The effect of roasting on the nutritional and antioxidant properties of yellow and white maize varieties

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Summary Maize varieties (yellow and white) were roasted for 17 min; and allowed to cool, and later milled into powder. The nutritional evaluation (proximate composition, mineral and antinutrient content determination) and antioxidant properties investigation (reducing power, free radicals scavenging ability and Fe 2+ chelating ability) of the product was subsequently carried out. The result of the study revealed that roasting caused a significant increase ( P < 0.05) in the crude fat, carbohydrate, Ca, Na, Mg and Zn content. Conversely, a significant decrease ( P < 0.05) was observed in crude protein, crude fibre, Fe and K content. A significant decrease in the phytate content was also observed. However, the reduced phytate content did not have sparing effect on Zn bioavailability. Roasting significantly ( P < 0.05) reduced the extractible phenol and flavonoid content of the maize varieties. The antioxidant properties (1,1‐diphenyl‐2‐picrylhydracyl free radical scavenging ability and Fe 2+ chelating ability) followed the phenolic content pattern. However, roasting caused a significant increase in the ferric reducing antioxidant power of the maize varieties. Thus, roasting reduced the protein content of maize but also increased the energy value and antioxidant capacity as exemplified by high reducing power.