Degradation of cyanogenic glycosides of bitter apricot seeds (Prunus armeniaca) by endogenous and added enzymes as affected by heat treatments and particle size

Bitter apricot (Prunus armeniaca) seeds (kernels) are by-products of the apricot processing industry. They contain approximately 50–150 μMol/g (dry weight basis) of potentially toxic cyanogenic glycosides, mainly amygdalin and prunasin. The present paper deals with the degradation of these glycosides by endogenous and added enzymes in raw and blanched seeds of different particle sizes. A hot water blanching treatment of 20 min at 100 °C was adequate to inactivate endogenous β-glucosidase activity in raw bitter apricot seeds. In addition to raw seeds, such blanched seeds were used as an experimental model to investigate the effect of particle size and added individual enzyme preparations on the degradation of cyanogenic glycosides. Finely ground (< 2 mm) fractions showed increased glycoside degradation, supporting the hypothesis that particle size is a limiting factor for enzymic degradation. Our hypothesis that added pectinase activity would enhance degradation of glycosides by improving enzyme-substrate contact could not be affirmed. Furthermore, it was observed that substantial enzyme addition (β-glucosidase) is required to fully degrade residual glycoside levels in raw and/or blanched seeds.