Effects of Eggshell Powder as a Coagulant on Gel Properties and Texture Structure of Citric-Acidified Tofu Gel

It has been shown that citric acid-induced tofu has problems of soft texture and fragility. The aim of this study is to improve these problems by adding eggshell powder as a coagulant. Commercial tofu (gypsum tofu) was used as a control group. The properties of the gels were analyzed using intermolecular forces, rheology, and scanning electron microscope (SEM). The least surface hydrophobicity and free sulfhydryl groups were observed at 0.08% eggshell powder concentration. The rheological behavior indicated a solid elastic dominant behavior of tofu. Additionally, ionic, hydrogen and hydrophobic interactions increased accordingly. With the optimal addition of eggshell powder (0.08%), the alpha-helices structure of soybean protein transformed into a beta-sheet structure, resulting in a redshift and enhanced peak intensity. The network of the tofu gel has become denser. These findings suggest that eggshell powder can be used as a natural calcium supplement to enhance the performance of tofu.