How composition and process parameters affect volatile active compounds in biopolymer films

Development of sodium alginate-pectin biodegradable active food packaging film containing cinnamic acid

Plastics are still the most popular food packaging material, and many of them end up in the environment for a long period. Besides, due to packaging material's inability to inhibit microbial growth, beef often contains microorganisms that affect its aroma, colour, and texture. Cinnamic acid is categorized as generally recognised as safe and is permitted for use in food, however, the development of biodegradable food packaging film with cinnamic acid has never been conducted before. Thus, this present study was aimed to develop a biodegradable active packaging material for fresh beef using sodium alginate and pectin. The film was successfully developed with solution casting method. The films' thickness, colour, moisture level, dissolution, water vapour permeability, bending strength, and elongation at break were comparable to those of polyethylene plastic film in terms of these attributes. The developed film also showed the degradability in soil of 43.26% in a duration of 15 days. Fourier Transform Infrared (FTIR) spectra showed that cinnamic acid was successfully incorporated with the film. The developed film showed significant inhibitory activity on all test foodborne bacteria. On Hohenstein Challenge Test, a 51.28-70.45% reduction on bacterial growth was also observed. The antibacterial efficacy of the established film by using fresh beef as food model. The meats wrapped with the film showed significant reduction in bacterial load throughout the experimental period by 84.09%. The colour of the beef also showed significant different between control film and edible film during 5 days test. Beef with control film turned into dark brownish and beef with cinnamic acid turn into light brownish. In conclusion, sodium alginate and pectin film with cinnamic acid showed good biodegradability and antibacterial activity. Further studies can be conducted to investigate the scalability and commercial viability of this environmental-friendly food packaging materials.

Eugenol loaded chitosan nanoemulsion for food protection and inhibition of Aflatoxin B1 synthesizing genes based on molecular docking

The present investigation entails the fabrication and characterization of nanometric emulsion of eugenol (Nm-eugenol) encompassed into chitosan for assessing bio-efficacy in terms of in vitro antifungal actions, antiaflatoxigenic potential, and in situ preservative efficacy against Aspergillus flavus infestation and aflatoxin B₁ (AFB₁) mediated loss of dietary minerals, lipid triglycerides and alterations in composition of important macronutrients in stored rice. Nm-eugenol characterized by SEM, XRD, and FTIR exhibited biphasic burst release of eugenol. Reduction in ergosterol and methylglyoxal (AFB₁-inducer) content after Nm-eugenol fumigation depicted biochemical mechanism of antifungal and antiaflatoxigenic activities. In silico 3D homology docking of eugenol with Ver-1 gene validated molecular mechanism of AFB₁ inhibition. Further, significant protection of rice seeds from fungi, AFB₁ contamination and preservation against loss of rice minerals, macronutrients and lipids during storage suggested deployment of chitosan as a biocompatible wall material for eugenol encapsulation and application as novel green preservative for food protection.

Application of Supercritical Solvent Impregnation for Production of Zeolite Modified Starch-Chitosan Polymers with Antibacterial Properties

In the present study, supercritical solvent impregnation (SSI) has been applied to incorporate thymol into bio-composite polymers as a potential active packaging material. Thymol, a natural component with a proven antimicrobial activity, was successfully impregnated into starch-chitosan (SC) and starch-chitosan-zeolite (SCZ) films using supercritical carbon dioxide (scCO₂) as a solvent. Experiments were performed at 35 °C, pressures of 15.5 and 30 MPa, and an impregnation time in the range of 4–24 h. The highest impregnation yields of SC films with starch to chitosan mass ratios of 1:1 and 1:2 were 10.80% and 6.48%, respectively. The addition of natural zeolite (15–60%) significantly increased the loading capacity of films enabling thymol incorporation in a quantity of 16.7–27.3%. FTIR and SEM analyses were applied for the characterization of the films. Mechanical properties and water vapor permeability of films before and after the impregnation were tested as well. Thymol release kinetics in deionized water was followed and modeled by the Korsmeyer-Peppas and Weibull model. SCZ films with thymol loading of approximately 24% exhibited strong antibacterial activity against E. coli and methicillin-resistant Staphylococcus (S.) aureus (MRSA).

Active Food Packaging Based on Biopolymers and Aroma Compounds: How to Design and Control the Release

Aroma compounds are known to be efficient active agents for a broad range of applications (antimicrobial, anti-oxidant, insect repellent…) that are highly sought when aiming at extending shelf life of food or biological products. However, they are intrinsically odorant and volatile at ambient temperature, which restricts the processing routes used to introduce them in a polymeric matrix and can affect their mode of action and limit efficiency. Indeed, due to their high sensitivity toward temperature they can be lost or transformed during processing. Acting after being released in the headspace, their concentration has to be controlled to avoid any odorant contamination of the targeted products. Hence, the ability for an aroma compound to be retained in a polymeric matrix, and then released when submitted to a triggering effect, are the two main requirements that should be satisfied. The volatile nature of the aroma compound offer the possibility when introduce in the packaging to act by direct or indirect contact with the product and thus to be used in different ways; as a coating layer directly applied on the product surface, as a self-supported film or as coated paper when associated with a paper sheet, as well as an object that could be inserted in the package. As biopolymers such as proteins and polysaccharides are able to retain aroma compounds but also to favor their release by modification of their structure when the relative humidity (RH) and temperature change, they are relevant carriers of these specific aroma compounds. Examples of how active packaging systems with limonene, eugenol and carvacrol as active agents were designed and elaborated. These examples will be presented with a special focus on the processing conditions and the way to improve their aroma compound retention and the release control (biopolymer nature, cyclodextrin clay addition…). Avrami's equation has been used to model the transfer of aroma compound and to advantageously compare it taking into account the mechanism in relation to the biopolymer structural changes.

Characterization of Active Edible Films based on Citral Essential Oil, Alginate and Pectin

Thermal, structural and physico-chemical properties of different composite edible films based on alginate and pectin with the addition of citral essential oil (citral EO) as an agent to improve barrier properties, were investigated. The obtained films were clear and transparent, with a yellow hue that increased with citral EO addition. All the films displayed good thermal stability up to 160 °C, with a slight improvement observed by increasing the amount of citral EO in the composites. Gas transmission rate (GTR) strongly depended on the polymer structure, gas type and temperature, with improvement in barrier performance for composite samples. Also, citral EO did not exert any weakening action on the tensile behavior. On the contrary, an increase of the elastic modulus and of the tensile strength was observed. Lastly, water contact angle measurements demonstrated the dependence of the film wettability on the content of citral EO.

Collagen from Cartilaginous Fish By-Products for a Potential Application in Bioactive Film Composite

The acid solubilised collagen (ASC) and pepsin solubilised collagen (PSC) were extracted from the by-products (skin) of a cartilaginous fish (Mustelus mustelus). The ASC and PSC yields were 23.07% and 35.27% dry weight, respectively and were identified as collagen Type I with the presence of α, β and γ chains. As revealed by the Fourier Transform Infrared (FTIR) spectra analysis, pepsin did not alter the PSC triple helix structure. Based on the various type of collagen yield, only PSC was used in combination with chitosan to produce a composite film. Such film had lower tensile strength but higher elongation at break when compared to chitosan film; and lower water solubility and lightness when compared to collagen film. Equally, FTIR spectra analysis of film composite showed the occurrence of collagen-chitosan interaction resulting in a modification of the secondary structure of collagen. Collagen-chitosan-based biofilm showed a potential UV barrier properties and antioxidant activity, which might be used as green bioactive films to preserve nutraceutical products.

Barrier, structural and mechanical properties of bovine gelatin-chitosan blend films related to biopolymer interactions

BACKGROUND

The increased use of synthetic packaging films has led to a high ecological problem due to their total non-biodegradability. Thus, there is a vital need to develop renewable and environmentally friendly bio-based polymeric materials. Films and coatings made from polysaccharide polymers, particularly chitosans and gelatins have good gas barrier properties and are envisaged more and more for applications in the biomedical and food fields, as well as for packaging. In this study a casting method was used to develop an edible plasticised film from chitosan and gelatin. Aiming to develop a blend film with enhanced properties, the effects of mixing chitosan (CS) and gelatin (G) in different proportions (CS:G, 75:25, 50:50, 25:75, w/w) on functional and physico-chemical properties have been studied.

RESULTS

Mean film thickness increased linearly (R2 =0.999) with surface density of the film forming solution. An enhancement of mechanical properties by increasing the tensile strength (38.7±11 MPa for pure chitosan and 76.8±9 MPa for pure gelatin film) was also observed in blends, due to gelatin content.When the gelatin content in blend filmswas increased an improvement of both water vapour barrier properties [(4±0.3)×10(-10) g m(-1) s(-1) Pa(-1) for pure chitosan and (2.5±0.14)×10(-10) g m(-1) s(-1) Pa(-1) for pure gelatin, at 70% RH gradient] and oxygen barrier properties ((822.62±90.24)×10(-12) g m(-1) s(-1) Pa(-1) for blend film chitosan:gelatin (25:75 w/w) and (296.67±18.76)×10(-12) g m(-1) s(-1) Pa(-1) for pure gelatin was observed. Fourier transform infrared spectra of blend films showed a shift in the peak positions related to the amide groups (amide-I and amide-III) indicating interactions between biopolymers.

CONCLUSIONS

Addition of gelatin in chitosan induced greater functional properties (mechanical, barrier) due to chemical interactions, suggesting an inter-penetrated network.

Combined effects of drying methods, extract concentration, and film thickness on efficacy of antimicrobial chitosan films

An idea of using a suitable drying method to minimize the loss of added antimicrobial agent and, at the same time, to modify the structure, and hence the release characteristics of chitosan films was proposed. Chitosan film-forming solution was incorporated with galangal extract (0% and 1.5% w/w) and formed into films with the thickness of 15 and 30 μm via hot air drying (HD) (40 °C) and low-pressure superheated steam drying (LPSSD) (70 °C, 10 kPa). The extract retention, release characteristics, and antimicrobial efficacy of the films were then assessed; fresh-cut cantaloupe was used as the test food material, while Staphylococcus aureus was the test pathogenic microorganism. The retention and release of 1,8-cineole, a major bioactive compound in the galangal extract, was monitored during 5-d storage at 25 °C. The film swelling was also evaluated and their results used to interpret the release characteristics of 1,8-cineole from the films to the cantaloupe. At the same thickness, the films prepared by HD had lower extract retention and higher degree of swelling, thus exhibiting faster extract release and lower antimicrobial efficacy than the films prepared by LPSSD. Within the same drying method, the increased film thickness led to higher extract retention and antimicrobial efficacy. The concentration of the extract in the cantaloupe matched well with the extract retention and release characteristics as well as the antimicrobial efficacy of the films.

PRACTICAL APPLICATION

The results of this work illustrate the feasibility of using a suitable drying technology to improve the quality of antimicrobial films from edible biopolymer and form the basis for future development of an improved antimicrobial film production process.

Effect of relative humidity on carvacrol release and permeation properties of chitosan based films and coatings

The influence of water vapour conditions on mass transport and barrier properties of chitosan based films and coatings were studied in relation to surface and structural properties. Water contact angles, material swelling, polymer degradation temperature, barrier properties (PO2, PCO2, WVP) and aroma diffusion coefficients were determined. The solvent nature and the presence of carvacrol influenced the surface and structural properties and then the barrier performance of activated chitosan films. Increasing RH from 0% to 100% led to a significant increase in material swelling. The plasticization effect of water was more pronounced at high humid environment, while at low RH the matrix plasticization was induced by carvacrol. The deposit of a thin chitosan layer on polyethylene decreased PO2 and PCO2 both in dry and humid conditions. The carvacrol release from the chitosan matrix was strongly influenced by RH. A temperature increase from 4 to 37°C also had an impact on carvacrol diffusivity but to a lesser extent than RH.