Improvement of the in vitro protein digestibility of amaranth grain through optimization of the malting process

Physicochemical changes in Amaranthus spp grains, flour, isolated starch, and nanocrystals during germination and malting

Amaranth is a pseudocereal that contains between 50 and 60% starch, gluten-free protein, and essential amino acids. This study investigates the physicochemical changes in Amaranthus spp. grains, flour, isolated starch and nanocrystals during germination and malting. The moisture content increased from 8.9% to 41% over 2 h of soaking. The percentage of germination increased rapidly, reaching 96% after 60 h, a remarkable advantage over other cereals. The nutrient composition varied, including protein synthesis and lipid degradation. Lipid concentration decreased during malting, except for soaking, which increased by 62%. Scanning electron microscopy shows that germination does not cause morphological changes on the outer surface of the grains, while transmission electron microscopy indicates the presence of isolated nanocrystals with orthorhombic crystal structure confirmed by X-ray diffraction. The viscosity profile shows a decrease in peak viscosity. Therefore, amaranth is a potential pseudocereal that can be used as an additive in the production of fermented beverages.

Enrichment and Quantitation of Dipeptidyl Peptidase IV Inhibitory Peptides in Quinoa upon Systematic Malting

Food-derived peptides with an inhibitory effect on dipeptidyl peptidase IV (DPP-IV) can be used as an additive treatment for type 2 diabetes. The inhibitory potential of food depends on technological protein hydrolysis and gastrointestinal digestion, as the peptides only act after intestinal resorption. The effect of malting as a hydrolytic step on the availability of these peptides in grains has yet to be investigated. In this study, quinoa was malted under systematic temperature, moisture, and time variations. In the resulting malts, the DPP-IV inhibition reached a maximum of 45.02 (±10.28) %, whereas the highest overall concentration of literature-known inhibitory peptides was 4.07 μmol/L, depending on the malting parameters. After in vitro gastrointestinal digest, the inhibition of most malts, as well as the overall concentration of inhibitory peptides, could be increased significantly. Additionally, the digested malts showed higher values in both the inhibition and the peptide concentration than the unmalted quinoa. Concerning the malting parameters, germination time had the highest impact on the inhibition and the peptide concentration after digest. An analysis of the protein sizes before and after malting gave first hints toward the origin of these peptides, or their precursors, in quinoa.

Effect of Germination on Seed Protein Quality and Secondary Metabolites and Potential Modulation by Pulsed Electric Field Treatment

Plant-based foods are being increasingly favored to feed the ever-growing population, but these need to exhibit improved nutritional value in terms of protein quality and digestibility to be considered a useful alternative to animal-based foods. Germination is essential for plant growth and represents a viable method through which the protein quality of plants can be further improved. However, it will be a challenge to maintain efficient rates of germination in a changing climate when seeds are sown. In the context of the indoor germination of seeds for food, consumption, or processing purposes, a more efficient and sustainable process is desired. Therefore, novel techniques to facilitate seed germination are required. Pulsed electric fields (PEF) treatment of seeds results in the permeabilization of the cell membrane, allowing water to be taken up more quickly and triggering biochemical changes to the macromolecules in the seed during germination. Therefore, PEF could be a chemical-free approach to induce a stress response in seeds, leading to the production of secondary metabolites known to exert beneficial effects on human health. However, this application of PEF, though promising, requires further research to optimize its impact on the protein and bioactive compounds in germinating seeds.

Amaranth proteins: From extraction to application as nanoparticle-based delivery systems for bioactive compounds

Amaranth proteins can be produced more sustainably than animal proteins, and they have amino acid compositions that are nutritionally balanced, which makes them attractive candidates for various applications in the food and pharmaceutical industries. This article provides an overview of the composition and techno-functional properties of amaranth protein, including its solubility, emulsification, gelation, foaming, and binding properties. These properties play an important role in the use of amaranth proteins for formulating nanoparticle-based delivery systems with good functional attributes. Amaranth proteins have structural and physicochemical properties suitable for fabricating protein-based nanoparticles. These nanoparticles can be used to encapsulate and control the release of bioactive compounds. However, challenges associated with the presence of anti-nutritional factors in amaranth proteins need to be addressed. These antinutrients negatively affect the bioavailability and digestibility of proteins and bioactive compounds. Hence, strategies to mitigate these challenges are discussed, including processing technologies and genetic engineering methods.

Germination and probiotic fermentation: a way to enhance nutritional and biochemical properties of cereals and millets

Probiotics have become increasingly popular as consumers demand balanced nutrition and health benefits from their diet. However, lactose intolerance and allergies to milk proteins may make dairy-based probiotics unsuitable for some individuals. Thus, probiotics derived from cereals and millets have shown promise as an alternative to dairy probiotics. Soaking, germination, and fermentation can reduce the anti-nutritional factors present in cereal grains and improve nutrient quality and bioactive compounds. Biochemical properties of probiotics are positively influenced by fermentation and germination. Thus, the current review provides an overview of the effect of fermentation and germination on the biochemical properties of probiotics. Further, probiotics made from non-dairy sources may prevent intestinal infections, improve lactose metabolism, reduce cholesterol, enhance immunity, improve calcium absorption, protein digestion, and synthesize vitamins. Finally, health-conscious consumers seeking non-dairy probiotic options can now choose from a wider variety of low-cost, phytochemically rich probiotics derived from germinated and fermented cereal grains.

Impact of In Vitro Digestion on the Digestibility, Amino Acid Release, and Antioxidant Activity of Amaranth (Amaranthus cruentus L.) and Cañihua (Chenopodium pallidicaule Aellen) Proteins in Caco-2 and HepG2 Cells

This study evaluated the impact of in vitro gastrointestinal digestion on the digestibility, amino acid release, and antioxidant activity of proteins from amaranth (Amarantus cruentus L.) and cañihua (Chenopodium pallidicaule Aellen). Antioxidant activity was assessed using ORAC, ABTS, DPPH, and cellular antioxidant activity (CAA) assays in human intestinal Caco-2 and hepatic Hep-G2 cell lines. The results showed that amaranth had higher protein digestibility (79.19%) than cañihua (71.22%). In addition, intestinal digestion promoted the release of essential amino acids, such as leucine, lysine, and phenylalanine, in both protein concentrates. Concentrations of amaranth and cañihua proteins, ranging from 0.125 to 1.0 mg mL-1, were non-cytotoxic in both cell lines. At a concentration of 0.750 mg mL-1, simulated gastrointestinal digestion enhanced cellular antioxidant activity. Intestinal digest fractions containing peptides >5 kDa were the principal contributors to CAA in both cell lines. Notably, cañihua proteins exhibited high CAA, reaching values of 85.55% and 82.57% in Caco-2 and HepG2 cells, respectively, compared to amaranth proteins, which reached 84.68% in Caco-2 and 81.06% in HepG2 cells. In conclusion, both amaranth and cañihua proteins, after simulated gastrointestinal digestion, showcased high digestibility and released peptides and amino acids with potent antioxidant properties, underscoring their potential health benefits.

Physicochemical Properties and Bacterial Community Profiling of Optimal Mahewu (A Fermented Food Product) Prepared Using White and Yellow Maize with Different Inocula

Mahewu is a fermented food product from maize, commonly consumed in Southern Africa. This study investigated the effect of optimizing fermentation (time and temperature) and boiling time of white maize (WM) and yellow maize (YM) mahewu, with the use of the Box–Behnken-response surface methodology (RSM). Fermentation time and temperature as well as boiling time were optimized and pH, total titratable acidity (TTA) and total soluble solids (TSS) determined. Results obtained showed that the processing conditions significantly (p ≤ 0.05) influenced the physicochemical properties. pH values of the mahewu samples ranged between 3.48–5.28 and 3.50–4.20 for YM mahewu and WM mahewu samples, respectively. Reduction in pH values after fermentation coincided with an increase in TTA as well as changes in the TSS values. Using the numerical multi-response optimisation of three investigated responses the optimal fermentation conditions were observed to be 25 °C for 54 h and a boiling time of 19 min for white maize mahewu and 29 °C for 72 h and a boiling time of 13 min for yellow maize mahewu. Thereafter white and yellow maize mahewu were prepared with the optimized conditions using different inocula (sorghum malt flour, wheat flour, millet malt flour or maize malt flour) and the pH, TTA and TSS of the derived mahewu samples determined. Additionally, amplicon sequencing of the 16S rRNA gene was used to characterise the relative abundance of bacterial genera in optimized mahewu samples, malted grains as well as flour samples. Major bacterial genera observed in the mahewu samples included Paenibacillus, Stenotrophomonas, Weissella, Pseudomonas, Lactococcus, Enterococcus, Lactobacillus, Bacillus, Massilia, Clostridium sensu stricto 1, Streptococcus, Staphylococcus, Sanguibacter, Roseococcus, Leuconostoc, Cutibacterium, Brevibacterium, Blastococcus, Sphingomonas and Pediococcus, with variations noted for YM mahewu and WM mahewu. As a result, the variations in physicochemical properties are due to differences in maize type and modification in processing conditions. This study also discovered the existence of variety of bacterial that can be isolated for controlled fermentation of mahewu.

Effects of Germination and Popping on the Anti-Nutritional Compounds and the Digestibility of Amaranthus hypochondriacus Seeds

Amaranth seeds, although a valuable food in Mexico, contain anti-nutritional compounds that can affect food quality. As a part of this work, the proximate composition, fatty acid profile, protein digestibility, and the effect of germination and popping of Amaranthus hypochondriacus seeds was analyzed with the aim of eliminating anti-nutritional compounds. Untreated seeds comprised of 11.35–18.8% protein and 0.27–13.39% lipids, including omega 3, 6, and 9 fatty acids such as oleic, linoleic, linolenic, and arachidonic acid. The main minerals detected were Ca⁺², K⁺¹, and Mg⁺². Nevertheless in vitro studies indicate that germination significantly improved digestibility, whereby treatments aimed at reducing anti-nutritional compounds decreased lectin concentration, while significantly increasing tannins and completely eliminating trypsins and saponins.

Utilization of Amaranthus spp. grains in food

Recently there has been a rediscovery of some ancient crops due to increased consumer demands for a healthier diet with medicinal and therapeutic effects. One such crop is a pseudocereal Amaranthus sp., which is nutritionally more favourable than many widespread kinds of cereal and meets most of the requirements of modern diets. The incorporation of amaranth species in food formulations would expand the assortment of food products present on the market. The high nutritional quality and potential functionality of amaranth-based food products have been the subject of extensive scientific research. This study aims at reviewing the currently available data on the application of amaranth grains in the food industry and manufacturing and focuses on the functionalities of these products, providing an overview of the current amaranth value chain.

Utilization of Amaranthus spp. grains in food

Recently there has been a rediscovery of some ancient crops due to increased consumer demands for a healthier diet with medicinal and therapeutic effects. One such crop is a pseudocereal Amaranthus sp., which is nutritionally more favourable than many widespread kinds of cereal and meets most of the requirements of modern diets. The incorporation of amaranth species in food formulations would expand the assortment of food products present on the market. The high nutritional quality and potential functionality of amaranth-based food products have been the subject of extensive scientific research. This study aims at reviewing the currently available data on the application of amaranth grains in the food industry and manufacturing and focuses on the functionalities of these products, providing an overview of the current amaranth value chain.

In vitro Bioaccessibility of Proteins, Phenolics, Flavonoids and Antioxidant Activity of Amaranthus viridis

The aim of this study was to investigate the chemical composition, mineral content and report the effect of gastrointestinal digestion on the proteins, phenolics, flavonoids and antioxidant activity of morphological parts of Amaranthus viridis (AV). The macronutrients found in the greatest quantity were proteins (leave, inflorescence and seeds) and fiber (roots and stem). The main minerals were calcium, potassium, iron and zinc. All the plant parts showed total phenolic (TPC) and total flavonoid (TFC) compounds that were correlated with antioxidant capacity (DPPH, ABTS and FRAP); the leaves and inflorescence presented the greatest potential. The antioxidant compounds from the leaves, inflorescence and roots decreased after static in vitro digestion, while the TPC and TFC of the digested seeds increased by more than 55%. Approximately 90% of the protein content was bioaccessible. To the best of our knowledge, for the first time, the bioaccessibility of proteins, phenolics, flavonoids and antioxidant activity of the leave, inflorescence, seeds, roots and stem from AV were reported. Taking into consideration the excellent nutritional properties, the morphological parts of the plant can be potentially explored as a source of protein, fiber, minerals and antioxidant compounds.

Relationship of Cultivated Grain Amaranth Species and Wild Relative Accessions

Amaranthus is a genus of C4 dicotyledonous herbaceous plants, and three New World species have been domesticated to produce grain crops with light colored seed which are classified as pseudo-cereals rich in protein and minerals. A core collection of grain amaranths and immediate precursor species has been established, representing the closest related species. The goal of this study was to evaluate the genetic diversity in that collection of cultivated and wild species, using competitive allele single nucleotide polymorphism markers. A secondary objective was to determine the relationships among the three cultivated species and non-domesticated Amaranthus, while a third objective was to evaluate the utility of the markers in detecting diversity in the 276 genotypes. The markers were found to be highly variable with an average polymorphism information content of 0.365. All markers were bi-allelic; and the major allele frequency ranged from 0.388 to 0.871. Population structure analysis of the cultigens revealed the presence of two sub populations. Phylogeny confirmed that the two Mesoamerican species, Amaranthus cruentus and Amaranthus hypochondriacus, were related and distant from the South American species Amaranthus caudatus, which in turn was very closely clustered with Amaranthus quitensis, even though this is considered a weedy relative. The first pair of species were likely to have inter-crossed, while the latter two likely exist in a wild-cultivated hybrid state. In conclusion, the results of this SNP study provided insights on amaranth cultivars and their relationship to wild species, the probable domestication events leading to the cultivars, and possible crop breeding or germplasm conservation strategies.

Millet: A review of its nutritional and functional changes during processing

Millets are a major source of human food, and their production has been steadily increasing in the last decades to meet the dietary requirements of the increasing world population. Millets are an excellent source of all essential nutrients like protein, carbohydrates, fat, minerals, vitamins, and bioactive compounds. However, the nutrients, bioactive compounds, and functions of cereal grains can be influenced by the food preparation techniques such as decortication/dehulling, soaking, germination/malting, milling, fermentation, etc. This study discusses the nutritional and functional changes in millet during different traditional/modern processing techniques, based on more than 100 articles between 2013 and 2020 from Web of Science, Google Scholar, FAO, and USDA databases. Our results concluded that processing techniques could be useful to combat undernourishment and other health issues. Moreover, this review provides detailed information about millet processing, which is advantageous for industry, consumers, and researchers in this area.

Efficacy of germination and probiotic fermentation on underutilized cereal and millet grains

Abstract

Cereals and millets have been known as poor man’s crops for a long time, and have good potential in the mercenary system of food and in research and development but these coarse grains have been leftover and underutilised since a long time. In addition to nutritional properties, various elements of cereal grains contain phenolic compounds as well as various anti-nutritional factors. To improve the nutritional quality and availability of these grains, they are processed in several ways. This review discusses the effect of pre-processing techniques such as germination with a combination of probiotic fermentation on various components of underutilised coarse cereals and millets and advantages it brings into the final product. Germinated food mixture usually contains a significantly higher amount of thiamine, lysine and niacin contents. The combination of cereals with other methods results in better nutrient profile and an enhanced amino acid pattern. Fermentation is said to be the most crucial and popular process which considerably lowers the antinutrients present in coarse cereals such as trypsin inhibitor, phytic acid and tannins and hence, enhance the overall nutritive value of coarse cereals and other food grains. Also, germinated cereal-based food products have higher cell count and better growth of beneficial bacteria, thus, germination of cereals facilitates the probiotic fermentation of cereals.

Graphical abstract

Healthy and Resilient Cereals and Pseudo-Cereals for Marginal Agriculture: Molecular Advances for Improving Nutrient Bioavailability

With the ever-increasing world population, an extra 1.5 billion mouths need to be fed by 2050 with continuously dwindling arable land. Hence, it is imperative that extra food come from the marginal lands that are expected to be unsuitable for growing major staple crops under the adverse climate change scenario. Crop diversity provides right alternatives for marginal environments to improve food, feed, and nutritional security. Well-adapted and climate-resilient crops will be the best fit for such a scenario to produce seed and biomass. The minor millets are known for their high nutritional profile and better resilience for several abiotic stresses that make them the suitable crops for arid and salt-affected soils and poor-quality waters. Finger millet (Eleucine coracana) and foxtail millet (Setaria italica), also considered as orphan crops, are highly tolerant grass crop species that grow well in marginal and degraded lands of Africa and Asia with better nutritional profile. Another category of grains, called pseudo-cereals, is considered as rich foods because of their protein quality and content, high mineral content, and healthy and balance food quality. Quinoa (Chenopodium quinoa), amaranth (Amaranthus sp.), and buckwheat (Fagopyrum esculentum) fall under this category. Nevertheless, both minor millets and pseudo-cereals are morphologically different, although similar for micronutrient bioavailability, and their grains are gluten-free. The cultivation of these millets can make dry lands productive and ensure future food as well as nutritional security. Although the natural nutrient profile of these crop plant species is remarkably good, little development has occurred in advances in molecular genetics and breeding efforts to improve the bioavailability of nutrients. Recent advances in NGS have enabled the genome and transcriptome sequencing of these millets and pseudo-cereals for the faster development of molecular markers and application in molecular breeding. Genomic information on finger millet (1,196 Mb with 85,243 genes); S. italica, a model small millet (well-annotated draft genome of 420 Mb with 38,801 protein-coding genes); amaranth (466 Mb genome and 23,059 protein-coding genes); buckwheat (genome size of 1.12 Gb with 35,816 annotated genes); and quinoa (genome size of 1.5 Gb containing 54,438 protein-coding genes) could pave the way for the genetic improvement of these grains. These genomic resources are an important first step toward genetic improvement of these crops. This review highlights the current advances and available resources on genomics to improve nutrient bioavailability in these five suitable crops for the sustained healthy livelihood.

Emerging opportunities in exploring the nutritional/functional value of amaranth

Amaranthusspp. is a highly nutritive pseudocereal, rich in macronutrients and micronutrients, including vitamins and minerals.

Optimization of the malting process for nutritional improvement of finger millet and amaranth flours in the infant weaning food industry

Malting is a beneficial approach to improve the nutritional value of cereals used in infant preparations. Malted finger millet and amaranth might be considered as potentially appropriate gluten-free alternatives for common wheat-based weaning products, especially in case of those suffering from celiac disease. In this study, the effects of germination temperature and duration on the main nutrients of malted finger millet and amaranth, are evaluated and optimized. Grains were germinated for 24, 36 and 48 h at 22, 26 and 30 °C. In the case of finger millet, germinating for 48 h at 30 °C resulted into 17% increase in protein availability, 10% increase in total energy and 60% reduction in resistant starch (RS). For amaranth, germinating for 48 h at 26 °C was preferable, resulting in 8% increase in protein availability, 11% increase in total energy, 70% reduction in RS and a 10% increase in the linoleic acid.

Malting process optimization for protein digestibility enhancement in finger millet grain

Finger millet (Eleusine coracana) is a nutritious, gluten-free, and drought resistant cereal containing high amounts of protein, carbohydrate, and minerals. However, bio-availability of these nutrients is restricted due to the presence of an excessive level of anti-nutrient components, mainly phytic acid, tannin, and oxalate. It has been shown that a well-designed malting/germination process can significantly reduce these anti-nutrients and consequently enhance the nutrient availability. In the present study, the effects of two important germination factors, duration and temperature, on the enhancement of in-vitro protein digestibility of finger millet were thoroughly investigated and optimized. Based on a central composite design, the grains were germinated for 24, 36, and 48 h at 22, 26, and 30 °C. For all factor combinations, protein, peptide, phytic acid, tannin, and oxalate contents were evaluated and digestibility was assessed. It was shown that during the malting/germinating process, both temperature and duration factors significantly influenced the investigated quantities. Germination of finger millet for 48 h at 30 °C increased protein digestibility from 74 % (for native grain) up to 91 %. Besides, it notably decreased phytic acid, tannin, and oxalate contents by 45 %, 46 %, and 29 %, respectively. Linear correlations between protein digestibility and these anti-nutrients were observed.