Starch Fine Molecular Structures As A Significant Controller Of The Malting, Mashing, And Fermentation Performance During Beer Production

Background: Starch, as the most abundant component in barley grains, its importance for beer quality is, however, often overlooked. Starch undergoes sequential modifications during the malting, mashing and fermentation process of beer production, which ultimately provides fermentable sugars (FS) for yeast fermentation and determines the beer quality (e.g., sensory attributes, nutritional properties, etc) by forming un-fermentable dextrins.Scope and approach: This review systematically describes the alteration of starch molecular structures during barley malting, mashing and fermentation processes and its relations with beer sensory properties. It is aimed to identify mechanisms and desirable starch molecular structures accounting for desirable brewing qualities.Key findings and conclusions: Starch molecular structure, characterized as chain-length distributions (CLD) and whole molecular size distributions (MSD) could significantly affect malts brewing performances by (1) determining the gelatinization/viscosity characteristics of malt flour and by (2) affecting starch-amylolytic enzyme interactions and thereby altering both the content and functional properties of starch hydrolysate after mashing. Except for FS, as malt starch hydrolysis also produces a large amount of non-fermentable dextrins, either branched or debranched, that would significantly impact yeast fermentation efficiency, resulting to different beer sensory proceptions (e.g., ethanol concentration, variances of aromatic components of beer, etc). In the meantime, dextrin molecules that escape from the brewing processes and remaining in beer could also directly influence the perceived impression of beer palate fullness, functional properties and the effects varied with different molar mass. The information summarized in this review provides a molecular tool for brewers to select better raw barley grains for beer production with improved qualities.