Soy Protein Films Research Articles

Biodegradable soy protein films with controllable water solubility and enhanced mechanical properties via graft polymerization

Graft polymerization of acrylic acid endowed soy protein films with good tensile properties and water solubility without sacrificing biodegradability. In this research, soy protein was grafted with acrylic acid and cast into biodegradable films as substitutes of non-biodegradable Poly(vinyl alcohol) (PVA) films. The grafted soy protein films had 318%, 114%, 60% and 9% higher tensile strength, elongation, dissolving rate and transmittance, compared to ungrafted ones, respectively. Acrylic acid grafting provided soy protein films with biodegradability, flexibility, and adhesion to yarns substantially higher than PVA, while water solubility and abrasion resistance similar to PVA, leading to high potential applications of the grafted soy proteins in the fields of water soluble packaging films and slashing to substitute PVA.

Preparation and characterization of soy protein films with a durable water resistance-adjustable and antimicrobial surface

A water resistant surface was first obtained by immobilizing hydrophobic copolymers, poly (styrene-co-glycidyl methacrylate) (PSG), with functional groups on soy protein isolate (SPI) films. XPS and AFM results showed that PSG copolymers were immobilized on the film by chemical bonding, and formed a rough surface with some bumps because of the segregation of two different phases on PSG copolymers. Water resistance of the modified films could be adjusted dramatically by further immobilizing different amounts of guanidine-based antimicrobial polymers, poly (hexamethylene guanidine hydrochloride) (PHMG) on the resulting hydrophobic surface. The introduction of hydrophilic PHMG on the resulting surface generated many micropores, which potentially increased the water uptake of the modified films. Furthermore, the modified SPI films showed higher thermostability compared to native SPI film and broad-spectrum antimicrobial activity by contact killing, attributed to the presence of PHMG on the surface. The modified SPI film with a multi-functional surface showed potential for applications in the packaging and medical fields.

Structure, Functionality, and Active Release of Nanoclay–Soy Protein Films Affected by Clove Essential Oil

Nowadays, there is a pronounced interest in the potential use of biopolymer/layered silicate systems as active food packaging. This manuscript studied the effect of clove essential oil addition to soy protein–montmorillonite (MMT) films on the material’s structure, functionality, and active release. Active nanocomposite films were prepared by casting from aqueous dispersions containing soy protein isolates (SPI), glycerol, different concentrations of MMT and clove essential oil. Besides the important antioxidants and antimicrobial properties provided to nanocomposite films, the addition of clove essential oil exerted a plasticizing effect, which was verified in a decrease in the tensile strength and elastic modulus (up to 50 and 75 %, respectively) and an increase of the water content of films (up to 20 %). But the nanoclay caused a further strengthening effect in films containing CEO. While nanocomposite films containing 10 g MMT/100 g SPI reached an increase of 105 and 200 % in tensile strength and Young’s modulus, respectively, and a decrease of 340 % in their elongation at break, those that also contained CEO reached higher variations (230, 345, and 290 %, respectively). Clove essential oil presence also favored the exfoliation of montmorillonite into the soy protein matrix, while the nanoclay seemed to promote the release of active compounds, occasionally modifying the antimicrobial activity of films as well as the release of some of its Si and Al ions after being in contact with water (at least twice).

The effect of peanut protein nanoparticles on characteristics of protein- and starch-based nanocomposite films: A comparative study

The objective of the current research was to analyze the effects of peanut protein nanoparticles on the characteristics of soy protein and cornstarch films. Peanut protein nanoparticles (PNPs) were fabricated by the anti-solvent method and were incorporated, at a concentration of 0–4%, into soy protein isolate films and cornstarch films. Mechanical, water vapor barrier, thermal stability, and morphological properties of the nanocomposite films were evaluated by scanning electron microscope, texture analyzer, and thermogravimetric analyzer. Compared to untreated films, addition of PNPs at the level ∼4% significantly (p<0.05) improved tensile strength, water vapor barrier, and thermal stability of both protein and starch films. The soy protein films performed best with 2% nanoparticles, especially in mechanical properties, which could be due to the better compatibility between protein matrices and protein nanoparticles.

Thermal and mechanical properties of mandelic acid-incorporated soy protein films

Different contents of mandelic acid (2.5–10 %) were mixed with glycerol-plasticized soy protein isolate (SPI) to prepare mandelic acid incorporated soy protein isolate films. The effects of the mandelic acid content on the morphology and properties of the glycerol-plasticized SPI films were investigated by scanning electron microscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, thermogravimetric analysis, water resistivity and tensile testing. The tensile strength of the mandelic acid incorporated SPI films decreased while elongation at break increased. The results indicated that, at 10 mass% of mandelic acid, strong interactions occurred both between the mandelic acid and the SPI matrix, leading to appearance of endotherms at 148.8 °C. Mandelic acid-incorporated soy protein films were also tested for their antibacterial properties.

Effects of Paraffin Emulsion on the Structure and Properties of Soy Protein Films

In this work, the water-repellent capacity of the paraffin emulsion−covered soy flour (SF) substrate has been studied. Effect of paraffin emulsion content on the structure and properties of the resulting films were studied using laser particle size distribution analyzer, water absorption test, x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and tensile testing. Study on the emulsion particle size and stability revealed that the particle size distribution and stability were strongly dependent on the pH of the system. And the optimum pH was 9.9. The incorporation of paraffin emulsion produced at pH 9.9 could markedly enhance the water resistance of films. However, the improvement was realized at the expense of decreased thermal stability and tensile strength of SF−paraffin emulsion films. The addition of paraffin emulsion could destroy the crystalline domains of soy protein and change the protein secondary structure.

Biodegradable soy wound dressings with controlled release of antibiotics: Results from a guinea pig burn model

There is growing interest in the development of biodegradable materials from renewable biopolymers, such as soy protein, for biomedical applications. Soy protein is a major fraction of natural soybean and has the advantages of being economically competitive, biodegradable and biocompatible. It presents good water resistance as well as storage stability. In the current study, homogenous antibiotic-loaded soy protein films were cast from aqueous solutions. The antibiotic drug gentamicin was incorporated into the films in order to inhibit bacterial growth, and thus prevent or combat infection, upon its controlled release to the surrounding tissue. The current in vivo study of the dressing material in contaminated deep second-degree burn wounds in guinea pigs (n=20) demonstrated its ability to accelerate epithelialization with 71% epithelial coverage compared to an unloaded format of the soy material (62%) and a significant improved epithelial coverage as compared to the conventional dressing material (55%). Our new platform of antibiotic-eluting wound dressings is advantageous over currently used popular dressing materials that provide controlled release of silver ions, due to its gentamicin release profile, which is safer. Another advantage of our novel concept is that it is based on a biodegradable natural polymer and therefore does not require bandage changes and offers a potentially valuable and economic approach for treating burn-related infections.

Crosslinked soy protein films and their application as ophthalmic drug delivery system

In this research, the potential of soy protein (SPI) based-films as drug delivery devices for ocular therapy was developed. Hence, crosslinked films with a natural and non-cytotoxic crosslinking agent, genipin (Gen), coated with poly(lactic acid) (PLA), were prepared. Filmogenic solutions were loaded with timolol maleate (TM) as a model drug, to be used as drug delivery devices, a novel application for this material. The mechanical properties of the films were studied, observing that with the presence of PLA coating, more rigid materials with improved properties were obtained. Furthermore, the release behavior of TM was evaluated in aqueous medium, it being influenced by the degree of film crosslinking. Furthermore, it was determined that PLA coating decreased TM release rate compared to that of uncoated films. Similarly, this behavior was observed via indirect estimation of the release by assessing the hypotensive effectiveness of the films by in-vivo assays. Through intraocular pressure (IOP) determination tests in rabbits, it was demonstrated that, through the use of high crosslinked and coated films, a significant decrease in IOP could be achieved for prolonged time periods. These results suggest that the use of soy protein-based films as drug delivery systems is highly suitable.

Modified soy protein to substitute non-degradable petrochemicals for slashing industry

Additives with multiple hydroxyl groups, nonlinear molecular structure and electric charge, like triethanolamine (TEA), could modify soy protein into effective sizes for high speed weaving of cotton fabrics. Poly(vinyl alcohol) (PVA) sizes are known as the best sizing agent for cotton. However, PVA is poorly biodegradable and is a major contributor to high chemical oxygen demand in textile effluents. Starch sizes have escalating prices and also could not provide cotton yarns with enough protection in high speed weaving or weaving of high-count cotton fabrics as PVA does. Soy protein, extracted from bio-diesel or edible oil byproducts such as soymeal, is highly available, low cost, water soluble, biodegradable, and has limited industrial applications. The major disadvantage of using soy protein as warp sizes is their formation of films with low flexibility, leading to poor size performance and weaving efficiency. In this paper, adding triethanolamine (TEA) substantially improves tensile properties of soy protein films. Industrial weaving results showed TEA-soy protein (TEA-soy) had 36% and 12% higher weaving efficiency for cotton fabrics than modified starch and PVA sizes. In addition, TEA-soy sizes had a 5-day biochemical oxygen demand/chemical oxygen demand ratio of 0.44 compared to 0.03 for PVA indicating that TEA-soy sizes were easily biodegradable in activated sludge. To replace starch and PVA sizes, about 1.2 million tons of soymeal could be used to produce TEA-soy for high quality and high speed weaving, benefiting agriculture, textiles, and environment.

Selective chemical modification of soy protein for a tough and applicable plant protein-based material.

Soy protein, one of the most abundant plant proteins, has gained considerable attention and popularity in recent years due to its biocompatibility, biodegradability, and renewability. However, the poor mechanical properties and high moisture sensitivity of soy protein-based materials have limited their wider application in practical use. In the present study we have overcome these shortcomings by the use of an aqueous reagent, tetrakis(hydroxylmethyl) phosphonium chloride (THPC), to modify the amino groups of the lysine (Lys) and arginine (Arg) residues present in soy protein. Solid state 13C cross polarization/magic-angle spinning nuclear magnetic resonance (CP/MAS NMR) and 31P NMR spectroscopy have confirmed the success of the chemical reaction by replacement of the hydroxymethyl arm of THPC, both qualitatively and quantitatively. Fourier-transform infrared (FTIR) spectroscopy, rheological observations, transmission electron microscopy (TEM) and atomic force microscopy (AFM) have been used to confirm the changes in the coherent tertiary structure of soy protein after modification, increasing the interconnection between the molecular chains. Finally, we have been able to produce a modified soy protein film, which provides a good combination of tensile strength and extensibility under either dry (10 ± 2 MPa and 25 ± 3%) or wet (5 ± 1 MPa and 200 ± 20%) conditions. In addition the modified soy protein film has unexpectedly been found to exhibit antimicrobial properties, and this adds to the merits of the final product. We believe that the method described further broadens the application of natural soy protein-based materials, for example in antimicrobial packaging films.

Mechanical, Optical, and Barrier Properties of Soy Protein Film As Affected by Phenolic Acid Addition.

This study aimed to explore the effect of phenolic acid addition on properties of soy protein film. Ferulic (FE), caffeic (CA), and gallic (GA) acids as well as their oxidized products were used in this study. Phenolic acid addition was found to have a significant effect (p ≤ 0.05) on the mechanical properties of the film. GA-containing films exhibited the highest tensile strength and elongation at break, followed by those with added CA and FE, respectively. Oxidized phenolic acids were shown to produce a film with higher tensile strength and elongation at break than their unoxidized counterparts. Phenolic acid addition also affected film color and transparency. As compared to the control, phenolic-containing film samples demonstrated reduced water vapor permeability and water solubility and increased contact angle, especially at high concentrations of oxidized phenolic acid addition.

Improving wet strength of soy protein films using oxidized sucrose

ABSTRACTThe chemical modification of soy protein isolate (SPI) with various amounts of oxidized sucrose was performed in this study. The poor mechanical properties and lack of hydrolysis resistance of SPI have limited its applications in various fields. Although chemical modification proved to be an effective method to enhance the properties of SPI films, current SPI modifiers are either expensive, toxic, or do not impart the satisfiable properties to the modified materials. In this research, the possibility of modification of SPI films using oxidized sucrose to improve their strength and stability was examined. At optimal conditions, oxidized sucrose‐modified SPI films showed about 50% higher wet strength than the control films. The melting temperature of modified SPI film was 26°C higher than the unmodified control. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 41473.

Development and characterization of soy protein films incorporated with cellulose fibers using a hot surface casting technique

In this study, cellulose-soy protein isolate (SPI) composite films were prepared using a hot surface casting technique. The cellulose microfibrils for the films were extracted from soybean pods and stems using a combined acid-alkaline hydrolysis and high-pressure homogenization treatment. For comparison, TiO2-SPI composite films were also prepared using TiO2 nanoparticles as filler. Mechanical and barrier properties (water vapor, and oxygen permeability) of these files were evaluated under different relative humidity (RH) conditions. In general, tensile strength (TS) and Young's modulus (YM) decreased and elongation at break (EAB) increased with increasing RH. Among the composites tested, the 5 g:95 g fiber:SPI film exhibited significant (p-value < 0.05) improvements in TS and YM but decreased EAB as compared to the neat SPI. By contrast, TiO2 composites possessed similar TS, YM, and EAB values as the control film. Barrier properties were comparable across all samples, and decreased with increasing RH. Samples were characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic force microscopy.

Nanocrystal-reinforced soy protein films and their application as active packaging

Soy protein isolate (SPI) films reinforced with starch nanocrystals (SNC) were developed by simple casting method. The films were transparent and homogeneous. The opacity and degree of crystallinity increased with the amount of nanocrystals. Moisture content, total soluble matter and swelling in water were evaluated, showing a marked effect on SNC additions. As the amount of SNC increased, the films exhibited lower affinity for water. Moreover, mechanical properties were determined showing that SPI-SNC reinforced films became more resistant and less elongable as SNC amount increased. With the incorporation of a considerable amount of reinforcements, a marked variation was observed in these properties. In addition, assays performed demonstrated that β-cyclodextrins (β-CD)-containing SPI-SNC films were able to sequester cholesterol when brought into contact with cholesterol rich food such as milk. This effect was more marked as the amount of β-CD into the films increased. The methodologies developed in this work allowed yielding biodegradable films with optimized physical and mechanical properties which were assayed as active food coating.

Extrusion and Characterization of Soy Protein Film Incorporated with Soy Cellulose Microfibers

Abstract A biodegradable alternative material to synthetic plastics was explored in this study through the extrusion of soy protein isolate (SPI) composite films containing soy cellulose microfibers (SMF). SMF were isolated from soy pods and stems using a chemo-mechanical method. The fibers produced through successive treatments were characterized by microscopy, x-ray diffraction, and Fourier transform infrared analysis. SMF/SPI composite films (0.08 to 0.3 mm thick), containing different concentrations of cellulose fibers, were produced using a single-screw extruder (0.625″ screw; 24 : 1 L/D ratio; 100 – 120 min−1; 120 to 150 °C barrel temperature) and characterized. Homogenous films with uniform distribution of SMF were obtained with the highest concentration of 0.5 % w/w SMF/SPI. Increasing fiber content resulted in the formation of aggregates. As with other protein films, mechanical properties of the extruded pristine SPI and composite films were negatively affected by humidity. At the optimal concentration of 0.25 % w/w SMF/SPI, films exhibited improved mechanical performance at elevated relative humidity (84 %) when compared to the pristine SPI films.

Grafting soyprotein isolates with various methacrylates for thermoplastic applications

Soyprotein isolates were grafted with four different methacrylates and compression molded into films with good dry and wet tensile properties. Soyprotein isolates are obtained as coproducts during soybean processing, have unique properties and have been widely studied for various industrial applications. Although films with properties suitable for various applications have been developed from soyproteins by solution casting, attempts to obtain thermoplastics from soyproteins with high strength and stability under aqueous environments have not been successful. In this research, soyproteins were grafted with methyl methacrylate (MMA), ethyl methacrylate (EMA), butyl methacrylate (BMA) and hexyl methacrylate (HMA) and the grafting conditions were optimized. Influence of grafting conditions on % monomer conversion, % grafting efficiency and % homopolymers were studied. Grafted samples were analyzed for their thermal behavior using thermogravimetric analysis (TGA) and differential scanning calorimeter (DSC) and grafting was confirmed using nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR). Grafted samples were compression molded into films and the influence of % homopolymers on tensile properties was investigated. It was found that increasing length of alkyl chains decreased grafting efficiency but improved the thermal behavior and provided films with better properties. At high humidity (90%), HMA grafted soyprotein films containing 25% homopolymers retained about 73% of their dry strength, had elongation of 16.5%, better than thermoplastic films previously developed from soyprotein isolates.

Effect of glycosylation on the mechanical properties of edible soy protein packaging film

In this paper, we explore the glycosylation conditions (glucomannan content, reaction time, temperature and humidity) to probe the relationship between glycosylation and mechanical properties of soy protein isolate (SPI) film. The mechanical properties were characterized by studying the tensile strength (TS) and elongation at break (EB). Furthermore, degree of glycosylation, free glucomannan content, surface hydrophobicity, sulfhydryl groups content, lysine and arginine content of glycosylation soy protein with different reaction time were investigated to certify the significant effect of glycosylation on mechanical properties of soy protein film. What is more, the comparison of TS and EB, contact angle values and water vapor permeability of glycosylation SPI (GSPI), SPI and mixture of SPI and glucomannan films showed the excellence of GSPI. At the end, the analysis of scanning electron microscope was applied to reveal the effect of glycosylation on the structure of films. These results suggested that glycosylation with glucomannan is an ideal method to enhance the mechanical properties of soy protein isolate film.

Behavior of protein interfacial films upon bile salts addition

It was studied the effect of the bile salts on protein interfacial films at oil–water interfaces under simulated duodenal conditions (37 °C, pH 7.0 and 39 mM K2HPO4, 150 mM NaCl and 30 mM CaCl2) in order to develop an interfacial film which could resist the interfacial displacement by the bile salts in the duodenum to control the lipids digestion process, as it could retard the next action of lipase and colipase. The proteins studied were β-lactoglobulin, soy proteins and egg white proteins as well as non-ionic low molecular weight surfactants (Tween 20). The interfacial characterization was done by using a pendant drop tensiometer by analyzing the competitive and sequential adsorption of these components at the oil–water interface. The results demonstrated that soy protein film was particularly more resistant to bile salts displacement.

Bio-based films prepared with by-products and wastes: environmental assessment

Abstract Considerable interest in bio-based films has been renewed due to their potential use in packaging industries. Polymers from biomass receive increasing interest as potential substitutes for certain conventional polymers since they are derived from renewable sources and can be biodegradable. However, the life cycle assessment of biofilms has not been widely reported in the literature. In this context, this paper discusses the environmental assessment of bio-based films based on agro-industrial by-products and marine residues, providing added value to these wastes. The materials employed to prepare the bio-based films were soy protein obtained as by-product of soy oil industry, chitosan obtained from the skeleton of crustaceans, and agar obtained from marine seaweeds. The results showed that manufacture is the most contaminant stage for chitosan and agar films, whereas the extraction of raw materials is the stage with the highest environmental burden for soy protein films. In addition, soybeans cultivation contributes to the environmental burden in land use category due to the use of glycerol, considered as by-product from biodiesel production, as plasticizer. However, the end of life stage is the least pollutant phase for bio-based films due to the fact that their biodegradable nature allows composting as the end of life scenario, providing environmental benefits. The present study allows identifying the most pollutant phases of the life cycle for biofilms from different resources, which is the first step prior to the analysis of the changes needed during the design of products and processes to minimize negative impacts in the environment.

Soy protein – Poly (lactic acid) bilayer films as biodegradable material for active food packaging

The preparation and characterization of biodegradable bilayer films from isolated soy protein (SPI) and poly (lactic acid) (PLA) were carried out in this work. The films showed high transparency and strong adhesion between layers without adding an extra component, or without chemically modifying the film surfaces. The application of the PLA layer largely increased the mechanical properties of the films with respect to those of pure SPI films. Furthermore, the hydrophobic characteristics of the PLA layer improved film performance under conditions in which water was involved, markedly decreasing the amount of total soluble matter, the swelling index and the water vapor permeability. The biodegradation under soil burial conditions was evaluated measuring weight loss as a function of time, showing a two-step degradation and a faster degradation rate for the protein component compared to those of PLA layer. The films prepared were evaluated as active packaging by incorporation of an antifungal and an antibacterial agent (natamycin and thymol, respectively) to the SPI layer, showing a marked growth inhibition of mold, yeast and two strains of bacteria by in-vitro microbiological assays.