Influence of particle size distribution on in vitro digestibility and nutritional quality of differently coloured wholegrain maize flours

Maize (Zea mays L.) is one of the most important cereal crops in the world, along with wheat and rice. Considering that many physical and chemical factors influence the digestibility of food and feed ingredients, this study aimed to determine the effect of particle size on the in vitro digestibility and nutritional properties of various wholegrain maize flour fractions. Maize grains of various genetic backgrounds and kernel colours were used in this study, namely, white dent, yellow popcorn, red dent and blue popcorn. After grinding maize grains on a stone mill, the wholegrain flour was dry-sieved through three mesh sieves: 1700 mu m, 710 mu m and 212 mu m. The medium particle size fraction (710-212 mu m) was dominant. The in vitro digestibility testing showed that the powder fraction (< 212 mu m) was the most digestible in all investigated samples, while the coarse fraction was the least digestible. The yellow popcorn genotype showed the highest overall digestibility. An increase in the protein content was observed with a decrease in the particle size of the fraction. The findings of this study offer new possibilities for incorporating various wholegrain maize flour fractions in food or feed to meet the specific needs of various categories of consumers.