Structural, thermal, and rheological properties ofAmaranthus hypochondriacusandAmaranthus caudatusstarches

Functional properties of starch cultivars of two Andean grains grown in Bolivia: Amaranth (Amaranthus caudatus) and canihua (Chenopodium pallidicaule)

The functional properties of Andean grain starches of two species, amaranth (Amaranthus caudatus) and canihua (Chenopodium pallidicaule), three cultivars each, were studied. The study focused on chemical composition, pasting properties, thermal properties, water solubility index (WSI), swelling power (SP), and granule morphology. All amaranth starches were waxy starches, with amylose content less than 5 %, which had some differences in chemical composition (p < 0.05). The pasting properties differed between the species, canihua showed more resistance, than amaranth, to heat and shear stress (higher cool paste (CPV) and lower breakdown (BD), ranged between 1250 and 1600 cP and -30 - 10 cP respectively. The amaranth starches presented only similar CPV with 800-1000 cP, while canihua cultivars presented similar PT and BD, and both species presented similar PV, around 1000 cP. Thermal properties (To, Tp, Tc, ΔH, and ΔT) differed among cultivars and species. These differences could be related to the homogeneity molecular structure and content of amylose in canihua cultivars and possibly to genotype factor. Polygonal shapes were the predominant shape of starch granules, ranged 1.0-1.4 μm and 0.8-0.9 μm, for amaranth and canihua starches respectively. Amaranth starches swelled quickly to disintegrate partially at the end, contrary to canihua starches. The thermal and pasting properties were correlated between them. SB, CPV, HPV, CS, were correlated to the content of amylose in canihua starches. One amaranth cultivar was significantly different from the others. Thus, according the functional properties differenced both species and some cultivars in each species. Additionally, the amaranth starch has the potential to be used in the food industry where heat and stress are applied such as extrusion, while canihua starches can be used in desserts or in cosmetic uses, based on their functional properties.

Amaranthus crop for food security and sustainable food systems

MAIN CONCLUSION

This review ascertains amaranth grains as a potent crop for food security and sustainable food systems by highlighting its agricultural advantages, health benefits and applications in the food, packaging, and brewing industry. The global population surge and rapidly transitioning climatic conditions necessitate the maximization of nutritional crop yield to mitigate malnutrition resulting from food and nutrition insecurity. The modern agricultural practices adopted to maximize the yield of the conventional staple crops are heavily contingent on the depleting natural resources and are contributing extensively to the contamination of these natural resources. Furthermore, these agricultural practices are also causing detrimental effects on the environment like rising emission of greenhouse gasses and increased water footprints. To address these challenges while ensuring sustainable nutrient-rich crop production, it is imperative to utilize underutilized crops like Amaranthus. Amaranth grains are gluten-free pseudo-cereals that are gaining much prominence owing to their abundance in vital nutrients and bio-active components, potential health benefits, resilience to adverse climatic and soil conditions, minimum agricultural input requirements, potential of generating income for small holder farmers as well as various applications across the sustainable value chain. However, due to the limited awareness of these potential benefits of the amaranth grains among the consumers, researchers, and policymakers, they have remained untapped. This review paper enunciates the nutritional composition and potential health benefits of the grains while briefly discussing their various applications in food and beverage industries and accentuating the need to explore further possibilities of valorizing amaranth grains to maximize their utilization along the value chain.

Functional, rheological, and microstructural properties of hydrothermal puffed and raw amaranth flour suspensions

The pseudocereal amaranth is commonly used in food as whole puffed grain. To improve the utilization of amaranth, hydrothermally treated suspensions of puffed and raw Amaranthus caudatus flour and their blends were investigated in this study. The suspensions were hydrothermally treated at 20, 50, and 80°C for 1, 5, and 24 h. The blends were treated at 80°C for 1 h. The effect of hydrothermal treatments of the suspensions on their morphological (color, SEM), water-binding, and rheological-functional properties was studied. The puffed amaranth suspensions exhibited cold swelling properties by rapid viscosity increase and significant water absorption properties. It was found that hydrothermal treatment at 80°C for 1 h significantly increased water absorption and viscosity in puffed and raw flour suspensions. However, the puffed suspensions showed significantly higher values in water binding and viscosity. Suspensions of raw amaranth flour showed increasing color differences with increasing temperature. Blends of raw and puffed amaranth flour resulted in a decreasing color change with increasing puffed flour content. Water absorption of the samples increased with an increasing puffed flour content. Raw amaranth flour and the 50/50 (puffed/raw) blend had the lowest, 10/90 and 20/80 (puffed/raw), and showed similar viscosity profiles to suspensions of pure puffed flour.

Are quinoa proteins a promising alternative to be applied in plant-based emulsion gel formulation?

Emulsion gels are structured emulsion systems that behave as soft solid-like materials. Emulsion gels are commonly used in food-product design both as fat replacers and as delivery carriers of bioactive compounds. Different plant-derived proteins like soy, chia, and oat have been used in emulsion gel formulation to substitute fat in meat products and to deliver some vegetable dyes or extracts. Quinoa protein isolates have been scarcely applied in emulsion gel formulation although they seem to be a promising alternative as emulsion stabilizers. Quinoa protein isolates have a high protein content with a well-balanced amino acid profile and show good emulsifying and gelling capabilities. Unlike quinoa starch, quinoa protein isolates do not require any chemical modification before being used. The present article reviews the state of the art in food emulsion gels stabilized with vegetable proteins and highlights the potential uses of quinoa proteins in emulsion gel formulation.

Structural changes of different starches illuminated with linearly polarised visible light

Aqueous suspensions (30% w/w) of spelt, amaranth and wheat starches were illuminated with linearly polarised visible light for 5, 15, 25 and 50 h. For native and illuminated samples, the weight-average molecular weight, the radii of gyration of the starch polysaccharide chains, and the distribution of the amylopectin structural units of the illuminated starches were determined. The susceptibility to α-amylolysis together with the iodine-binding properties and crystalline structure were studied for each of the starch samples. Illumination with linearly polarised visible light indicated changes in the crystalline structure of the polysaccharide chains and led to an increased enzymatic hydrolysis rate constant for the first stage of hydrolysis and final hydrolysis extent. Changes in the molecular structure of the starch indicate that illumination of the starches induced depolymerisation-repolymerisation reactions of starch polysaccharide chains. That rearrangements of the molecular starch structure depend on the illumination time and the botanical source of the starch.

Physicochemical, thermal and structural properties of heat moisture treated common buckwheat starches

Common buckwheat starch modified by heat moisture treatment at different temperatures was analysed for functional, pasting, structural, thermal, gel textural and morphological properties. Heat moisture treatment decreased swelling power, solubility and oil absorption capacity while amplified water absorption capacity of buckwheat starch. Lower whiteness index with higher a* and b* values were observed for treated starches. Modified starches showed increased paste clarity and reduced syneresis. A declining order of paste clarity and freeze-thaw stability of native and treated starches was noticed during storage period. RVA analysis showed reduced viscosities (peak, trough, breakdown, final and setback viscosity) for hydrothermally treated starches. Increased gel hardness was observed for modified starches and starch sample treated at 85 °C produced the hardest gel. FTIR spectrums of native and treated starch samples showed peaks at similar wavenumbers. Micrographs revealed the polygonal shape of native starch granules with flat areas on surface. Increased agglomeration in heat moisture treated starch samples was noticed in scanned images of starches. X-ray diffraction analysis showed 'A' type crystalline pattern in native starch of common buckwheat and no alteration in crystalline pattern due to hydrothermal treatment was observed. Relative crystallinity of native buckwheat starch decreased during heat moisture treatment and the minimum value was recorded for starches treated at 85 °C. Differential scanning calorimetry showed raised gelatinisation temperatures (T_O, T_P and T_C) and reduced ΔH values for hydrothermal treated starches.

Impact of partial replacement of rice with other selected cereals on idli batter fermentation and idli characteristics

Idli is a naturally fermented food, prepared using dehulled black gram dal and parboiled rice. In the first phase of the study, replacement of rice with some underutilized cereals like amaranth and finger millet was carried out at different proportions (25%, 50%, 75% and 100%, w/w) followed by sensory evaluation of the prepared idlis. Idlis prepared with 25% (w/w) replacement of rice with finger millet (25F) were more acceptable than idlis prepared with 25% (w/w) replacement of rice with amaranth (25A). In the second phase of the study, 50% replacement of rice was carried out with cereals in combinations (25% each, w/w) such as amaranth + finger millet (AF), amaranth + sorghum (AS), amaranth + pearl millet (AP), finger millet + sorghum (FS), finger millet + pearl millet (FP) and sorghum + pearl millet (SP), of which FS and FP batter variants were accepted by the panellists and taken ahead for further analysis. Control, 25F, FS and FP batter variants were subjected to various biochemical analysis up to 20 h of fermentation. Replacement of rice in these batter variants led to comparable changes with an increase in the levels of microbial counts, amylase, protease and phytase activities, titratable acidity, reducing sugars, soluble proteins and antioxidant activity during fermentation. A greater reduction in trypsin inhibitor activity (TIA) was also observed. Idlis prepared with replacement of rice by other cereals (25F, FS and FP) resulted in improved textural values and bulk density as compared to control idlis, though the colour was affected.

Thermal, structural and textural properties of amaranth and buckwheat starches

Starches isolated from amaranth and buckwheat were analysed for thermal characteristics, crystallinity, gel textural properties and light transmittance. Buckwheat starch gels were harder with higher chewiness and springiness than amaranth starch gels. Starch from common buckwheat produced the hardest gel and amaranth starch from VL-44 cultivar produced the softest gel. Gelatinisation temperatures of amaranth and buckwheat starches differed significantly and tartary buckwheat starch showed the highest values for T_P and T_C. Buckwheat starches showed lower enthalpy change values than amaranth starches of both the cultivars. X-ray diffractometry confirmed 'A' type crystalline pattern for all tested starch samples and higher relative crystallinity was noticed in amaranth starches than buckwheat starches. Tartary buckwheat exhibited the lowest value of relative crystallinity and amaranth starch of Durga cultivars showed the highest value of relative crystallinity. FTIR spectrums showed band at similar wavenumbers (cm^-1) with varying intensities. A declining order of paste clarity during storage at refrigeration temperature was observed for all starches.

Electrically induced changes in amaranth seed enzymatic activity and their effect on bioactive compounds content after germination

Electric treatment applied to seeds and sprouts can change their phytochemical composition. However, only a handful of studies have investigated the effects of treating seeds with electric current prior to their germination on the enzymatic antioxidant system of their sprouts. The aim of this study was to determine the changes in bioactive compounds and the enzymatic antioxidant activities in seeds and amaranth sprouts under direct electric current (DC) treatments. Amaranth seeds were treated with DC at 500 mA for different periods of time (0, 2, 5, 10 and 30 min) and let sprout (85% RH, 25 ± 2 °C) for 6 days. Significant changes were found in the antioxidant enzymatic activities and in the total content of flavonoids (15.44 ± 0.56 mg RE/gDW) and phenolic compounds (35.87 ± 0.17 mg GAE/gDW) in 6-day-old sprouts from DC-treated seeds in comparison to sprouts form non-treated seeds. The results suggested that DC treatment for short period (5 min) can induce quantitative changes to the enzymatic antioxidant system of amaranth sprouts, thus representing a relatively cost-effective method for enhancing health-improving properties of sprouts.

Effect of grain moisture content during milling on pasting profile and functional properties of amaranth fractions

Evaluation of functional properties of milled fractions of grain amaranth may be useful to decide the end uses of the grain. Hence, pasting profiles of amaranth fractions obtained by milling the grains at different moisture contents were studied in relation with their starch profile and also with their swelling power and solubility indices. It was observed that, for flour fraction, the viscosity parameters were lowest at 14-16 % moisture content. Swelling power and solubility indices of the samples varied as a function of grain moisture content. The middling fraction also showed similar pasting pattern with the variation of grain moisture content. The seed coat fractions showed higher gelatinization temperature compared to that of fine flour and middling fractions. However, starch content of the fine seed coat fraction was comparable with that of the flour and middling fractions. The coarse seed coat fraction showed lower viscosity parameters than the other samples. Viscosity parameters correlated well among themselves while, they did not show significant correlation with the starch content. However, the viscosity parameters showed negative correlation with the soluble amylose content. The study revealed that, the fractions obtained by milling the grains at different moisture content show differential pasting profiles and functional properties.

Physicochemical, pasting, and functional properties of amaranth seed flours: effects of lipids removal

The present work was carried out to evaluate physicochemical (composition, hunter color, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]), pasting, and functional properties (foaming, emulsification, water, and fat absorption capacity) of amaranth full-fat flours from 6 lines/cultivars (AFs), and to see the effects of lipid removal/defatting on these properties. Protein, ash, and lipid content of AFs ranged between 12.5% to 15.2%, 3.0% to 3.5%, and 7.1% to 8.0%, respectively. The flours showed a number of bands between 97 and 7 kDa, with main subunits of approximately 58, 37, 33, 31, 23, and 16 kDa in the SDS-PAGE profiles. The protein content and L* value increased, while b* values decreased following defatting for most of the lines/cultivars. The defatted flours (DAFs) had higher final viscosity and stability (lower breakdown viscosity) as compared to counterpart AFs. The protein profiling of the flours was not affected with the lipid removal/defatting. However, water absorption capacity and foam stability of the flours improved upon defatting. Principal component analysis revealed that pasting temperature was positively related to lipid content, while breakdown viscosity was negatively related to protein content. Foaming properties (capacity and stability) showed negative relationship with lipid content, and positive with protein content, ash content, water, and fat absorption capacity.

PRACTICAL APPLICATION

Amaranth grains are known to have higher amount of proteins and lipids than cereals. Amaranth lipids are rich in unsaturated fatty acids, which are prone to oxidative rancidity. Removal of lipids or defatting of flours may be carried out to enhance product shelf life by preventing undesirable oxidative chain reactions. Therefore, this research was undertaken to see the effects of defatting on the functional properties of amaranth flours. The defatting was a value addition process as it improved the functional properties of the flours.