Pressure/ Low Acid Canning

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Beginning in the late ‘90s, low acid food canning began making headlines when the Centers for Disease Control (CDC) received reports of botulism outbreaks associated with home canned vegetables. Those outbreaks resulted from home canners who did not follow proper safety and preservation guidelines for canning vegetables and low acid foods.

Considering the severity of the botulism, it is pertinent to follow safe preservation guidelines which starts with using a pressure canner and not a water bath canner. In my profession, I regularly have to guide people away from water bath canners and explain the necessity of a pressure canner.

So let us look at safe preservation guidelines before you start canning low acid foods.

What are low acid foods?

Low acid foods are vegetables, broth, stews, soups, meat-based recipes, spaghetti sauce, mixed dishes, and dairy products.

What equipment do I need?

A pressure canner is the only specialized equipment used to home can low acid foods. Pressure canners are thin-walled kettles that have screw-on lid with a fitted gasket. They also come with removable racks, an automatic vent/cover lock, a vent pipe, and safety fuse. It is important to buy pressure canner with Underwriter’s Laboratory (UL) approval to ensure safety.

The pressure canners come with either a dial gauge or a weighted gauge to regulate pressure within the canner. You should conduct a trial run to get familiar with the new equipment. A very important thing to remember is that PRESSURE COOKERS and INSTANT POTS ARE NOT RECOMMENDED TO CAN LOW ACID FOODS – these can lead to botulism.

Store your pressure canner in dry and airtight packaging. If using dial gauge, make sure to check and recalibrate the dial every few uses. Read your manufacturer’s guidelines while learning to use and store pressure canner.

You will also need mason jars that contains two lids – A metal lid with sealing compound and a metal screwband. The jars are manufactured in different sizes such as half pint, pint, quart, gallon, or with wide mouth.

Canning toolkits are also very helpful in handling your jar while pouring your prepared fruit product and placing it in the canner. It usually contains lid magnet (lifting metal lids), funnel, tongs, bubble wand (for removing air bubbles and measuring headspace), and a jar lifter (to lift and handle hot jars).

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General steps to pressure can low acid foods

  • Sterilize your jars:
    • Wash glass jars and metal screwbands in hot soapy water (if reusing jars). Sterilize it in boiling water for 10 minutes. This step can be skipped if the processing time for canning is longer than 10 minutes.
    • Metal lids with sealing compound: Sterilize sealing lids in a simmering water bath (ONLY FOR ONE USE)
  • Recipe preparation:
    • Prep your ingredients indicated in the recipe. Cut pieces of food items as evenly as possible.
    • Follow tested recipe guidelines without altering the ingredient amount.
  • Preparing the canner:
    • Gas cooktops are recommended for this canning method.
    • If using a dial gauge, make sure it is recalibrated and inspect all parts of the canner such as vent, gauge, gasket etc.
    • Place rack at the bottom of the canner and add about 2-4 inches of water.
    • Start the burner when the recipe is almost prepared and ready to be poured. Leave weight off the vent port/petcock. Once jars are placed inside the canner, you can adjust the water level if needed.
  • Processing:
    • Drain sterilized jars. Use funnel to pour prepared recipe in the jar.
    • Remove the air bubbles using bubble wand and measure and/or adjust the headspace as indicated in the tested recipe. Wipe the jar rim with clean towel without touching the food.
    • Use lid magnet to lift metal lid and place it on the jar. Place metal screwband and finger-tip tighten the lid.
    • Place prepared jars in the canner using jar lifter and cover the canner with the lid.
    • Wait for the steady steam coming from the vent port.
    • Place pressure regulator on the port and let the pressure build. Once the recommended pressure is reached, start recording processing time. Tested recipes will include the processing time based on jar size and altitude.
    • Regulate heat when the pressure fluctuates from the recommended pressure.
    • Once processing time is complete, turn off the burner and let it cool down at least till the canner is completely depressurized and vent lock falls down to its starting position.
    • DO NOT FORCE COOL YOUR PRESSURE CANNER.
    • Wait 10 minutes after depressurizing and then remove the lid away from your face.
    • Remove jars and let it rest the jar on the counter for at least 12 hours.
    • Clean the jars and label it with recipe name and production and expiration date.

What are tested/reliable recipes?

These recipes are lab-tested for time, temperature, and pH to ensure safety of the product if followed diligently. These recipes can be found on USDA’s website, state Extension websites, So Easy to Preserve Book, and the Ball Book on Preserving. You can also participate in University of Maryland Extension’s Statewide Food preservation program to gain hands-on experience. Have Fun Canning!

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