Modulating the fermented gelation behavior of pumpkin (Cucurbita moschata) seed protein isolate through ultrasound-assisted protein glutaminase deamidation.

Pumpkin (Cucurbita moschata) seed protein isolate (PSPI) is a promising plant protein, yet its fermented gel exhibits poor quality for practical applications. To overcome the limitations of PSPI and enhance its applicability in gelation systems, a synergistic strategy combining protein-glutaminase (PG) co-fermentation with ultrasound (US) pretreatment was developed for fermented pumpkin seed protein isolate (PSPFG). The results showed that compared with native PSPFG, PG co-fermentation effectively accelerated the fermentation process, shortening the fermentation endpoint time by 4 h (from 10 h to 6 h). US pretreatment induced protein unfolding and exposed more hydrophobic groups, thus enhancing gel binding strength and reducing the risk of syneresis and gel collapse. The combined treatment of US+PG significantly reduced gel particle size from 30.82 ± 2.97 μm to 8.91 ± 0.80 μm with a more uniform distribution, improved gel cohesiveness, and formed gels with enhanced water-holding capacity (WHC) by 25.54% compared with native PSPFG, thereby generating a finer fermented gel structure suitable for alternative yogurt products. LF-NMR analysis further confirmed that the synergistic treatment eliminated free water content and alleviated syneresis in the gels. Overall, the synergistic combination of ultrasonication and PG deamidation provided a reliable strategy for constructing plant protein gels with faster fermentation kinetics and higher structural stability.