Water soaking temperature of kenaf ( Hibiscus cannabinus L.) seed, coagulant types, and their concentrations affected the production of kenaf‐based tofu

Abstract

The effects of soaking temperature of kenaf seed on the proximate, phytic acid, and microstructure were studied to produce kenaf-based tofu. The seeds were soaked at temperatures 65°C, 45°C, and 25°C for 160, 300, and 616 min, respectively. The soaked seeds were used to produce tofu based on the Box–Behnken design with three independent variables (coagulant types (x1), coagulant concentrations (x2), and soaking temperature of seed (x3). Soaking significantly increased the carbohydrate and reduced the ash content without a significant effect on the phytic acid of the seeds. An increase in the soaking temperature of seed significantly decreased the yield, hardness, and chewiness of the tofu. Two-way interactions of (x1x2) and (x1x3 and x2x3) significantly affected the yield and the hardness of the tofu, respectively. There was a 75.91%–100% reduction in the phytic acid of the tofu. Hydrogen and hydrophobic interactions were the major bonds that stabilized the coagulation process of the tofu. Practical applications Kenaf seed contains a high amount of protein and it could serve as a suitable seed for tofu production. In general, processing factors are an important concern in tofu making. Soaking is a crucial step in the production of tofu which is often time-consuming. Soaking of seeds at higher temperature is known to practically reduce the time of soaking and overall processing time. Different types and concentrations of coagulants will give different effects on the characteristics of the tofu. The results showed that the soaking temperature of kenaf seed, coagulant types, and concentrations used in the tofu preparation affected the textural characteristics of the product. Hardness and chewiness of the tofu were significantly decreased as the soaking temperature of the seed was increased. The findings of this research will serve as the primary knowledge to produce tofu from kenaf seed. Application of suitable kenaf seed soaking conditions and appropriate concentration and type of coagulant will be useful for the tofu manufacturers to produce kenaf-based tofu with desirable qualities.