Louis Pasteur developed and patented the process of pasteurisation in the 1860s. His purpose at the time was to prevent beer spoilage.
By the early 1900s pasteurisation had solved the problem of many common water- and milk-borne diseases such as tuberculosis, diphtheria, severe streptococcal infections, typhoid fever and other foodborne illnesses. Uncountable deaths and immeasurable suffering were prevented by this simple process.
Most civilised countries began pasteurising milk from the 1920s. Now, many liquid and semi fluid foods, including juice, eggs and other dairy products, can be pasteurised.
Pasteurisation does not kill all microorganisms in food but it can significantly reduce pathogen numbers so they do not cause infection. Similarly, pasteurising reduces the number of spoilage organisms, extending a product’s shelf life under refrigeration. Pasteurisation typically reduces microorganism numbers by about 5 to 8 log cycles.
The process involves heating a liquid or semi fluid food to a specific temperature for a set time followed by rapid cooling. Different time-temperature combinations are effective for different products, particularly when flavour is affected by heating. Compare the difference in taste of a fresh cooked product with its canned equivalent, and it is clear why the process is desirable for some more chemically fragile liquid foods.
The Vat pasteurisation process involves heating milk to 63 degrees Celsius for 30 minutes. Flash Pasteurisation – HTST (high-temperature short-time) processing is at 72 degrees for around 15 seconds.
UHT or ultra-high temperature pasteurisation involves heating product rapidly to 138 degrees C for 2 seconds. This actually sterilises the product and makes it shelf stable without refrigeration.
Without pasteurisation, such serious and potentially fatal bacteria such as E. coli, Campylobacter and Salmonella would be far more common.
The latest update from the US Centre for Disease Control and Prevention (CDC), reports 48 outbreaks due to consumption of raw milk or raw milk products in the US between 1998 and 2011. There were 2,384 illnesses, 284 hospitalisations and two deaths. 75% of the outbreaks occurred in 21 states that permit sale of non-pasteurised products.
I have heard it said that we do not have a problem because we are not a ‘third world’ country. There is a reason for that. We are no longer a developing country solely because we have adopted sensible, sane and safe technology such as pasteurisation. In developing countries, where resources are stretched, the technology is not available, or the health system less efficient, the death rates are considerably higher. http://apps.who.int/gho/data/node.main.168. This is also seen in the US where the greatest burden is suffered in states that allow sale of unsafe product.
The much- touted claim that pasteurised milk is not as nutritious as raw milk is simply not true. The evidence relating to the difference in health and nutrition between pasteurised and raw milk is that there is no significant difference. Pasteurisation causes a small decrease in the amount of vitamin C and thiamine in the milk. However, milk is not a major contributor of these nutrients to the diet.
Independent blind taste tests have demonstrated even the claims that unpasturised milk makes better tasting cheese are misleading. The indication is that any perceived difference in flavour is likely due to bias on the part of the taster.