It’s been a very busy week – we’ve had a wedding, family in from all over the world, an accidental dinner parts for more than 60 (we figured we’d get 13), and just an all-out fun party for 3 days. Connection to the blog and the community here has been very low (a massive pile of comments to go through awaits for a free moment).
We’ve only been around enough to pop by and smile at the messages we’re seeing here and the Facebook Community. The group was abuzz last night with items that each of us had cooked and were very happy with over the weekend. Lynne mentioned that she did her first ever batch of canning on the weekend (strawberry jam – this was also my ‘gateway’ into preserving) and that she had fabulous success.
Lynne also mentioned that she had some minor confusion around acid levels and waterbath vs. pressure can. I think most of us have had this question (I remeber it feeling like such a mystery) as we learned and I wanted to flip her the easy explanation – and realized I didn’t have a short article that explained the differences. I’m hoping today builds that resource to help those who are learning (and I hope they take comfort that we’ve all tried to untangle this one). It’s going to be a simplification of the science – so my excuses to the chemists amongst us!
Let’s start with acidity. Most canning relies on techniques which kill or suspend the growth of yeasts, mould and bacteria. Acid naturally inhibits many of the nasties so food which is deemed to have high acidity don’t need the amount of processing that non-acidic food does. Acid is measure by pH level from 0-14. Pure water is neutral at 7, acidic substances are closer to 0 and base (alkaline) elements increase upwards from 7.
Food which is under pH level 4.6 is considered to be high acid. This includes almost all fruit and almost no vegetables (tomatoes are close to this ‘magic number’ and it is recommended that you add citric acid or lemon juice to them to increase their acidity).
High-acid foods are safe to be water-bathed, however:
- Use tested recipes. A strawberry is high acid but if you added 3 pieces of bacon for every strawberry, you’re concoction is no-longer high-acid. Of course this is in exaggeration but it helps demonstrate the point. And I have seen some recipes online which tell you that you can preserve bacon jam via waterbath which is (as far as I can tell) some very poor advice, in part due to the lack of acidity.
- When in doubt, check with the pros. My most trusted resource is the National Center for Home Food Preservation (we describe them here and include a link to them in that article).
You do not need to pressure can high-acid foods.
This brings us to low-acid foods – i.e. most vegetables. There are two options with them (we’re ignoring other preserving methods like freezing, infusing, dehydrating and lacto-fermentation for now):
- Increase the acidity
- Pressure can them
Option 1 simply means that we add acid – in the case of tomatoes a small amount of citric acid or lemon juice (as explained at the National Center for Home Food Preservation above) is the most common fix which vegetables like cucumbers become pickles and are submerged in vinegar. These are then water-bathed – the advantages being that they keep their texture better and you need less equipment than pressure canning – the main disadvantage (also an advantage) is that the taste is transformed to a pickle and not the original vegetable.
Pressure canning allows you to use pressure and steam to increase the heat of the processing while canning. This attacks the nasties we mentioned earlier. Pressure canning allows you to preserve vegetables and other low-acid foods (including stocks and meats) so that you can extend your summer food (especially local) through the year.
Rather than repeating a lot of what we’ve said in the past, here’s a few links to start/ help get your head around pressure canning:
- Why should I buy a pressure canner? -> How to decide if this is for you
- Thinking of buying a pressure canner? -> How to select the right one
- Canned Peas -> An example of pressure-canning vegetables.
To conclude;
- High-Acid (most fruit) -> safe for all methods.
- Low-Acid (most vegetables and meat) -> add acid OR pressure can
- For both -> use tested recipes.
Hope that helps!
We love your questions and ideas (here and at the Facebook Community) – they help us know what you want to know and make for easy topic ideas (something that gets more difficult after every post :)).
Happy Monday all.