The principle of fresh fruit and vegetable modified atmosphere packaging

After fresh fruits and vegetables are packaged and sealed with breathable plastic film, the respiration of fruits and vegetables consumes O2 in the air in the package and generates almost the same amount of CO2, which gradually constitutes the gas concentration difference between the package and the atmospheric environment. The O2 in the air penetrates into the packaging through the plastic film to supplement the consumed O2, and the CO2 in the packaging penetrates the plastic film and diffuses into the air. At the beginning, the gas concentration difference between the inside and outside of the packaging film is small, and the O2 infiltrating into the packaging is not enough to offset the consumption. Yes, the CO2 exuded is less than the CO2 produced. As the difference in gas concentration inside and outside the package increases during storage, the rate of gas permeation increases. When the rate of O2 consumption in the package is equal to the rate of O2 infiltration, and the rate of CO2 production is equal to the rate of exudation, a low O2 and low CO2 modified atmosphere equilibrium concentration may be reached in the package. If the balanced concentration of gas in the package makes the fruits and vegetables produce only weak aerobic respiration without anaerobic respiration, then the fruits and vegetables are placed in a better atmosphere environment to slow down the ripening and aging process of fruits and vegetables as much as possible and obtain great freshness preservation. Effect. Forms of Modified Atmosphere Establishment in Packaging There are two forms of modified atmosphere establishment in modified atmosphere packaging of fruits and vegetables: inflatable or active modified atmosphere packaging and spontaneous modified atmosphere packaging

1. Spontaneous modified atmosphere packaging The so-called spontaneous modified atmosphere is to use the respiratory activities of fruits and vegetables sealed in plastic films to consume O2 and of the air in the packaging to generate CO2, gradually forming a low O2 and high CO2 (relative to air) modified atmosphere environment in the packaging, And through the gas exchange between the plastic film and the atmosphere to maintain the gas in the package. If the respiration rate of fruits and vegetables matches the air permeability of the film, a controlled atmosphere balance that is beneficial to the storage of fruits and vegetables will be slowly established in the package; if the air permeability of the selected film is insufficient, an air pressure detrimental to the storage of fruits and vegetables will be automatically established in the package. Anaerobic conditioning or harmful high concentrations of CO2. At present, the fresh-keeping packaging of fresh fruits and vegetables generally adopts the form of spontaneous packaging, such as wrapping the tomatoes in plastic trays and fresh-cut vegetables in plastic film with fresh-keeping film. The preservation effect depends on the air permeability of the plastic film.

2. Inflatable or active modified atmosphere packaging The meaning of inflatable modified packaging of fresh fruits and vegetables is to actively create modified atmosphere conditions conducive to the storage of fruits and vegetables. It is a kind of active packaging, so it is also called active modified atmosphere packaging. There are two ways to establish modified atmosphere in inflatable modified atmosphere packaging: one is to put the superplasticizer into a plastic packaging bag or box, first extract the air to form a partial vacuum, and then fill it with a mixed gas of low O2 and high concentration of CO2 or fill it with N 2 dilutes the residual oxygen in the package to obtain an air-conditioned environment with low O2 concentration, and then seals it; the other is to seal the absorbent of C2H4, O2, CO2 or the release bag in the package to quickly establish a low O2 to CO2 concentration. Modified atmosphere, and eliminate the C2H4 gas that makes fruits and vegetables ripen, also known as active packaging, inflatable or active modified atmosphere packaging to establish a modified atmosphere balance, like spontaneous modified atmosphere packaging, requires gas exchange between the plastic film and the atmosphere.