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If I brine a turkey in a solution of 1/2 cup of salt per 1 gallon of distilled water, how do I tell how cold it can get before the brine freezes?

Here in America, we all know water freezes at 32 degree Fahrenheit... if pure. Salt reduces the freezing point of water, which is why we salt our roads to melt ice in winter.

Since my fridge is fairly full, I would prefer to keep the brine bucket in the garage overnight. However, it may get as cold as 26 degrees F tonight. Will a brine with 1/2 cup salt per gallon distilled water freeze at that temperature? Is there a good way to calculate the temperature to make an answer applicable to multiple brine ratios and temperatures?

Wikipedia has a page on saline water and its freezing points but this requires calculation of molar masses and more chemistry than I am capable of - is there a way to simplify this in the context of cooking proportions? I.e. cups and gallons, not g/cm3 and other measurements.

To be more specific, I am using Alton Brown's brine recipe. 1 quart of store-bought vegetable stock mixed with one gallon of water, 1 cup of salt, and 1/2 cup of brown sugar. Boil to dissolve/mix, then chill in the fridge. Combine with another gallon of chilled water and store chilled (fridge or outdoors in a cold climate, in a detached garage in my case). However, a good answer will not assume a specific recipe: it will specify ratios and explain "X cups salt, Y cups sugar, Z gallons water = W% brine concentration" since not everyone uses the same brine. I am looking for an answer that anyone can use to convert cooking volumes (cups/gallons) into temperatures: "I put X cups of salt into Y gallons of water, how cold can it get before this freezes and the brine fails to do its job?"


Actual results: the brine appears not to have frozen. When I checked in the morning it was liquid without any ice chunks floating in it. I am still interested in a more scientific approach to planning this, however.

  • If it gets to 26 degrees F tonight you think the garage will get below freezing? – paparazzo Nov 23 '17 at 10:03
  • So, did it freeze? – FuzzyChef Nov 23 '17 at 21:59
  • @FuzzyChef please see my edit – user21524 Nov 24 '17 at 4:09
  • I give you the formula for a salt brine below. – FuzzyChef Nov 28 '17 at 6:05
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Short answer: a recommended 6% brine solution will not quite freeze at 26F.

Long answer:

You should have just looked at the chart on the Wikipedia page, which has % by weight. That's easy to calculate; just divide the weight of the salt (4.5oz for 1/2 cup) into the weight of the water (133 oz). This is, of course, way easier to do in metric (128g into 4000g).

Note that you will find widely varying estimates for the weight of a half-cup of kosher salt on the web, from 2.5oz/70g up to 5oz/140g. Based on weighing Diamond Crystal Kosher Salt in my own kitchen, the correct answer is towards the high end of this range (4.5oz / 128g). To answer the math part of your question, if you're willing to believe my scale rather than getting out one of your own, each 1/2 cup of salt per gallon represents about 3% salinity by weight and about 3.5deg F drop in freezing temperature, at least up to 2 cups.

You also should have read better instructions on brining a turkey, as the amounts you ask about, 1/2 cup salt per gallon of water, is far too low in salt. That's only about 3% to 3.5%, which is well below the recommended brine strength and will result in a watery turkey (as well as frozen brine at 26F). You want a 6% saline solution by weight.

And, coincidentally, per the chart a 6% brine solution should freeze at around 25F, putting you in the clear. Mind you, that means you'd better be pretty confident in that weather forecast.

On the other hand, maybe you should try a dry brine instead?

  • Interesting read. I have been using Alton Brown's brine recipe which is half the salt content your link says I should aim for. So far it has worked okay, but maybe next year I can do it better? (Note: his recipe is 1 gallon vegetable stock, 1 gallon ice water: I consider vegetable stock to be water with a few ounces of extras, maybe some extra salt, but nothing that changes the overall balance) – user21524 Nov 23 '17 at 6:12
  • Huh? The recipe you linked recommends a full cup of kosher salt per gallon. Plus I wouldn't assume that Alton's veggie stock is low-salt (quite the opposite, really). – FuzzyChef Nov 23 '17 at 6:21
  • You might have to worry about the turkey freezing though? The brine doesn't put that much salt into it, so if it drops below freezing, the outer layer of the turkey could start to freeze. I suppose it's not a huge deal though, it'll just mean the brine won't be quite as effective, not like it's unsafe. And... really, it's going to take a long time for even just the brine to reach 26F, especially sitting in a garage, so it probably wouldn't freeze for that long if at all anyway. – Cascabel Nov 23 '17 at 6:23
  • Oh, I see, it's a gallon of water and a gallon of stock. However, there's also a 1/2 cup of sugar, which is part of the brine, it's not just salt, and that affects both the conditioning of the meat and the freezing temperature. That also leaves out how much salt is expected to be in the vegetable stock, which we don't know ... I can't find Alton's recipe for veggie stock online. – FuzzyChef Nov 23 '17 at 6:28
  • @FuzzyChef good point, the sugar affects the freezing temperature as well. It is not as effective as salt, but not negligible, either. I used Swanson's vegetable stock which is a carton of 4 cups of product containing 3.2g of sodium, mixed with 1 gallon of water (so really 2.25 gallons of liquid total - 0.25 gallons of vegetable stock, 1 gallon of water mixed in on the stove, then another gallon of chilled water when actually brining the turkey). – user21524 Nov 23 '17 at 7:10

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