When you are used to canning at home, then the canning headspace concept is easy for you. However, you would be surprised at how many people don’t understand the necessity for this space.
If you have screwed up your canning before, then you know that not leaving enough headspace while processing can cause the vacuum seal to break, and your food to spoil.
Don’t worry, though, there are many things you can do to get the canning headspace right:
Fact #1: Depending on what you are canning, there are some general rules to follow
While it is true that no canning process is the same, there are some things that you can keep in mind as guidance at any time.
If you are canning jellies, jams, spreads, or fruit juice, leaving about 0.5 cm of headspace is ideal. When you are canning tomatoes, fruits, pickles, or condiments, you want to leave double that, so at least 1 cm. Foods with low acid will require more headspace, so 2-3 cm is a good start. And if you are planning on freezing things, always leave at least 1 cm of headspace.
Fact #2: Sometimes, you can miscalculate the canning headspace and things won’t turn out badly
Even though it is important to have enough headspace for your canned goods, the truth is, sometimes you will get it wrong. The biggest problem is that not having headspace prevents the seal from forming, which can become a food safety issue.
Fact #3: Too much or too little canning headspace is not the same
What happens if you leave too little headspace? Your food will expand, and bubbles will accumulate, leaving traces at the rim of the lid and preventing the jar from sealing. This deposit can also cause microorganisms to grow at the top.
On the other hand, leaving too much headspace can cause food at the top to lose its color. If you leave more headspace than advised there may also be too much air, which ultimately affects your processing time, and you may not be able to push all the air out of the jar.
Fact #4: Make sure there are no visible bubbles either
Many beginner canners realize their mistake too late, but if you don’t get rid of bubbles on time, you will end up with a false headspace. Bubbles will always form, either because they are trapped between the food particles, or pockets form in your liquids, like jam or chutneys. Once you start processing your jars, these bubbles will rise to the top, causing the food levels to sink to the bottom, and giving you a false idea of what headspace you have.
This is the moment when you need to de-bubble, as you will see that you had much more space occupied by these trapped bubbles that could have prevented the correct seal. Another key point here is that leaving the bubbles may not leave enough space for your food to expand when you are processing the jars, causing pressure to build up, and ultimately preventing the correct sealing and storage.
Fact #5: You can use a spatula to remove bubbles
Now you know that you have to account for bubbles and remove them, but how can you do this? You can simply use a spatula or a similar tool and begin moving it up and down while you turn the jar. This process will get rid of the bubbles, but may also leave you with too much space. If this is the case, don’t hesitate to add water or liquid to the canned product.
Fact #6: Don’t panic if you start with one headspace level and finish with another
It is normal for your starting headspace to be different from the end one. If you are packing foods into hot jars, once these cool off, the food may shrink and fall to the bottom. Air spaces in raw food will also cause more headspace as you process hot jars, which create a bigger gap. Keep in mind too, that If you are siphoning, you may lose liquid in the jars. Siphoning increases when you pack raw food and heavy syrups.
To reduce the loss of liquid, allow your jars to cool for 5 minutes after the processing and before you remove them from the canner. Once the jar is sealed, though, losing liquid can’t be fixed, and it will likely not affect your final product as long as it is stored and sealed properly.
Understand canning headspace enough to can at home?
Headspace is something that home preservers and canners love to talk about, but not everyone knows the ins and outs of it. These tips can help you troubleshoot every time you are getting ready to process your jars and seal them. When in doubt, it is best to research how much headspace to leave; otherwise, you may end up with a spoiled product that you have to throw out.