Influence Of Thermal History To Quality Of Steamed Bread

Steamed bread is one of the most favourited staple foods in china. With the standard of living of people and the acceleration of the pace of life, frozen steamed bread has become a staple of supermarket selling varieties. Frozen steamed bread generally through heating, cooling, quick freezing and frozen storage and re-heating processes to be eaten. During the thermal history heating-cooling (freezing)-reheating, such as microwave and steam heat recovery methods will affect the texture of steamed bread and digestive absorption. However, not yet studies related. Sensory properties of steamed bread that were cooked and reheated by steam and microwave were evaluated. Their physicochemical properties and digestibility were also studied. The temperature-time curve of steamed bread in cooking and the reheating processes was examined and a modified model was used for indicate the temperature-time relationship of reheating the steamed bread. The results were as follows:1. Studied the amount of water, proofing time, microwave power and treatment time on the microwave steaming quality of steamed bread. Amount of water, proofing time, microwave power and microwave treatment time on the microwave steaming bread quality was significantly affected, increasing the amount of water, proper control of proofing time, microwave power and processing time, helping improve the microwave steaming steamed bread quality. The appropriate process for steamed bread cooked by microwave heating were determined by orthogonal tests:50% water added to the flour, then knead dough, shaping and ferment for 30min,420w microwave heat for 2.5 min.2、Compared with steam and microwave steaming steamed bread quality differences. Steamed bread quality and digestion methods on which there was any significant effect. When using steam steamed steaming center temperature reached 100℃need 14min, but only when the microwave steaming 100s. When microwave steam buns, with short production cycles, better flavor and chewiness, starch digestion of high, but its surface color, shape and internal structure, elastic geometric difference between steam steaming bread. Simulate human gastric digestion bread 4h, microwave steaming fresh bread starch digestibility 88.58%, significantly higher than the steam steaming bread (82.92%).3. Studied microwave steaming buns and steamed bread in the steam quality changes during storage. At 25℃,4℃and stored under -10℃72h, microwave steaming bread in the water content decreased by 10.83%,5.69%,4.74%, while the moisture content of steam steaming bread decreased by 8.40%,6.36%,6.05%; microwave steaming bread starch digestibility by the 88.58% down to 60.57%,56.87%,63.85%, protein digestibility decreased from the 83.74% to 68.91%,65.91%,69.92%, while the steam steaming bread starch digestibility dropped to 82.91 percent from the 60.87%,57.67%,64.07%, protein digestibility decreased from the 84.12% to 72.66%,67.61%,63.66%; microwave steaming buns and steam steaming bread during storage iodine blue value decreased, paste re-polymerization of starch crystallization, and with the storage time increased crystallinity, making bread hardness, flexibility decreases, sensory quality became inferior., The fastest decline in the quality of storage of bread at 4℃, that can slow the deterioration of the quality of steamed bread storage at -10℃. After storage, microwave steaming bread sensory quality, texture, peptic were worse than the steam buns.4. Studied the frozen bread steam heated by microwave and its texture and digestibility changes. When using heat recovery steam temperature reaches 100℃steamed center time (11-12min) far longer than the microwave heat recovery (only 75s), Microwave Reheating fast. Steam after reheating frozen bread increased by 2.14% water content, natural thaw and microwave reheating, the water content decreased by 1.91%, 4.28%; after reheating, iodine blue values are lower. Fresh bread, natural bread thaw, heat recovery steam and microwave reheating steamed bread starch digestibility of 88.58%, 75.44%,78.44% and 87.57%, protein digestibility were 83.74%,71.43%,73.74% and 76.55%. Heat recovery can improve the texture of frozen bread, flexibility, and the digestion of starch and protein, and microwave reheating on the bread to improve the flexibility and the role of peptic complex than steam heat.