Effect of Polishing on Nutritional, Physical, Functional and Colour Characteristics of Foxtail Millet

Abstract

Foxtail millet (Setaria italica L.) is a nutrient-rich, climate-resilient minor millet; however, polishing, while improving processing and eating quality, can alter its nutritional, physical, and functional characteristics. The present study evaluated the effects of 5% and 10% polishing on the nutritional, physical, functional, and colour characteristics of foxtail millet, using dehulled unpolished grain as the control. Foxtail millet variety SIA-3088 was dehulled and polished to 5% (P5FM) and 10% (P10FM), and the samples were analysed in triplicate. Polishing significantly affected fat, crude fibre, protein, total dietary fibre, carbohydrate, and energy contents (p < 0.01 to p < 0.001). Protein content increased from 13.41% in the control to 13.80% and 14.07% in P5FM and P10FM, respectively, while total dietary fibre decreased from 9.313% to 6.786% and 6.062%. Crude fibre decreased from 1.70% in the control to 1.487% and 1.471% in P5FM and P10FM, respectively, whereas fat increased from 5.28% in the control to 6.17% and 5.70% in P5FM and P10FM, respectively. Energy content increased from 382.1 to 387.1 and 385.5 kcal/100 g. Physical and functional properties were significantly influenced by polishing. Bulk density decreased from 0.5683 g/mL in the control to 0.5062 and 0.5167 g/mL in P5FM and P10FM, respectively, while tapped density decreased from 0.8152 to 0.8128 and 0.7938 g/mL, respectively. Water absorption capacity increased from 1.280 to 1.371 and 1.389 g/g in P5FM and P10FM, respectively, whereas oil absorption capacity did not differ significantly. Colour characteristics were not significantly affected, with L*, a*, and b* values ranging from 62.65-63.19, 7.713-7.987, and 34.09-35.21, respectively, and ΔE values below 1. Overall, polishing up to 10% significantly modified the nutritional and functional properties of foxtail millet while maintaining its colour characteristics, suggesting that moderate polishing can improve functional attributes without substantial visual changes.