EFFECTS OF ROASTING TEMPERATURE AND TIME ON BULK DENSITY, SOLUBLE SOLIDS, BROWNING INDEX AND PHENOLIC COMPOUNDS OF CORN KERNELS

Abstract

Changes in physicochemical properties of corn kernels as affected by roasting temperature and time were investigated and described using mathematical equations. Corn kernels were roasted for up to 50 min at 160, 180, 200, 220 and 240C. The weight, bulk density, soluble solids, pH, browning index and phenolic compounds of roasted corn were assayed throughout the roasting process. The levels of weight, bulk density and pH of corn decreased, while the levels of soluble solids, browning index and phenolic compounds increased, when the roasting temperature and time increased. The higher chemical changes in corn occurred at above 200C. The change patterns in the levels of soluble solids and phenolic compounds during roasting satisfactorily followed first-order and zero-order equations, respectively. Temperature dependence of these changes was described by Arrhenius equation. PRACTICAL APPLICATIONS Corn (Zea mays L.) is treated by various food processing technologies including roasting in order to be consumed as foodstuff. Quality and utilization of roasted corn may be dependent on the roasting conditions. However, the control of roasting process is roughly carried out by an experience of operators. In the present study, the changes in physicochemical properties of corn kernels during roasting process were determined. The results showed that physicochemical changes in corn were significantly affected by the roasting temperature and time. Thus, roasting temperature and time should be quantitatively controlled to obtain a desired quality of the roasted corn kernels. The change kinetics of physicochemical property obtained in this study could be considered as an indicator for quality control in roasting processes dependence on the utilization of the roasted corn kernels.