POD promoted oxidative gelation of water-extractable arabinoxylan through ferulic acid dimers. Evidence for its negative effect on malt filterability

Abstract

As a major component of non-starch polysaccharide in barley, arabinoxylan (AX) plays an important role in quality traits of malt and the final beer product. The Chinese barley malt has encountered filterability problems for a long time. The main reason caused by barley cultivar has been accepted in the malting and brewing industries. In our previous proteomic study, the peroxidase (POD) BP1 was found to be in quite high abundant in the filterability defect Chinese barley malt. Therefore, the present study tried to verify its negative effect on filterability, by surveying its activity in different malt samples and detecting effects of POD on AX gelation and filterability. The results showed that the activity of POD, as well as the content of AX bounded ferulic acid, were both negatively correlated with filterability, while the feruloyl esterase activity was positively correlated with it. In addition, AX gelation catalyzed by POD caused worse filterability, and the natural inhibitor of POD, vitamin C, could blocked the cross linking catalyzed by POD and thus improve the filterability. These results all suggested the great negative effect of POD on malt filterability.

Keywords: Arabinoxylan; Ferulic acid; Filterability; Malt; Peroxidase.