Improving shelf life of harvested sweet potato

Sometimes in 2017, on my way back from work I observed that sweet potato (Ipomea batatas (L) Lam) roots and freshly fried chips were being sold at almost all the bus-stops I passed, and it seemed like it was the new business in town. I became curious and wanted to know the reason for the sudden increase in consumption.

I took time to visit some wholesalers, retailers, and some end users, and as good as the increase in consumption was, one major thing common among them was that they all had issues with rapid deterioration of sweet potato and could not store for as long as they desired.  I observed that sweet potato was being used as a substitute of yam by consumers who are mostly from households that cannot afford to buy yam.

Every stakeholder in the value chain could not keep their tubers for more about 6 weeks without losing half of the produce because of the high moisture content and bruised periderm which occurs during harvesting.

The sudden increase in demand for sweet potato across the country was reported in the Nations Newspaper on the 25th July 2017. The reports also stated that sweet potato was fast becoming a substitute for cassava and a potential source of raw material for industrial uses and various finished products such as baby food, flour etc.  The realization of the challenges of short shelf life in sweet potato is why I decided to carry out my PhD research in looking into improving shelf life of harvested sweet potato roots in the market and household level.

A search for materials that were readily available, cost and eco-friendly, which could be used to extend the shelf life of sweet potato and still retain its nutritional content over the long period of storage.  I once again thought of results of a literature review which revealed that sawdust and wood ash has recorded successes in the inhibition of some pathogens responsible for the deterioration of sweet potato. So why not try to store potato with sawdust and ash?

Sawdust is known to provide cushioning and also prevent condensation of the roots. Reports also say that sawdust and wood ash contains phytochemicals which would be released gradually into the roots. At the end of the 5 month storage period it is expected that the sweet potato roots will still retain their nutritional and mineral content which will be adequate for consumer’s day-to-day dietary needs.

The use of sawdust for storage I believe is an eco-friendly approach as sawdust is a major waste that is readily available from wood processing factories in Nigeria.  However, for my research I ensured that sawdust was selectively collected to ascertain the tree species to be used in order to evaluate the efficacy of sawdust from the different tree species used in the study.

The research is also going to promote the cultivation of the purple flesh variety over the cream flesh variety in the country, which is currently at a ratio of 1:25. The purple skin has showed to have a better storage value than the cream flesh. The cultivation of the purple flesh in Nigeria is going to be another big step towards attaining food security in Nigeria.

Sweet potato will be analyzed for their nutritional content and aflatoxin profile at 5weeks, 10weeks, 15weeks and 20weeks of storage. The N-GAGE fund will provide adequate support for carrying out this analysis from August 2019.

The beneficiaries for this project will include

  1. Various flour mills in Nigeria who are currently looking for substitute for cassava flour.
  2. Household consumers, as they can now purchase adequate quantity of sweet potato without fear of losing it to deterioration or sprouting.
  3. My immediate community and Nigeria at large. Sawdust will be put to efficient use, giving us a more serene environment especially around sawmills. 

Finally, attendance at the 2019 Agri Summit in Ghent, Belgium will provide me with rare opportunity to broaden my horizon on recent developments in crop protection and increase my scientific network through meeting with other researchers at the summit.

Olajumoke Tobi Abimbola, Nigeria


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