乳化剂对冷冻面团水分状态和玻璃化转变温度的影响

乳化剂能通过改变面团中的水分状态来改变面团的玻璃化转变温度(Tg)和低温贮藏后的微观结构。利用低场核磁共振技术(LF-NMR)研究乳化剂对面团中水分状态的影响，并利用差示扫描量热法(DSC)和扫描电子显微镜(SEM)研究乳化剂对面团的Tg和低温贮存后面团微观结构的影响。结果表明：乳化剂能不同程度地降低面团中自由水含量，当加入0.15%双乙酰酒石酸单(双)甘油酯(DATEM)时，面团中自由水含量相对空白面团减少了5.78%；乳化剂也改变了面团的Tg，空白面团的Tg为－31.3℃，当加入0.50%的单甘酯时，面团的Tg为－17.3℃，提高了14℃，而山梨醇酐单硬脂酸酯(SP60)和卵磷脂在本实验的添加量范围内，未能将面团的Tg显著提高；乳化剂能不同程度的改善低温贮藏后面团的微观结构，尤其是加入0.50%单甘酯或0.15% DATEM后，面团实现玻璃化贮存，其微观结构得到了很好的保护。

Effect of Emulsifiers on Water State and Glass Transition Temperature of Frozen Dough

Emulsifiers can affect the textural structure and glass transition temperature (Tg) of dough by changing its water state. In this study, the effect of five emulsifiers on water state in dough was by using LF-NMR. Meanwhile, DSC and SEM were used to analyze their effect on the Tg and microstructure after low-temperature storage of dough, respectively. The results showed that emulsifiers could decrease the proportion of free water in dough. The addition of 0.15% DATEM resulted in a 5.78% decrease in free water. In addition, emulsifiers also caused changes in the Tg of dough. Moreover, the Tg of dough with the addition of 0.50% glyceryli monostearici was －17.3 ℃, and revealed an increase of 14 ℃ compared with blank dough. However, the addition of SP60 or lecithin did not cause a significant increase in the Tg of dough. Furthermore, emulsifiers improved the textural structure of frozen dough to different extent. Glass-state storage of frozen dough was achieved by adding 0.50% glyceryli monostearici or 0.15% DATEM and the textural structure of frozen dough was well protected.