Abstract:

Pea protein isolate (PPI) with or without structural unfolding (by heating or pH12 treatment) was hydrolyzed by
using seven proteases (3 crude proteases: alcalase, flavourzyme and protamex; 4 pure proteases: trypsin, chymotrypsin, papain
and pepsin) to produce pea protein hydrolysates (PPHs). The degree of hydrolysis, protein solubility and antioxidant activity
were evaluated. Results showed that both heating and pH12 treatments could promote protein hydrolysis, but produce obvious
changes in solubility, depending on enzymes. All PPHs exhibited stronger (P ＜ 0.05) scavenging activity against ABTS+• and
•OH free radicals than PPI, and both heating and pH12 treatments of PPI enhanced the antioxidant activity of the hydrolysates.
PPHs prepared by crude enzymes were stronger Fe2+-chelating capacity than PPHs prepared by pure enzymes. Among all PPHs,
the PPH prepared by flavourzyme (Fla-PPH) and protamex (Pro-PPH) revealed the most obvious inhibition on lipid oxidation
in the liposomal system. Fla-PPH prepared from heating or pH12-treated PPIs showed better inhibition on lipid oxidation in
the Tween-20-stabilized oil-in-water emulsion than Fla-PPH prepared from non-treated PPIs. Overall, PPHs from heating and
pH12-treated PPIs generally has stronger antioxidant activity than those from native PPIs.

Key words: pea protein isolate, heating and alkaline treatment, enzymatic hydrolysis, antioxidant activity