Canning Temperatures and Processing Times

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Canning - Food Acidity
| Canning - Temperatures and Processing Time

The temperatures and processing times used when canning vegetables and fruit are determined by many factors. The food acidity, how the jars are packed, and canning method being used all determine the processing time, temperatures, and PSI when canning. The information below will help explain some of the factors that need to be considered when canning.


Canning - Food Acidity

There are two basic methods for canning, boiling-water-bath and pressure canning. The method used is normally determined by whether the food being canned has a high acidity level or a low acidity level.

High-Acid Foods: In high-acid foods, such as tomatoes, fruit and pickles, the growth of the Clostridium botulinum bacteria, which is heat resistant, is prevented by the high acidity level or the acidity allows the botulism spores to be destroyed quicker when boiled. This allows them to be processed using a boiling-water-bath at 212°F. The most common forms of spoilage microorganisms in acid foods are mold and yeast, which are destroyed by the boiling-water-bath.

Tomatoes generally have an acidity level that is high enough to be considered an acid food but there are some varieties that have an acidity level that is slightly under the level required. Tomatoes that have a slightly lower acidity level can be made acidic by adding lemon juice or citric acid. The USDA suggests adding lemon juice or citric acid to all tomatoes to ensure acidity levels. They are then safe to process using the boiling-water-bath.

Low-Acid Foods: Low-acid foods, such as vegetables, seafood, meats, and poultry must be pressure canned at 240°F to eliminate and prevent the growth of bacteria called Clostridium botulinum. The botulinum spores are very resistant to heat so processing at the higher temperatures provides a way to destroy these spores. If the low acid foods were processed in a boiling-water-bath canner, they would have to be processed for a length of time ranging from 7 to 12 hours. Processed at the 240° to 250°F using a pressure canner takes 20 to 100 minutes, depending on the type of food, size of jars, and the way it is packed.

The chart below shows which foods are considered high acidity and which are low acidity.

High Acidity Foods

Using Boiling-Water Bath or
Pressure Canning (for less processing)

Low Acidity Foods

Using Pressure Canning Only

Apples Plums Artichokes (Jerusalem) Mushrooms
Apricots Raspberries Asparagus Okra
Blackberries Rhubarb Beans (green or yellow) Parsnips
Blueberries Strawberries Beets Peas
Cranberries Pineapple Broccoli Peas (snap)
Cherries Tomatoes (with acid added) Brussels Sprouts Peppers
Cucumbers (pickled)   Cabbage Potatoes
Grapefruit   Carrots Pumpkin
Grapes   Cauliflower Spinach
Nectarines   Corn Squash (summer)
Oranges   Eggplant Squash (winter)
Peaches   Figs Sweet Potatoes
Pears   Lima Beans  


Canning - Temperatures and Processing Times

Using the proper processing temperature and time is very important when canning foods to ensure that the processed food will be safe to eat. If not processed properly the food will spoil. There are several factors that affect the amount of processing time required. Some of these factors are listed below:

  • The size and shape of the jars. Less time is needed for smaller jars.
  • Whether they have been raw packed or hot packed.
  • The amount of liquid in the jars. More liquid will allow the jar contents to heat more quickly.
  • The size of the food being processed. Smaller pieces will heat faster.
  • The canning method being used. Pressure canning will be faster.
  • The altitude in your area. See at the bottom of each chart for instructions on how much to adjust the processing time for altitudes above sea level.

All of these factors determine the canning method, processing time and PSI (pounds per square inch) of pressure to be used. Be sure to follow all canning instructions very carefully. It is important to adjust the processing times when you are at a higher elevation. At sea level, water boils at 212°F but as the elevation increases water will boil at lower temperatures. The temperatures at which water boils at the higher elevations are not sufficient for killing bacteria. To compensated for the lower boiling temperatures, the processing time for boiling-water-bath canning needs to be increased and for pressure canning the PSI needs to be increased to destroy the harmful bacteria. Shown below are some charts with processing information and the adjustments that need to be made in processing time for higher elevations. If you are unsure of what the elevation is in your area, you can call your local county extension office to request this information.

High Acid Foods - Boiling-Water-Bath Canning Method

Headspace:

Leave 1/2 inch headspace on all high acid foods with two exceptions. When canning strawberry jam - leave 1/4 inch headspace. When canning grapes - leave 1 inch headspace.

Food Type Pack Method Process Time - Minutes
Pint Jars Quart Jars
Apples Hot 20 20
Apricots Raw
Hot
25
20
30
25
Blackberries Raw
Hot
15
15
20
15
Blueberries Raw
Hot
15
15
20
15
Cranberries Hot 15 15
Cherries Raw
Hot
25
15
30
20
Cucumbers (pickled in vinegar brine) Raw 10 15
Grapefruit Raw 10 10
Grapes Raw
Hot
15
10
20
10
Nectarines Raw
Hot
25
20
30
25
Oranges Raw 10 10
Peaches Raw
Hot
25
20
30
25
Pears Raw
Hot
25
20
30
25
Plums Raw
Hot
20
25
20
25
Raspberries Raw
Hot
15
15
20
15
Rhubarb Hot 15 15
Strawberry Jam Hot 5  
Pineapple Hot 15 20
Tomatoes - Juice (with acid added) Hot 35 40
Tomatoes - Whole or halved - No Liquid Added (with acid added) Raw 85 85
Tomatoes - Crushed (Quartered) - No Liquid Added (with acid added) Hot 35 45

High Altitude:

The processing times above are for canning at sea level. Adjust as shown below:

Processing Time at
Sea Level
Adjusted Processing Time
20 Minutes or Less Add 1 minute per 1000 ft. in elevation
Over 20 Minutes Add 2 minutes per 1000 ft. in elevation.

When using a pressure canner to process high acid foods, your processing time is much shorter than when processing with the boiling-water-bath. When processing at higher elevations the processing time can remain the same as what is used at sea level but the PSI (pounds per square inch) needs to be increased to make up for the lower internal temperature of the canner. Do not begin counting the processing time until the canner has reached its required pressure reading.

High Acid Foods - Dial Gauge Pressure Canning Method

Headspace:

Leave 1/2 inch headspace on all high acid foods listed below. At higher elevations, the steam in the headspace will expand more than at elevations below 1000 feet. To allow for this expansion, it is suggested that you increase the headspace by 1/8 inch for each 1000 feet above see level, not to exceed 1 inch on pint jars and 1 3/4 inches on quart jars.

Food Type Pack Method

Process Time(minutes)

PSI
(pounds per square inch of pressure)
Pint Jars Quart Jars Under
2000 ft.
2001 to 4000 ft. 4001 to 6000 ft. 6001 to 8000 ft.
Apples Hot 8 8 6 lb. 7 lb. 8 lb. 9 lb.
Apricots Raw
Hot
10
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Blackberries Raw
Hot
8
8
10
8

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Blueberries Raw
Hot
8
8
10
8

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Cherries Raw
Hot
10
8
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Grapefruit Raw
Hot
8
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Nectarines Raw
Hot
10
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Oranges Raw
Hot
8
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Peaches Raw
Hot
10
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Pears Hot 10 10 6 lb. 7 lb. 8 lb. 9 lb.
Plums Raw
Hot
10
10
10
10

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Raspberries Raw
Hot
8
8
10
8

6 lb.
6 lb.

7 lb.
7 lb.
8 lb.
8 lb.
9 lb.
9 lb.
Rhubarb Hot 8 8 6 lb. 7 lb. 8 lb. 9 lb.
Tomatoes - Juice (with acid added) Hot 20 15 6 lb. 7 lb. 8 lb. 9 lb.
Hot 20 15 11 lb. 12 lb. 13 lb. 14 lb.
Tomatoes - Whole or halved - No Liquid Added (with acid added) Raw 40
40 6 lb. 7 lb. 8 lb. 9 lb.
Raw 25 25 11 lb. 12 lb. 13 lb. 14 lb.
Tomatoes - Crushed (Quartered) - No Liquid Added (with acid added) Hot 20 20 6 lb. 7 lb. 8 lb. 9 lb.
Hot 15 15 11 lb. 12 lb. 13 lb. 14 lb.

Weighted-Gauge Pressure Canning:

When using a weighted-gauge pressure canner, use the chart above for pack methods and processing time. Weighted-gauge pressure canners cannot have the PSI increased by 1 lb. increments, so adjust the PSI as shown below:

PSI from Chart Above Weighted-Gauge PSI Setting
PSI of 6 lb. to 9 lb. 10 PSI
PSI of 11 lb. to 14 lb. 15 PSI
Elevations under 1000 ft. 5 PSI


Low Acid Foods - Dial Gauge Pressure Canning Method

Headspace:

Leave 1 inch headspace on all low acid foods listed below with the exception of lima beans, raw packed. When using the raw packed method for canning with quart size jars, increase the headspace to 1 1/2 inches for small beans and 1 1/4 inches for large beans.

At higher elevations, the steam in the headspace will expand more than at elevations below 1000 feet. To allow for this expansion, it is suggested that you increase the headspace by 1/8 inch for each 1000 feet above see level, not to exceed 1 inch on pint jars and 1 3/4 inches on quart jars.

Food Type Pack Method

Process Time (minutes)

PSI
(pounds per square inch of pressure)
Pint Jars Quart Jars Under
2000 ft.
2001 to 4000 ft. 4001 to 6000 ft. 6001 to 8000 ft.
Artichokes (Jerusalem) Hot 25 25 11 lb. 12 lb. 13 lb. 14 lb.
Asparagus Raw
Hot
30
30
40
40

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Beans (green or yellow) Raw
Hot
20
20
25
25

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Beets Hot 30 35 11 lb. 12 lb. 13 lb. 14 lb.
Broccoli Canning is not recommended. Best to freeze or
pickle for preservation.
Brussels Sprouts Canning is not recommended. Best to freeze or
pickle for preservation.
Cabbage Canning is not recommended. Best kept in cold storage.
Carrots Raw
Hot
25
25
30
30

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Cauliflower Canning is not recommended. Best to freeze
for preservation.
Corn Raw
Hot
55
55
85
85

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Eggplant Canning is not recommended.
Lima Beans Raw
Hot
40
40
50
50

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Mushrooms Hot 45   11 lb. 12 lb. 13 lb. 14 lb.
Okra Raw
Hot
25
25
40
40

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Peas Raw
Hot
40
40
40
40

11 lb.
11 lb.

12 lb.
12 lb.
13 lb.
13 lb.
14 lb.
14 lb.
Peas (snap) Canning is not recommended. Best to freeze
for preservation.
Peppers Hot 35   11 lb. 12 lb. 13 lb. 14 lb.
Potatoes, White Hot 35 40 11 lb. 12 lb. 13 lb. 14 lb.
Pumpkin Hot 55 90 11 lb. 12 lb. 13 lb. 14 lb.
Spinach and Other Greens Hot 70 90 11 lb. 12 lb. 13 lb. 14 lb.
Squash (summer) Canning is not recommended. Best eaten fresh.
Squash (winter) Hot 55 90 11 lb. 12 lb. 13 lb. 14 lb.
Sweet Potatoes Hot 65 90 11 lb. 12 lb. 13 lb. 14 lb.

Weighted-Gauge Pressure Canning:

When using a weighted-gauge pressure canner, use the chart above for pack methods and processing time. Weighted-gauge pressure canners cannot have the PSI increased by 1 lb. increments, so adjust the PSI as shown below:

Elevation Level Weighted-Gauge PSI Setting
Elevations under 1000 ft. 10 PSI
Elevations over 1000 ft. 15 PSI

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