真(zhen)空袋(dai)(dai)的主(zhu)要作用(yong)(yong)是(shi)除(chu)氧(yang)(yang)，以有利于防(fang)止(zhi)食(shi)(shi)(shi)品變(bian)質(zhi)，其原理也比較簡單(dan)，因食(shi)(shi)(shi)品霉腐變(bian)質(zhi)主(zhu)要由微(wei)(wei)(wei)生(sheng)(sheng)(sheng)物(wu)(wu)(wu)的活動造成，而大多(duo)數微(wei)(wei)(wei)生(sheng)(sheng)(sheng)物(wu)(wu)(wu)（如霉菌(jun)和(he)(he)(he)酵母(mu)菌(jun)）的生(sheng)(sheng)(sheng)存是(shi)需要氧(yang)(yang)氣的，而真(zhen)空包裝就是(shi)運用(yong)(yong)這個原理，把(ba)包裝袋(dai)(dai)內(nei)和(he)(he)(he)食(shi)(shi)(shi)品細胞(bao)內(nei)的氧(yang)(yang)氣抽掉，使(shi)微(wei)(wei)(wei)物(wu)(wu)(wu)物(wu)(wu)(wu)失去(qu)“生(sheng)(sheng)(sheng)存的環境”。實驗證明：當(dang)包裝袋(dai)(dai)內(nei)的氧(yang)(yang)氣濃度≤1%時(shi)(shi)，微(wei)(wei)(wei)生(sheng)(sheng)(sheng)物(wu)(wu)(wu)的生(sheng)(sheng)(sheng)長和(he)(he)(he)繁(fan)殖(zhi)速(su)度就急劇(ju)下降，氧(yang)(yang)氣濃度≤0.5%時(shi)(shi)，大多(duo)數微(wei)(wei)(wei)生(sheng)(sheng)(sheng)物(wu)(wu)(wu)將受到抑制(zhi)而停止(zhi)繁(fan)殖(zhi)。（注：真(zhen)空包裝不(bu)能抑制(zhi)厭氧(yang)(yang)菌(jun)的繁(fan)殖(zhi)和(he)(he)(he)酶(mei)反(fan)應引起(qi)的食(shi)(shi)(shi)品變(bian)質(zhi)和(he)(he)(he)變(bian)色(se)，因此(ci)還(huan)需與(yu)其它輔助方法結合(he)，如冷藏、速(su)凍、脫水(shui)、高溫殺(sha)菌(jun)、輻照 滅菌(jun)、微(wei)(wei)(wei)波(bo)殺(sha)菌(jun)、鹽腌制(zhi)等。）真(zhen)空除(chu)氧(yang)(yang)除(chu)了抑制(zhi)微(wei)(wei)(wei)生(sheng)(sheng)(sheng)物(wu)(wu)(wu)的生(sheng)(sheng)(sheng)長和(he)(he)(he)繁(fan)殖(zhi)外，另一個重要功能是(shi)防(fang)止(zhi)食(shi)(shi)(shi)品氧(yang)(yang)化，因油脂類食(shi)(shi)(shi)品中含有大量不(bu)飽和(he)(he)(he)脂肪酸，受氧(yang)(yang)的作用(yong)(yong)而氧(yang)(yang)化，使(shi)食(shi)(shi)(shi)品變(bian)味、變(bian)質(zhi)，此(ci)外，氧(yang)(yang)化還(huan)使(shi)維生(sheng)(sheng)(sheng)素A和(he)(he)(he)C損(sun)失，食(shi)(shi)(shi)品色(se)素中的不(bu)穩定物(wu)(wu)(wu)質(zhi)受氧(yang)(yang)的作用(yong)(yong)，使(shi)顏色(se)變(bian)暗。所以，除(chu)氧(yang)(yang)能有效(xiao)地防(fang)止(zhi)食(shi)(shi)(shi)品變(bian)質(zhi)，保(bao)持其色(se)、香、味及(ji)營養價值。