Home canning is an excellent way to preserve garden produce and share it with family and friends, but it can be risky—or even deadly—if not done correctly and safely. The potential culprit is botulism.
Although it’s a rare occurrence, botulism is a serious illness caused by a bacterium toxin, Clostridium botulinum, that attacks the body’s nerves. It can cause difficulty breathing, muscle paralysis, and even death. Clostridium botulinum is commonly found in soil, on raw fruits and vegetables, on meat and fish, and many other foods and surfaces. Improperly home-canned, preserved, or fermented foods can provide the right conditions for the bacteria to make the toxin. One cannot see, smell or taste the toxin, yet if ingested, even a small amount can be deadly.
To avoid concerns about botulism, steer clear of these canning mistakes.1
Making Up Your Own Recipe
Use only up-to-date, scientifically tested recipes approved by the USDA and follow directions exactly. Good sources are The USDA Complete Guide to Home Canning, the National Center for Home Food Preservation, So Easy to Preserve, and land-grant university publications. Without scientific testing, there is no way to know how long the product needs to be processed to be safe.
Adding Extra Starch, Flour or Other Thickeners
Starches slow the rate of heat penetration into the product and can result in under processing. Clear Jel® is recommended as a thickener for canned pie fillings. If a product is not as thick as desired going into the jar, it can be thickened at the time of use.
Adding Extra Onions, Chilies, Peppers, or Other Vegetables to Salsas or Sauces
Tested recipes specify the quantity of vegetables allowed to keep the salsa or sauce within the safe pH range. Most vegetables are low-acid and adding extra vegetables will dilute the acidity and result in an unsafe product. While it is dangerous to add more vegetables to salsa and sauce recipes, fewer may be used for a milder flavor. Extra ingredients can be added at the time of use.
Canning by Electric Pressure Cooker, Oven, Open Kettle, Microwave, or Dishwasher
Boiling water bath or pressure are the only approved canning methods. Any other method should be avoided as foods will be under processed and unsafe. Heat is conducted by air in an oven which is less efficient than water or steam. As a result product temperature never exceeds the boiling point; jar breakage is also a possibility. Open-kettle canning, placing hot food in jars and sealing with no further heat treatment, has been considered an unsafe home canning practice since the 1980’s due to insufficient heat to destroy bacteria2. Microwaved food reaches 212°F but heating is not uniform; in additon, there is a danger of jar explosion within the microwave oven or as food is being removed3. The water temperature of the dishwasher’s cleaning and rinsing cyles is far below that required to kill harmful microorganisms. While electric pressure cookers use pressure for cooking, they do not meet the appliance standards for home pressure canning, even if marketed as safe for pressure canning. Washington State Extension explains all the reasons why electric pressure cookers should not be used for home canning in Canning in Electric Pressure Cookers.
Not Making Elevation Adjustments
The temperature at which water boils is affected by barometric pressure which is reduced with elevation or altitude. When water doesn’t reach the normal boiling temperature, undesired pathogens may survive the canning process. These pathogens could multiply in the canned food and cause sickness. Processing times and temperatures for recipes in most canning resources are based on canning at an elevation of 1,000 feet above sea level or lower. When canning at a higher elevation, one must add more pounds of pressure for pressure canning and more processing time for water bath canning. See charts prepared by South Dakota State University Extension for altitude adjustments.
Not Venting the Pressure Canner
Trapped air inside a pressure canner lowers the temperature obtained for a given pressure and results in under processing. To be safe, the USDA recommends that all pressure canners be vented 10 minutes before they are pressurized.
To vent a canner, leave the vent pipe (steam vent) uncovered (or manually open the petcock on some older models) after you fill the canner and lock the canner lid in place. Heat the canner on high until the water boils and generates steam that can be seen escaping through the open vent pipe or petcock. When a visible funnel-shape of steam is continuously escaping the canner, set a timer for 10 minutes. After 10 minutes of continuous steam, you can close the petcock or place the counterweight or weighted gauge over the vent pipe to begin pressurizing the canner.
Failure to Acidify Canned Tomatoes
Because the pH of tomatoes is an unknown, the USDA recommends that bottled lemon juice be used to lower the pH of the product to be unquestionably safe.
Rushing the Pressure Canner Cool-Down Time
The natural cool-down of the canner is part of the tested processing time. Hurrying this process will result in under-processed food and siphoning of liquid from the jars. It may also cause jar breakage.
Allowing “Hot Pack” Foods to Cool in Jars before Processing
Processing times are based on the food being hot at the beginning of the processing. Foods not starting hot could be under processed. Further, the rule, “hot foods hot and cold foods cold” applies; when foods are held between 40 and 140°F, bacteria can grow rapidly.
Processing Low-Acid Foods in a Water Bath
Canning low-acid foods requires special care. This includes red meats, fish, poultry and all vegetables (except for acidified tomatoes). Low-acid foods can support the production of the deadly botulism toxin if these foods are not processed properly in a pressure canner. A pressure canner heats food to high temperatures (240-250 degrees F or higher) and destroys the spores that produce the botulism toxin. A boiling water bath canner, which can be used for canning pickles or fruit, heats food to boiling temperature (212 F), which is not high enough to ensure safety for canning vegetables and other low-acid foods4.
Home canning is perfectly safe but needs to be done correctly. If you are new to canning (or need a refresher), check out Safe Home Canning Basics, by University of Missouri Extension to learn about preventing botulism and other key issues to be aware of when preserving food by home canning.
Sources:
1Avoiding Canning Mistakes. Utah State University Extension.
2Say NO to Oven Canning. PennState Extension.
3Safe Home Canning Basics. Extension University of Missouri.
4Botulism: take care when canning low-acid foods. University of Minnesota Extension.
Updated 2-2024, mg.
I put carrots in pint and quart jars for pressure canning without using boiling liquid. they were processed for 25 to 30 minutes at 10lbs. pressure, using an all american canner. they are all sealed and look fine. are they safe or should they be re-processed or thrown out? all the water in the canner was room temp. also, it took longer before the steam venting to start, but that is all that was different.
Hi, this is really a difficult question to answer. The safest method is “hot/hot/hot.” Fill hot jars with hot liquid…the hotter the better. Place hot jars into hot water in the canner. Begin processing immediately. Filling jars with cool liquid and placing in cool water might not give enough processing time to kill microorganisms. Just because a jar seals does not mean that the contents are unquestionably safe if they have not been processed correctly. If you are still within the 24 hr window, I would suggest that you reprocess the batch using hot water in the jar and in the canner. With a 2nd processing, the carrots will become quite soft but you will know that they are safe.
I packed raw beef in pint jars with 1/2 teaspoon of pink Himalayan salt. I didn’t have the time to process them so I put the filled jars in the refrigerator over night. Then set on counter a couple hours to get to room temperature. Now I’m questioning if the meat is safe after pressure canning for 75 minutes.
I will appreciate your feedback.
Thank you,
Donna
Hi Donna, there are several things of concern in your message. First, to answer your question about safety–if the meat was only out of the refrigerator for two hours, you are probably okay but there are no guarantees. The danger zone is from 40F-140F and the maximum time for food to be in that range is no more than 2 hours. Unfortunately, circumstances prevented you from proceeding with processing in a safe manner. So let’s review that process to eliminate future problems: If you desired to raw pack, the meat should be chilled when it is packed into HOT jars, leaving 1-inch of headspace. As each jar is filled, it should be placed immediately into the heated water in the canner. The amount of salt per pint jar is correct. However, we don’t recommend using Himalayan salt for canning and pickling because it has minerals in it that may affect the quality of the canned products; this is especially true for pickled products. 75 minutes at 11 lbs of pressure (dial gauge) for processing is correct assuming your elevation is 2000 ft or less. For a weighted gauge, the processing time is 75 minutes at 10 lbs of pressure up to 1000 ft. (See USDA Complete Guide to Home CAnning.) Be sure to exhaust steam for 10 minutes before adding weight or closing petcock to pressurize the canner. Processing starts when pressure has been reach.
The hot pack method is preferred for best liquid cover and quality during storage. The natural amount of fat and juices in today’s leaner meat cuts are usually not enough to cover most of the meat in raw packs.
My water bath tomatoes slowly lost water over the top. My lid wasn’t sealing right. I covered them with more water and continued cooking an extra 25 min. Do you think they’re ok?
Hi Lindy, it is difficult to answer your question. What kind of tomatoes were you processing? Did you remove the jars from the hot water bath to determine the lids were not sealing? If the latter was the case, you should have processed them again starting from the beginning with reheating, refilling the jars, adding new lids, and processing for the appropriate amount of time to make them safe. If they stayed in the hot water the entire time and you think that the top of the jars were out of the water for 25 minutes, then they may be okay???. If you are still in the 24 hour window, it might be best to put the tomatoes in freezer containers and freeze them. If more than 24 hrs have passed, it is a 50/50 call depending on the circumstances above.
I am fairly new to canning. If a recipe is made from all commercially canned ingredients except ground beef, made on stovetop for a meal like chili or baked beans, can these be canned if there are no ingredients on the do not can list? I am talking about thickener’s, pasta’s, dairy products etc.
Maybe check the Ph first.
Ron, we cannot say it enough, always use a tested recipe when canning. Making up recipes and guessing at processing time is a gamble with potential food poisoning that may go way beyond just making you a bit sick. There are several trusted resources beginning with the National Center for Home Food Preservation, USDA Complete Guide to Home Canning (2015), and extension websites. A very popular recipe is the USDA’s “Your Choice” Soup.
Why do they recommend not adding water to raw meat pressure canning. I canned raw beef with about an inch of cooled boiled water. Pressure at 11 for 90 minutes. I cannot find an answer as to why water should not be added to raw meat canning. Can you explain as I don’t want to throw out my meat but if the water compromises the safety of the meat then I shall
Hi Beverly, When you process meat using the raw pack method, the meat forms it’s own liquid as it cooks in the pressure canner so there is no need for additional liquid and could cause the jars to siphon and potentially not seal. This is especially true with pork and beef. Some drier or leaner meats benefit from adding a small amount of liquid as you have done. If your jars did not overflow or siphon, your jars of meat should be fine. Your processing time is correct for quart jars per the National Center for Home Food Preservation/USDA.
A week ago (I have been desperately trying various resources to get an answer since), I was fortunate to be given about 30lbs of collard greens which I cleaned, blanched, and packed into twelve quart jars. They were tightly packed and only needed about 1/2c of water added to reach one inch of headspace. I did include one tsp of salt in each jar. I checked for bubbles and tightened the lids before placing in the pressure canner. The canner was then closed and I vented for the full ten minutes before adding the weight for 10lbs. I then processed the jars for 90 minutes. I allowed the canner to cool on its own and was able to take the jars out after about 45-50 minutes. Unfortunately, I did not closely inspect them until the next day when I realized they are very low on water. I have never been clear if the guidance of “more than half” for liquid loss meant half the jar or half the original liquid but there is alot of dry space in these jars. How can I find out if they are safe? I hate to waste them as they were beautiful greens and was hoping to use them through the holidays but safety and health come first! I have been canning for many years (although I am admittedly more comfortable with my water bath canner) and I have never ever seen siphoning like this so I am a bit at a loss….I appreciate any guidance or resources you can share.
Hi Elsa, from the National Center for Home Food Preservation: “If liquid has been lost from jars, but the jars have been processed properly and sealed, do not reopen them to replace it. Use those jars first or food may become discolored. If more than half of the liquid in the jars has been lost, the food may not be adequately processed. In this situation, break the seal on the lid, refrigerate the jar and use it within 2 to 3 days.” In the future, you may not want to pack your jars tightly. See directions from NCHFP: https://nchfp.uga.edu/how/can_04/spinach_greens.html
I’ve been canning meat all year without a problem…until today
After canning my cold pack venison my jars didn’t show much boiling as I removed them from the canner. They all sealed but I could put my hands on the jars within an hour and it doesn’t seem right. I know I did everything correctly. I always vent for 15min. I add weight and pressurize to 14.5lbs. I only need 11lbs but when my weight starts rocking at 14.5lbs I have confidence my pressure gage is correct. I’ll then back down to 11-12 range and maintain for 75min. This was first time I had a full 10 pints to process. Will these be safe to use?
Any idea help please…
Should I reprocess my pints?
Hi Joan, I agree with you that something about this processing does not sound right and if something isn’t right with the processing, sealed jars do not mean that the venison is safe. To ensure a safe product, they should be reprocessed within the 24 hr window. Please give us a call at AnswerLine as it will be easier to talk and ask questions about your experience than to write. Phone lines open at 9 am at 1-800-262-3804 (in Iowa), 1-800-854-1678 (in Minnesota), or 515-296-5883.