Influence of mechanical activation of starch using planetary ball milling on the development of little millet gluten free bread

Abstract

Planetary ball milling is a simple and cost-effective green technology to mechanically activate starch. In the present study, little millet flour (LMF) was ball milled (BMF) and substituted in different amounts from 5 to 25 g/100 g in LMF. Herein, flour morphology, functional properties, batter rheology, bread physical and sensorial characteristics were investigated. Ball milling improved the ultrafine flour content (<40 μ) by 56.58 %. Flour microstructure revealed that mechanical activation structurally altered the starch granules and protein crosslinks leading to increased damaged starch content. In thermogravimetry, BMF (89.98 %) showed highest mass change than LMF (88.34 %) due to larger surface area. Also, BMF substitution significantly improved the water absorption (41.8 %), swelling power (93.77 %) and solubility (30.28 %), whereas gelatinization temperature, peak viscosity and enthalpy reduced signifying faster gelatinization. The XRD pattern and FT-IR spectra (1047/1022 cm⁻¹) revealed reduction in relative crystallinity of starch in BMF. In terms of batter, BMF substitution improved the viscoelasticity and pseudoplasticity with shear thinning behaviour. Compared to control (2.16 cm³/g), BMF15 bread had significantly higher specific volume (2.54 cm³/g) and softer texture. Sensorially, BMF15 received higher overall acceptability. Thus, mechanical activation modified the little millet flour and it can be used as potential strategy to develop better quality gluten free bread.