Aloe vera Oil-Added Agar Gelatin Edible Films for Kashar Cheese Packaging.

In recent years, there has been a growing interest in edible and biodegradable films due to their sustainability, environmental friendliness, and their functionality. In this work, Aloe vera oil-added agar-gelatin films were prepared and characterized in terms of water content, degree of swelling, water solubility, antioxidant activity, and antimicrobial activity. The possibility of using these edible films for Kashar cheese packaging during cold storage was investigated. Physical, chemical, and microbiological properties of the packaged cheese samples were examined for 20 days of cold storage at 4 °C. A. vera oil-added films were found to have antibacterial activity against Escherichia coli and Staphylococcus aureus and antifungal activities against Aspergillus niger and Candida albicans. A. vera oil-added films showed high antioxidant activities, increasing with the increasing A. vera oil percentage in the formulation. The current study showed that at the end of 20 days of storage period, bacterial growth in A. vera oil-incorporated film-covered samples was 2.30 log CFU/g lower than the control samples, and the amount of yeast and mold in A. vera oil-added film-covered samples was 3.37 log CFU/g lower than control samples. This shows the efficiency of A. vera oil-incorporated agar-gelatin films during the refrigerated storage period. Our data evidenced the positive effect of A. vera oil-added agar-gelatin films on Kashar cheese packaging as an innovative and sustainable technique to maintain cheese quality and prevent food loss during storage.

New biocompatible antibacterial wound dressing candidates; agar-locust bean gum and agar-salep films.

Agar has numerous applications in biomedical and biopharmaceutical fields in gel form. However the hard and tough nature of agar films and their vulnerability to microbial attacks prevent their usage in wound dressing applications. In this work, agar - locust bean gum (LBG) and agar - salep films were prepared for the first time to improve its physical, antimicrobial and cell viability properties. LBG and salep incorporated films resulted in higher antimicrobial and cell viability properties than agar films, which are very important in wound dressing applications. Agar - LBG films had higher water vapor permeabilities and were insoluble in water and in phosphate buffer solutions. Salep incorporation resulted in lower water vapor permeability and films were soluble in both media. All films were transparent, allowing good observability. With LBG and salep addition, lower tensile strength films were obtained and thicknesses of all films were appropriate for wound dressing applications. Due to their solubility, agar - salep films can be preferred especially for the cases where removal from the wound without damaging the tissue structure is a priority.

A detailed investigation of the effect of calcium crosslinking and glycerol plasticizing on the physical properties of alginate films.

Alginates attract growing interest due to their biocompatible and biodegradable nature. Here, a wide spectrum of glycerol added alginate films (from 0 to 30% w/w, glycerol/alginate) were prepared and crosslinked by four different concentrations of calcium chloride solutions (0.5, 1, 1.5, 2%, w/w). This is the first investigation involving variation of both the plasticizer and crosslinker concentrations in twenty different compositions. It is shown that glycerol and calcium have a synergic effect on the mechanical properties and the behavior of crosslinked and plasticized alginate films cannot be predicted by studies, which vary only one of these, keeping the other constant. Without glycerol, crosslinking had a negligible effect on tensile behavior, but with glycerol addition, the effect of crosslinking became evident in mechanical properties. Calcium and glycerol concentrations exhibited a combined effect, displaying optimum combinations with good strength and fracture strain properties. Crosslinking increased the thermal resistance of all films. Low crosslinked high swelling films and highly crosslinked low swelling films were prepared. Water vapor permeability of films decreased regularly with increasing calcium concentration. The films exhibited high transmittance in the visible region. The results showed that alginate films have an appreciable potential in wound dressing and food packaging applications.

Stress relaxation and humidity dependence in sodium alginate-glycerol films.

The control of viscoelastic properties of alginate biopolymer that mimics the matrix properties of biological substrates plays an important role for the success of its biomedical applications. For this purpose stress relaxation behavior of glycerol plasticized sodium alginate films is characterized at room temperature as a function of the glycerol concentration ranging up to 40%. A series of experiments are thus conducted at relative humidity levels of 38 ±â€¯1% and 51 ±â€¯1%. The glycerol content is demonstrated to amplify the effect of humidity on relaxation profiles. In the case of 30% glycerol, normalized stress at the level of 65% is recorded at the end of the first 30 min at the low humidity level, whereas the corresponding value drops to 8% with increased humidity. Alginate films with no glycerol content exhibit much higher normalized stresses of 89% and 73% at low and high humidity levels, respectively. In addition, stress relaxation is observed to continue well beyond the first 30 min, especially for glycerol concentrations lower than 30%, where 9-hour parameters for a stretched exponential Kohlrausch - Williams - Watts function are reported demonstrating the importance of relaxation time for successful modeling.

Evolution of composition, molar mass, and conductivity during the free radical copolymerization of polyelectrolytes.

Despite their importance in biological and technological contexts, copolymeric polyelectrolytes (or "copolyelectrolytes") continue to present challenges to theorists and experimentalists. The first results of a unified approach to the kinetics and mechanisms of copolyelectrolyte synthesis and the physical characteristics of the resulting polymers are presented. The free radical copolymerization of 4-vinylbenzenesulfonic acid sodium salt and acrylamide was monitored using automatic continuous online monitoring of polymerization reactions (ACOMP), from which the average bivariate composition and mass distributions were determined. Composition drift was related to the evolution of conductivity. In some cases bimodal populations of copolyelectrolyte and homopolymeric poly(acrylamide) resulted, i.e., blends of copolyelectrolyte and neutral homopolymer. The end-product scattering behavior depended on whether the end-product was bimodal or not, as demonstrated using automatic continuous mixing (ACM) in conjunction with light scattering and viscosity. Negative light-scattering third virial coefficients were found for bimodal end-products. This combined approach may allow connecting the synthesis kinetics to the resulting "trivariate" distribution of composition, molar mass, and linear charge density, which in turn controls the properties of end-product solutions, such as chain conformations, interparticle interactions, viscosity, interactions with colloids and other polymers, phase separation, etc. Unified results may allow testing and improvement of existing polyelectrolyte theories, development of new quantitative physicochemical models, provide advanced characterization methods, set the stage for studying more complex copolyelectrolytes, such as hydrophobically modified ones, and provide tools for ultimately controlling and tailoring the synthesis and properties of copolyelectrolytes.