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Polymeric nanofibers play an important role in modern food packaging because of their ability to modulate the pore size, surface reactivity, barrier properties, antimicrobial properties, optical properties and mechanical strength of packaging materials. There are a number of methods for producing nanofibers, of which electrostatic spinning is one of the most popular because of its relatively low cost and ease of scale-up. The electrostatic spinning process involves converting a polymer solution into a fiber matte using two electrodes (usually a syringe tip and a collector plate) with a high voltage electrostatic field between the two electrodes. The electric field pulls the polymer solution through the syringe tip, which creates a thin polymer jet. As the jet travels through the air, the solvent is evaporated, which leads to the formation of a layer of nanofibers on the collector plate, which can be rotating or fixed. The strength of the electric field must be high enough to overcome the surface tension of the polymer solution. A schematic representation of the process is shown in Figure 1. This method allows the production of robust nanofibers with diameters of 10-1000 nm, with great elasticity and high surface-to-volume ratios; however, the polymer, the type of solvent, and the operating conditions used must be carefully controlled. This method is popular in the food industry because it can be used to make nanofibers, such as proteins and polysaccharides, from food-grade polymers.
The main point of this paper
Recent advances in smart and active packaging materials:
Smart packaging materials are able to respond to specific changes in the properties of food materials, for example, by displaying a color change to warn when a food is contaminated with microorganisms
Active packaging materials, on the other hand, are designed to release functional agents (e.g., antioxidants or antimicrobials) to protect food during storage, improve food quality and extend shelf life
Advances in research on functionalized food packaging films based on natural polysaccharides have shown that by adding active agents such as plant essential oils and natural antioxidants, it is possible to extend the shelf life of food and ensure stable release of active agents
Progress in the application of nanomaterials in food storage has shown that new “smart” packaging materials can be intelligently controlled by adding nanomaterials, such as the slow release of preservatives from nano-microspheres, and nanoscale array sensors to monitor the basic safety of food.
Application of electrospun nanofiber materials in food packaging:
The main advantage of electrospun nanofibers as packaging materials lies in the method of encapsulating active agents within the fibers with relative ease to form a nonwoven fiber mat coating. The small diameter and high surface area of the fibers allow them to respond quickly to the surrounding conditions and release the active agent in a timely manner
The main advantages of the electrostatic spinning method for the fabrication of polymer nanofibers are simplicity, cheapness, versatility and scalability. However, there are problems such as solvent recovery, low productivity and jet instability that need to be addressed
Uniformly dispersed polymer nanofiber composites by electrostatic spinning, such as poly(vinyl alcohol) nanofiber/poly(dimethylsiloxane) composites, can improve the mechanical properties of the matrix polymer
Research by Prof. Lan Xu's team at Soochow University shows that the application of electrostatically spun nanofibers in functional food packaging, including antimicrobial packaging, antioxidant packaging, barrier packaging, and smart packaging, can maintain the quality and sensory properties of food products for the purpose of improving food safety and effectively delaying the shelf life of food products.
Biodegradable packaging materials formed from natural polymers:
There is a growing need to improve the functional properties of biodegradable packaging materials formed from natural polymers (proteins and polysaccharides) to match the desired properties of traditional petroleum-based plastic packaging materials
Nanofibers control the porosity or mechanical strength of packaging materials:
Nanofibers can also be used to control the porosity or mechanical strength of packaging materials, which is also beneficial for controlling the performance of food during storage
Advantages of electrospun nanofibers:
Electrospinning technology allows the preparation of nanofibers with high specific surface area, which is beneficial for encapsulating bioactive compounds and enhancing the functionality of food packaging materials.
Electrospinning technology operates under mild conditions, which is favorable to protect sensitive active compounds that are degraded during high temperature processing.
The ability of electrospinning to prepare nanofibers with a variety of structures, such as uniaxial, core-shell, and porous structures, provides additional possibilities for encapsulating bioactive compounds.
The use of natural biopolymers in electrospinning allows for the preparation of biodegradable and biocompatible films, which can help to improve the sustainability of food packaging systems.
Electrospun nanofibers with high porosity and loading capacity are suitable for efficient encapsulation of bioactive compounds with improved release efficiency.
Effect of electrospun nanofibers on physicochemical properties of packaging materials:
The addition of nanofibrils in appropriate amounts can significantly optimize the strength and barrier properties of packaging materials
The effect of electrospun nanofibers on the physicochemical properties of packaging materials.
A large number of hydroxyl groups on the surface of nanocellulose crystals generate interfacial adsorption with polymer molecules, which results in mechanical penetration effect and increases the connectivity between matrix molecules within the membrane, effectively increasing the strength of the material.
Application of nanofiber packaging materials in food:
The application of nanofiber materials in food packaging for dairy products, meat products, fruit and vegetable products, etc. has been widely studied
Nanocellulose crystals can be used as a filler added to polyvinyl alcohol, whey protein, chitosan, polylactic acid (PLA), and other polymer matrices to enhance the tensile strength, Young's modulus, and barrier properties of the materials.
Innovation of electrospun nanofibers as packaging materials:
Polymer nanofibers as additives to packaging materials are gaining attention due to their ability to control pore size, surface energy, barrier properties, antimicrobial activity, and mechanical strength
Electrospun nanofibers are covalently or non-covalently functionalized to load various bioactives such as antimicrobials, antioxidants, oxygen scavengers, carbon dioxide generators, ethylene scavengers
Chitosan based electrospun nanofiber materials:
Chitosan based electrospun nanofibers have attracted attention due to their high specific surface area, ease of fabrication and efficacy as active food packaging materials.
The different properties of these nanofiber materials such as water and gas barrier, mechanical properties, thermal stability and cytotoxicity assays are also satisfactory and the proposed materials have been successfully used as food packaging materials to extend the shelf life of a variety of food products.
Electrospinning technology is increasingly being used in the food industry to produce nanofibers due to its simplicity, flexibility, and cost-effectiveness. One of the most common applications of this technology is in the manufacture of smart and/or active packaging materials due to its right choice of ingredients, high surface-to-volume ratio, user-friendly manufacturing methods with high bioactive loading, rapid response, timely release of bioactivity, and control of the structural properties of packaging materials at the nanoscale, where nanofibers are used to make sensors or preservatives. This review summarizes the applications of electrospun fibers in smart and active packaging materials. Although active nanofibers have the potential to be used as packaging materials and are ideal carriers for antimicrobial and antioxidant agents, their application on an industrial scale is limited due to some properties such as poor mechanical and water resistance, especially for products with high moisture content such as meat and dairy products and products that come in contact with the product. In addition, another barrier that limits the use of nanofibers in the packaging industry is the use of chemical solvents required to dissolve the synthetic polymers. Therefore, to overcome these limitations, it is recommended that the nature of the nanofiber matrix/compound be food-grade and insoluble compounds with high water resistance, and that these nanofibers be used in conjunction with other packaging material synthesis methods, such as multilayer packaging and incorporation with packaging films. The nanofibrous materials were prepared using green solvents and a melt electrospinning system without the use of any chemical solvents. The porous structure of the nanofibers is another limitation of these materials, which results in more permeation of water vapor, oxygen, and gases than packaging films. Therefore, it is very important to use special biopolymers and compounds that can absorb these gases and moisture. In addition, it is important to develop economical and scalable production methods to create sufficient quantities of these functional materials for use in the food industry.
