Structural modification of mung bean protein isolate via heat–pH shifting and limited enzymatic hydrolysis: Enhancing gelation of additive-free yogurt

Legume protein–based yogurts formulated without added fat or stabilizers typically exhibit poor gelation capacity and are prone to phase separation. To overcome this limitation and extend the applicability of pH-shifting in yogurt systems, a synergistic modification strategy for mung bean protein isolate (MBPI) was developed by integrating heat–alkali treatment (pH 10.5, 50 °C) with limited proteolysis using papain or bromelain. SDS–PAGE analysis showed that papain induced controlled hydrolysis while largely preserving the medium-molecular-weight protein fractions. Compared with native MBPI (solubility: 23.7 %), MBPI subjected to pH-shifting combined with papain treatment exhibited a pronounced increase in solubility (75.5 %) and formed gels with enhanced water-holding capacity (WHC, 78.6 %) and improved viscoelastic properties (G′/G″). The combined treatment slightly reduced gel hardness due to particle size reduction, resulting in a finer gel structure suitable for yogurt products. LF-NMR analysis further confirmed a more restricted water distribution within the modified gels, indicating the formation of a stable and cohesive gel network. Overall, these findings demonstrate an effective approach for alleviating textural limitations in plant-based yogurts and support the development of high-quality, clean-label fermented products.