真(zhen)空(kong)袋(dai)(dai)的(de)主要作用(yong)是除(chu)(chu)氧(yang)(yang)(yang)(yang)，以(yi)有(you)(you)利于防止(zhi)(zhi)食(shi)(shi)(shi)品變(bian)(bian)(bian)質(zhi)(zhi)(zhi)，其原(yuan)理(li)(li)也(ye)比較簡單，因食(shi)(shi)(shi)品霉(mei)腐(fu)變(bian)(bian)(bian)質(zhi)(zhi)(zhi)主要由微(wei)(wei)(wei)(wei)(wei)生物(wu)的(de)活動造(zao)成(cheng)，而大多數微(wei)(wei)(wei)(wei)(wei)生物(wu)（如霉(mei)菌(jun)和(he)酵(jiao)母菌(jun)）的(de)生存是需(xu)要氧(yang)(yang)(yang)(yang)氣的(de)，而真(zhen)空(kong)包裝就(jiu)是運用(yong)這個原(yuan)理(li)(li)，把包裝袋(dai)(dai)內(nei)(nei)和(he)食(shi)(shi)(shi)品細胞(bao)內(nei)(nei)的(de)氧(yang)(yang)(yang)(yang)氣抽掉，使(shi)(shi)微(wei)(wei)(wei)(wei)(wei)物(wu)物(wu)失去“生存的(de)環境(jing)”。實驗證明：當包裝袋(dai)(dai)內(nei)(nei)的(de)氧(yang)(yang)(yang)(yang)氣濃(nong)度≤1%時(shi)，微(wei)(wei)(wei)(wei)(wei)生物(wu)的(de)生長(chang)和(he)繁殖(zhi)速(su)度就(jiu)急劇下降，氧(yang)(yang)(yang)(yang)氣濃(nong)度≤0.5%時(shi)，大多數微(wei)(wei)(wei)(wei)(wei)生物(wu)將受(shou)到抑(yi)制(zhi)而停止(zhi)(zhi)繁殖(zhi)。（注：真(zhen)空(kong)包裝不能(neng)抑(yi)制(zhi)厭氧(yang)(yang)(yang)(yang)菌(jun)的(de)繁殖(zhi)和(he)酶反應引起的(de)食(shi)(shi)(shi)品變(bian)(bian)(bian)質(zhi)(zhi)(zhi)和(he)變(bian)(bian)(bian)色(se)(se)，因此還需(xu)與(yu)其它輔助方法結合(he)，如冷藏、速(su)凍、脫水(shui)、高溫殺菌(jun)、輻照 滅(mie)菌(jun)、微(wei)(wei)(wei)(wei)(wei)波殺菌(jun)、鹽(yan)腌制(zhi)等(deng)。）真(zhen)空(kong)除(chu)(chu)氧(yang)(yang)(yang)(yang)除(chu)(chu)了抑(yi)制(zhi)微(wei)(wei)(wei)(wei)(wei)生物(wu)的(de)生長(chang)和(he)繁殖(zhi)外(wai)(wai)，另一個重要功能(neng)是防止(zhi)(zhi)食(shi)(shi)(shi)品氧(yang)(yang)(yang)(yang)化，因油脂類食(shi)(shi)(shi)品中含有(you)(you)大量不飽和(he)脂肪酸，受(shou)氧(yang)(yang)(yang)(yang)的(de)作用(yong)而氧(yang)(yang)(yang)(yang)化，使(shi)(shi)食(shi)(shi)(shi)品變(bian)(bian)(bian)味、變(bian)(bian)(bian)質(zhi)(zhi)(zhi)，此外(wai)(wai)，氧(yang)(yang)(yang)(yang)化還使(shi)(shi)維(wei)生素A和(he)C損失，食(shi)(shi)(shi)品色(se)(se)素中的(de)不穩定物(wu)質(zhi)(zhi)(zhi)受(shou)氧(yang)(yang)(yang)(yang)的(de)作用(yong)，使(shi)(shi)顏(yan)色(se)(se)變(bian)(bian)(bian)暗。所以(yi)，除(chu)(chu)氧(yang)(yang)(yang)(yang)能(neng)有(you)(you)效地防止(zhi)(zhi)食(shi)(shi)(shi)品變(bian)(bian)(bian)質(zhi)(zhi)(zhi)，保持其色(se)(se)、香、味及營養價值。