真(zhen)空(kong)袋的(de)主(zhu)要(yao)(yao)作(zuo)(zuo)(zuo)用(yong)是除(chu)氧(yang)(yang)(yang)(yang)，以(yi)有利于(yu)防止食(shi)品(pin)變(bian)質(zhi)(zhi)(zhi)(zhi)，其(qi)原理也(ye)比較(jiao)簡單，因食(shi)品(pin)霉腐變(bian)質(zhi)(zhi)(zhi)(zhi)主(zhu)要(yao)(yao)由微(wei)(wei)(wei)(wei)生(sheng)(sheng)(sheng)(sheng)物(wu)(wu)的(de)活動(dong)造(zao)成(cheng)，而(er)大(da)多數微(wei)(wei)(wei)(wei)生(sheng)(sheng)(sheng)(sheng)物(wu)(wu)（如霉菌(jun)和(he)酵(jiao)母菌(jun)）的(de)生(sheng)(sheng)(sheng)(sheng)存是需(xu)要(yao)(yao)氧(yang)(yang)(yang)(yang)氣(qi)的(de)，而(er)真(zhen)空(kong)包裝(zhuang)就是運用(yong)這個原理，把(ba)包裝(zhuang)袋內(nei)和(he)食(shi)品(pin)細胞(bao)內(nei)的(de)氧(yang)(yang)(yang)(yang)氣(qi)抽掉，使微(wei)(wei)(wei)(wei)物(wu)(wu)物(wu)(wu)失(shi)去“生(sheng)(sheng)(sheng)(sheng)存的(de)環境”。實驗證明：當包裝(zhuang)袋內(nei)的(de)氧(yang)(yang)(yang)(yang)氣(qi)濃度(du)≤1%時，微(wei)(wei)(wei)(wei)生(sheng)(sheng)(sheng)(sheng)物(wu)(wu)的(de)生(sheng)(sheng)(sheng)(sheng)長(chang)和(he)繁(fan)殖速度(du)就急劇(ju)下(xia)降，氧(yang)(yang)(yang)(yang)氣(qi)濃度(du)≤0.5%時，大(da)多數微(wei)(wei)(wei)(wei)生(sheng)(sheng)(sheng)(sheng)物(wu)(wu)將(jiang)受(shou)(shou)到(dao)抑(yi)制而(er)停止繁(fan)殖。（注：真(zhen)空(kong)包裝(zhuang)不能抑(yi)制厭氧(yang)(yang)(yang)(yang)菌(jun)的(de)繁(fan)殖和(he)酶(mei)反(fan)應引起的(de)食(shi)品(pin)變(bian)質(zhi)(zhi)(zhi)(zhi)和(he)變(bian)色(se)(se)，因此還需(xu)與其(qi)它輔助(zhu)方法結合，如冷藏、速凍、脫水(shui)、高溫殺菌(jun)、輻照(zhao) 滅菌(jun)、微(wei)(wei)(wei)(wei)波(bo)殺菌(jun)、鹽腌制等。）真(zhen)空(kong)除(chu)氧(yang)(yang)(yang)(yang)除(chu)了抑(yi)制微(wei)(wei)(wei)(wei)生(sheng)(sheng)(sheng)(sheng)物(wu)(wu)的(de)生(sheng)(sheng)(sheng)(sheng)長(chang)和(he)繁(fan)殖外(wai)，另(ling)一個重(zhong)要(yao)(yao)功能是防止食(shi)品(pin)氧(yang)(yang)(yang)(yang)化，因油脂類食(shi)品(pin)中(zhong)含有大(da)量不飽和(he)脂肪酸，受(shou)(shou)氧(yang)(yang)(yang)(yang)的(de)作(zuo)(zuo)(zuo)用(yong)而(er)氧(yang)(yang)(yang)(yang)化，使食(shi)品(pin)變(bian)味、變(bian)質(zhi)(zhi)(zhi)(zhi)，此外(wai)，氧(yang)(yang)(yang)(yang)化還使維生(sheng)(sheng)(sheng)(sheng)素A和(he)C損(sun)失(shi)，食(shi)品(pin)色(se)(se)素中(zhong)的(de)不穩定物(wu)(wu)質(zhi)(zhi)(zhi)(zhi)受(shou)(shou)氧(yang)(yang)(yang)(yang)的(de)作(zuo)(zuo)(zuo)用(yong)，使顏色(se)(se)變(bian)暗。所以(yi)，除(chu)氧(yang)(yang)(yang)(yang)能有效地防止食(shi)品(pin)變(bian)質(zhi)(zhi)(zhi)(zhi)，保持其(qi)色(se)(se)、香、味及營(ying)養價值。