Changes in Morphological and Physicochemical Properties of Waxy and Non-waxy Proso Millets during Cooking Process

Abstract

Proso millet, a grain which is principally consumed in cooked form, is favored by consumers because of its rich nutritional value. However, the changes in morphological and physicochemical properties of proso millet grains occurring during the cooking process have rarely been reported. In this study, we investigated the changes in morphological and physicochemical properties of cooked waxy and non-waxy proso millets. During the cooking process, starch granules in the grains were gradually gelatinized starting from the outer region to the inner region and were gelatinized earlier in waxy proso millet than in non-waxy proso millet. Many filamentous network structures were observed in the cross sections of cooked waxy proso millet. As the cooking time increased, the long- and short-range, ordered structures of proso millets were gradually disrupted, and the ordered structures were fully disrupted by 20 min of cooking. In both waxy and non-waxy proso millets, thermal and pasting properties significantly changed with an increase in the cooking time. This study provides useful information for the processing of proso millet in the food industry.

Effect of malting and fermentation on colour, thermal properties, functional groups and crystallinity level of flours from pearl millet (Pennisetum glaucum) and sorghum (Sorghum bicolor)

“…The A-typical arrangements of the diffraction patterns with high peaks were noticed in the processed and unprocessed flours of Agrigreen , Babala and sorghum were similar to other cereals reported by Kamble et al. (2019) , Yang et al. (2019) and Amadou et al.…”

“…From the results, it could be deduced that malted and fermented sorghum flour had the highest gelatinisation range 23.02 °C at 24 h mating and 24 h fermentation time than malted and fermented Agrigreen and Babala flours. Variations in the gelatinisation of processed flour could due to protein content, starch structures (in terms of crystal structure) ( Yang et al., 2019 ; Kaur and Singh, 2005). The melting enthalpy of starch-lipid complexes and protein-starch interaction that inhibits the absorption of water in the granule to swell up and gelatinise ( Liu et al., 2007 ).…”

Capitalizing on a double crop: Recent advances in proso millet's transition to a food crop

“…Regarding starch structure, a thorough characterization of proso millet amylopectin was reported by Annor, Marcone, Bertoft, and Seetharaman (2014b). The average amylopectin chain length ranged from 18.12 to 20.1 for nonwaxy varieties (Annor et al., 2014b; Yang et al., 2019). However, though not specified, it is likely that these studies used different varieties that could have contributed to the observed differences (18.12 in the study of Annor et al.…”

“…[2014b] and 19.2 vs. 20.1 for waxy and nonwaxy proso millet amylopectin in the study by Yang et al. [2019]).…”

“…Amylopectin molecules from waxy varieties were characterized by higher weight‐average molar mass (17 vs. 2.4×10 7 g/mol) and degree of branching (4.2 vs. 2.8% for waxy vs. regular, respectively), but lower average chain length, than amylopectin in starch of regular proso millet (Yang et al., 2019). Waxy proso millet starches had significantly higher phosphorus contents than regular proso millet or corn starch (Chao et al., 2014), which would enhance starch functionality (i.e., swelling, gelatinization, and pasting properties) due to electrostatic repulsion between the negatively charged groups (Ramadan & Sitohy, 2020).…”