Utah State University: Canning and Preserving

It is also that time of year when many folks turn to preserving food at home—so they can enjoy the fresh flavor and wonderful taste throughout the winter.

The ability to preserve your food is a great skill to have, and we have seen an increase in home food preservation this year, as crops are abundant, and the cost of food and gas are on the rise. But are we doing it safely? There is a lot more to food preservation then simply putting food in a bottle and getting the lid to seal. Teresa Hunsaker, Family and Consumer Science Educator with USU Extension, Weber State University shows us how.

Proper canning practices include:

• carefully selecting and washing fresh food,

• peeling some fresh foods,

• hot packing many foods,

• adding acids (lemon juice or vinegar) to some foods—tomatoes, Asian pears, salsa, etc.,

• using acceptable jars and self-sealing lids,

• processing jars in a boiling-water or pressure canner for the correct period of time and pressure for this altitude—depending on the type of food.
Collectively, these practices remove oxygen; destroy enzymes; prevent the growth of undesirable bacteria, yeasts, and molds; and help form a high vacuum in jars. Good vacuums form tight seals which keep liquid in and air and microorganisms out.

The main culprit we are trying to deal with is a pretty clever little microorganism that is a spore—and produces a toxin (in the right conditions) that quite literally can be deadly.

These bacteria exist either as spores or as vegetative cells. The spores, which are comparable to plant seeds, can survive harmlessly in soil and water for many years. When ideal conditions exist for growth, the spores produce vegetative cells which multiply rapidly and may produce a deadly toxin within 3 to 4 days of growth in an environment consisting of:

• a moist, low-acid food

• a temperature between 40° and 120°F

• less than 2 percent oxygen (anaerobic—without air)
Botulinum spores are on most fresh food surfaces. Because they grow only in the absence of air, they are harmless on fresh foods.

Most bacteria, yeasts, and molds are difficult to remove from food surfaces. Washing fresh food reduces their numbers only slightly. Peeling root crops, underground stem crops, and tomatoes reduces their numbers greatly.


Canners: For water bath canning a pan made for this purpose should be used. It should also be large enough to allow quart bottles to be completely submerged in water. A rack to keep the bottles from sitting right on the bottom should also be used.
Water should cover tops of jars by 1-2 inches, when they are submerged in the water. Processing time begins once the water comes back to a boil after bottles are completely submerged.

For pressure canning a pressure canner must be used.

Jars: Regular and wide-mouth Mason-type, threaded, home-canning jars with self-sealing two piece lids are the best choice. They are available in ½ pint, pint, and quart sizes. The standard jar mouth opening is about 2-3/8 inches. Wide-mouth jars have openings of about 3 inches, making them more easily filled and emptied. Half-gallon jars may be used for canning very acid juices only. Regular-mouth decorator jelly jars are available in 8 and 12 ounce sizes. With careful use and handling, Mason jars may be reused many times, requiring only new lids each time. When jars and lids are used properly, jar seals and vacuums are excellent and jar breakage is rare.
Mayonnaise-type jars are not recommended for use with foods to be processed in a pressure canner because of excessive jar breakage. This type jar may be used for foods in a water bath canner, however, you should expect more seal failures and jar breakage. These jars have a narrower sealing surface and are tempered less than Mason jars, and may be weakened by repeated contact with metal spoons or knives used in dispensing mayonnaise or salad dressing. Other commercial jars with mouths that cannot be sealed with two-piece canning lids are not recommended for use in canning any food at home.

Lids: The common self-sealing lid consists of a flat metal lid held in place by a metal screw band during processing. The flat lid is crimped around its bottom edge to form a trough, which is filled with a colored sealing compound. When jars are processed, the sealing compound softens and flows slightly and molds to cover the jar-sealing surface, yet allows air to escape from the jar. The lid then forms an airtight seal as the jar cools.
Buy only the quantity of lids you will use in a year. To ensure a good seal, carefully follow the manufacturer’s directions in preparing lids for use. Examine all metal lids carefully. Do not use old, dented, or deformed lids, or lids with gaps or other defects in the sealing compound.

Canning High Acid Foods

Foods with a high enough acidity (pH of 4.6 to 2.0) can be safely canned in a water bath canner—using a scientifically developed and up to date recipe. This includes pickled foods, fruits, and tomatoes or tomato combinations (with enough acidity). This method is more popular, least intimidating, and “easiest”—but not safe for low acid foods—such as meats, veggies, stews, soups.

Follow these steps for successful boiling-water canning:

1. Fill the canner halfway with water.

2. Preheat water to 140°F for raw-packed foods and to 180°F for hot-packed foods.

3. Load filled jars, fitted with lids, into the canner rack and use the handles to lower the rack into the water; or fill the canner, one jar at a time, with a jar lifter.

4. Add more boiling water, if needed, so the water level is at least 1 inch above jar tops.

5. Turn heat to its highest position until water boils vigorously.

6. Set a timer for the minutes required for processing the food.

7. Cover with the canner lid and lower the heat setting to maintain a gentle boil throughout the process schedule.

8. Add more boiling water, if needed, to keep the water level above the jars.

9. When jars have been boiled for the recommended time, turn off the heat and remove the canner lid.

10. Using a jar lifter, remove the jars and place them on a towel, leaving at least 1-inch space between the jars during cooling.

Canning Low Acid Foods in a Pressure Canner

A scientifically tested recipe for low acid foods must also be used. Just because one is using a pressure canner to preserve low acid foods does not mean that all “home” concoctions will be safe if pressure canned!! Many people think that pressure canning will be the answer to all of their other fixin’s. This is not the case. Safety considerations also included in the science based recipe include food density, heat penetration(based on thickness and viscosity, etc.), starting temperature, standard bacteria load, acidity, and others. In other words, to can your favorite chili recipe just because you have a pressure canner would not advised.

Follow these steps for successful pressure canning:

1. Put 2 to 3 inches of hot water in the canner. Place filled jars on the rack, using a jar lifter. Fasten canner lid securely.

2. Leave weight off vent port or open petcock. Heat at the highest setting until steam flows from the petcock or vent port.

3. Maintain high heat setting, exhaust steam 10 minutes, and then place weight on vent port or close petcock. The canner will pressurize during the next 3 to 5 minutes.

4. Start timing the process when the pressure reading on the dial gauge indicates that the recommended pressure has been reached, or when the weighted gauge begins to jiggle or rock.

5. Regulate heat under the canner to maintain a steady pressure at or slightly above the correct gauge pressure. Quick and large pressure variations during processing may cause unnecessary liquid losses from jars. Weighted gauges on Mirro canners should jiggle about 2 or 3 times per minute. On Presto canners, they should rock slowly throughout the entire process.

6. When the timed process is completed, turn off the heat, remove the canner from heat if possible, and let the canner depressurize on its own. Do not force-cool the canner. Forced cooling may result in food spoilage. Cooling the canner with cold running water or opening the vent port before the canner is fully depressurized will cause loss of liquid from jars and seal failures. Force-cooling may also warp the canner lid of older model canners, causing steam leaks. Depressurization of older models should be timed. Standard-size heavy-walled canners require about 30 minutes when loaded with pints and 45 minutes with quarts. Newer thin-walled canners cool more rapidly and are equipped with vent locks. These canners are depressurized when their vent lock piston drops to a normal position.

7. After the canner is depressurized, remove the weight from the vent port or open the petcock. Wait 2 minutes, unfasten the lid, and remove it carefully. Lift the lid away from you so that the steam does not burn your face.

8. Remove jars with a lifter, and place on towel or cooling rack, if desired.
Once bottles are cooled (24 hours) and have been checked for sealing, they can be washed down, the ring removed, labeled and placed on your storage shelves.
There are so many great foods you can preserve!! Making sure you have the correct equipment and a scientifically sound recipe are the main things to keep in mind. The USDA has a terrific publication called Complete Guide to Home Canning. Of course, there is still the Ball Blue Book, and there is also another excellent source called So Easy To Preserve—from the University of Georgia and USDA.
A good internet source for canning information is: www.uga.edu/nchfp.

They have so many tips, hints, tutorials, educational writings, and RECIPES!! The source is the National Center for Home Food Preservation. Of course, there is always Utah State University Extension website, www.usu.edu/foodsafety.

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