Effect of heat processing on selected grain amaranth physicochemical properties

Abstract

Grain amaranth is a pseudocereal with unique agricultural, nutritional, and functional properties. This study was undertaken to determine the effect of different heat-processing methods on physicochemical and nutraceutical properties in two main grain amaranth species, of Amaranthus hypochondriacus L. and Amaranthus cruentus L. Grains were prepared by roasting and popping, milled and analyzed for changes in in vitro protein digestibility, gruel viscosity, pasting characteristics, antioxidant activity, flavonoids, and total phenolics. In vitro protein digestibility was determined using the pepsin-pancreatin enzyme system. Viscosity and pasting characteristics of samples were determined using a Brookfield Viscometer and a Rapid Visco Analyzer, respectively. The grain methanol extracts were analysed for phenolics using spectrophotometry while antioxidant activity was determined using the DPPH (2,2-diphenyl-1-picrylhydrazyl) method. Heat treatment led to a reduction in protein digestibility, the effect being higher in popped than in roasted samples. Viscosities for roasted grain amaranth gruels were significantly higher than those obtained from raw and popped grain amaranth gruels. The results for pasting properties were consistent with the results for viscosity. In both A. hypochondriacus L. and A. cruentus L., the order of the viscosity values was roasted>raw>popped. The viscosities were also generally lower for A. cruentus L. compared to A. hypochondriacus L. Raw samples for both A. hypochondriacus L. and A. cruentus L. did not significantly differ in total phenolic content (TPC), total flavonoid content (TFC), and total antioxidant activity values. Thermal processing led to an increase in TFC and antioxidant activity. However, TPC of heat-processed samples remained unchanged. From the results, it can be concluded that heat treatment enhances antioxidant activity of grain amaranth and causes rheological changes dependent on the nature of heat treatment.

Characterization and nutritional value of precooked products of kiwicha grains (Amaranthus caudatus)

“…In this study, in the raw grain was obtained a lower value of setback (17 BU). Higher values were reported by other researchers which studied two types of grain Amaranth cruentus L. and L. hipochondriacus (Muyonga et al, 2014). According to other authors, the retrogradation of the amaranth starch is small compared to corn and wheat starches, by the low amount of amylose present amaranth grain (Choi et al, 2004;Wilhelm et al, 2002).…”

“…The puffed operation was performed according to the methodology developed by Muyonga et al (2014), with some modifications. An aluminium pan was used to make puffed corns.…”

“…This trend can be explained by the fact that all these attributes are dependent on the pace and level of starch granule disintegration. Samples which register more extensive granule disintegration seem also likely to exhibit a high extent of retrogradation reflected in the values for setback (Muyonga et al, 2014). Table 4 presents the content of nutrients in raw grain, PK and LK.…”

The Role of Dietary Phenolic Compounds in Protein Digestion and Processing Technologies to Improve Their Antinutritive Properties

“…Also, autoclaving of soaked kidney bean have shown to be better than autoclaving of unsoaked seeds (Shimelis and Rakshit ). Roasting has been shown to have a negative effect on IVPD in beans (Nakitto and others ), African breadfruit (Giami and others ), and amaranth (Muyonga and others ). Cooking and autoclaving after soaking in sodium bicarbonate solution almost completely depleted tannins and dramatically increased IVPD in black grams (Rehman and Shah ).…”

Contribution of instant amaranth (Amaranthus hypochondriacus L.)‐based vegetable soup to nourishment of boarding school adolescents

“…However, the soup mixes should be adequately nutritious if they are to contribute to the adolescents’ micro‐ and macronutrient requirements. Among plant foods, amaranth has proved a highly digestible and a better source of protein, carbohydrates, and micronutrients such as minerals (calcium, sodium, and potassium) and vitamins A, E, C, and folic acid (Mburu, Gikonyo, Kenji, & Mwasaru, ; Mnkeni, Masika, & Maphaha, ; Muyonga, Andabati, & Ssepuuya, ). Amaranth and other nutritious food ingredients can thus be used to make a nutritious dry soup mix that is convenient to use by adolescents.…”