Improving vitamin A nutrition in low-income countries. In vitro bioaccessibility of provitamin A carotenoids in biofortified orange-fleshed sweet potato
Doctoral thesis, 2010

Vitamin A deficiency is a major nutritional disorder in a large number of low-income countries that is caused by an inadequate intake of preformed vitamin A and provitamin A carotenoids in the diet. The objective of the present thesis was to evaluate orange-fleshed sweet potato (OFSP) as a biofortified food source of provitamin A carotenoids with a potential to be included in a diet for alleviating vitamin A deficiency. The effects of various thermal processing and drying methods on the retention and in vitro bioaccessibility of β-carotene in OFSP were investigated using HPLC and an in vitro digestion model. The cell structure and β-carotene morphology in fresh and thermally processed OFSP were visualized by brightfield and coherent anti-Stokes Raman scattering microscopy. The interactive effects of simultaneous uptake of β-carotene from micelles and iron were studied using a Caco-2 cell model. Biofortified OFSP cultivars from Uganda contained high levels of all-trans-β-carotene ranging from 108 to 315 μg/g dry weight. Traditional preparation methods resulted in moderate losses of β-carotene with approximately 78% of the all-trans-β-carotene content retained, and the effects of boiling, steaming and deep-frying were similar. However, the degree of cell wall damage strongly influenced the in vitro bioaccessibility of β-carotene, which was clearly indicated by the 31% to 50% transfer of all-trans-β-carotene from the OFSP matrix to the micellar phase in samples that were homogenized prior to boiling, considerably higher than in samples that were thermally treated prior to homogenization (11% to 22%). These findings correlated qualitatively very well with the differences observed in size and number of β-carotene bodies in the in vitro digested samples. Furthermore, β-carotene bodies were co-located with starch granules in the OFSP matrix. The Caco-2 cell model showed that the uptake of β-carotene was reduced in the presence of physiological amounts of ferrous chloride, and this effect was concentration dependent. However, no evidence of an impact of β-carotene on iron uptake was observed. The results in the present thesis indicate that a meal supplemented with OFSP together with a small amount of fat would provide enough β-carotene to completely cover the daily vitamin A requirements for preschool-age children. In summary, the high content and in vitro bioaccessibility of β-carotene from thermally processed OFSP suggests that this food crop can be considered a promising food-based approach to prevent vitamin A deficiency in a sustainable manner.




provitamin A carotenoids

coherent anti-Stokes Raman scattering microscopy

vitamin A deficiency

food processing

orange-fleshed sweet potato

in vitro digestion

Caco-2 cells

10:an, Kemivägen 10, Chalmers tekniska högskola
Opponent: Paul van Jaarsveld, Medical Research Council, Tygerberg, South Africa


Anton Bengtsson

Chalmers, Chemical and Biological Engineering, Life Sciences, Food and Nutrition Science

Subject Categories

Biological Sciences

Chemical Sciences



Doktorsavhandlingar vid Chalmers tekniska högskola. Ny serie: 3095

10:an, Kemivägen 10, Chalmers tekniska högskola

Opponent: Paul van Jaarsveld, Medical Research Council, Tygerberg, South Africa

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