PUBLISHED: 1:49 PM on Wednesday, June 7, 2006
Home canning for preservation

Often, when speaking of home canning as a food preservation method, individuals will tell me that they used to do that but now they use the vacuum packaging machines or sealers. While I agree that this system is an easy way to preserve foods, there are a couple of advantages to canning in jars that quickly spring to mind.

One advantage to preserving foods in jars is that this method offers the best shelf life for the product. This is especially important when considering emergency preparedness and sheltering in place. Emergency situations may result in loss of electricity for extended periods of time which means that refrigerated and frozen foods are subject to quality loss and spoilage. Typically, a full, freestanding freezer will stay at freezing temperatures about 2 days. A half-full freezer will stay at freezing temperatures about a day. Experts advise stocking up on shelf-stable foods which would include commercially and/or home canned goods.

Another advantage to home canning is that it costs less than freezing. In fact, freezing is the most expensive method of preserving food.

If you have foods from last year's harvest stored in your freezer, now is the time to clean it out in preparation for the new season. Whether you freeze berries, home grown produce, game meats, or fish, home canning last year's harvest is beneficial in two ways: 1) it adds foods to your emergency supply, and 2) it creates additional storage space in your freezer.

Microorganisms, such as molds, yeasts and bacteria are the biggest concerns in home canning.

All foods in their natural state contain these microorganisms to some degree. They are what cause food to spoil. Canning interrupts this natural process through heating the food in containers that seal. The heat destroys the potentially harmful microorganisms, air is driven from the container, and a vacuum is formed. This vacuum prevents other microorganisms from entering and recontaminating the food.

There are two methods of canning or processing foods: boiling water and pressure.

The method used is determined by the acidity (pH) level of the food. These are referred to as acid or high acid foods, and low acid foods.

Acid foods are those that contain natural acid. Generally, all fruits are acid. Sauerkraut, rhubarb, and foods to which vinegar is added, such as certain pickles and relishes, also are treated as acid foods.

The boiling water bath canner is used to process acid foods at a boiling water temperature of 2121/4 F. Any large pot with a tight fitting lid can be used as a boiling water bath canner.

The pot should be large enough for the canning jars to be completely immersed and fully surrounded in boiling water with enough room for active boiling.

Low acid foods, such as meat, vegetables including all tomatoes, fish, and game meat, must be preserved in a pressure canner to be safe. The microorganisms that grow in a low acid environment can only be killed by temperatures greater than 2121/4 F. Low acid foods must be heated to a temperature of 2401/4 F before the spoilage and food poisoning bacteria are killed.

This temperature can only be obtained with a pressure canner. It takes 10 pounds of pressure (psi) at sea level to attain 2401/4 F.

There are two types of pressure canners: the weighted gauge and the dial gauge. The weighted gauge can be adjusted to pressures of 5, 10 or 15 pounds.

The dial gauge canner has a dial on top of the lid that allows you to see the pressure and monitor changes visually.

The dial gauge should be tested yearly for accuracy. Weighted gauges do not have to be tested.

Food that has been properly canned will keep indefinitely; but after a year, some chemical changes may occur which could negatively affect the quality of the product. It should be noted that properly canned food has a recommended shelf life of about one year.

Canned goods should be kept in a cool, dark, dry place. Light hastens the oxidation and destroys certain vitamins. Damp storage can cause metal lids and closures to corrode or rust and endanger the seal.

In fact, it's good practice to remove the screw bands from the jars prior to storage to reduce the occurrence of corrosion or rust.

Always check the food for signs of spoilage before tasting. Indications that food has spoiled include:

• Broken seal

• Seepage

• Mold

• Gassiness

• Disagreeable odors

• Spurting liquid when the jar is opened

• Sliminess

• Cloudiness

The Juneau District CES office has up-to-date research-based information for canning both high and low acid foods. Additionally, your pressure canner gauge can be tested for accuracy at the office. We are located at 3032 Vintage Blvd. Ste. 104, or call 465-8756.

Dr. Koukel is the Juneau District Agent for the Home Economics Programs of the UAF Cooperative Extension Service.