Effects of three cooking methods on content changes and absorption efficiencies of carotenoids in maize
Maize is a staple source of certain carotenoids for the human diet, but food processing is an important factor affecting the carotenoid content and absorption. In this study, we investigated the content changes of carotenoids in maize under three cooking methods (boiling kernels, preparing porridge and preparing tortilla). Also, using the in vitro digestion model, we assessed the effects of the cooking methods on carotenoid absorption efficiencies (digestion stability, micellization efficiency and bioaccessibility). The results indicated that the carotenoid content obviously increased in the boiled kernels, but its carotenoid bioaccessibility was the lowest compared to that of porridge and tortilla. Tortilla presented the highest digestion stability of β-carotene (309 ± 63%) and bioaccessibility of xanthophylls (22.4 ± 0.5% for lutein and 18.5 ± 1.0% for zeaxanthin) among the three cooked products during in vitro digestion. The contents of carotenoids in the porridge were all the lowest among the three cooked products; however, the low concentration level of xanthophylls reduced the competitive effect on β-carotene micellization, which increased the bioaccessibility of β-carotene to 52.1 ± 5.0%. Additionally, the content of xanthophylls (lutein + zeaxanthin) in digesta significantly and positively correlated with the β-carotene content in digesta, whereas it negatively correlated with the micellization of β-carotene. This correlation between the xanthophylls and β-carotene was not affected by the cooking methods. These results together suggest that tortilla and porridge are better dietary choices for the intake of xanthophylls and β-carotene, respectively, among maize-based foods. Furthermore, the absorption of β-carotene was influenced by the content of xanthophylls whatever the cooking method.