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Abstract
The quality of bread made from frozen dough is diminished by changes that occur during the freezing process. The effects of processing conditions and levels of waxy wheat flour (WWF) and water on the quality of frozen dough and bread were investigated. As for processing condition effect, Yeasted bread dough was frozen using four freezing rates, then stored at -10, -20, -30, or -35C for 30, 60, 90, and 180 days. The properties of the resulting yeasted frozen doughs were measured using nuclear magnetic resonance techniques (NMR), cryo-scanning electron microscopy (SEM), and texture analysis. Specifically, bread staling, a physical property of the bread, was measured using NMR, texture analysis and color analysis. The yeast activity of dough was assessed by measurements of gas production. Our results indicate that dough strength diminishes with time as well as with increasing storage temperature. Cryo-SEM demonstrated that frozen dough stored at -30 and -35C displayed the least damage to dough structure. NMR studies showed that frozen dough at lower storage temperatures had lower T2 values (9-10 ms). However, dough stored at higher temperatures displayed higher yeast activity. Baking tests showed that the loaf volume and weight gradually decreased with storage time, and that bread made from dough stored at -20C resulted in the highest loaf volume. Breads made from dough stored at -30 and -35C displayed less change in the texture profile during storage as well as less change in T2 values. As for WWF, the quality of dough and bread quality was investigated. Stickiness of dough increased with higher content of WWF. Dough with higher content of WWF and 60% level of water added were more extensible. NMR studies showed that frozen dough with higher WWF content had lower T2 values (9-10 ms). Bread made from 15% and 30% WWF had higher specific volume. The results of T2 value change ratio and firmness showed that bread with higher WWF content had slower rates of staling. Bread made from the combination of 15% or 30% waxy wheat flour and 60% water content had more even distribution of color and higher volume of bread.