The Barley Malting Microbiome: Influence on Malt Quality, Control and Characterization Methods

The conversion of raw grains to malt is a pivotal step in the beer production process. By germination, the grains produce enzymes necessary for the conversion of starch into sugars during the mashing process, but also cell wall constituents are broken down which aids in wort filtration. Further, storage proteins are converted into soluble peptides and amino acids important for yeast nutrition during fermentation. However, the performance of the malting process and the quality of malt produced is also significantly influenced by the active microbial communities that naturally colonise the barley grains. These diverse microbial communities have the potential to produce extracellular enzymes, phytohormones, mycotoxins, and exopolysaccharides, and also compete with the grains for oxygen. While microbes can contribute positively to the break-down of cell wall β-glucans and arabinoxylans, they can also negatively impact the final malt quality by production of gushing precursors, compounds leading to premature yeast flocculation (PYF) and mycotoxins. This review provides an overview of the current knowledge on the different microbial communities interacting with the barley grain on the field and during malt production, their influence on the quality of produced malt, and the brewing process. Further, current strategies to control the proliferation of detrimental microbial species during malting are presented, including a summary on recent techniques to identify, quantify and functionally characterise the barley malting microbiome.

Publication year:2024

Accessibility:Closed