Effects Of Wheat Malt-derived Endoxylanase On The Quality Of Wheat Beer

Wheat is the main raw material of wheat beer.Compared with barley malt,the content of arabinoxylan in wheat is higher.The degradation product of wheat is one of the key substances affecting the viscosity,turbidity,and foam properties of wheat beer.Endo-1,4-β-Xylanase(EC 3.2.1.8)is a key enzyme in the degradation of arabinoxylan.In this paper,based on the separation and purification of wheat malt-derived endoxylanase obtained by our research group,the effects of wheat malt-derived and Bacillus-derived endo-β-1,4-xylanase on the quality of wheat beer were compared,and the differences of the degradation mechanisms of endoxylanase from two sources were revealed.The effect of the addition of purified wheat-derived endo-β-1,4-xylanase and its action time on the quality of wheat beer was investigated,and the changes in the quality of wheat beer were studied when the malt ratio was changed under the optimal addition amount and action time.The main findings of the study are as follows:(1)In the process of saccharification,Bacillus-derived endo-β-1,4-xylanase mainly degraded insoluble polysaccharide into water-soluble polysaccharide with a molecular weight of 6200～48000 Da,which increased the content of WEAX in hopped wort and beer.Wheat-derived endo-β-1,4-xylanase mainly degraded the polysaccharide with a molecular weight of 1320～48000 Da to the polysaccharide with a molecular weight of less than 1320 Da,which reduced the content of WEAX in hopped wort and wheat beer.The addition of the two enzymes can reduce the viscosity and turbidity of the hopped wort and improve the foam stability of wheat beer.Bacillus-derived endo-β-1,4-xylanase reduced the viscosity and turbidity of the hopped wort by 0.31 m Pa.s and 7.33 NTU,respectively,and increased the wheat beer foam stability by 20 s,and wheat-derived endo-β-1,4-xylanase reduced the viscosity and turbidity of the hopped wort by 0.39 m Pa.s and 11.16 NTU,respectively,and increased the wheat beer foam stability by 7 s.(2)In the process of saccharification,when the supplemental level of wheat-derived endo-β-1,4-xylanase was 0.5 to 2.5 folds of the activity of wheat-derived endo-β-1,4-xylanase,WEAX content in hopped wort decreased and total polysaccharide content increased with the increase of the supplemental level of wheat-derived endo-β-1,4-xylanase.When wheat-derived endo-β-1,4-xylanase was added at 0.5,1.0 and 1.5 folds,respectively,polysaccharides with a molecular weight of 1320～21700 Da were degraded into polysaccharides with a molecular weight less than 1320 Da,and the degradation degree of WEAX was greater than that of WUAX.On the other hand,the turbidity and viscosity of hopped wort decreased,and the foam stability of wheat beer increased.Specifically,the viscosity of hopped wort decreased by 0.14～0.17 m Pa.s,the turbidity decreased by 2.6～3.0NTU,and the foam stability of wheat beer increased by 3～4 s with each 0.5 fold increase of endoxylanase supplemental level.At the addition of 2.0 and 2.5 folds,the polysaccharide with a molecular weight of 6200～21700 Da was degraded into polysaccharide with a molecular weight less than 6200 Da,and the turbidity and viscosity were decreased and the foam stability of wheat beer was increased.There was no significant difference in the basic indexes under the two additional levels.Polysaccharides with a molecular weight of 21700～48000 Da decreased significantly in wheat beer,which may be caused by precipitation caused by excessive molecular weight of these polysaccharides.The total polysaccharide content increased when 0.5,1.0 and 1.5 folds were added,and decreased when 2.0 and 2.5 folds were added.The changes of WEAX content and basic indexes were similar to those of hopped wort.After comprehensive comparison of endoxylanase cost and each component in wort,1x endoxylanase addition amount was selected,and subsequent operation was conducted based on this.(3)When the addition of endoxylanase was doubled,the contents of WEAX and total polysaccharide in hopped wort decreased with the increase of the action time during 10～60min.The polysaccharide with a molecular weight of 1320～21700 Da was degraded into polysaccharide with a molecular weight of less than 1320 Da,the turbidity and viscosity of hopped wort decreased and the foam stability of wheat beer increased.When the action time was 40,50 and 60 min,the changes of polysaccharide content and basic indexes were little or no significant differences.The changes of polysaccharides with a molecular weight of21700～48000 Da in wheat beer were consistent with the addition amount.The total polysaccharide content increased at 10,20,and 30 min,and remained unchanged at 40,50,and 60 min.The changes of WEAX content and basic indexes were similar to those in hopped wort.Considering the cost of the beer production process,30 min was selected as the action time of endoxylanase in the subsequent operation.(4)The content of WEAX in hopped wort increased and the total polysaccharide content decreased with the increase in wheat proportion.When the wheat proportion was 40%,45%,and 50%,the content of WEAX was increased and the total polysaccharide content was decreased.The molecular weight of 6200～21700 Da polysaccharides was degraded to those with molecular weight less than 6200 Da,and the degradation degree of WEAX was greater than that of WUAX.The viscosity and turbidity of hopped wort increased,and the foam stability of wheat beer decreased.At 55% and 60%,the polysaccharide with a molecular weight greater than 48000 Da was degraded into polysaccharides with a molecular weight less than 1320～48000 Da.The total polysaccharide content in wheat beer increased,and the changes of WEAX and basic indexes were consistent with those in hopped wort.(5)Correlation analysis showed that the polysaccharide with a molecular weight of1320～21700 Da was the key polysaccharide affecting the viscosity and turbidity of hopped wort and wheat beer,and the polysaccharide with a molecular weight of 342～48000 Da was the key polysaccharide affecting the foam stability of wheat beer.