Determination of the causes and the effects of storage conditions on the quality of silo stored wheat (Triticum aestivum) in Zimbabwe

摘要

There are still cases of millers returning poor quality red wheat to the Zimbabwe Grain Marketing Board (GMB) and this has been an ongoing problem over the past few years. A larger amount of this wheat has discoloured and damaged embryos and it is discounted by millers because the germs are brittle and they crumble easily. There have been also many rejections of the red wheat particularly by major traders. Therefore there was an urgent need to investigate the causes and effects of storage conditions on the quality of silo-stored red wheat, since red wheat is one of human beings’ main food supplies. A representative sample of 2.25 kg of red winter wheat was randomly collected from the common red winter wheat incoming to the Grain Marketing Board Depot for storage. This representative sample of 2.25 kg was used as the control sample and its test density was determined. The control sample was then finely ground and analysed for protein, moisture, ash, aflatoxins and falling number. The red winter wheat was then stored in six different silos for a period of 5 months, with each silo having different humidity and temperature conditions. Representative samples of 4.5 kg were randomly collected monthly from each silo during the storage period. The test densities of the representative samples were determined. These representative samples were then finely ground and analysed for protein, moisture, ash, aflatoxins, and falling number. The results of the red wheat in storage were then compared with those of the control sample and analysed by analysis of variance (ANOVA) at the 5% level of significance. Results obtained after data analysis suggest that there were significant differences in the protein content, moisture content and falling number of the wheat before and after storage. However, differences in test density, aflatoxin and ash contents of the wheat before and after storage were not statistically significant at the 5% level of significance. The deterioration in wheat quality was attributed to the high storage temperature and humidity conditions. It was also concluded that the optimum conditions for wheat storage are a temperature of 15 oC and a humidity of 60%.