Theobromine and caffeine are methylxanthines and found in cocao, coffee and tea. Methylxanthines (a class of alkaloids) are easily extracted in hot water, hence their prevalence in hot cocoa, coffee and tea. The concentration of methyxanthines varies due to growing environment and processing of cocoa, coffee and tea. Theobromine is believed to be a blood vessel widener and a diuretic.
Blauch and Tarka (1983) used the HPLC methodology to determine the caffeine and theobromine content in commercially bought coffee, instant cocoa mix (9) and tea (14). The coffees were either ground or instant. Ground coffee was either percolated (automatic 7 min.or non-automatic stove-top) or drip (automatic or non-autmatic 6 min). Instant coffee (0.5 g) was dissolved in 125 ml boiling water. Tea bags were immersed in 177 ml boiling water and brewed for 5 min. Instant cocoa (3.0 g) was added to 125 ml boiling water. The authors collected data on caffeine and theobromine by HPLC quantification using pure standards.
Caffeine: coffee, instant cocoa and tea all contained varying concentrations of caffeine. The caffeine content in instant cocoa ranged from 1.0 to 7.8 mg/cup. In tea, the caffeine content ranged from 30.2 (orang and spice) to 65.0 mg/cup (American Black Tea). There was one imported black tea that contained 67.4 mg/cup of caffeine.
Instant coffees caffeine content ranged from 46.7 to 67.6 mg/cup. The caffeine content in ground coffee made by the drip method was 7 to 29.0 mg/cup higher than by the percolator method. Blauch and Tarka (1983) ascribe the higher caffeine concentrations in the drip method to the finer particle size of the ground coffee used for the drip method. There was no statistical difference in caffeine content between automatic or non-automatic drip methods.
Theobromine: all coffees tested in this study didn’t show any theobromine. The instant cocoa samples (9) showed theobromine concentrations from 39.5 to 79.5 mg/cup. Theobromine content in the different teas (14) ranged from 1.2 (orange and spice) to 3.6 mg/cup (American Black). Again one imported black tea showed 4.4 mg/cup of theobromine. The one decaffeinated tea included in this study contained 0.3 mg/cup theobromine.
We can see from Bluach and Tarka’s (1983) study that caffeine content varies among the different coffee, instant cocoa and tea brands. Likewise, theobromine concentrations vary among different cocoa and tea brands. Instant cocoa shows the highest amount of theobromine compared to tea and coffee.
Blauch, J. L. and S.M Tarka Jr. 1983. HPLC Determination of caffeine and theopbromine in coffee, tea, and instant hot cocoa mix. Journal of Food Science. 48:745-747.