This study was conducted to recover edible bird's nest (EBN) hydrolysates from different grades of EBN, including the industrial by-products, using enzymatic treatment. The nutrient, physicochemical properties and antioxidant activities of the recovered hydrolysates at different hydrolysis times were evaluated. Results showed that the recovery yield of enzymatic hydrolysis was above 89% for all grades of EBN and the degree of hydrolysis increased over time. Nitrite content (0.321–0.433 mg/L) was below the permissible tolerance level for all samples. Interestingly, the antioxidant activities (DPPH and ABTS scavenging activities and ferric reducing antioxidant powder (FRAP) activity) were significantly higher (P ≤ 0.05) in hydrolysates recovered from EBN by-products (EBNh_C and EBNh_D) as compared to the high grade EBN hydrolysates (EBNh_A and EBNh_B). The in-vitro probiotic activity of EBN and its hydrolysates were examined using the probiotic bacterium Lactobacillus plantarum. Evidently, EBN by-products hydrolysate (EBNh_D) recorded the highest number of L. plantarum (1.1 × 10¹¹ CFU/mL), indicating that low grade EBN has the potential as prebiotic material that promotes probiotic activity. This study demonstrated the concept of using EBN by-products hydrolysates for various applications, such as functional ingredients with enhanced bioactivities, to improve its economic value.

Edible bird's nest (EBN) hydrolysates have been proven to exhibit enhanced bioactivities. However, being a macromolecule, fractions with different molecular weights would have different properties and bioactivities. Hence, this research was aimed to determine the chemical properties and antioxidant activities of freeze-dried (EBN_FD) and spray-dried EBN (EBN_SD) hydrolysates fractionated using gel permeation chromatography (GPC). Overall, two well-separated fractions were identified (EBN_fFD1, EBN_fFD2, EBN_fSD1 and EBN_fSD2). EBN_FD demonstrated significantly higher (P ≤ 0.05) peptide (3.6%), total carbohydrate (27.7%) and sialic acid (18.2%) contents than that of EBN_SD. Similar trend was observed in low molecular weight fractionates (EBN_fFD2 and EBN_fSD2). Meanwhile, the first fractionates (EBN_fFD1 and EBN_fSD1) exhibited significantly higher (P ≤ 0.05) hydroxyl radical (•OH) scavenging activity. Fourier transform infrared (FTIR) spectroscopy demonstrated that all EBN fractionates have similar spectrum, except in the region of N—H (amide Ⅱ) and C—H alkyl group. In conclusion, EBN fractionates with different molecular weights showed different chemical properties and antioxidant activities.