N. Soc. H.019 21. Ibi& 40:1046 (1992).. and H. C. no. P. Kuntom and N. Dirinck. C.G. Peppard. 54:445 (1977). Careri and A.250 12. Goheen.108 24.758 16. G.V. Wu.I. Jang. 1993.R. 26. L. Britsch. 505. Dirinck and N. M. Russwam Jr.J.J. Evans. W.. M.P. Hamilton-Kemp. KUNTOM E T AL.. Dupuy. E. Flavor Science and Technology. Rohwedder and H. Progress in Flavor Research 1984. 54:62 (1977).L. K.A.603 29. Ibid. Reglero... and S. Applewhite. J. Light. M. 11. 32. Ibid. 2. A. Oil Chem.. W. Ibid.453 23.M. Ibi& 54:454 (1977).. and E.. Wychuyseand N.. John. p 2..D. Kuntom. 39:524 (1991). Chen.R.S. R. Puan Mazlina and Puan Halimah for their assistance in this project and to the personnel in palm oil refineries for their assistance in collecting the samples for this investigation. J. Parolari. Proceedings of the Second European Conference on Food Chemistry. Guentert. p. Gale.011 26. 40:2464 (1992). Potter. and J. Reineccius and J. A.746 Compounds Hexanal Heptanal 2-Pentylfuran Octanal 2-Nonanone n-Nonanal 2-Nonenal n-Dodecane n-Decanal 2-Decenal 6. Evans. [Received September 3. D. Virgili. G. Flath. Shaw. L.L. 1987.3.A.H. Williams.A.L. 49:106 (1972).M.. Hendersonand F. Liou.878 25.P. p.. Ibid. G. 25. 6. Dalen and H. A. Ibid~ 38:371(1961). Koller. Sehamp. (1989). Evans. 69:614 (1992).W. C. 1994] JAOCS.G. Dupuy. 8. 10.P.T. Preconcentration by Using Static-Head-Space Technique for Mass Spectrometric Identification. 9. New York. Ibid. E. Ellis and G. G. Takeoka. 20. 13. edited by J. Ibid. Sanz and I. 40:838 (1992). Ibid. Rios.M. Adda. Zmachinski. Moshomas and P.R. J. 18. 27.A..353 21. Schreyen. 4.E. A.G. Dirinck. Moser.2.J. Ibi& 38:2021 (1990). Nisperos-Carriedo.P. 16. List. Ibid.H. 33. 191.T. 21.H. R.. A. 42:645 (1977). 28. 39:939 (1991).2.375 18. 71. p 3.L.1. Miller. Keppler. 15. J. Nature 125:310 (1960). 40:1379 (1992).. Am.H.W. Barbueru. Ibi& 40:2232 (1992).G. Ibid.. Oil Chem. Wadsworth and M.4-decadienal trans-2-undecenal Tetradecene Alpha-ionone Geranyl acetone Pentadecane Dodecanoic acid Eicosane Tetradecanoic acid Methyl hexadecanoate Hexadecanoic acid 5. J. A. 54:225 (1977).531 22.788 15. Hoffmann. Shibamoso.. 7.. Y. G. 40:1925 (1992).. 183..T. Neth. C.I. Methods p 2. Martinez-Castro.640 24.936 22. E.0 10. Hoffmann and H. 30.F. 46:501(1969). Dutton. G.O. Ternalshi and M. 23.. Badings. Tabera~ J. Kuala Lumpur. Waltking. Schamp. Agric. REFERENCES 1. R. Dirinck. M. Loughrin.965 23. Olias.5.. Blanch.M. Ibid~ 40:257 (1992).J.H.750 21. G. IbidL 38:455 (1990). Flath..... Shimoda.. Bolzoni. M. Fegerson. T.P.10-undecadione 2. R. T.W. Amsterdam. Ibid~ 38:2054 (1990). and I.M. 34.P. R. Elaeis 1:53 ACKNOWLEDGMENTS We thank the Director General of PORIM for his encouragement and permission to publish this paper. Martens. Mon. Sheen.E. 17. p 3. R.O. H. and J. IbidL 38:802 (1990). and T. Kifli and K. D. Sanz and J. T. J.G.H.608 19.736 28.R. Milk and Dairy J. John Wiley & Sons Ltd...R.R. accepted February 16. edited by M. Ibid. J. 38:471(1990). Flath. Perez. T. R. 19. J. 1985.Y. List. M. Rayner.K. GA. Selke. H. De Frutos. TABLE 2 Compounds Identified in the Steam-Distilled Extract of Palm Acid Oil Peak number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 Retention time (min) 7. Selke. E. Schamp. R.E. Ibi& 54:461 (1977). 55:252 (1978).6-Dimethyl-2.D. 29. 3.7. Curie. Baldwin. 40:2389 (1992)..E. de Schroenmaker.R. A.D.D. T. C. Food Sci. Ibi& 38:1060 (1990). Mon and J. 14:215 (1960). J. Heraiz and G.L. PORIMTest Methods.A. Agric. Leino.. Buttery and R.643 12. G. J. 15-18 March 1983.. p.. C.. p 2. H. Gaddis. J. Food Chem. Buttini.M. and T. Thanks are also extended to research assistants Cik Rabeah.E. p 5.A. 22.R. Elsevier SciencePublishers B.. Mangra. 1988.. Am. Warner. Rome. 24. compiledby PalmOil Research Institute of Malaysia. 14. Legendre.B. Kuntom. Ibid. Tsai Ou and S. 5 (May 1994) .