Improving the techno-functionality of air-classified pea flour fine fraction by enzymatic proteolysis, followed by Maillard-induced conjugation with available carbohydrates in the flour

Abstract

Background and Objectives: Air-classified pea protein-enriched flour (PPEF) was hydrolyzed with trypsin and papain and heat conjugated with the carbohydrate fraction of the flour via the Maillard reaction to form protein–carbohydrate conjugates. The surface and functional properties of the conjugates were assessed thereafter. Findings: The surface charge of the conjugates (trypsin and papain conjugates) (−27.5 to −32.2 mV and −33.1 to −37.5 mV) was higher than that of PPEF (−24.2 ± 0.5 mV and −27.3 ± 1.1 mV) at pH 7 and 10. Low degrees of trypsin hydrolysis, followed by conjugation resulted in enhanced foam capacity (109.2% ± 2.0%), and heated trypsin controls had the highest foam stability (76.9%) at pH 4. The emulsion activity index of the hydrolyzed protein–carbohydrate conjugates (hydrolyzed proteins conjugated with starch) was higher at pH 4 (15.9–22.2 min) as compared to pH 7 (16.5–21.3 min). Trypsin conjugates showed the highest emulsion stability (ES) at pH 4 (96.4%–98%), whereas the ES at pH 7 and 10 was almost comparable. Both oil-holding (OHC: 1.9–3.9 g/g) and water-holding capacities (WHC: 1.7–2.4 g/g) were significantly improved. Conclusions: Maillard conjugated proteins have enhanced functional properties at pH 4, 7, and 10 as compared to PPEF. Most of the conjugates show high functionality at pH 4. It was also observed that only heating the low-cost, raw materials produced conjugates with enhanced functional properties. Significance and Novelty: Enhanced functional properties at acidic pH are indicative of their use in beverage emulsions like fruit juices and processed drinks. High WHC and OHC show their potential use in the food industry as an alternative to animal proteins.