Basics of Water Bath canning
Image: iStock
What is water bathing (or water bath canning)?
Some people don’t consider water bathing to be “ canning” at all, however in my mind, a processing step of heating food in jars is canning - whether that is water bathing, steam canning, pressure canning, or even Fowlers Vacola method.
Water bath canning involves putting jars of food into a pot of water, large enough so that a couple of centimetres (or an inch) of water will come over the top of the jar lids. With jars inside, the pot is brought to a boil and held at a boil for a specified period. That time will vary according to your recipe.
What does water bath canning do to my food?
The water bathing process will bring the jars and their contents up to boiling point, being 100˚C (212˚F) and keeps them there for a specified period. This will:
Kill off most of the potential nasties (bacteria, yeast etc) that may be lurking in your jars (keep reading!).
Pushes air out of the jars, which helps reduce spoilage (oxygen is not a friend of long term storage).
By pushing out the air, creates a vacuum that will seal your jar lid to the jar.
What foods are suitable for water bathing?
Only “high-acid” foods are suitable for water bathing. “High acid foods”, in a canning context, have a pH below 4.6. Remember, high acid = low pH.
The reason only high-acid foods are suitable for water bath canning, because the Clostridium botulinum, that bacteria that can give you the very nasty botulism, can survive temperatures in excess of 100˚C (212˚F). However, C.botulinum can not survive in an acidic environment. Whilst botulism is not common, it is a serious illness - it can kill you.
So when we are water bathing, the acid in our food - either naturally occurring or added in the form of vinegars etc - is key.
Examples of high-acid foods are:
Pickles
Most Salsas
Most fruit
Jams and Jellies
Tomatoes (with lemon juice added)
The process of water bath canning
Prep your food or recipe.
Prep your jars and lids.
Check each jar for any cracks or chips on the rim.
If you are going to be processing in a water bath for 10min or more, you don’t need to sterilise your jars & lids, they just need to be nice & clean.
If your recipe calls for water bath processing for less than 10min, you will need to sterilise your jars - the easiest way will be to simmer them in your water bath pot for 10min before filling.
Prep your water bath - place your trivett (or alternative) in pot, fill your water bath pot with hot water and pre-heat.
If you are raw packing your food, pre-heat the water in your canner to 60˚C (140F).
If you are hot packing your food, pre-heat the water in your canner to 82˚C (180˚F).
This is important to avoid thermal shock - cool food into cool jars into cool(ish) canner, OR hot food into hot jars into hot canner.
It is also important not to have your canner at a rolling boil when you want to put your jars in - the jars take some time to come up to temp, plus it’s very unsafe trying to load jars into a canner that is at a boil.
Fill your jars, ensuring you maintain the correct headspace as indicated by your recipe.
Debubble the jars.
Clean rims - a cloth dipped in white vinegar removes any food residue.
Place lids on jars and screw on rings to “fingertip tight”.
Place jars into canner.
When the water comes to a rolling boil, your processing time has begun.
When processing, keep an eye on your pot and top up with boiling water as required to ensure the minimum 2cm (1 inch) of water over the jars is maintained throughout the entire processing time.
While processing, ensure that you have a cooling area set up - this needs to be a breeze-free space where the jars can sit undisturbed for up to 24 hours.
Ensure you protect your bench top or tabletop, as the jars are very hot - cork mats or an old thick bath towel can work.
When the processing time is complete, turn off the heat and wait a few seconds for the water to stop boiling. Remove jars from the pot and place them in your cooling area.
NB ensure you don’t tip your jars when removing them from the pot - and do not place them upside down to cool! Jars aren’t always sealed when they come out of the pot; they seal as they cool. Tipping them may result in food making its way between the jar and the lid and may compromise your seals.
Leave your jars to cool for 12-24 hours before removing rings and checking your seals.
If any jars have not sealed, put them in the fridge to eat over the coming days. You can also re-process within 24 hours; however, think about what food you are canning - another processing round may turn the contents of your jars to mush!
A special note on steam canning
Steam canners are considered a safe alternative to water bath canning. I have not used a steam canner - yet! This is the next thing on my list of kit to buy. Steam canners have the advantages of using less water, therefore less energy to heat and are significantly lighter. Steam canners can only be used for processing times up to 45 minutes. Other than that, from what my research has shown, the processing times, sterilisation requirements etc are the same as per water bath canning.
References
Anon. 2009. “General Canning Information”. National Center for Home Food Preservation.
Boyer, R. & Schonberger, H.L. 2022. “Boiling Water Bath Canning”. Virginia Cooperative Extension.
McGlynn, W. 2016. “The Importance of Food pH in Commercial Canning Operations”. Oklahoma State Extension.