Influence of drought stress and growth temperature during kernel development on physical and chemical starch characteristics of malting barley

Background and Objectives: Starch is the main component of malting barley (Hordeum vulgare L.), and its physical and chemical characteristics are particularly important in further processing in the beverage industry. This study investigates how the parameters (i) growing temperature (high/low) and (ii) water deficit (drought stress) during grain filling affect starch characteristics by cultivating nine different commonly used malting barley varieties in greenhouses under defined conditions. Particle size distribution of the starch granules, their phase transition characteristics (DSC), the pasting temperature (RVA), and the amylose/amylopectin (AM/AP) ratio were examined to assess starch characteristics. Findings: Two-way ANOVA analyses revealed that drought stress during the grain-filling phase resulted in significantly smaller starch granules, lower onset, peak, and endset temperatures (DSC), and increased pasting temperature (PT) while not affecting the AM/AP ratio. High growth temperature during grain filling resulted in significantly higher onset, peak, and endset temperatures (DSC), lower phase transition enthalpies, significantly higher PTs, and lower AM/AP ratios. Conclusions: Growth temperature during kernel development affected starch phase transition characteristics the most, while water availability was significantly associated with starch granule sizes. Significance and Novelty: Climate change is increasing the events and severity of heat and drought in Europe. Agricultural practices and modern barley varieties must be adapted to these requirements to maintain processability for food production.