The effect of heat and transglutaminase treatment on emulsifying and gelling properties of faba bean protein isolate

The effects of heat treatment (90 degrees C, 5 or 30 min) and enzymatic crosslinking with transglutaminase (TG, 10, 100 or 1000 nkat/g protein) on emulsifying and gelling properties of faba bean protein isolate (FPI) were studied. Heat treatment of FPI caused a clear shift in far-UV CD spectra towards random coil structure and an increase in surface hydrophobicity from 181 to 504 RFU. TG crosslinked heat-treated FPI more efficiently as compared to native FPI. TG-induced crosslinking caused a reduction of surface hydrophobicity from 504 to 435 RFU. Emulsifying activity and stability indexes of FPI stabilized emulsions ranged between 25 and 30 m(2)/g and 18-35 min, respectively. Rheological properties of the FPI gels induced by heating, followed by acidification or TG treatment (10 or 100 nkat/g protein) were analyzed. FPI showed gel-like characteristics at 10% concentration (G' = 180 Pa). When the heat-treated FPI dispersion was further acidified or TG-treated (100 nkat/g), G' values of >6500 and > 3500 Pa were achieved, respectively. Water holding capacity of the FPI gels were >93% and >98% for acid- and TG-induced gels, respectively. The gel microstructures showed mainly heterogeneously-sized protein aggregates, however, no differences were observed between acid- and TG-induced gels.