Comparative study on composition and functional properties of brewer's spent grain proteins precipitated by citric acid and hydrochloric acid

Brewer's spent grain (BSG) is an abundant agro-industrial residue and a sustainable low-cost source for extracting proteins. The composition and functionality of BSG protein concentrates are affected by extraction conditions. This study examined the use of citric acid (CA) and HCl to precipitate BSG proteins. The resultant protein concentrates were compared in terms of their composition and functional properties. The BSG protein concentrate precipitated by CA had 10% lower protein content, 5.8% higher carbohydrate, and 5.4% higher lipid content than the sample precipitated by HCl. Hydrophilic/hydrophobic protein and saturated/unsaturated fatty acid ratios increased by 16.9% and 26.5% respectively, in the sample precipitated by CA. The formation of CA-cross-linkages was verified using shotgun proteomics and Fourier transform infrared spectroscopy. Precipitation by CA adversely affected protein solubility and emulsifying properties, while improving foaming properties. This study provides insights into the role of precipitants in modulating the properties of protein concentrates.

[Amaranth grain proteins: prospects for use in specialized food products]

Amaranth is a widespread genus of predominantly annual herbaceous plants belonging to the Amaranthaceae family, which is one of the most widely used pseudocereals along with quinoa and buckwheat in nutrition. The aim of the research was to review and analyze the results of the studies on the characteristics of amaranth grain proteins, the effect of various food processing methods on their quality, and the prospects for using amaranth protein hydrolysates in therapeutic nutrition. Material and methods. For the main search for the literature, the PubMed bibliographic database was used, which covers about 75% of the world's medical publications. In addition, Scopus and Web of Science databases and non-commercial search engine Google Scholar were used. The depth of the search was 15 years. Results. The paper presents a brief review of modern approaches for obtaining amaranth protein isolates and concentrates, including the use of a complex of physicochemical methods: grinding, sifting, extraction at high pH values, defatting, ultrafiltration, centrifugation, isoelectric precipitation, and drying of the protein product. A comparative characteristic of amino acid content of protein fractions of pseudocereals is presented. Basically, leucine, isoleucine, and valine are limiting amino acids for the grain protein of various varieties of amaranth. When substantiating and developing modern effective food technologies for processing amaranth grain, the studies dedicated to the evaluation of their impact on the biological value of amaranth protein deserve special attention. Methods of grain fermentation, sprouting, steaming, malting, boiling can be used to increase the bioavailability and digestibility of its ingredients. The results of in vitro and in vivo studies indicate the presence of hypotensive, hypolipidemic and antioxidant activity of the amaranth protein and its hydrolysates what determines the prospects for their use as part of foods for special dietary uses and therapeutic nutrition. An analysis of the scientific publications presented in the review indicates an increase in demand for high-quality gluten-free products and an increase in the range of mass-consumption foods, such as bakery, pasta, flour confectionery, with pseudo-cereals in their composition, including amaranth. Conclusion. The high biological value and technological properties of amaranth protein concentrates/isolates determine the prospects for their use to create a wide range of specialized foods for various purposes.

Genetic dissection of a pericentromeric region of barley chromosome 6H associated with Fusarium head blight resistance, grain protein content and agronomic traits

Fine mapping of barley 6H pericentromeric region identified FHB QTL with opposite effects, and high grain protein content was associated with increased FHB severity. Resistance to Fusarium head blight (FHB), kernel discoloration (KD), deoxynivalenol (DON) accumulation and grain protein content (GPC) are important traits for breeding malting barley varieties. Previous work mapped a Chevron-derived FHB QTL to the pericentromeric region of 6H, coinciding with QTL for KD resistance and GPC. The Chevron allele reduced FHB and KD, but unfavorably increased GPC. To determine whether the correlations are caused by linkage or pleiotropy, a fine mapping approach was used to dissect the QTL underlying these quality and disease traits. Two populations, referred to as Gen10 and Gen10/Lacey, derived from a recombinant near-isogenic line (rNIL) were developed. Recombinants were phenotyped for FHB, KD, DON, GPC and other agronomic traits. Three FHB, two DON and two KD QTLs were identified. One of the three FHB QTLs, one DON QTL and one KD QTL were coincident with the GPC QTL, which contains the Hv-NAM1 locus affecting grain protein accumulation. The Chevron allele at the GPC QTL increased GPC and FHB and decreased DON and KD. The other two FHB QTL and the other DON and KD QTL were identified in the regions flanking the Hv-NAM1 locus, and the Chevron alleles decreased FHB, DON and KD. Our results suggested that the QTL associated with FHB, KD, DON and GPC in the pericentromeric region of 6H was controlled by both pleiotropy and tightly linked loci. The rNILs identified in this study with low FHB severity and moderate GPC may be used for breeding malting barley cultivars.

Predicting grain protein content of field-grown winter wheat with satellite images and partial least square algorithm

Remote sensing has been used as an important means of modern crop production monitoring, especially for wheat quality prediction in the middle and late growth period. In order to further improve the accuracy of estimating grain protein content (GPC) through remote sensing, this study analyzed the quantitative relationship between 14 remote sensing variables obtained from images of environment and disaster monitoring and forecasting small satellite constellation system equipped with wide-band CCD sensors (abbreviated as HJ-CCD) and field-grown winter wheat GPC. The 14 remote sensing variables were normalized difference vegetation index (NDVI), soil-adjusted vegetation index (SAVI), optimized soil-adjusted vegetation index (OSAVI), nitrogen reflectance index (NRI), green normalized difference vegetation index (GNDVI), structure intensive pigment index (SIPI), plant senescence reflectance index (PSRI), enhanced vegetation index (EVI), difference vegetation index (DVI), ratio vegetation index (RVI), Rblue (reflectance at blue band), Rgreen (reflectance at green band), Rred (reflectance at red band) and Rnir (reflectance at near infrared band). The partial least square (PLS) algorithm was used to construct and validate the multivariate remote sensing model of predicting wheat GPC. The research showed a close relationship between wheat GPC and 12 remote sensing variables other than Rblue and Rgreen of the spectral reflectance bands. Among them, except PSRI and Rblue, Rgreen and Rred, other remote sensing vegetation indexes had significant multiple correlations. The optimal principal components of PLS model used to predict wheat GPC were: NDVI, SIPI, PSRI and EVI. All these were sensitive variables to predict wheat GPC. Through modeling set and verification set evaluation, GPC prediction models' coefficients of determination (R2) were 0.84 and 0.8, respectively. The root mean square errors (RMSE) were 0.43% and 0.54%, respectively. It indicated that the PLS algorithm model predicted wheat GPC better than models for linear regression (LR) and principal components analysis (PCA) algorithms. The PLS algorithm model's prediction accuracies were above 90%. The improvement was by more than 20% than the model for LR algorithm and more than 15% higher than the model for PCA algorithm. The results could provide an effective way to improve the accuracy of remotely predicting winter wheat GPC through satellite images, and was conducive to large-area application and promotion.

Nitrogen application is required to realize wheat yield stimulation by elevated CO2 but will not remove the CO2 -induced reduction in grain protein concentration

Elevated CO₂ (eCO₂ ) generally promotes increased grain yield (GY) and decreased grain protein concentration (GPC), but the extent to which these effects depend on the magnitude of fertilization remains unclear. We collected data on the eCO₂ responses of GY, GPC and grain protein yield and their relationships with nitrogen (N) application rates across experimental data covering 11 field grown wheat (Triticum aestivum) cultivars studied in eight countries on four continents. The eCO₂ -induced stimulation of GY increased with N application rates up to ~200 kg/ha. At higher N application, stimulation of GY by eCO₂ stagnated or even declined. This was valid both when the yield stimulation was expressed as the total effect and using per ppm CO₂ scaling. GPC was decreased by on average 7% under eCO₂ and the magnitude of this effect did not depend on N application rate. The net effect of responses on GY and protein concentration was that eCO₂ typically increased and decreased grain protein yield at N application rates below and above ~100 kg/ha respectively. We conclude that a negative effect on wheat GPC seems inevitable under eCO₂ and that substantial N application rates may be required to sustain wheat protein yields in a world with rising CO₂ .

Climate change impact and adaptation for wheat protein

Wheat grain protein concentration is an important determinant of wheat quality for human nutrition that is often overlooked in efforts to improve crop production. We tested and applied a 32-multi-model ensemble to simulate global wheat yield and quality in a changing climate. Potential benefits of elevated atmospheric CO₂ concentration by 2050 on global wheat grain and protein yield are likely to be negated by impacts from rising temperature and changes in rainfall, but with considerable disparities between regions. Grain and protein yields are expected to be lower and more variable in most low-rainfall regions, with nitrogen availability limiting growth stimulus from elevated CO₂ . Introducing genotypes adapted to warmer temperatures (and also considering changes in CO₂ and rainfall) could boost global wheat yield by 7% and protein yield by 2%, but grain protein concentration would be reduced by -1.1 percentage points, representing a relative change of -8.6%. Climate change adaptations that benefit grain yield are not always positive for grain quality, putting additional pressure on global wheat production.

Independent and combined effects of elevated CO2 and post-anthesis heat stress on protein quantity and quality in spring wheat grains

Spring wheat plants were grown under two CO₂ concentrations (380 and 550 μmol mol^-1) and two temperature treatments (ambient and post-anthesis heat stress) to investigate the effects of elevated CO₂ and heat stress on grain protein quality. Contents of protein components, glutenin macropolymers (GMP) and amino acids in grains decreased due to elevated CO₂, while increased by high temperature. The combination of elevated CO₂ and heat stress increased the contents of total protein and albumin, but decreased the contents of gliadin and glutenin, while the content and particle size distribution of GMP as well as the contents of amino acids were not significantly affected. Furthermore, we found that the content and particle size distribution of GMP were not only determined by the contents of proteins and high-molecular-weight glutenin subunits, but also related to the contents of amino acids containing disulfide bonds, which favor the formation of large insoluble polymers.