France in the late 1790s was at war and having difficulty feeding its people. Napoleon's fighting forces had a diet of putrid meat and other items of poor quality. The foods available couldn't be stored or transported except in a dry state. Recognizing an important problem prize was announced offering 12,OOO francs and fame to anyone inventing a useful method of food preservation.
 
    Nicolas Appert, a French confectioner. working in a simple kitchen. observed that food heated in. sealed containers was preserved if the container was not reopened or the seal did not leak. He modestly called the process "the art of Appertizing". Appert received the award from Napoleon after spending ten years proving his discovery.
 
 
    It should be appreciated that the cause of spoilage of food was unknown, The great scientists of the day were summoned to evaluate Appert’s process and offer explanations for its apparent success. The conclusion reached was that the process was successful because in some mysterious and magical fashion, air combined with food in a sealed container, preventing putrefaction. This was quite incorrect. Nevertheless, the canning process was discovered and practiced for the next 5O years with some success, but in the darkness of ignorance.
 
    Appert began work on his process in 1795. Peter Durand received patents in England in 1810 for glass and metal containers for packaging foods to be canned. The tin-plated metal containers were called "conisters" from which the term "can" is assumed to be derived. Early metal containers were bulky, crude and difficult to seal. By 1823 a can with a hole in the top was invented, allowing the food to be heated in boiling water baths with the hole covered with a loose lid. The lid was soldered into place after the heat treatment. Hole-in-top cans are in use presently for canned evaporated milk, although the cans are sealed prior to heating.

    By 1824 Appert had developed schedules for proessing some 50 different canned foods. Meats and stews processed by Appert were carried by Sir Edward Perry in 1824 in his search for a northwest passage to India. Several cans of food from this voyage were obtained from the National Maritime Museum in London in 1938 and opened. The food was found nontoxic for animals. Interestingly there were isolated from these canned products bacteria which had been dorman for at least 114 years. Given proper environment and substrate, they grow!
 
    In the 1820s canning plants appeared in the United States in Boston and
New York. By 1830 sweet corn was being processed in Maine. By 1840 canneries
began appearing throughout the United States.

    Temperature vs. Pressure

    In 1851 Chevalier-Appert invented an autoclave which lessened the danger involved in the operation of steam pressure vessels. It was recognized that some foods could be processed for shorter times if higher temperatures were available. It was learned that the temperature of boiling water could be increased by adding salt. Demands for greater production in factories could be met if the cooking times for foods could be reduced. For instance, the boiling water bath cooking of canned meats could be reduced from 6 hr to perhaps 1/2 hr by cooking the cans in a water-calcium chloride solution. Production could be increased thereby from some 2000 to 20,OOO cans per day. Losses due failure of containers were large. No pressure was applied to the cooking vessels. Commercial cans were unable to withstand the internal pressures developed by heating to 115℃.
 
    The temperature at which water will boil is dependent upon the pressure. Using a pressure pressure it was possible to achieve temperatures in the vicinity of 115℃. However, these retorts were still dangerous to operate.
 
    Spoilage of Food Caused by Microorganisms
     
    In 1862 President Lincoln signed the Morrill Act, creating the land grant colleges (Purdue, Michigan, Massachusetts, Illinois, etc. ). The great scientific debate in universities at that time was "spontaneous generation" of life. At this time Louis Pasteur, son of a well-decorated officer in Napoleon's army, became interested in the problems of the great wine and beer industries of France which were threatened with ruin; their products were diseased and souring from "spontaneous generation" of life in bottles and kegs.
 
    To the Academy of Sciences in France in 1864, Pasteur reported that be had found the cause of the disease of wine and beer to be a microscopic vegetation. When given favorable conditions this vegetation grew and spoiled the products. However, boiled wine sealed from contamination in jars with even cotton plugs would not sour. In fact, it was possible to isolate this microscopic vegetation from the cotton plugs! It was this microscopic growth which spoiled foods, and it was neccessary for such organisms to gain entrance to heated foods if they were to spoil! Here was an explanation for the success of Appert more than half a century before. The concept of heat treating foods to inactivate pathogenic organisms is termed appropriately "pasteurization" today.  It is interesting to note that magnifying lenses were used by Bacon in the late 1200s, but had never been focused on a drop of water until the 1600s by Leeuwenhoek. He had noted microscopic growth which he named "animalcules," but they were only a curiosity in water to him. Two more centuries elapsed before this information was organized and synthesized into an explanation for "spontaneous generation" of life.
 
    Appert had established that containers of food must be carefully sealed and heated. Cleanliness was important to his process, although he did not know that microorganisms were the agents of spoilage. Pasteur established several important principles. Most changes in wine depended on the development in it of microorganisms which were themselves the spirits of disease. Germs were brought by air, ingredients. machinery and even by people. Whenever wine contained no living organisms, the material remained undiseased.
 
    Heat Resistance of Microorganisms Important in Canning
 
    There are two important genera of bacteria which form spores. Both genera are rod forms, one (Bacillus) is aerobic and the other (Clostridium) is anaerobic. When a rod is about to sporulate a tiny refractile granule appears in the cell. The granule enlarges, becomes glassy and transparent, and resists the penetration of various chemical substances. All of the protoplasm of the rod seems to condense into the granule, or young spore. in a hard dehydrated, resistant state. The empty cell membrane of the bacterium may separate off, like the hull of a seed, leaving the spore as a free. round or oval body. Actually a spore is an end product of a series of enzymatic processes. There is no unanimity of opinion either of spore function in nature or of the factors concerned in spore formation.
 
    Since no multiplication take place as a result of the vegetative cell-spore-vegetative cell cycle, few bacteriologists accept the concept of the spore as a cell set apart for reproduction. Instead, various explanations of the biological nature and function of bacterial spores have been advanced. These include: the teleological interpretation of the spore as a resistant structure produced to enable the organism to survive an unfavorable environment; the idea that the spore is a normal resting state(a form of hibernation):the notion that spores are stages in
a development cycle of certain organisms, or a provision for the rearrangement of nuclear material. It is interesting to note that the protein of the vegetative cell and the protein of the spore are antigenically different.
 
    Spores appear to be formed by healthy cells facing starvation. Certain chemical agents (glutamic acid) may inhibit the development of spores. No doubt sporulation consists of a sequence of integrated biochemical reactions. The sequence can be interrupted at certain susceptible stages.
 
    The literature on the subject of the heat resistance ofbacteria contains many
contradictions and discrepancies from the records of the earliest works to those of
the present day. This lack of uniformity has been due in part to factors of unknown nature. Until the factors operative in the thermal resistance of bacteria are understood, it will not be possible to control by other than empirical means the processes which require for their success the destruction of bacteria.
 
    Heat may be applied in two ways for the destruction of bacteria. Oven heat may be considered as dry heat, used in the sterilization of glassware. Other materials are heated when moist or in the presence of moisture; this is commonly termed moist heat. Dry cells exhibit no life functions; their enzymes are not active. Cell protein does not coagulate in the absence of moisture.
 
    The gradual increase in the death rate of bacteria exposed to dry heat is
indicative of an oxidation process.
 
    Whereas death by dry heat is reported as an oxidative process. death by moist heat is thought to be due to the coagulation of the protein in the cell. The order of death by moist heat is logarithmic in nature. The explanation of bacteria death as caused by the inactivation of bacterial enzymes cannot be correct. A suspension containing 99% dead cells has 80% of its catalase active. Since the order of death by moist heat is logarithmic in nature, death must be brought about by the destruction of a single molecule. This change is termed a lethal mutation. To a food technologist, death of a bacterium is described by its inability to reproduce. Heat inactivates or coagulates a single mechanism (gene?) preventing reproduction. The decreasing enzyme content of dead bacteria is the consequence of inhibited growth and probably not the cause . Replacement of the enzyme molecules becomes impossible; the enzyme content slowly decreases.
 
    Regardless of the explanation of death of bacterial spores. the logarithmic
order of this death permits the computation of death points, rates or times. independent of any explanation. The death rates or times permit the comparison of the heat resistance of one .species at different temperatures or of different species at the same temperatures. It is also possible to describe in quantitative terms the effect of environmental factors upon the heat resistance of the bacteria.
 
    Originally the standard method of establishing the heat tolerance of different species of bacteria was the thermal death point,i.e. , the lowest temperature at which the organism is killed in 10 min. This method cannot give comparable results unless conditions such as the age of the culture, the concentration of cells, the pH value of the medium, and the incubation temperature are standardized. Food technologists concerned with processing canned foods have adopted the thermal death time, keeping the temperature constant and varying the times of heating. The thermal death time is the shortest time required at a given. temperature to kill the bacteria present. It is necessary to know the time and temperature required to adequately sterilize canned foods. This procedure involves not only the destruction of spores by moist heat, but also the rate of heat penetration and heat conductivity of containers and their contents. The heat resistance of an organism is designated. by the c value(the number of minutes required to destroy the organism at 121℃) and the z value (the numbre of degree centigrade required for the thermal death time curve to traverse one logarithmic cycle). These two valuse establish and describe the thermal death time curve. and are a quantitative measure of the heat resistance of the spores over a range of temperatures. 
 
    It has been recognized that spores of different species, and of strains of the
same species, exhibit marked differences in heat resistance, but little or nothing
is know in explanation. Some workers have believed that there might be a difference in heat resistance among the vegetative cells, which was transmitted to the spores. Comparing the beat resistance of vegetative cells and spores of a number of bacteria, considerable differences in the spore resistances are found among organisms. Differences in vegetative cell heat resistance is in some instances associated with high spore resistance. Other cultures of vegetative cells produce spores of low resistance. There is evidently no significant relationship between the heat resistance of the vegetative cell and that of the spore produced therefrom. As noted previously, even the protein of the vegetative cell and
 
   spore differ for a species.

     Some researchers reason that the spores of a strain are all of the same heat resistance. Others suspect that in a given spore suspension there are a predominant number of spores of relatively low heat resistance, a smaller number with greater heat resistance, and a still smaller number of very heat resistant spores. However, subcultures from heat resistant selections do not yield survivors  of uniformly high heat resistance over the parent strain.

    Factors Influencing The Heat Resistance of Spores
 
    Concentration. The heat resistance of a suspension of bacterial spores is related to the number of organisms present. The greater the number of spores per milliliter, the higher resistance of the suspension.
 
    Environment Factors. The resistance of bacterial spores is not a fixed property,but one which under ordinary conditions may tend to be relatively constant. The extent of change in resistance is determined largely by the physical and chemical forces which operate from outside the spore cell. Aside from purely theoretical interest, a better understanding of the cause of heat resistance of spores is of fundamental importance to the canning industry. There are relatively few types of spore-forming organisms especially endowed with heat resistant properties, but these account for most of the spoilage potential in canning. Spore heredity. the environment in which grow, and a combination of these factors must play some part in the production of highly heat resistant spores .
 
    Different yields of spore crops can be determined in various media. This may be demonstrated by plate count or by direct microscopic count. There is little information indicating a relationship between the physiological factors influencing spore formation and the heat resistance of spores produced. The reaction (pH value) of the medium in which spores are produced has appearently little influence on their heat resistance. 
 
    Continuous drying seems to enhance the resistance of spores, but this is irregular in effect. Freezing tends to weaken spores. The following data for an aerobic spare-forming organism isolated from spoiled canned milk is noteworthy
 
   (Curran 1935):
                                Heat Resistance at 121℃
     Spore Treatment                          Survival in Minutes
     Wetted                                                    5
     Alternately wetted and dried               6
     Dried                                                       7
     Frozen                                                     2
 
    Spores formed and aged in soil are found to be more heat resistant than those formed and aged in broth or agar. Natural environmental conditions are evidently more conducive to the development of heat resistant spores than conditions prevailing in artificial cultures. The prolonged action of metabolic wastes from cells appears to decrease the heat resistance of spores.
 
    Bacteria exposed to sublethal heat are more exacting in their nutrient and temperature requirements than undamaged bacteria. The composition of recovery media which organisms are placed after heating may have considerable effect on the apparent thermal destruction time of the organisms. Depending on the choice of media, heat treated bacteria may be found to be dead in one and alive in another.
 
    Thermophilic bacteria which from spores in artificial media. produce spores
of comparable heat resistance to those formed on equipment and machinery in canning plants.
 
    Spores obtained from soil extractions and remixed with sterile soil are less heat resistant than those heated in the soil directly. The higher natural resistance of spores in soil may be due to some physico-chemical influence of the soil and not to any differences between the soil and cultured spores themselves.
 
    Anthrax spores remain viable and virulent in naturally contaminated water for as many as 18 years. while artificial cultures remain in this condition for perhaps 5 months. Soil organisms on corn may remain viable on naturally contaminated tissue for at least 7 years. while the artificially cultured die in 3 months. Artificial media apparently weakens cultures of organisms If a culture is to be kept alive for a long period it is apparently desirable to have a medium which permits only a limited growth. limiting metabolic byproducts, than media which permit best growth. B. tuberculosis growing on a relatively poor medium may be kept viable for several years while growth on enriched media has viable organisms for only a few weeks. The preserving influence of natural environments may be a similar phenomena.

    18世紀90年代末,法國處於戰爭時期,國民的食物供應發生了困難.拿破侖部隊吃的是腐敗的肉和其他劣質食物.這些可供利用的食物除幹態的外,都不可能進行儲藏或運輸.認識到這一嚴重問題之後,就宣告了一項獎金,將給予任何發明食物有效保藏方法的個人以12,000法郎和榮譽.

    一位工作在簡陋廚房中的法國糖食師傅尼古拉·阿培爾發現：在密封容器中加熱過的食物，如果不重新打開容器或密封不漏，它便被保存下來。他謙虛地把這種處理方法稱為“阿培爾技藝“。阿培爾在花了10年確認他的發明之後，才從拿破侖那裏拿到這項獎賞。

    yaozhidao

，nashibingbumingbaishipinbianzhidedaoli。yushizhaojiledangshidedakexuejia
，duiepeierdechulifangfajinxinglepingjia，bingduizhezhongfangfademingxianchenggongzuochujieshi。dedaodejielunshi：這(zhe)種(zhong)處(chu)理(li)方(fang)法(fa)之(zhi)所(suo)以(yi)成(cheng)功(gong)
，原(yuan)因(yin)是(shi)在(zai)密(mi)封(feng)的(de)容(rong)器(qi)內(nei)
，空(kong)氣(qi)以(yi)某(mou)種(zhong)神(shen)秘(mi)難(nan)測(ce)的(de)方(fang)式(shi)於(yu)食(shi)物(wu)相(xiang)結(jie)合(he)，防(fang)止(zhi)了(le)食(shi)物(wu)的(de)腐(fu)敗(bai)。這(zhe)當(dang)然(ran)不(bu)正(zheng)確(que)。盡(jin)管(guan)這(zhe)樣(yang)，這(zhe)種(zhong)罐(guan)藏(zang)工(gong)藝(yi)終(zhong)於(yu)被(bei)發(fa)現(xian)了(le)，並(bing)經(jing)過(guo)了(le)那(na)時(shi)以(yi)後(hou)50年的實踐，取得了一定程度的成功，但還是處在無知的黑暗之中。

    阿培爾於1795年在他所提出的工藝方麵開始工作。1810年彼特·杜蘭德在英國獲得用於包裝罐頭食物的玻璃容器和金屬容器專利。人們過去稱鍍錫鋼板的容器為“canister”(金屬罐）現在“can”這一用語被認為是從canister派生出來的詞。早期的金屬容器笨重、粗陋且難以封口。到1823年nian，發fa明ming了le一yi種zhong頂ding上shang帶dai小xiao孔kong的de金jin屬shu罐guan
，用yong不bu緊jin密mi的de蓋gai子zi封feng住zhu小xiao孔kong，同tong時shi讓rang食shi物wu在zai沸fei水shui浴yu中zhong加jia熱re。熱re處chu理li之zhi後hou
，將jiang蓋gai子zi就jiu原yuan位wei焊han牢lao。這zhe種zhong孔kong蓋gai式shi金jin屬shu罐guan目mu前qian仍reng用yong於yu淡dan煉lian奶nai罐guan頭tou，隻zhi不bu過guo這zhe種zhong鐵tie罐guan是shi在zai加jia熱re之zhi前qian密mi封feng的de。

    到1824年，阿培爾已經製定了加工約50多種不同罐頭食品的作業計劃。經阿培爾處理的肉類和燉菜由埃德華·彼裏爵士於1824年他探索通往印度西北航道是帶去。1838nian
，renmenconglundundeguolihaishibowuguandedaolejiguanlaizizhecihangxingdeguantoushipin，bingjiangzhexieguantoudakai。faxianzhexieshiwuduidongwuwudu。youqudeshi，congzhexieguanshipinzhongfenlichuyixiexijun，tamenyizhishaoxiumianle114年。給以適當的環境和基質後，它們又生長了!

    19世紀20年代末在美國的波士頓和紐約出現了罐頭製造廠。1830年，緬因州開始加工甜玉米。到1840年，罐頭食品廠開始在美國到處出現。

    溫度和壓力

    1851年，查弗利爾—阿(e)培(pei)爾(er)創(chuang)製(zhi)了(le)一(yi)種(zhong)高(gao)壓(ya)鍋(guo)，它(ta)可(ke)以(yi)減(jian)少(shao)汽(qi)壓(ya)容(rong)器(qi)操(cao)作(zuo)中(zhong)所(suo)涉(she)及(ji)的(de)危(wei)險(xian)。人(ren)們(men)早(zao)就(jiu)知(zhi)道(dao)，如(ru)果(guo)更(geng)高(gao)的(de)溫(wen)度(du)能(neng)辦(ban)到(dao)
，有(you)些(xie)食(shi)品(pin)的(de)熱(re)處(chu)理(li)時(shi)間(jian)就(jiu)可(ke)以(yi)縮(suo)短(duan)。人(ren)們(men)也(ye)知(zhi)道(dao)：用(yong)加(jia)鹽(yan)的(de)方(fang)法(fa)可(ke)提(ti)高(gao)沸(fei)水(shui)的(de)溫(wen)度(du)。如(ru)果(guo)能(neng)減(jian)少(shao)食(shi)品(pin)的(de)熱(re)處(chu)理(li)時(shi)間(jian)

，那(na)麼(me)工(gong)廠(chang)提(ti)高(gao)產(chan)量(liang)的(de)要(yao)求(qiu)就(jiu)能(neng)夠(gou)得(de)到(dao)滿(man)足(zu)。例(li)如(ru)，可(ke)以(yi)把(ba)肉(rou)類(lei)罐(guan)頭(tou)的(de)沸(fei)水(shui)浴(yu)熱(re)處(chu)理(li)時(shi)間(jian)從(cong)6小時縮短到用氯化鈣水溶液熱處理時的0.5小時左右，從而可使產量大體從每天2000罐增加到20000罐。容器損壞所造成的損失是大的。因為對熱處理的容器不加壓
，所以商業金屬罐也就不能耐受因加熱到115℃而產生的內壓。

    水沸騰時的溫度取決於壓力。使用壓力容器就可以達到115℃左右的溫度。雖如此，這類高壓殺菌鍋的操作仍有危險。

    微生物引起的食品腐敗

    1862年，林肯總統簽署了莫裏爾法令，創辦了幾所政府贈地的高等學校（如普多、密歇根、馬薩諸塞、伊利諾斯等）。那時大學裏科學辯論的重大課題是生命的“自發生說”。此時，拿破侖軍隊裏一位功勳顯赫的軍官的兒子路易·巴斯德開始對法國巨大的葡萄酒和啤酒工業麵臨毀滅危險這一問題產生了興趣，這些工業的產品由於酒瓶和酒桶裏的生命“自發生”問題而得了毛病，正在變酸。

    1864nian，basidexiangfaguokexueyuantichubaogaoshuo，tayifaxianledaozhiputaojiuhepijiubianhuaideyuanyinshimouzhongweixiaoyingyangtizaochengde。zhiyaogeiyuyoulidetiaojian，zhezhongyingyangtibianshengchang，shichanpinfubai。danzhufeihoudepingzhuangputaojiu
，jishicaiyongnapashimianhuasaimifengyigejuewuran，yebuhuibiansuan。deque
，yongmianhuasaigelizhezhongweixiaoyingyangtishikenengde！正是這些微小的生長物造成了食品的腐壞！這些生物體若要腐壞加熱過的食品
，它就得進入食品！以上就是50多年前阿培爾的成功的一種解釋。今天人們把這種對食品進行熱處理使致病生物體失活的概念恰當地稱為“巴氏滅菌”。

    有趣的是我們注意到，雖然培根在13世紀末期就使用放大鏡了，但直到17世紀才由列文虎克將放大鏡對準一滴水。列文虎克發現了稱之為“微小物”的微小生長物,不過對他來說
，這些微動物隻不過是水中稀奇的東西罷了。經過兩個多世紀之後
，這一知識被條理化了
，被綜合成為對生命“自發生說”的一種解釋。

    阿培爾肯定：shipinrongqibixuyangemifenghejiare。qingjieduitadegongyifangfahenzhongyao，buguotabingbuzhidaoweishengwushifubaidemeijie。basidequelileyixiezhongyaodeyuanze。putaojiudexuduobianhuaqujueyuweishengwuzaiqizhongdeshengchang，erweishengwubenshenzeshiputaojiuchuwentideshizhi。shengmingdepeiyashiyoukongqi、配料

、機器甚至人帶來的。隻要酒中不含活的生物體，此物一定可保持不變質。

    罐頭製造中重要微生物的耐熱性 

    形成芽孢的細菌主要有兩屬。這兩屬都是杆狀菌。一屬（芽孢杆菌屬）是需氧的，另一屬（梭狀芽孢杆菌屬）是shi厭yan氧yang的de。當dang一yi個ge杆gan菌jun即ji將jiang形xing成cheng芽ya孢bao時shi，細xi胞bao內nei便bian出chu現xian一yi粒li帶dai折zhe射she性xing的de微wei小xiao顆ke粒li。這zhe顆ke粒li逐zhu漸jian擴kuo大da，變bian成cheng玻bo璃li狀zhuang透tou明ming，並bing能neng抵di抗kang多duo種zhong化hua學xue物wu質zhi的de侵qin入ru。杆gan菌jun中zhong的de所suo有you原yuan生sheng質zhi似si乎hu都dou凝ning聚ju到dao此ci顆ke粒li（即幼芽孢）中zhong，使shi之zhi處chu於yu一yi種zhong幹gan硬ying而er有you抵di抗kang力li的de狀zhuang態tai。此ci細xi菌jun的de空kong細xi胞bao膜mo象xiang種zhong子zi殼ke一yi樣yang可ke被bei分fen離li掉diao
，留liu下xia呈cheng圓yuan形xing或huo蛋dan形xing散san粒li物wu的de芽ya孢bao。實shi際ji上shang一yi個ge芽ya孢bao是shi一yi係xi列lie酶mei促cu過guo程cheng的de最zui終zhong產chan物wu。不bu論lun關guan於yu芽ya孢bao在zai自zi然ran界jie中zhong的de作zuo用yong，或huo有you關guan芽ya孢bao形xing成cheng的de原yuan因yin，都dou沒mei有you一yi致zhi的de看kan法fa。

    因為“營養細胞—芽孢—營養細胞”xunhuandejieguobuchanshengzengzhizuoyong，suoyijihumeiyouxijunxuejiarenweiyabaoshiyizhongfenkailaigongfanzhiyongdexibao。xiangfan，duixijunyabaodeshengwuxuebenzhihegongnengquetichuleduozhongjieshi。zhexiejieshibaokuo：有關芽孢是一種正常休眠狀態（一種蟄伏狀態）的看法;有you關guan芽ya孢bao是shi某mou些xie生sheng物wu體ti生sheng長chang循xun環huan中zhong的de一yi個ge階jie段duan，即ji為wei重zhong新xin調tiao整zheng細xi胞bao核he物wu質zhi作zuo準zhun備bei的de意yi見jian。有you趣qu的de是shi我wo們men注zhu意yi到dao，營ying養yang細xi胞bao蛋dan白bai質zhi與yu芽ya孢bao蛋dan白bai質zhi在zai抗kang原yuan上shang是shi不bu同tong的de。

    健康細胞麵臨饑餓時就要形成芽孢。某些化學物質（穀氨酸）可以抑製芽孢的發育。無疑芽孢的形成包括一係列完整的生物化學反應。這一係列反應在某些易受外界影響的階段可能被中斷。

    youguanxijundenairexingwentidewenxianzhongzaiyoucongzaoqigongzuozheziliaodaomuqianziliaozhongdexuduomaodunhefenqidedifang。zhezhongbuyizhidebufenyuanyinshibenzhiweimingdeyinsuzaochengde。yaodengdaozhexieduixijunnairexingqizuoyongdeyinsubeirenmenrenshizhihou，renmencainengyongjingyanfangfayiwaidefangfalaichenggongdikongzhishajunguocheng。

    為了殺滅細菌，加熱方法可以有兩種。烘爐的熱可認為是幹熱
，用於玻璃器皿的滅菌。其他物料是在潮濕（即有水份存在）的時候加熱的，就是通常說的濕熱。幹的細胞不顯現生命功能，其酶係統無活性。細胞蛋白質在沒有水份存在的情況下不凝固。

    暴露在幹熱狀態下的細菌，其死亡率的逐漸上升是某種氧化過程的表現。

    盡(jin)管(guan)據(ju)報(bao)道(dao)幹(gan)熱(re)致(zhi)死(si)是(shi)一(yi)種(zhong)氧(yang)化(hua)過(guo)程(cheng)，但(dan)一(yi)般(ban)認(ren)為(wei)濕(shi)熱(re)致(zhi)死(si)則(ze)是(shi)由(you)細(xi)胞(bao)中(zhong)蛋(dan)白(bai)質(zhi)凝(ning)固(gu)造(zao)成(cheng)的(de)。濕(shi)熱(re)致(zhi)死(si)的(de)量(liang)級(ji)本(ben)質(zhi)上(shang)是(shi)對(dui)數(shu)性(xing)的(de)。把(ba)細(xi)菌(jun)死(si)亡(wang)解(jie)釋(shi)為(wei)由(you)細(xi)菌(jun)酶(mei)鈍(dun)化(hua)引(yin)起(qi)是(shi)不(bu)正(zheng)確(que)的(de)。某(mou)種(zhong)含(han)99％死細胞的懸浮液，其中過氧化氫酶有80％是shi有you活huo性xing的de。由you於yu濕shi熱re至zhi死si的de量liang級ji是shi對dui數shu的de，所suo以yi死si亡wang的de發fa生sheng必bi定ding按an單dan個ge微wei粒li一yi一yi死si亡wang的de方fang式shi。這zhe種zhong變bian化hua稱cheng為wei致zhi死si突tu變bian。對dui食shi品pin工gong藝yi學xue家jia來lai說shuo


，細xi菌jun的de死si亡wang被bei說shuo成cheng是shi無wu力li繁fan殖zhi。熱re使shi某mou種zhong簡jian單dan的de機ji製zhi（基因？）不(bu)起(qi)作(zuo)用(yong)或(huo)凝(ning)住(zhu)，從(cong)而(er)不(bu)使(shi)細(xi)菌(jun)再(zai)生(sheng)繁(fan)殖(zhi)。死(si)亡(wang)細(xi)菌(jun)酶(mei)含(han)量(liang)不(bu)斷(duan)減(jian)少(shao)是(shi)生(sheng)長(chang)受(shou)抑(yi)製(zhi)的(de)結(jie)果(guo)，可(ke)能(neng)不(bu)是(shi)生(sheng)長(chang)受(shou)抑(yi)製(zhi)的(de)原(yuan)因(yin)。酶(mei)分(fen)子(zi)的(de)補(bu)充(chong)成(cheng)為(wei)不(bu)可(ke)能(neng)
，故(gu)酶(mei)含(han)量(liang)慢(man)慢(man)地(di)減(jian)少(shao)。

    不論對細菌芽孢死亡的解釋如何，芽孢死亡的對數量級使致死溫度、zhisilvhezhisishijiandejisuanchengweikeneng，eryurenhejieshiwuguan。zhisilvhuozhisishijianshitongyijunzhongbutongwenduxiahuobutongjunzhongzaitongyiwenduxiadenairexingyoukenengjinxingbijiao。tongshi，haiyoukenengyidingliangfangshimiaoshuhuanjingyinsuduixijunnairexingdeyingxiang。

    最初，確定不同菌種的耐熱性的標準方法是熱死溫度法，即這種生物體在10分鍾內被殺死的最低溫度。此法不能得出可比的結果
，除非象菌種齡期、細胞濃度、培養基pH值和培養溫度都是統一規定的。關心罐頭食品加工的食品工業學家卻采用了熱死時間法，即保持溫度不變、改變加熱時間的方法。熱死時間使在給定溫度下殺滅現存細菌所需的最短時間。

    youbiyaozhidaoguantoushipinchongfenmiejunsuoxuyaodeshijianhewendu。zheyibuzhoubujinshejiyongshirefashamieyabao
，yeshejidaochuanresulvherongqijiqineirongwurechuandaolv。shengwutidenairexingyouC值（在120℃下殺滅此生物體所需的分鍾數）和E值（沿熱死時間曲線移動一個對數周期所需的攝氏度數）表示。這兩個值確定並描繪了熱致死時間曲線，是芽孢在一定溫度範圍內耐熱性的定量的量度。

    人們已經認識到：不(bu)同(tong)菌(jun)種(zhong)芽(ya)孢(bao)和(he)同(tong)菌(jun)種(zhong)不(bu)同(tong)菌(jun)株(zhu)的(de)芽(ya)孢(bao)，都(dou)表(biao)現(xian)出(chu)明(ming)顯(xian)不(bu)同(tong)的(de)耐(nai)熱(re)性(xing)，但(dan)幾(ji)乎(hu)不(bu)知(zhi)道(dao)如(ru)何(he)解(jie)釋(shi)。有(you)些(xie)工(gong)作(zuo)者(zhe)認(ren)為(wei)，營(ying)養(yang)細(xi)胞(bao)之(zhi)間(jian)也(ye)會(hui)在(zai)耐(nai)熱(re)性(xing)下(xia)有(you)一(yi)定(ding)差(cha)異(yi)，此(ci)差(cha)異(yi)傳(chuan)給(gei)了(le)芽(ya)孢(bao)。比(bi)較(jiao)許(xu)多(duo)細(xi)菌(jun)的(de)營(ying)養(yang)細(xi)胞(bao)和(he)芽(ya)孢(bao)的(de)耐(nai)熱(re)性(xing)後(hou)發(fa)現(xian)生(sheng)物(wu)體(ti)中(zhong)間(jian)在(zai)芽(ya)孢(bao)耐(nai)熱(re)性(xing)上(shang)有(you)顯(xian)著(zhu)差(cha)異(yi)。有(you)的(de)情(qing)況(kuang)營(ying)養(yang)細(xi)胞(bao)耐(nai)熱(re)性(xing)差(cha)異(yi)與(yu)芽(ya)孢(bao)耐(nai)熱(re)性(xing)強(qiang)有(you)聯(lian)係(xi)。也(ye)有(you)一(yi)些(xie)營(ying)養(yang)細(xi)胞(bao)的(de)培(pei)養(yang)物(wu)產(chan)生(sheng)耐(nai)熱(re)性(xing)弱(ruo)的(de)芽(ya)孢(bao)。顯(xian)然(ran)，營(ying)養(yang)細(xi)胞(bao)耐(nai)熱(re)性(xing)和(he)由(you)營(ying)養(yang)細(xi)胞(bao)產(chan)生(sheng)的(de)芽(ya)孢(bao)的(de)耐(nai)熱(re)性(xing)之(zhi)間(jian)沒(mei)有(you)明(ming)顯(xian)的(de)聯(lian)係(xi)。如(ru)以(yi)前(qian)所(suo)指(zhi)出(chu)的(de)
，即(ji)使(shi)同(tong)一(yi)菌(jun)種(zhong)的(de)營(ying)養(yang)細(xi)胞(bao)和(he)芽(ya)孢(bao)中(zhong)的(de)蛋(dan)白(bai)質(zhi)也(ye)不(bu)同(tong)。

    一些研究者推論：同菌株芽孢的耐熱性都是相同的。但另外一些人認為：在給定的芽孢懸浮液中，耐熱性弱的芽孢的數目占有優勢;耐熱性愈強，數目愈少;耐熱性最強的，數就更少。然而

，從耐熱性選育得到的次代培養物不產生比親株均勻耐熱性更強的存活者。

    影響芽孢耐熱性的因素 

    濃度——細胞懸浮液的耐熱性於現存生物體的數量有關。每毫升中芽孢數越多，懸浮液耐熱性越強。

    環境因素——細xi胞bao芽ya孢bao的de耐nai熱re性xing不bu是shi一yi種zhong固gu定ding不bu變bian的de性xing質zhi，而er是shi一yi種zhong在zai一yi般ban條tiao件jian下xia趡趡於yu相xiang對dui恒heng定ding的de選xuan擇ze。耐nai熱re性xing變bian化hua的de幅fu度du主zhu要yao取qu決jue於yu受shou芽ya孢bao細xi胞bao外wai部bu影ying響xiang的de物wu理li力li和he化hua學xue力li。對dui於yu罐guan頭tou製zhi造zao工gong業ye來lai說shuo
，除chu了le純chun理li論lun的de興xing趣qu外wai，更geng深shen入ru了le解jie芽ya孢bao耐nai熱re性xing的de起qi因yin使shi十shi分fen重zhong要yao的de事shi情qing。隻zhi有you比bi較jiao少shao數shu的de幾ji種zhong產chan芽ya孢bao微wei生sheng物wu特te別bie賦fu有you耐nai熱re特te性xing，而er這zhe種zhong微wei生sheng物wu則ze是shi造zao成cheng罐guan頭tou製zhi造zao上shang大da多duo數shu潛qian在zai腐fu敗bai的de主zhu要yao原yuan因yin。芽ya孢bao的de遺yi傳chuan性xing、它生長所在的環境
、以及這些因素的綜合都必然在強耐熱性芽孢的產生方麵有一定作用。

    我wo們men能neng夠gou測ce定ding各ge種zhong培pei養yang基ji中zhong芽ya孢bao培pei養yang物wu的de不bu同tong收shou得de量liang。這zhe可ke由you平ping板ban計ji數shu或huo直zhi接jie顯xian微wei鏡jing計ji數shu來lai顯xian示shi。幾ji乎hu沒mei有you什shen麼me測ce定ding數shu據ju能neng說shuo明ming影ying響xiang芽ya孢bao形xing成cheng的de生sheng理li因yin素su與yu產chan生sheng的de芽ya孢bao的de耐nai熱re性xing之zhi間jian的de關guan係xi。產chan芽ya孢bao的de培pei養yang基ji的de作zuo用yong（pH值）很明顯不影響芽孢的耐熱性。

    chixudeganzaosihuzengqiangleyabaodenaixing，danzheshijishangmeiyoushenmeguilv。lengdong趡yushiyabaonairexingjianruo。xiamianshicongfubainiunaiguantouzhongfenlichulaidexuyangchanyabaojundeshuliang，zhidewomenzhuyi（柯倫，1935年）：

    121℃時的耐熱性
    芽孢處理法                           存活時間（min）
    潮濕                                        5
    幹
、濕交替處理                    6
    幹燥                                        7         
    冷凍                                        2
 
    womenfaxianzaiturangzhongxingchenghechengshudeyabaobizairoutanghuoqiongzhizhongxingchenghechengshudeyabaoyougengqiangdenairexing。xianran，ziranhuanjingtiaojianbichangjianrengongpeiyangtiaojiangengyouzhuyunaireyabaodefayu。kanlailaizixibaoxinchendaixiefeiwudechangshijianzuoyonghuishiyabaodenairexingjianruo。

    受(shou)亞(ya)致(zhi)死(si)熱(re)量(liang)作(zuo)用(yong)的(de)芽(ya)孢(bao)比(bi)未(wei)受(shou)損(sun)害(hai)的(de)芽(ya)孢(bao)有(you)更(geng)加(jia)嚴(yan)格(ge)的(de)營(ying)養(yang)要(yao)求(qiu)和(he)溫(wen)度(du)要(yao)求(qiu)。對(dui)於(yu)經(jing)加(jia)熱(re)之(zhi)後(hou)接(jie)入(ru)微(wei)生(sheng)物(wu)的(de)回(hui)收(shou)培(pei)養(yang)基(ji)，它(ta)的(de)組(zu)成(cheng)對(dui)該(gai)微(wei)生(sheng)物(wu)的(de)表(biao)現(xian)熱(re)致(zhi)死(si)時(shi)間(jian)會(hui)有(you)明(ming)顯(xian)的(de)影(ying)響(xiang)。根(gen)據(ju)選(xuan)用(yong)培(pei)養(yang)基(ji)的(de)不(bu)同(tong)，可(ke)以(yi)發(fa)現(xian)熱(re)處(chu)理(li)後(hou)的(de)細(xi)菌(jun)在(zai)一(yi)種(zhong)培(pei)養(yang)基(ji)裏(li)死(si)亡(wang)，而(er)在(zai)另(ling)一(yi)種(zhong)培(pei)養(yang)基(ji)裏(li)存(cun)活(huo)。

    在人工培養基中形成芽孢的嗜熱細菌

，它產生的芽孢於在罐頭工廠機器設備上形成的芽孢，在耐熱性上差不多。

    從cong土tu壤rang分fen離li出chu來lai再zai混hun以yi無wu菌jun泥ni土tu的de芽ya孢bao
，其qi耐nai熱re性xing比bi直zhi接jie在zai土tu壤rang中zhong加jia熱re的de芽ya孢bao弱ruo。土tu壤rang中zhong芽ya孢bao的de天tian然ran耐nai熱re性xing較jiao強qiang可ke能neng是shi由you於yu土tu壤rang的de某mou些xie物wu理li化hua學xue影ying響xiang造zao成cheng的de。而er不bu是shi土tu壤rang芽ya孢bao與yu人ren工gong培pei養yang芽ya孢bao本ben身shen之zhi間jian的de什shen麼me差cha異yi造zao成cheng的de。

    炭菹菌芽孢在天然汙染的水中保持活性和毒性長達18年，而人工培養物則保持此狀態約5個月。玉米上的土壤微生物在天然汙染的生物組織上至少可以存活7年，而人工培養的則在3個月內就死亡。顯然人工培養的微生物的活性減弱。

    如(ru)果(guo)要(yao)長(chang)期(qi)保(bao)持(chi)培(pei)養(yang)物(wu)的(de)活(huo)力(li)，顯(xian)然(ran)就(jiu)要(yao)有(you)一(yi)種(zhong)隻(zhi)許(xu)有(you)限(xian)生(sheng)長(chang)的(de)培(pei)養(yang)基(ji)，來(lai)限(xian)製(zhi)新(xin)陳(chen)代(dai)謝(xie)的(de)副(fu)產(chan)物(wu)

，而(er)不(bu)要(yao)那(na)些(xie)允(yun)許(xu)旺(wang)盛(sheng)生(sheng)長(chang)的(de)培(pei)養(yang)基(ji)。生(sheng)長(chang)在(zai)相(xiang)對(dui)劣(lie)質(zhi)培(pei)養(yang)基(ji)中(zhong)的(de)結(jie)核(he)杆(gan)菌(jun)可(ke)以(yi)存(cun)活(huo)好(hao)幾(ji)年(nian)，而(er)在(zai)營(ying)養(yang)豐(feng)富(fu)培(pei)養(yang)基(ji)中(zhong)生(sheng)長(chang)時(shi)，僅(jin)存(cun)活(huo)幾(ji)周(zhou)。天(tian)然(ran)環(huan)境(jing)的(de)防(fang)腐(fu)作(zuo)用(yong)大(da)概(gai)也(ye)是(shi)一(yi)種(zhong)類(lei)似(si)的(de)現(xian)象(xiang)。