IN VITRO IRON BIOAVAILABILITY IN SWEET POTATO LEAF RECIPES AS AFFECTED BY PROCESSING METHODS

Iron deficiency is a leading form of malnutrition in developing countries with adverse consequences on immune status and morbidity from infections in all age groups. It is also associated with reduced physical capacity and cognitive performance in adults and children, respectively. In Tanzania, traditional vegetable recipes form part of legume and cereal based diets. The diets are characterised by high levels of inhibitors such as phytic acid and polyphenols, which reduces iron bioavailability. The low iron bioavailability could be enhanced by right food combinations and appropriate food processing methods. However, less is known regarding the effect of the same on iron bioavailability in these vegetables. This study was conducted to assess the effects of processing methods on traditional vegetables. Sweet potato leaves chosen as a representative vegetable was prepared through traditional and modified methods on the basis of handling practices before, during and after cooking. In the traditional method, fresh and sun-dried leaves were cooked with sunflower oil and without oil. Modification was done through cooking fresh and oven-dried leaves with sunflower oil, tomato, lemon and soybean. Iron bioavailability was determined by simulating gastrointestinal digestion using pepsin and pancreatin enzymes, followed by measurement of the soluble iron released by the digestion in a dialysis tube. Results showed that modified recipes were significantly higher (P<0.05) in iron bioavailability than the traditional recipes. Iron bioavailability in oven-dried recipes was significantly higher (7.08%) than in open sun-dried recipes (3.78%). The use of tomato and lemon as enhancers proved to be more effective, while recipes without oil were least in iron bioavailability. The study concludes that modified preparations with enhancing ingredients have higher potential in improving iron bioavailability in vegetables than traditional preparation methods. Since these findings are applicable to all traditional leafy vegetables, a nutritional education is therefore advised to promote their use.