Pasteurized milk has a longer shelf life than raw milk because it has been heated to high temperatures to eliminate pathogenic bacteria, reducing its microbial load and extending its shelf life.
Pasteurization is a simple thermal treatment that allows, by rapidly heating milk to a temperature generally between 72°C and 85°C for a few seconds, to destroy a large part of the potentially dangerous microorganisms or those responsible for milk spoilage. This process improves the food safety of the milk while preserving most of its nutritional and taste qualities. The milk thus heated is then quickly cooled to stop the action of the heat and prevent the proliferation of any remaining bacteria. This technique does not completely sterilize the product, but it does achieve a significant reduction in the present germs, which provides a shelf life much longer than that of raw milk.
Pasteurization involves quickly heating milk (generally to around 72°C for about 15 seconds) before immediately cooling it down. This very brief thermal treatment is sufficient to destroy a large portion of microorganisms, including those responsible for diseases and spoilage. In simple terms, it "kills off" most pathogenic bacteria, such as Listeria or Salmonella, as well as various microbes that cause the milk to turn rancid or sour. However, caution is still warranted: some more resistant bacteria manage to survive pasteurization, although they remain greatly weakened and few in number. As a result, pasteurized milk becomes much safer to consume and lasts longer in the fridge, without becoming completely sterile.
Raw milk naturally contains microorganisms, such as lactic bacteria or other undesirable microflora. Since it undergoes no heat treatment, these bacteria remain present and multiply rapidly, especially at room temperature. Rapid multiplication means a quick deterioration, leading to acidification, unpleasant taste, and bad odor. Additionally, the milk's natural enzymes remain active and also accelerate its degradation. If there was any contamination during milking or handling, you introduce even more bacteria into the equation. Therefore, without treatment, even when stored in a cool place, raw milk generally lasts no more than 24 to 72 hours.
Pasteurization is a heat treatment that will destroy a large majority of the germs naturally present in milk. By briefly heating the milk to a high temperature (usually around 72°C for about fifteen seconds), most harmful bacteria and microorganisms responsible for rapid spoilage are eliminated. As a result, pasteurized milk can be stored for several days, even weeks in the refrigerator, while raw milk spoils much faster due to these tiny creatures that proliferate quickly at room temperature or even when chilled. Pasteurization significantly slows down their development, which directly helps to increase shelf life and keep the milk safe for consumption for a longer time.
Pasteurization helps to preserve many essential nutrients in milk such as calcium, proteins, and a good portion of vitamins. However, it does lead to a slight loss of heat-sensitive vitamins, particularly vitamin C and some B vitamins. From a health perspective, it is a significant improvement since pathogenic microorganisms responsible for contamination (such as salmonella or listeria) are eliminated, making milk much safer to drink than raw milk. Overall, the nutritional quality remains very satisfactory, with the tremendous advantage of significantly reducing the risk of diseases.
Even after being pasteurized, milk must still be kept at a low temperature (below 4°C) to slow down any potential growth of remaining bacteria and ensure optimal preservation.
Raw milk contains natural enzymes that aid in its digestion for some individuals, but it also carries an increased risk of contamination by pathogenic bacteria such as Salmonella or Escherichia coli. This is why it is not recommended for vulnerable populations such as young children, pregnant women, or immunocompromised individuals.
Did you know that pasteurization was developed in the 19th century by Louis Pasteur, initially to preserve wine and beer from bacterial contamination? It was only later that this method was applied to milk to extend its shelf life and improve its safety.
Unlike sterilization, which completely destroys the present organisms, pasteurization retains some beneficial microorganisms in the milk, thus better preserving the taste and nutritional qualities of the product.
Yes, it is entirely possible to freeze pasteurized milk for long-term storage (up to a few months at -18°C). However, after thawing, its texture may be different, with a tendency for the fat and water to separate. It is therefore preferable to use this milk in cooking rather than as a direct drink.
Pasteurization slightly affects some heat-sensitive nutrients, such as certain B vitamins and vitamin C, but the majority of essential nutrients (calcium, proteins, lipids) remain intact after this moderate heat treatment.
If it comes from a strictly controlled operation, raw milk can be consumed with caution. However, due to the risks associated with pathogenic microorganisms, it is strongly advised against for pregnant women, young children, the elderly, and immunocompromised individuals.
Once opened, pasteurized milk should be stored in the refrigerator and ideally consumed within 2 to 3 days to avoid any risk of bacterial growth.
Pasteurization involves heating milk to moderate temperatures (around 72–75°C for 15-20 seconds), destroying most pathogenic bacteria without significantly altering its flavor or nutritional qualities. In contrast, sterilization uses higher temperatures (above 100°C) to eliminate all microorganisms, allowing for much longer preservation, but with more noticeable changes in taste and nutritional value.
Pasteurization eliminates the vast majority of pathogenic microorganisms present in raw milk, which allows for a longer shelf life and significantly reduces health risks for the consumer.
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