Production, Quality, and Biological Effects of Oolong Tea (Camellia sinensis)

Abstract

Oolong tea is a semi-fermented Chinese traditional tea that dates back centuries and now its unique characteristics are attracting more and more consumers worldwide. The formation of Oolong tea's special quality is attributed to the proper processing of the fresh tea leaf. The quality of Oolong tea can be evaluated by aroma, flavor, color, and appearance with aroma and flavor being the two most important quality indices. The formation of the distinct aroma of Oolong tea depends largely on the decomposition of lipids and carotenoids. However, other compounds that can be hydrolyzed and/or oxidized also contribute to Oolong tea's special aroma. During the processing of Oolong tea, some major flavor compounds are formed by the oxidation of catechins, amino acids, and sugars. The flavor of Oolong tea is complex due to the interaction of many different flavor compounds. Oolong tea exhibits antioxidant, anticancer, antiobesity, prevention of atherosclerosis and heart disease, antidiabetes, and antiallergic effects. Management of environmental factors, selection of tea cultivars and improvements in tea production needs to be emphasized to ensure the high quality of Oolong tea. The exact mechanisms responsible for the beneficial health effects of Oolong tea are not known.