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Pasteurization: Making Milk Safe
Pasteurization removes harmful bacteria from the things we eat and drink without destroying the way they taste. Read on for more about Pasteur’s process.
Heat had been used as a sterilizing agent for ages by the time Louis Pasteur lent his name to the process in the 1860s. But in his hands, the technique was transformed from a blunt and poorly understood instrument into a rather delicate science. For one thing, his experiments shed light on why foods went bad in the first place: certain destructive strains of bacteria, or, as he called them in the theory he pioneered, germs.
Having seen and understood these tiny enemies through comparing good and soured batches of wine under the microscope, he could then determine the temperatures needed to first destroy them with heat and then keep new microorganisms from flourishing via quick cooling. (For taste reasons, the technique never caught on with winemakers.) Boiling or sterilizing a liquid such as milk destroys its dangerous microorganisms, but it can also quickly destroy its flavor and texture. Pasteurization, on the other hand, raises milk’s temperature enough to denature some, but not all, of the bacteria’s cells. Denaturing the cells changes their shape and renders them powerless to infect the body or make creepy noises when you walk past the fridge at night.
Three types of pasteurization accomplish this end. Batch, or vat, pasteurization kills most common bacteria by heating liquids to temperatures of 145 degrees Fahrenheit for about 30 minutes. Because of the length of time required, this method is usually used by smaller-scale producers; as a bonus, the lower temperature tends to have little effect on the flavor. HTST (high-temperature, short-time) pasteurization is the most common type of pasteurization and, like a drive-through sauna, heats liquids up to 161 degrees or more in only 15–20 seconds. The final type, ultra-high temperature pasteurization, brings products such as creamers and juices above their boiling point for a fraction of a second. This heat yields food and drink that doesn’t even need to be refrigerated.
Although milk is the first thing that springs to mind when we hear the word pasteurization, the technique can also be used on eggs. How do they avoid cooking them in such heat? The secret is an hourlong bath in a tank of churning water, which raises the eggs’ temperature slowly and evenly enough that their texture won’t change. Some believe that this can help preserve flavor as well as safety: “We’re killing the bacteria that cause flavors to degrade, so they taste more like farm fresh eggs,” a vice-president of National Pasteurized Eggs told the Chicago Tribune in 2010; after a subsequent taste test, Tribune staffers tended to agree.