Lysozyme-based composite membranes and their potential application for active packaging

Antibacterial activity of lysozyme after association with carboxymethyl konjac glucomannan

The unique high isoelectric point of lysozyme (LYZ) restricts its application in composite antibacterial coating due to the unfavorable liability to electrostatic interaction with other components. In this work, the antibacterial activity of a dispersible LYZ-carboxymethyl konjac glucomannan (CMKGM) polyelectrolyte complex was evaluated. Kinetic analysis revealed that, compared with free LYZ, the complexed enzyme exhibited decreased affinity (Km) but markedly increased Vmax against Micrococcus lysodeikticus, and QCM and dynamic light scattering analysis confirmed that the complex could bind with the substrate but in a much lower ratio. The complexation with CMKGM did not alter the antibacterial spectrum of LYZ, and the complex exerted antibacterial function by delaying the logarithmic growth phase and impairing the cell integrity of Staphylococcus aureus. Since the LYZ-CMKGM complex is dispersible in water and could be assembled easily, it has great potential as an edible coating in food preservation.

The Effect of Fibrillation, Semi-Dry Pressing, and Surface Treatment on the Barrier Properties of Water Molecules and Oxygen on Food Packaging Paper

The characteristics of fiber morphology and paper structure are critical to the barrier properties of food packaging paper. Herein, this study aimed to use pulp fibrillation, paper semi-dry pressing and carboxymethyl starch (CMS) coating to flatten the fibers, which were formed on the paper surface with good barrier properties due to the tight bond between fibers. The results showed that the permeability of paper was reduced by 87.56%, from 81.44 μm/Pa·s to 10.13 μm/Pa·s after the pulp fibrillation treatment (60 °SR). Moreover, semi-dry pressing treatment contributed to decreasing the water vapor transmission coefficient (WVP) by 50.98% to 2.74 × 10-10 g/m·s·Pa, and the oxygen permeation coefficient (OP) decreased by 98.04% to 1.93 × 10-14 cm3·cm/cm2·s·Pa. After coating the paper surface with titanium dioxide (TiO2) and CMS, the WVP of the paper was further reduced to 1.55 × 10-10 g/m·s·Pa, and OP was reduced to 0.19 × 10-14 cm3·cm/cm2·s·Pa. These values were 72.27% and 99.8% lower than those of the original paper, respectively. Therefore, through pulp fibrillation, semi-dry pressing of paper, TiO2 filling, and surface coating with CMS, there is no need to use synthetic polymer surface film-forming agents to achieve the high barrier properties that are required for low water and oxygen molecules permeation in food packaging paper.

A review on bio-based polymer polylactic acid potential on sustainable food packaging

Poly(lactic acid) (PLA) stands as a compelling alternative to conventional plastic-based packaging, signifying a notable shift toward sustainable material utilization. This comprehensive analysis illuminates the manifold applications of PLA composites within the realm of the food industry, emphasizing its pivotal role in food packaging and preservation. Noteworthy attributes of PLA composites with phenolic active compounds (phenolic acid and aldehyde, terpenes, carotenoid, and so on) include robust antimicrobial and antioxidant properties, significantly enhancing its capability to bolster adherence to stringent food safety standards. The incorporation of microbial and synthetic biopolymers, polysaccharides, oligosaccharides, oils, proteins and peptides to PLA in packaging solutions arises from its inherent non-toxicity and outstanding mechanical as well as thermal resilience. Functioning as a proficient film producer, PLA constructs an ideal preservation environment by merging optical and permeability traits. Esteemed as a pioneer in environmentally mindful packaging, PLA diminishes ecological footprints owing to its innate biodegradability. Primarily, the adoption of PLA extends the shelf life of products and encourages an eco-centric approach, marking a significant stride toward the food industry's embrace of sustainable packaging methodologies.

Graphical abstract

Characteristics of hen egg white lysozyme, strategies to break through antibacterial limitation, and its application in food preservation: A review

Hen egg white lysozyme (HEWL) is used as a food additive in China due to its outstanding antibacterial properties. It is listed as GRAS grade (generally recognized as safe) by the United States Food and Drug Administration (FDA, US) and has been extensively researched and used in food preservation. And the industrial production of HEWL already been realized. Given the complex food system that can affect the antibacterial activity of HEWL, and the limitations of HEWL itself on Gram-negative bacteria. Based on the structure and main biological characteristics of HEWL, this paper focuses on reviewing methods to enhance the stability and antibacterial properties of HEWL. Immobilization tactics such as chemically driven self-assembly, embedding and adsorption address the restriction of poor HEWL antibacterial activity effected by external factors. Both intermolecular and intramolecular modification strategies break the bactericidal deficiencies of HEWL itself. It also comprehensively analyzes the current application status and future prospects of HEWL in the food preservation. There was limited research on the biological methods in modifying HEWL. If the HEWL is genetically engineered, it can broaden its antimicrobial spectrum, improve its other biological activities, so as to further expand its application in the food industry. At present, research on HEWL mainly focused on its antibacterial properties, whereas its application in anti-inflammatory and antioxidant effects also presented great potential.

Epitope Mapping of Lysozyme Using the Chinese Egg-Allergic Sera at Both Pooled and Individual Levels

To accurately map the B-cell linear epitopes of lysozyme (LYS) in eggs, five bioinformatics tools were first used to obtain the mimotopes. Afterward, based on the Chinese egg-allergic sera samples screened by the indirect enzyme-linked immunosorbent, the epitopes possessing the capability of binding to IgG/IgE were mapped at both pooled and individual levels by using overlapping peptides covering the complete amino acid sequence of LYS. Six B-cell linear epitopes and two dominant B-cell linear epitopes that could bind to LYS-sIgG were mapped for the first time. Seven IgE-binding epitopes and three dominant IgE-binding epitopes were also obtained. Furthermore, AA31-34 and AA88-91 were the shared dominant epitopes of LYS-sIgG and LYS-sIgE at pooled and individual levels. Overall, the mapped B-cell linear epitopes filled in the gaps in the study of LYS epitopes, and the results may provide theoretical support for the following immunotherapy of egg allergy.

A Review on Antimicrobial Packaging for Extending the Shelf Life of Food

Food packaging systems are continually impacted by the growing demand for minimally processed foods, changing eating habits, and food safety risks. Minimally processed foods are prone to the growth of harmful microbes, compromising quality and safety. As a result, the need for improved food shelf life and protection against foodborne diseases alongside consumer preference for minimally processed foods with no or lesser synthetic additives foster the development of innovative technologies such as antimicrobial packaging. It is a form of active packaging that can release antimicrobial substances to suppress the activities of specific microorganisms, thereby improving food quality and safety during long-term storage. However, antimicrobial packaging continues to be a very challenging technology. This study highlights antimicrobial packaging concepts, providing different antimicrobial substances used in food packaging. We review various types of antimicrobial systems. Emphasis is given to the effectiveness of antimicrobial packaging in various food applications, including fresh and minimally processed fruit and vegetables and meat and dairy products. For the development of antimicrobial packaging, several approaches have been used, including the use of antimicrobial sachets inside packaging, packaging films, and coatings incorporating active antimicrobial agents. Due to their antimicrobial activity and capacity to extend food shelf life, regulate or inhibit the growth of microorganisms and ultimately reduce the potential risk of health hazards, natural antimicrobial agents are gaining significant importance and attention in developing antimicrobial packaging systems. Selecting the best antimicrobial packaging system for a particular product depends on its nature, desired shelf life, storage requirements, and legal considerations. The current review is expected to contribute to research on the potential of antimicrobial packaging to extend the shelf life of food and also serves as a good reference for food innovation information.

Advancements in Biodegradable Active Films for Food Packaging: Effects of Nano/Microcapsule Incorporation

Food packaging plays a fundamental role in the modern food industry as a main process to preserve the quality of food products from manufacture to consumption. New food packaging technologies are being developed that are formulated with natural compounds by substituting synthetic/chemical antimicrobial and antioxidant agents to fulfill consumers’ expectations for healthy food. The strategy of incorporating natural antimicrobial compounds into food packaging structures is a recent and promising technology to reach this goal. Concepts such as “biodegradable packaging”, “active packaging”, and “bioactive packaging” currently guide the research and development of food packaging. However, the use of natural compounds faces some challenges, including weak stability and sensitivity to processing and storage conditions. The nano/microencapsulation of these bioactive compounds enhances their stability and controls their release. In addition, biodegradable packaging materials are gaining great attention in the face of ever-growing environmental concerns about plastic pollution. They are a sustainable, environmentally friendly, and cost-effective alternative to conventional plastic packaging materials. Ultimately, a combined formulation of nano/microencapsulated antimicrobial and antioxidant natural molecules, incorporated into a biodegradable food packaging system, offers many benefits by preventing food spoilage, extending the shelf life of food, reducing plastic and food waste, and preserving the freshness and quality of food. The main objective of this review is to illustrate the latest advances in the principal biodegradable materials used in the development of active antimicrobial and antioxidant packaging systems, as well as the most common nano/microencapsulated active natural agents incorporated into these food-packaging materials.

Bioactive Electrospun Fibers of Poly(ε-Caprolactone) Incorporating α-Tocopherol for Food Packaging Applications

Antioxidant activity is an important feature for food contact materials such as packaging, aiming to preserve freshness and retard food spoilage. Common bioactive agents are highly susceptible to various forms of degradation; therefore, protection is required to maintain functionality and bioavailability. Poly(ε-caprolactone) (PCL), a biodegradable GRAS labeled polymer, was used in this study for encapsulation of α-tocopherol antioxidant, a major component of vitamin E, in the form of electrospun fibers. Rheological properties of the fiber forming solutions, which determine the electrospinning behavior, were correlated with the properties of electrospun fibers, e.g., morphology and surface properties. Interactions through hydrogen bonds were evidenced between the two components. These have strong effect on structuration of macromolecular chains, especially at low α-tocopherol amounts, decreasing viscosity and elastic modulus. Intra-molecular interactions in PCL strengthen at high α-tocopherol amounts due to decreased solvation, allowing good structural recovery after cease of mechanical stress. Morphologically homogeneous electrospun fibers were obtained, with ~6 μm average diameter. The obtained fibers were highly hydrophobic, with fast release in 95% ethanol as alternative simulant for fatty foods. This induced good in vitro antioxidant activity and significant in vivo reduction of microbial growth on cheese, as determined by respirometry. Therefore, the electrospun fibers from PCL entrapping α-tocopherol as bioactive agent showed potential use in food packaging materials.