Water dynamics in microwavable par-baked soy dough evaluated during frozen storage

Par-baked bread provides convenience and quality in bakery products. Soy, in combination with its nutritional benefits, was previously shown to improve the texture of microwave-baked flatbread and par-baked flatbread due to the high hygroscopic properties of soy protein and the plasticizing effects of the added lipids. It was hypothesized that soy addition would also mitigate the changes in texture and the properties of water within par-baked flatbread during frozen storage. Flatbread was formulated with 0, 10, 20, and 26% soy ingredients (by weight of added ingredients). The dough was (partially) baked to about 75% of completion and then stored at − 18 °C for 14 days. The dough was then thawed and analyzed for moisture content, textural properties such as hardness, and proton T1 and T2 relaxation times. Freezing increased the hardness and chewiness and decreased the springiness of par-baked wheat bread, but 10% soy bread did not show a change in chewiness, hardness, or springiness upon freezing. Two distinct water populations, in an approximate 90%–10% proportion, were defined using solution state proton NMR relaxation techniques. Increasing soy concentrations led to decreased T1 relaxation values in the most populated water state. Data suggest that the water in this par-baked system is a non-rigid solid, and that soy addition therefore increases mobility of the water. Neither T1 nor T2 relaxation values changed during frozen storage time for any of the formulations. These results indicate that soy slightly altered the texture and water properties of par-baked flatbread but these formulations were more stable during frozen storage.

► Soy par-baked flat bread withstood frozen storage better than the wheat counterpart. ► T1 and T2 relaxation data suggest that water is in a non-rigid, solid state. ► Bread with 10% soy maintained textural properties after 2 wks of frozen storage.