Hydrolysis of peanut (Arachis hypogea L) protein concentrate by fungal crude protease extract: effect on structural, functional and in-vitro protein digestibility

Peanut protein concentrates (PPCs) were subjected to hydrolysis by crude protease extract (CPE) obtained from three fungi viz; Rhizopus oligosporus, Trichoderma reesei, and Aspergillus oryzae and the effect on structural, functional and in-vitro protein digestibility (IVPD) properties were studied. Particle size was found significantly (p <= 0.05) lower in hydrolyzed samples than un-treated samples. Fourier transform infrared spectroscopy (FTIR) spectrum of hydrolyzed samples displayed intense absorbance peaks in the wavelength ranging from 1500 to 2600 cm(-1). Peanut protein concentrates hydrolyzed by CPE from R. oligosporus showed higher surface hydrophobicity (564.18). Total sulfhydryl content was found lower in all the hydrolyzed samples whereas, reverse trend was observed for exposed sulfhydryl content. The structural changes simultaneously affected the functional and IVPD attributes of hydrolyzed PPCs. In comparison to the PPCs hydrolysed using crude extracts from T. reesei and R. oligosporus, PPCs hydrolysed by A, oryzae showed higher solubility, water and oil binding capacity, foaming capacity and foam stability. Higher IVPD values of 86.70% was also found in PPCs hydrolyzed with CPE of A. oryzae. The study established that CPE hydrolysis of PPCs has potential for scale-up studies and may serve as a cost effective alternative to protein hydrolysis with pure enzymes.