Mitigating the Damaging Effects of Growth and Storage Conditions on Grain Quality

Abstract

Today's grain market requires growers to maximize both yield and processing quality. Wheat breeding, the first focus in working towards these two objectives, promises the delivery of yield-related advantages, as well as providing varieties "tailor-made" for the various downstream processing requirements. Growth and storage conditions are next in determining grain quality at the flour mill. While we may have no control over many aspects of growth environment, the damaging effects may be mitigated, for example, by attempting to predict and forestall the risk factors, and by breeding as a means of "building in" genetic tolerance to environmental hazards. Significant loss of dough strength can be caused by heat stress, i.e., a few very hot days (> 35 C) during grain filling. Nevertheless, some genotypes are less affected than others, opening the possibility of selecting for tolerance to the dough-weakening effects of heat shock. Growers have the added opportunity of using statistical weather data to sow early enough to reduce the risk that heat stress may reduce both yield and quality. Buyers may also use information about climate fluctuations to select regions with grain of suitable quality. During prolonged storage, on the other hand, elevated temperatures appear to cause an increase in dough-strength potential. In this case, grain-moisture content is an important factor, interactive with storage temperature. Adequate water in the intermediate growth stage of the plant may affect the outcome of grain-protein content. On the other hand, rain at harvest leads to the risk of sprout damage, and the storage of moist grain is an obvious source of spoilage. Plant nutrition is a basic aspect of growth environment that affects grain quality. The economics of fertilizer use may be based on grain-yield considerations, plus maximizing protein content and thus premium payments. As a result, nitrogen fertilizer may be used, but in excess, this action may cause sulfur to be limiting, leading to a loss of dough-forming quality (especially extensibility). A test of N:S ratio in harvested grain can serve as an indicator of sulfur deficiency, a ratio of over 17:1 being considered abnormal. Finally, the approach of precision agriculture may offer possibilities of overcoming quality losses due to growth conditions. It offers the opportunities of applying variable inputs of fertilizer and of selective harvesting to optimize grain quality