Cryoprotective effect and mechanism of γ-polyglutamic acid with different molecular weight on surimi

• Exploring the antifreeze effect of poly- γ -glutamic acid ( γ -PGA). • 2, γ -PGA reduces myofibrillar protein degradation and oxidation during refrigeration. • 3,Low molecular weight γ -PGA has better antifreeze effect. • 4,SH content, carbonyl content and Ca 2+ - ATPase activity reflect the antifreeze effect of γ -PGA. γ -Polyglutamic acid ( γ -PGA), a significant component of traditional food (natto), is produced industrially through microbial fermentation from Bacillus subtilis. It has been extensively studied for its diverse effects, such as facilitating weight loss, reducing salt content, and enhancing calcium absorption. Additionally, γ -PGA also demonstrates antifreeze properties, which necessitates further exploration of its underlying mechanism. This study comprehensively examines, for the first time, the impact of γ -PGA with varying molecular weights (20∼2,000 kDa) on the freeze-thaw stability of tilapia surimi. The findings highlight the significant role of γ -PGA in mitigating the deterioration of surimi quality, resulting in enhanced stability of myofibrillar proteins, improved gel properties, and upregulation of essential proteins. Analysis reveals a correlation between the antifreeze effect and the molecular weight of γ -PGA, with the 20 kDa variant demonstrating superior performance compared to commercial antifreezes. Mechanistic investigations uncover the ability of γ -PGA to effectively hinder the growth and recrystallization of ice crystals, while also strengthening the gel and texture properties through hydrogen bonding among surimi proteins. Furthermore, γ -PGA stands out for its low-calorie profile and lack of unpleasant taste, distinguishing it from conventional commercial antifreezes such as sugars or polyphosphates. These results emphasize the promising potential of γ -PGA in the food industry as an environmentally friendly and highly appealing green antifreeze.