Before he began this crucial work, the scientific community regarded the theory of spontaneous generation as the cause of microbiological infestation — in short, that pathogens could arise naturally from nonliving matter.
Experimenting with wine, he showed that thermal processing would inactivate unwanted microorganisms in sterilized and sealed flasks that, when opened, allowed them to grow. From this point on, the concept that diseases can be caused by pathological infection shifted to preventing them from entering the human body.
Pasteur completed the first successful test on April 20, , eventually patenting the method we now know as pasteurization, which was soon applied to beer, juice, eggs, and most famously milk.
This process also proved successful at destroying most yeasts and molds without causing a phase transition in the product. Louis Pasteur in his lab performing experiments. Food can be pasteurized in two basic ways: either before or after being packaged into containers.
When food is packaged in glass, hot water is used to lower the risk of thermal shock. If packaged in plastic or metal, steam can be used, since the risk of thermal shock is low. In general, most foods requiring pasteurization are liquid such as milk , and can therefore move through a continuous system comprised of a heating zone, hold tube, and cooling zone, from which the liquid is filled into packaging.
The pasteurization process. Pasteurization Type. In addition to these traditional methods of pasteurization, newer processes have been developed to pasteurize foods as a way of extending shelf life without refrigeration, reducing the effects on the sensory characteristics of foods, and preventing degradation of nutrients. A few examples include:. While pasteurization has helped provide safe, nutrient-rich milk and cheese for over years, some raw milk enthusiasts claim that pasteurization reduces the nutritional value of milk and that raw milk is a safe, healthier alternative if properly processed in a sterile environment.
Currently, both the CDC and the FDA dismiss these claims as lacking scientific evidence and affirm that raw milk remains less safe than pasteurized milk. Historically, milk has been a major source of foodborne illness when people increasingly migrated from rural to urban areas.
As population density increased and supply chains became longer and more complicated, raw milk often reached consumers days or weeks old. By the turn of the 20th century, childhood deaths attributed to contaminated milk skyrocketed, causing a major public health crisis. After incidents of illness and death markedly decreased, individual cities and states began enacting mandatory pasteurization laws.
By , with more than 50 years of evidence that the process was saving lives, the federal government required pasteurization of milk used in any interstate commerce.
Today, the CDC maintains that improperly handled raw milk is responsible for nearly three times more hospitalizations than any other source of foodborne disease. The FDA has also published its own webpage that debunks common myths about raw milk and pasteurization:. For his proof of germ theory, discovery of fermentation, and invention of pasteurization, Louis Pasteur was a French national hero by age 55, and even today, his name is a household word across the world. As far as beer went, this was mostly a cosmetic, not a health issue.
But milk presented an altogether different scenario. Typhoid and scarlet fever, diphtheria, tuberculosis and various diarrheal diseases were all capable of being transmitted through the consumption of milk.
But it seems that until , when von Soxhlet made his suggestion, nobody thought of pasteurizing milk on a large scale. And what a difference pasteurization made! In , one in every four infants in New York City died, many from drinking tainted milk. This dropped to about one in fourteen when pasteurization was introduced.
The advent of this life-saving technology, though, was not without its critics. Amazingly, the controversy about the pros and cons of pasteurization continues to this day.
However, Pasteur observed that paratartaric acid did not rotate plane-polarized light. He deduced that although the two compounds had the same chemical composition, they must somehow have different structures.
Looking at the paratartaric acid under a microscope, Pasteur observed there were two different types of tiny crystals. Though they looked almost identical, the two were actually mirror images of each other. He separated the two types of crystals into two piles and made solutions of each.
When polarized light was passed through each, he discovered that both solutions rotated, but in opposite directions. When the two crystals were together in the solution the effect of polarized light was canceled. This experiment established that just studying the composition is not enough to understand how a chemical behaves.
The structure and shape is also important and led to the field of stereochemistry. In , Pasteur was appointed professor of chemistry and dean of the science faculty at the University of Lille.
There, he worked on finding solutions to the problems with the manufacture of alcoholic drinks. Working with the germ theory, which Pasteur did not invent but further developed through experiments and eventually convinced most of Europe of its truth, he demonstrated that organisms such as bacteria were responsible for souring wine, beer and even milk. He then invented a process where bacteria could be removed by boiling and then cooling liquid.
He completed the first test on April 20, Today the process is known as pasteurization. Shifting focus, in , Pasteur helped save the silk industry. He proved that microbes were attacking healthy silkworm eggs, causing an unknown disease and that the disease would be eliminated if the microbes were eliminated.
He eventually developed a method to prevent their contamination and it was soon used by silk producers throughout the world. Pasteur's first vaccine discovery was in , with a disease called chicken cholera.
0コメント