Ultrasound-assisted enzymatic hydrolysis enhances anti-inflammatory and hypoglycemic activities of edible Bird's nest

Abstract

Edible bird's nest (EBN) is the solidified saliva of swiftlet Aerodramus fuciphagus. It is an expensive premium health food that has long been consumed, especially in China. However, the broken EBN pieces left behind after the cleaning process have low market value due to high contaminants, particularly fine feathers. Thus, EBN hydrolysate (EBNH) is the best downstream product to add value to this low-grade EBN. This study aims to investigate the effects of ultrasound pretreatment on the enzymatic process of EBNH production. Initially, the EBN was treated with ultrasound at different amplitudes (30%, 60%, 90%) and times (15 min, 30 min, 45 min), then hydrolyzed for 1.5 h at 60 °C using papain enzyme (pH 7). The viscosity, degree of hydrolysis (DH), total soluble protein (TSP), anti-lipoxygenase activity and α-amylase inhibition activity of the EBNHs produced were determined. Results suggested that ultrasound amplitude exerted a more prominent effect than time in lowering the viscosity of EBNH. Viscosity of EBNH dropped by 4.4 folds–6.58 ± 0.10 mPa s after 30 min ultrasound at 90% amplitude. Under this condition, the produced EBNH exhibited 61.66 ± 2.89% anti-lipoxygenase activity and 77.40 ± 5.41% α-amylase inhibition activity, which were >100% and 43%, respectively higher than the control. However, ultrasound had exerted no significant effects on DH and TSP. These findings speculate that ultrasound enhances bioactivities of EBNH by modifying intermolecular interactions between glycopeptides and glycoproteins. This study proved that ultrasound is a promising green pretreatment technology in EBNH production. Besides, this study also provides an insight into the importance of pretreatment in bioactive EBNH production.