Canning is a fun resourceful way to preserve an abundant harvest from your garden, however if it is done incorrectly, home-canned foods can lead to serious and even fatal food-borne illnesses. The following are 10 tips for canning at home safely.
#1 Always start with a clean preparation area, and the fresher the foods are the better. Make sure there is not any damage to any of the jars, such as nicks and cracks. Make sure all of your equipment is sterilized clean and working well.
#2 If you are canning low-acid foods, always use a pressure canner, this includes most vegetable except for tomatoes, seafood, poultry, and meat.
#3 If you use a pressure canner with a dial gauge, have it tested each year. You can also have your pressure canner checked to ensure that the gaskets are in good shape and that vents, safety valves and edges of the lid are clean.
#4 It is important to always use tested recipes that have up-to-date, researched canning times. Good sources of tested recipes include the National Center for Home Food Preservation at nchfp.uga.edu, Extension service websites and companies that produce home canning supplies such as Ball at www.freshpreserving.com.
Recipes from cookbooks, personal internet sites, and older Extension publications should not be used.
#5 You should never alter ingredients in tested recipes, because changing the ingredients in a tested recipe can make that recipe unsafe for home food preservation and consumption.
#6 When you begin to fill your jars, you should always use the correct headspace. (Headspace - the space in the jar that is between the lid and the top of the food or liquid.) Having too much or too little headspace can affect how the lid seals and the quality of the final product.
#7 Once the jars have been processed (canned), you should check the lids within 12 to 24 hours to make sure that they have a good seal. If you have a jar that did not seal properly, the food should be frozen or refrigerated and eating within 48 hours, or you can reprocess it within 24 hours.
#8 Label the lids with the name of the food and date. If you canned more than once that day, you should add a batch number to the label. That way, if you see signs of spoilage, you can identify the batch number and pay special attention to those jars.
#9 To prevent spoilage, store your canned foods in a dark, cool, dry place. If food is stored in a humid place, the moisture can cause the lids to rust which can lead to spoilage. Periodically check your jars for signs of spoilage.
#10 To enjoy the best quality of your canned goods, use them within ONE YEAR.
Spoilage: process of food becoming unsafe or unacceptable for human consumption. Major causes of food spoilage include: microorganisms (germs, mold, yeast), enzymes in fruit and vegetables, bruising and cuts in fresh produce, and insect damage.
When the conditions are right, germs multiply fast!
|Time||# of bacteria|
Food safety is critical when preserving food at home. Follow researched-based, tested recipes and choose the right method of food preservation to reduce spoilage such as, refrigeration, freezing, canning, sweetening and acidifying jellies and jams, pickling and fermenting, and drying. If food preservation is not done right, food spoilage and/or a foodborne illness can happen.
Refrigeration will slow the growth of germs and other microorganisms and slows down the action of fruit and vegetable enzymes that cause spoilage, however it will not preserve foods for a long periods of time. Keep your refrigerator at 40 degrees or cooler to preserve food longer.
Freezing is the easiest method of food preservation and is a safe method for any food. Freezing stops germs from growing, but it does not kill them, and it slows enzyme activity; but it doesn't stop them; blanching stops the enzymes. Keep your freezer at zero degrees or cooler to get the most out of preservation.
Canning when done right, kills the germs and causes a vacuum that seals the lids. There are two types of canning: boiling water bath and pressure canning. The pH of a food determines which canning method to use. If proper canning methods are not followed, it can lead to food spoilage or serious foodborne illness.
Sweetening and acidifying (jams and jellies) use sugar which prevents the growth of germs. It binds with water so germs can't use it. Lemon juice and/or citric acid are used to add flavor and helps gel formation. Long-term storage of jams and jellies requires canning.
Pickling uses acids (naturally present or added) to lower the pH of a food. This prevents the growth of germs that cause food to spoil and/or foodborne illness. Long-term storage will require processing/canning.
Drying is the oldest method of food preservation. It removes water from food such as fruit, vegetables, herbs, and meat. Removing the water prevents germ growth. Dried foods must be packed in moisture-proof containers so they do not become rehydrated.
Now you may be asking, "which method do I choose?" The following diagram may help
|Equipment ($)||Canners, jars, and lids||Freezer and stroage containers||dDehydrator or oven and strorage containers|
|Energy Requirement||Fairly low||High (due to freezer)||Low if using a dehydrator; high for oven use|
|Processing Time||Medium to Long||Short||Long|
|Does it look like the fresh food?||Somewhat||Yes||Somewhat|
|Do you lose nutrients?||Loss of vitamins A & C||Not much||Some loss of vitamin A & C|
Source: University of Georgia, So Easy to Preserve, 5th ed.
Canning preserves food by using heat to kill any bacteria that can cause illness or spoilage and creates and airtight seal to prevent future spoilage.
There are two methods of canning, boiling water bath and pressure canning. The method used depends on the acidity of the food. High acid foods with a pH balance equal to or more than 4.6 would use a boiling water bath, while low acid foods with a pH balance below 4.6 would use a pressure canner.
|pH = < 4.6 High Acid Foods|
|WATER BATH CANNER|
pH > 4.6
Low Acid Foods
The proper canning method must be used to prevent botulism (Clostridium Botulinum) which is often found in the soil and is found in two forms. The first form is vegetative cells (active cells which produce a deadly toxin), Vegetative cells are anarobic (can live without oxygen) and are kill by boiling in water 212 degrees. The second form is spores which are often in the soil and are inactive and in hibernation. Spores can only be killed if they are boiled at 240 degrees which must be done with a pressure canner. Botulism loves a low-acid environment.
|Turnips||Meat and Poultry|
| PRESSURE CANNER|
A boiling water bath uses a large covered cooking pot with a rack. The pot must be deep enough to at least one inch of water covers the top of the jars during processing. The diameter of the pot should be no more than 4 inches wider than the diameter of the burner. Again, this method is used most often when canning high-acid foods such as tomatoes, most fruits, jellies, jams, and pickles.
Pressure canning uses a special type of canner that has a lid which is able to be tightly closed so steam cannot escape. The pressure generated in this type of canner allows the food to be heated at temperatures higher than 212 degrees (boiling temperature). This is the recommended method of canning for low acid foods like most vegetables, meat, and poultry.
You should only ever can using a boiling water bath using a pot on the stove or using a pressure canner on the stove. Do not use an open kettle, steam canning, microwave oven canning, oven canning or dishwasher canning, as these are all unsafe methods.
Also, you should only use recipes that have been tested using research -based methods. Recipes from cookbooks, family, and some internet sites may not be safe to use. And DO NOT alter or make up your own recipes, because it is not safe.
You can get tested recipes from current Extension publications, USDA, and makers of home canning equipment and ingredients.
DO NOT use personal internet sites, cookbooks, "back to nature" publications, or out-of-date Extension publications.
When canning use mason-type jars that are made for home canning. Sizes of jars vary; pint and quarter sizes are most common, and half-pint jars are used most often for jellies and jams. Be sure to use regular and wide-mouth jars. Most canning jars have a life span of about 13 years.
Headspace is the space in the jar between the underside of the lid and the top of the food or its liquid. The amount of headspace needed depends on the type of food and the method of canning used, which you will find stated in the recipe.
If you have too little headspace, food may boil over onto the rim of the jar and prevent it from sealing properly, and if you have too much hefadspace the processing time may not be enough to get all the air out of the jar, resulting in a poor seal and may also result in discolored food.
Once the jars are filled, release air bubbles by placing a flat plastic spatula between the food and the jar, adjust the headspace, wipe the jar rim with a damp paper towel, and place the lid on the jar, add the screw band and slightly tighten (not too loose or too tight).
The processing time is the length of time the jars are in the canner so foods are properly heated and the lids sealed. This time kills the bacteria in the food so spoilage or foodborne illness doesn't happen, and is a critical step in food preservation. Processing times depend on the the food, the size of the jar, and the type of canner.
High altitudes can change the processing times.
|Food||Jar Size||Usual Time (< 1000 feet)||1001-3000 ft||3001 - 6000 ft|
|Water Bath Canning|
|Crushed Tomatoes||quart||45 minutes||50 minutes||55 minutes|
|Jelly||quart||varies||Add 1 minute of processing time per 1,000 ft of altitude|
|Green Beans||quart||25 minutes||Process time depends on altitude and type of pressure canner (dial vs. weighed gauge)|
After processing, make sure your jars are sealed. Press the middle of the lid with your finger. If the lid springs up when you lift your finger the seal is NOT good. While cooling you may hear a "pop" noise coming from the jars. This is a sign that the lids have sealed but it is a good idea to check them again 12 to 24 hours later.
If you notice a jar that did not seal within 24 hours of processing, you have three options:
- Refrigerate the contents and eat in a few days
- Reprocess using a NEW LID and the FULL processing time.
If the jars did not seal and it has been longer than 24 hours, those jars should be thrown away.
Remove the screw bands and wipe the jars to remove any food residues. Label and date the jars, then store in a clean, cool, dark, dry place.
Example Jar Label:
07/08/2015 = Date the jar was processed
B-2 = second batch of jars processed
Okra = food processed
You should throw out home-canned foods when:
- The jars were not processed correctly
- There is unexplained clouding canning liquid occurs
- There is a strange odor
- There is mold growth
- The jar did not seal and it has been longer than 24 hours
- The lid is bulging
- Has reached 1 year after processing date
Source: National Center for Home Food Preservation, Georgia Cooperative Extension, So Easy to Preserve 5th ed., and Food Safety Advisor Volunteer Handbook, Washington State University and University of Idaho.