Development and characterisation of calcium and vitamin D-fortified starch-based multi-millet extruded snack

This research develops a multi-millet extruded snack fortified with calcium and vitamin D. Extrusion conditions were standardized at 20 % feed moisture, 150 rpm screw speed, 20 mPa, and 120 °C. Extruded snacks exhibited favourable physicochemical properties, including bulk density (0.13–0.17g/cm³), sectional expansion index (10.68–12.45), water absorption index (5.32–6.22g/g), and water solubility index (6.70–7.84 %). Structural analysis via SEM revealed starch gelatinisation, resulting in a glossy texture, while XRD showed a more symmetrical, aligned structure due to the breakdown of dense irregularities. FTIR spectra confirmed the presence of functional groups, and TGA indicated complete weight loss at 350–400 °C. DSC revealed thermal transitions: melting (60–70 °C), gelatinisation (119 °C), and degradation (170 °C). ICP-OES revealed notable mineral content, including calcium (125–131mg/100 g), iron (3.12–3.87mg/100 g), potassium (135.58–255.88 mg/100 g), magnesium (46.63–59.08mg/100 g), manganese (0.53–0.85mg/100 g), and zinc (1.1–2.36mg/100 g). The extrudes were pale yellow, with ES 3 (Extruded Sample 3) emerging as the best due to higher sectional expansion index, optimal hardness and water absorption index (WAI) and water solubility index (WSI). The study successfully demonstrated that extrusion processing could produce fortified multi-millet snacks with improved functional properties.