Changes of Phytochemical Contents in Sweet and Waxy Corn (Zea mays L.) as Affected by Cultivars and Growth Stages

Background: Sweet and waxy corn (Zea mays L.) are high in phytochemicals which vary depending on several factors including corn cultivars and the maturation stage. Methods: Five commercial sweet and waxy corn cultivars were grown and their major phytochemical compositions were investigated at the milk, late milk, and soft dough stages. Phytochemicals in corn samples harvested from each kernel maturation stage were determined as total phenolic compounds, anthocyanins, tocopherols, and carotenoids. Results: Significant interactions between the corn cultivars and maturation stage were detected for all phytochemical compositions, with changes in their concentration during seed development. Total phenolic compounds and total anthocyanins were highest in the dark purple waxy variety (316.74 mg GAE/100 g of DW and 522.21 mg CGE/100 g of DW, respectively) in which cyanidin was the major anthocyanin. Carotenoid compositions were also affected by corn type and harvesting stage. The yellow sweet cultivars indicated higher levels of carotenoids than other colors, with lutein as the major carotenoid at concentrations from 0.05 to 8.46 µg/g of DW. Contents of γ-tocotrienol, γ-tocopherol, and α-tocopherol were observed in all five corn cultivars with similar influences of the maturation stage. Conclusion: Results suggested that the phytochemical contents of all five corn types showed diverse reliance regarding cultivars and maturity stages. The purple waxy and yellow sweet corn cultivars contained a high level of phytochemicals. This would open up a useful opportunity for the functional food industry as consumption of these corn cultivars would afford health benefits to consumers.