Effect of Germination on the Functional and Moisture Sorption Properties of High–Pressure-Processed Foxtail Millet Grain Flour

Abstract

Foxtail millet is one of the commonly cultivated, nutritionally competitive source of protein, fibre, phytochemicals and other micronutrients, as compared to major cereals like wheat and rice. Considering the potential of these grains, the high pressure processed flours of germinated (GFMF) and non-germinated foxtail millet (NGFMF) grains were studied for its functional, moisture sorption and thermodynamic properties. Germination and high-pressure processing of foxtail millet grains significantly improved the functional properties of the flour. Apart from this, the moisture sorption isotherms of both the flours were determined at 10, 25 and 40 °C and the sorption data was fitted to Guggenheim-Anderson-De Boer (GAB) sorption model. The monolayer moisture content for NGFMF and GFMF ranged between 3.235–2.364 and 2.987–2.063 g g−1, respectively. The isosteric heat of sorption ranged between − 76.35 to − 38.23 kJ mol−1 for NGFMF and 172.55 to − 34.02 kJ mol−1 for GFMF at a moisture range of 0 to 36%, whereas, the integral entropy of sorption for NGFMF ranged between − 0.404 and − 0.120 kJ mol−1 K−1 and for GFMF between − 0.667 and − 0.383 kJ mol−1 K−1. Along with the validation of the compensation theory, the values of spreading pressures lied in the range of 0–0.078 J m−2 for NGFMF and 0– 0.124 J m−2 for GFMF, while, the glass transition temperatures ranged between 82.25 and 28.67 °C for NGFMF and from 51.11 to 11.83 °C for GFMF at all three temperatures.