Water bath canning = steam bath canning?

October 26, 2023 4:53 PM

Is it safe and effective to can by placing the jars in a "bath" of steam (i.e. on a rack over boiling water in a pot) rather than in boiling water?

It seems logical that the steam bath would be as effective as the traditional boiling-water bath (maybe with the bath times increased, as the steam wouldn't heat the jars as quickly as boiling water would), but I haven't seen a steam method described anywhere I've researched this and, especially as a novice canner, I don't want to take any chances when food poisoning is a possibility. Please advise!

posted by Mechitar to Food & Drink (7 answers total)

(My answer assumes you're not doing pressure canning, and that you are canning acidic food that does not require steam sterilization.) The temperature at 1 atm in both would be the same for the purposes of sterilization. It's just that water is a more effective conduit of heat to what you are canning. Water is more dense than steam, so it does a better job of carrying heat to the jars than steam. With steam, also, you'll have to have less water in the canning container, which means you have to babysit it more constantly and frequently to keep at least some water in there at all times — you absolutely don't want it to boil dry. Water canning is fine; just use canning tongs or "jar lifters" to get jars in and out and you're fine.
posted by They sucked his brains out! at 5:11 PM on October 26, 2023 [2 favorites]

There is a specific way to do it, and the process is different from water bath canning. So atmospheric steam canning is a thing, but it relies on having constant steam that is at the right temperature for the entire time of processing. You need specifically a steam canner apparatus to do it, not a rack over a pot. Don't wing it!
posted by blnkfrnk at 5:12 PM on October 26, 2023 [8 favorites]

I go with the tried-and-true when canning and always stick to water bath. Haven't heard of steam canning, but did find this link from a South Dakota Extension about the process.

Seems like a couple things you need to be sure of: "Process in pure steam at 210-212 degrees F" and "Steam must flow through the canner vent during the process or the food is considered unsafe to consume." That's the sort of stuff that probably has special equipment to make sure that is happening, and if you're asking this, you probably don't have it. I definitely wouldn't use a normal canning pot with less water and consider it good enough.
posted by msbrauer at 5:14 PM on October 26, 2023 [4 favorites]

Here's info from a blog about steam canning equipment.
posted by msbrauer at 5:15 PM on October 26, 2023

I've been water bath and pressure canning for 30 years and really can't emphasize enough how good an idea it is to nail the basics before going off piste. New to this? Use tested recipes and methods with good quality, well maintained materials. Been doing it forever? Same, actually.
posted by Ardnamurchan at 5:51 PM on October 26, 2023 [18 favorites]

maybe with the bath times increased, as the steam wouldn't heat the jars as quickly as boiling water would

I think this is the rub. Steam is several orders of magnitude less dense than liquid water and while it may still be efficient at transferring heat (and you're taking advantage of the fact that it releases its latent heat of vaporization when it condenses on the cooler surface of the jar, at least at first), there's just a lot less energy there. Like, probably thousands of times less per unit of volume. So you need to make sure there's plenty of steam for long enough (you don't boil the steam canner dry) and that it's evely distributed around what youre canning (you're also venting the canner to ensure you're not getting stagnant, cold spots). Basically, it's logistically more complicated and there are more ways it can fail if you don't get the conditions exactly right.
posted by pullayup at 6:08 PM on October 26, 2023

I can answer this question! YES! It is possible to do this. I own a steam canner. I wouldn’t try it without a specifically designed pot; mine has a built in thermometer in the lid so you can tell when it reaches the correct temperature. The advantage of this over a water bath is that it uses less energy and doesn’t take as long to heat up; also the size of the steam canner is very large, larger than the largest pots I own that I can use for water canning. It can also be used as a straight up water canner if you want.

I would say this is about the same level of difficulty as canning with a water bath, and possibly a little easier bc I am always nervous about dealing with huge pots of boiling water and making sure my jars are completely submerged.

As always, only use water and steam canning on acidic foods and use recipes approved for water canning, not pressure canning.
posted by bq at 8:52 PM on October 26, 2023 [2 favorites]