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The Study of Yeast Frost-resistance and Application in Frozen Dough

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Tutor: SongLianJun
School: Henan Agricultural University
Course: Of Food Science
Keywords: yeast frost-resistance,UV,diethyl sulfate mutagenesis,cryoprotectant,frozen doug
CLC: TS213.2
Type: Master's thesis
Year:  2011
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The appearing of frozen dough divided into making and baking,which grately improved production efficiency.The quality of steamed bread was closely related with workmanship,the yeast frost resisting, frozen pack storage and thawing.This experiment improved yeast frost-resistance of though UV, diethyl sulfate adding cryoprotectant .The result of researchwas as follows:(1) When UV was 30s,60s,90s and 120s, 90s, yeast frost-resistance of was most powerful.(2) The diethyl sulfate showed yeast frost-resistance was most powerful, when the additive amount of diethyl sulfate was 1%,oscillating 40 min in 150r/min .(3)After culturing 15h,the gasproductionrate of yeast was more 21.3 mL/mg than groupa,the gasproductionrate of yeast adding 5%NaCl was more16.3 mL/mg than groupa. After culturing 48h, the gasproductionrate of yeast adding 2% trehalose was more16.0 mL/mg than groupa.But inoculum adding alcohol, amylaceum, BSA and petroleum wax can not improve frost-resistance of yeast.(4)The best combination of NaCl and glycerol was 5%NaCl and 15% glycerol, the gasproductionrate was 32.8 mL/mg. The best combination of NaCl and glycerol was NaCl and trehalose, the gasproductionrate was 31.2 mL/mg. The best combination of glycerol and trehalose was 14% glycerol and 3% NaCl, the gasproductionrate was 35.0 mL/mg. According to mutual cryoprotectant response surface analysis, frost-resistance of yeast was best, the gasproductionrate of yeast was 38.1 mL/mg when glycerol additive amount was 14.57%,NaCl 4.00%,trehalose2.10%.(5)When fermentation temperature was 40¡æ,fermentation time was 120min, wake up hair time was 20min, thawing time was 30min,and frozen pack storage was one week. The quality of frozen dough steamed bread was better.Choosed frost-resistance of yeast applied in frozen dough steamed bread, frozening pack storage after a week ,its specific volume,spring and chewiness are higher than groupa. The volume made in frost-resistance of yeast is 0.96mL/g bigger than steamed bread made common yeast ,and its hardness smaller than groupa.
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