Improving sweet potato processing and storage performance through manipulation of slicing, drying and packaging

Abstract

To date, sweet potato processing is still a problem. In the rural areas of Tanzania, e.g., Shinyanga district, significant proportion of time is wasted, especially during slicing operation. The objective of this study was, therefore, to investigate the traditional slicing process so as to see if the fabricated slicer could be adapted to production of michembe that were similar to those produced traditionally and study how their drying and packaging were influenced during storage. Three drying surfaces (perforated surface, thatched roof and ground) were used for drying the samples for 3 days. Dry samples were then packaged in perforated polythene bags, sealed plastic containers and hessian bags and stored for 6 months with investigations carried out at the start, 3 and 6 months. The investigations included moisture content, visual examination, microbial counting and mycotoxin detection. Results showed that increasing thickness of the slices improved the throughput. However, the larger the thickness the longer it took for the slices to dry, which increased the browning of the slices and accelerated the spoilage by chemical reactions resulting from inadequate drying for the samples sun dried for 3 days. Done under village conditions, drying on the perforated surface proved to be the most effective in terms of drying rate and microbiological quality of the stored product while drying on the ground was the most inferior. Within the short drying period, infestation of the product by insect was evident, further supporting drying on the perforated surface as the most probable option if cost is not limiting. Results on storage have shown that, due to difficulties of drying, the slices produced at 12 and 16 mm knife settings and sun dried for 3 days spoiled within 3 months of storage due to high moisture. Storage in hessian bags produced best results, due to improved aeration in the package. Upgrading of the slicer to include multiple knives and motorization are recommended for purposes of increasing throughput, thus promote commercialisation of sweet potatoes. More shelf life studies are recommended, to include nutritional evaluation of michembe.