Canning is not difficult, but it’s important to understand the acid level of food and how it plays a role. As much fun as canning is, it’s a bit scientific. We will try to keep the science to a bare minimum, and as basic as we can. We aren’t scientist ourselves, but have done quite a bit of research on this and want to share what we have learned.
To start off, all foods have an acid level.
If you remember the ph-scale from high school chemistry (that was a looong time ago for us!) it runs from 0-14. I might not remember much from High School biology and chemistry, but I remembered 7 is neutral. I’ll admit I had to look up the rest because my memory is just not that great. If you’re like me a simple explanation is best and Science Buddies explained it perfectly. Anything higher than 7 is alkaline anything lower than 7 is an acid. This is also true for our food.
According to Ball’s Official Canning Guide, most fruits like lemons, pickles, apples, peaches and even tomatoes are high acid foods with a ph scale factor between 2-4. Most vegetables like okra, carrots, and green beans are low acid foods, with a ph scale factor between 5-6. Corn and peas are about the only vegetable that is neutral at 7 on the ph scale.
This acid level matters because it tells you which method to use when processing food by canning.
Also, according to Ball’s Official Canning Guide most mold, yeast and bacteria grows in an acid level of between 2-5 on the ph scale. In order to kill those bacteria you must sometimes raise the acid level of the food you are canning. There are two ways to do this. Most recipes call for adding lemon juice to your product to raise the acid level adequate enough for processing. Other recipes require vinegar to do this.
Once your food has a sufficient acid level (around 4.6 on the ph scale) it can be processed using the Water Bathing Method. However, some foods have such a low acid level that you can’t add enough acid to the food, to process by water bathing. The temperature of boiling water simply isn’t hot enough to kill bacteria.
This is when you use the Pressure Canning Method. The pressure builds and the steam and water combined raise the temperature to 240 degrees thus killing all mold, yeast and bacteria in low acid foods. Make sense?
I know it’s confusing, but if you follow your recipe’s instructions, you’ll be just fine. Acid levels are not fun to learn about, but are necessary when preserving food!
~Until Next Time,
Question: What is the acid level of the food you preserve?