Evaluation of physicochemical properties, amino acid profile and bioactivities of edible Bird's nest hydrolysate as affected by drying methods

Previous studies indicated that enzymatic hydrolysis of edible bird's nest (EBN) glycoproteins to glycopeptides resulted in higher bioactivities than raw EBN. However, a drying process is necessary to remove water after hydrolysis to increase the shelf-life and broaden its application. The current work was carried out to study the properties of EBN hydrolysates as affected by different drying methods: oven-drying (EBNod), spray-drying (EBNsd) and freeze-drying (EBNfd). The dried EBN hydrolysate yields were in the order of EBNfd > EBNod > EBNsd. Both EBNfd and EBNsd were relatively stable against microbial and biochemical changes as the water activity was below 0.60. Low lightness (L*), high yellowness (b*) and colour intensity (C) were obtained from EBNod, suggesting that the oven-drying had a negative effect on the colour appearance. EBNsd has a high soluble protein content (15.14 ± 0.56g/100g) and low viscosity (1.65 ± 0.17 mPa s), indicating high solubility when incorporated into food products as a functional ingredient. Besides, EBNfd exhibited a high degree of hydrolysis (45.09 ± 2.09%), essential amino acid content (42.62 ± 0.23g/100g), antioxidant activities [DPPH (60.80 ± 0.67%); FRAP (11.99 ± 0.29 mg TE/g)] and antihypertensive (75.76 ± 1.08%) activities. The FTIR spectrum showed that the powders exhibited similar functional groups. Freeze-drying of EBN with low-temperature exposure is preferable because it exhibits minimal effects on the properties of EBN hydrolysate.