Effect Of Ultra-low Moisture Content On The Storability Of Wheat And Maize

China has a large quantity of annual production and consumption of cereal grains. However, quality deterioration of cereal grains occurs since they were harvested. It was estimated that, due to inappropriate storage condition, the annual grain loss during storage could be up to millions of metric tons. The moisture content(m.c.) of grain is of great significance in grain purchasing, transportation, storage, processing and trading. Medium gluten wheat “Kaimai 21” and maize “zhengdan 958” were studied in this paper. Wheat was reconditioned to 12.5%, 9.5%, 7.7% and 5.9% m.c., and maize was reconditioned to 14.5%, 11.7%, 9.9% and 7.8% m.c., respectively. The changes in physiological and biochemical quality, storage quality, cooking quality and volatile compounds were inspected during 300d-airtight storage.Generally speaking, cereal grains with a low moisture content were more resistant to poor storage conditions. The longer the storage time and the higher the m.c. are, the faster the deterioration rate would be. Low m.c. has significant effects on the changes of physiological and biochemical qualities(p<0.05). Although deterioration rate of many quality indicators of wheat with low m.c. is slower than that of wheat with high m.c., high temperature has a greater influence on wet-gluten content and water absorption of gluten, which means that quality deterioration in these two indicators could not be retarded effectively only by decreasing the m.c.. There were no significant differences between wheat with 7.7% and 5.9% m.c. in the changes of conductivity, O2·-, MDA, catalase activity, POD, test weight, L* and b* value, wet gluten content, water absorption of gluten and falling number(p>0.05). However, seed viability of wheat with 5.9% m.c. were significant lower than that of wheat with 7.7% m.c.(p<0.05) during storage. And for maize, the lower the m.c. is, the higher the seed viability and catalase activity would be. Similarly, there were also no significant differences between maize with 9.9% and 7.8% m.c. in the changes of conductivity, O2·-, MDA, POD, test weight, L* and b* value(p>0.05). Fat acid value has a negative correlation with m.c., and maize with 7.8% m.c. showed the lowest increase in fat acid value, and it was still suitable for further storage after 240d-airtight storage. For cooking quality, wheat and maize both showed a negative correlation with their m.c. during storage. Wheat with 12.5% m.c was near light-unsuitable for further storage and maize with 14.5% m.c. was serious-unsuitable for further storage after 150 d. Nevertheless, wheat and maize with lowest m.c. were light-unsuitable for further storage after 300d-airtight storage.The major volatile compounds identified from wheat and maize could be categorized into seven groups, namely alkanes, alcohols, aldehydes, acids, ketones, esters and small amount of other compounds. The relative content of alcohols, aldehydes, ketones and esters in high m.c. wheat increased during storage, compared with that of alkanes, aldehydes, ketones decreased in low m.c. wheat. The relative content of alcohols, aldehydes, acids, and esters in high m.c. maize increased during storage, and some compounds with benzene and heterocycle functional groups were inspected in the late storage period. Meanwhile, the relative content of aldehydes decreased in low m.c. maize.SEM results showed that the higher the m.c. is, the more obvious changes in wheat’s endosperm and maize’s embryo could be found, but no significant visible changes could be observed between wheat with 5.9% and 7.7% m.c.In general, ultra-low moisture content has significant effects on decelerating the deterioration rate of wheat and maize in physiological and biochemical quality, storage quality, and cooking quality, especially effective for the fat acid value and tasting scores of maize. And it should be pointed out that ultra-low-moisture-content storage for wheat doesn’t have a high overall effect as maize does.