The aim of this study is to investigate the effect of pH levels on functional properties of various molecular weights of eel (Monopterus sp.) protein hydrolysate (EPH). The eel was enzymatically hydrolyzed and fractionated through membranes filter (10 kDa, 5 kDa and 3 kDa). The foaming capacity and stability, emulsifying capacity and stability index, water holding capacity and fat binding capacity between pH 2 and 10 were determined. The 5 kDa EPH was found to have the highest foaming capacity at pH 2, pH 4 and pH 6, and foaming stability and emulsifying activity index at all pH levels, except pH 8 and fat binding capacity at pH 2, as compared to 10 kDa and 3 kDa EPH fractions. The 10 kDa EPH had the highest emulsifying stability index and water holding capacity at all pH levels. This study shows that the EPH fractions at low pH level had high foaming and oil binding capacity, while at neutral pH, the fractions had high foaming stability and water holding capacity. These properties are important in making whipped cream, mousse and meringue. In contrast, EPH fractions demonstrated strong emulsifying properties at high pH levels and show potential as an emulsifier for breads, biscuits and frozen desserts.
Keywords: Eel protein hydrolysate; Functional properties; Molecular weight; pH.