Effect of Thermal Pretreatment on the Functional Constituents of Waxy Corn (Zea mays L.)

Quantitative changes in functional constituents of waxy corn (Zea mays L.) by 5 different thermal pretreatments, including roasting, steaming, microwave, puffing, and extruding, were determined and compared with those of the raw waxy corn. There were no significant differences in fatty acid compositions among the corn treated with 5 thermal treatments. Levels of $\alpha$- and $\gamma$-tocopherols, soluble amino acids, and phytosterols decreased by thermal treatments, while those of p-coumaric and ferulic acids considerably increased by thermal treatments. In particular, the contents of tocopherols and phytosterols, and souble amino acid decreased significant in the steaming and puffing processes, respectively, whereas those of 2 free cinnamic acids increased significantly in the steaming and puffing processes. The extruding process showed smaller quantitative changes in tocopherols, phytosterols, and hydroxycinnamic acid derivatives compared to other heat pretreatments. These results suggest that the extruding process have a positive effect on valuable phytochemicals in waxy corn.