Cutting - Edge Preservation Technologies for Prolonging Preserved Fruit Shelf - Life

Preserved fruits, despite their relatively long - established shelf - life due to processing, still face challenges of quality degradation during storage and distribution, such as mold growth, spoilage, and taste deterioration. Consequently, the development of advanced preservation technologies for preserved fruits is of great significance for extending their shelf - life and maintaining their high - quality standards. In recent years, with the rapid progress of science and technology, a series of innovative preservation technologies for preserved fruits have emerged.

Modified atmosphere packaging (MAP) is one of the most widely applied preservation methods at present. Its underlying principle is to alter the gas composition in the storage environment by reducing the oxygen content and increasing the carbon dioxide content. This modification inhibits the growth and reproduction of microorganisms and slows down the respiration of fruits, thereby delaying the spoilage process of preserved fruits. In the context of preserved fruit preservation, commonly used MAP materials include polyethylene (PE) and polypropylene (PP). These materials possess excellent gas - barrier properties, enabling effective control of the gas composition within the package. For example, when preserved fruits are packaged in a MAP bag containing nitrogen, carbon dioxide, and a small amount of oxygen and stored at an appropriate temperature, their shelf - life can be significantly extended. Research indicates that the use of MAP technology can extend the shelf - life of preserved fruits by 2 - 3 times while maintaining their color, taste, and nutritional value.

Coating preservation technology involves applying an edible protective film to the surface of preserved fruits. This film serves to isolate oxygen, moisture, and microorganisms, thereby achieving the goal of preservation. There is a wide variety of coating materials available, with common ones including polysaccharides, proteins, and lipids. Polysaccharide - based coating materials like chitosan exhibit good film - forming properties, antibacterial activity, and biocompatibility. When a chitosan solution is applied to the surface of preserved fruits and allowed to dry, a transparent film is formed, which effectively inhibits mold growth, reduces water evaporation, and maintains the softness and luster of the preserves. Protein - based coating materials such as gelatin also have good film - forming capabilities and can endow preserved fruits with a certain degree of elasticity. Lipid - based coating materials, such as beeswax, can enhance the water - resistance of the coating. In practical applications, a combination of multiple coating materials is often used to achieve a synergistic preservation effect. For example, a composite coating solution made by mixing chitosan and gelatin in a specific ratio and adding an appropriate amount of glycerol as a plasticizer shows enhanced preservation performance for preserved fruits.

Biological preservation technology utilizes biological agents to inhibit the growth of harmful microorganisms, thereby ensuring the preservation of preserved fruits. Probiotics and biological enzymes are important components of this technology. Probiotics, such as lactic acid bacteria, can produce organic acids like lactic acid, which lower the environmental pH and inhibit the growth of harmful microorganisms. Spraying lactic acid bacteria fermentation broth on the surface of preserved fruits or incorporating it into the packaging materials can effectively preserve the fruits. Biological enzymes, such as glucose oxidase, can consume the oxygen in the package, creating an anaerobic environment that inhibits the growth of aerobic microorganisms. Additionally, glucose oxidase can convert glucose into gluconic acid, further reducing the pH of the preserved fruits and enhancing the preservation effect. Studies have found that the use of biological preservation technology significantly reduces the number of microorganisms in preserved fruits during storage and effectively extends their shelf - life.

Irradiation preservation technology involves treating preserved fruits with ionizing radiation. By disrupting the DNA structure of microorganisms, it renders them incapable of reproduction, thus achieving the objectives of sterilization and preservation. Irradiation preservation offers advantages such as thorough sterilization, no residue, and no adverse impact on the quality of preserved fruits. Common irradiation sources include γ - rays and electron beams. During the irradiation preservation of preserved fruits, strict control of the irradiation dose is essential to ensure that it effectively kills harmful microorganisms without compromising the nutritional value and taste of the fruits. Generally, the appropriate irradiation dose ranges from 1 - 5 kGy. Research shows that after irradiated preserved fruits are stored at room temperature for 6 months, their microbial indicators still meet national standards, and there are no significant differences in color, taste, and nutrients compared to non - irradiated counterparts.

Nanotechnology - based preservation is a novel preservation technology that has emerged in recent years. Due to their unique size and surface effects, nanomaterials possess excellent antibacterial, antioxidant, and gas - barrier properties. The application of nanomaterials in the field of preserved fruit preservation has led to the development of high - performance preservation packaging materials and preservatives. For example, incorporating silver nanoparticles into packaging materials to create nanosilver - antibacterial packaging materials can effectively inhibit microbial growth and extend the shelf - life of preserved fruits. Moreover, nano - titanium dioxide has photocatalytic activity and can generate free radicals under light conditions to decompose harmful gases and microorganisms in the package, thereby playing a role in preservation. Nanotechnology - based preservation provides new perspectives and methods for the preservation of preserved fruits and holds great promise for future applications.

The continuous emergence of new preservation technologies for preserved fruits provides strong impetus for the development of the preserved - fruit industry. MAP, coating preservation, biological preservation, irradiation preservation, and nanotechnology - based preservation technologies each have their own unique advantages. Through rational selection and comprehensive application of these technologies, the shelf - life of preserved fruits can be effectively extended, their high - quality standards can be maintained, and consumers' demands for high - quality preserved fruits can be met. With the continuous advancement of science and technology, it is expected 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.