PasteurizationPasteurization, named after its inventor FrancebiologistLouis Pasteur.In 1862, Pasteur invented a disinfection method that can kill bacteria in milk without affecting the taste of milk, namely pasteurization[1]。
The French beer industry is very famous in Europe, but the beer often turns sour. The whole barrel of aromatic and delicious beer turns into sour mucus and has to be poured out, which makes the brewers complain incessantly and some even go bankrupt.In 1865, the owner of a brewery in Lille asked Pasteur to help cure the disease of beer and see if a chemical could be added to prevent the beer from turning sour[3]。
Pasteur agreed to study this problem. He observed under a microscope and found that there was a round yeast cell in the liquid of the old wine and beer that had not deteriorated. When the wine and beer became sour, there were thin sticks in the liquidLactobacillusThey breed in nutritious beer and make beer "sick".He put the closed wine bottle in a wire basket, soaked it in water and heated it to different temperatures, trying to kill lactobacilli without boiling the beer. After repeated experiments, he finally found a simple and effective method: as long as the wine is kept at 50 or 60 degrees Celsius for half an hour, it can kill lactobacilli in the wine, which is famous“Pasteurization”This method is still in use today, and the sterilized milk sold on the market is sterilized by this method[3]。
At that time, the owner of the brewery did not believe Pasteur's method. Pasteur was not worried. He heated some samples and did not heat others. He told the owner to stay patiently for several months. As a result, after opening the heated samples, the wine tasted pure, while the unheated ones were already sour[3]。
Main principles
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In a certain temperature range, the lower the temperature, the slower the bacteria reproduction;The higher the temperature, the faster the reproduction.But if the temperature is too high, the bacteria will die.Different bacteria have different optimum growth temperature and heat and cold tolerance.In fact, pasteurization is to take advantage of the fact that pathogens are not very heat-resistant and treat them with appropriate temperature and holding time to kill them all.However, after pasteurization, a small number of harmless or beneficial, heat-resistant bacteria orBacterial sporeTherefore, pasteurized milk should be stored at about 4 ℃, and can only be stored for 3-10 days, up to 16 days[2]。
Operation method
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At present, there are two commonly used pasteurization methods in the world: the first method is to heat the milk to 62 ℃ - 65 ℃ for 30 minutes.This method can kill various growth pathogenic bacteria in milk, and the sterilization efficiency can reach 97.3% - 99.9%. After disinfection, only some thermophilic bacteria, heat-resistant bacteria and spores remain, but most of these bacteria are lactic acid bacteria, which are not only harmless but also beneficial to human health;The second method is to heat the milk to 75 ℃ - 90 ℃ for 15s - 16s, which has shorter sterilization time and higher efficiency.But the basic principle of sterilization is to kill the pathogenic bacteria. If the temperature is too high, more nutrition will be lost[2]。
Main applications
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Pasteurization is mainly a kind of sterilization method for milk, which can not only kill pathogenic bacteria harmful to health, but also minimize changes in milk quality.PasteurizationIt is impossible to kill all bacteria. It can only reduce the number of pathogenic bacteria to a level that will not cause harm to consumers.In addition to milk, pasteurization can also be applied to fermented products[2]。
Pasteur
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louis pasteur (Louis Pasteur) (1821-1895.9.25) French microbiologist, chemist and founder of modern microbiology.imageNewtonLike classical mechanics, Pasteur opened up the field of microbiology, created a set of unique basic research methods of microbiology, and began to study with the method of "practice theory practice". He is also a scientific giant[4]。
Pasteur
Personal achievements
Pasteur has carried out a number of exploratory research throughout his life and has made significant achievements. He is one of the most accomplished scientists in the 19th century.He spent his whole life proving four scientific problems: (1) Every fermentation is due to the development of a microbe. The French chemist found that heating can kill those annoying microorganisms that make wine sour.Soon“Pasteurization”It is applied to various foods and drinks.(2) Every infectious disease is the development of a microbe in the organism: Pasteur saved the French silk industry by discovering and eradicating a bacterium that infringes on silkworm eggs.(3) Microbacteria of infectious diseases can reduce their virulence under special cultivation, making them become disease prevention vaccines from germs.He realized that many diseases were caused by microorganisms, so he established the theory of bacteria.(4) The ingenious invention of the flask and the bacterial test proved that it was not produced by corrupt objects, but by bacteria, which broke the long-standing view of Newton and others[4]。
Louis Pasteur is praised by the world as "the most perfect person entering the kingdom of science". He is not only a theoretical genius, but also a person who is good at solving practical problems.He published two papers in 1843 -“BicrystalPhenomenon research "and" crystal morphology "initiated the research on optical properties of substances.From 1856 to 1860, he proposedMicrobial metabolismActivity based new theory on the nature of fermentation, "AboutLactic acid fermentation"Is recognized as a classic paper in microbiology.It was successfully developed after 1880fowl choleraVaccine, rabies vaccine and other vaccines, their theories and immunization methods have caused major changes in medical practice.In addition, Pasteur's work has also successfully saved France's wine industry, sericulture and animal husbandry in distress[4]。
Medical contribution
Pasteur is regarded as the most important outstanding person in the history of medicine.Pasteur's contribution involves several disciplines, but his reputation focuses on defending and supporting germs and developing vaccines to prevent diseases[4]。
Pasteur was not the earliest discoverer of germs.Before him, Kirula, Bao Henry and others had proposed similar assumptions.However, Pasteur not only enthusiastically and bravely put forward his theory on bacteria, but also proved the correctness of his theory through a large number of experiments, which convinced the scientific community. This is his main contribution[4]。
Obviously, the cause lies in bacteria. It is obvious that only by preventing bacteria from entering the human body can we avoid getting sick.Therefore, Pasteur stressed that doctors should use disinfection.Joseph Sinster, who proposed to the world to use disinfection in surgery, was influenced by Pasteur.Toxic bacteria enter the human body through food and drink.Pasteur developed the method of sterilization in beverages, which is later called pasteurization (heat sterilization)[4]。
Infectious Diseases
At the age of 50, Pasteur focused his attention on malignant carbuncle.It is an infectious disease that harms livestock and other animals, including people;Pasteur proved that the cause was a special bacterium.He used attenuated bacilli of malignant carbuncle to inject animals[4]。
In 1881, Pasteur improved the method of reducing the virulence of pathogenic microorganisms. He observed that animals who had suffered from an infectious disease and recovered from it had immunity to the disease later.Accordingly, sheep and chickens were immunized with attenuated anthrax and chicken cholera pathogens, and success was achieved.This method has greatly stimulated the enthusiasm of scientists.From then on, people knew that many infectious diseases could be avoided by using this method[4]。
Vaccination technology
In 1882, Pasteur was electedFrenchAcademician of the college began to study rabies in the same year, proving that the pathogen existed in the saliva and nervous system of the affected animals, and made a live virus vaccine, which successfully helped people gain immunity to the disease.According to Pasteur's immunization method, medical scientists created vaccines to prevent several dangerous diseases, and successfully exemptedTyphus，polioAnd other diseases[4]。
fermentation
In September 1854, the French Ministry of Education appointed Pasteur as the dean of Lille Institute of Technology and the head of the Department of Chemistry. At that time, he became interested in the alcohol industry, and fermentation was an important process in alcohol production.At that time, an alcohol manufacturing factory in Lille encountered technical problems and asked Pasteur to help study the fermentation process. Pasteur went deep into the factory and brought various beet root juices and fermentation liquids back to the laboratory for observation.After many experiments, he found that there was a globular body much smaller than yeast in the fermentation liquid, which would become yeast when it grew up[4]。
Soon, a bud grew on the mycelium, fell off when it grew up, and became a new spherical body. In the process of continuous circulation, beet root juice "fermented".Pasteur continued his research to find out the relationship between alcohol produced during fermentation andcarbon dioxideThe gas comes from the decomposition of sugar by yeast.This process can happen even without oxygen. He thinks that fermentation is yeastAnaerobic respirationAnd control their living conditions, which is the key link of wine making[4]。
