Micronization of maize flour: Process optimization and product quality

• A central composite design technique was used to optimize micronization conditions.
• The optimum combination of variables obtained resulted in 7.7% enhancement in RDS.
• Micronization leads to 93–94.5% reduction in peroxidase enzyme activity.
• Micronization significantly reduced the lipase activity.

Micronization refers to high temperature short time processing of grains using near infrared rays. The present study is focused on optimization of process conditions for micronization of maize flour with an emphasis on enhancing rapidly digestible starch (RDS) content for enhancing starch digestibility and inactivation of peroxidase enzyme for probable extension of shelf-life. The study employed a central composite design (CCD) with three variables namely, time (60–180 s), temperature (130–170 °C) and moisture content (20–40%) with RDS and peroxidase contents as responses. The optimized micronization conditions (173 s, 159 °C, 40% mc; 164 s, 166 °C and 40% mc) resulted in 7.1–7.7% increase in RDS content and 92.5–96.2% inactivation of peroxidase enzyme, respectively, without significantly affecting protein, carbohydrate and fat content of flour. Validation studies showed that experimental values matched well with that of predicted, suggesting suitability of the model used. At the optimized conditions, micronization was also able to inactivate lipase activity by 66.9–68.2%.