加热和冷却速率对大豆蛋白凝胶特性的影响

Effect of Heating and Cooling Rate on the Properties of Soybean Protein Gel

凝胶性是植物蛋白最重要的性质.采用小变形振荡（动态）流变测试研究大豆分离蛋白凝胶网络结构形成.结果表明：在加热阶段,储能模量（G’）和耗能模量（G”）都低于1Pa,G’＜G”且基本保持恒定直到达到凝胶点.Tanδ值随着加热的进行逐渐降低,然后急剧下降,冷却阶段时降至最低且保持恒定,说明形成强而稳定的凝胶网络结构.当加热和冷却速率增大时（从0.5～4℃/min）G’值逐渐下降,表明最终形成凝胶强度下降;慢的加热（冷却）速率时（0.5、1、2℃/min） tanδ较小,说明相对于快的加热速率（4℃/min）形成了更好三维网络结构的凝胶;凝胶点和加热速率有关而不受冷却速率的影响.随着蛋白质浓度的增大,其凝胶G’值增大、tanδ值减少、凝胶点下降.因此,控制加热和冷却速率可以最大限度的提高热诱导大豆蛋白的凝胶强度,而不用改变蛋白质的浓度.

Gelation is one of the most important properties for plant proteins.In this paper,gel network formation of soybean protein isolate has been studied using dynamic rheological measurements.During heating phase,the result revealed that the storage modulus（G＇） and loss modulus（G＂） were almost constant by tiny fluctuation below 1 Pa and the storage modulus was always smaller than the loss modulus until the gelling point reached.Tan delta （δ） values decreased gradually in heating phase,then followed by suddenly plunging to a very low level and remained constant at this low level of the entire cooling phase.This observation suggests that a stable gel network had formed.When both the heating and cooling rates increased（from 0.5 to 4 ℃/min）,final G＇ value decreased,which was indicative of decreased gel strength.The lower heating （cooling） rates （0.5,1 and 2 ℃/min） resulted in smaller tan （δ）.This hinted that the final product had the better three-dimensional structure compared to high heating and cooling rate （4 ℃/min）.The gelling point was dependent on heating ratewhile unaffected by cooling rate.The higher protein concentration resulted in the higher G＇.Tan δ and gelling point decreased in line with protein concentration increasing.Careful control of the heating and cooling rates enable maximum gel strength for heat-induced soybean protein gel,without having to alter the concentration of the protein.