Researchers unearth the versatility of sweet potatoes

WITH keeping fit and eating healthy being the “buzzwords” today, the University of Pretoria has found a way to make the humble sweet potato last even longer in order to address micro-nutrient deficiencies among young children and pregnant women.

Sweet potatoes are reportedly high in fibre and antioxidants, which protect the body from free radical damage and promote a healthy gut and brain.

They’re also incredibly rich in beta-carotene, which is converted to vitamin A to support good vision and boost the immune system.

With all those benefits in mind, researchers at the University of Pretoria have found a way to make orange-fleshed sweet potato last longer as part of Innofoodafrica, a multinational, cross-continental project that aims to enhance food and nutrition security in Africa.

The researchers discovered that they could leverage the health benefits of the vegetable by making it into flour, as normally these potatoes only had a shelf life of between two to three weeks.

However, by turning them into flour, researchers have found that they could not only expand the vegetable’s shelf life, but also expand the number of ways they could be used.

PHD Food Sciences candidate Daddy Kgonothi, central to the development of this flour, has been working under the guidance of Professor Naushad Emmambux and Dr Nwabisa Mehlomakulu of the Department of Consumer and Food Sciences at the institution. He said they dried the sweet potatoes using various drying methods.

Kgonothi said since the vegetable was a perishable product, drying and milling the potatoes into flour was one of the best methods one could apply, giving it a shelf life of at least a year.

He said the process began with the team sourcing sweet potatoes from a commercial farm in North West, following a 4- to 6-month growth period, from planting to harvesting.

As it is a seasonal crop which is planted around November or December, the harvest takes place between March and June or July.

Following that, Kgonothi said the team set about testing different drying methods.

“The whole process took about three weeks, which included testing the drying process and doing the actual drying and milling. We used microwaves, infra-red applications and convection ovens to dry the potatoes and discovered that when we combined microwave drying with infra-red, drying the process was much faster. There was also higher retention of beta-carotene.”

With vitamin A deficiency being one of the leading causes of micronutrient deficiencies in children up to the age of six and among pregnant women, Kgonothi said flour made from orange-fleshed sweet potato could offer a helpful solution.

“The flour is also a good source of dietary fibre and of minerals such as iron, zinc and phosphorus. As flour, the application of orange-fleshed sweet potatoes is more diverse as the flour can be used in baked products like fortified bread or biscuits or as stabilisers in soups; due to its rich dietary fibre. As a bonus, because of its low viscosity, it can be used to make baby food, making it easy for infants to swallow,” he said.