Corn Zein Research Articles

Barrier properties of corn zein nanocomposite coated polypropylene films for food packaging applications

The feasibility of corn zein nanocomposite (CZNC) coatings as an alternative to synthetic polymer barrier layer on polypropylene (PP) films was examined. The effect of layered silicate content in the CZNC layers on the barrier and surface hydrophobicity of the CZNC-PP films were investigated. Incorporation of organomodified montmorillonite (OMMT) by solution intercalation into zein matrix significantly improved oxygen and water vapor barrier of coated PP films. The barrier properties were also investigated theoretically by using various phenomenological permeability models. Tortuous permeation path formed by the fine delamination of nanoclays was found to be responsible for the barrier improvements in zein layers. In conclusion, durable CZNC-PP laminates were developed. CZNC coating of PP films has reduced the oxygen permeability nearly four times, while water vapor permeability reduced by 30% with 5wt.% OMMT content in 5.9μm corn zein coating.

Alimentary ‘green’ proteins as electrospun scaffolds for skin regenerative engineering

As a potential alternative to currently available skin substitutes and wound dressings, we explored the use of bioactive scaffolds made of plant-derived proteins. We hypothesized that 'green' materials, derived from renewable and biodegradable natural sources, may confer bioactive properties to enhance wound healing and tissue regeneration. We optimized and characterized fibrous scaffolds electrospun from soy protein isolate (SPI) with addition of 0.05% poly(ethylene oxide) (PEO) dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol, and from corn zein dissolved in glacial acetic acid. Fibrous mats electrospun from either of these plant proteins remained intact without further cross-linking, possessing a skin-like pliability. Soy-derived scaffolds supported the adhesion and proliferation of cultured primary human dermal fibroblasts. Using targeted PCR arrays and qPCR validation, we found similar gene expression profiles of fibroblasts cultured for 2 and 24 h on SPI substrates and on collagen type I at both time points. On both substrates there was a pronounced time-dependent upregulation of several genes related to ECM deposition remodelling, including MMP-10, MMP-1, collagen VII, integrin-α2 and laminin-β3, indicating that both plant- and animal-derived materials induce similar responses from the cells after initial adhesion, degrading substrate proteins and depositing extracellular matrix in a 'normal' remodelling process. These results suggest that 'green' proteins, such as soy and zein, are promising as a platform for organotypic skin equivalent culture, as well as implantable scaffolds for skin regeneration. Future studies will determine specific mechanisms of their interaction with skin cells and their efficacy in wound-healing applications.

Spray-Dried Zein Capsules with Coencapsulated Nisin and Thymol as Antimicrobial Delivery System for Enhanced Antilisterial Properties

Food grade antimicrobial delivery systems were studied in this work to enhance the effectiveness of antimicrobials inhibiting the growth of Listeria monocytogenes during storage. Corn zein was used as a carrier biopolymer and nisin and thymol as antimicrobials. Capsules produced by spray drying demonstrated different microstructures and release characteristics of nisin at different usage levels of thymol. Better release profiles were achieved when glycerol was additionally used to prepare capsules. Capsules showing sustained release of significant amounts of both antimicrobials effectively inhibited the growth of L. monocytogenes at pH 6.0 and 30 °C in the growth medium. Capsules were also more effective than free antimicrobials in inhibiting the growth of L. monocytogenes in 2% reduced fat milk at 25 °C. Our work showed that engineered delivery systems have promise to fulfill the antimicrobial effectiveness during shelf life storage of foods to ensure microbiological safety.

Bioavailability of Soy Protein and Corn Zein Films

The in vivo bioavailability of soy protein isolates and corn zein film material before and after film formation by heat/ pressure was determined. The In vitro digestibility of corn zein before and after film formation was also measured. Films were produced from anhydrous protein with 30% glycerol added using a heat-press method with no use of casting solvents or cross-linking agents. Corn zein raw and film material were ground under liquid nitrogen then digested in two enzyme-acid cocktails with free amino acid analysis before and after digestion. The protein efficiency ratio and net protein ratio were determined for both zein and soy protein using a weanling Sprague-Dawley descended rat feeding study. The In vitro digestibility study indicated that the non-heat pressed corn zein was more digestible than the heat pressed zein. However, the in vivo results indicated that corn and soy protein were equally bioavailable whether they were derived from film mixture prior to or after film formation. Both corn zein and soy protein material had lower protein efficiency ratio than the control diet. Furthermore, soy protein films materials had a higher protein efficiency ratio than corn zein.

Pectin–zein microspheres as drug delivery systems

The formation of microspheres from various pectin hydrogel complexes and corn zein in the presence of calcium and zinc ions has been studied. It is shown that the formation of microspheres and their loading capacity for a drug (piroxicam) depend on the type of biopolymers, their ratio, the sizes of the bivalent ions, and the molecular mass of the pectin. Complex formation between the two biopolymers results predominantly from bivalent metal cross-linking for low-methylated pectins and from hydrophobic interaction for high-methylated pectins. As a result, a series of microspheres have been prepared from biodegradable and biocompatible polymers and may find application as controlled-release drug delivery systems.

Evaluation of the biocide properties of whey-protein edible films with potassium sorbate to control non-O157 shiga toxinproducing Escherichia coli

The use of edible films to release antimicrobial constituents in food packaging is a form of active packaging that contributes to extend the shelf-life of a product and provides microbial safety for consumers. A number of plant and animal proteins have been investigated for the production of edible films such as corn zein, wheat gluten, soy and peanut proteins, gelatin, collagen, casein, and whey proteins. Several antimicrobial agents such as organic acids, enzymes, fungicides and natural antimicrobial compounds (spices and essential oils) can be incorporated into edible films. Potassium sorbate (PS) have a long history as a generally recognized as safe food preservative, being widely used to inhibit or retard the growing of a number of recognized food pathogens. Shiga toxin-producing Escherichia coli (STEC) O157 and non-O157 strains have been associated with human disease, ranging from uncomplicated diarrhea to hemorrhagic colitis and hemolytic uremic syndrome. STEC is transmitted to humans through contaminated food, water, and direct contact with infected persons or animals. Several outbreaks caused by non-O157 STEC were described although data implicating these STEC were scanty and the source of infection was not always known. Therefore, the objective of the present study was to incorporate PS into whey protein concentrate (WPC) films and to determine the inhibitory effects of these films against eight non-O157 STEC strains isolated from readyto-eat food samples.

Effects of edible film coatings on shelf-life of mustafakemalpasa sweet, a cheese based dessert

It was aimed to investigate the shelf-life of single baked (one stage heating at 280-300°C) mustafakemalpasa (MKP) cheese sweets coated with edible films such as κ-carrageenan, chitosan, corn zein and whey protein concentrate (WPC). The sweets prepared were coated, packed in polystyrene bags and stored at room temperature (20 ± 1°C). The shelf-life of sweet samples was determined by microbiological analyses, aw, titratable acidity, pH and sensory analysis. The microorganisms exhibited growth dependent upon the water activity levels during storage. The most significant growth was seen in moulds and yeasts. The minimum aw values for the growth of mould and yeasts were 0.85. Coating with chitosan and κ-carrageenan showed no significant effect on shelf-life of MKP sweets. The shelf-life of these samples was limited by 3days same as control (non-coated) and deterioration occurred when the aw value reached 0.90. The coatings with WPC and corn zein prolonged the shelf-life of sweets from 3 to 10days.

Effect of corn‐zein coating on the mechanical properties of polypropylene packaging films

AbstractIn this study, a novel film structure of corn zein coated on polypropylene (PP) synthetic films for food packaging applications was developed, and the mechanical properties of the resulting coated film, as affected by the coating formulation, were investigated. Composite structures of PP films coated with corn zein were obtained through a simple solvent casting method. Different amounts of corn zein (5 and 15%) were dissolved in 70 and 95% aqueous ethanol solution at 50°C. Solutions of corn zein plasticized with poly(ethylene glycol) and glycerol (GLY) at various levels (20 and 50%) were applied on corona‐discharge‐treated PP. A statistical analysis based on full factorial design was performed to examine the influence of the coating formulation on the final properties of the corn‐zein‐coated PP films. A significant (p < 0.05) improvement in the coated film's mechanical properties was observed compared to those of the uncoated PP. The effect of the plasticization of the coating solutions was also quite significant. In general, GLY provided better improvements in the mechanical properties of the corn‐zein‐coated PP films. The statistical analysis of the results showed that the corn‐zein and plasticizer concentrations and plasticizer type used in the coating formulations were more effective parameters and had significant effects on the mechanical behavior of the coated PP films. In conclusion, corn‐zein coatings could have potential as alternatives to conventional synthetic polymers used in composite multilayer structures for food packaging applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011

Biodegradable protein‐based films from plant resources: A review

AbstractThis review provides an overview of studies on the film‐forming properties of soy protein, wheat gluten and corn zein. Biodegradable films from these proteins have been investigated extensively. Casting is the most often used film‐forming method. Glycerol is added as plasticizer in many studies. The proteins are normally dissolved or dispersed in suitable solvents with plasticizers. The resulting solutions or dispersions form free standing films on a plate by casting the mixture and subsequent drying. Posttreatments such as coating, heating, and radiation are also employed to improve film properties. These protein films in general are water sensitive and lack mechanical strength but are good oxygen barriers. Further studies to improve the properties of the films for food packaging materials are also discussed. © 2010 American Institute of Chemical Engineers Environ Prog, 2010

Determination of thiobarbituric acid reactive substances in microencapsulated products

Food samples are usually extracted or distillated before quantification of thiobarbituric acid reactive substances (TBARS) for evaluation of secondary lipid oxidation, which is a challenge for microencapsulation projects with limited sample quantities. Our approach was to use a ternary solvent mixture of 1-butanol, isopropanol, and 0.5 M HCl (in water) at a proportion of 2:2:1 (v/v/v) to completely dissolve microcapsules of fish oil. The solvent system allowed the construction of highly linear standard curves with good sensitivity: 0.4–13 μM 1,1,3,3,-tetramethoxypropane as a TBA reactive standard with a R 2 value of 99.86%. For a sample of fish oil coated by corn zein, only 40 mg of the sample was needed to obtain reliable and repeatable TBARS values. Further, several common encapsulation materials gave low interferences to the assay. The proposed approach, with the above qualities along with good precision and accuracy, may be applicable to a variety of relevant bioactive compounds and encapsulation materials.

COMPARATIVE STUDY OF EGG WHITE PROTEIN AND EGG ALTERNATIVES USED IN AN ANGEL FOOD CAKE SYSTEM

Comparisons of the physical and sensory properties of several commercial egg alternatives in angel food cake formulation were studied. Fourteen samples were investigated for foaming properties at 10 and 20 min whipping time: collagen, Cryogel gelatin, Solugel collagen hydroysates, gelatin, whey protein concentrate, fish protein, whey protein isolate (95% WPI, 90%WPI), hydrolyzed whey protein isolate, pea protein, rice protein concentrate, soy protein, corn zein and casein. However, only eight samples showed potential and were moved forward for further evaluation. Only the WPI alternative was able to maintain a meringue during baking. All other foams collapsed during the baking process. The angel food cake formulated with WPI exhibited a significantly firmer crust and crumb compared with the egg white control. The L value, height and volume of control cake were also significantly higher than the egg alternative. The control significantly outperformed the angel food cake formulated with the egg alternative in all sensory categories evaluated.

The Corn Protein, Zein Hydrolysate, Administered into the Ileum Attenuates Hyperglycemia via Its Dual Action on Glucagon-Like Peptide-1 Secretion and Dipeptidyl Peptidase-IV Activity in Rats

We previously showed that a hydrolysate prepared from corn zein [zein hydrolysate (ZeinH)] strongly stimulates glucagons-like peptide-1 (GLP-1) secretion from the murine GLP-1-producing enteroendocrine cell line and in the rat small intestine, especially in the ileum. Here, we investigated whether ZeinH administered into the ileum affects glucose tolerance via stimulating GLP-1 secretion. To observe the effect of luminal ZeinH itself on GLP-1 secretion and glycemia, ip glucose tolerance tests were performed in conscious rats with ileal and jugular catheters, and plasma glucose, insulin, and GLP-1 (total and active) were measured. In addition, plasma dipeptidyl peptidase-IV activities in the ileal vein were measured after the administration of ZeinH into the ileal-ligated loop in anesthetized rats. The ileal administration of ZeinH attenuated the glucose-induced hyperglycemia accompanied by the enhancement of insulin secretion, whereas meat hydrolysate (MHY) neither induced insulin secretion nor attenuated hyperglycemia. The antihyperglycemic effect was also demonstrated by the oral administration of ZeinH. From these results, it was predicted that the GLP-1-releasing potency of ZeinH was higher than that of MHY. However, both peptides induced a similar increase in total GLP-1 concentration after the ileal administration. In contrast, active GLP-1 concentration was increased only in ZeinH-treated rats. In anesthetized rats, ileal administration of ZeinH, but not MHY, decreased plasma dipeptidyl peptidase-IV activity in the ileal vein. These results indicate that the ileal administration of a dietary peptide, ZeinH, has the dual functions of inducing GLP-1 secretion and inhibiting GLP-1 degradation, resulting in the enhancement of insulin secretion and the prevention of hyperglycemia in rats.

Edible oxygen barrier bilayer film pouches from corn zein and soy protein isolate for olive oil packaging

An edible oxygen barrier film pouch was fabricated from a heat sealable corn zein (CZ) layer laminated on soy protein isolate (SPI) film and used to package olive oil condiments for use with instant noodles. The mechanical, barrier, and physical properties of the CZ/SPI bilayer films were then investigated and the oxidative stability of olive oil in the pouches was measured during storage under dry and intermediate relative humidity conditions. When compared to the SPI film, lamination with an additional layer of CZ film led to increased tensile strength and water barrier properties, while it had a lower elongation at break and decreased oxygen barrier properties. Nevertheless, the oxygen permeability of the CZ/SPI film (0.81 × 10 −18 m 3 m/m 2 s Pa) was lower than that of nylon-metalocene catalyzed linear low-density polyethylene (NY/mLLDPE) film (3.51 × 10 −18 m 3 m/m 2 s Pa) which is the material usually used for such condiments. The CZ/SPI bilayer films generated here were heat sealable at 120–130 °C and produced a seal strength greater than 300 N/m. The higher oxygen barrier property of the CZ/SPI bilayer films resulted in reduced oxidative rancidity of olive oil packaged in the CZ/SPI film when compared to olive oil packaged in NY/mLLDPE films.

Propionic acid in bio-based packaging to prevent Sitophilus granarius (L.) (Coleoptera, Dryophthoridae) infestation in cereal products

The aim of the work is to develop a biodegradable carrier material to control insect pests in cereal products. To this purpose, a known repellent of stored-product insects, propionic acid, was incorporated in biodegradable coatings then applied onto carton intended for packaging cereal goods. Different coating layers of corn zein and policaprolactone (PCL) respectively, were tested as carrier of the natural compound. The bioassay was carried out over a two-week period with a high number of insects confined in a small space and damaged cartons imitating breakdown or poor sealed packaging, in order to simulate awfully infestation conditions. The results demonstrated that at the end of the aging period, the percentage of S. granarius adults found in cartons coated with propionic acid-loaded mono and multilayer PCL and zein was only 13.1%, 11.3%, 18.0% and 10.7% of the total number of insects used in the bioassay, respectively. On the contrary, coating materials and/or solvents used for coating preparation had no effects on insect entering ability, since the percentages of insects found in coated cartons without propionic acid and in the uncoated cartons were almost similar. The granary weevil is a serious pest of stored cereal products worldwide. Thus, the exploration of biodegradable systems to control insect pests represents a strategic solution for the industrial sector due to the ability of these systems to break down after completion of function. The selection of a proper repellent compound is also of crucial importance. Propionic acid was found effective for the aim of the work and it could be greatly priced since it is a natural compound already used as a food preservative.

ANTIOXIDANT PROPERTIES AND POSSIBLE MODE OF ACTION OF CORN PROTEIN PEPTIDES AND ZEIN PEPTIDES

ABSTRACT Corn peptides (CPS) and zein peptides (ZPS) were prepared from defatted corn gluten meal and zein, respectively by proteolysis with alcalase, an alkaline protease. The molecular-mass distributions and amino acid compositions of CPS and ZPS were determined and compared. With α-tocopherol as the positive control, the antioxidant activities of CPS and ZPS were investigated by several in vitro assay systems, including the scavenging effects on 2, 2-diphenyl-1-picrylhydrazyl radical, the inhibiting emergence of hydroxyl radical and prevention of linoleic acidauto-oxidation and the reducing power of CPS and ZPS. The capacities of CPS and ZPS removing superoxide anion from pyrogallol auto-oxidation were also estimated. The data revealed that the antioxidant potency of CPS was similar to that of ZPS. CPS and ZPS also exhibited the similar reducing power. The possible mode of action of antioxidant activity was because of the presence of some proton-donating peptide components in CPS and ZPS products. PRACTICAL APPLICATIONS CPS, hydrolyzate of corn gluten meal through the action of alcalase with the molecular-mass distribution from 300 to 1,000 Da, showed the same notable antioxidant activities, free radical-scavenging activities and reducing power in vitro as those of ZPS, hydrolyzate of zein. Therefore, CPS rather than ZPS can be used as an ingredient with antioxidant activity in pharmaceutical and food industries in the future. Subsequently, the cost of production of natural antioxidant can be decreased and the process of production also be simplified greatly.

Water vapor and oxygen-barrier performance of corn–zein coated polypropylene films

A novel corn–zein coating structure on polypropylene (PP) films was developed to examine its feasibility as an alternative water vapor and oxygen-barrier for flexible packaging industry. The barrier properties of the resulting films were evaluated as affected by coating formulation (solvent, corn–zein, plasticizer concentration and plasticizer type). Corn–zein with different amounts (5% and 15%) was dissolved in 70% and 95% aqueous ethanol solution at 50 °C, respectively. Solutions of corn–zein plasticized by polyethylene glycol (PEG) and glycerol (GLY) with various levels (20% and 50%) were applied on corona-discharged-treated PP by using solvent-casting method. The significant improvements in water vapor and oxygen-barrier properties of uncoated PP films were obtained with corn–zein coating. Water vapor permeability (WVP) of the coated films decreased significantly with increasing corn–zein concentration. The application of plasticized corn–zein coating on PP films showed nearly more than three order of reduction in oxygen permeability (OP). The high water vapor and oxygen-barriers were obtained for films coated with coating formulation consisting of higher amounts of corn–zein plasticized by GLY. The statistical analysis defined the key parameters of coating formulation that had major effect on the final properties of coated PP films as corn–zein, plasticizer concentration, and plasticizer type.

Dental Mold: A Novel Formulation to Treat Common Dental Disorders

Oral administration of antibiotics to treat dental problems mostly yields slow actions due to slow onset and hepatic "first-pass." Again, commonly used dental paints are generally washed out by saliva within few hours of application. To overcome the challenges, polymeric molds to be placed on an affected tooth (during carries and gum problems) were prepared and evaluated in vitro for sustained drug release for prolonged local action. Here, amoxicillin trihydrate and lidocaine hydrochloride were used as model drugs. Dental molds were prepared using corn zein, carbopol 934 P, gum karaya powder, and poloxamer 407 by mixing and solvent evaporation technique. Different physicochemical evaluation studies such as tooth adhesion test, surface pH, swelling index, and drug-distribution pattern were carried out. Percentage swelling varied from 56% to 93%. Average tooth adhesion strength and mean initial surface pH of the formulations were 50 g and 6.5, respectively. As assessed by scanning electron microscopy, drug distribution was uniform throughout the matrix. Cumulative percentage release of lidocaine hydrochloride and amoxicillin trihydrate in simulated saliva were 98% and 50%, respectively. In vitro drug-release studies revealed the sustained-release patterns of the drugs in simulated saliva at least for 24 h. The stability study shows that the drugs were stable in the formulations following the conditions as per ICH guideline. The formulation is a novel approach to deliver the drug(s) for a prolonged period for local action upon its application on an affected tooth.

Electrospun Zein Fibers as Carriers to Stabilize (−)‐Epigallocatechin Gallate

In this study, a method was developed for continuous electrospinning of ultrafine corn zein protein fibers with diameters ranging from 150 to 600 nm. Fiber-forming solutions with various zein concentrations (10% to 30%, w/w) and aqueous ethanol concentrations (60% to 90%, w/w) were electrospun at 15 and 20 kV. Scanning electron microscopy results showed that the morphology of zein fibers was affected by aqueous ethanol concentration, zein concentration, and the applied voltage. The optimal condition for forming bead-less fibers was found to be 20% protein, 70% alcohol, and 15 kV. The zein fibers resisted solubilization in water, although swelling and plasticization were apparent after the water treatment. The efficacy of zein fibers was tested for stabilization of a green tea polyphenol, (-)-epigallocatechin gallate (EGCG), by incorporating the EGCG in zein fiber-forming solutions. Freshly spun fibers were less effective at immobilizing the EGCG upon immersion in water (82% recovery) as compared to fibers that were aged at 0% relative humidity for at least 1 d (>98% recovery) before water immersion. Fourier transform infrared spectroscopy studies demonstrated that hydrogen bonding, hydrophobic interactions, and physical encapsulation are the major contributors to the stabilization of EGCG in zein fibers in water.

Nanoscalar Structures of Spray-Dried Zein Microcapsules and in Vitro Release Kinetics of the Encapsulated Lysozyme As Affected by Formulations

Sustained release of antimicrobials may be a viable solution to enhance the bioavailability during the shelf life of food products. In this work, spray-drying was used to encapsulate a model antimicrobial of lysozyme in corn zein. The effects of zein/lysozyme (20:1 to 4:1) and zein/thymol (1:0 to 4:1) ratios on the microstructures of microcapsules and in vitro release profiles of the encapsulated lysozyme were investigated. In all cases, less lysozyme was released at higher pH, resulting from stronger molecular attraction between zein and lysozyme. Nanoscalar matrix structures of microcapsules were correlated with release characteristics of the encapsulated lysozyme. At intermediate zein/lysozyme (10:1) and zein/thymol (50:1) ratios, microcapsules had a continuous matrix structure and showed sustained release (11.1-65.3%) of lysozyme at pH 6 over 49 days. This work may be developed into practical food grade delivery systems of antimicrobials.

Decolorization/deodorization of zein via activated carbons and molecular sieves

Commercially available corn zeins from co-products of the corn ethanol industry possess yellow color and off-odors that deter their usage in food, medical, pharmaceutical and cosmetic industries. A pilot-scale process (patent pending) was developed to purify those products. Our objective is to investigate a series of activated carbons and zeolites, clay-based particles acting as molecular sieves, as potential column media for that process. A batch process was used to evaluate each of five different activated carbons and zeolites to determine the adsorption characteristics of protein and the color and off-odor components. Adsorptive properties of those media were performed by spectral analyses at wavelengths 280 nm for the protein component and 325 nm for the contaminants. Statistical evaluation of the batch adsorption data from each series demonstrated that activated carbon generated from coconut hulls and zeolite 5 A (5 angstrom pore size) adsorbed the least amount of protein relative to contaminant adsorptions. Our selection of column media for the pilot-scale process was based on these findings.