Processing methods affect phytochemical contents in products prepared from orange‐fleshed sweetpotato leaves and roots

Scholars world over continue to research on various approaches to achieve sustainable development goal 2 to end hunger, achieve food security and improve nutrition and promote sustainable agriculture. The University of Nairobi has intensely researched in the areas of Food safety and Food security and trained various stakeholders in food handling to ensure the food products are not only safe for human consumption but also nutritious and wholesome.

Dr. George Ooko-Abong from the Department of Food Science, Nutrition and Technology conducted a research to show that processing methods affect phytochemical contents in products prepared from orange-fleshed sweet potato leaves and roots. The study evaluated the effects of common processing methods on phytochemical content in the roots and leaves of orange-fleshed sweet potato (OFSP) varieties called Kabode and SPK031. Click here to download full paper.

Extensive research shows that sweet potatoes ranks seventh (7th) among food crops at global scale and provides food to a large proportion of the world’s population (FAOSTAT, 2018). It has also been established that Orange-fleshed sweet potato varieties contain a high nutritional value, particularly in vitamins and minerals compared to many other root and tuber crops.

The paper brings out how various methods like boiling, fermenting, dehydrating and baking affect the nutritional content in the leaves and root tubers of Orange-fleshed sweet potato. The researchers conducted a series of experiments on 4 sweet potato varieties where the roots and leaves were analyzed.  The samples were then processed using the following common methods: boil, fry, bake and dehydration.

 Findings show that “Vitamin C content varies in sweet potato products and Vitamin C content was highest in boiled roots. Boiling retained more than 100% of all Carotenoids, while fermenting and drying the leaves retained between 22%–48% Carotenoids. Researchers also discovered that frying roots and leaves retained 100% Carotenoids.

This study documents effect of processing methods and the interaction between processing methods and sweetpotato varieties on inherent phytochemical content of processed foods prepared from leaves and roots of selected sweetpotato varieties in Kenya. The researchers concluded that traditional boiling enhances the retention of phytochemicals in roots, whereas boiling degrades most of these phytochemicals in leaves. Fermentation and dehydration of leaves and frying sweetpotato roots leads to reduction of antinutrients in sweetpotato leaves and roots, respectively. This study shows the possibility of selecting processing method to improve the target phytochemical content in the processed sweetpotato food products.

This research was conducted by  George Ooko Abong' , Tawanda Muzhing, Michael Wandayi Okoth, Fredrick Ng'ang'a, Phillis Emelda Ochieng, Daniel Mahuga Mbogo, Derick Malayi,  Machel Akhwale