Impact of variety and environmental factors on proteolytic quality parameters of selected malting barley varieties

BACKGROUND: Barley (Hordeum vulgare) is a major cereal crop, essential for global food processing and brewing. Malting barley represents less than one-fifth of global barley output due to strict quality requirements, such as total protein content, enzymatic activity, and kernel homogeneity, which directly influence malting performance and, consequently, beer quality. Despite enormous progress in breeding for agronomic performance and grain quality, increasing climate variability poses significant challenges to malting barley production, affecting both yield and quality. An understanding of the ways in which environmental and genotypic factors influence protein composition is critical to ensure consistent malt quality. This study analyzed malt quality data from 7458 malt batches representing six commercial malting barley varieties harvested between 2017 and 2024 across three European regions to quantify, evaluate, and contextualize the effects of environmental and genotypic factors on key proteolytic quality parameters, including total protein content, soluble nitrogen (SN), free amino nitrogen (FAN), and the Kolbach index (KI). RESULTS: Proteolytic parameters (PPs) followed a sequential cascade from total protein to SN and FAN. Total protein varied mainly among harvest year × variety combinations, whereas SN and FAN showed pronounced temporal declines, particularly during 2021-2024. Varieties 1 and 5 combined high SN with high FAN, whereas variety 3 consistently showed the lowest values. Variety 6 displayed the highest FAN despite intermediate SN, indicating genotype-specific proteolytic efficiency. The KI showed low variability and confirmed classification into high- and moderate modification groups. Regional effects were minor. CONCLUSION: The decline in SN and FAN in more recent years, despite variable protein levels, indicates that protein quality is a more important determinant of malt performance than total protein quantity alone. This cascade-oriented perspective provides a clearer interpretation of quality variation in malting barley and supports more informed decisions regarding variety selection and raw-material management.