Sun drying of grains

In 2 vols.Available from British Library Document Supply Centre-DSC:DXN020652 / BLDSC - British Library Document Supply CentreSIGLEGBUnited Kingdo

Effects on direct sun drying of maize grains on perforated and unperforated surface

Tanzania Journal of Agricultural Sciences 2000, VoL 3(2) : 97-102Sun drying ofmqize grains on unperforated and perforatedsurfaceswas conducted under simulated solar radiation intensity of afJout 800 Wlm: and in the field, where solar radiation intensity was variable. ,The drying depths employed were 10, 20, 30 and 40 mm under simulated solar radiation conditions and 20 and 40 mm in the field The response variables measured were weight loss at all depths and moisture content and temperature distributions in the 40-mm depth bed The results in terms of overall drying rates indicate that, at depths greater than 10 mm, the perforated surface was superior (P < 0.05) to the unperforated and at 40 mm th.e efJectwas about double that of the contro/. Changi,!gof dryingdepthfrom 10 to. either 20 or 30 mm on the perforated surface did not affoct the specific drying rates significantly (P < 0.05) 'except on 40/,;;n depth. On the unperforated surface the overall specific drying rates decreased significantly (P<O. 05) with ~hange oj drying depth from 10 to 20 mm and above: Lolt'er moisture gradients were achieved on th£! ierforaied surface and despite the higher drying rates temperatures in the bed were , lower than on the u;lperforated surface. In order for high drying throughput to be achieved, drying depth ' of about 30';"m on perforated surfaces is recommended. Sun drying in the field yielded results that were similar to those obtained under simulated solar radiation conditions despite the fluctuating nature ofterrestrial solar radiation intenSity. Further work in the field, focusing on theefJect of aperture size ofperforations and 'the gap ~ize between the drying surface and the ground floor for perforated surfaces is needed.'

Assesssment of the Perfomance of sun drying of maize grains on perforated surfaces

Tanzania Journal of Agriculture Science 1998, Vol. 1(2): pp 195-197Sun drying of maize grains on different mesh sizes ofperjorated trays using different heights from the ground was investigated. The mesh sizes used were 1.5 mm and 3 mm at the elevations of 30, 60 and 90 cm. The results show that both mesh size and height from the ground affect the drying rate and seed viability. The combination of90 cm elevation and 3mm mesh size gave the highest drying rates and lowest seed viability loss

Effects on direct sun drying of maize grains on perforated and unperforated surface

Tanzania Journal of Agricultural Sciences 2000, VoL 3(2) : 97-102Sun drying ofmqize grains on unperforated and perforatedsurfaceswas conducted under simulated solar radiation intensity of afJout 800 Wlm: and in the field, where solar radiation intensity was variable. ,The drying depths employed were 10, 20, 30 and 40 mm under simulated solar radiation conditions and 20 and 40 mm in the field The response variables measured were weight loss at all depths and moisture content and temperature distributions in the 40-mm depth bed The results in terms of overall drying rates indicate that, at depths greater than 10 mm, the perforated surface was superior (P < 0.05) to the unperforated and at 40 mm th.e efJectwas about double that of the contro/. Changi,!gof dryingdepthfrom 10 to. either 20 or 30 mm on the perforated surface did not affoct the specific drying rates significantly (P < 0.05) 'except on 40/,;;n depth. On the unperforated surface the overall specific drying rates decreased significantly (P<O. 05) with ~hange oj drying depth from 10 to 20 mm and above: Lolt'er moisture gradients were achieved on th£! ierforaied surface and despite the higher drying rates temperatures in the bed were , lower than on the u;lperforated surface. In order for high drying throughput to be achieved, drying depth ' of about 30';"m on perforated surfaces is recommended. Sun drying in the field yielded results that were similar to those obtained under simulated solar radiation conditions despite the fluctuating nature ofterrestrial solar radiation intenSity. Further work in the field, focusing on theefJect of aperture size ofperforations and 'the gap ~ize between the drying surface and the ground floor for perforated surfaces is needed.'

Cassava Sun Drying Performance on Various Surfaces and Drying Bed Depths

Tanzania Journal of Agricultural Sciences 2013, Vol. 12(1): PP 31-36Processing of cassava (Manihot esculenta Crantz) to obtain flour is faced with a lot of technical constraints including inefficient drying. The traditional sun drying method is very inefficient as the product can take 2- 3 days to dry. Mould growth and other problems such as contamination of the product are likely and therefore necessitate intervention. Among the interventions was sun drying on a platform raised 1 m above ground in comparison with drying in a direct box solar dryer; by using trays with various bottom surfaces. The experiments were done using kiroba cassava variety obtained from the University farm, which was peeled and sliced into thin chips (2-3 mm) then sun dried on wire mesh, black polythene, white polythene and woven mat for three days. The material was dried for 8 hours daily after which it was kept indoors overnight. The surface with highest sun drying performance was wire mesh while white polythene was the least. The 10 mm bed depth attained constant weight in just about six hours of drying while for 20 and 30 mm bed depth it was about 16 hours and 40 mm bed depth for about 24 hours. There was moisture adsorption which was at 10, 22 and 28 hours for the 10 mm bed depth, 10, 20, 26 and 28 hours for 20 and 30 mm bed depths, and 28 hours for the 40 mm bed depth. The time 0,10 and 20 hours marked the beginning of drying whereas 8, 18 and 28 hours marked the end of drying. The best performance was therefore obtained on wire mesh and 10 mm bed depth and recommended for sun drying of cassava. However; there is need to investigate on whether there is significant quality difference between cassava sun dried at different bed depths investigated in this stud

Improving sweet potato processing and storage performance throug slicing, drying and packaging

Tanzania Journal of Agricultural Sciences 2003, Vol 6(1) : 19:27Sweet potato is an important food security crop in, many parts of Tanzania. Despite this potential, research into its post-harvest handling for maximum utilisation hass been low. The objective of this study was therefore, to assess slicing performance of a fabricated hand operated slicing machine against the traditional knife slicing by hand in the production of michemhe. It also assessed how slice thickness, the drying surfaces, and packaging of the slices influenced quality during storage. The slicing machine was set to produce slices of 4.8 12 and 16 mm thickness. Together with the traditionally obtained slices the samples were dried on three surfaces (perforated surface, thatched roof and on the ground) for three days. Dry samples were then packaged in polypropylene bags, perforated polyethylene bags and sealed plastic containers and stored for nine months with observation carried in three months intervals. The investigations included moisture content, fungal count and mycotoxin detection discoloration and insect infestation aa quality attributes. Results showed that the slicer throughput ranged between 16 and 46 kg/h of fresh peeled roots in the thickness range of 4-16 mm, against 17 kg/h for traditionally sliced (75 mm) sweet potatoes. During drying, weight of slices decreased exponentially with time. In terms of drying effectiveness, the three drying surfaces used displayed almost the same final mean moisture content in the lower slice thickness range (4-8 mm). With increased slice thickness to 12 and 16 mm: the perforated surface was the most effective (10. 63-18. 03%) followed by the ground floor- (15.67-18.65%) and thatched roof the least (16.5-19.36%) Quality of dried michembe decreased with storage time and the best performance was obtained in polypropylene bags for the nine months storage. Packaging in sealed plastic containers produced the worst results. Quality was also influenced by the drying surfaces used with ground floor resulting in poor product and perforated surface the best. Increasing the slice thickness affected the quality of the dry product except in the range of 4 to 8 mm. Slicing of the roots to 4-8 mm drying on perforated surface and packging in polypropylene bags for room temperature storage of up to six months produced michembe of acceptaple quality. Use of improved slicing machines including mechanically powered machines requires further investigation. Studies on more drying surfaces more packaging materials, and nutrition of michembe are also recommende

Cassava sun drying performance onvarious surfaces and drying bed depths

Tanzania Journal of Agricultural Sciences 2013, Vol. 12(1) : 31-36Processing of cassava (Manihot esculenta Crantz) to obtain flour is faced with a lot of technical constraints including inefficient drying. The traditional sun drying method is very inefficient as the product can take 2- 3 days to dry. Mould growth and other problems such as contamination of the product are likely and therefore necessitate intervention. Among the interventions was sun drying on a platform raised 1 m above ground in comparison with drying in a direct box solar dryer; by using trays with various bottom surfaces. The experiments were done using kiroba cassava variety obtained from the University farm, which was peeled and sliced into thin chips (2-3 mm) then sun dried on wire mesh, black polythene, white polythene and woven mat for three days. The material was dried for 8 hours daily after which it was kept indoors overnight. The surface with highest sun drying performance was wire mesh while white polythene was the least. The 10 mm bed depth attained constant weight in just about six hours of drying while for 20 and 30 mm bed depth it was about 16 hours and 40 mm bed depth for about 24 hours. There was moisture adsorption which was at 10, 22 and 28 hours for the 10 mm bed depth, 10, 20, 26 and 28 hours for 20 and 30 mm bed depths, and 28 hours for the 40 mm bed depth. The time 0,10 and 20 hours marked the beginning of drying whereas 8, 18 and 28 hours marked the end of drying. The best performance was therefore obtained on wire mesh and 10 mm bed depth and recommended for sun drying of cassava. However; there is need to investigate on whether there is significant quality difference between cassava sun dried at different bed depths investigated in this study

Cassava sun drying performance onvarious surfaces and drying bed depths

Tanzania Journal of Agricultural Sciences 2013, Vol. 12(1) : 31-36Processing of cassava (Manihot esculenta Crantz) to obtain flour is faced with a lot of technical constraints including inefficient drying. The traditional sun drying method is very inefficient as the product can take 2- 3 days to dry. Mould growth and other problems such as contamination of the product are likely and therefore necessitate intervention. Among the interventions was sun drying on a platform raised 1 m above ground in comparison with drying in a direct box solar dryer; by using trays with various bottom surfaces. The experiments were done using kiroba cassava variety obtained from the University farm, which was peeled and sliced into thin chips (2-3 mm) then sun dried on wire mesh, black polythene, white polythene and woven mat for three days. The material was dried for 8 hours daily after which it was kept indoors overnight. The surface with highest sun drying performance was wire mesh while white polythene was the least. The 10 mm bed depth attained constant weight in just about six hours of drying while for 20 and 30 mm bed depth it was about 16 hours and 40 mm bed depth for about 24 hours. There was moisture adsorption which was at 10, 22 and 28 hours for the 10 mm bed depth, 10, 20, 26 and 28 hours for 20 and 30 mm bed depths, and 28 hours for the 40 mm bed depth. The time 0,10 and 20 hours marked the beginning of drying whereas 8, 18 and 28 hours marked the end of drying. The best performance was therefore obtained on wire mesh and 10 mm bed depth and recommended for sun drying of cassava. However; there is need to investigate on whether there is significant quality difference between cassava sun dried at different bed depths investigated in this study

Adaption of the traditional coffee pulping machine to soybean dehulling

Tanzania Journal of Agricultural Sciences, 2008, 9(1) : 93 - 100Processing of soybean for human consumption requires wet heat treatment of the beans in order to inactivate anti-nutritional factors. After hot water treatment or steaming, dehulling of the bean has always been an uphill task for household processors in Tanzania. Dehulling is done by hand rubbing, which is tedious and time consuming. The traditional coffee pulping machine was adapted to dehull boiled soybean. Seven soybean varieties namely TGX-1876-2E, Bossier, Kaleya, TGX 1805-8E, Sable, Songea and Duicker were tried. This was a development process whereby three consecutively improved versions of dehulling machines were tested. The machines were branded Ml, M2 and M3, implying first, second and third generation, respectively. Bean recovery as a measure of performance was 74.3, 77.4 and 91.8% for Ml, M2 and M3, respectively compared with 89.7% for manual dehullingfrubbing. The respective throughput was 8, 10 and 28.2 kg/h compared with 0.43 kg/h for manual dehulling. The mean dehulling efficiency of the M3 dehuller was 82.4% which was the highest. The M3 dehuller's best performance was due to use of ball bearings to support the rasping roller axle instead of sleeves and its ergonomically suitable height. The M3 dehuller could be adopted for soybean dehulling under rural livelihood conditions but the economics for owning and running it needs to be explored. Its improvement to make it moiorised is recommended to increase throughput and increase chances for adoption in medium scale soybean processing

Adaption of the traditional coffee pulping machine to soybean dehulling

Tanzania Journal of Agricultural Sciences, 2008, 9(1) : 93 - 100Processing of soybean for human consumption requires wet heat treatment of the beans in order to inactivate anti-nutritional factors. After hot water treatment or steaming, dehulling of the bean has always been an uphill task for household processors in Tanzania. Dehulling is done by hand rubbing, which is tedious and time consuming. The traditional coffee pulping machine was adapted to dehull boiled soybean. Seven soybean varieties namely TGX-1876-2E, Bossier, Kaleya, TGX 1805-8E, Sable, Songea and Duicker were tried. This was a development process whereby three consecutively improved versions of dehulling machines were tested. The machines were branded Ml, M2 and M3, implying first, second and third generation, respectively. Bean recovery as a measure of performance was 74.3, 77.4 and 91.8% for Ml, M2 and M3, respectively compared with 89.7% for manual dehullingfrubbing. The respective throughput was 8, 10 and 28.2 kg/h compared with 0.43 kg/h for manual dehulling. The mean dehulling efficiency of the M3 dehuller was 82.4% which was the highest. The M3 dehuller's best performance was due to use of ball bearings to support the rasping roller axle instead of sleeves and its ergonomically suitable height. The M3 dehuller could be adopted for soybean dehulling under rural livelihood conditions but the economics for owning and running it needs to be explored. Its improvement to make it moiorised is recommended to increase throughput and increase chances for adoption in medium scale soybean processing