真空(kong)充(chong)(chong)氣(qi)包裝在真空(kong)后(hou)再充(chong)(chong)入氮氣(qi)、二氧(yang)(yang)化碳(tan)、氧(yang)(yang)氣(qi)單(dan)一(yi)氣(qi)體或(huo)二、三種(zhong)氣(qi)體的混合氣(qi)體。其(qi)(qi)氮氣(qi)是惰性氣(qi)體，起(qi)充(chong)(chong)填作用(yong)(yong)，使袋內保(bao)持正壓，以防止袋外(wai)空(kong)氣(qi)進入袋內，對食品(pin)起(qi)到一(yi)個保(bao)護作用(yong)(yong)。其(qi)(qi)二氧(yang)(yang)化碳(tan)能夠溶于(yu)各類(lei)脂肪或(huo)水，引成酸(suan)性較弱的碳(tan)酸(suan)，有(you)抑制(zhi)霉菌、腐敗細菌等微生(sheng)物的活性。其(qi)(qi)氧(yang)(yang)氣(qi)具有(you)抑制(zhi)厭氧(yang)(yang)菌的生(sheng)長繁殖，保(bao)持水果(guo)、蔬菜的新鮮(xian)(xian)及色(se)彩，高(gao)濃度氧(yang)(yang)氣(qi)可(ke)使新鮮(xian)(xian)肉(rou)類(lei)保(bao)持其(qi)(qi)鮮(xian)(xian)紅色(se)。