真(zhen)空(kong)(kong)充(chong)氣(qi)(qi)(qi)包裝在真(zhen)空(kong)(kong)后再(zai)充(chong)入氮(dan)氣(qi)(qi)(qi)、二氧(yang)(yang)(yang)化(hua)碳、氧(yang)(yang)(yang)氣(qi)(qi)(qi)單一(yi)氣(qi)(qi)(qi)體(ti)或(huo)二、三種氣(qi)(qi)(qi)體(ti)的混合(he)氣(qi)(qi)(qi)體(ti)。其氮(dan)氣(qi)(qi)(qi)是(shi)惰性(xing)氣(qi)(qi)(qi)體(ti)，起(qi)充(chong)填作用(yong)，使袋內保(bao)持正壓，以防止袋外空(kong)(kong)氣(qi)(qi)(qi)進入袋內，對食品起(qi)到一(yi)個保(bao)護作用(yong)。其二氧(yang)(yang)(yang)化(hua)碳能夠溶于各類(lei)脂肪或(huo)水，引成酸性(xing)較弱(ruo)的碳酸，有(you)抑制霉菌、腐敗細菌等微(wei)生(sheng)物的活性(xing)。其氧(yang)(yang)(yang)氣(qi)(qi)(qi)具有(you)抑制厭氧(yang)(yang)(yang)菌的生(sheng)長繁殖，保(bao)持水果、蔬菜的新鮮(xian)及色(se)彩，高濃度氧(yang)(yang)(yang)氣(qi)(qi)(qi)可使新鮮(xian)肉類(lei)保(bao)持其鮮(xian)紅(hong)色(se)。