EFFECTS of THERMAL TREATMENTS ON TEXTURE of SOY PROTEIN ISOLATE TOFU

Effects of three thermal treatments; boiling at 100C and retorting at 110 and 121C, on texture of soy protein isolate tofu were studied for a range of heating times. Retorted tofu showed a shrinkage of 18–25% of its original size and a loss of 6–12% of its original moisture. Tofu processed at high temperatures and long heating times developed higher values of texture profile parameters than tofu processed at lower temperature and shorter heating times. the thermal treatment of tofu at elevated conditions also caused an increase in sensory hardness and a decrease in moistness and overall acceptability of the tofu. the increase in texture profile values appeared to be mirrored by a decrease in protein solubility in 1% sodium dodecyl sulfate solvent and a reduction in moisture content of the tofu. the formation of disulfides linkages at elevated temperatures and during heating at 100C stabilized protein aggregates that were initially formed by hydrophobic interactions. Formation of the disulfides and shrinkage of tofu as a result of moisture loss were suggested as the major reason for decreased sensory values of thermally processed soy protein isolate tofu.