Kafirin structure and functionality

Effect of fermentation with selected lactic acid bacteria strains on the molecular and technological properties of sorghum batters

This study provides an in-depth investigation of the relationship between fermentation-induced molecular changes and techno-functional properties of sorghum flour, using three lactic acid bacteria (LAB) strains - Lactobacillus delbrueckii subsp. bulgaricus 1932, Leuconostoc spp. 4454, and Lacticaseibacillus casei 4339. Fermentation at 25 °C for 15 h induced significant molecular changes, including the reduction of low molecular weight fractions (∼0.7 kDa), and depolymerization of starch and fiber (HPSEC analysis). Proton mobility and relaxation analyses (1H LR-NMR) revealed matrix breakdown and stronger water-biopolymer interactions. These molecular changes were closely associated with improved technological properties, including enhanced starch gelatinization (higher enthalpy changes, DSC) and better pasting properties. Changes in structure and molecular interactions likely contributed to the increased viscosity of sorghum, even in the absence of exopolysaccharide production. This study bridges the gap between molecular-level transformations with functional outcomes, providing insights into tailoring fermentation processes for the development of sustainable and innovative sorghum-based foods.

Multiresponse Surface Optimization of Ionic Gelation Vibrational Jet Flow Technology to Fine-Tune Kafirin Microparticles Extracted From Sorghum Dried Distiller's Grain

Sorghum dried distiller's grain with solubles (DDGS), a protein-enriched byproduct of sorghum bioethanol production, is predominantly used as a low-cost animal feed. However, unutilized DDGS is mainly discarded as waste, containing approximately 40% of the prolamin protein kafirin. Kafirin's high hydrophobicity, low digestibility, evaporation-induced self-assembly, and strong disulfide cross-linking offer potential for biomaterial applications. This study used ethanol extraction and acid precipitation to purify kafirin protein from sorghum DDGS. The extracted protein was then used to prepare microparticles using ionic gelation vibrational jet flow technology (IGVJFT). This technology enables reproducible, uniform, scalable, high-speed microparticle production compared to existing methodologies. The integrated electrode voltage (V), internal frequency/vibration (Hz), and DDGS kafirin concentration (% [w/v]) used in the IGVJFT process were evaluated against key microparticle physicochemical response factors of volume-weighted mean microparticle size (% [w/v]), zeta potential (mV), and fracture frequency (mechanical strength) (%). Optimization of microparticle formation was performed by a response surface methodology (RSM) central composite design. Under different processing parameters of the RSM, the resulting DDGS kafirin microparticles possessed spherical morphology, volume-weighted mean particle sizes from 406.7 to 656.4 µm, zeta potential in the range of -38.2 to -18.1 mV, and fracture frequency (mechanical strength) of 23%-57%. Optimal conditions for producing microparticles with minimal size, high negative zeta potential, and low fracture frequency were identified and validated. These findings highlight the potential of DDGS kafirin as a sustainable material for large-scale microparticle applications and demonstrate the efficacy of IGVJFT for assembling hydrophobic proteins into microparticles with tailored physicochemical properties.

Prolamin-pectin complexes: Structural properties, interaction mechanisms and food applications

Prolamin, a class of plant protein mainly derived from grains, and pectins, complex-structured polysaccharides, are natural biological macromolecules with versatile functional properties. The interactions between prolamins and pectin have been widely studied and applied, demonstrating that both covalent and non-covalent interactions play pivotal roles in the formation of prolamin-pectin complexes. These interactions impart exceptional physicochemical and functional properties to the complexes. This review also details the main applications of prolamin-pectin complexes, including emulsions, nanoparticles, hydrogels and films. The similarities in their reaction principles are based on the interaction of complexes that improve their physicochemical and functional properties, while the difference lies in the specific modes of action, involving the emulsifying properties, self-assembly properties, gelling properties and film-forming properties of prolamin and pectin. By delving into the intricate mechanisms underlying prolamin-pectin interactions and their diverse applications in the food industry, this review offers valuable insights for advancing the development and utilization of these complexes.

The Antinutritional Factors and Technological Processing of Sorghum and Its Application in Pig Production

Sorghum ranks as the fifth largest grain crop globally, and it has similar levels of crude protein and leucine compared to corn, making it a viable substitute for full or partial corn in pig diets. Sorghum is produced around the world like corn, which is the energy source in pig diets. However, sorghum contains antinutritional factors that adversely affect nutrient absorption, energy, and amino acid availability. Additionally, the low content of essential amino acids, such as lysine (Lys) and methionine (Met), limits its feeding value. Consequently, this paper primarily discusses the antinutritional factors present in sorghum and elaborates on methods to enhance the nutritional value of forage sorghum through processes such as crushing, extrusion, and enzymatic hydrolysis. The nutritional value of sorghum could be improved by adding protease, by extrusion, and by reducing the grain size. Furthermore, this paper summarizes the application of sorghum in pig production to enhance the understanding of forage sorghum among feed enterprises and to provide a theoretical reference for the rational formulation of pig diets.

Optimization of enzymatic production of anti-skin aging biopeptides from white sorghum [Sorghum bicolor (L) Moench] grain

Recently, kafirins from white sorghum [Sorghum bicolor (L) Moench] grain have shown promise as a source of biopeptides with anti-skin aging effects (anti-inflammatory, antioxidant, and inhibition of photoaging-associated enzymes). This study employed response surface methodology (RSM) to optimize the extraction and enzymatic hydrolysis of kafirins (KAF) for the production of peptides with anti-skin aging properties. The optimization of conditions (reaction time and enzyme/substrate ratio) for liquefaction with α-amylase and hydrolysis of KAF with alcalase was performed using 32 complete factorial designs. Subsequently, ultrafiltered peptide extracts were obtained with molecular weights of 1-3 kDa (KAF-UF3) and lower than 1 kDa (KAF-UF1), which mainly contain hydrophobic amino acids (proline, leucine, isoleucine, phenylalanine, and valine) and peptide fractions with molecular weights of 0.69, 1.14, and 1.87 kDa. Consequently, the peptide extracts protected immortalized human keratinocytes (HaCaT cells) from ultraviolet B radiation (UVB)-induced damage by preventing the decrease and/or restoring the activity of antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px)]. Furthermore, KAF-UF3 and KAF-UF1 inhibited (20-29%) elastase and collagenase overactivity in UVB-exposed murine fibroblasts (3T3 cells). Thus, KAF-UF3 and KAF-UF1 exhibited behavior similar to that observed with glutathione (GSH), suggesting their potential as functional peptide ingredients in skincare products.

Preparation, characterization, stability and functional properties of andrographolide loaded kafirin/carboxymethyl cellulose composite particles using antisolvent precipitation method

Enhancing the oral bioavailability of hydrophobic nutraceuticals and protecting bioactive components through encapsulation systems has gained significant attention in food science. This study explored the preparation and characterization of kafirin (Kaf)/carboxymethyl cellulose (CMC) composite nanoparticles for encapsulating andrographolide (AG) using the antisolvent precipitation method. The optimal Kaf to CMC mass ratio was identified as 4:1, resulting in nanoparticles with an average diameter of 146.4 nm. CMC markedly improved the water dispersibility of the nanoparticles compared to Kaf alone. The formation of these composite nanoparticles was mainly driven by hydrophobic interactions, hydrogen bonding, and electrostatic interactions. Compared to Kaf nanoparticles, the Kaf/CMC nanoparticles showed enhanced encapsulation efficiency, gastrointestinal release characteristics, and stability. Additionally, AG-loaded composite nanoparticles showed exhibited superior biological safety and anti-cancer effects, highlighting their potential for therapeutic applications. In conclusion, Kaf/CMC composite nanoparticles present a promising delivery system for hydrophobic nutraceuticals and drugs, contributing to advancements in drug delivery technologies and nutraceutical formulations.

Prolamin and prolamin-polysaccharide composite nanoparticles for oral drug and nutrient delivery systems: A review

Prolamin-based nanoparticles, particularly those composed of prolamin-polysaccharide composites, have garnered significant interest as oral delivery systems in recent research. This review provides a thorough analysis of the current advancements in these composite nanoparticles with prolamins derived from various cereals, including maize, wheat, sorghum, and millet, with a focus on their applications in oral drug delivery. It discusses the mechanisms by which these composites enhance nanoparticle performance, especially in terms of stability. The review also explores the differences among various prolamins and clarifies the reasons for their performance characteristics as encapsulants for nanoparticles. Additionally, it offers an in-depth examination of various preparation methods for these composite nanoparticles, such as the traditional anti-solvent method, pH-driven method, and several innovative techniques. The study highlights the physicochemical and encapsulation properties of these composite nanoparticles and underscores their novel applications, which hold promise for future use in the food and pharmaceutical sectors. The findings aim to support the integration of prolamin-polysaccharide composites into these industries, ultimately accelerating the development of new applications for these nanoparticles.

Enzymatic production and physicochemical and functional properties of sorghum protein isolates

Grain sorghum has emerged as a promising source for producing alternative proteins, yet current extraction methods lack efficiency. In this study, a novel enzymatic approach using α-amylase and cellulase on sorghum materials was developed to address this challenge. Comparisons were made among the proteins isolated from dry-milled sorghum flours, wet-milled sorghum gluten meals, and sorghum dried distiller's grains (DDG). Remarkably, proteins obtained from sorghum gluten meals demonstrated the highest protein purity (83-85 %) and recovery rate (92-93 %), followed by those from sorghum flour (purity 75-76 %) and DDG (purity 45-50 %). Physicochemical properties and functionalities of the isolated sorghum proteins were analyzed and compared with common commercial plant proteins (e.g., soy protein isolate, pea protein isolate, and wheat gluten). Sorghum proteins exhibited higher levels of crude fat content, α-helix, and random coil structures, along with higher surface hydrophobicity and oil holding capacity (OHC) compared to the commercial plant protein isolates. Notably, proteins extracted from sorghum flours displayed slightly higher α-helix and random coil structures, total sulfhydryl content, water holding capacity (WHC), OHC, and protein digestibility compared to proteins isolated from sorghum gluten meals. Overall, this study demonstrates that enzymatic processing is feasible in producing sorghum proteins and provides insights into their basic properties and functionalities.

Novel mode of kafirin modification using combination of enzyme and thermal treatment to expand its food application

Kafirin in sorghum inhibits starch digestion and exhibits antioxidant properties, however its potential in food industry remains unexplored. Therefore, the study was aimed to explore and improve the potential of kafirin as natural carbohydrate blocker using papain (6 NFU/mL) and/or infrared treatment (220 °C/3 min). Results indicated that the combined treatment, PIR (infrared + papain) is the most efficient treatment to modify kafirin. PIR generated a new ∼37 kDa high molecular weight moiety in kafirin with a crystal size of 157.44 Å. All samples showed superior antioxidant activity post-treatments, with PIR exhibiting highest scavenging activity from 31.09 to 82.97%, 15.09 to 42.82%, and 25.92 to 38.58% for DPPH, FRAP, and ABTS, respectively. PIR-modified kafirin limited malondialdehyde production, and increased α-amylase and α-glucosidase inhibition. Incorporation of 7.5% kafirin in corn starch increased resistant starch from 5.09 to 21.04% after cooking, which suggests potential of kafirin in development of diabetic-friendly food formulations.

Dhurrin in Sorghum: Biosynthesis, Regulation, Biological Function and Challenges for Animal Production

Sorghum (Sorghum bicolor) holds a significant position as the fifth most vital cereal crop globally. Its drought resistance and robust biomass production, coupled with commendable nutritional value, make sorghum a promising choice for animal feed. Nevertheless, the utilization of sorghum in animal production faces hurdles of dhurrin (a cyanogenic glycoside) poisoning. While dhurrin serves as a protective secondary metabolite during sorghum growth, the resulting highly toxic hydrogen cyanide poses a significant threat to animal safety. This review extensively examines the biometabolic processes of dhurrin, the pivotal genes involved in the regulation of dhurrin biosynthesis, and the factors influencing dhurrin content in sorghum. It delves into the impact of dhurrin on animal production and explores measures to mitigate its content, aiming to provide insights for advancing research on dhurrin metabolism regulation in sorghum and its rational utilization in animal production.

Transcriptome and metabolome analyses reveal regulatory networks associated with nutrition synthesis in sorghum seeds

Cereal seeds are vital for food, feed, and agricultural sustainability because they store and provide essential nutrients to human and animal food and feed systems. Unraveling molecular processes in seed development is crucial for enhancing cereal grain yield and quality. We analyze spatiotemporal transcriptome and metabolome profiles during sorghum seed development in the inbred line 'BTx623'. Morphological and molecular analyses identify the key stages of seed maturation, specifying starch biosynthesis onset at 5 days post-anthesis (dpa) and protein at 10 dpa. Transcriptome profiling from 1 to 25 dpa reveal dynamic gene expression pathways, shifting from cellular growth and embryo development (1-5 dpa) to cell division, fatty acid biosynthesis (5-25 dpa), and seed storage compounds synthesis in the endosperm (5-25 dpa). Network analysis identifies 361 and 207 hub genes linked to starch and protein synthesis in the endosperm, respectively, which will help breeders enhance sorghum grain quality. The availability of this data in the sorghum reference genome line establishes a baseline for future studies as new pangenomes emerge, which will consider copy number and presence-absence variation in functional food traits.

Advances in Extraction, Structure, and Physiochemical Properties of Sorghum Kafirin for Biomaterial Applications: A Review

Kafirin is an endosperm-specific hydrophobic protein found in sorghum grain and the waste by-product from sorghum biorefineries known as sorghum dried distillers' grain with solubles (DDGS). Because of kafirin's poor nutritional profile (negative nitrogen balance, slow digestibility, and lack of some essential amino acids), its direct human use as a food is restricted. Nevertheless, increased focus on biofuel production from sorghum grain has triggered a new wave of research to use sorghum DDGS kafirin as a food-grade protein for biomaterials with diverse applications. These applications result from kafirin's unique chemical nature: high hydrophobicity, evaporation-induced self-assembling capacity, elongated conformation, water insolubility, and low digestibility. Aqueous alcohol mixtures have been widely used for the extraction of kafirin. The composition, structure, extraction methodologies, and physiochemical properties of kafirin, emphasising its biomaterial functionality, are discussed in detail in this review. The literature survey reveals an in-depth understanding of extraction methodologies and their impact on structure functionality, which could assist in formulating materials of kafirin at a commercial scale. Ongoing research continues to explore the potential of kafirin and optimise its utilisation as a functional biomaterial, highlighting its valuable structural and physicochemical properties. Further studies should focus on covering gaps in the research as some of the current structural understanding comes from data on zein protein from maize.

Reverse Micelles Extraction of Prolamin from Baijiu Jiuzao: Impact of Isolation Process on Protein Structure and Morphology

Prolamins, proteins derived from plants, have extensive applications in pharmaceutics and food science. Jiuzao is a byproduct of the Baijiu brewing industry, and is a great source of prolamin. Despite its importance, knowledge regarding the extraction techniques and the properties of prolamin derived from Baijiu Jiuzao (PBJ) remains limited. Reverse micelles (RMs) extraction offers an efficient and cost-effective method for purifying proteins. In the present study, prolamin was extracted from Baijiu Jiuzao using RMs extraction and subsequently characterized in terms of its secondary structure, morphology, and particle size distribution. Our findings indicate that the purified prolamin extracted using further RMs extraction possessed higher α-helix content (+13.25%), forming a large-scale protein network, and narrower particle size distributions compared to the crude prolamin obtained by NaOH-ethanol method. This research suggests that RMs extraction has potential applications in extracting prolamin from brewing industry byproducts, offering an environmentally friendly approach to Baijiu Jiuzao recycling.

Transgenic, high-protein sorghums display promise in poultry diets in an initial comparison

This study aimed to compare the inclusion of transgenic sorghums against commercially available sorghums on growth performance in broiler chickens. Isonitrogenous and isoenergetic diets were offered to a total 288 male Ross 308 broiler chickens from 14 to 35 d posthatch. Three dietary treatments were diets based on transgenic sorghums with a mean protein content of 154.7 g/kg and 5 treatments were based on commercially available sorghum hybrids with a mean protein content of 90.6 g/kg. Soybean meal inclusions in the commercial sorghum diets averaged 215 g/kg, which was reduced to 171 g/kg in the transgenic sorghum diets because of the higher protein contents. Overall growth performance was highly satisfactory, and commercial sorghums supported 2.55% (2,330 vs. 2,272 g/bird; P = 0.010) more weight gains and 2.74% (2,929 vs. 2,851 g/bird; P = 0.012) higher feed intakes; however, the transgenic sorghums supported a fractionally better FCR (1.255 vs 1.257; P = 0.826). There were no statistical differences in apparent jejunal and ileal starch and protein (N) digestibility coefficients between treatments. The transgenic sorghum diets generated slightly, but significantly, higher AME:GE ratios and AMEn, but the commercial sorghum diets generated 6.33% (235 vs. 221 g/kg; P < 0.001) greater breast meat yields. Apparent ileal digestibility coefficients of 16 amino acids averaged 0.839 and 0.832 for transgenic and commercial sorghum-based diets, respectively, without any significant differences in individual amino acids. This outcome suggests amino acid digestibilities of the transgenic sorghums may be inherently higher than commercial hybrid sorghums as the 25.7% higher average soybean meal inclusions would have advantaged amino acid digestibilities in commercial sorghum diets. The possibility that the digestibilities of amino acids in the kafirin component of transgenic sorghums was enhanced by modifications to the structure of kafirin protein bodies is discussed. In conclusion, transgenic sorghums with higher protein concentrations led to 20.5% reduction of soybean meal inclusions in broiler diets, and this change did not compromise feed conversion efficiency compared to standard commercial hybrid sorghums.

Effect of fortifying sorghum and wheat with Longhorn grasshopper (Ruspolia differens) powder on nutritional composition and consumer acceptability of biscuits

This study aimed at improving the nutrient composition and protein quality of biscuits made from sorghum and wheat through fortification with Longhorn Ruspolia differens powder (RDP) for use as a supplementary food targeting children vulnerable to protein-energy malnutrition (PEM). Ten biscuit formulations were prepared by replacing a part of wheat and sorghum-wheat flours with 5, 15, 20, and 40% RDP. To establish the nutrient content of biscuits, proximate and mineral compositions were determined. The amino acid composition, reactive lysine and in vitro protein digestibility were determined for protein quality. Compositing wheat or wheat-sorghum biscuits with RDP increased the protein, fat, ash, and crude fiber by percentages as high as 118, 37, 133, and 573%, respectively. Mineral content increased with, iron, zinc, and potassium as high as 161, 219, and 169%, respectively. The lysine, reactive lysine and in vitro protein digestibility of the fortified biscuits increased significantly, relative to the 100% cereal biscuits. Fortification with RDP significantly improved the amino acid content of the biscuits but had a marginal effect on improvement of the lysine score and did not meet the reference pattern for children aged 3-10 years. The Protein Digestibility Corrected Amino Acid Score (PDCAAS) of wheat-sorghum and wheat biscuits improved by 6% to 47% and 2% to 33%, respectively, compared to the control biscuits. The fortified biscuits were liked by the consumers. The RDP-fortified biscuits have the potential to alleviate PME in developing countries.

Investigating sorghum protein solubility and in vitro digestibility during seed germination

In this work, we examined the impact of sorghum gain germination on kafirins solubility and digestibility. Two genotypes differing in their proteins and tannins contents were germinated under controlled conditions up to radicle emergence. Biochemical, physicochemical, and in vitro digestibility tests were applied on the germinated grains. Microscopic examination of grains endosperm revealed that germination resulted in pitted starch granules and protein matrix slackening. Apart cystine and the amount of free thiol groups which increased significantly, the overall amino acids composition remained rather unchanged, just as the kafirins solubility and size distribution. In contrast germination was demonstrated to improved significantly the in vitro protein digestibility, even after cooking and especially for the genotype poor in tannin. Without inducing major physicochemical changes, germination enhanced kafirins susceptibility to gastrointestinal proteases. Germination may be a way to improve the nutritional value of sorghum.

Improvement of sorghum-wheat blended flours by E-beam irradiation: Physicochemical properties, rheological behavior, microstructure, and quality properties

To enhance the processing suitability of blended flours, this study used 4 kGy E-beam irradiated (EBI) sorghum flour in different ratios blended with wheat flour and further verified the improvement mechanism of the processed products under the optimal ratios. The results suggested that the EBI can mitigate the deterioration of the blend flour farinograph properties while enhancing the gas release during dough fermentation. Under the same addition ratio, the irradiated blend flours showed higher expansion height, gas release, cavitation time, and gas retention coefficient than the control flours. Also, irradiated blend flours retained a gluten network at a higher addition rate (20 %). Moreover, the irradiated blend flours were optimized at 10 % as its pasting and thermal properties were improved. Notably, this ameliorating effect promotes a decrease in hardness and chewiness and an increase in cohesion of the bread cores, presenting better textural attributes and delaying the aging rate during storage. The findings are instructive for applying EBI technology in the manufacture and quality improvement of mixed grain breads and open a new research avenue for processing sorghum staple foods.

Applications of Prolamin-Based Edible Coatings in Food Preservation: A Review

Foods are susceptible to deterioration and sour due to external environmental influences during production and storage. Coating can form a layer of physical barrier on the surface of foods to achieve the purpose of food preservation. Because of its good barrier properties and biocompatibility, prolamin-based film has been valued as a new green and environment-friendly material in the application of food preservation. Single prolamin-based film has weaknesses of poor toughness and stability, and it is necessary to select appropriate modification methods to improve the performance of film according to the application requirements. The practical application effect of film is not only affected by the raw materials and the properties of the film itself, but also affected by the selection of preparation methods and processing techniques of film-forming liquid. In this review, the properties and selection of prolamins, the forming mechanisms and processes of prolamin-based coatings, the coating techniques, and the modifications of prolamin-based coatings were systematically introduced from the perspective of food coating applications. Moreover, the defects and deficiencies in the research and development of prolamin-based coatings were also reviewed in order to provide a reference for the follow-up research on the application of prolamin-based coatings in food preservation.

Fabrication and characterization of bio-nanocomposites based on kafirin and polyethylene oxide as auxiliary polymer: process optimization, rheological, morphological and thermal properties

The aim of this research was to compare the effects of various solvents on producing kafirin/polyethylene oxide (PEO) bio-nanocomposites by the technique of electrospinning. Different concentrations of kafirin (15, 20, 25, 30 and 40% w/v) and PEO (2, 4 and 6% w/v) were electrospun. For the dissolution and electrospinning of these two biopolymers, different solvents were used comparatively, i.e. distilled water, ethanol (70%), acetic acid (40%), 2-Butanol and glacial acetic acid. An evaluation of flow behavior showed that kafirin and PEO had Newtonian and pseudoplastic behaviors, respectively. A mixture of these two polymers demonstrated quasi-Newtonian and shear-independent behaviors in a low shear rate range, which positively affected the electrospinning process. SEM images showed that the best concentrations of kafirin and PEO were 25 and 2%, respectively, for producing nanofibers with uniform structures. Fourier-transform infrared spectroscopy (FTIR) indicated the presence of kafirin and PEO in the bio-nanocomposite after electrospinning. The FTIR proved that these two polymers had no chemical interactions with each other. Overall, the results showed that selecting an appropriate solvent and a suitable auxiliary polymer could have significant roles in producing biodegradable kafirin nanofibers.

Graphical abstract

Determination and Analysis of Composition, Structure, and Properties of Teff Protein Fractions

To develop teff-based food products with acceptable quality, the composition, structure, and properties of teff protein fractions should be better understood. In this study, teff proteins were extracted, and their protein composition, structure, and properties were calculated, analyzed, and compared with those of wheat gliadin and glutenin. Results showed that teff flour contained 9.07% protein, with prolamin as its main protein fraction. The isoelectric points of albumin, globulin, prolamin, and glutelin were at pH 3.6, 3.0, 4.4, and 3.4, respectively. Teff prolamin and glutelin showed a significant difference in amino acids and free energy of hydration compared to wheat gliadins and glutenins. The protein chain length of teff prolamins was smaller than that of wheat gliadins, and teff glutelins lacked high molecular weight glutelin subunits. Teff prolamin had the highest α-helices content (27.08%), whereas no random coils were determined, which is different from wheat gliadin. Teff glutelin had a lower content of β-turn than wheat glutenin, and no α-helices were determined in it. Teff prolamin and glutelin had lower disulfide bond content and surface hydrophobicity. Teff prolamin had significantly higher thermal stability than wheat gliadin, whereas the thermal stability of teff glutelin was significantly lower than that of wheat glutenin.

Sorghum grain germination as a route to improve kafirin digestibility: Biochemical and label free proteomics insights

Kafirin, the sorghum grain storage protein presents lower digestibility compared to its cereals counterparts. Germination has been proposed as an adequate bioprocessing method to improve seed protein digestibility. Here, germination was rationalized so as to evenly sample germinated seeds and the dynamic changes of the proteome and several biochemical markers was connected for the first time with the in vitro protein digestibility of germinated seeds. Free sulfhydryl groups increased during germination and in vitro protein digestibility enhanced. The dynamic in abundance of several enzymes out of which 3 cysteine proteases were found to coincide with appearance of aqueous soluble peptides derived from kafirin at boot time of their degradation. The study provides deep information about the molecular events occurring during sorghum seed germination and reveals potential biomarkers of the kafirin proteolysis. It points a way to improve sorghum nutritional value through controlled germination.

Variations in Total Protein and Amino Acids in the Sequenced Sorghum Mutant Library

Sorghum (Sorghum bicolor) is the fifth most important cereal crop worldwide; however, its utilization in food products can be limited due to reduced nutritional quality related to amino acid composition and protein digestibility in cooked products. Low essential amino acid levels and digestibility are influenced by the composition of the sorghum seed storage proteins, kafirins. In this study, we report a core collection of 206 sorghum mutant lines with altered seed storage proteins. Wet lab chemistry analysis was conducted to evaluate the total protein content and 23 amino acids, including 19 protein-bound and 4 non-protein amino acids. We identified mutant lines with diverse compositions of essential and non-essential amino acids. The highest total protein content in these lines was almost double that of the wild-type (BTx623). The mutants identified in this study can be used as a genetic resource to improve the sorghum grain quality and determine the molecular mechanisms underlying the biosynthesis of storage protein and starch in sorghum seeds.

Effect of protein-starch interactions on starch retrogradation and implications for food product quality

Starch retrogradation is a consequential part of food processing that greatly impacts the texture and acceptability of products containing both starch and proteins, but the effect of proteins on starch retrogradation has only recently been explored. With the increased popularity of plant-based proteins in recent years, incorporation of proteins into starch-based products is more commonplace. These formulation changes may have unforeseen effects on ingredient functionality and sensory outcomes of starch-containing products during storage, which makes the investigation of protein-starch interactions and subsequent impact on starch retrogradation and product quality essential. Protein can inhibit or promote starch retrogradation based on its exposed residues. Charged residues promote charge-dipole interactions between starch-bound phosphate and protein, hydrophobic groups restrict amylose release and reassociation, while hydrophilic groups impact water/molecular mobility. Covalent bonds (disulfide linkages) formed between proteins may enhance starch retrogradation, while glycosidic bonds formed between starch and protein during high-temperature processing may limit starch retrogradation. With these protein-starch interactions in mind, products can be formulated with proteins that enhance or delay textural changes in starch-containing products. Future work to understand the impact of starch-protein interactions on retrogradation should focus on integrating the fields of proteomics and carbohydrate chemistry. This interdisciplinary approach should result in better methods to characterize mechanisms of interaction between starch and proteins to optimize their food applications. This review provides useful interpretations of current literature characterizing the mechanistic effect of protein on starch retrogradation.

Large and stable genome edits at the sorghum alpha kafirin locus result in changes in chromatin accessibility and globally increased expression of genes encoding lysine enrichment

INTRODUCTION

Sorghum is a resilient and widely cultivated grain crop used for feed and food. However, it's grain is deficient in lysine, an essential amino acid. This is due to the primary seed storage proteins, the alpha-kafirins, lacking lysine. It has been observed that reductions in alpha-kafirin protein results in rebalancing of the seed proteome and a corresponding increase in non-kafirin proteins which leads to an increased lysine content. However, the mechanisms underlying proteome rebalancing are unclear. This study characterizes a previously developed gene edited sorghum line, with deletions at the alpha kafirin locus.

METHODS

A single consensus guide RNA leads to tandem deletion of multiple members of the gene family in addition to the small target site mutations in remaining genes. RNA-seq and ATAC-seq were utilized to identify changes in gene expression and chromatin accessibility in developing kernels in the absence of most alpha-kafirin expression.

RESULTS

Several differentially accessible chromatin regions and differentially expressed genes were identified. Additionally, several genes upregulated in the edited sorghum line were common with their syntenic orthologues differentially expressed in maize prolamin mutants. ATAC-seq showed enrichment of the binding motif for ZmOPAQUE 11, perhaps indicating the transcription factor's involvement in the kernel response to reduced prolamins.

DISCUSSION

Overall, this study provides a resource of genes and chromosomal regions which may be involved in sorghum's response to reduced seed storage proteins and the process of proteome rebalancing.

[Antiproliferative, apoptotic, and antimigratory activities of kafirins on cervical cancer-derived cell lines]

Background

Cervical cancer is one of the leading causes of death in women worldwide, both in developed and developing countries. Therefore, effective treatment of cervical cancer with potential anti-tumor drugs is important. However, new treatments inspired by nutritional medicine are needed.

Objective

To use the human cervical cancer cell lines HeLa and SiHa to evaluate the antiproliferative, apoptotic, and migratory activity of sorghum (kafirins).

Materials and methods

The anticancer effects of the kafirins were examined by counting cells, MTT assays, apoptosis, and migration assays.

Results

This investigation showed that sorghum induced growth inhibition of HeLa and SiHa cells at a significant level. The growth inhibition is dose-dependent and irreversible. When HeLa and SiHa cells were treated with sorghum due to the activity of kafirins, morphological changes were observed, which were identified through the formation of apoptopic bodies. And the kafirins at concentrations of 37.5, 75, 150, and 300 μg/mL decreased the migration of HeLa cells and SiHa cells.

Conclusion

This paper demonstrates the induction of antiproliferative, apoptotic, and anti-migratory activity in HeLa and SiHa cells by kafirins. Sorghum may be used as a nutraceutical with potential cancer-prevention benefits.

Antioxidant activity of kafirin hydrolysates on UVB irradiated human keratinocyte cells and in silico identification

BACKGROUND

Ultraviolet B (UVB) causes photoaging of the skin, the appearance of wrinkles, spots, and alteration of the skin barrier. The main cells in the most superficial layer of the skin are the keratinocytes; these cells play an important role in protecting this organ.

OBJECTIVE

The present study aimed to investigate the antioxidant activity of the hydrolysates from kafirin to inhibit UVB-induced responses in human keratinocytes cells (HaCaT).

METHODS

Kafirin hydrolysates were produced by enzymatic hydrolysis with alcalase. The activity of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPx), in the HaCaT cell line in the presence of UVB and the effects of the hydrolysates against the UVB-induced response were evaluated. Furthermore, the peptides that were generated by hydrolysis were identified in silico using the BIOPEP database.

RESULTS

Two protein sequences were identified (α-kafirin and the precursor protein of α-kafirin), in the kafirin extract. A degree of hydrolysis of 18.8% was obtained by hydrolyzing the kafirin extract with alcalase. The kafirin hydrolysates avoided the decrease in endogenous antioxidant enzymes such as SOD, CAT, and GPx reducing the oxidative stress generated by UVB. Using the BIOPEP-UWM database, we found 102 peptide sequences, and it has shown that the peptides have a large amount of hydrophobic amino acids such as proline, alanine, and glutamine, and amino acids with high antioxidant capacity.

CONCLUSION

These results suggest that the kafirin hydrolysates can be used as antioxidant agents to ameliorate UVB-induced skin keratinocytes cells' response in vitro, providing an alternative against UVB-induced photoaging.

Sorghum in foods: Functionality and potential in innovative products

Sorghum grain is a staple food for about 500 million people in 30 countries in Africa and Asia. Despite this contribution to global food production, most of the world's sorghum grain, and nearly all in Western countries, is used as animal feed. A combination of the increasingly important ability of sorghum crops to resist heat and drought, the limited history of the use of sorghum in Western foods, and the excellent functional properties of sorghum grain in healthy diets, suggests a greater focus on the development of new sorghum-based foods. An understanding of the structural and functional properties of sorghum grain to develop processes for production of new sorghum-based foods is required. In this review, we discuss the potential of sorghum in new food products, including sorghum grain composition, the functional properties of sorghum in foods, processing of sorghum-based products, the digestibility of sorghum protein and starch compared to other grains, and the health benefits of sorghum. In the potential for sorghum as a major ingredient in new foods, we suggest that the gluten-free status of sorghum is of relatively minor importance compared to the functionality of the slowly digested starch and the health benefits of the phenolic compounds present.

CRISPR-knockout of β-kafirin in sorghum does not recapitulate the grain quality of natural mutants

When gene editing was applied to knockout beta-kafirin, there was a compensatory increase of gamma-kafirin which does not occur in domesticated null varieties, so enhanced grain quality was not achieved. Sorghum bicolor is an important animal feedstock cereal crop throughout Australia and the southern United States, where its use as a food product is limited by issues with low calorific and nutritive value. Qualities such as reduced digestibility and low essential amino acid content are directly attributed to the kafirin grain storage proteins, the major components of protein bodies within the endosperm. Specifically, the β- and γ-kafirins have few protease cleavage sites and high levels of cysteine residues which lead to a highly cross-linked shell of intra- and inter-molecular disulphide linkages that encapsulate the more digestible α- and δ-kafirins in the core of the protein bodies. Naturally occurring β-kafirin mutants exist and are known to have improved grain quality, with enhanced protein contents and digestibility, traits which are often attributed to the lack of this cysteine-rich kafirin in the mature grain. However, when CRISPR/Cas9 editing was used to create β-kafirin knockout lines, there was no improvement to grain quality in the Tx430 background, although they did have unique protein composition and changes to protein body morphology in the vitreous endosperm. One explanation of the divergence in quality traits found the lines lacking β-kafirin are due to a drastic increase of γ-kafirin which was only found in the gene edited lines. This study highlights that in some germplasm, there is a level of redundancy between the peripheral kafirins, and that improvement of grain protein digestibility cannot be achieved by simply removing the β-kafirin protein in all genetic backgrounds.

Effect of Bioprocessing on Techno-Functional Properties of Climate-Resilient African Crops, Sorghum and Cowpea

Sorghum and cowpea are very compatible for intercropping in hot and dry environments, and they also have complementary nutritional compositions. Thus, the crops have the potential to improve food security in regions threatened by climate change. The aim of this study was to investigate different enzymes (carbohydrate-degrading, proteases and phytases) and lactic acid bacteria (LAB) fermentation to improve the techno-functional properties of sorghum and cowpea flours. Results show that sorghum carbohydrates were very resistant to hydrolysis induced by bioprocessing treatments. Most of the protease treatments resulted in low or moderate protein solubilization (from ca. 6.5% to 10%) in sorghum, while the pH adjustment to 8 followed by alkaline protease increased solubility to 40%. With cowpea, protease treatment combined with carbohydrate-degrading enzymes increased the solubility of proteins from 37% up to 61%. With regard to the techno-functional properties, LAB and amylase treatment decreased the sorghum peak paste viscosities (from 504 to 370 and 325 cPa, respectively), while LAB and chemical acidification increased cowpea viscosity (from 282 to 366 and 468 cPa, respectively). When the bioprocessed sorghum and cowpea were tested in breadmaking, only moderate effects were observed, suggesting that the modifications by enzymes and fermentation were not strong enough to improve breadmaking.

Modification of zein dough functionality using kafirin as a coprotein

Kafirin, sorghum prolamin, was investigated as a coprotein for zein as visco-elastic masses and in starch-based model doughs. Regular kafirin and kafirins from waxy and high protein digestibility (HD) sorghum crosses were studied. HPLC revealed that waxy-HD kafirin was of smaller molecular size and low in β-kafirin. It also had greater surface hydrophobicity. Kafirin addition to zein increased visco-elastic mass elasticity up to ≈50% stress-recovery, similar to wheat gluten. Waxy-HD kafirin gave the highest elasticity, possibly due to its hydrophobicity. Kafirin inclusion at 2:8 parts zein increased the tensile strength of model doughs. Maximum strength was, however, only 60% that of gluten-based dough. Kafirin from regular sorghum gave the highest strength, possibly because of greater disulphide-bonded polymerisation. Confocal laser scanning microscopy showed that zein-kafirin copolymers formed fairly linear fibrils in stretched doughs, indicating excellent compatibility between the proteins. Future research should establish how kafirin-zein copolymer performs in non-wheat flour products.

Dry heat and pressure favor bioactive compounds preservation and peptides formation in sorghum [S orghum bicolor (L.) Moench]

Sorghum is a cereal with potential economic and nutritional properties. It has gained headway in the international market because of its nutritional content which is characterized for many bioactive compounds with antioxidant characteristics, and also, because it is gluten free. This work evaluated the proteomic profile of sorghum grains and its nutritional composition and functional profile after exposure to 7 different treatments (control, grind, dry heat, bursting, wet cooking with and without water and wet cooking in pressure). They were analyzed for chemical composition, protein profile, total phenolic compounds, anthocyanin content and antioxidant activity. The dry heat preserves the protein content, phenolic compounds, anthocyanins and presents between 94% and 95% of radical scavenging activity. Heat treatments that use the pressure promote the natural hydrolysis of proteins. Bursting treatment resulted in 45.6% of proteins and peptides in the range of 3.7; 5.93; 8.9 and 14 kDa. Wet cooking in pressure (SPC) showed a similar behavior, with 26.8% being the abundance of 14 and 14.3 kDa proteins and 25.3% of the peptides with less than 10 kDa, making up 52.1% of protein content. This hydrolysis promoted an important percentage of peptides and low molecular mass proteins which can have bioactive profile and improve healthy.

Inheritance of the genetic construct for RNA-silencing of the γ-kafirin gene (gKAF1) in the progeny of transgenic sorghum plants

Sorghum is one of the most important cereal crops in drought regions of the Globe. However, a number of constrains, such as poor nutritional value compared to other cereals, which is caused by resistance of its grain storage proteins (kafirins) to protease digestion, makes it less popular. The use of modern genetic technologies, such as RNA interference, opens up prospects for solving this problem. In this paper, we describe the inheritance of the genetic construct for RNAi silencing of the γ-kafirin gene (gKAF1) in the progeny of the mutant Avans-1/18, that we obtained previously by Agrobacterium-mediated genetic transformation of immature embryos of commercial cv. Avans. Inheritance of the genetic construct was traced by PCR-analysis to the nos-promoter governing expression of the marker gene bar and to the ubi1-intron, which is part of the genetic construct for silencing. It was found that the genetic construct inherited in T1 and T2 generations of the mutant grown both in the growth chamber and in the field plot, and in the F1 hybrids of the mutant with CMS-lines A2 KVV-181, A2 KVV-114, A2 O-1237, and fertile lines Volzhskoe-4v, Volzhskoe-615, O-1237. The studied plants from T1 and T2 generations had significantly higher in vitro protein digestibility than original non-transgenic cv. Avans. The vitreous endosperm in these plants was reduced either completely or manifested a faint layer. These data demonstrated that genetic construct for gKAF1 silencing was not only stably integrated in genome of the mutant plants but also expressed and improved the digestibility of endosperm proteins. In addition, in T1 progeny we found the plant, PCR positive for nos-promoter but PCR-negative for ubi1-intron, that had vitreous endosperm and was characterized by poor in vitro protein digestibility. These data are an example of instability of the genetic construct for RNAi-silencing in genome of some transgenic plants; they show close correlation of the floury endosperm type and high in vitro protein digestibility.

Effect of extrusion and turmeric addition on phenolic compounds and kafirin properties in tannin and tannin-free sorghum

Sorghum is a potential substitute for corn/wheat in cereal-based extruded products. Despite agronomic advantages and its rich diversity of phenolic compounds, sorghum kafirins group together and form complex with tannins, leading to a low digestibility. Phenolic content/profile by UPLC-ESI-QTOF-MS^E and kafirins polymerization by SE-HPLC were evaluated in wholemeal sorghum extrudates; tannin-rich (#SC319) and tannin-free (#BRS330) genotypes with/without turmeric powder. Total phenolic, proantocyanidin and flavonoid contents were strongly correlated with antioxidant capacity (r > 0.9, p < 0.05). Extrusion increased free (+60%) and decreased bound phenolics (-40%) in #SC319, but reduced both (-40%; -90%, respectively) in #BRS330, which presented lower abundance after extrusion. Turmeric addition did not significantly impact antioxidant activity, phenolic content and profile and kafirins profile. Tannins presence/absence impacted phenolic profiles and polymerization of kafirins which appears related to the thermoplastic process. The extrusion improved proteins solubility and can positively enhance their digestibility (phenolic compounds-proteins interactions), making more accessible to proteolysis in sorghum extrudates.

Sorghum polyphenols: plant stress, human health benefits, and industrial applications

MAIN CONCLUSION

Various phenolic compounds of sorghum are effective in the management of abiotic stress (salt, nutrients) and biotic stress (caused by birds, fungi and aphids). The health and industrial application of phenolics is mainly contributed by inherent antioxidant and nutraceutical potential. In a natural environment, plant growth is affected by various biotic and abiotic stresses. In every ecosystem, the presence of a wide range of harmful biological agents (bacteria, fungi, nematodes, mites, and insects) and undesirable environmental factors (drought, salinity, heat, excessive or low rainfall, etc.) may cause a heavy loss in crop productivity. Being sessile during evolution, plants have evolved multiple defense mechanisms against various types of microbial pathogens and environmental stresses. A plant's natural defense system produces some compounds named secondary metabolites, which include phenolics, terpenes, and nitrogen. The phenolic profile of grain sorghum, the least utilized staple crop, is unique, more diverse, and more abundant than in any other common cereal grain. It mainly contains phenolic acids, 3-deoxyanthocyanidins and condensed tannins. Sorghum polyphenols play a major role in plant defense against biotic and abiotic stresses and have many additional health benefits along with various industrial applications. The objective of this review is to discuss the phenolic compounds derived from grain sorghum and describe their role in plant defense, human health, and industrial applications.

The effect of sorghum consumption on markers of chronic disease: A systematic review

Sorghum requires fewer inputs for sustainable cultivation in harsh climates and has the potential to be utilized in modern food product innovations. Moreover, consumption of sorghum may elicit favorable health effects similar to other commonly consumed cereals, like wheat. Animal and human research exploring health effects of sorghum consumption indicates potential beneficial effects on blood glucose and lipid regulation, oxidative stress modulation, appetite regulation and weight management. However, a recent appraisal of the strength of evidence has not been conducted. Therefore, this study aims to evaluate the effects of sorghum consumption on metabolic indicators of chronic disease, including blood lipid and blood glucose levels, markers of oxidative stress, and factors associated with weight management. Using CINAHL, Cochrane Library, PubMed and MEDLINE databases, a systematic review of intervention studies published up to May 2020 was conducted and 16 interventional studies met the criteria for inclusion. Evidence for favorable effects of sorghum consumption on indicators of chronic disease, including blood glucose responses, markers of oxidative stress, satiety measures and weight management was demonstrated. Evidence from this systematic review may assist to promote sorghum's potential health benefits globally, including in food markets where it is underutilized, stimulating more sorghum-based food innovations in the future.

Physicochemical characterisation of kafirins extracted from sorghum grain and dried distillers grain with solubles related to their biomaterial functionality

Kafirin, the hydrophobic prolamin storage protein in sorghum grain is enriched when the grain is used for bioethanol production to give dried distillers grain with solubles (DGGS) as a by-product. There is great interest in DDGS kafirin as a new source for biomaterials. There is however a lack of fundamental understanding of how the physicochemical properties of DDGS kafirin having been exposed to the high temperature conditions during ethanol production, compare to kafirin made directly from the grain. An understanding of these properties is required to catalyse the utilisation of DDGS kafirin for biomaterial applications. The aim of this study was to extract kafirin directly from sorghum grain and from DDGS derived from the same grain and, then perform a comparative investigation of the physicochemical properties of these kafirins in terms of: polypeptide profile by sodium-dodecyl sulphate polyacrylamide gel electrophoresis; secondary structure by Fourier transform infra-red spectroscopy and x-ray diffraction, self-assembly behaviour by small-angle x-ray scattering, surface morphology by scanning electron microscopy and surface chemical properties by energy dispersive x-ray spectroscopy. DDGS kafirin was found to have very similar polypeptide profile as grain kafirin but contained altered secondary structure with increased levels of β-sheets. The structure morphology showed surface fractals and surface elemental composition suggesting enhanced reactivity with possibility to endow interfacial wettability. These properties of DDGS kafirin may provide it with unique functionality and thus open up opportunities for it to be used as a novel food grade biomaterial.

Effect of Sorghum on Rheology and Final Quality of Western Style Breads: A Literature Review

Due to the extreme weather conditions, caused by the climate change, the usual wheat harvest yield and quality in the Western countries were difficult to maintain in the past few years. The altered wheat quality was primarily characterized by a rising protein content. The application of high protein wheat flours in baking products leads to baking difficulties due to its elastic dough behavior. As these issues will further face the Western cereal cultivation, heat resistant cereals, like sorghum, are attracting increasing interest. A partial substitution of wheat with sorghum might offer one possible solution to address the current challenging situation. To introduce sorghum in the Western cereal and baking industry, the grain and its unique chemical and rheological properties need to be more widely promoted. Until now, several authors have conducted studies in order to emphasize the high potential of sorghum. The aim of the present review is to broaden the current knowledge of the chemical, rheological and baking properties of sorghum in comparison to wheat. The review further demonstrates promising approaches, which might be from interest in order to achieve higher wheat-sorghum bakery end product qualities.

Genome-wide association analysis reveals seed protein loci as determinants of variations in grain mold resistance in sorghum

GWAS analysis revealed variations at loci harboring seed storage, late embryogenesis abundant protein, and a tannin biosynthesis gene associated with sorghum grain mold resistance. Grain mold is the most important disease of sorghum [Sorghum bicolor (L.) Moench]. It starts at the early stages of grain development due to concurrent infection by multiple fungal species. The genetic architecture of resistance to grain mold is poorly understood. Using a diverse set of 635 Ethiopian sorghum accessions, we conducted a multi-stage disease rating for resistance to grain mold under natural infestation in the field. Through genome-wide association analyses with 173,666 SNPs and multiple models, two novel loci were identified that were consistently associated with grain mold resistance across environments. Sequence variation at new loci containing sorghum KAFIRIN gene encoding a seed storage protein affecting seed texture and LATE EMBRYOGENESIS ABUNDANT 3 (LEA3) gene encoding a protein that accumulates in seeds, previously implicated in stress tolerance, were significantly associated with grain mold resistance. The KAFIRIN and LEA3 loci were also significant factors in grain mold resistance in accessions with non-pigmented grains. Moreover, we consistently detected the known SNP (S4_62316425) in TAN1 gene, a regulator of tannin accumulation in sorghum grain to be significantly associated with grain mold resistance. Identification of loci associated with new mechanisms of resistance provides fresh insight into genetic control of the trait, while the highly resistant accessions can serve as sources of resistance genes for breeding. Overall, our association data suggest the critical role of loci harboring seed protein genes and implicate grain chemical and physical properties in sorghum grain mold resistance.

Sprouting of Sorghum (Sorghum bicolor [L.] Moench): Effect of Drying Treatment on Protein and Starch Features

The nutritional and physicochemical properties of sorghum proteins and starch make the use of this cereal for food production challenging. Sprouting is a cost-effective technology to improve the nutritional and functional profile of grains. Two drying treatments were used after sorghum sprouting to investigate whether the drying phase could improve the protein and starch functionalities. Results showed that the drying treatment at lower temperature/longer time (40 °C for 12 h) extended the enzymatic activity that started during sprouting compared to the one performed at higher temperature/shorter time (50 °C for 6 h). An increased protein hydrolysis and water- and oil-holding capacity were found in the flour obtained by the former treatment. Higher protein matrix hydrolysis caused high exposure of starch to enzymes, thus increasing its digestibility, while worsening the technological functionality. Overall, modulating drying conditions could represent a further way, in addition to sprouting, to improve sorghum flour’s nutritional profile.

Prolamin-based complexes: Structure design and food-related applications

Prolamins are a group of safe food additives that are biocompatible, biodegradable, and sustainable. Zein, gliadin, kafirin, and hordein are common prolamins that have been extensively studied, particularly as these form colloidal particles because of their amphiphilic properties. Prolamin-based binary/ternary complexes, which have stable physicochemical properties and superior functionality, are formed by combining prolamins with polysaccharides, polyphenols, water-soluble proteins, and surfactants. Although the combination of prolamins with other components has received attention, the relationship between the structural design of prolamin-based complexes and their functionalities remains uncertain. This review discusses the production methods of prolamin-based complexes, the factors influencing their structural characteristics, and their applications in the food industry. Further studies are needed to elucidate the structure-function relationships between prolamins and other biopolymers, as well as the toxicological effects of these complexes in food.