Quality and Flavor
“Omics Analysis of Malt from Heirloom Barley: The Potential for New Traits and New Flavors from an Old World”
Poster presentation at upcoming ASBC conference in SanDiego this August
Presented by CSU PhD candidate Harmonie Bettenhausen
In the brewing industry, identifying superior ingredients that provide distinct flavors is an important area of research. Craft brewers have supported the notion that older “heirloom” varieties of barley (Hordeum vulgare) provide unique attributes that improve the brewing process and flavors of the beer. While the contribution of raw ingredients such as yeast and hops to flavor is well understood, it is currently unclear how different genotypes of barley provide unique flavor to beer. Malt type is understood to impact beer flavor, but not regarding the variety of barley variety to beer flavor and flavor stability. In brewing, barley is malted to provide saccharides and enzymes for fermentation, however the malt also contains thousands of metabolites that may influence flavor. Here, we characterized metabolite variation in a collection of heirloom varieties and more current varieties gathered from various sources by the Montana State University Barley Breeding Program. The goals of this study are to determine (i) chemical profile and metabolite differences among 160 heirloom barley genotypes, (ii) which differences in barley chemistry are reflected in the chemistry of the beer, (iii) if the differences in the beer chemistry impact sensory attributes of beer, through flavor and flavor stability, and (iv) if there are barley and/or malt metabolites that can be markers for beer flavor and/or flavor stability for future breeding into lines adapted to dryland farming. A total of 173 varieties plus five checks replicated seven times were grown with an augmented Randomized Complete Block Design (RCBD) in both rain-fed and irrigated environments. All barley genotypes including checks were initially micro-malted as 5g samples to pale malt specifications and evaluated for variation in malting quality. Lines with adequate malt quality were then micro-malted in 100g samples. Barley and malt were evaluated for variation in small molecules, metals, and proteins that are associated with malting quality, flavor, and flavor stability. The barley and malt were evaluated using mass spectrometry-based proteomics (LC-MS/MS). Metabolomics platforms were used to characterize chemical variation among the barley and malt using UPLC-MS (non-volatile metabolites), HS/SPME-GC-MS (volatiles), and ICP-MS (metals). A subset of the malt was evaluated using the ASBC Hot Steep Sensory method, evaluated by a trained sensory panel, and the subsequent hot steep extract was evaluated on metabolomics platforms (UPLC-MS and HS/SPME-GC-MS). The chemical profiles of the barley and malt were evaluated for metabolite variation using principal component analysis (PCA), analysis of variance (ANOVA), and orthogonal two-way partial least squares (O2PLS). The statistical analyses revealed significant variation in the chemical content of the barley grain and malt. Further, several metabolites were found to be associated with the final chemical content of the beer. Taken together, these data support a potential role for heirloom varieties to provide distinct attributes to the brewing process, given the relation of the chemical composition and differences within, to beer flavor and flavor stability.