Effects of thermal processing on transformation of polyphenols and flavor quality

Polyphenols (PP) are abundant in tea, coffee, cocoa and many plant-sourced foods, mainly including catechins, flavonoids, anthocyanins, chlorogenic acid and others. PP not only possess health benefits (anti-inflammatory, hypoglycemic, cancer-preventive, etc.), but are also important taste contributors in food. Thermal processing, such as roasting and drying, is one of the common treatments during food manufacturing, which markedly affects the transformation of PP. Therefore, this review summarizes the isomerization, degradation and polymerization products of PP in food during thermal processing and their interaction with other food components (amino acids, sugars and Maillard reaction products) in food. In addition, the formation of corresponding variety of new adducts, and their contribution to the flavor quality of food was also discussed. This review basically clarifies the transformation products and its flavor properties of PP during thermal processing of food, which provides a new strategy for using PP to regulate food flavor in the future.