Canning Q and A
With answers provided by:
UAF Cooperative Extension Service instructor Leslie Shallcross
Why can’t I just can meat by boiling the jars in a water bath?
A boiling-water bath does not get hot enough to kill botulism spores. All low-acid foods like meat, fish and vegetables must be processed in a pressure canner at a higher temperature to be safe.
What does it mean to have pressure when you’re canning fish or meat? Why do you need pressure to can it so it doesn’t make you sick? Why do you need more pressure to can something if you live somewhere like Denver?
A pressure canner keeps steam from escaping from the pot and creates “pressure” on the surface of the water. The water can then get hotter than the ordinary boiling temperature of 212 degrees Fahrenheit. At sea level and 10 pounds of pressure, the water temperature will get to 240 degrees F.
We need this extra heat to destroy dangerous microbes. At higher altitudes, as in Denver, Colo., there is less air pressure and the ordinary boiling temperature is lower than 212 F. At altitudes above 1,000 feet, we need to increase the pressure in the canner even more to reach our safe canning temperature.
I want to can some meat and fish. It will take more than two hours for the canning process to occur, though, so maybe I’ll go catch a movie or take the kids out for ice cream. Any reason why I shouldn’t do that?
Destroying dangerous botulinum spores involves heating at the correct temperature/pressure for the correct length of time. Only careful monitoring of your canner will assure that the temperature/pressure has stayed at the correct level for the entire recommended processing time.
The tops of the jars are loose after I take the jars out of the canner! What went wrong?
The ring or screw band is often loose after processing. This is not a problem—the function of the ring is to hold the flat lid securely on the top edge of the jar during the processing. The sealing compound on the flat lid is responsible for the flat lid staying in place after processing, not the ring
Why do I need to let the canner blow steam out for 10 minutes before starting to time the canning process?
This creates an even temperature inside the canner by expelling air pockets—the canner becomes filled with hot water vapor
Why can’t I can hot meat in a cold jar?
Even though canning jars are tempered glass, they may crack or shatter if contents are added to a cold jar or cold is added to a hot jar. The rule is that hot contents require a hot jar and hot water in the canner; cold contents require a room-temperature jar and cool water
How tight should the jar lids be screwed on before I start canning?
We describe the correct level of tightening as “fingertip tight.” Using your fingertips instead of your palm, turn the screw band until you feel resistance; then, turn it a quarter-inch to half-inch farther.
Why do you need racks in the canner to put the jars on?
Racks protect the jars from too much direct heat—even though they are specially designed to withstand heat, the metal bottom of the canner is too hot. Lifting the jar off the bottom of the canner also allows water to fully circulate around the jars for even heating.
Why do you need liquid in the jars when canning cooked meat?
If you brown meat before canning you change the way heat transfers through the product. Adding liquid to the jar eliminates air pockets and creates better heat transfer through the meat.
Why do some people use tomato juice in the jars when canning wild game?
The tanginess of tomato juice goes well with stronger-tasting meat.
I bought a dial-gauge canner at a garage sale. It has a little dent on the side but otherwise looks good as new! I’m going to can some caribou tonight. Any reason why I shouldn’t do this?
This might be OK, but a dented or warped canner may not heat evenly or close properly. The bottom of the canner must be able to sit flat on your stove or heat source. Before canning, put some water in your canner with the lid on it and make sure you can easily get it up to pressure and that the gasket or other parts don’t leak. Also, if you have a dial gauge, take your canner lid/gauge to your Cooperative Extension Service Office to have the gauge tested for accuracy each year.
My grandma used to can fish in a water bath using a recipe from a 1930s cookbook and the fish tasted so delicious. No one ever got sick from eating it, so what’s the problem with using that tried-and-true old recipe we love so much?
Times and maybe even germs have changed. We know more now and the tests have shown that in order to effectively destroy botulism, a pressure canner is necessary. A boiling-water bath canner does not get hot enough (212 F in the boiling water versus 240 F in the pressure canner at 10 psi).
I canned a batch of meat using our woodstove. I went in to watch TV. Came back, added wood to the fire a couple of times while canning. Everything seemed fine and the tops of the jars made a popping noise after I removed them from the canner. Any reason why I shouldn’t eat what’s in those jars?
People often think that if the jars seal, they are safe. However, the vacuum and seal can occur even if you haven’t processed long enough to kill the dangerous microbes.
My elderly aunt gave me a jar of canned salmon with a label that said “Happy Birthday!” It looks scrumptious. Why should I hesitate to gobble everything in that jar?
Before eating any canned food gifts, you should be certain that the gift giver has followed the USDA’s and Cooperative Extension Service’s recommended process for canning that product. Ideally the jar’s label will tell you what is in the jar, when the product was processed, how long the product was processed, and the method used (i.e. July 2012, Smoked Salmon, 110 minutes @11 pounds).
I like to screw on the jar lids super tight when I can food in the canner, because the jars need to be airtight. Is there any reason I shouldn’t do this?
Overtightening can cause the exact problem you are trying to avoid. It can keep your jar from sealing by warping or buckling the edge of the flat lid or it can be so tight it keeps air from escaping from the jar.
Leaving space inside the top inch of the jar is silly, because everyone knows it will leave an air pocket above the food and allow microbes to grow there.
Following the recommended guidelines for head space and processing time is important. The processing times assure that the airspace/headspace is sterilized so no microbes will grow. The head space is also important so your jar contents do not get pushed out of the jar during canning, interfering with sealing compound on the rim or lip of the jar.
I buy jars at garage sales and use them over and over. I do the same thing with the flat lids. It’s just more economical to do this and has no effect on the safety of what I’m canning…right?
Jars in good condition should be used for no longer than 10 years. Garage sale jars have an unknown history and may be too old—not a good bet for canning success.
Flat lids can only be used one time because the sealing compound is degraded after one use.
It seems silly and redundant to wash the jars before canning, since they’ll be subjected to really high heat for more than an hour and a half. Why do I need to bother?
Even though the pressure-canning process sterilizes the jars, you should always wash jars to remove any dust, dirt or other potential contamination.
Why can’t I just leave food on the rim of the jar before putting on the flat lid and canning the food?
Food left on the rim of the jar will prevent the flat lid from sitting down completely on the rim of the jar—this could keep the jar from sealing.
I plan to take the hot jars immediately after canning and immerse them in cold water, to cool them down so I can handle them. Would this be a reasonable thing to do?
The cool-down time is part of the safe processing time. Jars cooled suddenly might break and might not seal or form a vacuum.
My canned jars didn’t pop. They look fine, though. I took a bite of food from one of the jars and it tasted great. It seems silly to go through that whole process all over again just to hear a “pop” noise.
The pop tells you a vacuum has formed and that you have a safely sealed jar—this seal is important for keeping out microbes during extended storage.
I found some canned meat in the cellar of a house I just moved into. There are no labels on the jars and no one can tell me how long they’ve been there, but everyone knows canned food stays good and safe practically forever. It is sinful to waste perfectly good food. Give me one good reason why I shouldn’t eat it.
DON”T EAT IT! Never eat canned food if you do not know whether it has been processed according to U.S. Department of Agriculture-recommended guidelines. Botulism is potentially deadly and is odorless, flavorless and colorless.
I have some pint jars, some quart jars. It would probably be more energy-efficient to can them all together at one time, in the same canner. Why shouldn’t I?
Always follow recommended instructions for canning times and methods. These methods are based on how quickly a safe heat level is attained in the product. A quart jar does not heat up as quickly, so you cannot use times tested for pints, nor can you simply increase the time yourself. Processing times for each product must be tested in a specially equipped laboratory.
My hands look clean. Why do I have to go to all the trouble of washing them before starting to can food?
Even though proper processing will destroy many microbes, safe and high-quality food depends upon cleanliness at each stage of the process. Hands can introduce germs and other contaminants.