Study On The Effect Of Arabinoxylan Oxidative Cross-linking On Filterability Of Jiangsu Barley Malt

Jiangsu province is one of the major planting regions of malting barley in China. However, quality traits of barleys grown in this area are generally inferior to the imported malting barley cultivars, such as Canadian and Austrilian barley cultivars like Metcalfe and Baudin. The most severe problem encountered by Jiangsu barley cultivars is filterability. The present study revealed the correlations between the main factors of water-extractable arabinoxylans(WEAX) oxidative cross-linking and filterabilityusing pearson correlation analysis(PCA). The effect of WEAX gel wort filterability was further investigated, and several reducing agents and xylanase were added during the saccharification toreduce negative effects on filterability caused by oxidative cross-linking of WEAX chains. This study provides a new clue for filterability improvement of Jiangsu barley malt.Statistical analysis showed that there were significantly negative correlation between filtration rate and wort viscosity, peroxidase(POD) activity, AX bounded ferulic acid(AX-FA) and arabinoxylans(PAX) content in wort, with correlation coefficient of 0.521(p<0.05), 0.632(p<0.01), 0.555(p<0.05) and 0.664(p<0.01), respectively. On the contrary, PAX content in wort were positively correlated with, wort viscosity and AX-FA content, with correlation coefficient of 0.595(p<0.01) and 0.590(p<0.05), respectively.It was found that mashing with extra WEAX gel, the product of WEAX oxidative cross-linking, would significantly reduce the filterability of wort. Moreover, the negative impacts on filterability were dependent on the molecular weight of WEAX gel. The WEAX gel with molecular weight around 1770 k Da, precipitated by 80% ethanol, played major role in affecting filterability. With this part of WEAX gel added to mashing, the filtration rate of wort reduced by 63.3%, wort turbidity increased by 57%, wort viscosity increased by 6.8%. In addition, the different molecular weight of WEAX had the different ability of cross-linking reaction. The WEAX with molecular weight around 118.5 k Da, precipitated by 80% ethanol was found to be the major fraction of WEAX that participated in the crosslinking reaction. This proportion of WEAX contained 1.42 mg×g-1 of FA, indicated the existence of a large amount of covalent cross linking of AX chains.Based on the oxidative cross-linking of WEAX chains, the reducing agent VC and AX degrading enzyme xylanase were selected to add during mashing process for improving the filterability of Dan’er malt. It was found that with 0.25 g VC added, the filtration rate of Dan’er malt increased by 30%, wort turbidity reduced by 60.3%, wort viscosity decreased by 3.7%. When added with 80 U/g xylanase, the filtration rate of Dan’er malt increased by 41.9%, wort turbidity reduced by 40.9%, wort viscosity decreased by 4.1%.