| Summary: | Native yellow pea (Pisum sativum) protein isolates (PPIs) showed good foaming and emulsifying properties but a poor gelling characteristic. However, this can be corrected by Transglutaminase (TGase) treatment. PPIs were obtained using alkaline extraction method in which extracting pH, precipitating pH, flour–to–water ratio, and extraction time were optimized to obtain maximum yields and least change in protein functionalities. Extraction pH of 10.0, precipitating pH of 4.3, flour–to–water ratio of 1:6, and 30 minute extraction time were found to be optimum values for pea protein extraction. SDS–PAGE gels showed that the PPI had a very similar protein molecular weight profile as its original flour. TGase treatment was applied on PPIs at different pH levels from 4.3 to 7.0. The SDS–PAGE and RVA tests showed that treatment at pH 6.0 provided the best overall functionality. Large molecular weight (MW) proteins (~ 90,000 Da) and medium MW proteins (~50,000 – 80,000 Da) were the main substrates for TGase catalyzed reaction whereas most low MW the proteins (< 45,000 Da) were not involved. RVA results indicated that treatments at pH 6.0 and 7.0 had the highest viscosities but the treatment at pH 6.0 had better stability and consistency. Functionality tests indicated that modified PPIs possessed a better viscosity profile than the native PPIs but no improvement in gelling capacity and only minor impact on foaming and emulsifying properties. PPIs performance greatly depended on their final pHs. The foaming capacity, foaming stability, and emulsion capacity were significantly improved when the final pH of PPIs was adjusted from 4.3 to 7.0. The overall sensory evaluation results suggested that TGase–treated PPIs and PPIs were not yet able to replace egg in the cake system. Only PPI can replace egg in the cookie system. TGase–treated samples had a lower acceptability due to an “off–taste” and a “strange” flavor. Future work, therefore, should study TGase combined with other treatments to further improve PPIs functionalities. Purification should be integrated into extraction process and other food systems should also be included to extent the scope and role of modified PPIs in food industry.
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