Abstract
We investigated the effects on the suitability for tofu making (color and hardness) of damaged soybean (purple stained, sucked by stink bugs, black stained by two-striped soybean beetle, fed by caterpillars) and evaluated the allowable blending ratios of the damaged soybeans to whole soybean not to degrade the suitability for tofu making. A purple stained soybean did not affect the breaking stress and the taste of tofu, but affected the color (brightness and redness). If the blending ratios of a purple stained soybean to a whole soybean was less than 25%, the redness of tofu was equal to the tofu made with undamaged soybean. The tofu made with the sucked soybean and the black stained soybean were equal to the tofu made with undamaged soybean in color, breaking stress, and sensory evaluation. It is thought that incorporation of the sucked and the black stained soybean do not have much effect on the suitability for tofu making. As compared with undamaged soybean, the fed soybean showed a higher percentage of the water absorption and the solid outflow rate to the soaked liquid. The protein content and pH of the soybean milk made with the fed soybean were lower than those made with undamaged soybean. The soybean increased the breaking stress of the tofu at 0.3% of chlorination magnesium concentration and decreased it at 0.5%. If the blending ratio of the fed soybean to whole soybean was less than 10%, the suitability for tofu making was equal to the undamaged soybean.
