Effect of freezing on physical properties of whey protein emulsion films

Chitosan-based nanocomposite films with carnauba wax, rosin resin, and zinc oxide nanoparticles

This work aimed to develop edible emulsion-based barriers in the form of chitosan composite films, with a focus on assessing the impacts of carnauba wax, rosin resin, and zinc oxide nanoparticles on their properties. Six films were produced by casting using chitosan as polymer base and glycerol as plasticizer. Acetic acid and polysorbate 80 were also used to facilitate the dissolution and mixing of the components. The six filmogenic solutions contained chitosan at 1.2% w/v, wax or resin content with 0 or 0.6% m/v and ZnO with 0 or 0.05% m/v. The dried films were characterized according to their chemical, barrier, mechanical, thermal and optical properties. All treatments resulted in flexible films. Chitosan films appeared smoother and more uniform under SEM imaging, while carnauba wax films displayed roughness due to their hydrophobic nature. Wax and resin films were less transparent and water soluble than the chitosan-only films. On the other hand, the addition of ZnO in the formulations increased the solubility of the films. The sorption degree was in line with the solubility results, i.e., films with ZnO presented higher sorption degree and solubility values. All treatments showed low or non-light UV transmission, indicating that the films provide good barrier to UV light. In the visible light region, films of resin with ZnO showed the lowest transmittance values, hence offering a good barrier to visible light. Among the evaluated films, chitosan, and resin films with ZnO nanoparticles were more rigid and resistant to deformation. Overall, films produced with rosin resin and ZnO nanoparticles showed potential improvements in barrier, mechanical, thermal, and optical properties, mainly due to their low water solubility, good UV protection and low permeability to water vapor and oxygen, which are suitable for using in formulations, intended to produce edible films and coatings.

Moisture loss inhibition with biopolymer films for preservation of fruits and vegetables: A review

In cold storage, fruits and vegetables still keep a low respiratory rate. Although cold storage is beneficial to maintain the quality of some fruits and vegetables, several factors (temperature and humidity fluctuations, heat inflow, air velocity, light, etc.) will accelerate moisture loss. Biopolymer films have attracted great attention for fruits and vegetables preservation because of their biodegradable and barrier properties. However, there is still a certain amount of water transfer occurring between storage environment/biopolymer films/fruits and vegetables (EFF). The effect of biopolymer films to inhibit moisture loss of fruits and vegetables and the water transfer mechanism in EFF system need to be studied systematically. Therefore, the moisture loss of fruits and vegetables, crucial properties, major components, fabrication methods, and formation mechanisms of biopolymer films were reviewed. Further, this study highlights the EFF system, responses of fruits and vegetables, and water transfer in EFF. This work aims to clarify the characteristics of EFF members, their influence on each other, and water transfer, which is conducive to improving the preservation efficiency of fruits and vegetables purposefully in future studies. In addition, the prospects of studies in EFF systems are shown.

Chitosan/oxidized Konjac Glucomannan films incorporated with Zanthoxylum Bungeanum essential oil: A novel approach for extending the shelf life of meat

In this study, a novel edible composite film was prepared by chitosan, konjac glucomannan oxidized with ozone for 60 min (OKGM), and Zanthoxylum Bungeanum essential oil (ZEO). The chitosan/OKGM film was fortified with ZEO to assess the physical properties, structure, antioxidant and antibacterial abilities, and pork preservation systematically. Compared to the control group, the addition of 1 % ZEO increased tensile strength by 18.92 % and decreased water solubility, water vapor permeability, and moisture content by 10.05 %, 6.60 %, and 1.03 %, respectively. However, the treatment with ZEO (1.5 % and 2 %) decreased mechanical properties and increased the water vapor permeability. The ultraviolet barrier, antioxidant, and antibacterial abilities of composite films were enhanced by increasing the ZEO addition. Moreover, the COZ-1 film was used to protect the freshness of pork with slow-release behavior of ZEO. The results showed that addition of ZEO significantly decreased the pH value, total viable count, redness, total volatile basic nitrogen, and thiobarbituric acid and increased the hardness of pork after preservation for 10 days. Therefore, the chitosan/OKGM loaded with ZEO film can potentially be used as food packaging, providing new ideas for the research on active packaging materials.

Emulsified blend film based on konjac glucomannan/carrageenan/ camellia oil: Physical, structural, and water barrier properties

The objective of this study was to develop a new hydrophobic film based on konjac glucomannan and kappa-carrageenan (KGM-KC) incorporating camellia oil (CO) (2, 4, and 6 %). CO was directly emulsified as a dispersed phase into KGM-KC matrix. The physical, structural, and water barrier properties of the film were studied. The results of Fourier transform infrared and scanning electron microscopy suggested that CO was successfully distributed in KGM-KC matrix by emulsification. Contact angle of the film indicated that addition of CO increased the hydrophobicity and water-resistance properties of film, which corresponding to the moisture content, total soluble mass, water vapor permeability, water vapor adsorption kinetics and water vapor adsorption isotherms. Addition of CO by emulsification improved thermal stability of film, optical properties, and mechanical properties. In conclusion, the incorporation of CO by emulsification is an effective and promising pathway to improve the properties of polysaccharide-based film.

Effects of Candelilla and Carnauba Wax Incorporation on the Functional Properties of Edible Sodium Caseinate Films

The aim of this study was to evaluate the effects of candelilla (CAN) or carnauba wax (CAR) incorporation on functional properties of edible sodium caseinate (CAS) films. Glycerol and Tween-80 were used as the plasticizer and the emulsifier, respectively. The results showed that the incorporation of waxes increased film opacity, total color differences (∆E), and mechanical resistance and reduced film lightness, water vapor permeability (WVP), and elongation at break. Scanning electron microscopy showed heterogeneous structure of emulsion films with regular distribution of lipid particles. A different internal arrangement was observed as a function of the film composition with both layered and incorporated film structure. Films containing candelilla wax exhibited more regular lipid reorganization, which resulted in better water vapor barrier efficacy and mechanical resistance in comparison to control films. The presence of Tween-80 resulted in better dispersion of lipid particles in film-forming solutions and lower water solubility, lightness, film opacity, and water vapor permeability, whereas the total color differences (∆E) were significantly larger and the improvement in mechanical properties was also achieved.

Oleogel Films Through the Pickering Effect of Bacterial Cellulose Nanofibrils Featuring Interfacial Network Stabilization

As bio-based food packaging materials promise a more sustainable future, this work fabricated edible oleofilms by casting beeswax-in-water Pickering emulsions, which were formed by the physical hybrid particles of bacterial cellulose nanofibrils (BCNFs) and carboxymethyl chitosan (CCS) (BC/CCS). The emulsion droplet size was varied from 4 to 9 μm, and the emulsion index (EI) was all up to 100%. The obtained emulsions exhibited excellent long-term stability, and there was no change in the EI (100%) after the storage of the emulsion for 3 months. Moreover, the environmental temperature had almost no impact on the droplet size and EI of the emulsion. The mechanical properties of the oleofilms were significantly improved by enhancing the content of BC/CCS. There was also a visual reduction in the water vapor permeability (WVP) value, which was lower than 1.1 × 10^-7 g·m^-1·h^-1·Pa^-1. Furthermore, the obtained oleofilms exhibited a notable improvement in surface hydrophobicity, and surprisingly, it could be easily redispersed into water to recover back to the emulsion state without additional high energy mixing. This suggested that this edible oleofilm was prepared by a fully green method by casting Pickering emulsions stabilized by BC/CCS and could extend its application for the development of food-grade coating materials.

Application of Protein-Based Films and Coatings for Food Packaging: A Review

As the IV generation of packaging, biopolymers, with the advantages of biodegradability, process ability, combination possibilities and no pollution to food, have become the leading food packaging materials. Biopolymers can be directly extracted from biomass, synthesized from bioderived monomers and produced directly by microorganisms which are all abundant and renewable. The raw materials used to produce biopolymers are low-cost, some even coming from agrion dustrial waste. This review summarized the advances in protein-based films and coatings for food packaging. The materials studied to develop protein-based packaging films and coatings can be divided into two classes: plant proteins and animal proteins. Parts of proteins are referred in this review, including plant proteins i.e., gluten, soy proteins and zein, and animal proteins i.e., casein, whey and gelatin. Films and coatings based on these proteins have excellent gas barrier properties and satisfactory mechanical properties. However, the hydrophilicity of proteins makes the protein-based films present poor water barrier characteristics. The application of plasticizers and the corresponding post-treatments can make the properties of the protein-based films and coatings improved. The addition of active compounds into protein-based films can effectively inhibit or delay the growth of microorganisms and the oxidation of lipids. The review also summarized the research about the storage requirements of various foods that can provide corresponding guidance for the preparation of food packaging materials. Numerous application examples of protein-based films and coatings in food packaging also confirm their important role in food packaging materials.

Effect of Antioxidant and Antimicrobial Coating based on Whey Protein Nanofibrils with TiO₂ Nanotubes on the Quality and Shelf Life of Chilled Meat

Whey protein nanofibrils (WPNFs) can be used in edible films and coatings (EFCs) because of its favorable functional properties, which rely on its well-ordered β-sheet structures, high hydrophobicity, homogeneous structure, and antioxidant activity. In the present study, WPNF-based edible coatings with glycerol (Gly) as plastic and titanium dioxide nanotubes (TNTs) as antimicrobial agents were studied. TNTs not only showed greater antibacterial activity than titanium dioxide nanoparticles (TNPs), but also increased interactions with WPNFs. The WPNF/TNT film had a smooth and continuous surface and was homogeneous with good mechanical properties. WPNF/TNT edible coatings (ECs) can help improve lipid peroxidation and antioxidant activity, limit microbial growth, reduce weight loss, and extend the shelf life of chilled beef. Given that the WPNF/TNT film components are low cost and show high antioxidant and antimicrobial activity, these optimized films have potential applications for various food products, including raw and chilled meat.

Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review

Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films.