At present, the industrial production of edible fungus mushroom is one of the world's scale has been reached. Mushroom northern China in the winter season cultivation, in winter and spring vegetables off-season market, expensive, and thus produce higher efficiency. Bags mushroom is good or bad, mainly by mushroom color, Guti size uniformity, tenderness, flavor, clarity and soup several aspects of the decision. Any mushroom color yellow, uniform size, delicious, tender and crisp texture, the soup is clear who as a top grade. Mushroom pollution-free food, often using modified atmosphere packaging. Overview of MAP refers to the replacement of MAP with a protective gas atmosphere packaging for food preservation container to inhibit the reproduction of bacteria to achieve a long-term storage and preservation methods. The basic principles of food preservation is the use of MAP preservative gas (pure gas, or 2 to 4-gas mixing ratio according to food properties), boxes or bags of air replacement, change boxes (bags) of food external environment, inhibit bacteria (microbes) in growth and reproduction, slow down the metabolic rate of fresh fruits and vegetables, fresh fruits and vegetables slow the aging process, thus prolonging the shelf or shelf life of food products. In fresh mushroom fresh example: After picking fresh mushroom still respire, consuming O2 produce CO2, increasing the CO2 content of the environment and to reduce the concentration of O2, the use of plastic film high permeability gas exchange with the atmosphere, add O2 consumed and discharged CO2. When the gas permeation rate of films and mushroom equal respiration rate, packaging bags of gas reaches a certain equilibrium concentration can make mushroom maintain weak respiratory rate without anaerobic respiration, thus delaying the mature and get fresh. MAP could not use preservatives to ensure that the taste, nutrients and shelf life of food additives under the premise. Mushroom gas preservative gas atmosphere packaging is generally used in carbon dioxide (CO2), nitrogen (N2), oxygen (O2) and special gases (NO2, SO2, Ar etc.). Effect of various gases as follows. (1) Carbon dioxide (CO2) CO2 content of normal air is 0.03%, a high concentration of carbon dioxide, the vast majority of corruption can inhibit the growth of microorganisms. Wherein the aerobic (such as mold) and some other bacteria most sensitive to high concentrations of CO2; facultative anaerobes (such as yeast, etc.) CO2 is less sensitive, less inhibition; anaerobes (such as lactic acid) is Inhibition of the worst. Antibacterial Mechanism of CO2 in the following areas. a, CO2 penetrate bacterial cells, bacterial and intracellular pH value decreased enzyme activity decreased. b, dehydroxyfluorination enzyme is inhibited by CO2 enrichment. c, the presence of non-dehydroxylation enzyme is inhibited by an enzyme CO2. d, since the bacterial cell membrane is dissolved CO2, and changes in its nature a function is inhibited. CO2 gas can inhibit the growth of most spoilage bacteria and molds propagation effects, fresh gas is the main antibacterial agent, CO2 high concentrations can hinder aerobic bacteria and fungi and other microbial proliferation, microbial growth to extend the period of stagnation and exponential growth stage, starting corrosion mildew. (2) oxygen (O2) O2 inhibit most anaerobic bacterial growth and reproduction, to keep raw meat color, and the role of maintaining the fruit and vegetable freshness of respiratory metabolism. (3) nitrogen (N2) N2 is an inert gas, generally do not react with food effect, nor is absorbed by the food, make the filling gas used in modified atmosphere and prevent the escape of CO2 and other gases from the package leaving the package slump, in the application of N2 N2 must pay attention to purity and quality through membrane separation or pressure swing adsorption to separate it from the compressed air out of the nitrogen purity of 99.9%. N2 purity for use in food packaging must meet the nitrogen level (ie, security level). Different food and fruit ingredients and fresh gas is not the same proportion of key crops MAP, it is the oxygen permeability of packaging materials and breathing rate to match the product.