Studies on aroma generation in lulo (Solanum quitoense): enzymatic hydrolysis of glycosides from leaves

Five C13-norisoprenoid glycosides, isolated from lulo (Solanum quitoense) leaves, were subjected to enzymatic hydrolysis with a commercial glucosidase (emulsin) and also with an enzymatic preparation having glycosidase activity, isolated from lulo fruit pulp. The volatile compounds generated after reaction were characterized by capillary GC and capillary GC–MS. Lulo fruit glycosidases were extracted by ammonium sulfate precipitation at pH 6.5 and subjected to fractionation by hydrophobic interaction chromatography (HIC) on phenyl Sepharose® gel, and some of their properties were determined. As the result of enzymatic hydrolysis with exogenous enzymes (emulsin), glycosides isolated from lulo leaves produced only the aglycone (glycosidically bound volatile); in contrast, enzymatic hydrolysis of glycosides, using endogenous enzymes (lulo fruit glycosidases), generated additional volatile compounds, some recognisable as components of fruit flavour. The role of lulo leaf glycosides as flavour precursors was confirmed.