Previous research demonstrates that barley genetics can influence beer flavor. However, the chemical basis for differences in beer flavor attributed to barley is not well defined. Here, the associations between beer volatile compounds and sensory descriptors were investigated in a controlled experiment, whereby barley genotype was the main driver of variation in the system. Beer was brewed from three advanced barley breeding lines and compared to a CDC Copeland control. Sensory studies were performed via three independent panels (a consumer, brewery, and laboratory panel). The results suggest that the four beer samples have distinct flavor profiles that could be discriminated by the three sensory panels. Volatile compounds for the four beers were characterized using HS/SPME-GC-MS; quantitation and annotation were performed using a non-targeted metabolomics approach on 397 detected compounds. The O2PLS data analysis supports that alkane/alkenes, benzenoids, amides/amines, and fatty acid esters were associated with the most desirable lager traits, compared to Maillard Reaction Products that were more abundant in the beers with "non-ideal" lager traits. Taken together, these data further support the role of barley genetics in beer flavor and provide new information on the types of volatile metabolites that can vary in controlled systems.ABBREVIATIONS: ANOVA: analysis of variance; HS/SPME-GC-MS: headspace solid-phase microextraction gas chromatography mass spectrometry; O2PLS: orthogonal partial least squares; PCA: principal component analysis.

Based on prior research that showed significant genetic differences between barley genotypes for beer sensory descriptors, the effects of degree of malt modification on these descriptors were assessed in two experiments. The first experiment involved sensory assessment of nano-beers made from micromalts of Golden Promise, Full Pint, 34 doubled haploid progeny, and the check CDC Copeland. Average degree of modification was assessed by sampling grain from each of the 37 genotypes stored for three postharvest intervals prior to malting and brewing. The second experiment involved sensory assessment of pilot beers made from intentionally under-, properly, and overmodified pilot malts of two barley varieties: Full Pint and CDC Copeland. In both experiments, genotypes were the principal sources of significant variation in sensory descriptors. Degree of modification and genotype × modification interactions were also significant for some descriptors. Based on the results of this study, the genetic characterization of and selection for barley contributions to beer flavor are warranted, even with undermodified malts. The contribution of barley variety to beer flavor will likely be modest compared with the flavors developed during the malting process and the flavors contributed by hops and yeast. However, in certain beer styles, the contributions of barley genotype may be worth the attention of maltsters, brewers, and consumers.

Heirloom barley (Hordeum vulgare L.) varieties remain interesting to maltsters and brewers for their perceived unique flavor contributions to beer, despite not meeting contemporary agronomic and malting expectations. This study utilized crosses of the heirloom Maris Otter ® and two contemporary genotypes to determine if "updated heirlooms" could be produced that would show improved agronomics and contemporary malt quality, while contributing uniquely to malt and beer sensory and chemical profiles. Using a recently established pipeline of malting; brewing; hot steep and beer sensory; and metabolomics to evaluate barley genotype contributions to malt and beer flavor, four experimental lines were compared to a control. The experimental lines were also assessed for their genomic contribution from their respective parents to further elucidate regions of the Maris Otter genome that may contribute to unique beer flavors. Results show improved agronomic outcomes relative to the heirloom parent and were comparable to the control. Malting quality met current recommendations. However, sensory properties attributable to the unique heirloom parent were not found. Further, chemical profiling did not explain the observed nuanced sensory differences, nor did it reveal unique metabolites not described by the sensory panels.

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