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Research Progress on New Preservation Technologies for Preserved Fruits

Preserved fruits, as a processed food, although they have a relatively long shelf - life, still face problems such as quality degradation during storage and circulation, such as mold growth, spoilage, and deterioration of taste. Therefore, the development of new preservation technologies for preserved fruits is of great significance for extending the shelf - life of preserved fruits and maintaining their good quality. In recent years, with the continuous progress of science and technology, a series of new preservation technologies for preserved fruits have emerged.

Modified atmosphere packaging (MAP) technology is currently a widely used preservation method. Its principle is to change the gas composition in the storage environment, reduce the oxygen content, and increase the carbon dioxide content, thereby inhibiting the growth and reproduction of microorganisms and the respiration of fruits, and delaying the spoilage process of preserved fruits. In the preservation of preserved fruits, commonly used MAP materials include polyethylene (PE), polypropylene (PP), etc. These materials have good gas - barrier properties and can effectively control the gas composition in the package. For example, when preserved fruits are packed in a MAP bag containing nitrogen, carbon dioxide, and a small amount of oxygen and stored at an appropriate temperature, the shelf - life of the preserved fruits can be significantly extended. Studies have shown that using MAP technology, the shelf - life of preserved fruits can be extended by 2 - 3 times, and at the same time, the color, taste, and nutrients of the preserved fruits can be well retained.

Coating preservation technology involves coating an edible protective film on the surface of preserved fruits. This film can isolate oxygen, moisture, and microorganisms, thereby achieving the purpose of preservation. There are a wide variety of coating materials, and common ones include polysaccharides, proteins, and lipids. Polysaccharide - based coating materials such as chitosan have good film - forming properties, antibacterial properties, and biocompatibility. When a chitosan solution is applied to the surface of preserved fruits and dried, a transparent film is formed, which can effectively inhibit the growth of molds, reduce water evaporation, and maintain the softness and luster of preserved fruits. Protein - based coating materials such as gelatin also have good film - forming properties and can endow preserved fruits with certain elasticity. Lipid - based coating materials such as beeswax can improve the water - resistance of the coating. In practical applications, multiple coating materials are often used in combination to play a synergistic preservation effect. For example, a composite coating solution made by mixing chitosan and gelatin in a certain proportion and adding an appropriate amount of glycerol as a plasticizer has a better preservation effect on preserved fruits.

Biological preservation technology uses biological agents to inhibit the growth of harmful microorganisms, thereby achieving the preservation of preserved fruits. Among them, probiotics and biological enzymes are important components of biological preservation technology. Probiotics such as lactic acid bacteria can produce organic acids such as lactic acid, reducing the pH value of the environment and inhibiting the growth of harmful microorganisms. Spraying lactic acid bacteria fermentation broth on the surface of preserved fruits or adding it to the packaging materials of preserved fruits can play a preservation role. Biological enzymes such as glucose oxidase can consume the oxygen in the package, creating an anaerobic environment, thereby inhibiting the growth of aerobic microorganisms. At the same time, glucose oxidase can also oxidize glucose to gluconic acid, reducing the pH value of preserved fruits and further enhancing the preservation effect. Studies have found that using biological preservation technology, the number of microorganisms in preserved fruits during storage is significantly reduced, and the shelf - life is effectively extended.

Irradiation preservation technology uses ionizing radiation to treat preserved fruits. By destroying the DNA structure of microorganisms, it makes them lose their reproductive ability, thereby achieving the purpose of sterilization and preservation. Irradiation preservation has the advantages of thorough sterilization, no residue, and no impact on the quality of preserved fruits. Common irradiation sources include γ - rays and electron beams. During the irradiation preservation process of preserved fruits, the irradiation dose needs to be strictly controlled to ensure that it can effectively kill harmful microorganisms without causing adverse effects on the nutrients and taste of preserved fruits. Generally, the appropriate irradiation dose is 1 - 5 kGy. Studies have shown that after irradiated preserved fruits are stored at room temperature for 6 months, the microbial indicators still meet the national standards, and there is no significant difference in the color, taste, and nutrients of the preserved fruits compared with non - irradiated ones.

Nanotechnology - based preservation is a new preservation technology that has emerged in recent years. Due to their unique size effect and surface effect, nanomaterials have excellent antibacterial, antioxidant, and gas - barrier properties. Applying nanomaterials to the field of preserved fruit preservation can develop high - performance preservation packaging materials and preservatives. For example, adding silver nanoparticles to packaging materials to make nanosilver antibacterial packaging materials can effectively inhibit the growth of microorganisms and extend the shelf - life of preserved fruits. In addition, nano - titanium dioxide has photocatalytic activity and can generate free radicals under light conditions to decompose harmful gases and microorganisms in the package, thus playing a preservation role. Nanotechnology - based preservation provides new ideas and methods for the preservation of preserved fruits and has broad application prospects.

The continuous emergence of new preservation technologies for preserved fruits provides strong support for the development of the preserved - fruit industry. MAP, coating preservation, biological preservation, irradiation preservation, and nanotechnology - based preservation technologies each have their own advantages. By reasonably selecting and comprehensively applying these technologies, the shelf - life of preserved fruits can be effectively extended, the good quality of preserved fruits can be maintained, and consumers' demands for high - quality preserved fruits can be met. With the continuous progress of science and technology, it is believed that more advanced and efficient preservation technologies will be applied to the field of preserved fruit preservation in the future, promoting the sustainable development of the preserved - fruit industry.


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