Study On Processing Technic Of Wheat Corn Steamed Bread

This paper mainly studied the problems exists widely in the wheat corn steamed bread market about less additive amount of corn flour and rough texture, process improvement, flour blending and other improvement researchs were carried out to improving the additive amount of corn flour and the quality of the wheat corn steamed bread, then developed a wheat corn steamed bread which meeting the needs of both flavor and nutrition.Mixing flour of corn flour and wheat flour were as raw material, the influence of processing conditions(mixing time, fermentation time, proving time)on the wheat corn mixed dough extensibility and steamed bread quality was studied. What’s more, the relationship of extensibility test data obtained by textural analyzer with the quality of steamed bread was analyzed in this paper, and the application of texture analyzer on quality control in the production process of wheat corn steamed bread was explored. The results showed significant correlations between dough extensibility(force at the extension limit points, distance at the extension limit points) and steamed bread quality, which could be used for process quality control. The optimal conditions were as following:mixing time at 10 min, fermentation time at 80 min, proving time at 20 min.The effects of corn flour addition, water addition, corn particle size on the wheat corn mixed dough extensibility and steamed bread quality were investigated. Response surface methodology(RSM) was used to optimize process conditions to improve the sensory score. The optimal conditions were as following:corn flour addition at 27.6%, water addition at 51.72%, and corn particle size at 80 meshes.The effect of the extrusion pretreatment on corn flour properties was studied. The results showed that extruded corn flour has bigger water absorption, higher viscosity and better dough properties than ordinary corn flour. However, the steamed bread made of extruded corn flour has larger hardness, smaller specific volume and lower sensory score than the steamed bread made of ordinary corn flour.(1) The study of quality improver for steamed bread showed that gluten could significantly increase water absorption, development time, stabilization time. Within a certain range, with the increase of gluten content, mixed flour steamed bread hardness decreases, spring and sensory score increase gradually. When gluten content exceeds 6%, steamed bread quality will decline. (2) Mixing flour of corn flour and wheat flour as raw material,4 kinds of hydrocolloids, xanthan gum, guar gum, carboxymethyl cellulose sodium and konjac gum were added with different dosage,0.5%,1%,1.5%and 2%, to the mixed flour, respectively, the effects of hydrocolloids on farinograph properties of mixed flour and steamed bread quality characteristics, such as water absorption, development time, stabilization time, softening, specific volume, hardness, springiness and sensory evaluation were studied. The results showed that mixed flour added with hydrocolloids had higher water absorption, longer development time, longer stabilization time, and lower softening degree. Whereas different hydrocolloid types, different influence degree. Although the effect of xanthan gum on farinograph properties was the most remarkable, but the wheat corn steamed bread with it was of inferior quality. The qualities of wheat corn steamed bread, to some extent, were improved by adding a moderate amount of guar gum, sodium carboxymethyl cellulose or konjac glucomannan, specific volume maximum with 2% konjac glucomannan, hardness minimum with 0.5% konjac glucomannan, and sensory quality score the highest with 2%sodium carboxymethyl cellulose. (3)Monoglyceride(0.5%), refined lard(3%) and granulesten(1%) could improve development time and ductility of mixed flour, reduced hardness of wheat corn steamed bread and improve the specific volume and the sensory quality of steamed bread.Taking hardness of wheat corn steamed bread as test index, the application of additives in the steamed bread anti-aging is studied. The results showed that addition of monoglyceride, granulesten, refined lard, xanthan gum, guar gum, CMC and konjac gum had an effect on decreasing the ultimate hardness value and the extent of firming, which can retard retrogradation of amylopectin during strage。Scanning electron microscopy experiments confirmed that quality improver has improved the quality of both mixed flour dough and steamed bread from the microscopic view. The results showed that additives improve the gluten network structure of mixed flour dough, delay the hardening of the steamed bread and prolong the shelf life of the products.