Glycerol improved film extensibility but reduced film puncture strength, elasticity, and water vapor barrier properties. The plasticizing effect of water was highly temperature dependent. During hydration of gluten film, a sharp decrease in puncture strength, elasticity, and an increase of extensibility and water vapor transmission rate were observed at 5, 30 and 5o'C for respective water contents of 30 (0,8 a,), 15 (0,7 a,) and 5% (0,4 a,). This was related to disruptive waterpolymer hydrogen bonding and glass-to-rubber transition.

An edible wheat gluten film was developed and effects of gluten concentration, ethanol concentration (ET) and pH of the film-forming solution on various film properties were evaluated using Response Surface Methodology. pH and ethanol concentration had strong interactive effects on film opacity, water solubility and water vapor permeability. A simultaneous variation of ethanol concentration and pH between 32.5% ET, pH 4 and 45% ET, pH 2 resulted in homogeneous and transparent film with relatively low water solubility. The lowest water vapor permeability would be expected with 20% ethanol concentration and pH 6. Mechanical properties were mainly affected by gluten concentration and pH. The most resistant film was obtained at high gluten concentration (12.5%) and pH 5.

Edible composite films comprised of wheat gluten as the structural matrix and various concentrations of different lipids as the moisture barrier component were tested for water vapour permeability, dispersion in water, opacity and mechanical properties. The effects of lipids on the functional properties of gluten-based composite films depended on the lipid characteristics and on the interactions between the lipid and the protein structural matrix. Beeswax, a solid and highly hydrophobic lipid, was the most effective lipid for improving moisture barrier properties of films; but these films were opaque, weak and disintegrated easily in water. Combining wheat gluten proteins with a diacetyl tartaric ester of monoglycerides reduced water vapour permeability, increased strength and maintained transparency.

Edible films o r coatings have provided an interesting and often essential complementary means f o r controlling the quality and stability of numerous food products. There are many potential uses of edible films (e.g. wrapping various products, individual protection o f dried fruits, meat and fish, control of internal moisture transfer in pizzas, pies, etc.) which are based on t h e films properties (e.g. organoleptic, mechanical, gas and solute barrier). Polysaccharide (cellulose, starch, dextrin, vegetable and other gums, etc) and protein (gelatin, gluten, casein, etc) based films have suitable mechanical and organoleptic properties, while wax (beeswax, carnauba wax, etc) and lipid or lipid derivative films have enhanced water vapour barrier properties. The film-forming technology, solvent characteristics, plasticizing agents, temperature effects, solvent evaporation rate, coating operation and usage conditions o f the film (relative humidity, temperature) can also substantially modify the ultimate properties o f the film.

Aims:  To investigate the relation between the chemical structure and the antimicrobial activity of carvacrol, eugenol, menthol and two synthesized carvacrol derivative compounds: carvacrol methyl ether and carvacryl acetate against bacteria, Escherichia coli, Pseudomonas fluorescens, Staphylococcus aureus, Lactobacillus plantarum, Bacillus subtilis, a yeast Saccharomyces cerevisiae and one fungi Botrytis cinerea. Methods and Results:  The antimicrobial activity was tested in liquid and vapour phases, by both broth liquid and microatmosphere methods, respectively. The same classification of the compound's antimicrobial efficiency was found with both methods. Eugenol and menthol exhibited a weaker antimicrobial activity than carvacrol, the most hydrophobic compound. Carvacryl acetate and carvacrol methyl ether were not efficient, indicating that the presence of a free hydroxyl group is essential for antimicrobial activity. Conclusions:  The different extents of antimicrobial aroma compounds’ efficiency showed that hydrophobicity is an important factor and the presence of a free hydroxyl group and a delocalized system allows proton exchange. Significance and Impact of the Study:  This study has identified the importance of the hydrophobicity and the chemical structure of phenolic aroma compounds for antimicrobial activity and may contribute to a most rational use of these compounds as antimicrobial agent.

Cereal Chem. 75(1):1-9Advantages, types, formation, and properties of agricultural packaging materials based on proteins, with examples, are reviewed in detail. Proteins have long and empirically been used to make biodegradable, renewable, and edible packaging materials. Numerous cereal and vegetable proteins (such as corn zein, wheat gluten, and soy proteins) and animal proteins (such as milk proteins, collagen, gelatin, keratin, and myofibrillar proteins) are commonly used to form agricultural packaging materials. Two technological processes have been investigated to make materials based on proteins: the "wet (or solvent) process" based on dispersion or solubilization of proteins in a solvent medium, and the "dry process" based on the thermoplastic properties of proteins under low water content conditions. The macroscopic properties (including solubility in water, mechanical properties, and barrier properties) of agricultural packaging materials based on proteins are dependent mainly on the structure of the macromolecular three-dimensional network and on interactions between proteins, plasticizers, and cross-linking agents.

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