The fresh-keeping principle of the compound modified atmosphere fresh-keeping packaging machine
1.Compound modified atmosphere preservation packaging is also called gas replacement packaging, and internationally known as MAP packaging (ie Modified Atmosphere Packing). The principle of the composite modified atmosphere packaging machine is to use composite fresh-keeping gas (2-3 kinds of gases are mixed according to the food characteristics) to replace the air in the packaging box or packaging bag, and change the external environment of the food in the box (bag) to achieve suppression The growth and reproduction of bacteria (microorganisms) slows down the metabolism of fresh fruits and vegetables, thereby prolonging the freshness or shelf life of food.
2. Air conditioning and fresh-keeping gas is generally composed of carbon dioxide (CO2), nitrogen (N2), oxygen (O2) and a small amount of special gases. CO2 gas can inhibit the growth and reproduction of most spoilage bacteria and molds, and is the main antibacterial component in the protective gas; O2 can inhibit the growth and reproduction of most anaerobic spoilage bacteria, maintain the color of fresh flesh and maintain aerobic respiration of fresh fruits and vegetables, and maintain The role of freshness; N2 is an inert gas, which does not work with food. As a filling gas, it forms a composite fresh-keeping gas with CO2, O2 and special gases. Different food, fruits and vegetables, the composition and proportion of fresh-keeping gas are also different.
Key technology of modified atmosphere packaging machine
For a qualified composite modified atmosphere fresh-keeping packaging machine, there are two key technical indicators that must meet the corresponding requirements. These two indicators are: one is the gas replacement rate, and the other is the gas mixing accuracy error rate. These two key indicators are needed to judge whether the quality of the composite modified atmosphere preservation packaging equipment is qualified or not. Modified atmosphere preservation gas generally consists of carbon dioxide (CO2), nitrogen (N2), oxygen (O2) and a small amount of special gases.
Carbon dioxide has the effect of inhibiting the growth and reproduction of most spoilage bacteria and molds, and slowing down the metabolism of fresh fruits and vegetables. It is the main antibacterial component in the fresh-keeping gas;
Oxygen has the effect of inhibiting the growth of most anaerobic bacteria, maintaining the color of fresh meat, maintaining aerobic respiration of fresh fruits and vegetables, and maintaining freshness;
Nitrogen is an inert gas and does not work with food. As a filling gas, it forms a composite fresh-keeping gas with carbon dioxide, oxygen and special gases. Different foods, fruits and vegetables require different components and proportions of fresh-keeping gas.
The use of compound modified atmosphere packaging equipment for fresh-keeping packaging of food, fruits and vegetables requires a reasonable requirement for gas mixing accuracy error and gas replacement rate. In the standards of advanced composite modified atmosphere fresh-keeping packaging equipment in developed countries, the gas replacement rate is required to be more than 98%, and the error rate of the fresh-keeping gas mixing accuracy is less than 2%. This is because the above two indicators play a vital role in the preservation of food, fruits and vegetables. Examples are as follows:
Example 1: When lychee is packaged with modified atmosphere preservation, the mixing ratio of the preservation gas is: oxygen (O2) concentration ratio 4%~6%; carbon dioxide (CO2) concentration ratio 3%~5%, damage concentration 8%; the rest is filling gas Nitrogen (N2); if the O2 concentration is low, anaerobic respiration will occur, which will cause the fermentation of litchi fruit and tissue necrosis; the high O2 concentration or the low CO2 concentration will inhibit the decline of litchi metabolism and shorten the shelf life; the high CO2 concentration ( >8%), it will cause damage to the peel and fruit, and accelerate the deterioration of lychees.
Example 2: When packaging stewed vegetables (cooked food) with modified atmosphere preservation, the mixing ratio of the preservation gas is: nitrogen (N2) 64%~66%, carbon dioxide (CO2) 34%~36%, and the gas replacement rate is ≥98%. Since many microorganisms (bacteria) need O2 for their growth and reproduction, reducing the oxygen content can slow down the growth of bacteria (except anaerobic bacteria). Experiments show that a reasonable mixture of N2 and CO2 forms a protective layer with broad-spectrum antibacterial, color and taste on the food surface, and under low oxygen environment, the stewed vegetables can be kept fresh. Therefore, when the gas mixing accuracy error rate and replacement rate cannot reach the target, its antibacterial and fresh-keeping effect is basically invalid.
