Structure, morphology, and assembly behavior of kafirin

Alkali-assisted extraction, characterization and encapsulation functionality of enzymatic hydrolysis-resistant prolamin from distilled spirit spent grain

Curcumin is a natural lipophilic polyphenol that exhibits significant various biological properties such as antioxidant and anti-inflammatory properties following oral administration. However, its uses have shown limitations concerning aqueous solubility, bioavailability and biodegradability that could be improved by prolamin-based nanoparticle. In this study, curcumin was encapsulated into prolamin from sorghum (SOP) and wheat (WHP) and distilled spirit spent grain (DSSGP), which was obtained after microbial proteolysis of the former two cereal grains. All the three prolamins showed clear variation of protein profiles and microstructure as confirmed by electrophoresis analysis, disulfide bond determination and Fourier-transform infrared spectroscopy (FTIR). For curcumin-loaded nanospheres (NPs) fabrication, three prolamin-based NPs shared features of spherical shape, uniform particle size, and smooth surface. The average size ranged from 122 to 193 nm depending on the prolamin variety and curcumin loading. In the experiments in vitro, curcumin showed significantly improved UV/thermal stability. Furthermore, DSSGP was more resistant to enzymatic digestion in vitro, hence achieving the controlled release of curcumin in gastrointestinal tract. Collectively, the results indicated the improved bioavailability and biodegradability of curcumin encapsulated by DSSGP, which would be an innovative potential encapsulant for effective protection and targeted delivery of hydrophobic compounds.

Effect of a novel drying method based on supercritical carbon dioxide on the physicochemical properties of sorghum proteins

The aim of this research was to use supercritical carbon dioxide (SC-CO2) drying as a novel approach for generating sorghum protein concentrates/isolates with enhanced functional properties. Sorghum protein extracts were obtained from white whole-grain sorghum flour and were dried by two methods, namely, freeze-drying and SC-CO2 drying. The collected proteins were characterized for their morphology, color, crystallinity, surface hydrophobicity, emulsifying activity index (EAI), creaming index (CI), foaming capacity (FC), foaming stability (FS), protein solubility, chemical interactions, and viscosity. The SC-CO2-dried proteins exhibited higher porosity compared to the freeze-dried ones with smaller particle sizes (∼5.1 vs. 0.4 μm, respectively). The XRD patterns indicated that the SC-CO2-dried proteins had a lower crystallinity than the freeze-dried proteins. However, the surface hydrophobicities of the freeze-dried and SC-CO2-dried proteins were similar. The EAI results showed that the emulsifying activity of freeze-dried protein powder (40.6) was better than that of SC-CO2-dried protein powder (29.8). Nevertheless, the solubility of SC-CO2-dried proteins was higher than that of freeze-dried proteins in most of the pHs investigated. Overall, the proposed SC-CO2 drying method has the potential to generate porous protein powders with improved solubility that can be used in developing functional foods.

Plant-Derived Proteins and Peptides as Potential Immunomodulators

The immune response of humans may be modulated by certain biopeptides. The present study aimed to determine the immunomodulatory potential of plant-derived food proteins and hydrolysates obtained from these proteins via monocatalytic in silico hydrolysis (using ficin, stem bromelainm or pepsin (pH > 2)). The scope of this study included determinations of the profiles of select bioactivities of proteins before and after hydrolysis and computations of the frequency of occurrence of selected bioactive fragments in proteins (parameter A), frequency/relative frequency of the release of biopeptides (parameters AE, W) and the theoretical degree of hydrolysis (DHt), by means of the resources and programs available in the BIOPEP-UWM database. The immunomodulating (ImmD)/immunostimulating (ImmS) peptides deposited in the database were characterized as well (ProtParam tool). Among the analyzed proteins of cereals and legumes, the best precursors of ImmD immunopeptides (YG, YGG, GLF, TPRK) turned out to be rice and garden pea proteins, whereas the best precursors of ImmS peptides appeared to be buckwheat (GVM, GFL, EAE) and broad bean (LLY, EAE) proteins. The highest number of YG sequences was released by stem bromelain upon the simulated hydrolysis of rice proteins (AE = 0.0010-0.0820, W = 0.1994-1.0000, DHt = 45-82%). However, antibacterial peptides (IAK) were released by ficin only from rice, oat, and garden pea proteins (DHt = 41-46%). Biopeptides (YG, IAK) identified in protein hydrolysates are potential immunomodulators, nutraceuticals, and components of functional food that may modulate the activity of the human immune system. Stem bromelain and ficin are also active components that are primed to release peptide immunomodulators from plant-derived food proteins.

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.

Effect of High-Hydrostatic-Pressure Treatment on the Physicochemical Properties of Kafirin

The kafirin derived from Jin Nuo 3 sorghum underwent a high-hydrostatic-pressure (HHP) treatment of 100, 300, and 600 MPa for 10 min to investigate alterations in its physicochemical attributes. The findings exhibited a reduction in protein solubility, declining from 83% to 62%, consequent to the application of the HHP treatment. However, this treatment did not lead to subunit-specific aggregation. The absorption intensity of UV light diminished, and the peak fluorescence absorption wavelength exhibited a shift from 342 nm to 344 nm, indicating an increased polarity within the amino acid microenvironment. In an aqueous solution, the specific surface area expanded from 294.2 m2/kg to 304.5 m2/kg, while the average particle-size value in a 70% ethanol solution rose to 26.3 nm. Conversely, the zeta-potential value decreased from 3.4 mV to 1.3 mV, suggesting a propensity for aggregation in ethanol solutions. A notable rise in the intermolecular β-sheet content to 21.06% was observed, along with a shift in the peak denaturation temperature from 76.33 °C to 86.33 °C. Additionally, the content of disulfide bonds increased to 14.5 μmol/g. Collectively, the application of the HHP treatment not only enhanced the thermal stability but also induced a more ordered secondary structure within the kafirin.

Ultrasonic and homogenization: An overview of the preparation of an edible protein-polysaccharide complex emulsion

Emulsion systems are extensively utilized in the food industry, including dairy products, such as ice cream and salad dressing, as well as meat products, beverages, sauces, and mayonnaise. Meanwhile, diverse advanced technologies have been developed for emulsion preparation. Compared with other techniques, high-intensity ultrasound (HIUS) and high-pressure homogenization (HPH) are two emerging emulsification methods that are cost-effective, green, and environmentally friendly and have gained significant attention. HIUS-induced acoustic cavitation helps in efficiently disrupting the oil droplets, which effectively produces a stable emulsion. HPH-induced shear stress, turbulence, and cavitation lead to droplet disruption, altering protein structure and functional aspects of food. The key distinctions among emulsification devices are covered in this review, as are the mechanisms of the HIUS and HPH emulsification processes. Furthermore, the preparation of emulsions including natural polymers (e.g., proteins-polysaccharides, and their complexes), has also been discussed in this review. Moreover, the review put forward to the future HIUS and HPH emulsification trends and challenges. HIUS and HPH can prepare much emulsifier-stable food emulsions, (e.g., proteins, polysaccharides, and protein-polysaccharide complexes). Appropriate HIUS and HPH treatment can improve emulsions' rheological and emulsifying properties and reduce the emulsions droplets' size. HIUS and HPH are suitable methods for developing protein-polysaccharide forming stable emulsions. Despite the numerous studies conducted on ultrasonic and homogenization-induced emulsifying properties available in recent literature, this review specifically focuses on summarizing the significant progress made in utilizing biopolymer-based protein-polysaccharide complex particles, which can provide valuable insights for designing new, sustainable, clean-label, and improved eco-friendly colloidal systems for food emulsion. PRACTICAL APPLICATION: Utilizing complex particle-stabilized emulsions is a promising approach towards developing safer, healthier, and more sustainable food products that meet legal requirements and industrial standards. Moreover, the is an increasing need of concentrated emulsions stabilized by biopolymer complex particles, which have been increasingly recognized for their potential health benefits in protecting against lifestyle-related diseases by the scientific community, industries, and consumers.

Formation of phenolic compound-loaded zein films at the air-liquid interface and their controlled release profiles: Effects of the polarity of phenolic compounds

Polyphenols are frequently utilized antioxidants in active packaging and anti-immflamotary bioactives in tissue engineering. Herein, we introduced a novel method for the rapid (<5 s) fabrication of interfacial self-assembled zein films (ZF) at the air-water interface. Polyphenols with different partition coeffient (Log P), namely, curcumin, resveratrol, and quercetin, were simultaneously loaded during the laterally occurred self-assembly process of zein molecules, respectively. Efficient loading and smart regulation over the physical distribution, intramolecule interaction and release profile in ZF were achieved. The main zein-polyphenol interactions exhibited hydrogen bonding and hydrophobic interactions that modulated the surface micromorphology of ZF and the release kinetics of different polyphenols. The log P of polyphenols affected the strength of the interaction of zein molecules, which in turn influenced the sustained release properties of polyphenols. This "bottom-up" strategy offers a novel way to rapidly incorporate and delicate control over the release of polyphenols.

High-Moisture Shear Processes: Molecular Changes of Wheat Gluten and Potential Plant-Based Proteins for Its Replacement

Nowadays, a growing offering of plant-based meat alternatives is available in the food market. Technologically, these products are produced through high-moisture shear technology. Process settings and material composition have a significant impact on the physicochemical characteristics of the final products. Throughout the process, the unfolded protein chains may be reduced, or associate in larger structures, creating rearrangement and cross-linking during the cooling stage. Generally, soy and pea proteins are the most used ingredients in plant-based meat analogues. Nevertheless, these proteins have shown poorer results with respect to the typical fibrousness and juiciness found in real meat. To address this limitation, wheat gluten is often incorporated into the formulations. This literature review highlights the key role of wheat gluten in creating products with higher anisotropy. The generation of new disulfide bonds after the addition of wheat gluten is critical to achieve the sought-after fibrous texture, whereas its incompatibility with the other protein phase present in the system is critical for the structuring process. However, allergenicity problems related to wheat gluten require alternatives, hence an evaluation of underutilized plant-based proteins has been carried out to identify those that potentially can imitate wheat gluten behavior during high-moisture shear processing.

Recent advances in self-assembly behaviors of prolamins and their applications as functional delivery vehicles

Prolamins are a group of storage proteins (zeins, kafirins, hordeins, secalins, gliadins, glutenins, and avenins) found in the endosperm of cereal grains and characterized by high glutamine and proline content. With the high proportion of nonpolar amino acids (40-80%) and peculiar solubility (alcohol (60-90%), acetic acid, and alkaline solutions), prolamins exhibit tunable self-assembly behaviors. In recent years, research practices of utilizing prolamins as green building materials of functional delivery vehicles to improve the health benefits of bioactive compounds have surged due to their attractive advantages (e.g. sustainability, biocompatibility, fabrication potential, and cost-competitiveness). This article covers the recent advances in self-assembly behaviors leading to the fabrication of nanoparticles, fibers, and films in the bulk water phase, at the air-liquid interface, and under the electrostatic field. Different fabrication methods, including antisolvent precipitation, evaporation induced self-assembly, thermal treatment, pH-modulation, electrospinning, and solvent casting for assembling nanoarchitectures as functional delivery vehicles are highlighted. Emerging industrial applications by mapping patents, including encapsulation and delivery of bioactive compounds and probiotics, active packaging, Pickering emulsions, and as functional additives to develop safer, healthier, and sustainable food products are discussed. A future perspective concerning the fabrication of prolamins as advanced materials to promote their commercial food applications is proposed.

In situ thermal modification of kafirin using infrared radiations and microwaves

BACKGROUND

Kafirin is a prolamin protein located in the corneous endosperm of sorghum. The conventional thermal processing of kafirin reduces its solubility, which limits its utilization in the food industry. Therefore, the study was aimed to investigate the effect of in situ thermal modification of kafirin using two different electromagnetic thermal treatments, namely infrared (IR) and microwave (MW) radiation, on the physicochemical, structural, thermal, and antioxidant properties.

RESULTS

The results demonstrated that both the thermal modifications improved yield, purity, and solubility of the kafirin with a decrease in hydrophobicity. However, IR-treated samples showed higher solubility (910.67 g kg^-1 ) and lower hydrophobicity (387.67). The IR modifications also improved the ratio of α helix/β sheets to a great extent. The alterations in the disulfide content were concomitant with the improvement in the thermal stability of kafirin. Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed variations in the band intensities of β- and γ-kafirin, indicating alterations in the kafirin subunits. Morphological examination of kafirin revealed surface withering and agglomeration. Notably, IR treatment improved the antioxidant activity more efficiently (from 32.11% to 74.05%).

CONCLUSION

Although both the IR and MW treatments modified kafirin, the effect seemed to be more pronounced in IR modification. The IR-modified kafirin had better solubility and lesser hydrophobicity than MW-modified kafirin. The physicochemical and structural changes induced by IR treatment improved the biological activity of kafirin, in terms of antioxidant activity. Therefore, it was concluded that the in situ IR modification of kafirin can alter its characteristic properties, improving its potential as a food ingredient. © 2021 Society of Chemical Industry.

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.

Engineering miscellaneous particles from media-milled defatted walnut flour as novel food-grade Pickering stabilizers

Media milling, an efficient and organic solvent-free method without the use of chemical modification, has been developed to engineer novel walnut-based miscellaneous colloidal particles. The defatted walnut flour particles (DWFPs), which were prepared by a novel continuous phase transition extraction method operated under low temperature (i.e., 50-65 °C) followed by 6-h media milling, were spherical shape with an average size of 753.0 ± 27.8 nm. These particles were mainly composed of proteins (55.6 ± 0.2 wt%) and carbohydrates (24.0 ± 0.2 wt%) and demonstrated the ability to form a gel-like network structure in Pickering emulsions (PEs). The visual observation and confocal laser scanning microscopy (CLSM) showed that the PE droplets stabilized by DWFPs had a good stability over a prolonged storage time (i.e., 3-month storage). Increasing particle concentration (c) in aqueous phase led to the increased emulsified phase volume, decreased oil droplet sizes, and increased storage moduli G' for the viscoelastic responses. As the oil volume fraction (ϕ) increased, the emulsified phase volume fraction and droplet size increased while their rheological properties shifted from fluid-like to gel-like behaviors. The method developed in this study is significant in value-added utilization of walnut products and provides a new insight into facile fabrication of stable food-grade Pickering emulsions-based functional foods using miscellaneous particle stabilizers from walnut extracts.

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.

Interaction mechanism of kafirin with ferulic acid and tetramethyl pyrazine: Multiple spectroscopic and molecular modeling studies

Ferulic acid (FA) and tetramethyl pyrazine (TMP) are intrinsic bioactive compounds in baijiu, and kafirin is the major protein of sorghum, which is the raw material of baijiu. In this study, the interactions of kafirin-FA and kafirin-TMP were investigated by multiple spectroscopic and molecular modeling techniques. Fluorescence spectra showed that intrinsic fluorescence of kafirin drastically quenched because of the formations of kafirin-FA and kafirin-TMP complexes. The CD studies indicated that the combination with FA or TMP decreased the α-helix content of kafirin slightly. The shifts and intensity changes of UV-Vis, FTIR and fluorescence spectra confirmed the formations of complexes. Moreover, the molecular docking and molecular dynamics studies showed that hydrophobic interactions and hydrogen bonds played major roles in the formations of kafirin-FA and kafirin-TMP complexes, and the formations of complexes made kafirin structures more compact. This work is of great importance for further quality improvement in baijiu and alcoholic beverages.

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.

Methods for the Modification and Evaluation of Cereal Proteins for the Substitution of Wheat Gluten in Dough Systems

The substitution of wheat gluten in the food industry is a relevant research area because the only known treatment for celiac disease is abstinence from this protein complex. The use of gluten-free cereals in dough systems has demonstrated that the viscoelastic properties of gluten cannot be achieved without the modification of the protein fraction. The quality of the final product is determined by the ability of the modification to form a matrix similar to that of gluten and to reach this, different methods have been proposed and tested. These procedures can be classified into four main types: chemical, enzymatic, physical, and genetic. This article provides a comprehensive review of the most recent research done in protein modification of cereal and pseudocereals for gluten substitution. The reported effects and methodologies for studying the changes made with each type of modification are described; also, some opportunity areas for future works regarding the study of the effect of protein modifications on gluten-free products are presented.

Characteristics of Potential Protein Nutraceuticals of Plant Origin with Antioxidant Activity

This study used selected plant proteins and the tools available in the BIOPEP-UWM database to profile proteins and release antioxidant nutraceuticals from their primary structures. The frequency of the occurrence of fragments with antioxidant activity in a protein sequence (the A parameter) was determined. A simulated monocatalytic proteolysis was carried out using ficin or stem bromelain or pepsin (pH > 2), and the theoretical degree of hydrolysis (DHt) and the frequency (including relative frequency) of the release of fragments with a particular antioxidant activity by a selected enzyme (the AE and W parameters, respectively). Both barley hordoindolines and the protein group of "actins and other rice proteins" were characterised by the best antioxidant potential. On the other hand, among the main analysed cereal protein groups or species, the best nutraceutical sources included kafirins, rice glutelins and α-gliadins. Potentially the most nutraceutical molecules were released by pepsin (HL, VY, PHQ and PWQ biopeptides) from gliadins, but the most analysed proteins were hydrolysed (66% on average) and the DHt for ficin and bromelain amounted to 27% and 31%, respectively. However, based on the calculated AE mean values, it can be concluded that nutraceuticals were more frequently released from rice protein structures (IY and VY biopeptides), and less frequently released from barley and other cereal protein species, which may be of significance in the context of designing nutraceutical food.

Composition and characterisation of kafirin, the dominant protein fraction in grain sorghum

Context Sorghum is an important feed grain for chicken-meat production in Australia. However, it is usually considered inferior to wheat – the foremost feed grain. Kafirin, the dominant protein fraction in sorghum, may be a major contributor to this inferiority due to its negative influence on starch digestion and energy utilisation. Aims The objective of this study was to determine kafirin concentrations in sorghum relative to crude protein and amino acid profiles of both kafirin and total sorghum protein. Methods Concentrations of amino acids and kafirin in 19 Premium Grains for Livestock Program sorghum varieties were quantified. These data were combined with that of up to 14 Poultry Research Foundation sorghum varieties to generate the most exhaustive documentation of its kind. The methodology developed to quantify kafirin concentrations in sorghum is thoroughly described. In addition, essential amino acid profiles in 25 grain sorghums from Australian surveys completed in 1998, 2009 and 2016 were compared statistically. Also, consideration was given to relevant near-infrared spectroscopy predicted data from 992 sorghum varieties from 2014 to 2019. Key results The average kafirin concentration of 48.2 g/kg represented 51.9% of the 92.9 g/kg crude protein (N × 5.81) content in 33 varieties grain sorghum. Kafirin holds a substantial 62.7% share of leucine as the concentration was 8.53 g/kg in kafirin as opposed 13.73 g/kg in total sorghum protein. The proposal was advanced that kafirin contents of local sorghum crops have increased during the past two decades from the 1998, 2009 and 2016 surveys of amino acid profiles in grain sorghum. Conclusions Kafirin concentrations in Australian sorghum crops may have increased over the past two decades, which may be having a negative impact on the performance of broiler chickens offered sorghum-based diets. Implications Breeding programs should be directed towards sorghums with lesser kafirin proportions of sorghum protein and/or modified kafirin protein bodies to enhance the nutritive value of sorghum as a feed grain for chicken-meat production.

Effect of wet and dry milling on the functional properties of whole sorghum grain flour and kafirin

The effect of wet and dry milling on the functional properties of whole sorghum grain flour (SF) and extracted kafirin were assessed. White sorghum landrace was used to prepare two SFs by wet milling (SF1) or dry milling (SF2) and to extract their respective kafirins SK1 and SK2. Protein contents of SK1 and SK2 were 90.07 and 94.23%. Wet milling of SF allowed increasing the oil binding capacity, the least gelling concentration and the instant foam capacity and decreasing the water binding capacity and foam stability. The emulsifying activity index of SF1 and SF2 were in the same range, while emulsion stability was two time higher in SF2. Functional properties of SK1 and SK2 showed an appropriate water binding capacity of 2.20 ± 0.10 and 1.82 ± 0.22 (g water/g dry mater), respectively. Both SK1 and SK2 showed higher oil binding capacity than SF1 and SF2 with no gel and foam formation. The wet milling improved water and oil binding capacities of SK1 by 17 and 5%. The emulsifying activity indexes were approximately similar for SK1 and SK2 with emulsion stability exceeding 60%. Fourier transform infrared spectroscopy of SK1 and SK2 showed that wet milling induced a decrease of α-helical structure and an increase of intermolecular β-sheet and β-turns and no change in the anti parallel β-sheet. This study showed that wet milling could allow extracting kafirin with preserving the most important functional properties of SF and kafirin and could constitute an interesting method for protein recovery and starch isolation.

Facile Dissolution of Zein Using a Common Solvent Dimethyl Sulfoxide

The conformation and stability of zein in solution are closely associated with its solvation process and influence the mechanical properties of the related zein-based materials. In this work, a common solvent dimethyl sulfoxide (DMSO) was used to dissolve zein, rather than solvents frequently used such as aqueous ethanol and acetic acid. It was found that DMSO could dissolve zein readily and the solution was stable for at least 2 weeks. Rheological analysis and small-angle X-ray scattering (SAXS) were employed to characterize the zein DMSO solution. Results of rheological analysis suggested a Huggins coefficient of 0.24, indicating DMSO to be a good solvent for zein. SAXS results revealed that zein adopted an elongated conformation and had dimensions of 2.8 nm × 2.8 nm × 14.8 nm in DMSO solution. Moreover, robust zein films were fabricated from zein DMSO solutions. The content of residual DMSO in the films was determined to be approximately 15 wt % by thermogravimetric analysis, in consistence with the value obtained by other two methods. The film showed a large breaking strain of 320.6% with a considerable breaking stress of 1.9 MPa, yielding a breaking energy of 376.2 MJ/m³. Therefore, the ease of dissolution and good mechanical performance of the final zein-based material make DMSO a potential solvent for fabrication of zein materials, thereby improving the scope of practical applications of zein.

Brewing with malted barley or raw barley: what makes the difference in the processes?

Malted barley is the main source for fermentable sugars used by yeasts in the traditional brewing of beers but its use has been increasingly substituted by unmalted barley and other raw grain adjuncts in recent years. The incorporation of raw grains is mainly economically driven, with the added advantage of improved sustainability, by reducing reliance on the malting process and its associated cost. The use of raw grains however, especially in high proportion, requires modifications to the brewing process to accommodate the lack of malt enzymes and the differences in structural and chemical composition between malted and raw grains. This review describes the traditional malting and brewing processes for the production of full malt beer, compares the modifications to these processes, namely milling and mashing, when raw barley or other grains are used in the production of wort-a solution of fermentable extracts metabolized by yeast and converted into beer, and discusses the activity of endogenous malt enzymes and the use of commercial brewing enzyme cocktails which enable high adjunct brewing.

White zein colloidal particles: synthesis and characterization of their optical properties on the single particle level and in concentrated suspensions

Growing interest in using natural, biodegradable ingredients for food products leads to an increase in research for alternative sources of functional ingredients. One alternative is zein, a water-insoluble protein from corn. Here, a method to investigate the optical properties of white zein colloidal particles is presented in both diluted and concentrated suspensions. The particles are synthesized, after purification of zein, by anti-solvent precipitation. Mean particle diameters ranged from 35 to 135 nm based on dynamic light scattering. The value of these particles as white colorant is examined by measuring their optical properties. Dilute suspensions are prepared to measure the extinction cross section of individual particles and this was combined with Mie theory to determine a refractive index (RI) of 1.49 ± 0.01 for zein particles dispersed in water. This value is used to further model the optical properties of concentrated suspensions. To obtain full opacity of the suspension, comparable to 0.1-0.2 wt% suspensions of TiO2, concentrations of 2 to 3.3 wt% of zein particles are sufficient. The optimal size for maximal scattering efficiency is explored by modeling dilute and concentrated samples with RI's matching those of zein and TiO2 particles in water. The transport mean free path of light was determined experimentally and theoretically and the agreement between the transport mean free path calculated from the model and the measured value is better than 30%. Such particles have the potential to be an all-natural edible alternative for TiO2 as white colorant in wet food products.

Outlook: Sorghum as a feed grain for Australian chicken-meat production

This review is an outlook for sorghum as a feed grain for broiler chickens based on a survey of relevant stake-holders and recent research outcomes. Australian grain sorghum production will probably continue to generate a harvest in the order of 2.5 × 106 t of which some 7.9 × 105 t will be used as a feed grain for poultry and pigs. Feed grains are included primarily to provide energy from starch, but energy utilisation by broiler chickens offered sorghum-based diets is relatively inferior, because of incomplete starch digestion. Kafirin, the dominant protein fraction, 'non-tannin' phenolic compounds and phytate are 3 'starch extrinsic' factors in sorghum that compromise starch digestibility and energy utilisation in broiler chickens offered sorghum-based diets. Kafirin concentrations in 6 sorghum varieties were negatively correlated with metabolizable energy to gross energy (ME:GE) ratios (r = -0.891; P < 0.02) or the efficiency of energy utilisation in broiler chickens. Importantly, kafirin proportions of sorghum protein may be increasing with time in Australia. If so, this represents a fundamental challenge to sorghum breeders which presumably could be met by the development of sorghum varieties with different characteristics, especially in relation to the γ- and β-kafirin fractions. White sorghum varieties contain lower polyphenol concentrations which should be advantageous as concentrations of total phenolic compounds were negatively correlated to ME:GE ratios (r = -0.838; P < 0.04) in 6 sorghum varieties. It would be desirable if more white varieties were to become available. It is suggested that responses to exogenous phytase in birds offered sorghum-based diets would be more robust if sorghum were to contain lower concentrations of kafirin and phenolic compounds. Paradoxically, while better sorghum varieties almost certainly could be developed, it may not necessarily follow that they will command a price premium from poultry and pig producers.