Concerns about possible transmission to people drinking unpasteurized milk are being talked about a lot. Apparently they fed mice unpasteurized milk, and they got the virus, but it seems like the temperature required to kill. The virus is higher than what they used to sterilize the milk. How is this safe?
In: Biology
as everyone else is mentioning here, sterilization is a function of both time AND temperature.
but for clarity, there are several methods of pasteurization. the only one that uses as low a temp as you describe is LTLT (Low temp, long time) pasteurization which holds the product at about 145F for 30minutes. I dont have the numbers on which is the most common, but LTLT is the original batch process heat treatment that is largely been abandoned for other processes using higher temps and shorter times.
Bulk pasteurization goes to 145F and is held for several minutes. However, hardly anyone uses bulk pasteurization. Dairies use HTST, high temperature short time pasteurization. This goes to 165f and holds for 15 seconds.pasteurization kills pathogens. It does not sterilize the milk.
In the U.S., most milk is pasteurized to 160F.
“The standard US protocol for flash pasteurization of milk, 71.7 °C (161 °F) for 15 seconds in order to kill Coxiella burnetii (the most heat-resistant pathogen found in raw milk), was introduced in 1933, and results in 5-log reduction (99.999%) or greater reduction in harmful bacteria.”
Most organic milk, and nearly all milk in Europe, is pasteurized at an even higher temperature.
As someone who uses a sous vide to cook I can tell you that the temperature listed is for instant death, but holding something at 145 for 10 mins might be equally as effective while not ruining the texture of the milk. It’s the same with cooking something like chicken. They say an internal temp of 160 is minimum safe, but cooking at 140 for several hours would also be quite effective at making it safe (though “rare” chicken tastes weird and has a weird texture, so most people still would cook it more).
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…are you drinking bird milk?
NEJM actually just published a good article about this: https://www.nejm.org/doi/full/10.1056/NEJMc2405495
All milk is not pasteurized to 145 degrees, some milk is pasteurized at much temperatures. UHT pasteurizing is done at about 285 degrees (with a pretty short hold time)
Source: I work with milk
Because there’s more than one factor at play here. It isn’t just the temperature that matters, it’s the exposure time as well. Basically, the 165 mark is what it takes for the bacteria to die instantly. If you manage to bring the milk up to that temperature, Avian Flu will be completely gone in that instant. But, you can instead bring it to a lower temperature for longer and it will still kill the bacteria. The “threshold”, or minimum, temperature is different for every microbe pretty much. You can’t leave the milk there at room temp and expect it to be pasteurized at some point.
For the record, in my field (Sterilization Tech, CRCST) the number is much higher. We achieve temperatures exceeding 270 F and exposure times of up to about 120 minutes at max. The pasteurization process SANITIZES it, does not STERILIZE it. They’d be burning the milk if they wanted to do that.
I know people are concerned about this but current pasteurization process for “Grade A” milk is sufficient to kill bird flu and other flu viruses. According to the FDA”
“The FDA and USDA have indicated that based on the information we currently have, our commercial milk supply is safe because of both the pasteurization process and that milk from sick cows is being diverted or destroyed. The federal-state milk safety system, and the Grade “A” Pasteurized Milk Ordinance, have proven effective for decades against a wide range of pathogens. Data from previous studies shows that pasteurization is very likely to effectively inactivate heat-sensitive viruses in fluid milk. Furthermore, thermal inactivation of HPAI has been successful during the pasteurization process for eggs, which occurs at lower temperatures than what is used for fluid milk. Given this is a novel and evolving situation, the FDA and USDA are working closely to collect and evaluate additional data and information specific to HPAI A (H5N1) to support our state co-regulators as they manage this emerging disease in dairy cattle. ”
[https://www.fda.gov/food/milk-guidance-documents-regulatory-information/questions-and-answers-regarding-milk-safety-during-highly-pathogenic-avian-influenza-hpai-outbreaks](https://www.fda.gov/food/milk-guidance-documents-regulatory-information/questions-and-answers-regarding-milk-safety-during-highly-pathogenic-avian-influenza-hpai-outbreaks)
As a virologist myself, don’t confuse the deadliness of a virus with it stability. Flu viruses are not the most hardy viruses out there when things like milk are being heat treated. Grade A milk covers 99% of all milk in the U.S. I suspect the remaining one percent might be those few people who drink unpasteurized milk, but not sure. I would never recommend someone drink raw milk, even if there was no bird flu going around. That is a great way to infect yourself with pathogens that can be found in milk. If it is pasteurized you good drink away, it is safe.
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