Modulating conversion of isoflavone glycosides to aglycones using crude beta-glycosidase extracts from almonds and processed soy

- Heat inhibited β-glycosidase activity of almonds but enhanced activity in soy.
- Thermally treated soy affects β-glycosidase mediated conversion of glycosides to aglycones.
- β-Glycosidase and isoflavone composition used to control conversion of glycosides to aglycones.
- Processed soy is an alternative to almonds for aglycone enrichment of soy foods.

Food processing alters the physicochemical state of soy which can enhance chemical and enzymatic conversion of isoflavones to their aglycone forms. This study investigated the role of β-glycosidase from processed soy-ingredient mixture (SIM) or almonds, and examined the impact of isoflavone composition in mediating conversion to aglycones. β-Glycosidase activity was quantified using p-nitrophenol-β-d-glucopyranoside and SIM isoflavone extracts. Almond β-glycosidase activity was significantly (p < 0.001) reduced after roasting (99% reduction) or steaming (97% reduction) compared to raw almonds. SIM β-glycosidase activity, however, increased, with steaming by 66% (p < 0.001) and with roasting by 52% (p = 0.022), compared to raw SIM. After incubation with β-glycosidase, percentage of aglycone (total aglycone/total isoflavones) in SIM isoflavone extracts increased significantly in raw (35%), fermented (48%), roasted (88%) and steamed (91%) SIM, compared to their initial (∼5%) compositions. Manipulation of β-glycosidase activity and isoflavone composition can be used to modulate aglycone content in soy food products.