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 the three cooking methods (boiling kernels, porridge and tortilla). Also, using the in vitro digestion model, we assessed the effects of cooking methods on carotenoid absorption efficiencies (digestion stability, micellization efficiency and bioaccessibility). The results indicated that the carotenoid content obviously increased in the boiling kernels, but the carotenoid bioaccessibility was the lowest comparing to porridge and tortilla. Tortilla presented the highest digestion stability of β-carotene (309 ± 63 %) and the bioaccessibility of xanthophylls (22.4 ± 0.5 % for lutein and 18.5 ± 1.0 % for zeaxanthin) among three cooking products during the in vitro digestion. The contents of carotenoids in porridge were all the lowest in three cooking products, however, the low concentration level of xanthophylls reduced the competitive effect on the 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 negatively correlated with the micellization of β-carotene. And this correlation between the xanthophylls and β-carotene was not affected by the cooking methods. These results together suggest that tortilla and porridge are the better dietary choices to intake 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.