小麦淀粉老化动力学及玻璃化转变温度

采用差示扫描量热法研究不同温度及储藏时间下小麦淀粉不同组分(小麦总淀粉、小麦A淀粉、小麦B淀粉)的老化动力学及最大冷冻浓缩状态下玻璃化转变温度(glass transition temperature of the maximally freezeconcentrated state,T_g’)。测定小麦淀粉各组分于-18、-5、4、22℃储藏3~21 d的老化度、T_g’及非冻结水含量。结果表明,不同淀粉组分在-18℃下储藏未发生老化,而在-5、4、22℃条件下储藏会发生老化,且4℃时的老化度最大,22℃时的老化度最小,-5℃时的老化度居两者之间;小麦B淀粉的T_g’比A淀粉的T_g’高。小麦淀粉不同组分老化动力学存在差异,小麦A淀粉的老化度较总淀粉及B淀粉大;非冻结水的含量对不同组分小麦淀粉T_g’有很大影响。

Retrogradation Kinetics and Glass Transition Temperature of Wheat Starch

The effects of storage temperature and time on the retrogradation kinetics and Tg’ (glass transition temperature of the maximally freeze-concentrated state) of different wheat starches (normal wheat starch, wheat A-starch, and wheat B-starch) were studied by differential scanning calorimetry (DSC). Fully gelatinized wheat starches were stored at ?18, ?5, 4 and 22 ℃ for 3–21 d respectively; retrogradation degree (RD), Tg’ and unfrozen water content of wheat starches were determined. The results showed that no retrogradation occurred for wheat starches stored at ?18 ℃. The RD of wheat starch stored at 4 ℃ was greater than at ?5, and 22 ℃. As indicated by DSC analysis, the Tg’ of wheat B-starch was higher than that of wheat A-starch. The results revealed that there was a significant difference in retrogradation kinetics between A- and B-starch with the former having a greater RD. The unfrozen water content had a great impact on the Tg’ of wheat starch.