Effect of home preparation practices on the content of provitamin A carotenoids in coloured sweet potato varieties (Ipomoea batatas Lam.) from Kenya

Abstract

The content of β-carotene was determined in raw peeled, boiled peeled and roasted peeled roots of six orange- and yellow-fleshed sweet potato varieties from Kenya to evaluate their vitamin A potential before and after household preparation. The boiling and roasting procedures were similar to traditional methods used in Kenya. Dried products, chips and flour, of the variety Zapallo were also analysed. The varieties differed in dry matter and β-carotene content (1240–10,800 μg/100 g fresh weight (FW)) and thus in vitamin A content (100–830 RE/100 g FW). As sweet potato roots are consumed after heating, the loss of all-trans-β-carotene during preparation should be taken into account. Boiling of roots of the selected varieties seemed to result in a higher true retention (TR) of all-trans-β-carotene than roasting and TR of all-trans-β-carotene seemed to be dependent on the variety (42–128%). Preparation of chips by drying resulted in a significant reduction of the all-trans-β-carotene content of approximately 21%, which was further reduced when flour was produced from chips. The varieties Tainung and SPK-004 can be recommended for consumption especially after boiling in order to enhance the vitamin A intake in Kenya. Both varieties have a high content of vitamin A, the losses after boiling are rather low and both varieties have high consumer acceptability. The content and stability of β-carotene in sweet potato is an issue that is particularly important for developing countries with high prevalence of vitamin A deficiency. In order to prolong the shelf life of sweet potato, it is necessary to implement and develop industrial or small scale processing methods so that it is possible to produce sweet potato products with highest possible vitamin A values in these countries. In developed countries, focus is on innovation of new products with a good taste and a high health value. Consequently, sweet potato and sweet potato products might have a future as healthy foods in developed countries, and therefore there is a need to build up an industry that can provide the people in these countries with high quality sweet potato foods.