Impact of cross-linking mode on the physical properties of zein/PVA composite films

Production of polysaccharide and protein edible films: Challenges and strategies to scale-up

Polymeric films are among the main packaging materials used by food industry, and they can be produced using petrochemical-based polymers and biopolymers. Although the use of petrochemical-based polymers for food packaging is associated with a harmful impact on the environment, and human health through direct contact with food, the food industry cannot avoid their use due to the lack of fully viable alternatives. Therefore, there is an imperative need for potential food packaging alternatives made from natural, bio-based polymers that should be safe and biodegradable. In this group, edible polysaccharides and proteins present several advantages, making them green and safe alternatives. Therefore, several pilot and semi-commercial attempts have been made to commercialize the production of edible packaging materials. However, their industrial-scale production still presents big challenges. These challenges are related to the properties of edible biopolymers, such as low elasticity and high hygroscopicity, and, others are associated with the commercial-scale manufacturing technologies, which causes a slower implementation of edible films at the industrial level. This study aims to discuss edible films' main properties and limitations and propose possibilities for their industrial-scale production, focusing on maintaining their natural and ecofriendly food packaging with evolved functionalities.

Tailoring hydrophobicity and strength in spider silk-inspired coatings via thermal treatments

The advent of advanced coatings has transformed material functionalities, extending their roles from basic coverage and visual appeal to include unique properties such as self-healing, superior hydrophobicity, and antimicrobial action. However, the traditional dependency on petrochemical-derived materials for these coatings raises environmental concerns. This study proposes the use of renewable and alternative materials for coating development. We present the use of bioengineered spider silk-inspired protein (SSIP), produced through recombinant technology, as a viable, eco-friendly alternative due to their ease of processing under ambient pressure and the utilization of water as a solvent, alongside their exceptional physicochemical properties. Our research investigates the effects of different thermal treatments and protein concentrations on the mechanical strength and surface water repellency of coatings on silica bases. Our findings reveal a direct correlation between the temperature of heat treatment and the enhancements in surface hydrophobicity and mechanical strength, where elevated temperatures facilitate increased resistance to water and improved mechanical integrity. Consequently, we advocate SSIPs present a promising, sustainable choice for advanced coatings, providing a pathway to fine-tune coating recipes for better mechanical and hydrophobic properties with a reduced ecological footprint, finding potential uses in various fields such as electronics.

Fabrication of Electrospun PVA/Zein/Gelatin Based Active Packaging for Quality Maintenance of Different Food Items

In this research, electrospun PVA/Zein/Gelatin based tri-component active food packaging has been fabricated to enhance the shelf life of food by assuring the food quality (freshness, taste, brittleness, color, etc.) for longer. Electrospinning imparts good morphological properties along with breathability in nanofibrous mats. Electrospun active food packaging has been characterized to investigate the morphological, thermal, mechanical, chemical, antibacterial and antioxidant properties. Results of all tests indicated that the PVA/Zein/Gelatin nanofiber sheet possessed good morphology, thermal stability, mechanical strength, good antibacterial properties along with excellent antioxidant properties, which makes it the most suitable food packaging for increasing the shelf life of different food items like sweet potatoes, potatoes and kimchi. Shelf life of sweet potatoes and potatoes was observed for a period of 50 days, and shelf life of the kimchi was observed for a period of 30 days. It was concluded that nanofibrous food packaging may enhance the shelf life of fruit and vegetables because of their better breathability and antioxidant properties.

Cross-linked CMC/Gelatin bio-nanocomposite films with organoclay, red cabbage anthocyanins and pistacia leaves extract as active intelligent food packaging: colorimetric pH indication, antimicrobial/antioxidant properties, and shrimp spoilage tests

Multifunctional food packaging films were produced from crosslinked carboxymethyl cellulose/gelatin (CMC/Ge) bio-nanocomposites incorporated with Ge-montmorillonite (OM) nanofiller, anthocyanins (ATH) from red cabbage as colorimetric pH-indicator, and pistacia leaves extract (PE) as active agent. The influence of additives on the structural, physical, and functional properties of the films was investigated. The results showed that ATH and PE caused color alteration and reduced transparency. However, they improved the UV light barrier ability by 98 %, with less impact from OM, despite its well-dispersed state in the matrix. Increasing PE content in the bio-nanocomposite films caused an increase in compactness and surface roughness, reduction in moisture content (15.10-12.33 %), swelling index (354.55-264.58 %), surface wettability (contact angle 80.1-92.49°), water vapor permeability (7.37-5.69 × 10¹⁰ g m^-1s^-1Pa^-1), and nano-indentation mechanical parameters, without affecting the thermal stability. ATH-included films demonstrated color pH-sensitivity with improved ATH color stability through the ATH-Al³⁺ chelates formation. PE-added films exhibited effective antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical, reaching 93 % of inhibition, and antimicrobial properties with biocidal effects for PE-rich film. The shrimp spoilage test showed that the T-1.5PE film offered the strongest active intelligent response. The CMC/Ge-based bio-nanocomposite films endowed with antioxidant/antimicrobial properties and colorimetric pH-sensitivity have promising potential for food packaging application.

Effects of citric acid crosslinking on the structure and properties of ovotransferrin and chitosan composite films

In this study, ovotransferrin/chitosan (OVT/CS) composite films cross-linked by citric acid (CA) were prepared and the effects of CA cross-linking on the structure and physicochemical properties of the composite films were investigated. The cross-linking degree measured by 2,4,6-trinitrobenzenesulfonic acid (TNBS) method confirmed that CA was cross-linked with the matrix, and Fourier transform infrared spectroscopy confirmed that more hydrogen bonds and electrostatic interactions were formed between CA and the matrix. Differential scanning calorimetry, X-ray diffraction and Scanning electron microscope images revealed the compatibility between substances. The synergistic inhibition between the matrix results in a significantly higher antibacterial activity of the composite film than the pure film. Compared with uncross-linked films, the mechanical properties, barrier properties and water resistance of the cross-linked films were significantly improved. When the concentration of CA was 5 wt% (W/W, on a dry basis of the weight of OVT and CS), the most significant improvement in film performance was obtained. The tensile strength of the film increased from 32.05 MPa without cross-linking to 61.99 MPa and the swelling degree decreased from 51.5 % to 24.23 %. The observed phenomena suggest that cross-linking OVT and CS with CA can obtain functional edible films with improved properties.

Biodegradable active packaging: Components, preparation, and applications in the preservation of postharvest perishable fruits and vegetables

The consumption of fresh fruits and vegetables is restricted by the susceptibility of fresh produce to deterioration caused by postharvest physiological and metabolic activities. Developing efficient preservation strategies is thus among the most important scientific issues to be urgently addressed in the field of food science. The incorporation of active agents into a polymer matrix to prepare biodegradable active packaging is being increasingly explored to mitigate the postharvest spoilage of fruits and vegetables during storage. This paper reviews the composition of biodegradable polymers and the methods used to prepare biodegradable active packaging. In addition, the interactions between bioactive ingredients and biodegradable polymers that can lead to plasticizing or cross-linking effects are summarized. Furthermore, the applications of biodegradable active (i.e., antibacterial, antioxidant, ethylene removing, barrier, and modified atmosphere) packaging in the preservation of fruits and vegetables are illustrated. These films may increase sensory acceptability, improve quality, and prolong the shelf life of postharvest products. Finally, the challenges and trends of biodegradable active packaging in the preservation of fruits and vegetables are discussed. This review aims to provide new ideas and insights for developing novel biodegradable active packaging materials and their practical application in the preservation of postharvest fruits and vegetables.

The realm of plant proteins with focus on their application in developing new bakery products

Plant proteins are spreading due to growing environmental, health and ethical concerns related to animal proteins. Proteins deriving from cereals, oilseeds, and pulses are witnessing a sharp growth showing a wide spectrum of applications from meat and fish analogues to infant formulations. Bakery products are one of the biggest markets of alternative protein applications for functional and nutritional motives. Fortifying bakery products with proteins can secure a better amino-acids profile and a higher protein intake. Conventional plant proteins (i.e., wheat and soy) dominate the bakery industry, but emerging sources (i.e., pea, chickpea, and faba) are also gaining traction. Each protein brings specific functional properties and nutritional value. Therefore, this chapter gives an overview of the main features of plant proteins and discusses their impact on the quality of bakery products.

Formation and characterization of protein-based films from yellow pea (Pisum sativum) protein isolate and concentrate for edible applications

This study investigated the properties of films or bioplastics fabricated using a wet processing method from yellow pea protein isolate (YPI) and protein concentrate (YPC) for potential application in food packaging. The wet processing method included mixing the protein with water and glycerol followed by casting and drying the films in a humidity- and temperature-controlled chamber. Whey protein isolate (WPI) and a film from a blend of equal amounts of YPI and WPI, labelled as YPI + WPI, were also studied. Fourier transform-infra red analysis revealed that films from YPI, YPC, WPI and YPI + WPI were formed by protein polymerisation with the plasticiser, glycerol, via hydrophobic and hydrophilic interactions. The protein films had contact angles of <90° demonstrating that they had a hydrophilic surface, with YPC < YPI < YPI + WPI < WPI. The pattern of ultraviolent light transmission of the films was WPI > YPC > YPI + WPI > YPI, whereas the mechanical and thermal resilience of films formulated from YPI, YPC and the protein blend were comparable to the properties of WPI-based films. The findings demonstrate that yellow pea proteins can be used as biomaterials to develop protein and protein-blend films or bioplastics for food packaging and edible applications.

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Bioplastics were fabricated from yellow pea protein isolate and concentrate, with glycerol.

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Contact angles of pea protein films indicate more hydrophobic surface than whey protein films.

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Pea protein films had more surface structure homogeneity and limited light transmission.

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Pea + whey protein blend did not produce synergistic effects in film property.

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Film physico-mechanical properties are promising for food packaging application.

Synthesis of Intelligent pH Indicative Films from Chitosan/Poly(vinyl alcohol)/Anthocyanin Extracted from Red Cabbage

In this study, pH indicative films were successfully synthesized from hydrogels made by blending 1% poly(vinyl alcohol) (PVA) and 1% chitosan (CS) with anthocyanin (ATH) and sodium tripolyphosphate (STPP). Particularly, ATH extracted from red cabbage was used as the pH indicator, while STPP was utilized as the cross-linking agent to provide better mechanical properties of the cast films. FT-IR spectra confirmed the existence of the ATH in the cast films. Moreover, the tensile strength, the elongation-at-break, and the swelling indices of the cast films were measured. In general, these properties of pH indicative films were profoundly influenced by the compositions of PVA/CS and the STPP dosage applied in the hydrogels. For example, the tensile strength could change from 43.27 MPa on a film cast from pure PVA hydrogel to 29.89 MPa, if 35% of the PVA hydrogel was substituted with CS. The cast films were applied as a food wrap that could be used to monitor visually the quality of the enwrapped food via the color change of the film upon the variation in pH values of the enwrapped food. In practice, a sequential change in color was successfully observed on the pH indicative films partially enwrapping the pork belly, indicating the spoilage of the meat.