Effect of heat treatment and enzymatic protein hydrolysis on the degree of hydrolysis and physicochemical properties of edible bird’s nest

Abstract

This study reported the effect of heat treatment and protein enzymatic hydrolysis on the degree of hydrolysis (DH) and physicochemical properties of edible bird’s nest (EBN). The EBN samples were subjected to eleven different processing treatments which were control EBN (raw), 30 mins normal boiled EBN (NB30); 30 mins normal boiled EBN followed with protein hydrolysis using 1% Alcalase® (NB30H); 60 mins normal boiled EBN (NB60); 60 mins normal boiled EBN followed with protein hydrolysis using 1% Alcalase® (NB60H); 60 mins slow cooked EBN (SC60); 60 mins slow cooked EBN followed with protein hydrolysis using 1% Alcalase® (SC60H); 120 mins slow cooked EBN (SC120); 120 mins slow cooked EBN followed with protein hydrolysis using 1% Alcalase® (SC120H); autoclaved EBN at 121oC for 15 mins (A); autoclaved EBN at 121oC for 15 mins followed with protein hydrolysis using 1% Alcalase® (AH). The treated EBN samples were then freeze dried prior to further analysis. This study found that heat treatment alone produced EBN sample with lower DH (5.84% to 14.54%) as compared to those undergone combined heat treatment and enzymatic protein hydrolysis (12.16% to 22.59%). EBN samples in this study gave solubility of 4.52 - 87.11%, water holding capacity of 3.82 - 17.9 mL/g, oil holding capacity of 4.87 - 7.65 mL/g, emulsifying capacity of 18.08 - 56.15%, emulsifying stability of 12.03 - 50.34%, foaming capacity of 0.75 - 359%, foaming stability (after 60 mins) of 58.89 - 96.39% and viscosity (for 1 - 10% EBN sample) of 26.67 - 7526.67 mPa.s. It was found that there was a positive correlation between DH and solubility, emulsifying capacity and emulsifying stability of EBN samples. However, a negative correlation was found between DH and water holding capacity and viscosity of EBN samples. Furthermore, there was no correlation between DH and oil holding capacity and colour profiles. Thus, this study shows that heat treatment and enzymatic hydrolysis of EBN can be tailored to achieve a certain degree of hydrolysis and physicochemical properties.