THE INFLUENCE OF RECOVERY TEMPERATURE ON THE EFFECTS OF A BRIEF HEAT-SHOCK ON WHEAT .3. GRAIN PROTEIN-COMPOSITION AND DOUGH PROPERTIES

In this study; controlled-environment conditions were used to examine the main effects and possible interactions of moderately high (20-32 d egrees C) and very high (>32 degrees C) temperature treatments, during grain filling, on wheat protein composition and dough mixing behaviou r at maturity. In particular, we wished to examine whether the deleter ious effects of a short exposure to very high temperature (40 degrees C) could be compensated by the expected benefits of moderately high te mperature. To this end, wheat cv. Oxley was exposed to either 21/16 or 40/16 degrees C from 15-19 days after anthesis and subsequently grown under one of three moderately high temperature regimes until maturity : 21/16, 27/22 or 30/25 degrees C. Flour from each treatment was teste d for protein composition using size-exclusion high-performance liquid chromatography (SE-HPLC) and dough mixing behaviour using the 2-g mix ograph. We conclude that in the heat-sensitive cultivar Oxley: (a) mod erately high temperatures increased flour protein percentage; but (b) significantly decreased dough strength: measured as mixing time and re sistance breakdown; (c) a short exposure to very high temperature also increased flour protein percentage and reduced dough strength, regard less of the following moderately high temperature; (d) the effects of moderately high and very high temperature on dough strength tended to be additive; (e) protein monomer content (r = -0.83 to -0.93) and SDS sedimentation volume (r = 0.80 to 0.96) were highly correlated with th e response of dough strength to elevated temperatures. (C) 1997 Academ ic Press Limited.