Enzymatic hydrolysis improves digestibility of edible bird's nest (EBN): combined effect of pretreatment and enzyme

Numerous studies proved the better health benefits of edible bird's nest hydrolysate (EBNH) than edible bird's nest (EBN). This study was conducted to investigate the effect of different pretreatments and enzymes on the chemical properties of EBNH. The degree of hydrolysis (DH), total soluble protein, UV-Vis absorption spectrum and FTIR spectrum of EBN and EBNH were determined. Besides, the digestibility of EBN and EBNH were also determined through simulated in vitro digestion. Initially, the 4% w/v EBN was treated with different pretreatments [boiling, combined boiling with ultrasound (40 kHz,250 W) and autoclave at 120 degrees C]. Then, the pretreated EBN was subjected to 2 h hydrolysis using pepsin, trypsin, papain and pancreatin, respectively. Besides, two-stages enzymatic hydrolysis using pepsin-papain, papain-trypsin and papain-pancreatin enzymes were also investigated. Results obtained propose that the combination of autoclave pretreatment and pancreatin hydrolysis produced EBNH with the highest DH (11.19 +/- 0.18%). Heat treatment was crucial to unfold the glycoprotein, hence facilitate enzymatic hydrolysis. Two-stages enzymatic hydrolysis was proven less efficient than the process with heat pretreatment. Besides, papain was proven as the best enzyme to increase solubility of EBN glycoprotein. EBNH produced from boiled EBN using papain contained the highest total soluble protein content (459.63 +/- 66.01 mg g(-1)). Results of UV-Vis absorption spectrum and FTIR spectrum reveal that efficiency of enzymatic hydrolysis of glycoprotein was strongly influenced by the extent of protein unfolding and aggregation. Among the EBNHs, EBNH produced from autoclaved EBN using pancreatin enzyme had the best digestibility. This study provides insight into the importance of pretreatment method and enzyme type in ensuring nutritional quality of EBNH.