Comparison of spontaneous and ragi fermentations on the physicochemical and functional properties of cereal flours

Abstract

Spontaneous and ragi fermentations are the most common methods in producing traditional fermented foods in Indonesia. The present work aimed to compare the impacts of spontaneous and ragi fermentations on cereal flour properties. Three kinds of cereal, namely whole sorghum, waxy coix, and white maize were processed into flours through spontaneous fermentation, ragi fermentation, and without fermentation (control). Fermentation methods were adopted from the Indonesian traditional processing methods. Cereal grains were immersed for 72 h in distilled water (1:2 w/v) for spontaneous fermentation, and in 1% ragi tapai solution (1:2 w/v) for ragi fermentation. Meanwhile, native flour (without fermentation) was produced by grounding and sieving the cereal grains. Results showed that both fermentation techniques significantly altered the physical properties of cereal flours, as indicated by the increase in lightness index and decrease in water-binding capacity and viscosity. However, cereal flours’ chemical and functional properties remain unchanged during fermentation, except for lipid and amylose. Spontaneous fermentation significantly resulted in the lowest lipid content of cereal flours, while ragi fermentation resulted in the lowest amylose content of cereal flours. Sorghum flour generally showed better nutritional properties among the examined cereal flours, especially lipid, protein, and dietary fibre. Meanwhile, waxy coix and white maize flours had the highest folate.