糖类对南美白对虾肉玻璃化转变温度与状态图的影响

Effects of Different Saccharides on Glass Transition Temperature and State Diagram of Penaeus Vannamei Meat

为提高南美白对虾肉(PV)的贮藏稳定性,研究了蔗糖、菊糖和海藻糖对PV玻璃化转变温度(Tg)与状态图的影响。采用静态称量法研究了25℃下PV和按虾肉质量添加10%蔗糖(PV-S)、10%菊糖(PV-I)和10%海藻糖虾肉(PV-T)的吸附等温线。采用差示扫描量热法分析了PV、PV-S、PV-I与PV-T的Tg和冻结点温度(TF)。分别采用Gordon-Taylor方程和Clausias-Clapeyron方程拟合Tg与TF数据,构建了虾肉的状态图,探讨了添加糖类对PV的Tg与状态图的影响。结果表明,PV、PV-S、PV-I与PV-T的水分吸附等温线呈III型,GAB模型为描述PV、PV-S、PV-I与PV-T水分吸附特性的最适模型。PV、PV-S、PV-I与PV-T的平衡含水率随着水分活度aw的增大而增大。aw一定时,平衡含水率随着糖类添加而降低。添加糖类降低了PV的单分子层含水率。PV、PV-S、PV-I与PV-T的Tg随着含水率增加而降低。相同aw时,Tg值高低顺序依次为PV-I、PV-T、PV-S、PV。根据状态图,PV、PV-S、PV-I和PV-T的最大冷冻浓缩溶液时的玻璃化转变温度T'g分别为-71.35、-64.76、-58.36、-59.36℃,与之对应的溶质含量分别为73.2%、73.4%、72.6%、73.4%,即非冻结含水率分别为26.8%、26.6%、27.4%、26.6%。添加糖类尤其是菊糖与海藻糖能显著提高南美白对虾肉的贮藏稳定性,延长其货架期。

Effects of different saccharides, viz. sugar, inulin and trehalose on the glass transition temperature and state diagram of Penaeus vannamei meat （PV） were investigated to improve the storage stability of Penaeus vannamei meat. Moisture adsorption isotherms of PV and Penaeus vannamei meat with addition （w/w） of 10% sugar （PV - S） , 10% inulin （PV - I） and 10% trehalose （PV - T） were determined at 25℃ by using the gravimetric method. Differential scanning calorimetry was employed to determine the glass transition temperature （ Tg ） and freezing point （ TF ） of samples equilibrated at various water activities. The state diagram was composed of the glass transition line and freezing curve, which were fitted according to Gordon - Taylor model and Clausius - Clapeyron model, respectively. The results showed that the adsorption behaviour of Penaeus vannamei meat （PV, PV - S, PV - I and PV - T） displayed type Ⅲ isotherms. The GAB model statisfactory described the adsorption behavior of PV, PV - S, PV - I and PV - T. The equilibrium moisture content of PV, PV -S, PV - I and PV - T increased with increasing water activity （aw）. Moisture content of PV - S, PV - I and PV - T at a given aw was lower than that of PV. The monolayer moisture content decreased with the addition of saccharides. Tg of PV, PV - S, PV - I and PV - T decreased with increasing moisture content. Tg increased with the addition of saccharides. The state diagram yielded maximally-freeze-concentrated solutes at 73.2%,73.4%, 72.6% and 73.4% solids with the characteristic temperature of glass transition being -71.35℃, -64.76℃ -58.36℃ and -59. 36℃ for PV, PV-S, PV-I and PV-T, respectively The corresponding un-freezable waters for PV, PV - S, PV - I and PV - T were 26.8% , 26.6% , 27.4% and 26.6% , respectively. The storage stability and shelf life of meat can be markedly improved by addition of saccharides especially inulin and trehalose.