The influence of systematic heat and drought applications at defined growth stages on malting barley starch properties

BACKGROUND: Starch gelatinization behavior and the proportion of B-granules are crucial for malt quality as a result of their impact on starch degradation during malt-based beverage production. Starch structure and resulting starch properties are determined by the starch synthesis during barley plant growth, which is influenced by barley genetics and environmental growing conditions. Because climate change is altering growing conditions increasingly, insights into the relationship between growth conditions, genetics and relevant starch properties are of upcoming importance. Thus, as a factorial experiment, three malting barley varieties (Morex, Scarlett and Avalon) were grown in highly controlled climate chambers with systematic variations in heat and drought conditions to investigate the influence of (i) pre-anthesis growth temperature [growth stage (GS) < 61]; (ii) temperature from GS 61–75 and from GS 75–93; (iii) malting barley variety; (iv) drought stress; and (v) interactions between those factors on resulting gelatinization behavior (using differential scanning calorimetry) and the B-granule proportion (detected by laser diffraction). RESULTS: (Stepwise) multiple linear regression calculations (MLR/SMLR) revealed that (i) pre-anthesis growth temperature significantly affected gelatinization behavior (onset, T_o; endset, T_E; enthalpy, ΔH) but not B-granule proportion; (ii) starch properties were not significantly and variety-independently different after heat stress from GS 61–75 or heat stress from GS 75–93; and (iii) additional drought stress did not significantly change T_o and T_E values per se, but significantly affected ΔH and B-granule proportion values. CONCLUSION: Growth conditions before GS 55 significantly impact starch gelatinization behavior, indicating that starch synthesis is highly affected by conditions before anthesis.