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TERRY DOES SCIENCE!
PASTEURIZATION: Louis Pasteur
Louis Pasteur was born in 1822. During his early years he showed no real interest in anything academic except painting. Later however, thanks to an inspiring teacher, (Balard), not only did he develop an interest, but became an internationally recognised chemist by the tender age of 26.
Pasteurization is a process created by the French scientist, Louis Pasteur which slows the growth of microbes in milk. Prior to pasteurization, many diseases were transmitted through raw milk to children and adults.
Milk is pasteurised by heating it quickly to a little over 70ºC and then cooling it. It is sometimes referred to as the HTST method (High Temperature / Short Time). The milk now has a refrigerated shelf life of two to three weeks.
This process is 99.999% effective.
However, the milk will still go sour. This is because the bacteria that cause milk to go sour can reproduce extremely fast. So the tiny amount of bacteria that are left reproduce and their numbers rise again. To slow this down we keep the milk as cold as possible. That’s why we put the milk into the fridge.
Pasteur understood what was happening. By using his microscope, he could see the bacteria. He reckoned that if he could kill these bacteria, then he would prevent the souring. At the time, many biologists believed in spontaneous generation. Pasteur did not agree with this. He was of the opinion that this souring was caused by microbes.
At the time there was the belief that microbial life was able to appear spontaneously, or basically out of thin air. Pasteur performed a simple yet brilliant experiment to show that it was the microbes in the air, and not the air or dust that caused the souring.
Milk is not the only material that can be pasteurised. Many items can be pasteurized. In fact, Pastuer first looked at the problem of wine going sour. At the time, the French wine-making industry was losing huge amounts of money and they turned to Pasteur for help.
Wine is produced by fermentation. In this process, living microorganisms called yeast feed on sugars and the waste they produce a waste called ethanol (alcohol). This waste is poisonous and at a certain concentration, about 12% the yeast are killed. Fermentation now ceases and the wine is produced.
However, if another, different yeast is also present, it will produce lactic acid or acetic acid and it is this acid that turns the wine sour. What Pasteur needed to do was find a method of killing off this second strain of yeast without harming the other one. He discovered that if the wine was heated to 44ºC that the bad yeast would be killed off. The wine industry were horrified at the thought of heating wine, but after a number of trials realised that this method worked and the wine industry was saved.
Pasteur also saved the silkworm industry in the south of France. The larvae and the silkworms were mysteriously dying. When Pasteur examined them under the microscope, he saw that they were infected by a minute parasite. His solution was for the farmers to burn the infected mulberry plants and the silkworms and replace them with new stock. This was considered drastic advice, but because he was held in such high esteem, his advice was followed and another industry was saved.
At the time, the English surgeon heard of Pasteur’s work with microbes and developed a method of killing microbes in the operating theatre. At the time, 45% of all patients undergoing operations died. Lister knew that he had to get rid of the microbes in the operating room. His method involved using phenol to sterilize his instruments and a phenol atomiser to sterilize the air.
Pasteur had already lost 2 daughters to infection so he decided to devote his working life to the fight against infection.
Later, he turned his attention to the development of a number of vaccines including anthrax in sheep and cholera in chickens. He believed that if a vaccine could be developed against smallpox, then a vaccine could be developed against all infections. He also developed a vaccine for rabies. The first person to be treated for rabies was Joeseph Meister, a young boy who had been bitten by a rabid dog. The boy survived. When he grew up, Joseph worked with Pasteur in the Louis Pasteur Institute in Paris.
In a tragic footnote to history, in 1940, 45 years after his treatment for rabies that made medical history, Meister was ordered by the German occupiers of Paris to open Pasteur's crypt. Rather than comply, Joseph Meister committed suicide!
Today, Louis Pasteur is now known as the father of Microbiology.
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