Characteristics and functional properties of Persian lime (Citrus latifolia)seed protein isolate and enzymatic hydrolysates

Lime seed is one of the by-products of lime juice extraction. In this work, Persian lime seed protein was isolated (81.39 percent purity)and hydrolyzed using commercial proteases (Alcalase, Protamex, Neutrase, and mixed enzymes (1:1:1)). Though the protein isolate contained all the essential amino acids, histidine, methionine, and tryptophan were limiting. Electrophoresis analysis showed that the protein was composed of 10 protein (four major)bands. The intensity of protein bands decreased and new bands appeared after hydrolysis. Hydrolysis using the mixed enzymes gave the highest (39.19 percent)degrees of hydrolysis, followed by Alcaase (33.80 percent), Neutrase (20.05 percent), and Protamex (18.23 percent)treatments. The highest water holding capacity (5.49 g/g), oil holding capacity (5.90 g/g), emulsion stability index (ESI), and emulsifying activity index (EAI)obtained using Protamex treatment. The highest foaming capacity (FC)and foam stability (FS)were observed in the hydrolysates of Neutrase or Protamex, respectively. Solubility, ESI, and EAI of protein isolate/hydrolysates were minimum at pH 4.0 and maximum at pH 10.0 or 12.0. Protein hydrolysates showed the lowest FC and FS at pH 4.0 and the highest at pH 8.0. Overall, as compared to the protein isolate, enzymatic hydrolysates had better functional properties at a broader pH range.