What You Can (And Can’t) Safely Do With Frozen Meat

Yesterday, we asked you:

❝You have meat in the freezer. How long is it really safe to keep it?❞

…and got a range of answers, mostly indicating to a) follow the instructions (a very safe general policy) and b) do not refreeze if thawed because that would be unsafe. Fewer respondents indicated that meat could be kept for much longer than guidelines say, or conversely, that it should only be kept for weeks or less.

So, what does the science say?

Meat can be kept indefinitely (for all intents and purposes) in a freezer; it just might get tougher: True or False?

False, assuming we are talking about a normal household electrical freezer that bottoms out at about -18℃ / 0℉.

Fun fact: cryobiologists cryopreserve tissue samples (so basically, meat) at -196℃ / -320℉, and down at those temperatures, the tissues will last a lot longer than you will (and, for all practical purposes: indefinitely). There are other complications with doing so (such as getting the sample through the glass transition point without cracking it during the vitrification process) but those are beyond the scope of this article.

If you remember back to your physics or perhaps chemistry classes at school, you’ll know that molecules move more quickly at higher temperatures, and more slowly at lower ones, only approaching true stillness as they near absolute zero (-273℃ / -459℉ / 0K ← we’re not saying it’s ok, although it is; rather, that is zero kelvin; no degree sign is used with kelvins)

That means that when food is frozen, the internal processes aren’t truly paused; it’s just slowed to a point of near imperceptibility.

So, all the way up at the relatively warm temperatures of a household freezer, a lot of processes are still going on.

What this means in practical terms: those guidelines saying “keep in the freezer for up to 4 months”, “keep in the freezer for up to 9 months”, “keep in the freezer for up to 12 months” etc are being honest with you.

More or less, anyway! They’ll usually underestimate a little to be on the safe side—but so should you.

Bad things start happening within weeks at most: True or False?

False, for all practical purposes. Again, assuming a normal and properly-working household freezer as described above.

(True, technically but misleadingly: the bad things never stopped; they just slowed down to a near imperceptible pace—again, as described above)

By “bad” here we should clarify we mean “dangerous”. One subscriber wrote:

❝Meat starts losing color and flavor after being in the freezer for too long. I keep meat in the freezer for about 2 months at the most❞

…and as a matter of taste, that’s fair enough!

It is unsafe to refreeze meat that has been thawed: True or False?

False! Assuming it has otherwise been kept chilled, just the same as for fresh meat.

Food poisoning comes from bacteria, and there is nothing about the meat previously having been frozen that will make it now have more bacteria.

That means, for example…

• if it was thawed (but chilled) for a period of time, treat it like you would any other meat that has been chilled for that period of time (so probably: use it or freeze it, unless it’s been more than a few days)
• if it was thawed (and at room temperature) for a period of time, treat it like you would any other meat that has been at room temperature for that period of time (so probably: throw it out, unless the period of time is very small indeed)

The USDA gives for 2 hours max at room temperature before considering it unsalvageable, by the way.

However! Whenever you freeze meat (or almost anything with cells, really), ice crystals will form in and between cells. How much ice crystallization occurs depends on several variables, with how much water there is present in the food is usually the biggest factor (remember that animal cells are—just like us—mostly water).

Those ice crystals will damage the cell walls, causing the food to lose structural integrity. When you thaw it out, the ice crystals will disappear but the damage will be left behind (this is what “freezer burn” is).

So if your food seems a little “squishy” after having been frozen and thawed, that’s why. It’s not rotten; it’s just been stabbed countless times on a microscopic level.

The more times you freeze and thaw and refreeze food, the more this will happen. Your food will degrade in structural integrity each time, but the safety of it won’t have changed meaningfully.

Want to know more?

Further reading:

You can thaw and refreeze meat: five food safety myths busted

Take care!

Pasteurization’s Effect On Risks & Nutrients

In Wednesday’s newsletter, we asked you for your health-related opinions of raw (cow’s) milk, and got the above-depicted, below-described, set of responses:

• About 47% said “raw milk is dangerous to consume, whereas pasteurization makes it safer”
• About 31% said “raw milk is a good source of vital nutrients which pasteurization would destroy”
• About 14% said “both raw milk and pasteurized milk are equally unhealthy”
• About 9% said “both raw milk and pasteurized milk are equally healthy”

Quite polarizing! So, what does the science say?

“Raw milk is dangerous to consume, whereas pasteurization makes it safer: True or False?”

True! Coincidentally, the 47% who voted for this are mirrored by the 47% of the general US population in a similar poll, deciding between the options of whether raw milk is less safe to drink (47%), just as safe to drink (15%), safer to drink (9%), or not sure (30%):

Public Fails to Appreciate Risk of Consuming Raw Milk, Survey Finds

As for what those risks are, by the way, unpasteurized dairy products are estimated to cause 840x more illness and 45x more hospitalizations than pasteurized products.

This is because unpasteurized milk can (and often does) contain E. coli, Listeria, Salmonella, Cryptosporidium, and other such unpleasantries, which pasteurization kills.

Source for both of the above claims:

Characteristics of U.S. Consumers Reporting Past Year Intake of Raw (Unpasteurized) Milk: Results from the 2016 Food Safety Survey and 2019 Food Safety and Nutrition Survey

(we know the title sounds vague, but all this information is easily visible in the abstract, specifically, the first two paragraphs)

Raw milk is a good source of vital nutrients which pasteurization would destroy: True or False?

False! Whether it’s a “good” source can be debated depending on other factors (e.g., if we considered milk’s inflammatory qualities against its positive nutritional content), but it’s undeniably a rich source. However, pasteurization doesn’t destroy or damage those nutrients.

Incidentally, in the same survey we linked up top, 16% of the general US public believed that pasteurization destroys nutrients, while 41% were not sure (and 43% knew that it doesn’t).

Note: for our confidence here, we are skipping over studies published by, for example, dairy farming lobbies and so forth. Those do agree, by the way, but nevertheless we like sources to be as unbiased as possible. The FDA, which is not completely unbiased, has produced a good list of references for this, about half of which we would consider biased, and half unbiased; the clue is generally in the journal names. For example, Food Chemistry and the Journal of Food Science and Journal of Nutrition are probably less biased than the International Dairy Association and the Journal of Dairy Science:

FDA | Raw Milk Misconceptions and the Danger of Raw Milk Consumption

this page covers a lot of other myths too, more than we have room to “bust” here, but it’s very interesting reading and we recommend to check it out!

Notably, we also weren’t able to find any refutation by counterexample on PubMed, with the very slight exception that some studies sometimes found that in the case of milks that were of low quality, pasteurization can reduce the vitamin E content while increasing the vitamin A content. For most milks however, no significant change was found, and in all cases we looked at, B-vitamins were comparable and vitamin D, popularly touted as a benefit of cow’s milk, is actually added later in any case. And, importantly, because this is a common argument, no change in lipid profiles appears to be findable either.

In science, when something has been well-studied and there aren’t clear refutations by counterexample, and the weight of evidence is clearly very much tipped into one camp, that usually means that camp has it right.

Milk generally is good/bad for the health: True or False?

True or False, depending on what we want to look at. It’s definitely not good for inflammation, but the whole it seems to be cancer-neutral and only increases heart disease risk very slightly:

• Keep Inflammation At Bay ← short version is milk is bad, fermented milk products are fine in moderation
• Is Dairy Scary? ← short version is that milk is neither good nor terrible; fermented dairy products however are health-positive in numerous ways when consumed in moderation

You may be wondering…

…how this goes for the safety of dairy products when it comes to the bird flu currently affecting dairy cows, and the good news is, the heat of pasteurization kills it:

With all this bird flu around, how safe are eggs, chicken or milk?

Take care!