How does the treatment pasteurisation work?

Answer 1

Pasteurization is a process of heating a food, usually liquid, to a specific temperature for a definite length of time, and then cooling it immediately. This process slows microbial growth in food. The process was named after its creator, French chemist and microbiologist Louis Pasteur. The first pasteurization test was completed by Louis Pasteur and Claude Bernard on April 20, 1864. The process was originally conceived as a way of preventing wine and beer from souring.[1]

Pasteurization aims to reduce the number of viable pathogens so they are unlikely to cause disease (assuming the pasteurized product is stored as indicated and consumed before its expiration date). Commercial-scale sterilization of food is not common because it adversely affects the taste and quality of the product. Certain food products, like dairy products, are superheated to ensure toxic microbes are destroyed.

Answer 2

Dry heat can be used to sterilize items, but as the heat takes much longer to be transferred to the organism, both the time and the temperature must be increased. The standard setting for a hot air oven is at least two hours at 160°C (320°F). A rapid method heats air to 190°C (374°F) for 6–12 hours. Dry heat has the advantage that it can be used on powders and other heat-stable items that are adversely affected by steam (for instance, it does not cause rusting of steel objects).

For prion elimination, various recommendations state 121–132°C(270°F) for 60 minutes or 134°C (273°F) for at least 18 minutes. The prion that causes the disease scrapie (strain 263K) is inactivated relatively quickly by such sterilization procedures; however, other strains of scrapie, as well as strains of CJD and BSE have shown much more resistance. Using mice as test animals, one experiment showed that heating BSE positive brain tissue at 134-138°C (273-280°F) for 18 minutes resulted in only a 2.5 log decrease in prion infectivity. (The initial BSE concentration in the tissue was relatively low). To have a significant margin of safety, cleaning should reduce infectivity 4 logs, and the sterilization method should reduce it a further 5 logs.

By combining immersion in sodium hydroxide

(NaOH 0.09N) for two hours with one hour autoclaving (121°C / 250°F), several investigators have shown complete (>7.4 logs) inactivation. (Note that sodium hydroxide may corrode surgical instruments, especially if the sodium hydroxide immersion and autoclaving steps are combined.)

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Pasteurisation (or Pasteurization) is the process of heating food for the purpose of killing harmful organisms such as bacteria, viruses, protozoa, molds, and yeasts. The process was named after its inventor, French scientist Louis Pasteur. The first pasteurisation test was completed by Pasteur and Claude Bernard on April 20, 1862.

Unlike sterilisation, pasteurisation is not intended to kill all micro-organisms in the food. Instead, pasteurisation aims to achieve a "log reduction" in the number of viable organisms, reducing their number so they are unlikely to cause disease (assuming the pasteurised product is refrigerated and consumed before its expiration date). Commercial scale sterilisation of food is not common, because it adversely affects the taste and quality of the product.

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Methods of Filtration


There are many different methods of filtration, all aim to attain the separation of two or more substances. This is achieved by some form of interaction between the substance or objects to be removed and the filter. In addition the substance that is to pass through the filter must be a fluid, i.e. a liquid or gas.

The simplest method of filtration is to pass a solution of a solid and fluid through a porous interface so that the solid is trapped, while the fluid passes through. This principle relies upon the size difference between the particles making up the fluid, and the particles making up the solid. In the laboratory, a Büchner funnel is often used, with a filter paper serving as the porous barrier.

By extending this principle, it is possible to separate any two things with a significant or reliable size difference. For example an experiment to prove the existence of microscopic organisms involves the comparison of water passed through unglazed porcelain and unfiltered water. When left in sealed containers the filtrated water takes longer to go foul, showing that very small items (such as bacteria) can be removed from fluids by filtration.

Answer 3

I think you boil it