Phenolic Compounds in Coffee and Tea Beverages

Abstract

Phenolic compounds are bioactive metabolites determined in plants which can be divided into six main groups: phenolic acids, flavonoids, tannins, stilbenes, lignans, and coumarins. These compounds possess not only high antioxidant activity but also many other bioactive properties, with anticancer activity as well. Very important sources of phenolic compounds in the human diet are coffee brew and tea leaves infusion. In this chapter, modern high pressure liquid chromatography (HPLC) and liquid chromatography coupled with mass spectrometry (LC-MS) methods are described for the determination of chlorogenic acids (CGAs) in coffees as well as catechins and theaflavins (TFs) in white, green, yellow, oolong, black, and pu-erh teas. Nowadays, the consumption of hot beverages is still common, and some other special coffees have become more and more popular. Apart from the roasting process, other special treatment processes of coffee beans such as steaming, decaffeination, or natural fermentation (Kopi Luwak coffee) influence the composition of chlorogenic acids and/or other phenolic compounds of coffee brew. Instant coffees and “ready-to-drink” coffee beverages are available on the market as well. In addition, coffee brews prepared by different methods contain a wide and dissimilar level of total chlorogenic acids and their lactones. Coffee leaves infusions, drunk from ages, also possess phenolic compounds and bioactive properties. Moreover, the preparation of tea leaves and/or buds (non-oxidized, semi-oxidized, fully oxidized, and post-fermented) influences the catechins, theaflavins, and other bioactive compounds present in tea infusions. Furthermore, the antioxidant activity of tea can be improved by the addition of spices (e.g., cayenne pepper), flowers (e.g., jasmine), herbs (mint or basil), fruits (e.g., lemon or dried fruits), bergamot oil, and also chocolate. The most common flavored black tea types are Earl Grey and masala. Other teas such as rooibos, yerba mate, and lapacho, best known and drunk in the places of origin, become more popular in the USA and Europe. They also contain phenolic acids and other phenolic compounds among other bioactive compounds.