methods in nutritionA study of caffeine in tea I. A new spectrophotometric micro-method II. Concentration of caffeine in various strengths, brands, blends, Downloaded from ajcn.nutrition.org by guest on April 7, 2014 and types of teas1-3 Daniel S. Groisser ABSTRACT A new spectrophotometric micro-method for the determination of caffeine in tea is described. This method is then used to evaluate the caffeine content of a variety of brands and blends of bagged and loose hot tea prepared in different strengths and by different brewing methods. In addition, the caffeine content of instant tea, ice tea, and Mr. Coffee automatic tea is evaluated. Am. J. Clin. Nut,. 31: 1727-1731, 1978. Tea, next to water, is the most frequently The purpose of this study is to evaluate the consumed beverage in the world. Conse- caffeine content of various brands and quently, the ingestion of caffeine, an impor- strengths of teas, prepared by the dipping tant ingredient of tea as well as coffee, has method or by brewing for consumption by become a daily habit for many. Because med- tea drinkers. ical literature concerning the physiological In addition, a new improved spectropho- effects of caffeine has shown the drug to be tometric micro-method has been developed an important contributing factor in some pa- to analyze the caffeine concentration in tea. tients with heartburn, diarrhea, and peptic This method and the evaluation of the caf- ulcer disease, and because of its well-known feine content of tea is described. effect as a central nervous system stimulant, a study of the caffeine content of a cup of An improved method for caffeine various brands and strengths of tea has been determination In tea performed (1-5). Several spectrophotometric methods for analyzing The question, “how much caffeine is in a caffeine concentrations in liquids are available (6-9). cup of tea?” is complex; the number of vari- Although accurate, these methods are time-consuming ables is great. There are a wide variety of and/or use large volumes of material. The new proce- brands and blends of bagged and loose tea, different brewing methods, and personal pre- From the Department of Pathology and Laborato- ferred strengths. As yet the literature does not ries, Mountainside Hospital, Montclair, New Jersey. 2Supported in part by a grant from the New Jersey contain information concerning the quantity Academy of Science. of caffeine ingested in tea that attempts to 3This work was presented in part at the Annual consider all or many of these diverse ele- Meeting of the New Jersey Academy of Science, April 2, ments. 1977. The American Journal of Clinical Nutrition 31: OCTOBER 1978, pp. 1727-173 1. Printed in U.S.A. 1727 Using the previously described method. (Beckman Methods Instruments. The extraction is augmented by 1 Tetley 18 48 70 the additioi of NaCl. Of those polled 95% choose density of the sample versus blank H2S04 cuvet at 273 their strength of tea by the color of the beverage. Inc. and one strong cup often from the 20 cups covery was better than 95% (see Table I). All chemicals and equipment used are of analytical grades and are used without further purifica- tion. mean value reported. and 50 hospital personnel were asked to visually select one weak. The caffeine 3 Tetley 18 48 70 is further isolated in H2SO4. procedure utilizes the relatively non-volatile H2S04 which allows samples to be pipeted into and out of the Tea prepared by color comparison Tea bags or porous metal tea bags containing 2. and 10. 20 C. 25. a Each trial was carried out by using different tea bags The optical density of the H2S04 layer is read on a on each of 4 different days. Read the optical choose their strength of tea.” and “strong” cups of tea NaCI. medium. The color of the weak. two ways: 1) on the basis of strength (color). 2) on Adjust pH of the beverage to 8 to 9 using 1 N NaOH at the basis of package directions for brewing. and Mr. one medium. Coffee Automatic teas were not made in . cannot be a Three aliquots per sample were analyzed and the compared with the color of Black and Oolong. 700 people were polled as to the criteria they use to (bottom) layer into a quartz cuvet. the basis of color development. various strengths and brands of tea were studied for caffeine Procedure content. is inexpensive.0 cg/m1 are tea prepared with 5 N H2S04. Of the 205 people 90% chose color concentrations that were almost identical in each of the Advantages weak. (Black tea. and strong tea that received the most frequent The described method has the following advantages: positive responses in each of the categories was used as Sample and reagent quantities have been reduced. mr In this procedure caffeine is isolated from tea at pH Trial no. and the procedure is less time-consuming. Three aliquots per sample spectrophotometer and the amount of caffeine present in the beverage is calculated.org by guest on April 7.” “medium. the the standard for the caffeine experiment. medium. medium. Pipet 0. single brand of tea were made.5. The reproducibility of Tea+25 73 72 99 this color matching was excellent and is shown in Table Tea+50 98 95 97 2. which helps to break the emulsion 2 Tetley 19 48 71 formed by the oils present in the beverage. Black and Oolong Tea+l0 58 57 98 teas were made in this fashion. 2014 A model DB spectrophotometer is used. Calif. separating it from other 4 Tetley 18 48 70 constituents of tea such as theobromine and theophylline. is less time-consuming (20 min per aliquot standards-as represented by caffeine content mg/180 compared to 60 or more min) and is highly accurate. Brand Weak Medium Strong 8 to 9 (20 C) by extraction into the relatively nonpolar organic solvent benzene. medium.. uses less reagents. To verify this assump- Centrifuge for 5 min. which pro- duces the copperish color most Americans are accus- Reproducibility tomed to. Downloaded from ajcn. Determination of caffeine concentration In Caffeine standards of 2. 7. Instant. is easily Reproducibility of color matching of tea to performed. which yields a pale green color. cuvet more readily without damaging the spectropho- Method tometer. Against a Tea plus caffeine added Ideal recovery Actual recovery uniform background. Carefully pipet some of the H2S04 tion. 5. Fullerton. was the blend used. and strong cup of tea Centrifuge for 10 min at 3500 rpm.1728 GROISSER dure. mg of caffeine were added to tea were performed.0.1 ml of tea into a 20 ml teflon capped tube. The comparison was made of teas prepared in Make 180 ml (6 ounces) of tea to desired strength.5.35 g TABLE 1 of loose tea leaves (the amount of tea found in most Recovery of caffeine from tea (mg/h80 ml)a bagged brands) were dunked at a uniform rate into Percent recov uniform glass jars containing boiling water. The popular con- from the benzene (top) layer into a teflon capped test cept is that most people choose their strength of tea on tube containing 5 ml of 5 N H2SO4. Calculate the caffeine concentration as mg/h80 ml ing this information. partially an outgrowth of the Axehrod-Reichenthal TABLE 2 method (6). Green tea.) A survey in which 205 Three recovery experiments in which 10. and strong range. ing The standards were in the same type of jar and were at Tea+ 0 48 the same temperature as the samples. and strong cups of cry tea were made by color matching with these standards. Materials. Shake tube for I min using a vortex super mixer. Shake for 30 sec. Pipet 10 ml benzene into the tube and add about 0. were analyzed and the mean value is reported. The choice of a weak. weak.5 g Criteria for “weak. Re.nutrition. ice. 20 different color gradations of a of beverage. Utiliz- nm. and. 92634). Carefully pipet S ml is highly variable and individualistic. often was conducted. and unencased loose tea were left to steep for 4 brands-Lipton. package directions. 2014 TABLE 3 Tea made by strengths-comparison of caffeine content mg/180 ml of domestic an d imported tea. and automatic tea were made by individual package instruc- per strength and package directions (Table tions. ice. Red Rose contains the most caffeine followed The caffeine content of weak. medium tea 48 to 84 mg. Table 4 includes the caffeine content directions.org by guest on April 7. . Bagged tea. Coffee Automatic tea). and by Salada. and Red min with the jar covered. Coffee automatic Loose 68 a Three aliquots per sample were analyzed and the mean value is reported. and Tetley. the Tea prepared by package instruction type of packaging and the blend of tea (Black.nutrition.) Instant. Lipton. These latter teas were analyzed for caffeine of all the teas tested by package directions. content only by following package directions for prepa- Tables 3 and 4 include the type of tea (hot. 3). or Oolong). ration. instant. TABLE 4 Tea made by package directions-comparison of caffeine content (mg/180 ml) of domestic and imported teas” Brand Type Packed Blend Four-mm steep Red Rose Hot Bag Black 46 Salada Hot Bag Black 40 Lipton Hot Bag Black 38 Tetley Hot Bag Black 25 English Breakfast (Twinings) Hot Bag Black 52 English Breakfast (Twinings) Hot Loose and metal bag Black 58 English Breakfast (Twinings) Hot Loose Black 77 Daijeeling (Twinings) Hot Bag Black 65 Formosa (Jackson) Hot Loose and metal bag Oolong 42 Chinese (Hong Kong) Hot Bag Green 36 Pan fried Hot Loose and metal bag Green 81 Lipton Instant Loose 62 Nestea Instant Loose 48 Lipton Ice water sugar and Loose 76 lemon Nestea Ice water sugar and Loose 67 lemon Lipton Mr. Coffee automatic Loose 71 Tetley Mr. (Package directions on most Rose-display a wide range of caffeine levels brands call for a 3 to S min steep. loose tea in porous metal The most commonly consumed domestic bags. strong tea for each brand tested is listed in For each of the three strengths and package Table 3. Salada. ice. the domestic teas contain less caf- Downloaded from ajcn. all teas tested were made by standard Green. For each strength. weak tea 18 to 45 mg. Tetley. In addition. or Mr. CAFFEINE IN TEA 1729 this fashion. medium. Stren gths of tea established by color comparison” Brand Type Packed Blend Weak Medium Strong Domestic teas Red Rose Hot Bag Black 45 62 90 Salada Hot Bag Black 25 60 78 Lipton Hot Bag Black 25 53 70 Tetley Hot Bag Black 18 48 70 Imported teas English Breakfast (Twinings) Hot Bag Black 26 78 107 English Breakfast (Twinings) Hot Loose in metal bag Black 39 84 90 Darjeeling (Twinings) Hot Bag Black 39 74 91 Formosa (Jacksons) Hot Loose in metal bag Oolong 42 65 78 a Three aliquots per sample were analyzed and the mean value is reported. strong 70 to 107 mg and by package Results directions 24 to 45 mg. The author should . and 46 mg as obtain a level of caffeine that is not signifi- prepared by package directions. and Mr. be- Instant tea. However. For all hot teas two cups of weak tea). medium 66 mg. When the leaves of loose English Breakfast It is of interest that the tea bag or porous Tea are encased in the metal tea bag. the metal container tends to retard some of the caffeine yield a similar to that of bagged caffeine leakage into the cup-thus tea pre- English Breakfast Tea (Tables 3 and 4). Likewise. Many that compare with that of a strong cup of the experiments have been performed with 5 to hot domestic teas (mean 77 mg). contains approximately one. does not result in the When package directions were followed for introduction of a physiologically significant all hot teas in Table 3. and certainly no been discussed. (mean the tea unpalatable to the tea drinker (14). possibly to the point of of caffeine in tea and other beverages has restlessness or sleeplessness in some people. coca cola (40 theobramine (2 mg per cup) and theophylline to 72 mg/12 ounces). 15). sible yet to decaffeinate tea.D. the caffeine content amount of caffeine into the body (if indeed was approximately between that of a weak the patient restricts himself to one or even and medium cup (Table 4).org by guest on April 7. has a similar cause caffeine contributes significantly to the caffeine content to that of a medium cup of flavor of the tea. cantly greater than a weak cup of tea. opment to the water. it has not been deemed fea- made under the same condition. tea has been evaluated. Although decaffeinated products are avail- lish Breakfast in paper or metal tea bags able for coffee. 72 mg). definitive information exists in the literature The author thanks R. One author has sug- Discussion gested that perhaps a 150 ml cup be used as In addition to tea. Other experiments have failed to mention cup size. The the so-called weak tea. The present experiment establishes that kind guidance and for his review of this manuscript. Ice tea. yield similar caffeine concentrations tea. siderably higher caffeine level than the Eng. NoDoze tablets (100 (1 mg per cup) have been detected (13. Sally Bailey for her development. Mean concentration of coffee or a strong cup of tea. been scanty infor- the caffeine content of tea as contrasted to mation concerning the amount of caffeine in the caffeine content of other beverages has various strengths of tea (13). The amount of Conclusion ingested caffeine that produces increased A new method for measuring the quantity awareness and acuity. 77 versus 92 mg for strong “take a weak cup of tea” to “settle your and 37 versus 63 mg for package directions. New Jersey. Biochemist at concerning the quantity of caffeine in weak Mountainside Hospital. only small quantities of milk chocolate (3 mg/ounce). been described. The relationship of There has. stomach. mean concentration of caffeine was: prepare tea according to package instructions weak 32 mg.” therefore. in general. varies with the individual. Coffee Automatic tea. caffeine may be ingested a standard (13). In addition. The advice of reveals 28 versus 37 mg for weak.1730 GROISSER feine than the more expensive imported black third the quantity of caffeine found in a cup teas (Tables 3 and 4). the size of the cup is important. How.Montclair. in cocoa (50 mg/6 ounces). 2014 loose English Breakfast leaves yielded a con.. as judged by its color author is also indebted to Ms. 56 versus parents and occasionally of physicians to 75 mg for medium. for his tea. 5Y2 ounce cups. (mean In any experiment regarding caffeine in 70 mg). (mean 55 mg). the caffeine 100 to 150 mg is considered a physiological content of different brands and strengths of dose and may produce side effects (5). as well as in coffee (100 to 150 mg/6 ounce cup) (10-12). vestigation. mg per tablet). Sandhu. prescription medication such as Cafergot (100 Caffeine is not the only xanthine present mg per tablet). Approximately Utilizing this new technique. made by package directions. in in tea. Ph.nutrition. unencased caffeine for the same degree of color devel- and time exposure Downloaded from ajcn. those who tested. pared with loose tea leaves delivers more ever. We have chosen a 6 ounce in many forms as in the over-the-counter cup as a standard throughout the entire in- medications such as APC (32 mg per tablet). constant encouragement and advice. its removal would render hot domestic tea (mean 56 mg). GOODMAN. 14. A. Non- Diseases 18: 391. A. J. and sodium in 6. Chem. C. G. MARTINEK. N. 52: 1133. Med. tory facilities for this research. bution to the character of the beverage. AND A. Ther. Anal. AND D. Offi- 1. M. 13. Xanthines.. H. 107: tainside Hospital Laboratories for providing the labora. Caffeine content of beverages and choc- response to coffee and caffeine. logical Basis of Therapeutics. J. CAFFEINE IN TEA 1731 also like to thank F. Am. 2014 Exp. Pharmacol. NAGY. Chem.nutrition. 1976. CRISPIN AND D. Pharmacol.. 1953. 15. G. Am. J. The effects of specific coffee. 10: 215. New York. Psy. MILLAN. J. References 8. 2. J. J. 9. and cocoa. 1974. 11: 239. The Pharmaco. 229: 337. 1944. S. tea. foods on the lower esophageal sphincter. Med. J. BOOTH. J. Official Methods of Analysis. Tea Coffee Trade J. J. WARREN. Assoc. J. GOLDSTEIN. BABKA. 17: 717. olate. AXELROD. 1973. CASTELL. New EngI.. S. Tea Coffee Trade J. . Off. cat and man. JR. AND A. 158: 1030. cial methods of analysis. J. The effect of caffeine could help better standards.org by guest on April 7. Nutrition and the M. Association of Official Analytical Chemists. 12. S. 1970. Food chotropic effects of caffeine in man. Med. J. Assoc. 1965. tannins. Physiol. REICHENTHAL.. KAISER AND R. M. p. D. Am.D. Assoc. 7. Agr. 293: 897. Ther. Exptl. upon gastric secretion in the dog. AND J. NEWTON. ROTH. J. 1969... D. 1975. D. SNAINE. caffeine in man and a method for its estimation in 1955. 519. How much caffeine in a cup often and 4. Director of Moun. 1975. L. BURG. A. Association of Official Agricultural Chemists. The fate of coffee. J. Better procedures for analyzing caffeine 3. Gastric acid 10. Digest. Ivy. COHEN. Watson. 141: 454.. Downloaded from ajcn. GILMAN. 9: 3. secretion and lower esophageal sphincter pressure in 11. volatile components of black tea and their contri- 5. 144: 26. AND G. 367. 1965. 1: 40. LEE. 150: 146. biological material..D. 1973. 1969. R. M. 1975.