Stability of Carotenoids in Sweet Corn: Part 2. Effects of Blanching, Freezing, and Canning

Sweet corn is one of the most widely consumed vegetables in the U.S. and a rich source of carotenoids, making it an important dietary contributor of carotenoids on a population level. Sweet corn is commonly preserved in canned or frozen forms, but the available data on the effects of blanching, freezing, and canning on its carotenoids are very limited. As Part 2 of a comprehensive research project, this study was designed to evaluate the effects of blanching, freezing, and canning on carotenoids in sweet corn. The raw materials were harvested from the field and were processed immediately to frozen or canned samples. The processed samples were stored at -20 degrees C or at room temperature for one month for the frozen and the canned samples, respectively. Free and bound carotenoids were analyzed by high-performance liquid chromatography (HPLC) with an ultraviolet-visible (UV/vis) detector and HPLC-mass spectrometry (HPLC-MS). The three processing methods reduced the levels of free carotenoids but increased those of the bound carotenoids. As a result, the total carotenoids in the processed samples were either unchanged or lower than in the unprocessed sample. The stability of individual carotenoids was determined by the processing method and their chemical structures. In addition, cis isomers of lutein and zeaxanthin were formed during canning, which made total cis isomers a significant contributor of the total carotenoids in canned sweet corn. The data from this study provide important information that will enable improved estimations of dietary carotenoid intake from sweet corn products.