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Presentation 7: Long term storage of sweetpotato roots to reduce puree supply chain risks

Agri-food supply chains, such as that of the nascent orange-fleshed sweetpotato puree used by a Kenyan supermarket chain for producing bread rich in vitamin A for the rapidly urbanising and nutritionally aware population, face a wide range of risks. Puree processors are affected by the pronounced seasonality of sweetpotato production and prices, adverse weather conditions, and fluctuations in market-demand particularly during the early stages of market development.

Value chain study suggested the storage of fresh sweetpotato roots by puree processors for periods of up to four months could help mitigate these supply chain risks. Temperature and humidity controls were installed in two insulated store rooms, one powered by solar and the other by mains electricity, at the Organi sweetpotato processing facility in Nyanza, Kenya. Freshly harvested roots of Kabode and Vita, two orange-fleshed sweetpotato varieties, were placed in wooden crates in each of the rooms. The roots were cured for five days, prior to reducing the temperatures to support long-term storage. The effect of washing or dry manual removal of soil from the roots prior to storage was also evaluated.

The trial has been designed to assess the quality of the stored roots after 2, 4, 6, 8, 12 and 16 weeks storage. Weight loss, general appearance, root sponginess and the occurrence of surface moulds, sprouting, Cylas spp. weevil damage, and rotting were recorded. At each of the monthly assessments, 25 kg of roots from each treatment were processed into puree and the ease of root preparation, puree sugar content, stickiness, thickness and colour were assessed. Additionally, raw roots and puree samples were sent for further laboratory analysis including beta-carotene content and bread-making qualities. The early findings of these trials are shared and discussed.