Research On Fermentative Adaptability Of Several Typical Yeast Used In Wheaten Food

To discuss the adaptability and mechanism of different yeast in fermentation pasta,this study chose the high sugar type and low sugar type of four typical brands at home and abroad,namely NO.1 in Europr,NO.2 in Europr,NO.1 in China and NO.2 in China,a total of eight kinds of yeast as the research object.This paper discusses the relationship between the yeast fermenting power and the effect of yeast number of living bacterium,bacteria content of thiol,endogenous digestive enzyme activity and exogenous enzymes secretion indicators.Osmotic stress conditions are analyzed using different yeast growth trend and its relationship with trehalose accumulation in yeast.It also optimizes the best fermentation conditions of different yeast in making bread and steamed bread.The main content of the research and the results are as follows:1.Analysis of yeast proportion of living bacterium.the result shows that in low sugar type yeast,the yeast living bacterium number ranged from16.9×109cfu/g to 21.4×109cfu/g;Living bacterium rate is between 75.00% and 86.94%,higher than national standard in food processing with yeast.In high sugar type yeast,yeast living bacterium number ranged from16.8×109cfu/g to 25.3×109cfu/g;Living bacterium rate is between 80.17% and 88.22%,in line with national standards.Suitable for application in fermented products.2.Explore different yeast fermentation activity within 4 hours.The experimental results show that CO2 gas production of the low sugar type yeast is obviously increasing within 3 hours and it began to decreased after 3 hours;CO2 gas production of the high sugar type yeast is on the rise within 4 hours. Using the characteristics of different yeast fermentation,control of fermentation time,in order to get the best fermentation effect.3.Explores the growth curve of yeast in environment with different osmotic stress tolerance.The test results show that:(1) When the salt concentration is under the gradient of 1%,3%5% and 7%,low sugar and high sugar yeast on the whole presents the trend of growth inhibition;When salt concentration exceeds 3%,inhibiting effect is remarkable.(2) When the concentration of sugar is under the gradient of 2%,4%,6% and 4%,low sugar yeast growth showed a trend of increase;that is,he increase of the concentration of sugar contributes to the growth of low sugar type yeast.(3) When the concentration of sugar is within the gradient of 10%,20%,30%,20% and 30%,it is conducive to the growth of high sugar type yeast and the trend of first increase and then decrease could be found.When the sugar concentration was 10%,it is the most suitable for the growth of yeast.(4) During 8h-16 h,observed the growth trend of yeast is good,can consider to use in the process of secondary fermentation of yeast fermentation.4.Primary discussion for the permeability resistance mechanism of yeast under different osmotic stress conditions was progressed.The results showed that:(1) For different yeast,when the salt concentration is less than 3%, trehalose content increased with the increase of salt concentration;When Salt concentration is more than 3%,the quantity of trehalose decreased.The changing trend of trehalose and the growth curve of salt-tolerant yeast is consistent Analysis shows that the accumulation of intracellular trehalose may improve the salt resistance of yeast,to a certain extent.(2) Trehalose accumulation in different yeast intracellular increased with the rise of sugar content,and the changing trend is consistent with the growth curve of the resistance to sugar of sugar.Analysis shows that the accumulation of intracellular trehalose to some extent could improve the resistance to sugar of yeast.5.Explore the application of different yeast in bread and steamed bread, concluded that the best fermentation conditions.Combined with the specific volume,rough and fine porosity ratio and the correlation between sensory score.Analysis shows that when the bread volume is within the scope of 7.0 or less,sensory score values were positively correlated;Thickness porosity ratio is negatively correlated with sensory score.6.The experiment explores the secretion levels of sulphur content of yeast, endogenous digestive enzyme activity and exogenous enzymes.According to data analysis,it is concluded that:The more lipase there is,the more conducive it is to strengthen the gluten.In the yeast proteinase,the higher enzyme activity is,the less corresponding number of living bacterium there is.That is to say,the negative correlation existed between them.so in so in the actual processing applications,muste control yeast endogenous protease enzyme activity,improve the number of living bacterium,yeast in order to achieve better effect of fermentation.Yeast secretory exogenous lipase enzyme activity within the scope of the determination,there may be a positive correlation to the volume size.Low sugar yeast exogenous secreted amylase enzyme activity in 84.0890 U/dl fermentation activity is the best;High sugar living yeast fermentation,the greater the enzyme activity.Sulfhydryl content will weaken the gluten,affecting the quality of the fermented flour products.