All about Pressure Canning

I’m nervous about pressure canning – should I be?

I was a bit worried the first time I pressure canned. I had never even used a pressure cooker before, and I had heard the stories about those back in the day (exploding pressure cookers! Yikes!). And I’ll admit, the idea of having shelf-stable meat kind of freaked me out a little bit – but then I thought about the amount of canned tuna I buy and eat!

However, like anything, if you follow the instructions and use safe practices, there is very little to worry about. There’s no doubt that care needs to be taken when preserving and canning food, but it’s very manageable.

And the canners aren’t nearly as scary as they might seem!

My advice would be to try some simple things to start with – carrots in water are a good one, as they are low cost, broths or stocks are a good ‘meat’ product to try early on.

Read on to get an overview of exactly what pressure canning is, how it works and when it’s the best (or only!) method to use.

What is pressure canning?

Some people consider pressure canning to be the only form of ‘canning’, but to my mind any processing of food in jars with heat is a form of canning (water bathing, Fowlers Vacola method, steam canning or pressure canning).

Pressure canning involves putting jars of food into a pressure canner, bringing that canner up to an appropriate pressure and processing at that pressure for the defined time.

Pressure canning is the only method of canning that is safe for low-acid foods.

What does pressure canning do to my food?

Under pressure, the boiling point of water is higher than the ‘regular’ boiling point of 100°C (212°F). As a result, your jars will get to a higher temp than if you were water bathing or steam canning. When pressure canning, the contents of the canner are brought up to 115°C (240°F). Your recipe will stipulate how long your food needs to be held at that temperature for.

The pressure canning process will:

• Kill off potential nasties (bacteria, yeast etc) that may be present in your jars – at this temperature, bacteria and spores that can survive at boiling point will be destroyed

• Pushes air out of the jars, which helps reduce the chances of food spoiling over time

• As the jars cool, a vacuum forms, sealing the jars

What foods are suitable for pressure canning?

Low-acid foods need to be pressure canned. Low-acid foods, in a canning context, have a pH of 4.6 or higher (remember that high pH = low acidity).

Low-acid foods include:

Red meats
Seafood
Poultry
All veg (don’t forget – tomatoes are a fruit!)
Some fruit

This also includes broths or stocks made from these ingredients.

Should I just pressure can everything?

Your recipe should tell you what canning method is needed, and some will give you instructions for water bathing OR pressure canning. If you don’t have to pressure can, based on your recipe, I would give it a miss. Other canning methods (water bathing, steam canning, FV method) may be gentler on your foods, so if you don’t have to pressure can, I wouldn’t.

Also, some foods just aren’t going to be suitable for pressure canning. Softer fruits, as an example are not going to hold up to pressure canning and will go very mushy!

Can I can in a pressure cooker?

Short answer: no. You can cook in pressure canners, but you cannot can in a pressure cooker.

Pressure cookers don’t have a weight or gauge to tell you what pressure they are running at – so you have no way of knowing when you have reached the safe canning pressure. Whilst a pressure cooker and a pressure canner work in similar ways, a pressure cooker may have far more variation in its temperature and potentially get up to temp too quickly for safe canning.

The parts of a pressure canner

This is referring to a Presto pressure canner, a popular brand that seems to be the most common in Australia. In the US, it seems that things are split between Presto and All American and the occasional other brand. Each brand is slightly different, so make sure that you review your manual before you get started. As an example, All American have clamps and bolts to attach the lid, versus the ‘twist on’ style of Presto.

The below info comes from the Presto website, with some additional thoughts from me.

My pressure canners

As this blog post is at risk of becoming longer than War and Peace, I will write a more detailed post about my canners. However, a quick note on my two canners.

Buffalo Commercial Series Pressure Cooker and Canner 35L

This is pretty much the largest pressure canner that you can buy in Australia. Don’t buy this. It’s far too big and only gets pulled out when I have many litres of stock to can. Get a Presto Stove Top model.

Presto Precise Digital Pressure Canner

Yes – an electric one. The jury is still out on these from a third party testing perspective, however I was prepared to take the risk on an electric pressure canner from the Presto brand. Given that they are experts in pressure canning, and in small appliances, it would not be worth them risking their reputation by releasing a questionable product.

References

Presto, Unknown. Pressure Canner and Cooker Instructions.
Kingry, J. and Devine, L. 2020. Ball Complete Book of Home Preserving
McGarry, J. 2014 “Basics of pressure canning foods” Michigan State University MSU Extension
Riggs, K. and Nummer, B. Unknown. “Principles of Pressure Canning” Utah State University Preserve the Harvest Extension