New progress in fresh-keeping packaging of the hot

2022-07-29
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New progress in fresh-keeping packaging of vegetables and fruits (Part I)

with the development of economy and the improvement of living standards, people's dietary life has changed from a single type of food and clothing in the past to a diversified type of nutrition now. At present, the demand for vegetables and fruits is increasing, and the demand for freshness is also increasing

vegetables and fruits maintain life through respiration during storage. In the process of respiration, vegetables and fruits inhale oxygen, exhale carbon dioxide, produce ethylene gas, and reduce water content. Respiration will cause internal component consumption, meat softening and reduced nutritional value; Ethylene gas can promote the aging of vegetables and fruits and accelerate the respiration; The moisture content in vegetables and fruits is as high as 85%-95%. If the moisture loss reaches 5%, the appearance will wilt and reduce the commodity value; If it turns yellow, the content of vitamin C will decrease. It can be seen that respiration is the main factor affecting the freshness of vegetables and fruits. In addition, the corrosion of pathogenic microorganisms is another factor that causes the decrease of vegetable freshness

the so-called food preservation technology is to maintain the freshness of food and inhibit food deterioration. The application of carbon fiber composite technology for the preservation of vegetables and fruits provides the best choice for automobile lightweight, mainly to inhibit their respiration and the proliferation rate of bacteria. The respiration of vegetables and fruits and the increment of microorganisms are related to the storage temperature, humidity and gas composition. Generally speaking, low temperature, high humidity, low oxygen, high carbon dioxide, low ethylene and sterile environment are conducive to the preservation of vegetables and fruits. Therefore, the main methods of preservation are to maintain low temperature, control water evaporation, adjust the gas environment, remove ethylene gas, sterilize and antibacterial. The main fresh-keeping materials of vegetables and fruits include functional fresh-keeping film, new corrugated box, functional fresh-keeping agent, etc

functional fresh-keeping film

although the traditional film can play the role of packaging and has a certain fresh-keeping effect, it obviously can not meet the fresh-keeping needs of the modern market. Therefore, a large number of new fresh-keeping films have been developed. These functional fresh-keeping films not only have the effect of preventing water evaporation and simply controlling gas, but also further improve the freshness of vegetables and fruits

ethylene adsorption film. The purpose of ethylene adsorption film is to remove harmful ethylene gas. The plastic film (especially LDPE) is mixed with gas adsorption porous substances, such as tuff and zeolite, quartzite and silica, clay minerals, stone powder and other micro powders, most of which can adsorb ethylene or isolate far-infrared radiation. The mechanism of adsorbing ethylene is that the pores on the surface of porous inorganic matter can capture ethylene, and even in the case of high moisture, the water molecules in the pores can be replaced with ethylene. However, the addition amount of gas adsorbent is 3%-5%, because the adsorption capacity of ethylene gas is limited. At present, in foreign countries, there will be a climax in the replacement of imported tuffaceous films. Domestic films call for more use of domestic materials, mainly adding silicon anhydride ceramics, with good results

anti dew film. The fresh-keeping films for vegetables and fruits are generally made of low-density polyethylene, polypropylene, polystyrene, ethylene vinyl acetate copolymer and polyvinyl chloride resins with high gas permeability. However, when the water vapor generated by the vegetables and fruits packed with these films condenses on the inner surface of the film, it not only makes the transparency poor, but also makes the water droplets gather, which makes the bacteria proliferate quickly, resulting in the corruption of vegetables and fruits. What can solve this problem is the anti dew film. The anti-corrosion film uses the surfactant to treat the inner surface of the above polyethylene, polypropylene, polystyrene and other materials, which can absorb excess water and properly maintain the humidity in the package, so as to achieve the purpose of fresh preservation. Fatty acid esters can be used as both food additives and anti dew agents

antibacterial film. Antibacterial film is the mixture of antibacterial silver zeolite into the film. Silver zeolite is the mixture of antibacterial silver and sodium ion in zeolite crystal structure or silver ion and synthetic loose zeolite with aluminum and silicon as raw materials. PE, PP and PS are mainly used as base materials. The film can inhibit the proliferation of bacteria to a certain extent and play a role in keeping fresh

fresh-keeping corrugated box

corrugated box is a commodity transportation packaging container which is currently mainly used for goods with the tension between consumption and production ≥ 8N, the bending resistance of the handle of adult toothbrush ≥ 80N or the deformation limit range is endless. It has attracted great attention in the fresh-keeping of vegetables and fruits. (to be continued)

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