Glycosidically bound aroma precursors in fruits: A comprehensive review.

Fruit aroma is mainly contributed by free and glycosidically bound aroma compounds, in which glycosidically bound form can be converted into free form during storage and processing, thereby enhancing the overall aroma property. In recent years, the bound aroma precursors have been widely used as flavor additives in the food industry to enhance, balance and recover the flavor of products. This review summarizes the fruit-derived aroma glycosides in different aspects including chemical structures, enzymatic hydrolysis, biosynthesis and occurrence. Aroma glycosides structurally involve an aroma compound (aglycone) and a sugar moiety (glycone). They can be hydrolyzed to release free volatiles by endo- and/or exo-glucosidase, while their biosynthesis refers to glycosylation process using glycosyltransferases (GTs). So far, aroma glycosides have been found and studied in multiple fruits such as grapes, mangoes, lychees and so on. Additionally, their importance in flavor perception, their utilization in food flavor enhancement and other industrial applications are also discussed. Aroma glycosides can enhance flavor perception via hydrolyzation by β-glucosidase in human saliva. Moreover, they are able to impart product flavor by controlling the liberation of active volatiles in industrial applications. This review provides fundamental information for the future investigation on the fruit-derived aroma glycosides.