Simultaneous enzyme catalysis extraction: A versatile technique for the study of flavor precursors

The identification of glycosidically bound volatiles from apple fruit (Malus sylvestris Mill cult. Jonathan) was achieved by isolation of a glycosidic extract by Amberlite XAD-2 adsorption and methanol elution followed by enzymatic hydrolysis with emulsin. Capillary gas chromatography and combined capillary gas chromatography-mass spectrometry revealed for the first time the occurrence of the following aglycons: 1-butanol, 2-methyl-1-butanol, 1-hexanol, 2-methylbutanoic acid, benzyl alcohol, 1-octanol, 2-phenylethanol, 1, 3-oct-5(Z)-enediol, 1, 3-octanediol, 4-vinylguaiacol, eugenol, 4-hydroxyphenylacetic acid, 3-hydroxy-βdamascone, 4-hydroxy-3-methoxyphenylacetic acid, 3-oxo-α-ionol, and vomifoliol. The concentrations of the liberated aglycons were found to change over time when the glycosides were subjected to enzymatic hydrolysis. Thus, the attractive C¹³ norisoprenoids were isolated in later hydrolysis steps in large amounts, although they occurred only in traces in the first hydrolysate. An apparatus was developed allowing continuously the simultaneous enzyme catalysis and extraction (SECE). Mathematical calculations of the enzymatic cleavage of glycosides were performed.