One of the most important things associated with canning is knowing which foods can be boiling water bath canned and which must be pressure canned to be safely preserved. The bottom line is that high-acid foods like fruits can be safely processed by using the boiling water bath method, while low-acid foods like vegetables and meats must be pressure canned.
The foods that must be pressure canned are low-acid foods with a pH of 4.6 or higher, including vegetables, except for some varieties of tomatoes, green peanuts, meats, poultry, and seafood.
Why Must Certain Foods Be Pressure Canned?
Bacteria exists naturally in the soil where our food is grown, in the water supply, and on the surfaces of most food crops. That bacteria is quite harmless unless the right conditions exist for it to become active, at which time it can produce deadly toxins within 3 to 4 days. The conditions which create the perfect environment for bacteria to grow and become dangerous are as follows:
- They exist on moist food that is considered low acid or food with a pH higher than 4.6.
- The environment contains less than 2% oxygen.
- The temperature falls within the 40℉ to 120℉ range.
Normal food preparation, such as washing and peeling, can reduce the number of bacteria on the surfaces of food but cannot remove all of it. The food is safe to eat, either raw or cooked, because bacteria require a lack of oxygen to produce their deadly toxins. But, the danger exists when foods are canned and stored in airtight containers but have not been properly processed in order to destroy the majority of the bacteria.
In order for foods to be canned or preserved for long-term storage, the bacteria which causes botulism, Clostridium botulinum, must be destroyed so that it doesn’t continue to grow and spoil the food so that it can infect us with food-borne illness. In order to do that, the food must be subjected to heat for a sufficient period of time to destroy that naturally-occurring bacteria.
Related The 6 Types of Foods That Can Be Canned (And 4 That Cannot).
Also important for this process is the amount of acid found in the food. The right combination of acid and heat is required to rid the food of those bacteria.
- For high-acid food like most types of fruit, the heat of boiling water, which is 212℉, for a certain amount of time is sufficient to destroy the bacteria contained in the fruit.
- However, low-acid food, like most vegetables, green peanuts, meats, poultry, and seafood, requires that temperatures of 240℉ to 250℉ be maintained for a designated period of time in order to destroy the bacteria that causes botulism.
In both canning processes, the length of time required depends on the type of food being canned. For example, when making jam by using the boiling water bath method, the length of time required for processing is 10 minutes. But, when canning beets by pressure canning, 30 minutes of processing time is required for a batch of beets in pint jars that are canned by using a dial-gauge pressure canner at an elevation of up to 1,000 feet.
What Is Meant By The Acidity Or pH of Foods?
Not only does food have to be subjected to heat to kill the naturally occurring bacteria, but acid found in food also serves the purpose of blocking the growth of and destroying bacteria.The acid found in food is measured by a method known as pH. On that pH scale, the lower the number on the scale, the higher the pH and the greater concentration of acid found in the food. The higher the number on the scale, the lower the amount of acid found in the food.
- High-acid foods will be those foods that measure 4.6 or lower on the pH scale.
- Low-acid foods are foods with a pH of 7.0 or higher.
Acid in food can be natural, or it can be added. Acid is natural in certain fruits, such as apples and citrus, which are high in natural acid, or it can be added, such as adding lemon juice to blueberry jelly because blueberries are a low-acid fruit or adding vinegar during the pickling process.
For more about low and high-acid foods, check my article called List of Low and High Acid Foods For Canning (With Chart).
Foods That Must Be Pressure Canned
Although high-acid foods can safely be canned by using the water bath canning method, which renders the foods safe by subjecting those foods with their high acid content to 212℉, the temperature at which water boils, for a specific period of time depending on the food, there are some foods that must be pressure canned.
Low-acid foods include all vegetables except for tomatoes, green peanuts, red meats, poultry, and seafood. These foods must be cooked at a certain pressure or PSI (pounds per square inch) for a certain amount of time. That length of time must be adjusted for canners at different elevations.
What Does Elevation Have To Do With Canning?
Elevation affects canning processes because the air at higher elevations is thinner, which makes the boiling point different. The boiling point at elevations up to 1,000 feet is 212℉, while at elevations of over 1,000 feet, the boiling point is 200℉. To adjust for this difference, the food must be boiled longer in the boiling water bath canning process, and a higher pressure must be used in the pressure canning process.
If you are not aware of the elevation in your area, there are apps for your cell phone that can provide you with that information, but there is also information online to help you determine your elevation. They are:
- The USGS (U. S. Geological Survey) provides a searchable map that gives you the exact location of your home address. Simply click on the “Spot Elevation Tool” on the left side of the map to find three different tools that allow you to search by address, by marker, or by specific coordinates.
- Use the tool at https://whatismyelevation.com/. By clicking the “Change Location” text in the center of the page, you are able to type in your address to find your elevation.
How To Adjust For Elevation In Pressure Canning
For Dial-Gauge Pressure Canners
Use the same times as those for 0 to 1,000 ft. but adjust pressure as follows:
- Up to 2,000 feet above sea level, use 11 pounds of pressure.
- From 2,001 to 4,000 feet above sea level, use 12 pounds of pressure.
- From 4,001 to 6,000 feet above sea level, use 13 pounds of pressure.
- From 6,001 to 8,000 feet above sea level, use 14 pounds of pressure.
- From 8,001 to 10,000 feet above sea level, use 15 pounds of pressure.
For Weighted-Gauge Pressure Canners
Use the same times as those for 0 to 1,000 ft. but adjust pressure as follows:
- Up to 1,000 feet above sea level, use 10 pounds of pressure.
- For over 1,000 feet above sea level, use 15 pounds of pressure.
List Of Foods That Must Be Pressure Canned
Here is a list of foods that must be canned by using the pressure canning method.
Meat
- Beef, Chunks, Cubes, Ground, Strips
- Chili
- Wild Game
Poultry
- Chicken
- Rabbit
- Turkey
Seafood
- Clams
- Crab Meat
- Fish
- Oysters
- Smoked Fish
- Tuna
Soups
- Chicken Soup
- Chicken/Vegetable Soup
- Turkey Soup
- Turkey/Vegetable Soup
- Vegetable Soup
- Vegetable Beef Soup
Stocks
- Chicken Stock
- Fish Stock
- Meat Stock
- Turkey Stock
- Vegetable Stock
Vegetables
- Asparagus
- Beans, Baked
- Beans, Fordhook or Limas
- Beans, Green, Pole, or Wax
- Beets
- Carrots
- Corn, Creamed or Whole Kernel
- Greens, Kale, Mustard, Spinach, Turnips
- Mushrooms, Sliced or Whole
- Okra
- Peas, Field
- Peas, Green
- Peppers
- Potatoes, Sweet
- Potatoes, White
- Pumpkin, Cubed
- Succotash
- Winter Squash
Foods That Cannot Be Canned
- Artichokes
- Candy
- Dairy
- Eggplant
- Eggs
- Olives
- Pasta
- Pumpkin Pulp
- Rice
- Starchy Foods
- Sweet Potato Pulp
- Thickeners, Flour, Cornstarch
Below are charts containing the basic pressure canning guidelines for each of the low-acid foods listed in this article. Please note that in most instances, only the information for the hot pack method and the elevation up to 1,000 feet has been included. Complete information for each item can be found on the National Center For Home Food Preservation website.
Dial Guage Pressure Canning Chart
| Food – Hot Pack | Process Time – Pint | Process Time – Quart | PSI – 0-1,000 ft. |
|---|---|---|---|
| MEAT | |||
| Beef | 75 min | 90 min | 11 lb |
| Chili | 75 min | N/A | 11 lb |
| Wild Game | 75 min | 90 min | 11 lb |
| Chicken (w/o bones) | 75 min | 90 min | 11 lb |
| Chicken (w/ bones) | 65 min | 75 min | 11 lb |
| Rabbit (w/o bones | 75 min | 90 min | 11 lb |
| Rabbit (w/bones) | 65 min | 75 min | 11 lb |
| Turkey (w/o bones) | 75 min | 90 min | 11 lb |
| Clams | 70 min | N/A | 11 lb |
| Crab Meat | 80 min | N/A | 11 lb |
| Fish (Raw pack) | 100 min | 160 min | 11 lb |
| Fish, Smoked (raw) | 110 min | N/A | 11 lb |
| Oysters (½ pints or pints) | 75 min | N/A | 11 lb |
| Tuna (½ pints or pints | 100 min | N/A | 11 lb |
| SOUP | |||
| Chicken Soup | 60 min* | 75 min* | 11 lb |
| Chicken/Vegetable Soup | 60 min* | 75 min* | 11 lb |
| Turkey Soup | 60 min* | 75 min* | 11 lb |
| Turkey/Vegetable Soup | 60 min* | 75 min* | 11 lb |
| Vegetable Soup | 60 min* | 75 min* | 11 lb |
| Vegetable/Beef Soup | 60 min* | 75 min* | 11 lb |
| STOCK | |||
| Chicken Stock | 20 min | 25 min | 11 lb |
| Fish Stock | 100 min | 100 min | 11 lb |
| Meat Stock | 20 min | 25 min | 11 lb |
| Turkey Stock | 20 min | 25 min | 11 lb |
| Vegetable Stock | 20 min | 25 min | 11 lb |
| VEGETABLES | |||
| Asparagus | 30 min | 40 min | 11 lb |
| Beans, Baked | 65 min | 75 min | 11 lb |
| Beans, Fordhook or Limas | 40 min | 50 min | 11 lb |
| Beans, Green, Pole, Wax | 20 min | 25 min | 11 lb |
| Beets | 30 min | 35 min | 11 lb |
| Carrots | 25 min | 30 min | 11 lb |
| Corn, Creamed/ Hot & Cold Pack | 85 min | Dense – Not recommended | 11 lb |
| Corn, Whole Kernel/Hot & Cold Pack | 55 min | 85 min | 11 lb |
| Greens | 70 min | 90 min | 11 lb |
| Mushrooms | 45 min/ Half Pint | 45 min/Pint | 11 lb |
| Okra | 25 min | 40 min | 11 lb |
| Peas, Green/Hot & Cold Pack | 40 min | 40 min | 11 lb |
| Peas, Field | 40 min | 50 min | 11 lb |
| Peppers | 35 min/ Half Pint | 35 min/Pint | 11 lb |
| Potatoes, Sweet/Pieces or Whole | 65 min | 90 min | 11 lb |
| Potatoes, White/Chunks or Whole | 35 min | 40 min | 11 lb |
| Pumpkin, Cubed | 55 min | 90 min | 11 lb |
| Succotash/ C |