Modified atmosphere packaging of the hottest fruit

The modified atmosphere packaging of fruits and vegetables

as mentioned in b2.01 above, after the harvest of fruits and vegetables, their metabolism continues, continues to consume oxygen, and releases carbon dioxide at the same time. In the closed packaging (or storage) environment, with the continuous respiration and metabolism of fruits and vegetables, the oxygen content also decreases, gradually forming anaerobic conditions, promoting the enzymatic transformation of fruits and vegetables and the proliferation of fungi, and producing mold, resulting in the deterioration and decay of products. In recent years, selecting plastic films with different air permeability and moisture permeability to adjust the different gas proportion inside the package can not only meet the needs of different fruits and vegetables to breathe, but also further control their breathing speed. See table 4-1 for the comparative data of oxygen permeability and carbon dioxide permeability of several films used in vegetable packaging

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① it is coated with a mixture of paraffin, polyethylene and random polypropylene, including 65% paraffin, 5% polyethylene and 30% random polypropylene

it is impossible to adapt and meet the respiratory characteristics of all fruits and vegetables by using any single film in the table. Therefore, the use of a single membrane often requires drilling in order to supplement oxygen and discharge carbon dioxide. If it is packed in bags, it is actually the same as the composition in the atmosphere, that is, oxygen 21%, nitrogen 79%

if two layers of single films with different air permeability are used to compound together, the heat sealing performance of the inner film is good, and the air permeability of the outer film is completely different from that of the inner layer. This combination can adjust the balance of nitrogen, carbon dioxide and oxygen content in the packaging, so as to meet the respiratory needs of different fruits and vegetables

according to the above principle, the inner layer material can be a transparent film, and the ratio of carbon dioxide and oxygen transmittance is about 4:1. Such films include polyvinyl chloride, nylon, chlorinated rubber, polyethylene, polystyrene and polypropylene, whose carbon dioxide to oxygen transmittance ratio is greater than 4. 7

the carbon dioxide and oxygen permeability of the outer material is 0.25 lower than that of the inner material. In general, the oxygen permeability of outer materials is not greater than 3oml/m2 · 24h. PVDC and its plastic coating materials can meet this requirement. Therefore, the inner and outer composite materials can be of the following structure: the inner material is polyethylene film, and the outer material is polyvinylidene chloride coated polyethylene. "I:o@

Table 4-2 lists the appropriate film permeability (at 25 ℃) of modified atmosphere packaging for several common fruits and vegetables."

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in some cases, the oxygen content in the internal space of the package is only less than 15%. Even, sometimes only a small amount of oxygen is required, and the rest are diluted with nitrogen or carbon dioxide to control the premature ripening of fruits and vegetables. However, the lower limit of oxygen containing tray should be on the premise of not causing anaerobic conditions.

lettuce can be wrapped with polyoxyethylene film, and the ratio of carbon dioxide transmittance to oxygen transmittance should be at least 3.0, that is, the oxygen transmittance should be more than 2000, and the carbon dioxide transmittance should be more than 10000. The more suitable oxygen permeability is in the range of 2250-4o00, and the carbon dioxide permeability is in the range of 12500 ~ 25000

lettuce should not be wrapped with polyethylene film, because it is easy to cause the reproduction and invasion of anaerobic bacteria, resulting in the production of alcohols, aldehydes and acids; The carbon dioxide in the package is easy to increase, which is very unsafe unless cold storage and low temperature control are adopted

the sales package of bananas can be expanded polystyrene shallow dish containers for meat packaging, with each 3-5 bananas packed in a shallow dish, and the surface covered with plastic film. The permeability of plastic film should be in the range of 4-10, that is, the oxygen permeability is more than 2000, and the carbon dioxide permeability is more than 8000. Wrap and heat seal the plastic shallow dish containing bananas with PVC film with a thickness of about 20 um. The oxygen permeability of poly vinyl film is 2700, and the carbon dioxide permeability also needs to often use antirust oil to prevent rust to 17000. The ratio of the latter to the former is 6.3, and the concentration of ethylene gas in the system is less than 10ppm. If ethylene vinyl acetate film (ethylene content is 82%, vinyl acetate content is 18%) is used to replace PVC film, satisfactory results can also be achieved. The oxygen permeability of this film is 2100 and the carbon dioxide permeability is 8400, and the ratio of the two is 4

source: Food Forum

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