Preliminary study on antibacterial packaging mater

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Preliminary study on antibacterial packaging materials for food

unlike goods such as electrical components and furniture, food is prone to decay. Type III samples of various components are only suitable for determining the tensile strength of molded chopped glass fiber reinforced plastics. There is a safety problem with food, which has a relatively short shelf life

the primary purpose of food packaging is to protect the contents. In the existing food packaging, there have been new materials that use various active substances to improve the function of packaging materials or give new functions. In addition to the function of extending the shelf life of packaged food, they also have the special function of maintaining food nutrition and safety

this technology with activated packaging makes use of many new functions formed by the interaction between food ingredients, packaging materials and internal gases of packaging materials, such as oxygen capture, antibacterial activity, water capture, ethylene gas capture and ethanol removal, which provide sufficient favorable conditions for the preservation of food and prolong the shelf life of packaged food

antibacterial food packaging injects antibacterial agents into polymers, making packaging materials have new functions of inhibiting microbial proliferation and killing and sterilizing. This antibacterial technology can not only be effectively applied to film packaging materials of food, but also be used in packaging containers, food equipment and other forms

the antibacterial activity of food packaging materials can be obtained by antibacterial agents, irradiation, gas emission and instant sterilization. Irradiation method uses radioactive materials, ultraviolet exposed materials, far-infrared ceramic powder and other materials. But so far, the method of using this kind of irradiation in food packaging materials has not been approved by FDA

the gas emission method can control the growth of mold. In the storage of strawberries and grapes, people can use the sulfur dioxide gas produced in the packaging bag to prevent mold. Although this method is very simple and feasible. However, at present, packaging materials containing bactericidal gases such as sulfur dioxide have not yet been marketed and are in the research stage

oxygen capture system refers to preventing food oxidation and inhibiting aerobic microorganisms, especially the growth of mold, by absorbing the residual oxygen in packaging materials. The use of deoxidizers in food packaging is the best example

antibacterial substances the main function and important characteristics of antibacterial packaging materials are to inject antibacterial preservatives into packaging materials and exert antibacterial activity by releasing a certain proportion of antibacterial components. Deoxidizers or oxygen absorbers reduce the concentration of residual oxygen in packaged products from the top gap or close to zero through a certain chemical reaction of mold oxygen or oxygen consuming enzymes (such as glucose oxidase), so as to prevent oxidative discoloration of food and spoilage caused by mold

general antibacterial chemicals suitable for food packaging include organic salts, sulfite, nitrite, antibiotics, ethanol, etc. For example, sorbic acid and its potassium salt are often used as preservatives in the packaging of cheese products. They can be used after the wax layer of natural cheese, the wax coating of packaging paper and the limited addition and mixing with edible protein. The disadvantage is that these materials can not control the release and transfer speed of antibacterial agents arbitrarily, so it is difficult to achieve perfect results

there are also other chemicals, gases, enzymes and natural ingredients. Nanjing Julong is also promising and is being tried as a new antibacterial reinforcement material, such as inorganic whisker reinforcement and carbon fiber reinforced Pa. it will become an important variety agent and bactericide. They are propionic acid, peroxide, O3, chlorine dioxide, eugenol (Eugenol), lauraldehyde, propyl isocyanate, lysozyme, nisin, etc. Considering the edible problem, natural ingredients are more suitable for antibacterial packaging systems than hydrogen peroxide, O3, chlorine dioxide, etc

in recent years, biodegradable polymer materials are generally used in edible coatings and film packaging materials together with various preservatives and natural antibacterial agents to make its antibacterial function better

antibacterial packaging system almost all food packaging systems are composed of packaging materials, food and top gap. Packaged food system refers to the low viscosity or liquid food with direct contact between food and packaging materials, or without top gap. Various waxed cheese, exquisite food and sterile brick packaging (Tetra Pak) are the most representative examples

in the composition system of packaging/top gap/food, there are different packaging forms, such as soft packaging, bottles, cans, cups and cartons. Compared with the non-volatile components that are only in contact with food and packaging materials, volatile components can be transferred greatly through the top gap and top cover between packaging materials and food. If the release speed and transfer movement of antibacterial substances released from food packaging materials can be controlled, it is very important for the antibacterial packaging system to realize its antibacterial function

the design of packaging system can affect the main factors of antibacterial film and packaging design as follows:

forming conditions and antibacterial activity. There are 89 antibacterial activities of residual active substances, which will deteriorate in the forming process of film or container, processing or storage, distribution and circulation. Antibacterial activity can almost completely lose its effectiveness due to deterioration in the extrusion process under high temperature, high shear and high pressure. Therefore, the temperature, pressure and material retention time in the extruder are important basis for predicting the residual amount of antibacterial activity

the influence of processing operations such as compounding, printing, drying and storage, and the influence of adhesives and solvents should also be analyzed quantitatively. In addition to chemical decomposition, volatile components are likely to be lost during forming and storage, resulting in reduced activity

antibacterial substances and food characteristic growth inhibition materials and reaction speed are important factors that need to be discussed first when designing antibacterial packaging systems. The mathematical model of microbial proliferation is composed of inhibition reaction speed and materials. Therefore, the design of the release rate of antibacterial agents must be based on the study of the proliferation rate of microorganisms and maintain its critical inhibitory concentration above as the benchmark

due to the different chemical and biological characteristics of food, such as pH, water activity, carbon source, nitrogen source and oxygen molecule, the environmental conditions for the formation of microorganisms and antibiotics in different foods are also different. For example, the pH of food is the condition that affects microbial proliferation. Water activity also has the same factors that affect the antibacterial activity of microorganisms and the stabilization of active substances. The oxygen in the top gap in the packaging can be used by aerobic microorganisms. The oxygen permeability of packaging materials changes the oxygen concentration in the top gap

therefore, in order to design antibacterial packaging, it is essential to study the pH, water activity, oxygen permeability of packaging materials and microbial properties of food

storage temperature the temperature of food storage can change the antibacterial activity of chemical preservatives. The temperature conditions in the manufacturing and distribution flow determine the degree of heat influence on the antibacterial activity, so it needs to be recorded for future reference. The combination of heat treatment, storage temperature and chemical preservatives can increase the sensitivity of microorganisms to heat and chemical drugs, resulting in the effect of increasing the efficacy. Volatile chemicals can affect the oxygen in the top gap of the package

the simplest movement system of substances is the diffusion of packaging materials to food to release active ingredients. There are at least two layers of space between the packaging materials and food in the antibacterial packaging. When using composite materials, it can be a spacing structure with more than three layers. At this time, the diffusivity of each layer interval of the active material can affect the overall diffusion morphology and results. At the same time, the diffusion of antibacterial active ingredients in food also affects the overall diffusion effect

the antibacterial agent release system with multilayer structure is composed of the barrier outer layer of the antibacterial agent, the antibacterial agent containing layer, the release control layer and the surface layer reaching the food. The control layer is a key layer designed to control the initial release time and bactericide penetration. The thickness and corresponding diffusivity of the packaging structure layer should be specially designed according to different microbial spoilage and food characteristics. The antibacterial activity control layer is a composite layer composed of an antibacterial layer and an active substance carrier layer. Like the film, the container can be made of multi-layer materials through vacuum blistering and compressed air forming. Paper and plastic are the same. There are also antibacterial paper packaging materials. Paper is a porous material, and the antibacterial agent can be perforated. Its antibacterial activity can also be improved by low wood properties such as water content, gas permeability, physical strength, optical properties and surface properties

the physical properties of packaging materials are to reduce food spoilage caused by microorganisms. Adding antibacterial active substances to packaging materials will generally affect the physical properties, processability and mechanical applicability of packaging materials. Slight changes have taken place in the mechanical processing properties of the material, such as tensile strength, fracture strength and toughness, as well as the permeability to oxygen, water vapor permeability, wettability, water absorption, oil resistance, brightness and gloss

however, even if active substances are added, the performance of packaging materials must be maintained. The ratio of activator molecules added in plastic materials to general copolymers is much smaller, and the amount added is also very small. When designing an excellent antibacterial packaging system, chemicals are distributed in the amorphous structure of polymers, which will not greatly affect the mechanical strength of plastic packaging materials. It has been reported that adding potassium sorbate to LDPE film will not affect the change of tensile strength

if we consider that the influence of larger antibacterial molecules on the amorphous field of polymers will not be much different from that of relatively small antibacterial molecules, and the change will not be great. However, in the field of polymer amorphous and paper porous, high concentration of antibacterial substances and saturated large powder particles will have a greater impact. The addition of antibacterial agents can not only change the mechanical strength of packaging materials, but also reduce the transparency. For example, the transparency of LDPE film can decrease with the increase of the amount of potassium sorbate added

Author: jiangshaohua source: China environmental protection ink

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