Effect of micronization of maize grains on shelf-life of flour.

The efficacy of micronization of maize (Arjun, EH-434042) in inactivating enzymes responsible for
lipid degradation and extending the shelf-life of whole maize flour was evaluated. Micronization at
2008C for 4 min resulted in complete inactivation of peroxidase enzyme and reduction in lipase
activity by 84%. Maize flour packaged in low density polyethylene pouches were exposed to
accelerated (90% RH/388C) and ambient (65% RH/278C) storage conditions. The results indicated
no significant change in free fatty acid content in micronized flour whereas a significant increase
was observed in raw flour under both the storage conditions. The color and carotenoid content
did not vary much during storage in both the maize flours. While micronized maize flour was
stored for 60 and 120 days under accelerated and ambient conditions, respectively, without significantly
affecting quality, the storage duration was only 15 and 30 days for raw maize flour under
similar conditions.
Practical applications
Most of the thermal processing methods employed for enzyme inactivation to extend the shelflife
of whole grain flour often involve longer processing time and in cases such as wet heating
require additional drying to keep the moisture content at safe levels. Infrared-based micronization
of grains is one novel method that combines benefits like improved starch digestibility and
enhanced shelf-life. The present study on micronization of maize grain was effective in inactivating
peroxidase and lipase activity and significantly reducing the formation of free fatty acids during
storage. Micronization enhanced the shelf-life of whole maize flour packed in low density polyethylene
pouches by fourfold when stored under ambient conditions. The outcome of this study
indicates that micronization of maize grain can be effectively employed to extended the “shelf-life
whole maize flour,” which otherwise is very less.