Analysis of the effects of natural and pure culture fermentation for the qualitative enhancement of pearl millet flour

Abstract

Its high nutritive quality and ability to survive in harsh conditions makes pearl millet a suitable crop for arid and semi-arid regions, but anti-nutrient factors reduce the bioavailability and digestibility of its nutrients. Fermentation reduces anti-nutrients and hence increases protein digestibility and mineral bioavailability. Thus, the present work examines the effects of fermentation on the nutritive, physiochemical and functional properties and anti-nutrient composition of pearl millet flour. Natural fermentation at 20°C, 25°C and 30°C and pure culture fermentations with Saccharomyces cerevisiae, Saccharomyces diastaticus, Lactobacillus fermentum and Lactobacillus brevis were performed. Analysis revealed an increase in moisture and fat content and a decrease in protein content following all types of fermentation. Although the variation in protein levels in different fermentations was not significant, ranging from 10.29% to 9.83%, the effect on thiamine content was significant as it decreased with an increase in temperature in the range 20–30˚C in natural fermentation but was increased in pure culture yeast fermentations as compared with bacterial fermentations at their favourable temperatures, respectively. Total soluble sugar content decreased in pure culture fermentation but increased in natural fermentation. Fermentation decreased pH, thereby increasing titratable acidity. Oil and water absorption capacities were increased, while least gelation concentration was decreased in all types of fermentations. Also, anti-nutritional factors like tannins and phenolic compounds were significantly decreased in all fermentations. We conclude that fermentation is an efficient process to improve the quality of pearl millet flour.