Effect of freezing on the properties of potato protein gels at different pH

Abstract

This study investigated the mechanisms and variations in physicochemical properties and microstructures of potato protein gels at different pH levels under freezing conditions. Potato protein gels with a 15 % protein concentration were prepared at pH 2, pH 7, and pH 10. The results showed that at pH 7, the gel exhibited roughness, pronounced granularity, a uniform pore size distribution, and a water-holding capacity of 97.12 %. After freezing, the enthalpy was −228.13 J/g, leading to significant changes in moisture distribution and a reduction in water-holding capacity to 80.43 %. At pH 10, increased hydrogen bonding (8.58 %) and ionic bonding (2.03 %) contributed to a denser, more ordered mesh structure with an enhanced water-holding capacity (97.88 %). The enthalpy was −227.85 J/g, which minimized moisture distribution changes and preserved a high water-holding capacity after freezing. In contrast, at pH 2, the gel exhibited a coarse and non-uniform structure, with a reduced water-holding capacity of 67.55 %, increased enthalpy of −243.45 J/g, and elongated relaxation time. The freezing process led to ice crystal formation, which disrupted the protein network, particularly at lower pH levels. These findings offer a theoretical basis for optimizing potato protein gel structures and advancing the development of innovative potato-based products.