β-carotene micellarization during in vitro digestion and uptake by Caco-2 cells is directly proportional to β-carotene content in different genotypes of cassava

Abstract

Cassava, a staple food in sub-Saharan Africa, does not provide adequate amounts of pro-vitamin A (VA) carotenoids and has been targeted for biofortification (i.e. selectively breeding cultivars of increased nutrient density with agroeconomically acceptable characteristics). However, the accessibility of pro-VA carotenoids for absorption in different cultivars of cassava remains unknown. Here, we used the coupled in vitro digestion/Caco-2 cell uptake model to screen the relative accessibility of β-carotene (βC) in 10 cultivars of cassava with varying concentrations of βC. After cooking (boiled for 30 min), the βC concentration in tubers from different cultivars ranged from less than detectable to 6.9 μg βC/g cassava. Samples were subjected to simulated oral, gastric, and small intestinal digestion to determine stability and micellarization of βC. All-trans βC, 9-cis βC, and 13-cis βC were the most abundant carotenoids in cooked cassava and recoveries after digestion exceeded 70%. Efficiency of micellarization of total βC was 30 ± 2% for various cultivars with no significant difference in isomers and linearly proportional to concentration in cooked cassava (r = 0.87; P < 0.001). Accumulation of all-trans βC by Caco-2 cells incubated with the diluted micelle fraction for 4 h was proportional (R2 = 0.99; P<0.001) to the quantity present in micelles. These results suggest that all-trans βC content appears to provide the key selection marker for breeding cassava to improve VA status and that the more complicated screening procedure using in vitro digestion coupled to cell uptake does not provide additional information on potential bioavailability. © 2007 American Society for Nutrition.