Development and characterization of sodium caseinate edible films cross-linked with genipin

Malva neglecta seed polysaccharide mucilage coating enriched by the Lactobacillus brevis TD4 postbiotics: A promising strategy to promote the shelf life of fresh beef

The need for bioactive-incorporated biodegradable packaging products is growing due to the desire to achieve food goods that have a longer shelf life and enhanced safety. The current study set out to create an edible coating using Malva neglecta seed polysaccharide mucilage (MNSM) containing Lactobacillus brevis TD4-derived postbiotics (PLB), and assess how well the PLB-MNSM edible coating preserved beef slices over a 12-day period of refrigeration. PLB was rich in fatty acids, organic heteropolycyclic compounds, monoterpene and cyclohexanol derivative, prenol lipids, ester compounds, and alpha-CH2-containing aldehyde with significant antimicrobial and antioxidant activities. By adding it to the edible coating at 0, 5, 10, and 15 % v/v, it successfully prevented the proliferation of microbial agents (total viable count, psychrotrophic count, Staphylococcus aureus, Escherichia coli, total coliform bacteria count, and fungi) as well as the oxidation of lipids (thiobarbituric and peroxide values) in beef samples. The samples' pH value, hardness, and moisture content were all more successfully sustained when PLB preparation was applied to the coating solution (P < 0.05). The edible coating consisting of PLB effectively maintained the meat color (L*, a*, b*) and sensory properties. Additionally, the bioactive edible coating comprised of MNSM and PLB, specifically MNSM-15 % PLB, significantly prevented the quality deterioration of beef samples and prolonged the shelf-life of the meat to over 12 days. The outcomes indicated that the MNSM-PLB edible coating has the capacity to be utilized as an antibacterial and antioxidant-rich packing material, hence enhancing the shelf life of meat-based goods.

Physicochemical properties of active films of rose essential oil produced using soy protein isolate-polyphenol conjugates for cherry tomato preservation

Soy protein isolate (SPI)-polyphenol conjugates were produced by grafting SPI individually with curcumin, naringenin, and catechin. The resulting conjugates showed better emulsifying properties and were used to develop active films containing rose essential oil. The effect of conjugation on the physicochemical and mechanical properties of these emulsion-based films was evaluated. The results showed that the barrier and mechanical properties of the films were improved when the SPI-polyphenol conjugates were used to emulsify the essential oil; in particular, the SPI-curcumin conjugate showed significant improvement. The improvements on the water vapor and oxygen barrier properties in the films were attributed to the formation of compact structure. Emulsion-based films stabilized by SPI-polyphenol conjugates showed antioxidant and antibacterial activities. They also demonstrated an ability to extend the shelf life of cherry tomatoes, as indicated by better preservation of weight, firmness, and ascorbic acid content.

Tuning the structure and physiochemical properties of sodium alginate and chitosan composite films through sodium tripolyphosphate (STPP) crosslinking

Sodium tripolyphosphate (STPP), an inorganic and non-toxic polyphosphate, has potential applications as a crosslinking agent in the fabrication of edible films. This study utilized STPP in the development of sodium alginate-chitosan composite films, with a focus on their suitability for food packaging applications. The results indicate that the incorporation of STPP led to an increase in film thickness (from 0.048 ± 0.004 to 0.078 ± 0.008 mm), elongation at break (from 11.50 ± 1.49 % to 15.88 ± 2.14 %), water permeation (from 0.364 ± 0.010 to 0.521 ± 0.021 gmm/(m2h*kPa)), and moisture content (from 25.98 ± 0.20 % to 28.12 ± 0.17 %). In contrast, there was a decrease in tensile strength (from 30.23 ± 2.08 to 25.60 ± 1.22 MPa) and swelling index (from 752.9 ± 17.1 to 533.5 ± 8.9 %). Scanning electron microscopy (SEM) analysis revealed the formation of distinctive needle-like microcrystals with the incorporation of STPP. Fourier-transform infrared spectroscopy (FTIR) analysis indicated intermolecular interactions between STPP and the film-forming biopolymers. The data obtained from Thermogravimetric analysis (TGA) and Differential Scanning Calorimetry (DSC) demonstrated enhanced thermal stability of STPP-loaded films at elevated temperatures. Furthermore, the films exhibited increased DPPH scavenging activity with the addition of STPP. This study underscores the potential of STPP as a crosslinking agent for the development of composite edible films, suggesting applications in the field of food packaging.

Casein-based conjugates and graft copolymers. Synthesis, properties, and applications

Biobased natural polymers, including polymers of natural origin such as casein, are growing rapidly in the light of the environmental pollution caused by many mass-produced commercial synthetic polymers. Although casein has interesting intrinsic properties, especially for the food industry, numerous chemical reactions have been carried out to broaden the range of its properties, most of them preserving casein's nontoxicity and biodegradability. New conjugates and graft copolymers have been developed especially by Maillard reaction of the amine functions of the casein backbone with the aldehyde functions of sugars, polysaccharides, or other molecules. Carried out with dialdehydes, these reactions lead to the cross-linking of casein giving three-dimensional polymers. Acylation and polymerization of various monomers initiated by amine functions are also described. Other reactions, far less numerous, involve alcohol and carboxylic acid functions in casein. This review provides an overview of casein-based conjugates and graft copolymers, their properties, and potential applications.

Novel applications of black pepper essential oil as an antioxidant agent in sodium caseinate and chitosan based active edible films

In the current study, sodium caseinate and chitosan-based composite edible films were developed with the incorporation of black pepper (Piper nigrum) essential oil (BPO) in various concentrations (0.05, 0.1 and 0.15 %) for potential food packaging applications. The chemical composition of BPO was determined using GCMS and the major compound detected were β-caryophyllene, limonene, β-phellandren, pinene, copaene and α-humulene. The addition of BPO resulted in an increase in the thickness, EAB, WVP, moisture content and swelling index values of the films; however, the TS and water solubility decreased. The inclusion of BPO led to a substantial enhancement in the DPPH and ABTS radical scavenging capabilities of the edible films. SEM micrographs demonstrated intermolecular interaction between BPO, sodium caseinate, and chitosan. FTIR spectra confirmed the interaction of the functional groups of the polymers and BPO. The incorporation of the BPO increased the crystallinity of the films. Moreover, the thermal analysis including TGA, DSC and DTG demonstrated an increase in the thermal stability of the edible films with the addition of the BPO. These findings demonstrated that sodium caseinate and chitosan composite based edible films loaded with BPO can be used as sustainable active food packaging material.

Development of composite film based on collagen and phenolic acid-grafted chitosan for food packaging

Collagen, a fibrous protein with triple-helical structure, is a good film-forming substrate for food packaging films because collagen films show advantages of biodegradability, high mechanical strength and good water resistance. However, collagen films lack functional activities, which may limit their applications in the field of active packaging. In this work, phenolic acid-grafted-chitosan was blended with collagen to improve the antioxidant and antimicrobial activities of collagen films. Gallic acid (GA), ferulic acid (FA) and caffeic acid (CA) were respectively grafted onto chitosan, and the physical properties and functional activities of the collagen/phenolic acids-g-chitosan (CGC, CFC and CCC) films were compared. The prepared films presented varying degrees of yellow color, and exhibited significantly improved UV light blocking capacity, antioxidant and antimicrobial properties due to the function of phenolic acid. Moreover, compared with collagen/chitosan (CC) film, CGC, CFC and CCC films showed higher mechanical strength (69.08-73.79 MPa), higher thermal denaturation temperature (69.4-71.2 °C), and lower water vapor permeability values (2.64-2.98 × 10^-12 g m^-1 s^-1 Pa^-1). The properties of collagen/ phenolic acids-g-chitosan films were greatly affected by the type of phenolic acid grafted. CGC film had the best antioxidant property as well as the best mechanical property, thermostability, UV light and water vapor blocking capacity.

Preparation and Characterization of Sodium Caseinate-Coated Papers Based on Glycerol and Sorbitol Contents for Packaging Application

Bio-based packaging materials are promising alternatives to petroleum-based plastics. Paper-based packaging materials are candidates for improving food sustainability; however, paper has poor gas and water vapor barrier properties. In this study, entirely bio-based sodium caseinate (CasNa)-coated papers with two plasticizers, glycerol (GY) and sorbitol (SO), were prepared. The morphological and chemical structure, burst strength, tensile strength, elongation at break, air permeability, surface properties, and thermal stability of the pristine CasNa-, CasNa/GY-, and CasNa/SO-coated papers were evaluated. The use of GY and SO strongly affected the tensile strength, elongation at break, and air barrier of the CasNa/GY- and CasNa/SO-coated paper. The air barrier and flexibility of the CasNa/GY-coated papers were higher than those of the CasNa/SO-coated papers. Compared to SO, GY better coated and penetrated the CasNa matrix, which positively affected the chemical and morphological structure of the coating layer and the interaction between the coating layer and paper. Overall, CasNa/GY was superior to the CasNa/SO coating. CasNa/GY-coated papers may be a good alternative for packaging materials in the food, medical, and electronic sectors, which would promote sustainability.

Effects of the geometry of reinforcement on physical properties of sodium caseinate/TiO2 nanocomposite films for applications in food packaging

Plastic materials for food packaging are being replaced by biodegradable films based on biopolymers due to the adverse effects they have had on animal life and the environment. In this study, nanocomposite films containing 2.5 wt% sodium caseinate and 2 wt% glycerol were reinforced with 0.1 or 0.2 wt% nano TiO₂ prepared in two forms: spheres (P25) and tubes. The effects of nanoreinforcement geometry on mechanical, tensile, barrier, thermogravimetric, and optical properties, and distribution of nanoparticles were described. The interactions among film components were analyzed by Fourier transform infrared spectroscopy (FTIR). Addition of nanotubes significantly increased E' (341 wt%) and E" (395 wt%) moduli, the Young modulus E (660 wt%), the residual mass at 500°C (38 wt%), and color change (6.78) compared to control film. The compositional mapping studies showed that P25 nanoparticles were homogeneously distributed between the surfaces of the film while nanotubes were found on the bottom surface. The changes in position of the FTIR spectra signals as compared to pure protein signals indicated strong matrix/reinforcement interactions. In addition, the changes in intensity in 1100, 1033, and 1638 cm^-1 FTIR signals suggested formation of a protein/Tween 20 ester. The geometry of reinforcement was highly relevant regarding physical properties, showing nanotubes as being very successful for enhancing tensile properties.

Characterization of Biodegradable Films Made from Taro Peel (Colocasia esculenta) Starch

Studies of renewable polymers have highlighted starch’s role to replace petroleum-based components to produce biodegradable films with plastic-like qualities. In this study, the novelty of taro peel starch (TPS) to produce such films using the casting technique is reported for the first time. A response surface method (RSM) approach was employed to optimize different concentrations of TPS (2.5−3.5%, w/w) and glycerol (25−35%, w/w) and investigate their effects on the physico-mechanical and water barrier properties of TPS films. TPS films showed a positive linear effect (p < 0.05) for thickness (0.058−0.088 mm), opacity (1.95−2.67), water vapor permeability (0.06−0.09 g∙m/m2∙kPa∙h), and cubic effect (p < 0.05) for moisture content (0.58−1.57%), which were linked to high starch concentrations when plasticized with glycerol. X-ray diffraction analysis of TPS films depicted “amorphous”-type crystalline structure peaks at 19.88°, while the thermogravimetric analysis of the film samples exhibited 75−80% of the weight loss of TPS film in the second phase between temperatures of 300 °C to 400 °C. All films exhibited homogenous, transparent surfaces with flexibility, and completely degraded in 5 days in simulated river water and composting soil environments, which confirmed TPS as a promising film polymer in food packaging.

Insights on Chemical Crosslinking Strategies for Proteins

Crosslinking of proteins has gained immense significance in the fabrication of biomaterials for various health care applications. Various novel chemical-based strategies are being continuously developed for intra-/inter-molecular crosslinking of proteins to create a network/matrix with desired mechanical/functional properties without imparting toxicity to the host system. Many materials that are used in biomedical and food packaging industries are prepared by chemical means of crosslinking the proteins, besides the physical or enzymatic means of crosslinking. Such chemical methods utilize the chemical compounds or crosslinkers available from natural sources or synthetically generated with the ability to form covalent/non-covalent bonds with proteins. Such linkages are possible with chemicals like carbodiimides/epoxides, while photo-induced novel chemical crosslinkers are also available. In this review, we have discussed different protein crosslinking strategies under chemical methods, along with the corresponding crosslinking reactions/conditions, material properties and significant applications.

Chitosan-Sodium Caseinate Composite Edible Film Incorporated with Probiotic Limosilactobacillus fermentum: Physical Properties, Viability, and Antibacterial Properties

Single-use synthetic plastics that are used as food packaging is one of the major contributors to environmental pollution. Hence, this study aimed to develop a biodegradable edible film incorporated with Limosilactobacillus fermentum. Investigation of the physical and mechanical properties of chitosan (CS), sodium caseinate (NaCas), and chitosan/sodium caseinate (CS/NaCas) composite films allowed us to determine that CS/NaCas composite films displayed higher opacity (7.40 A/mm), lower water solubility (27.6%), and higher Young's modulus (0.27 MPa) compared with pure CS and NaCas films. Therefore, Lb. fermentum bacteria were only incorporated in CS/NaCas composite films. Comparison of the physical and mechanical properties of CS/NaCas composite films incorporated with bacteria with those of control CS/NaCas composite films allowed us to observe that they were not affected by the addition of probiotics, except for the flexibility of films, which was improved. The Lb. fermentum incorporated composite films had a 0.11 mm thickness, 17.9% moisture content, 30.8% water solubility, 8.69 A/mm opacity, 25 MPa tensile strength, and 88.80% elongation at break. The viability of Lb. fermentum after drying the films and the antibacterial properties of films against Escherichia coli O157:H7 and Staphylococcus aureus ATCC 29213 were also evaluated after the addition of Lb. fermentum in the composite films. Dried Lb. fermentum composite films with 6.65 log₁₀ CFU/g showed an inhibitory effect against E. coli and S. aureus (0.67 mm and 0.80 mm inhibition zone diameters, respectively). This shows that the Lb.-fermentum-incorporated CS/NaCas composite film is a potential bioactive packaging material for perishable food product preservation.

Mung bean protein films incorporated with cumin essential oil: development and characterization

Biodegradable films based on mung bean protein (1, 3 and 5%) incorporated with cumin essential oil (EO) (0, 0.25 and 0.5 ml/g protein) were developed. Adding cumin oil and increasing the protein content enhanced the thickness, tensile strength and yellowness. Films incorporated with EO exhibited less water vapor permeability and water solubility, as compared to the control films. A higher antioxidant activity was also obtained by increasing the EO and protein ratios. Films with higher levels of protein displayed lower thermal stability with a lower degradation temperature, as suggested by thermo-gravimetric analyses. In addition, the incorporation of EO reduced thermal stability, as confirmed by the higher weight loss and lower degradation temperature. Furthermore, mung bean protein films containing 0.5 ml cumin oil/g protein had suitable physical characteristics, antioxidant activities, water barrier properties and thermal stability; thus, they can be used as appropriate biodegradable packaging materials for food preservation.

Physicochemical properties of films produced using nanoemulsions stabilized by carboxymethyl chitosan-peptide conjugates and application in blueberry preservation

Carboxymethyl chitosan (CMCh)-peptide conjugates were produced by grafting CMCh with peptides from hemp seed, maize and casein. The nanoemulsions stabilized by these conjugates had smaller droplet size and better emulsifying properties. Nanoemulsions stabilized by conjugates were used to develop active films containing Camellia essential oil and the effect of conjugation on physicochemical properties of resulting films was evaluated. Water vapor and oxygen barrier properties, tensile strength, flexibility, and temperature of endothermic peak increased 6.6-19.8% and 6.9-27.2%, 40.1-96.6%, 61.4-83.3% and 7.8-18.5%, respectively when the CMCh-peptide conjugates were used to emulsify the essential oil. The conjugation helped to form compact structure. All of the films containing essential oil emulsions stabilized by conjugates showed the ability to extend the shelf-life of blueberry by maintaining the firmness, reducing the weight loss and slowing down the formation of soluble solids.

Preparation and properties of poly (vinyl alcohol)/sodium caseinate blend films crosslinked with glutaraldehyde and glyoxal

Bio-based films containing poly (vinyl alcohol)/casein have poor mechanical and water vapor barrier properties that limit their use in packaging application. Some properties such as water resistance and tensile strength can be increased by the cross-linking process. For this reason, poly(vinyl alcohol)/sodium caseinate (PVA/SC) blends were crosslinked by adding glutaraldehyde (GLA) and glyoxal (GL) at different ratios in this work. The films were prepared by solution casting technique. Fourier transform infrared analysis (FTIR) confirmed the crosslinking reaction between the components. As a result of the crosslinking, the thicknesses, water vapor barrier properties and water contact angle values of the films have increased. The total soluble matters (TSM) of PVA/SC film decreased with increasing amounts of crosslinkers and GLA crosslinked films exhibited lower TSM. The addition of GLA and GL resulted in more strengthened films as verified by the tensile test. On the other hand, GLA crosslinked films were more flexible than un-crosslinked and GL crosslinked PVA/SC films. The hydrophilic PVA/SC film became more hydrophobic with the increasing amounts of crosslinkers. With the crosslinking, the PVA/SC film became more thermally stable. In conclusion, the crosslinked PVA/SC films were obtained with suitable properties for packaging applications.

Approaches in Animal Proteins and Natural Polysaccharides Application for Food Packaging: Edible Film Production and Quality Estimation

Natural biopolymers are an interesting resource for edible films production, as they are environmentally friendly packaging materials. The possibilities of the application of main animal proteins and natural polysaccharides are considered in the review, including the sources, structure, and limitations of usage. The main ways for overcoming the limitations caused by the physico-chemical properties of biopolymers are also discussed, including composites approaches, plasticizers, and the addition of crosslinking agents. Approaches for the production of biopolymer-based films and coatings are classified according to wet and dried processes and considered depending on biopolymer types. The methods for mechanical, physico-chemical, hydration, and uniformity estimation of edible films are reviewed.

Development of Chitosan/Peptide Films: Physical, Antibacterial and Antioxidant Properties

Chitosan/peptide films were prepared by incorporating peptides (0.4%, w/v) from soy, corn and caseins into chitosan films. The presence of peptides significantly affected the physical, antibacterial and antioxidative properties of chitosan films. Among these films, those containing corn peptide showed the best water vapor barrier properties, and the tensile strength and elongation at break increased to 24.80 Mpa and 23.94%, respectively. Characterization of surface hydrophobicity and thermal stability suggested the strongest intermolecular interactions between corn peptides and chitosan. Moreover, films containing casein peptides showed the highest antibacterial activity and radical scavenging activity. The DPPH scavenging rate of films containing casein peptides reached 46.11%, and ABTS scavenging rate reached 66.79%. These results indicate the chitosan/peptide films may be promising food packaging materials.

Encapsulation of Grapefruit Essential Oil in Emulsion-Based Edible Film Prepared by Plum (Pruni Domesticae Semen) Seed Protein Isolate and Gum Acacia Conjugates

A dry-heated Maillard reaction was used to prepare plum seed protein isolate and gum acacia conjugates. Emulsion-based edible films (EBEF) were prepared by the encapsulation of grapefruit essential oil using conjugates solution as the continuous phase. The conjugates formed from 3 days of dry heating showed a significant improvement in emulsifying properties due to the unfolding of protein, as confirmed by structure analysis. The droplet size, electrical charge, and viscosity of emulsions increased with the increasing essential oil concentration, and all emulsions exhibited ‘gel’-like behavior. The water vapor barrier property, surface hydrophobicity, mechanical properties, and thermal stability of the films were improved as the essential oil content increased in the range of 1–4% due to enhancement in intermolecular interaction and compatibility, as well as a denser microstructure. Furthermore, all films exhibited an inhibitory effect against E. coli, while their radical scavenging activity depended on the release rate from films. The results obtained in this work confirmed that EBEF could be used as a novel food active packaging in the near future.