Improved open-sun drying method for local swamp rice in Uganda
“Kaiso” and “Supa” are the main local swamp-rice (Oryza Sativa) varieties currently grown in Uganda mainly by smallholder farmers on small gardens (0.5 – 2ha). Due to lack of mechanized drying equipment and owing to the low volumes of their harvests, these farmers use open-sun drying methods, where the paddy is spread on tarpaulins, cemented floors or bare ground. In most cases the paddy is badly dried and is highly fissured. Such paddy on milling contributes to low levels of mill recovery and head rice count of the milled rice. Compared to other varieties and countries, the mill recovery and head rice levels are ostensibly low. The study aimed to improve the above method under the Ugandan weather conditions with a view to increase the mill recovery and head rice levels. Paddy of the predominant “Kaiso” variety was dried in sun on cemented floor at ten depths: control (farmers’ method), 30, 40, 50, 60, 70, 80, 90, 100 and 110 mm. The results showed that the best paddy drying depth was between 70 and 80 mm. However at these depths, the paddy takes 7 – 8 days to dry. To reduce the drying time, the paddy was first set to dry at 80 mm depth for two days; after which time, it was divided into three different potions that were further dried at different depths of 80, 40 and 30 mm. The results showed that samples whose drying depths were reduced to 40 mm and 30 mm took four days to dry while samples whose depths remained at 80 mm took 7-8 days. There were no significant differences in mill recovery values (p = 0.2968) and head rice levels (p = 0.5890). Improvement index in mill recovery was 1.14 and that of head rice was 1.24. Average aflatoxin level in the samples whose depth was reduced to 40mm was 4.8ppb and that reduced to 30 mm was 2.3ppb. From these results, it was recommended that “Kaiso” variety should be dried at 80 mm depth for two days and drying depth should be reduced between 30 and 40 mm for subsequent drying. It was further recommended that the method be tested with other swamp varieties before general conclusion is drawn that it can work for all swamp varieties.
Keywords: Head rice, mill recovery
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