Sorghum Starch Fine Structure Affect Its Brewing Characteristics

Sorghum is one of the main brewing crops in China.The main component of sorghum is starch,and the fine structure of starch could have an important influence on its physical and chemical properties to a certain extent,also affect the brewing quality of sorghum.However,the potential mechanism of starch molecules on brewing quality is still unclear.In this study,8 commonly brewing sorghum varieties and 3 sorghum varieties fermented lees which have fermented for different time respectively were chosen as material.In the steaming process,the sorghum grains were simulated the steaming process and the leached starch parameters were correlated with sorghum grain parameters which obtain how grain starch structure affect steaming process.In the fermentation process,the difference of components and starch fine structure in lees of different sorghum varieties and different fermentation time were analyzed to figure out the influence mechanism of starch structure on fermentation.The main research contents and results are as follows:1.Effects of the fine structure and physicochemical properties of starch on the steaming characteristic of sorghumSorghum steaming properties are important for both the flavor and brewing efficiency of Baijiu.However,it is currently unclear with respects to structural factors that affect sorghum steaming properties during Baijiu production.In this study,starch fine molecular structures were characterized by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis for 8 sorghum varieties used in Baijiu production.Starch crystalline structures and the thermodynamic properties were characterized by the X-ray diffraction and differential scanning calorimetry.Results showed that only small differences were observed for the starch molecular size distributions and chain-length distributions in the raw sorghum grain.Of significance,the leached starch content and molecular size during steaming was very different among these sorghum varieties.Furthermore,Spearman correlation analysis showed that there was no significant correlation between starch fine structural parameters with the leached starch content.On the other hand,the correlation analysis showed that the leached starch molecular size was negatively correlated with the starch crystallinity,while positively correlated with the onset and peak gelatinization temperatures.It is concluded that the sorghum steaming property is controlled by the starch crystalline structures instead of starch fine molecular structures.These results could help the baijiu industry to produce baijiu with more desirable properties.2.Effects of fine structure of sorghum starch and fermentation quality of brewing methodSorghum starch is the main carbon source and the raw material of most aromatic substances in the fermentation process of Chinese Baijiu.It has a significant impact on the brewing quality of Baijiu,but it underlying mechanism has not been understood.In the study,3 sorghum varieties fermented lees were determined the components and saccharification power change between different fermentation time.The difference in molecular structure and chain length distribution of starch in lees at different fermentation time were determined by size-exclusion chromatography and fluorophore-assisted carbohydrate electrophoresis.The result showed that amylopectin molecular had higher hydrolysis and fermentation rates,but produced and accumulated more organic acid,which resulted in the inhibition of the activities of amylase and Jiuqu in the later stage of fermentation and slow down of fermentation efficiency.On the other hand,the fermentation method and recipe also affect the fermentation efficiency.The strong flavor fermentation method has a slower fermentation rate,but a higher starch utilization rate.In addition,there was no significant difference in the molecular structure of distiller grain starch at different fermentation time,which may be related to the selective hydrolysis of Jiuqu.These results can be help Baijiu produces to screen sorghum varieties and optimize production process to produce higher quality Baijiu.