John M. Krochta

Oxygen and aroma barrier properties of edible films: A review

Interest in maintaining food quality while reducing packaging waste has encouraged the exploration of the oxygen and aroma transport properties of edible films. This review article introduces the theoretical basis for oxygen and aroma barrier property determination and presents a brief historical per- spective of the development of barrier polymers. The effects of structure and composition on mass transport in edible films are examined and compared with those of the more thoroughly investigated synthetic polymers. A survey of edible film oxygen and aroma barrier research is presented; areas re- quiring additional investigation are suggested, for applications as well as basic research. The potential of edible films and coatings to provide excellent aroma retention and superior oxygen barrier properties makes this quite a promising area of research for both food and packaging scientists.

Plasticizer effect on mechanical properties of β-lactoglobulin films

Abstract The mechanical properties (elastic modulus, EM; tensile strength, TS and % elongation, %E) of β-lactoglobulin (β-Lg) films plasticized with different plasticizers were determined. Six plasticizer types were studied over a range of concentrations. Propylene-glycol-plasticized β-Lg films were the most brittle, with mechanical properties independent of plasticizer content. Films with other plasticizers studied (glycerol, Gly; sorbitol, Sor; polyethylene glycol, PEG 200 and PEG 400 and sucrose, Suc) exhibited negative exponential dependence on plasticizer concentration for EM and TS, while they exhibited linear dependence on plasticizer concentration for %E. The EM and TS data for each plasticizer were fitted with an exponential model, while %E data were fitted with a linear model to quantify the plasticizer effect. The EM0, TS0 and %E0 of β-Lg films without plasticizer determined from the fitted equations were 1500, 37.28 MPa and 0, respectively. The kEM,kTS and kE values determined from the fitted EM, TS and %E data, respectively, reflect the efficiency of plasticizers. The kEM,kTS and kE values indicate that plasticizer efficiency generally decreased in the order Gly, PEG 200, PEG 400, Sor and Suc, on the bases of mole plasticizer-oxygen-atom/mole β-Lg and mass plasticizer/mass β-Lg. These results reflect the effect of plasticizer composition, size and shape. The kEM,kTS and kE value order was reversed when the basis was changed to mole plasticizer/mole β-Lg. The latter results clearly reflect the effect of plasticizer number of O atoms.

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.

Water vapor permeability properties of edible whey protein-lipid emulsion films

The water vapor permeability (WVP) of whey protein emulsion films was investigated. The exponential effect of relative humidity on the WVP of whey protein films was reduced through lipid incorporation. Film orientation had a significant effect on WVP due to emulsion separation during film formation. Heat denaturation of whey proteins lowered emulsion film WVP. Increasing fatty acid and fatty alcohol chainlengths significantly reduced WVP, as did increasing lipid concentration. The WVPs of fatty acids, fatty alcohols and beeswax were compared in whey protein-lipid emulsion films. Scanning and transmission electron microscopy revealed the crystalline microstructure of lipid particles in emulsion films.

Edible Packaging Materials

Research groups and the food and pharmaceutical industries recognize edible packaging as a useful alternative or addition to conventional packaging to reduce waste and to create novel applications for improving product stability, quality, safety, variety, and convenience for consumers. Recent studies have explored the ability of biopolymer-based food packaging materials to carry and control-release active compounds. As diverse edible packaging materials derived from various by-products or waste from food industry are being developed, the dry thermoplastic process is advancing rapidly as a feasible commercial edible packaging manufacturing process. The employment of nanocomposite concepts to edible packaging materials promises to improve barrier and mechanical properties and facilitate effective incorporation of bioactive ingredients and other designed functions. In addition to the need for a more fundamental understanding to enable design to desired specifications, edible packaging has to overcome challenges such as regulatory requirements, consumer acceptance, and scaling-up research concepts to commercial applications.

Plasticizers in edible films and coatings

Publisher Summary This chapter summarizes the advantages and disadvantages of plasticizers, plasticizers used, and plasticized-film properties of both polysaccharide- and protein-based films and coatings. Most polysaccharide- and protein-based films and coatings are brittle in nature. To solve this problem, plasticizers are incorporated to enhance the film flexibility and resilience. However, film permeability always increases with increasing plasticizer content. Proper selection of a plasticizer for a given polymer will allow optimization of the film mechanical properties with a minimum increase in film permeability. Common plasticizers for edible films and coatings, include monosaccharides, oligosaccharides, polyols, lipids, and derivatives. Different moisture sorption by various plasticizers contributes to differences in film permeability and mechanical properties. Selection of plasticizers need consideration of the issues of plasticizer compatibility, efficiency, permanence, and economics. The effect of the amount and type of plasticizer on achieving desirable mechanical properties with optimal permeability is of continuing interest to researchers.

Application of casein-lipid edible film emulsions to reduce white blush on minimally processed carrots

White blush on the surface of peeled carrots is a major cosmetic disadvantage in marketing this lightly processed, ready-to-eat product. The loss of quality is exacerbated by surface dehydration. To maintain good appearance, edible coatings consisting of emulsions incorporating caseinates with beeswax, stearic acid or acetylated monoglyceride were tested. All except the latter increased water vapor resistance. Sodium caseinate-stearic acid was particularly effective in ameliorating the disorder.

Optimization of edible coating formulations on zucchini to reduce water loss

Abstract Zucchini ( Cucurbita pepo; melopepo ) fruit were coated with 0.5, 0.75 or 1.0% aqueous solutions of Semperfresh ™ and with different formulations of calcium caseinate-acetylated monoglyceride aqueous emulsions ranging from 2.5 to 7.0% total solids. Semperfresh ™ did not increase water vapor resistance of zucchini. Rates of respiration and ethylene production from coated and uncoated zucchini increased at the beginning of storage at 12.5 and 86% RH, but decreased rapidly thereafter. This type of response is indicative of a temporary metabolic disturbance resulting from preparation and a non-climacteric pattern of respiration. Coatings did not affect internal carbon dioxide or ethylene concentrations. Hue angle and lightness values were not significantly different for coated and uncoated zucchini. Ridge analysis indicated that a maximum water vapor resistance will result from relatively high sodium caseinate and low acetylated monoglyceride contents in edible coatings for zucchini fruit.

Listeria monocytogenes inhibition by whey protein films and coatings incorporating lysozyme.

The effects of whey protein isolate (WPI) films and coatings incorporating lysozyme (LZ) on the inhibition of Listeria monocytogenes both in and on microbial media, as well as on cold-smoked salmon, were studied. The antimicrobial effects of LZ were examined using various growth media by turbidity and plate counting tests. Disc-covering and disc-surface-spreading tests were also used to evaluate the effects of WPI films incorporating LZ. Smoked salmon was used as a model food to test the antimicrobial effects of WPI coatings incorporating LZ, both initially and during storage at 4 and 10 degrees C for 35 days. Tensile properties (elastic modulus, tensile strength, and percentage of elongation), oxygen permeability, and color (Hunter L, a, and b) of WPI films with and without LZ were also compared. LZ inhibited L. monocytogenes in broth and on agar media. The number of cells surviving after LZ treatments depended on the type of media. WPI films incorporating 204 mg of LZ per g of film (dry basis) inhibited the growth of a preparation of 4.4 log CFU/cm2 L. monocytogenes. WPI coatings prepared with 25 mg of LZ per g of coating solution initially inactivated more than 2.4, 4.5, and 3.0 log CFU/g of L. monocytogenes, total aerobes, and yeasts and molds in smoked salmon samples, respectively. The WPI coatings incorporating LZ efficiently retarded the growth of L. monocytogenes at both 4 and 10 degrees C. The anti-L. monocytogenes effect of LZ-WPI coating was more noticeable when the coating was applied before inoculation than when the coating was applied after inoculation. Significantly higher elastic modulus values and lower percentage of elongation and oxygen permeability values were measured with the WPI films incorporating LZ than with the plain WPI films.

Specular reflection, gloss, roughness and surface heterogeneity of biopolymer coatings

The gloss values of biopolymer coatings were predicted by the Fresnel model from solid film refractive index measurements. Measured gloss properties of transparent coatings fit the model better than did those of wax- or lipid-dispersion coatings. Lipid content and particle size of dispersion coatings had a large influence on coating gloss. The effect of surface roughness on gloss was small compared with that of surface heterogeneity. Whey protein isolate and shellac coatings had higher gloss than hydroxypropyl methylcellulose coatings.