1 research outputs found
THE EFFECT OF PARTIAL PROTEOLYSIS ON TECHNO - FUNCTIONAL AND ANTIOXIDANT PROPERTIES OF MODIFIED SOY PROTEIN ISOLATES
The partial enzymatic hydrolysis is effective and safe method which can be used to improve
nutritive, techno-functional and functional properties of soy protein products. This method is
affected by numerous factors. The objective of this work was to examine the effect of partial
proteolysis on emulsifying and foaming properties of soy protein isolate. Also, the effect of
proteolysis on ABTS-radical scavenging activity and iron (III) chelating ability was followed.
Spray-dried soy protein isolate was prepared by isoelectric precipitation and modified using
three different commercial proteases, Alcalase, Flavourzyme, and Papain. Initial isolate was
hydrolyzed for 30, 60 and 90 minutes. Proteolysis was followed by the change of degree of
hydrolysis (DH) and by native-PAGE, SDS-PAGE under reducing and non-reducing
conditions. The effect of proteolysis on emulsifying properties was followed using emulsion
stability index (ESI) and emulsion activity index (EAI). Also, foaming capacity and stability of
foams formed using modified isolates were determined. Emulsifying and foaming properties
was measured at pH 3, 5 and 7. Modified isolates were characterized with different DH values
which were in the range of 11.75±0.08 (30 min, Papain) - 43.30±0.15 (Alcalase, 90 min).
Limited proteolysis differently affected emulsifying properties of soy protein isolate. All
modified isolates had improved emulsion stability at all investigated pH value whereas their
ability to form emulsion was slightly lower or equal to initial isolate but in the range of
commercial isolate used as standard. The highest stability had samples modified 30 min using
Flavourzyme (366.94±48.85 min). Contrary, limited hydrolysis improved foaming capacity,
but these foams were extremely unstable. The used enzymes differently affected the antioxidant
properties of soy isolate. Only Alcalase improved radical scavenging activity of the initial
isolate whereas the reducing power of all the investigated hydrolysates was lower than that of
the initial isolate. Alcalase and Papain improved the ability of isolate to chelate iron (II) ions,
whereas Flavourzyme-modified isolates had reduced iron (II) chelating ability. The initial IC50
of soy isolate was improved by 31.55-43.87% (Alcalase-modified) and by 21.08-60.40%
(Papain-modified)