Effect of compound quality improver on the frozen quality of frozen dough for steamed bread

Abstract: Steamed bread is a traditional fermented pasta product in China, which plays an important role in the dietary structure. With the improvement of people's living standards and the acceleration of life pace in recent years, steamed bread has become a popular fast food product for consumer. However, the shelf life of steamed bread is short and easy to be aged, which greatly affects the industrialized production of steamed bread. Frozen dough technology can provide an economic and effective technical way. However, the relevant research reports pointed out that the water in the dough formed ice crystals in the process of frozen storage. Because of the temperature fluctuation, recrystallization will occur, which will destroy the network structure of the dough, make the dough appear cracks after freezing, reduce the gas holding capacity, as well as affect the quality of frozen dough and its cooked products. At the same time, ice crystal will also lead to the damage and rupture of yeast cells, such as the damage of its respiratory system, the reduction of yeast vitality and the lack of gas production, which will cause the decline of dough specific volume, texture and sensory quality. The use of dough quality improver can enhance the structure of gluten network, protect yeast activity, improve the quality of dough, and prolong the storage period of frozen dough. To study the effect of different improvers on the quality of frozen dough and its cooked products, and to select the compound improvers which can improve the quality of the products better, it has a certain practical significance in the actual production. In order to improve the quality of frozen dough and to clarify the effect of different food improvers on the quality of unwrapped frozen dough, this paper studied compound thickeners (carrageenan, guar gum, sodium alginate) and compound emulsifier (diacetyl tartrate monoglyceride, carboxymethyl cellulose), complex enzyme preparations (glutamine transaminase, glucose oxidase) and trehalose on the quality of unwrapped frozen dough steamed bread, through single factor and response surface experimental design, the effect of different compound quality improver on the specific volume, texture and sensory quality of frozen dough. Studies have shown that the effect of trehalose and enzyme preparation on the specific volume of frozen dough is extremely significant (P<0.01). Under the compounding process of adding 0.4 % emulsifier, 0.8 % thickener, 45 mg/kg enzyme preparation and 2 % trehalose, the specific volume of the frozen dough steamed bread reached the level of 3.15 mL/g, and its hardness and the springiness also reached a superior value of 926.832 g and 0.912 8, respectively. At the same time, the frozen dough which was not added and added with the compound quality improver for 0-2.5 month was observed by scanning electron microscopy. It was found that most of the small starch granules in the frozen dough without the addition of the modifier were exposed outside, the particles were distinct, and the internal structure was uneven. The frozen dough starch granules with the compound quality improver added in the gluten network, the protein network structure is clear and complete, the internal structure of the frozen dough is even and tight.