Impact of hydrothermal processing on Job's tears grain fractions and its protein isolates: Evaluation of digestibility, functionality, and anti‐nutritional factors

Abstract

The study was focused on the effect of hydrothermal processing on the protein characteristics of Job's tears grain and its corresponding milled fractions. The protein isolated from native and treated grains was studied for their functional and physicochemical properties. The protein content of native and hydrothermally treated Job's tears was 20%–20.27%, 11.85%–12.26%, and 12.95%–13.70% in bran, endosperm, and germ-rich fractions, respectively. Hydrothermal processing improved the in vitro protein digestibility of grain fractions (up to 38%) and protein isolates (40%–55%) and decreased the anti-nutritional factors. There was a significant change in the surface hydrophobicity of globulin (148.91–1,191.30), glutelin (108.54–791.47), and prolamine (823.68–2,352.00) in the grain fractions. The water absorption capacity of processed Job's tears protein isolates remained unaffected; however, the oil absorption (5.45 ± 0.02 to 7.61 ± 0.46), emulsion (16.02 ± 0.01 to 26.06 ± 0.13), and foaming capacity (14.16 ± 0.08 to 28.33 ± 0.02) improved. Job's tears protein was found to be of high quality with potential for food application as functional ingredient after hydrothermal processing. Novelty impact statement Job's tears grain is a nutritious but underutilized millet with very few reports available on the processing of the grain. The novelty of this paper lies in the hydrothermal processing, fractionation, and isolation of protein from the grain, the increase in protein digestibility of hydrothermally processed Job's tears grain fractions (bran, endosperm, and germ-rich fractions), and the decrease in the anti-nutritional factors that hampers the protein digestion. Moreover, by fractionating the grain, nutrient-dense milled fractions were obtained which can be used as a food ingredient in product development.