Pasteurization is a process of treatments designed to remove microbes from milk. Most microbes inhabiting raw milk are lactic acid bacteria, known to aid gastrointestinal (GI) health, but some like Listeria can be fatal.
Invented by Louis Pasteur, pasteurization improves food safety and shelf life. It's intended to ensure product microbial safety while keeping nutritional benefits. In some scenarios the resident lactic acid bacteria (LAB) survive, while in others they don't.
Nonetheless, according to a Latvian study, similar strains of beneficial LAB exist in both raw and pasteurized milk. These microscopic entities are everywhere in the world and important to environmental as well as human health.
This is how it happens ...
In 1864, Pasteur is approached by wine producers in France who have spoilage issues when transporting products. Through experiments, Pasteur finds a way to kill harmful microorganisms by heating the liquid to a specific temperature for a set amount of time.
Initially applied to wine and beer, this process is later extends to milk and other perishable liquids. The discovery marks a pivotal moment in public health, drastically reducing illnesses caused by food contamination.
Pasteur’s experiments find microbes responsible for spoilage and disease transmission. His work contributes to the broader field of microbiology and germ theory to influence modern medicine and food science.
Process of Pasteurization
Pasteurization is a heat treatment to kill harmful microorganisms. The product is heated to a specific temperature for a defined period, then rapidly cooling it to inhibit growth of bacteria, yeasts or mold. Depending on product, various pasteurization methods are used.
Generally, temperatures of 60 to 65°C for several minutes will destroy Salmonella even when they're abundant. Bacillus typhosus which causes typhoid fever, dies in 2 minutes at 60°C in milk.
Standard pasteurization temperatures range from 63 °C (145 °F) to 85 °C (185 °F), depending on the product being treated. Beneficial lactic acid bacteria die at 71°C (160 °F), so these microbes expire in the HTST method.
Some cheese and dairy product makers prefer to kill all the bacteria in the liquid, than add their own lactic acid bacterial strains for flavor, texture and consistency. Use of local microbes is part of the product's terroir, or environmentally influenced properties.
1. Traditional (Low-Temperature Long-Time)
Temperature: 63°C (145°F) for 30 minutes
Uses: Commonly applied to milk and other dairy products.
2. High-Temperature Short-Time (HTST)
Temperature: 72°C (161°F) for 15 seconds
Uses: Widely used for milk, juice, and other beverages. This method retains flavor and nutrients while effectively killing pathogens like Salmonella, E. coli, and Listeria.
3. Ultra-High-Temperature (UHT) Pasteurization
Temperature: 135°C (275°F) for 2–5 seconds
Uses: Produces shelf-stable liquid products like long-life milk and cream not needing refrigeration.
4. Flash Pasteurization
Temperature: Rapid heating and cooling
Uses: Popular for beverages like orange juice and craft beer to maintain flavor while extending shelf life.
Science of Pasteurization
Pasteurization targets the microorganisms of food spoilage or disease. At high temperatures, proteins and enzymes in the microbes denature, making them inactive. While pasteurization does not completely sterilize a product, it kills enough harmful bacteria to make food safer.
What makes pasteurization uniquely effective is its ability to preserve food quality. Unlike sterilization, which degrades taste and texture, pasteurization minimizes changes to the properties of food. Rapid cooling after heating prevents the growth of heat-resistant bacteria.
Pasteurization methods significantly reduce bacterial levels to combat foodborne illnesses such as Salmonella and E. coli. According to the US Centers for Disease Control and Prevention (CDC), pasteurization has helped decrease these illnesses by up to 90%.
Pasteurization in Everyday Life
Pasteurization is now used in a wide range of food and beverages people consume daily. These include:
Milk: The most common and well-known example. Pasteurized milk is safer and lasts longer than raw milk.
Fruit Juice: Popular drinks like orange juice and apple juice are pasteurized to kill pathogens, while retaining their natural flavors.
Beer and Wine: The process prevents spoilage without compromising the taste of these beverages.
Egg Products: Liquid eggs used in restaurants and processed foods are pasteurized to eliminate the risk of Salmonella contamination.
Canned Foods: Pasteurization helps extend the shelf life and safety of canned goods.
Facts About Pasteurization
Raw Milk Debate: Despite widespread adoption, pasteurization faces opposition from raw milk advocates who believe it destroys enzymes and beneficial bacteria. However, scientists and health organizations emphasize that the risks of foodborne illness outweigh the benefits of consuming raw milk.
A French Revitalization: Pasteurization becomes officially recognized in France in 1895, over thirty years after Louis Pasteur's influential research on food safety.
Ice Cream and Pasteurization: The liquid base for most commercial ice creams is pasteurized before being frozen.
Pasteurized Honey: While rare, certain types of honey undergo pasteurization to slow crystallization and remove yeast.
Space Exploration: Pasteurization techniques are used to develop long-lasting foods for astronauts during space missions.
Beyond Food: Pasteurization techniques are also used in the production of pharmaceuticals and cosmetics, illustrating their widespread relevance.
Heat vs. Cold: While traditional pasteurization relies on heat, scientists are exploring low-temperature methods that preserve more natural flavors and nutrients in foods.
Ongoing Innovation: Advances in food safety include techniques like high-pressure processing and ultraviolet light, which may work alongside traditional pasteurization.
As food technology advances, researchers keep exploring ways to use pasteurization. Non-thermal methods like high-pressure processing (HPP) and pulsed electric fields are potential alternatives.
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