Postharvest quality improvement of sorghum (Sorghum bicolor (L.) Moench) grains

Abstract

The objectives o f this study were (a) to investigate the effect o f postharvest handling (threshing and storing) methods on the quality of sorghum (Sorghum bicolor (L) Moench) grains variety Numbu, in terms of the percentages of damaged grains and seed germination, population growth of Sitophilus zeamais, Fusariumproliferatum and F. verticillioides, fumonisin B, and carbohydrate contents, and the percentage of weight loss during storage. The change of moisture contents o f sorghum grains was also recorded. Threshing was conducted using wooden stick and a paddy thresher. Sorghum grains were packed in hermetic plastic bags. The conditions inside of the bags were airtight and normal. Each bag with different conditions inside was infested with 10 pairs of S. zeamais (1-14 days old). Sorghum was stored for one, two and three months under warehouse conditions. The results showed, that the moisture contents o f sorghum were lower than its standard safe moisture content (<14%) during storage. At the beginning of storage, the percentage of damaged grains caused by threshing using wooden stick was higher than that of using a paddy thresher. The increase of percentage o f damaged grains was caused among others by increase S. zeamais population under normal oxygen concentration inside of the bag (about 21%), consequently the percentage of weight loss was also increased. The percentage of seed germination of sorghum threshed using wooden stick was lower than that of threshed using a paddy thresher. The percentage of seed germination decreased with the increase of storage duration. Population of F.proliferatum and F. verticillioides decreased with the increase of storage duration. Fumonisin B1 content of sorghum threshed using wooden stick was higher than that of using a paddy thresher during one, two and three months o f storage. Fumonisin B1 contents were considered low. In general, carbohydrate content of sorghum threshed using either wooden stick or paddy thresher from the beginning up to three months o f storage were not significantly different. Threshing using a paddy thresher was better in comparison to threshing using wooden stick.