Plasticizers for Protein‐Based Materials

This study presents a practical approach to select plasticizers for proteins. It is a case study on thermoformed wheat gluten, considered here as a model protein, and it involved 30 plasticizer candidates. The approach consisted of selecting plasticisers (30 wt%) based on visual examination, rheological and molding behavior of the dough, and finally tensile data. There was no unique relationship between the torque behavior of the dough and the mechanical properties of the films. Nevertheless, the extensibility and dough analysis indicated that the most promising plasticizers were as follows: glycerol, linear glycols, ethanol amines, diols, and trimethylolpropane. Further, considering also the stiffness, it was concluded that the most efficient plasticisers were those that contained three hydroxyl groups and the linear glycols of intermediate size. Out of those, glycerol stood out as having the highest extensibility and lowest stiffness and strength. In an attempt to predict the mechanical properties of the films based on several physical data of the compounds, it was observed that there was a weak nonlinear relationship between the stiffness/strength and the size (molecular weight/molar volume), polarity and molar refractivity of the compound. The stiffness/strength decreased with an increase in these physical parameters

Are ultrafine submicron sized gliadin fibrous materials suitable as bio-absorbents? Processing and post-treatment derived structures and functional properties

Gliadins were electrospun into ultrafine fibrous membrane-like materials to evaluate their processability and suitability as bio-absorbents. From a wide range of tested protein concentrations and processing conditions, 15 and 20% protein solutions were optimal to produce uniform fibers with size

Clustering and cross-linking of the wheat storage protein ?-gliadin: A combined experimental and theoretical approach

Our aim was to understand mechanisms for clustering and cross-linking of gliadins, a wheat seed storage protein type, monomeric in native state, but incorporated in network while processed. The mechanisms were studied utilizing spectroscopy and high-performance liquid chromatography on a gliadin-rich fraction, in vitro produced alpha-gliadins, and synthetic gliadin peptides, and by coarse-grained modelling, Monte Carlo simulations and prediction algorithms. In solution, gliadins with alpha-helix structures (dip at 205 nm in CD) were primarily present as monomeric molecules and clusters of gliadins (peaks at 650- and 700-s on SE-HPLC). At drying, large polymers (Rg 90.3 nm by DLS) were formed and 13-sheets increased (14% by FTIR). Trained algorithms predicted aggregation areas at amino acids 115-140, 150-179, and 250-268, and induction of liquid-liquid phase separation at P- and Poly-Q-sequences (Score = 1). Simulations showed that gliadins formed polymers by tail-to-tail or a hydrophobic core (Kratky plots and Ree = 35 and 60 for C- and N-terminal). Thus, the N-terminal formed clusters while the C-terminal formed aggregates by disulphide and lanthionine bonds, with favoured hydrophobic clustering of similar/exact peptide sections (synthetic peptide mixtures on SE-HPLC). Mechanisms of clustering and cross-linking of the gliadins presented here, contribute ability to tailor processing results, using these proteins

Green Chemistry to Modify Functional Properties of Crambe Protein Isolate-Based Thermally Formed Films

Proteins are promising precursors to be used in productionof sustainablematerials with properties resembling plastics, although protein modificationor functionalization is often required to obtain suitable productcharacteristics. Here, effects of protein modification were evaluatedby crosslinking behavior using high-performance liquid chromatography(HPLC), secondary structure using infrared spectroscopy (IR), liquidimbibition and uptake, and tensile properties of six crambe proteinisolates modified in solution before thermal pressing. The resultsshowed that a basic pH (10), especially when combined with the commonlyused, although moderately toxic, crosslinking agent glutaraldehyde(GA), resulted in a decrease in crosslinking in unpressed samples,as compared to acidic pH (4) samples. After pressing, a more crosslinkedprotein matrix with an increase in beta-sheets was obtained inbasic samples compared to acidic samples, mainly due to the formationof disulfide bonds, which led to an increase in tensile strength,and liquid uptake with less material resolved. A treatment of pH 10+ GA, combined either with a heat or citric acid treatment, did notincrease crosslinking or improve the properties in pressed samples,as compared to pH 4 samples. Fenton treatment at pH 7.5 resulted ina similar amount of crosslinking as the pH 10 + GA treatment, althoughwith a higher degree of peptide/irreversible bonds. The strong bondformation resulted in lack of opportunities to disintegrate the proteinnetwork by all extraction solutions tested (even for 6 M urea + 1%sodium dodecyl sulfate + 1% dithiothreitol). Thus, the highest crosslinkingand best properties of the material produced from crambe protein isolateswere obtained by pH 10 + GA and pH 7.5 + Fenton, where Fenton is agreener and more sustainable solution than GA. Therefore, chemicalmodification of crambe protein isolates is effecting both sustainabilityand crosslinking behavior, which might have an effect on product suitability

Pasting and gelation of faba bean starch-protein mixtures

Starch and protein are major components in many foods, contributing to nutritional and textural properties. Understanding how the behaviour and interactions of these components contribute to different textures is important. In this study, mixed gel systems were created with different ratios of starch to protein (constant solid content 12%) extracted from faba bean, a promising crop for locally produced plant-based foods in cold climate regions. The mixed starch-protein gels were characterised in terms of pasting, texture and microstructure. Starch-rich mixtures showed higher water binding and water absorption than samples with higher protein content. A tendency for more efficient hydration in starch-rich samples was confirmed by NMR. Iodine affinity appeared to be lower for high-protein samples, particularly at higher temperatures. Mixtures with high starch content also showed higher viscosity during pasting, higher storage modulus throughout gelation, lower tan delta and lower frequency dependence of the final gel. Characterisation by compression tests showed stronger and more elastic gels with increasing starch content. Light microscopy revealed that starch granules were tightly packed, espe-cially at higher starch content, with protein filling the spaces between starch granules. SEM micrographs revealed a network structure with larger pores and thicker strands in samples with higher starch content. Overall, increasing protein content reduced viscosity during pasting and caused softer gels, likely owing to different gelation and hydration properties of starch and protein

Highly porous flame-retardant and sustainable biofoams based on wheat gluten and in situ polymerized silica

Wheat gluten from ethanol production is presented as flame-retardant silica hybrid biofoams for insulation. The porosity of 90% and self-extinguishing nature make them an attractive alternative to petroleum-based foams.</p

Protein Nanofibrils and Their Hydrogel Formation with Metal Ions

Protein nanofibrils (PNFs) have been prepared by whey protein fibrillation at low pH and in the presence of different metal ions. The effect of the metal ions was systematically studied both in terms of PNF suspension gelation behavior and fibrillation kinetics. A high valence state and a small ionic radius (e.g., Sn4+) of the metal ion resulted in the formation of hydrogels already at a metal ion concentration of 30 mM, whereas an intermediate valence state and larger ionic radius (Co2+, Ni2+, Al3+) resulted in the hydrogel formation occurring at 60 mM. A concentration of 120 mM of Na+ was needed to form a PNF hydrogel, while lower concentrations showed liquid behaviors similar to the reference PNF solution where no metal ions had been introduced. The hydrogel mechanics were investigated at steady-state conditions after 24 h of incubation/gelation, revealing that more acidic (smaller and more charged) metal ions induced ca. 2 orders of magnitude higher storage modulus as compared to the less acidic metal ions (with smaller charge and larger radius) for the same concentration of metal ions. The viscoelastic nature of the hydrogels was attributed to the ability of the metal ions to coordinate water molecules in the vicinity of the PNFs. The presence of metal ions in the solutions during the growth of the PNFs typically resulted in curved fibrils, whereas an upper limit of the concentration existed when oxides/hydroxides were formed, and the hydrogels lost their gel properties due to phase separation. Thioflavin T (ThT) fluorescence was used to determine the rate of the fibrillation to form 50% of the total PNFs (t(1/2)), which decreased from 2.3 to ca. 0.5 h depending on the specific metal ions added

Novel bioplastic from single cell protein as a potential packaging material

Microbial treatment of biodegradable wastes not only ensures neutralization of harmful substances such as volatile organic compounds but also enables valorization and bio-circularity within the society. Single cell protein (SCP) is a value-added product that can be obtained from biodegradable waste materials such as food waste via microbial fermentation. In this article, SCP derived from potato starch waste was demonstrated as a viable alternative to existing plant/animal proteins used in the production of films, for example, packaging applications. Flexible glycerol-plasticized SCP films were prepared through compression molding, and tensile tests revealed strength and stiffness similar to other plasticized protein films. The oxygen barrier properties were significantly better compared to the common polyethylene packaging material, but as with other highly polar materials, the SCP material must be shielded from moisture if used in, for example, food packaging. The biodegradation test revealed a similar degradation pattern as observed for a household compostable bag. The results showed that SCP-based bioplastic films can be considered as potential alternative to the existing plant/animal protein films and certain synthetic polymers. An important advantage with these protein materials is that they do not cause problems similar to microplastics

Greenhouse gas emissions of bio-based diapers containing chemically modified protein superabsorbents

Replacing the current mainly fossil-based, disposable, and non-biodegradable sanitary products with sustainable, functional alternatives is an industry priority. Suggested biobased alternatives require evaluation of their actual impact on greenhouse gas (GHG) emissions. We evaluated GHG emissions of biobased baby diapers as the most consumed sanitary product, using a biodegradable functionalized protein superabsorbent polymer (bioSAP) and compared them with currently used fossil-based counterparts. Assessment of the diapers also included estimated GHG emissions from the production of the biobased components, transport, and end-of-life combustion of these items. It was shown that only a few of the biobased diaper alternatives resulted in lower GHG emissions than commercial diapers containing fossil-based materials. At the same time, it was demonstrated that the production of the bioSAP via chemical modification of a protein raw material is the primary GHG contributor, with 78% of the total emissions. Reduction of the GHG contribution of the bioSAP production was achieved via a proposed recycling route of the functionalization agent, reducing the GHG emissions by 13% than if no recycling was carried out. Overall, we demonstrated that reduced and competitive GHG emissions could be achieved in sanitary articles using biobased materials, thereby contributing to a sanitary industry producing disposable products with less environmental pollution while allowing customers to keep their current consumption patterns

How the unuseful can be turned into sustainable and useful: novel potato protein bioplastics with unusual strength

In Southern Sweden the way potato starch is produced creates large amounts of by-product. This by-product consists of potato protein and non-edible compounds, which limits its use as food today. Improved uses of industrial by-product is of high interest for the future, and therefore finding a better use of the potato proteins from potato starch production is needed.Through this collaboration project between the researchers at SLU Alnarp and Lyckeby Starch AB it has been shown that potato proteins are suitable for making potato protein bioplastics. Also, the bioplastics made from these potato proteins have shown unusual strenght and stretchiness, properties that could be suitable for a multi-layered packaging bag for potato chips