| This study was aimed to improve the baking quality of wheat flour and ensure its safety. Domestic wheat flour was used as the object to explore the action mechanism and effect of glucose oxidase (GOD), pentosanase and lipase, which were new type enzyme preparations. Laser Raman spectroscopy, gel filtration chromatography, thin layer chromatogram (TLC). scanning electron microscope (SEM), dynamic rheological test and texture analysis et al were introduced in this research. A new bread wheat flour improver of compound enzymes was developed as a potassium bromate replacer. The main results are as follows:1. The action mechanism and eflect of GOD on improving the baking quality of wheat flour.In the flour-water dough, the H2O2, produced by GOD acted as an active substance, which could oxidate -SH to form -S-S- and also prevent -S-S- form deoxidized. GOD also induced physical and chemical interactions between gluten protein and non-gluten protein, which resulted in a high increase of lysine content in the dry gluten. Optimal dose of GOD could enhance the microstructure of dough, improve the farinograph data, increase resistance of dough and lower the tan (delta) of dynamic rheological test, all this evolution showed strengthening effect of GOD to dough, the texture analysis revealed a negative effect of GOD to increase the aging speed of bread during storage except the high dose group(100 g/g, enzyme/14%water base wheat flour, the same to the following). The comparative study with potassium bromate suggested that GOD was a fast acted oxidant and apt to induce intense oxidation, which resulted in the negative effect to the dough by ulteriorly oxdating -S-S- to sulfo acid kind material. Sensory evaluation test of bread indicated that GOD could increase the specific volume and total quality of bread, but the effect could not compare with the potassium bromate. The study suggested that the efficiency of oxidant was not only related with the amount of chemical bonds it could affect, but also determined by its action speed and intensity. The optimal dose of GOD in this study was 20-30 g/g. GOD could not entirelyreplace potassium bromate in the experiment. Yet the study provided some basic theory for developing a compound improver to replace potassium bromate.2. The action mechanism and effect of pentosanase on improving the baking quality of wheat flour.Pentosanase could hydrolyze both the water-unextractable pentosan (WUP) and water-extractable pentosan (WEP) to lower molecular weight molecule. The WUAX, for its high water absorption, might induce negative effect to the dough, while WEAK with too low molecular weight also had worsening effect. The molecular weight of the hydrolysate was affected by the concentration of pentosanase. Only suitable dose of pentosanase could obtain the best effect. Petosanase softened the dough, lowed the resistance of dough and increase the tan (delta) of dynamic rheological test* yet it improved the microstructure of dough and showed beneficial effect to the farinograph date. The baking test showed pentosanase had a positive effect to the bread quality. Texture analysis of breadcrumbs indicated that pentosanase could prevent the bread from retrogradation. The optimal dose of pentosan in this study is 60 g/g.3. The action mechanism and effect of lipase on improving the baking quality of wheat flour.Catalyzed by lipase, endogenous triacylglycerol (TAG) of wheat flour could be modified to monoacylglycerol (MAG) and free fatty acid (FFA). The MAG fraction acted as an emulsifier in the dough to improve the dough quality. Addition of lipase could also increase the loss of carotenoid in dough and induce bleaching effect to dough. It might due to the MAG and FFA fraction, which could be substrate of endogenous lipoxygenase and bring on the oxidative effect subsequently. Suitable dose of lipase could improve the microstructure of dough, increase the resistance of dough and decrease the tan (delta) of dynamic rheological test, that confirmed the indirect oxidative effect o...
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