Study On The Effect Of Refrigerated Storage On Dough/Bread Properties And Their Improvement

Frozen dough technology often requires high costs for mechanized process, unique preservation conditions and long-time post processing, which further restrict its application. Therefore, in this paper, a new technique called refrigerated dough with fermentation which has a short production cycle was studied. The fermentation performance under different refrigerated conditions and its relationship with the changes in bread quality was discussed in our research. Furthermore, the contribution of additives to the bread quality of refrigerated dough had also been investigated. By optimizing the additive formula, the baking properties of refrigerated dough was improved.First, the effect of refrigerated temperature, time and pre-proofing time on the dough fermentation and bread quality was investigated. Results showed that the bread specific volume was the largest at the end of fermentation. Shorter time for dough to reach the optimum fermentation was observed at higher refrigerated temperature or pre-proofing values. Under the certain values of pre-proofing time and storage time, the hardness of bread crumb decreased and springiness increased for the higher refrigerated temperature. Meanwhile, under the certain frozen temperature and storage time, the hardness of baked refrigerated dough decreased and the elastic value increased for the longer pre-proofed dough. GC-MS analysis showed that the flavor components content of the baked dough pre-proofed for 30 min and refrigerated for 4 days at 2℃ after 1-day proofing was increased by 27.51%, compared with fresh bread.Second, the results of the single factor experiments regarding the different oxidizing agents, emulsifiers, hydrophilic colloid and enzyme showed that oxidizing agents, emulsifiers and enzyme could increase the specific volume of bread and improve the bread texture. Meanwhile the addition of hydrophilic colloid could minimize the influence of frozen time on the bread quality. The orthogonal experiment showed that the dough pre-proofed for 30 min and refrigerated at 2℃ for 4 days with addition of 0.4% ascorbic acid, 1.00% sucrose ester, 0.09% CSL, 0.35% CMC, 0.45% guar gum and 10 mg/kg xylanase(flour weight basis) could reach the level of traditional fresh bread. The addition of baked frozen improver increased the specific volume and sensory scores by 4.56% and 12.34%, the hardness of bread crumb decreased 32.84% compared with the control group.Finally, the results of thiol content and secondary structure analysis showed that the compound additives improved the refrigerated dough quality mainly by stabilizing the gluten network rather than yeast. Compared with the control group, the change of thiol content dough,which pre-proofed for 30 min and refrigerated for 5 days at 2℃ decreased by 15.16%, α-helix content decreased by 44.70% and random coils content decreased by 63.79%. The SEM revealed that the gluten network was disrupted in the control group, and the degree of exposed starch granules was greater than that of the group with additives.