Physicochemical, Nutritional and Functional Properties of Popped Finger Millet (Eleusine coracana) and its Application in Product Development

Abstract

Finger millet (Eleusine coracana) is a highly nutritious grain with significant health benefits; however, its traditional processing methods have not been fully optimized for modern applications to enhance commercialization. This study evaluated the physicochemical, nutritional, and functional properties of popped finger millet and its application in cereal bar development. Finger millet grains were sourced from Jamhuri Market in Thika Town. The grains were sorted, cleaned, and dried, with an initial moisture content of 10.01%. The moisture content was subsequently adjusted to 15%, 18%, and 21% (in triplicates) and popped at chamber pressures of 120, 140, and 160 psi. The popped grains were analyzed for selected physicochemical, nutritional, functional, and microstructural properties. Grains popped at 21% moisture content and 160 psi were used to formulate five cereal bar variants with varying concentrations of guar gum and honey, which were then subjected to sensory, physicochemical, and microbiological analyses. Results indicated that increasing moisture content and pressure significantly (p≤0.05) enhanced popping yield and expansion ratio while reducing bulk density. The interaction between pressure and moisture content also had a significant (p≤0.05) effect on these parameters. Increasing moisture content from 15% to 21% significantly (p≤0.05) increased lightness and total color difference, while redness and browning index decreased significantly with increasing moisture content and pressure. Crude fat and moisture content of the popped grains decreased significantly (p≤0.05) with increasing pressure and moisture, whereas crude protein content increased significantly with pressure. Mineral analysis showed significant (p≤0.05) increases in zinc and iron content with increasing pressure and moisture levels. Total phenolic content also increased significantly, while phytates and tannins decreased significantly (p≤0.05), indicating improved nutritional quality. Functional properties were significantly influenced by processing conditions, with water absorption capacity, swelling power, and viscosities increasing, while bulk density decreased when popping pressure and moisture content were raised. Particle size distribution was also significantly affected by pressure, moisture, and their interaction. For the developed cereal bars, color attributes (lightness, redness, yellowness, and hue angle) varied significantly (p≤0.05), with increased lightness and yellowness observed at higher honey levels (10%–50%). Water activity ranged from 0.391 to 0.776 and decreased with increasing honey concentration, remaining within safe microbial limits. Bulk density and texture decreased significantly (p≤0.05) with increasing honey levels, improving handling and packaging characteristics. Proximate composition showed moisture content ranging from 3.47% to 11.35%, crude fiber from 2.31% to 2.70%, crude protein from 7.17% to 8.39%, and carbohydrates from 70.02% to 78.24%, all significantly influenced by formulation. Microbial analysis of the developed cereal bars revealed total viable counts ranging from 2.2007 to 2.7253 log CFU/g, within acceptable limits for ready-to-eat foods. No coliforms were detected, indicating satisfactory hygienic practices. Staphylococcus aureus was detected in two cereal bars, although no immediate health risk was indicated, while yeast and mold counts remained within acceptable limits. Sensory evaluation showed significant differences (p≤0.05) in appearance, flavor, taste, texture, and overall acceptability. Samples B1 and B5 were the most preferred, with overall acceptability scores above 7.0. Honey and guar gum significantly influenced sensory attributes, with higher honey levels enhancing flavor and consumer acceptance. In conclusion, popping pressure and moisture content significantly affect the nutritional, functional, and physicochemical properties of finger millet and demonstrates strong potential for value addition. The developed cereal bars exhibited acceptable sensory and microbial quality, supporting their potential as nutritious snack products. These findings highlight the role of popped finger millet in enhancing food and nutrition security and promoting the utilization of this underutilized indigenous crop.