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Presentation 10: Comparison of postharvest handling methods on the quality and shelf-life characteristics of OFSP roots intended for processing into puree

The shelf-life of fresh sweetpotato roots can be improved through avoidance of damage incurred during harvesting and postharvest handling and transport. As fresh orange-fleshed sweetpotato (OFSP) roots start to be processed into nutritionally enriched products, more attention needs to focus on the supply of high quality roots to processors. A constant supply can be secured by: purchasing from different geographical areas; promoting staggered planting and/or irrigated off-season production; and through medium or long term storage of roots purchased during the peak season. Understanding of optimum harvest and postharvest OFSP fresh root handling practices for smallholder farmers and processors is currently very limited. To address this knowledge gap, we compared the effect of different harvesting, soil removal methods and packaging containers on the keeping quality of freshly harvested OFSP roots in Kenya.  The harvesting methods tested were manual or ox-plough. The soil removal methods were: wet manual; wet brush; dry manual; and no soil removal. The packaging containers tested were polypropylene sacks, wooden or plastic crates. Roots of two varieties were included, and were kept in different packaging containers for 3, 7, 10 or 14 days before sampling. At sampling a number of different criteria were assessed, including: weight change of over time; general appearance; root sponginess, shrivelling, rotting and damage; percentage out-turn of roots after peeling; peeling quality and speed. It was anticipated that washed roots kept in sacks would rot after 4-5 days, however, this did not happen. Weight loss over time was less pronounced for all soil removal treatments tested when the roots were kept in sacks for up to 14 days, as opposed to in wooden or plastic crates. The general appearance of roots following dry manual soil removal or no soil removal after harvest initially resembled freshly harvested roots more closely than the washed roots. The roots kept in sacks had a less rapid decline in general appearance than those kept in wooden crates. These results suggest OFSP puree processors should encourage the farmers they source roots from to manually wash the soil off the roots and then air-dry the roots and discard those with weevil damage or rotting before marketing them. In addition to enhancing the keeping qualities there are also economic benefits to the processor, due to the weight of the soil remaining on roots and water and labour costs. The results also suggest that the washed and air-dried roots can then be packed into sacks for transport to the processing facility to help reduce the weight of packaging materials being transported. However, sacks should not be over-packed. On arrival at the factory the roots can be further sorted to determine which need to go for immediate peeling and processing, which can be kept in sacks for up to 14 days, and which will be placed into curing and long-term storage. Further work is required to determine whether different postharvest handling recommendations are required for roots that will be stored long-term.


Stathers, T., Muoki, P., Kipkoech, B., Wahonya, O., Low, J., Muzhingi, T., Rees, D. 2016. Comparison of post-harvest handling methods on the quality and shelf-life characteristics of orange-fleshed sweetpotato roots intended for processing into puree. Presentation made at the 2016 Marketing, Processing and Utilization Cop Meeting in Tanzania.