Thursday, July 9, 2015

Alititude Adjustments for Canning

Since canning season is going to be in full swing pretty soon, I decided to start the year off by providing some basic but useful information.

Today's topic: Altitude and Canning
This post will go over why altitude even matters when dealing with canning, and what changes need to take place based on where you live.  I will also go over the altitude differences between a steam or water bath canner compared to a pressure canner.

Just as it does in baking, higher altitude affects home canning recipes.  As elevation (altitude above sea level) increases, water boils at lower temperatures that are less effective for killing harmful spoilage microorganisms.

Most canning recipes include instructions for elevations of 0 - 1,000 feet, or an altitude at which water boils at 212 degrees F (100 degrees C).  Therefore, it is very important when using a new recipe to be aware of your own elevation, as well as the elevation of where the recipe is coming from.

When preserving at elevations higher than 1,000 feet, the processing time needs to be adjusted in order to extend the food's exposure to adequate heat to destroy microorganisms.

Below is a chart of common cities in Utah and their elevation:
Utah Elevations
Cedar City: 5,622 feet
Moab: 4,555 feet
Ogden: 4,473 feet
Provo: 4,497 feet
Salt Lake: 4,227 feet

For those outside of Utah, or if you are unaware of the altitude level at your home, local elevation information is often available through U.S. county extension offices and through government health or municipal agencies in Canada.  Aviation charts list elevation as well, so checking with your local airport is another good way to determine your general altitude.

So, how do you accommodate for altitude changes in terms of canning?
The method of adjustment differs between high and low acid foods.

High-acid foods are described as anything with a pH level of 4.6 or lower.  These types of foods can be safely heat-processed in a steamer or waterbath canner.  These foods consist mostly of fruits, jams, jellies and fruit spread.
Plain tomatoes sit on the borderline between high and low acid status, so they require acidification to be safely processed as described above (the addition of vinegar or lemon juice).

Low-acid foods have a pH of 4.7 or higher, or have very little natural acid.  They include vegetables, meats, poultry and seafood, as well as soups, stews, meat sauces, and some tomato mixtures.

When canning, each group requires a different type of adjustment:
For high-acid foods processed in a steam or waterbath canner, the processing time is increased.
For low-acid foods processed in a pressure canner, processing time remains constant, but the level of pressure is increased.

Below are two adjustment charts on how to modify original recipes (0 - 1,000 ft. altitude) to make them safe for where you live:

Altitude Adjustment Chart for High-Acid Foods
(Steam or Boiling-Water Bath Canning)

Increase in Processing Time
1,001 – 3,000
306 – 915
5 minutes
3,001 – 6,000
916 – 1,830
10 minutes
6,001 – 8,000
1,831 – 3,050
15 minutes
8,001 – 10,000
2,441 – 3,050
20 minutes

Altitude Adjustment Chart for Low-Acid Foods
(Pressure Canning)

0 – 1,000
1 – 305
1,001 – 2,000
306 – 609
2,001 – 4,000
610 – 1,219
4,001 – 6,000
1,220 – 1,828
6,001 – 8,000
1,829 – 2,438
8,001 – 10,000
2,439 – 3,048

So basically, if you have an original recipe for high-acid foods that needs to be processed for 15 minutes, in our Utah location, you would process for a total of 25 minutes.

And if you were using a pressure canner you would simply increase the lbs. to 13.

Altering your recipes to suit your altitude ensures the safety of your canned food; greatly reducing the risk of botulism, mold and yeast growth, bacteria and enzyme growth, and therefore ensuring quality food.

Source: The Ball Complete Book of Home Preserving, Edited by Judi Kingry and Lauren Devine

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