Corn Zein Research Articles

The use of edible protein films in seafood

It is used different conservation and packaging techniques in food industry by delaying enzymatic and microbial spoilage. One of the important development in this issue is edible films and coatings. These materials are made from natural biopolymers and constituted with thin layer on the surface of food. Lipid oxidation is prevented, in addition to water, aromatic components, pigments, ions and vitamins are hold in food by edible films. The most important property of edible films is not carrying cancerogenic risk and don’t cause waste problem, which are serious problems in plastic packaging materials. Edible films can fulfill all the functions of a functional package, if they are properly prepared. It is used generally hydrocolloids (protein and polysaccharides), lipids and composites (hydrocolloids+lipid) in the preparation of edible films. Edible protein films are however classified into two groups as plant origin proteins (such as corn zein, wheat gluten, soy protein, pea protein, sunflower protein, peanut protein and cottonseed protein) and animal origin proteins (such as keratin, collagen, gelatin, fish myofibrillar protein, egg white protein, casein and whey protein). Edible protein films, which are produced from protein isolates or protein consantrates, may be also generated by food processing waste as an evaluation method. The aim of this review is to explain mostly used protein films and to moot that the films are prepared directly from main structure proteins or water soluble proteins (at processing waste) and can applied yet to seafood. So, waste problem is reduced bidirectional and more safety seafoods can producted.

Size exclusion chromatography of zein and xanthophylls: Optimization of operating parameters

Ethanol-soluble components of corn (zein and xanthophylls) were separated and purified by size exclusion chromatography. Aqueous ethanol was used as the solvent for the entire process from extraction through chromatography. The effect of operating and design parameters, such as temperature, flow rate, loading mass, loading volume, column height and diameter, on productivity and resolution of the components was studied. Using a one-variable-at-a-time (OVAT) approach with 1 cm × 60 cm columns, optimum conditions were determined to be 40 °C temperature, 0.25 mL/min flow rate, volume loading of 22 mL corn extract, mass loading at 70 g/L of corn extract. All components could be resolved with base line separation with a 240 cm column length. Column diameter did not affect separation, implying linear scalability with constant flow distribution.

Sustained release of lysozyme from zein microcapsules produced by a supercritical anti-solvent process

Delivery systems with sustained release of antimicrobials are possible solutions to minimize the binding between antimicrobials and food matrices, thereby enhancing the efficacy of antimicrobials during shelf-lives of foods. In this work, GRAS (generally recognized as safe) corn zein was used as a carrier material and 90% aqueous ethanol was used as a solvent to microencapsulate GRAS hen egg white lysozyme using a supercritical anti-solvent (SAS) process. The microcapsules showed a continuous matrix with internal voids. The release of lysozyme was observed over 36 days at room temperature, with slower release at a higher pH between 2 and 8. At pH 4, release kinetics was further slowed by the addition of sodium chloride. Stronger molecular attraction between lysozyme and carrier zein was attributed to slower release at a higher pH and a higher ionic strength at the same pH. Our work demonstrated that SAS may be a feasible process to manufacture GRAS delivery systems to enhance antimicrobial efficacy.

Production of corn zein microparticles with loaded lysozyme directly extracted from hen egg white using spray drying: Extraction studies

Feasibility of achieving sustained release of lysozyme by encapsulation in corn zein using spray drying was examined. To reduce the materials cost, this part of work focused on partially purifying lysozyme from hen egg white using 30–90% (v/v) aqueous ethanol, adjusted to pH 3.0–9.24. After extraction for up to 24 h and centrifugation, the purification performance was evaluated for the supernatant. Extraction was insignificantly affected by kinetics ( P = 0.6186) but was inefficient at pH above 5.0 and above 60% ethanol. The optimal extraction was achieved at 50% ethanol and pH 3.5. Further, most of the lysozyme precipitated from the 50% ethanol (at pH 3.5) extract after increasing ethanol concentration to 90% but was completely recovered after diluting the precipitate back to 50% ethanol. Findings from this work may lead to low-cost encapsulation technologies using partially-purified lysozyme, such as spray drying.

Conformational Changes and Molecular Mobility in Plasticized Proteins

Most biopolymers exist in a plasticized state, whether it is naturally with water or unnaturally with glycerol or other suitable polyol, to make a flexible material. We have found that the extent to which a biopolymer can be plasticized is dependent on its molecular and higher order structures outside of simply molecular weight. Lactalbumin, ovalbumin, corn zein, wheat gluten, and feather keratin were plasticized with glycerol from very low to very high amounts. The conformation of the proteins was monitored with Fourier transform-infrared (FT-IR) spectroscopy and X-ray powder diffraction (XRD) and correlated with the tensile modulus. Protein conformational changes were pronounced for polar proteins with a low amount of cysteine. FT-IR showed that the conformational changes resulted in ordering of the protein at low to moderate plasticization levels. For proteins with little resistance to conformational changes, additional small-scale ordering occurred around the glass transition, as observed in XRD. Accurate comparison of plasticized proteins was dependent on knowing whether or not the protein was glassy or rubbery at room temperature as no differences arose in the glassy state. The transition from glassy to rubbery behavior with plasticization level can be found from modulus, FT-IR, and XRD data.

Chemistry and Physical Properties of Melt-Processed and Solution-Cross-Linked Corn Zein

Corn zein was cross-linked with glutaraldehyde (GDA) using glacial acetic acid (HAc) as catalyst. The objectives are to evaluate the swelling characteristics of GDA cross-linked zein gels in water, ethanol, and their combinations. Similar formulations, upon solvent evaporation, form films. The mechanical properties of the films are compared to compression molded tensile bars from GDA melt-processed zein as a second objective. Chemistry of the cross-linking reaction was based on the aldehyde binding characteristics defined by use of fluorescence spectroscopy; sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to demonstrate the cross-linking reaction; FTIR to observe absorption differences of the cross-linked product; differential scanning calorimetry, dynamic mechanical analysis and thermogravimetric analysis to assess thermal properties; and the use of Instron Universal Testing Machine to evaluate mechanical properties. A reaction mechanism for acid catalyzed GDA cross-linking of zein is proposed. Thermal and mechanical properties of tensile bars cut from either film or formed by compression molding were similar, where both showed increased tensile strengths, ductility and stiffness when compared with unmodified controls. Samples that were reacted with 8% GDA by weight based on weight of zein from either process retained their integrity when tensile bars from each were subjected to boiling water for 10 min or soaking in either water or HAc for 24 h. The melt-processed, cross-linked zein is a more environmentally friendly method that would eliminate the need for HAc recovery.

Improved Isolation of Zein from Corn Gluten Meal Using Acetic Acid and Isolate Characterization as Solvent

ABSTRACTAn improved means of isolating zein is needed to develop new uses for corn zein. We have measured the yield of zein and evaluated the ability of acetic acid to remove zein from corn gluten meal, distillers dried grains, and ground corn using acetic acid as solvent. Acetic acid removed zein more quickly, at lower temperatures, and in higher yields when compared with alcoholic solvents. After 60 min at 25°C, ≈50% of the zein in corn gluten meal was removed. A step change in yield from 43 to 50% occurs as the extraction temperature is increased from 40 to 55°C after mixing for 30 min at 25% solids. The protein composition of the zein removed from corn gluten meal using acetic acid is very similar to that of commercial zein by SDS‐PAGE. The zein obtained from corn gluten meal using acetic acid had higher amounts of fatty acids and esters according to IR analysis, leading to slightly lower protein content. Films made from zein extracted from corn gluten meal using acetic acid had lower tensile strength (≈60% lower) than films produced from commercial zein. Fibers with very small diameter (0.4–1.6 μm) can be produced by electrospinning using the AcOH solution obtained after corn gluten meal extraction.

Effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing yellow zein

The Freundlich model was evaluated for use to assess the effect of heat on the adsorption capacity of an activated carbon for decolorizing/deodorizing corn zein. Because zein protein and its color/odor components are all adsorbed by activated carbon, a method to monitor their removal was needed. Yellow color is due to xanthophylls; a contributor to off-odor is diferuloylputrescine. The off-odor component absorbs ultraviolet (UV) light at about 325 nm and its removal coincides with removal of yellow color. A spectrophotometric method based on UV absorbances 280 nm for protein and 325 nm for the off-odor component was used to monitor their adsorptions onto activated carbon. Equilibrium studies were performed over temperature range from 25 to 60 °C for zein dissolved in 70% aqueous ethanol. Runs made at 55 °C adsorbed significantly more of the color/odor components than the protein.

Thermoplastic Processing of Proteins for Film Formation—A Review

Increasing interest in high-quality food products with increased shelf life and reduced environmental impact has encouraged the study and development of edible and/or biodegradable polymer films and coatings. Edible films provide the opportunity to effectively control mass transfer among different components in a food or between the food and its surrounding environment. The diversity of proteins that results from an almost limitless number of side-chain amino-acid sequential arrangements allows for a wide range of interactions and chemical reactions to take place as proteins denature and cross-link during heat processing. Proteins such as wheat gluten, corn zein, soy protein, myofibrillar proteins, and whey proteins have been successfully formed into films using thermoplastic processes such as compression molding and extrusion. Thermoplastic processing can result in a highly efficient manufacturing method with commercial potential for large-scale production of edible films due to the low moisture levels, high temperatures, and short times used. Addition of water, glycerol, sorbitol, sucrose, and other plasticizers allows the proteins to undergo the glass transition and facilitates deformation and processability without thermal degradation. Target film variables, important in predicting biopackage performance under various conditions, include mechanical, thermal, barrier, and microstructural properties. Comparisons of film properties should be made with care since results depend on parameters such as film-forming materials, film formulation, fabrication method, operating conditions, testing equipment, and testing conditions. Film applications include their use as wraps, pouches, bags, casings, and sachets to protect foods, reduce waste, and improve package recyclability.

Characterization of protein-coated polypropylene films as a novel composite structure for active food packaging application

Plasticized protein coatings on polypropylene (PP) film were prepared and examined for their optical and tensile properties as affected by protein and plasticizer types in order to exploit a novel composite film for food packaging applications. Composite structure of PP film coated with three kinds of proteins (soy protein isolate: SPI, whey protein isolate: WPI, corn zein: CZ) and various plasticizers (propylene glycol, glycerol, polyethylene glycol, sorbitol, sucrose) could be obtained by a simple casting method. High glossy surfaces were observed on the coated films with WPI and CZ, with the sucrose-plasticized WPI coating giving the highest gloss. Proteins as well as plasticizers exerted a noticeable effect on color of the coated films. WPI coated films also showed greater transparency and tensile strength than the other coated films. Nisin-incorporated WPI coatings on PP film exhibited significant bacterial growth inhibition against Lactobacillus plantarum. Results suggest that WPI coatings with a proper plasticizer possess excellent visual and mechanical characteristics and have great potential for application in active packaging systems.

Properties of films from corn zein reacted with glutaraldehyde

AbstractTo improve the mechanical properties of zein films, a commercial white zein was reacted in glacial acetic acid (HAc) with glutaraldehyde (GDA) from 0.5 to 16% by weight based on the weight of zein. Amounts of 4% or higher GDA‐modified zein, when cured in a closed system, generated a gel. That gel was insoluble in organic solvents known to solubilize zein. Zein solutions cast within a silicon rubber gasket sealed onto Teflon‐coated plates, when air dried, generated 0.7–0.9‐mm thick films. Those films from 8% GDA‐modified zein had a water vapor permeability of 5.9 × 10−8 g cm/Pa s m2. Overall, results indicate that our thicker films gave higher water vapor permeability than values reported in the literature. To achieve consistent and comparable results with differential scanning calorimetry (DSC) and dynamic mechanical analyses (DMA), film samples had to be heated to remove residual HAc. An increase in the glass transition temperatures for those films from GDA‐modification of zein, observed with both DSC and DMA, was attributed to the crosslinking of zein. Physical testing of tensile bars cut from GDA‐modified zein films showed minor enhancement of tensile strength, percent elongation, and Young's modulus in the 0.5% GDA‐modified zein films, which increased and leveled off with 4% or higher amounts of GDA for the modifications. When the 4 to 16% GDA results are averaged, the tensile strength for the modified zein films increased 1.8‐fold when compared with unmodified zein control films. On the same note, percent elongation showed a 1.8‐fold increase and Young's modulus showed a 1.5‐fold increase. GDA reaction with zein generated films with improved tensile strength, ductility, and stiffness when compared with respective zein control films that retained their integrity when subjected to either boiling water or extensive soaking. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007

Incorporation of the Antilisterial Bacteriocin-like Inhibitory Substance from Pediococcus parvulus VKMX133 into Film-forming Protein Matrices with Different Hydrophobicity

The antilisterial bacteriocin-like inhibitory substance (BLIS) produced by Pediococcus parvulus VKMX133 was incorporated into protein film matrices of ethanol-soluble corn zein (CZ), and water-soluble whey protein isolate (WPI). Various BLIS concentrations were added to film-forming solutions (FFS), cast, dried, and cut in circular sections (28.27 mm2). Antimicrobial activity of films was evaluated by measuring inhibition zones against Listeria innocua ATCC 33090 on tryptic soy broth (TSB) agar. BLIS released from films into water at 10 °C was determined. Film effectiveness was evaluated by measuring the reduction of L. innocua population (108 colony-forming units [CFU]/mL) in peptone water where film sections were immersed. Film topography was analyzed by scanning electron microscopy (SEM). The minimum BLIS concentration in FFS to generate films with antimicrobial activity was 833 and 3333 arbitrary units per milliliter (AU/mL) for CZ and WPI, respectively. BLIS released into water was detected only for CZ films. Antimicrobial CZ films were more effective in reducing L. innocua population than WPI films at the same BLIS concentrations. SEM showed that surface topography was porous for CZ and more closed and compact for WPI films. BLIS can be entrapped into film protein matrices to produce edible antimicrobial packaging. However, BLIS inhibitory action against L. innocua and release were dependent on film nature and topography, and probably on hydrophobic and electrostatic interactions arising between the protein matrices and BLIS. High concentration of bacteriocin in films does not necessarily improve their effectiveness against L. innocua.

Formulation of Corn Zein Chewing Gum and Evaluation of Sensory Properties by the Time‐Intensity Method

ABSTRACT:This study was conducted to determine the feasibility of using corn zein as a natural gum base to be an alternative to the currently used synthetic gum base. The objectives were to (1) develop a corn zein chewing gum and (2) evaluate the taste, texture, and aroma qualities compared with synthetic gum base using a time‐intensity (T‐I) method. Four corn zein gum samples, each made with a different plasticizer (oleic acid, glycerin, propylene glycol, and 1 without any plasticizer), were included in the study along with 2 synthetic gum‐base samples. Nine panelists participated in the T‐I study. Thirteen attributes were evaluated. Maximum intensity, time to maximum intensity, and duration were parameters extracted from the T‐I curve. The synthetic gum‐base samples were rated higher for the maximum intensity of sweet taste and cinnamon aroma‐by‐mouth and lower for the maximum intensity of bitter taste. The propylene glycol corn zein sample was rated the highest for cinnamon aroma and the lowest for stale, rancid, and cheesy aromas. Out of the corn zein gums, the oleic acid sample was rated the lowest for the maximum intensity of hardness. It was also rated highest for the maximum intensity of bitter taste and the lowest for sweet taste. This study showed that it is feasible to use corn zein as a gum base, but future work is needed to develop an acceptable product for consumers.

Comparison of methods to analyze time–intensity curves in a corn zein chewing gum study

Nine panelists participated in a time–intensity ( T– I) study to evaluate the taste, texture and aroma qualities of corn zein gum compared to synthetic gum samples. Four corn zein gum samples varying in type of plasticizer, and two synthetic gum samples were evaluated. Two different methods were used to analyze T– I curves, grouping panelists with similar individual curves and the enhanced method developed by Liu and MacFie in the 1990s. Grouping panelists with similar individual curves was a more effective method to use when not all panelists reached zero intensity. Only panelists returning to zero intensity could be included in the final mean curve using the enhanced method. Both the propylene glycol and oleic acid corn zein samples showed potential for future development as an alternative to the synthetic gum base currently used.

Improved methods for decolorizing corn zein

The yellow color of corn and corn processing co-products is due to xanthophylls and β-carotene. Colorless zein commands a premium price and the resulting extracted carotenoids possess nutraceutical value. Our objectives were to devise methods for decolorizing zein and develop methodology to quantify color removal. Decolorizing methods include: subcritical propane and supercritical fluid extraction with carbon dioxide of zein with ethanol entrainers; ultrafiltration/diafiltration on a tangential flow system; partitioning with toluene; column chromatography on Sephadex LH-60; batch treatment with activated carbon. Residual color was assessed by dissolving zein control or decolorized product in glacial acetic acid, filtration, and reading absorbances of dilutions at 448 nm. Analysis of covariance from comparative logarithmic regressions of control zein and decolorized product dilutions was evaluated to determine the extent of residual color. Because, a covariate by treatment interaction was detected in treatments for supercritical fluid extractions an Analysis of Variance model comparing treatment method means at each dilution factor level was used. Results showed that subcritical propane extraction of zein with ethanol entrainer gave the least color removal. A commercial white zein possessed a similar degree of residual color as did ethanolic zein solutions partitioned with toluene. Almost complete removal was achieved by extractions of zein from corn gluten meal followed by batch treatment of those extracts with activated carbon. However, recovered yield was lowest with this procedure. Supercritical fluid extraction with carbon dioxide of zein with 15% ethanol entrainer for 15 min at 68,950 kPa and 70 °C decolorized zein slightly less than did either the column chromatographic method with Sephadex LH-60 or a diafiltration of zein ethanolic solutions ultrafiltered through the 5000 Da molecular weight cut-off membrane. These three methods gave excellent recoveries of decolorized zein product. The supercritical fluid method has the advantages of no need to spray-dry the final product and does not require the copious volumes of ethanol needed for color removal by the other methods. This method would utilize the carbon dioxide and ethanol byproducts generated by the fermentation process used for producing ethanol.

Nisin release from films is affected by both protein type and film-forming method

Effects of protein type (wheat or corn) and film-forming method (casting or heat-pressing) on films were evaluated for the retention of biologically active nisin (Nisaplin) and release of activity into water at four different temperatures (5, 25, 35 and 45 °C). Nisin activity was measured using the agar diffusion method against Lactobacillus plantarum 1752. Cast corn zein (CCZ) and cast wheat gluten (CWG) films retained 12.1% (8.1×10 4 IU/g film) and 15.8% (1.1×10 5 IU/g film) of the original activity after film formation, respectively. Heat-pressed corn zein (HPCZ) and heat-pressed wheat gluten (HPWG) films retained 6.5% (4.3×10 4 IU/g film) and 7.4% (4. 9×10 4 IU/g film) of the original activity after film formation, respectively. The maximum nisin activity found migrating into water at any sampling time was 561 IU/ml (CCZ), 1058 IU/ml (CWG), 309 IU/ml (HPCZ), and 478 IU/ml (HPWG).

Preparation and Physical Properties of Zein-Coated High-Amylose Corn Starch Film

The objective of this study was to prepare the edible composite films using high-amylose corn starch (HACS) and corn zein and to determine their physical properties. HACS was gelatinized using the specially designed high-pressure container. HACS film containing 20 g sorbitol/100 g as a plasticizer had suitable physical properties. The HACS film coated with corn zein containing 20 g oleic acid/100 g had moderate physical properties and barrier properties.

Nisin Diffusion in Protein Films: Effects of Film Type and Temperature

ABSTRACT: Protein films [cast corn zein (CCZ), heat‐pressed corn zein (HPCZ), cast wheat gluten (CWG), and heat‐pressed wheat gluten (HPWG)] were studied at different exposure temperatures (5, 25, 35, and 45 °C) to determine nisin diffusion in aqueous model systems. Kinetics of nisin diffusion in protein films followed a Fickian diffusion model. The CCZ had the lowest nisin diffusivity and highest nisin retention. Diffusivities in HPCZ, CWG, and HPWG films were not significantly different. Temperature dependence of nisin diffusion in all films followed an Arrhenius model, which indicated no morphological changes within 5 to 45 °C. The activation energy for nisin diffusion in corn‐zein films was higher than that in wheat‐gluten films.

Preparation of plastic and biopolymer multilayer films by plasma source ion implantation.

The plasma source ion implantation (PSII) technique was used to improve the adhesion between linear low-density polyethylene (LLDPE) and biopolymer. LLDPE was treated with the PSII using O(2) or CF(4) gas to modify its surface. After modification, chitosan or corn zein was used for coating on LLDPE. Wettability of the LLDPE surface was evaluated with a contact angle meter by the sessile drop method. X-ray photoelectron spectroscopy (XPS) was used to analyze the LLDPE surface. Before and after treatment, in the case of LLDPE treated with O(2) PSII, oxygen-containing functional groups were formed on the implanted surface. In the CF(4) PSII treated LLDPE, it was observed that the fluorine concentration on the surface of LLDPE remarkably increased and hydrophobic groups were formed by chemical reaction. Bilayer films coated with chitosan or corn zein showed 10 times lower oxygen permeability. Tensile strength of multilayer films was decreased a little compared with that of LLDPE. The plastic and biopolymer multilayer films have potential for food packaging application because of their O(2) gas barrier property and easy recyclability of the multilayer film.

명태 단백질로 제조한 가식성 필름의 물성 개선

The edible films were prepared from the protein of alaska pollack, Theragra chalcogrmma. Effects of plasticizer, cross linker and laminated film on physical properties such as tensile strength (TS), elongation (E) and water vapor permeability (WVP) of films were investigated. In adding various kinds of plasticizers, TS of the films prepared with propylene glycol (PG) was the highest, and followed sorbitol, polyethylene glycol 200 (PEG 200) and glycerol. Elongation of the films prepared with glycerol was the highest, then sorbitol, PEG 200 and PG. WVP of films showed lower in order of PG, sorbitol, glycerol and PEG 200.75 decreased with the increment of plasticizer concentration, but elongation increased, The addition of both PG and PEG 200 effected weakly on elongation, so they were inadequate as plasticizer for the film. Mixtures of glycerol and sorbitol, which showed opposing both TS and elongation in the films, could control the physical properties of the films. With increasing relative humidity, TS decreased, while elongation and equilibrium moisture content increased. By adding the cross linkers such as ascorbic acid, citric acid and succinic acid, TS and m of films increased, while elongation decreased. Ascorbic acid, citric acid, succinic acid were most effective for TS at 0.2, 0.1 and , respectively. Laminated film with alaska pollack protein and corn zein improved TS above two times, reduced WVP about , as compared with the Elm from alaska pollack protein. Two films did not show the difference to oxygen permeability, but they showed about tenfold greater oxygen resistance than polyethylene film. Laminated film showed higher b and E value of color difference, lower a and L value than the film from alaska pollack protein.