Variation in malt metabolite chemistry and impact on malt and beer flavor
Date
2021
Authors
Bettenhausen, Harmonie M., author
Heuberger, Adam, advisor
Prenni, Jessica, committee member
Munoz-Amatrian, Maria, committee member
Sedin, Dana, committee member
Journal Title
Journal ISSN
Volume Title
Abstract
Growing and malting barley are processes that are imperative to the production of beer and distilled spirits. The rise of craft malting and brewing have provided many opportunities for the "science and art" of manipulating and bending barley to new limits to create new alternatives for the industry in terms of style and flavor. Understanding the mechanisms of how raw ingredients and their interactions influence product quality is critical for any industry. The organoleptic traits of food and beverages are highly discernable by consumers based on flavor (taste and aroma), appearance, and mouthfeel. These organoleptic attributes are variable and define style, drive consumer trends, and therefore influence the decisions regarding traits that are desirable to breed for in crops. There is a gap in the knowledge regarding how genotype, environment, and processing conditions affect the quality and flavor of beer. Understanding the sources of chemical variation among barley varieties can inform on breeding, malting, and production techniques for novel attributes of the final product. The goal of this research is to understand 1) the chemical variation in non-volatiles observed among heirloom barley malts in order to determine if they offer novel chemical traits; 2) the chemistry of malt hot steep extracts and the links between specific metabolites of the hot steep extracts and their resulting sensory attributes; and 3) the chemical and sensorial basis for differences in beer flavor attributed to experimental barley varieties under controlled conditions. Broadly, a comprehensive non-targeted metabolomics approach was utilized for all studies. Study 1: ultra-performance liquid chromatography mass spectrometry (UPLC-MS) for non-volatiles detection, chemical characterization, and multivariate statistical analyses. In Study 2: three metabolomics platforms: UPLC-MS, Gas chromatography mass spectrometry (GC-MS) for detection of volatiles, and headspace solid phase microextraction (HS/SPME) GC-MS, as well as sensory testing, and multivariate statistical analyses. Study 3: HS/SPME-GC-MS for aromatic volatiles detection, sensory analysis (including check-all-that-apply [CATA], qualitative descriptive analysis [QDA], and projective mapping/napping [PM/N]), and both univariate and multivariate statistical analyses. The results of these studies supported the role of barley genetics, environment, and processing in both quality and flavor differences and provided new information on the types of volatile and non-volatile metabolites that can vary due to these factors. Study 1: we concluded that the metabolites detected in this study (e.g. lipids, organic acids) have demonstrated effects on malt quality and flavor and have potential to contribute to novel chemistry to heirloom barley varieties. The widening of genetic diversity through breeding and introduction of the novel metabolite chemistry traits can allow maltsters and brewers access to more varieties with unique and improved traits. Study 2: the data highlight the utility of the hot steep extract to differentiate malt for flavor and chemistry and indicate specific compounds that drive the most dominant flavors observed in a population of pale malts. These research findings support the value of sensory assessments of malt hot steeps when assessing the quality of malt, defect elimination, and potential for flavor development for craft malts. Study 3: the data supported the role of barley genetics in beer flavor and provided new information on the types of volatile metabolites that can vary in controlled systems. This research could be useful in prediction of flavor based on variety, malting, and brewing analytics. Predictions regarding variation in metabolites could be useful in variety development, selection of varieties for specific beer styles, and malting or brewing protocol design.
Description
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Subject
beer
metabolomics
sensory
malt
barley
quality