Microwave cooking significantly lowers lutein content of canned spinach. - GreenMedInfo Summary
Cellular transport of lutein is greater from uncooked rather than cooked spinach irrespective of whether it is fresh, frozen, or canned.
Nutr Res. 2008 Aug;28(8):532-8. PMID: 19083456
Department of Food and Nutritional Sciences, University College Cork, Cork, Republic of Ireland.
Lutein, a carotenoid found in significant levels in spinach, has attracted a great deal of attention owing to its reported function as a shield against the photooxidative effects of blue light. Therefore, the rationale of this study was to examine the effects of various processing and cooking methods on lutein bioavailability from spinach (Spinacia oleracea) using an in vitro digestion procedure coupled with the use of a human intestinal Caco-2 cell model. Fresh, frozen, and canned spinach were analyzed uncooked and after boiling or microwave cooking. Lutein content from the uncooked and cooked digested food (digestate) and appropriate micelles was determined. Micellarized lutein from the spinach samples was adjusted to 0.1 micromol/L and added to Caco-2 cells. Cellular uptake and secretion (cellular transport) of lutein were determined. Our results showed that digestate obtained from uncooked canned spinach had greater lutein content (P<.05) than uncooked fresh or frozen spinach. Microwave cooking, but not boiling, significantly lowered the lutein content of canned spinach digestate and micelles compared with their uncooked counterparts. Interestingly, there were no differences in the micellarization of lutein between the cooking and processing methods. Cellular transport of lutein was greater from uncooked spinach micelles compared with boiled or microwave-cooked spinach. To conclude, although the lutein content of digesta and micelles may have been modified, its micellarization was not significantly affected by any of the cooking or processing methods tested. In general, cellular transport of lutein was greatest in uncooked spinach irrespective of whether the spinach was fresh, frozen, or canned.