Properties Of Tea, Cocoa, Effects Of Drinking Them
( Originally Published 1936 )
Tea and coffee owe their stimulating effects to the same substance —caffeine, and cocoa to a closely related substance—theobromine. Theobromine is di-methyl-xanthine and caffeine is tri-methyl-xanthine. Chocolate is almost the same as cocoa except that it cotains more fat. —Both contain about 1 to 2 per cent theobromine, but this substance does not have the stimulating power of caffeine, and they are less objectionable than coffee from that standpoint.
The amount of caffeine in tea is such that an average cup of tea contains about a half of what an average cup of coffee does.
Tea also contains tannic acid, which is an astringent. The amount of tannic acid in tea is very Targely a matter of the kind used and the length of time the tea is steeped. The difference between black tea leaves and green tea leaves is simply in the preparation. Black and green teas can be made of leaves from the same bush. The black leaves have been put through a process of fermentation which oxidizes a considerable portion of the tannic acid. Hence green tea leaves will produce a tea with more astringent property than black.
Prolonged infusion of the tea also extracts more tannic acid. Steeping for five minutes extracts about 6 per cent, while 20 minutes' steeping extracts about 12 per cent. In the meantime, the amount of caffeine extracted is no greater.
So the only thing prolonged infusion does for tea is to get out more astringent substances. Five minutes infusion brings out all the desirable substances and any longer period is no advantage. Rather, the contrary. The muslin tea bag is thus seen to be the best friend the tea drinker has, allowing her to steep the tea exactly the proper length of time.