How to Can Food
Home canning is a time-tested way to preserve all kinds of different foods. So whether the garden harvest has just come in, you picked up an extra bushel of vegetables at the farmer’s market, or you’d like to give holiday jams and jellies as presents this winter, we’re here to help. We’ll lay out the information you need to get started canning food the right way, saving you time and money while putting up food for the rest of the year.
We’re going to review canning basics, give you a checklist of items you’ll need to get started, touch on common issues and problems, and share a few tips and tricks.
Canning preserves your food’s nutrients, flavor and prevents the growth of harmful bacteria through a heating process which vacuum seals your food in jars. For a fraction of the cost of store-bought food, you can create tasty, high-quality food that lasts for months or even up to a year. This includes fruits, jams, jellies, pickles, salsas, sauces, vegetables, meats, poultry, and even seafood. You control how much salt goes into each recipe, and you get the peace of mind that comes from knowing your family isn’t eating unwanted preservatives. You can get started for a relatively small investment, adding on more equipment as your desire to can food grows.
There are several items you’ll need for either type of canning. They are:
- Rack - The rack sits down in your water bath and keeps your jars upright. It is also useful during the sterilization process.
- Glass Jars - Use jars specifically designed for canning, they are available in many sizes.
- Ladle, spoon, and spatula - You’ll need these tools to measure and portion the food into the jars, and pack them in correctly.
- Canning Bands and Lids - Always use new lids to ensure a good seal.
- Canning Funnel - A funnel helps you get more food into the jar and keeps those rims clean. More on the importance of that later.
- Lid Lifter or Sterilizing Rack - Lift flat lids out of boiling water without fumbling or burning your fingers.
- Jar Lifter - Helps you lift heated jars out of boiling water or a pressure canner.
- Jar Wrench - used for loosening and tightening lids.
- Towels or Cooling Rack - Gives you a place to set hot jars for cooling.
- Water Bath Canner - You can use a large pot-type canner, large enough to hold several jars at once or a purpose-built multi-use canner that includes a heating element.
- Pressure Canner - A pot, lid, and valve combo specifically designed for pressure canning. Some also double as pressure cookers and water bath canners, like this Pressure Canner.
Types of Canning
When canning at home, you can choose one of two methods. The two methods are very similar, the biggest difference being the peak temperature food being canned reaches during the process. Water bath or boiling water canning heats food to 212℉, while pressure canning heats food to 240℉. The need for different temperatures is driven by pH, or a measure of acidity, and the natural ability of acidity to inhibit the growth of botulism. A lower pH indicates more acidity in the food, while a higher pH indicates food that is more alkaline and has less acidity.
- Water Bath Canning - This method is suitable for acidic foods with a pH below 4.6 (like lemons, limes, grapefruit, blueberries, strawberries, raspberries, oranges, apples, cherries, peaches, and pears.) This method is also appropriate for foods that have been made acidic by adding vinegar, lemon juice, or citric acid (examples include salsas, tomatoes, pickled foods, and some fruit preserves.)
- Pressure Canning - Low-acid foods (with a pH above 4.6), should be pressure canned, which raises the temperature of the food to 240℉. Most vegetables, meats, fowl, and seafood should be pressure canned.
Why The Difference?
pH drives the need for two types of canning, as botulism cannot grow in foods with a pH below 4.6. For any low-acid foods with a pH above 4.6, canning at 240℉ destroys the spores that cause botulism, thereby making them shelf-stable and safe to store at room temperature.
- Start by cleaning and pre-heating your lids and jars. You’ll want to wash them both in warm soapy water, rinse, then warm the jars in a pot full of hot water, while the lids are warming in a separate pot of hot water. Keep the water below boiling, as the canning process will sterilize both lids and jars, and boiling water can actually prematurely melt the compound on the inside of the lid that provides the canning seal.
- Fill the warm jars with your warm processed food. Leave enough headspace at the top of the jar to form a vacuum when the food cools, checking the specific of your recipe.
- Use a spatula to release the air bubbles that may be trapped in your food or at the sides of the jars, and adjust the headspace as necessary.
- Wipe down the rim of the jar to ensure a good seal, place the lid over the jar, and screw on a metal ring. Be careful not to over or under-tighten the lid, as both can ruin your can. You want to tighten to the point of resistance and then ⅛ of a turn more.
- Heat and process your jar per your recipe instructions, using either your water bath canner or your pressure canner.
- Remove your jars from the canner and cool them for 24 hours on the counter with two towels between the counter and the jar. The towels prevent thermal shock from a hot jar on a cold counter, which can crack the jar and ruin all your hard work.
- Check the lids for proper seal by pressing the button on the lid. If it presses and pops back up, the jar didn’t seal. This food should be refrigerated and eaten first. For more on failure to seal, see the common issues below.
- Store your canned food in a dark, cool, dry place, enjoying them within a year.
- Failure to Seal - The “pop” indicates a sealed lid. You’ll hear this sound while the jars are cooling, and you can test the seal by pressing the button in the center of the lid. If it still springs up and down, the jar didn’t seal. If you have a jar that didn’t seal, you can either refrigerate and eat the food within the next few days, freeze the food, or replace the lid and re-process the jar. Although, re-processing is hard on some foods and may not be the best option. The cause of the failed seal could be several things. Failure to clean the rim of the jar can prevent the lid from sealing if there was food between jar and lid. Too little headspace can prevent the vacuum from forming, and a lid that’s either too tight or too loose can interfere with the seal. Attempting to reuse lids can cause this problem; always use new lids to ensure a good seal.
- Cracking or exploding jars - Just like you don’t want to put hot jars on a cold counter, you shouldn’t put hot food into cold jars or heat your jars in the oven. These can all cause your jars to break. Use a towel to insulate the jars from the counter and preheat your jars in a water bath.
- Color changes - While some color changes, (like pink or blue in apples, peaches, or pears) are natural and harmless, exposure to light or over processing can cause color changes in canned food.
- For other issues, more tips and tricks, and recipes and ideas, check the USDA Canning Guidelines.