Study On Production Of Frozen Steamed Bread Doimh By Freeze-tolerant Yeast

This study takes four kinds of yeast in the market for experimentalmaterials. The freeze-tolerant yeasts for sugar-free frozen dough andlow-sugar dough were screened. By single factors experiments andresponse surface methodology to optimize the conditions of the frozendough bread process.Study the improvement of different additives on thequality of frozen dough. The results are as follows:1.The fermentation ability of4kinds of active dry yeast werestudied．As a result，There showed differences in the abilities when theseyeasts were used in fermenting low-sugar dough and plain doughFermentation ability of Y₁was the same on low-sugar dough and plaindough．The fermentation ability of Y₂、Y₅and Y₄on low-sugar doughwas higher than that onplain dough．After analyzing the relative value of fermentation abilityafter being frozen for7days in low-sugar dough and plain dough，respectively．Y₁、Y₃and Y₄have higher relative value of fermentationability in plain dough，Y₃and Y₄have higher relative value offermentation abilityin low-sugar dough．The sensory evaluation and texture profile analysisof frozen steamed bread showed that the Y₃has a better quality on frozensteamed bread．2.The fermentation ability and fermentation ability change during frozen storage of4kinds of active dry yeast were studied．As a result，thereduction of fermentation ability of Y₂and Y₄is small．During frozenstorage，the fermentation ability of different yeast were graduallylowered．Y₄has higher fermentation ability after frozen storage．Theresults of sensory evaluationand texture characteristics on frozen steamed bread with these four yeastsshowed that degradation of frozen steamed bread which contained Y₂andY₄were better than those with Y₁and Y₃．SoY₂and Y₄have a better effect on frozen steamed bread．3.The commercial active dry yeast had been treated with severalmethods．As a result，yeast treated with heat，hyper osmotic media，glycerol and trehalose show higher leavening power and freeze tolerancethan non-treated yeast after freezing.Yeast treated with hyper osmoticmedia had best leavening power and freeze tolerance, followed by treatedwith glycerol and trehalose．The leavening power and freeze tolerance byusing different active dry yeasts are different，The leavening power andfreeze tolerance of Y₂was better than those with commercial yeast，wasthe better choice in frozen dough．4.On the base of basic formula of frozen flour dough steamedbread,the factors that affected the quality of frozen flour dough steamedbread were studied．The most suitable condition of various factorsthrough single factor experiments was determined,then the ResponseSurface Method was used to optimize the optimum condition.The experimental results indicated the optimum formula of frozen flour doughsteamed bread: the thawing time1.95h， the amount of water50.8%,fermention temperature30.4℃，yeast dose1.3%.5.The effects of Vc,glycerin monostearate,carboxymethylcellulosesodium（CMC） and gluten on quality of frozen flour dough steamed breadwas studied．By single factor test and orthogonal experiment，all indexesof quality of frozen flour dough steamed bread were evaluated．Theresultsshowed that when the optimum additive amount of Vc，glycerinmonostearate,carboxymethylcellulose sodium（CMC） and gluten was0.2％，0.4％，0.09ï¼…and0.9%respectively，the index scores of theinternal and external structure of the finished bread were highest.