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Impacts of indigenous microbial communities on malt properties through commercial malting process

Cheung, H.Y.K., Lowe, C., Turlington, T.K., Levesque, C.A., Graefenhan, T., Chen, W., 2016. Impacts of indigenous microbial communities on malt properties through commercial malting process. (Win the 1st place in the Best student Poster awards). 2016 Canadian Phytopathological Society-Eastern Ontario Regional Meeting, Ottawa, November 18. Ottawa 2016/11/18 - 2016/11/18

Abstract

In order to identify opportunities for favorable microbial benefits as well as for avoiding potential brewing problems, such as premature yeast flocculation (PYF) or gushing, we applied 454 pyrosequencing on the bacterial 16S rRNA gene region and fungal internal transcribed spacer (ITS) region to recover the indigenous microbiome of steeped barley (n=30) as well as green and screened malt samples (n=30) of various quality in the crop year 2013/14. Taxonomic profiles based on high-throughput sequencing data showed that the microbial community of barley grain undergoes significant changes during the malting process. The biological selection process during the germination step decreased the community diversity through favouring a few microbes over many groups initially present on raw barley grain, even within the same microbial genus. The most prevalent microbes in malt are yeast or yeast-like fungi (e.g. Candida and Pichia) and ecologically widely distributed bacteria (e.g. Leuconostoc and Arthrobacter). A low abundance of toxigenic fungi (e.g. Fusarium) was observed in all samples. By thoroughly characterizing and source-tracking the community of beneficial and suspect microbes associated with factors affecting quality and safety of the malt end product, we may soon be able to provide science-based recommendation to the commercial malting industry.

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