Modification of Physical and Barrier Properties of Edible Wheat Gluten-Based Films

Edible films were produced from wheat gluten-based film-forming solutions. One film was produced as a control. Other types came from subjecting control films to three different soaking treatments. Three additional films were also produced by modifying the control film-forming solution. For all films, selected physical properties and permeability to water vapor and oxygen were measured. Comparisons indicated possible ways to improve the control film. All films were good oxygen barriers but limited water vapor barriers. Films containing hydrolyzed keratin had lower oxygen permeability (83%) and lower water vapor permeability (23%). Films containing mineral oil had lower water vapor permeability (25%). Films soaked in calcium chloride solution and in buffer solution at the isoelectric point of wheat gluten had higher tensile strength (47 and 9%, respectively) and lower water vapor permeability (14% and 13%, respectively). Addition of a reducing agent increased tensile strength (14%). Soaking in lactic acid solution did not improve the standard film properties

Gelatin Manufacturing Process and Product

The present invention overcomes the deficiencies of the prior art by providing a process for manufacturing gelatin including cleaning a fowl-based source of collagen; subjecting the fowl-based source of collagen to at least one water extraction to extract gelatin from the collagen source; and separating the gelatin from any resulting by-products, wherein the process does not require an initial acid or lime pretreatment step. The present invention also includes a product made from this process

Water vapor transport parameters of a cast wheat gluten film

Understanding the mode of transport of water vapor through the film is important for improving the moisture barrier properties of wheat gluten (WG) films. Effective permeability (Peff), solubility (Seff), and diffusion (Deff) coefficients of a hydrophilic cast WG film were determined at 25°C within the relative humidity (RH) range of 0–84% (with a 9–13% RH gradient between upstream and downstream water vapor flux). Peff, Seff, and Deff increased substantially as the RH gradient moved upwards in the RH spectrum. Peff increased by four orders of magnitude from the lowest RH condition of 0–11% (3.8×10−11 g·m/m2·s·Pa) to the highest RH condition of 75–84% (4.1×10−7 g·m/m2·s·Pa). A moisture sorption isotherm of the film at 25°C was constructed. Both the Guggenheim–Anderson–DeBoer (GAB) and the Kuhn moisture sorption isotherm models showed a good fit to the experimental adsorption data. Testing of WG films at the expected conditions of actual use is necessary to quantify the water vapor permeation through the films

Protein film development and property evaluation

Methods were presented in this study for preparing protein films from wheat gluten, corn zein, soy protein isolate, and egg white. Film properties, as related to various processing factors, were evaluated. The oxygen permeability of corn zein, wheat gluten, and wheat gluten/soy protein isolate (2.1:0.9) films was determined at 7, 15, 25, and 35\sp\circC under 0% relative humidity. Data for all three films showed good agreement with the Arrhenius activation energy model. Equations were presented for correcting water vapor transmission data of hydrophilic films, such as protein films. Corn zein and methyl cellulose films were used for validation of the corrective equations. Tensile strength of corn zein and wheat gluten films was found to decrease with relative humidity (23-75%) and to increase with temperature (5-45\sp\circC). Properties of wheat gluten and soy protein isolate films were significantly affected by the pH of film-forming solutions. Wheat gluten and soy protein isolate films of higher tensile strength were obtained under alkaline, rather than acidic, conditions. Glass transition, mechanical, and water vapor barrier properties of wheat gluten films containing glycerin, sucrose, glycerin-sucrose, or glycerin-sorbitol were studied. Glycerin and sucrose were immiscible and the gluten film containing both solutes showed two separate glass transitions ($-$58\sp\circC and $-$5\sp\circC). The glass transition temperature of films showed low correlation with water vapor barrier and mechanical properties. Gluten:glycerin:sorbitol films (15:3:3 w/w) showed a single effective glass transition temperature ($-$42\sp\circC). Soy protein isolate films heated at 80 or 95\sp\circC for 2, 6, 14, and 24 h had increased tensile strength and $+$b (yellowness) Hunter color values and reduced elongation at break, water solubility, and water vapor permeability. Film properties were affected more by heating at 95\sp\circC than 80\sp\circC. Films were cast from aqueous alkaline solutions of dried egg white. At equal concentrations, polyethylene glycol-plasticized films had greater tensile strength and elongation at break than glycerin- or sorbitol-plasticized films. Partial substitution of egg white with dried yolk solids decreased film tensile strength and elongation at break and increased $-$a (greenness) and $+$b (yellowness) Hunter color values

Gelatin Manufacturing Process and Product

The present invention overcomes the deficiencies of the prior art by providing a process for manufacturing gelatin including cleaning a fowl-based source of collagen; subjecting the fowl-based source of collagen to at least one water extraction to extract gelatin from the collagen source; and separating the gelatin from any resulting by-products, wherein the process does not require an initial acid or lime pretreatment step. The present invention also includes a product made from this process

Films from Laboratory-Extracted Sorghum Kafirin

There has been increased interest in development of biopolymer films and coatings from protein, polysaccharide, and lipid materials in recent years. The qualities of renewability, degradability, compostability, and edibility make such films particularly appealing for food and nonfood packaging applications. Moreover, wide commercialization of biopolymer films will provide a value-added innovative use for traditional agricultural commodities as sources of film-forming materials. Research findings on production, properties, and potential applications of edible films have been reviewed (Krochta 1992, Conca and Yang 1993, Gontard and Guilbert 1994). Protein films in particular have been discussed in detail by Gennadios et al (1994a) and by Torres (1994). Zein, the prolamin fraction of corn proteins, is used in formulations of protective coatings for confectionery items, shelled nuts, and pharmaceutical tablets (Gennadios et al 1994a). Several recent studies have focused on development and property evaluation of zein-based films (Aydt et al 1991; Gennadios et al 1993a,b; Park et al 1994b; Park and Chinnan 1995; Yamada et al 1995), zein-paper laminates (Trezza and Vergano 1994), and methylcellulose and zein-fatty acid laminates (Park et al 1994c, 1996). Functionality of zein in barrier packaging for popcorn (Wu and Schwartzberg 1992), tomatoes (Park et al 1994a), cooked turkey (Herald et al 1996), and shell eggs (Wong et al 1996) has been evaluated

Thermomechanical Behavior of Wheat Gluten Films: Effect of Sucrose, Glycerin, and Sorbitol

Glass transition temperature (Tg) and mechanical and water vapor barrier properties of wheat gluten films containing glycerin, sucrose, glycerin-sucrose, and glycerin-sorbitol were studied. Glycerin and sucrose were immiscible; the wheat gluten film containing both solutes showed two separate thermal transitions (-58°C and -5°C, respectively). The low temperature (low-T) transition (-58°C) was due to a glycerin-rich region. The low-T tan δ peak height influenced the tensile strength and elongation linearly and the water vapor permeability (WVP) curvilinearly. However, the Tg failed to change with solute composition and exhibited low correlation with barrier and mechanical properties. Initial addition of glycerin increased the WVP dramatically. Sucrose decreased the WVP (only slightly), but resulted in a rigid and fragile film. The gluten-glycerin-sorbitol film at a ratio of 15:3:3 (w/w), 16.7% moisture (wb), showed a single effective Tg (-42°C) and intermediate values for tensile strength, percent elongation, and WVP, which were between those of the 15:6:0 and 15:4:2 gluten-glycerin-sucrose films

Water vapor transport parameters of a cast wheat gluten film

Understanding the mode of transport of water vapor through the film is important for improving the moisture barrier properties of wheat gluten (WG) films. Effective permeability (Peff), solubility (Seff), and diffusion (Deff) coefficients of a hydrophilic cast WG film were determined at 25°C within the relative humidity (RH) range of 0–84% (with a 9–13% RH gradient between upstream and downstream water vapor flux). Peff, Seff, and Deff increased substantially as the RH gradient moved upwards in the RH spectrum. Peff increased by four orders of magnitude from the lowest RH condition of 0–11% (3.8×10−11 g·m/m2·s·Pa) to the highest RH condition of 75–84% (4.1×10−7 g·m/m2·s·Pa). A moisture sorption isotherm of the film at 25°C was constructed. Both the Guggenheim–Anderson–DeBoer (GAB) and the Kuhn moisture sorption isotherm models showed a good fit to the experimental adsorption data. Testing of WG films at the expected conditions of actual use is necessary to quantify the water vapor permeation through the films

Sodium dodecyl sulfate treatment improves properties of cast films from soy protein isolate

The manufacture of edible/biodegradable films or coatings can potentially add value to soy protein. This study was conducted to determine the effect of sodium dodecyl sulfate (SDS) on selected physical properties of glycerin-plasticized soy protein isolate (SPI) films. Films were cast from heated (70 °C for 20 min), alkaline (pH 10) aqueous solutions of SPI (5 g/100 ml water), glycerin (50% w/w of SPI), and SDS (0, 5, 10, 20, 30, or 40% w/w of SPI). Tensile strength (TS), elongation at break (E), moisture content (MC), total soluble matter (TSM), water vapor permeability (WVP), and color values (L, a, and b) were determined after conditioning film specimens at 25 °C and 50% relative humidity (RH) for 2 days. SDS reduced (P \u3c 0.05) film TS by as much as 43% for films with 40% SDS (6.2 vs. 10.9 MPa for control SPI films). In contrast, film E increased (P \u3c 0.05) notably with addition of SDS even at 5%. Films with SDS had smaller (P \u3c 0.05) MC and larger (P \u3c 0.05) TSM values than control SPI films. Films containing 10% or more SDS had lower WVP values than control SPI films by as much as 50%. Increased yellowness, evidenced by greater (P \u3c 0.05) + b color values, was noted for films with high amounts (20, 30, or 40%) of SDS. Changes in tensile, solubility, and water vapor barrier properties of SPI films due to the addition of SDS were largely attributed to disruption of hydrophobic associations among neighboring protein molecules as the non-polar portions of the SDS molecules attached onto hydrophobic amino acid residues within the film structure. It was demonstrated that adding anionic surfactant SDS to film-forming solutions prior to casting could greatly modify the properties of SPI films. In particular, SDS improved the water vapor barrier ability and the extendibility of SPI films, both desirable attributes when assessing the potential of such films for packaging applications