The Not So Good Old Days?

I treasure the memories of Grandma's pantry filled with jars of home canned foods, but canning methods have changed a lot since Grandma day. Many methods and much of the equipment that were once considered safe are no longer considered less reliable than modern practices and not safe or recommended today. Take the quiz below to determine how well you understand and practice safe canning methods and update your canning know-how for better food safety to ensure the highest quality of your home-canned foods.

Any canning recipe older than 1990 is no longer safe to use. The USDA changed and updated the approved canning methods in 1989. Processing times are much more precise, based on acid pH factors and YOUR specific altitude.

No Substitutes For Safety

There are no safe short cuts in canning. Food that is improperly canned can cause illness or even death. Safe canning methods have been developed based on laboratory research. You cannot assume that a canning method is safe just because it is printed in a magazine or cookbook. Your local County Extension Office is an excellent place to look for information on how to safely can food at home.  Sometimes canning recommendations change. As we learn more from research, we can better evaluate our food preservation methods. Find more answers to Common Canning Questions.

Safe canning requires careful planning. It can be rewarding to fill your pantry shelves with home canned foods, but remember to follow these simple guidelines:

Follow a tested recipe. Grandma's old cookbooks might have some wonderful recipes, but canning recommendations have changed significantly over the years. In order to ensure a safe, high quality product, follow a tested recipe. The United States Department of Agriculture's Complete Guide to Home Canning (1994 edition) is an excellent source of tested recipes. You can find the USDA canning guide on the web at: http://foodsafety.cas.psu.edu/presqueryform.cfm or contact your local cooperative extension agent for recipes tested for your area.Research continues in the area of home canning and processing times and temperature are constantly being evaluated and modified to reflect the latest scientific information. Always use an updated, modern and tested recipe. Pay close attention to the processing time and temperature, anything less will put you and your family at risk of food poisoning. See more in the Canning Section...

The most accurate, up-to-date, and dependable guidelines are in the current bulletins put out by the USDA, and these available free or cost only a few cents from your local county extension office. Many states and universities have a web presence offering downloadable fact sheets. The U.S. Department of Agriculture's, Complete Guide to Home Canning (1994 edition) is an excellent source of tested recipes, available through this link USDA Canning Guide.

Canning Quiz

Do you make up your own canning recipes?

Unsafe. Making up your own canning recipe -- without using scientifically tested recipes and methods, you will not know how long the products need to be processed to be safe. See more...

Do you add extra starch, flour or other thickener to your recipe?

Unsafe. Adding thickeners changes the rate of heat penetration into the product and can result in under processing. This might make the product unsafe to eat.

Do you process foods by using an altitude chart for correct times?

Unsafe. New guidelines in food safety now use altitude time charts. Because the boiling temperatures are lower at higher altitudes, the products will be under processed if you are canning in an areas that is above sea level. Products processed only by times are now considered unsafe to eat.

Do you add extra ingredients such as onions, chilies, bell peppers or other vegetables to canning directions?

Unsafe. Adding extra onions, chili, bell peppers, or other vegetables to tested recanning recipes dilute the acidity and can result in botulism poisoning because the product will not be properly acidified.

Do you skip the venting step to save time?

Unsafe. Not venting the pressure canner before processing can result in air pockets that will not reach the high temperature needed to process low-acid foods properly.

Do you use untested equipment, or fail to have your pressure canner gauge tested each year?

Unsafe. Pressure canners should be retested annually. If the gauge is inaccurate, the food might be under processed and the product might be unsafe to eat. See more...

Do you use old, outdated canning directions for processing tomato based recipes?

Unsafe. Modern tomato hybrids are not as acidic as the old heirloom varieties. It's no longer considered safe to use a boiling water bath canner for tomatoes without adding acidifiers. Not all tomatoes are adequately acid, especially those picked from dead vines. Not acidifying tomatoes may result in a product that could support the growth of Clostridium botulinum. See more...

Do you cool your pressure canner under running water?

Unsafe. Research-based calculations for processing times include the residual heat during the normal cool-down period as part of the heating process. Hurrying this process will result in under processed food that might then be unsafe to eat.

Do you retighten screw bands while the jars are still hot?

Unsafe. Do not retighten screw bands. If you re-tighten the bands, you may interfere with the sealing process.

Do you can two layers of jars at one time?

Safe. Two layers can be processed at once, in either the boiling water bath or pressure canner, but you must place a wire rack between the layers so water or steam will circulate around each jar. Make certain that the water covers the tops of all jars by one inch in a boiling water bath canner. The pressure canner should have two to three inches of water in the bottom.

Do you let food cool before processing hot pack recipes?

Unsafe. Letting food cool before processing in recipes that call for a hot pack -- the heat curves for processing are based on the food being hot at the beginning of the processing time.  Therefore, the product might be under processed and unsafe to eat.

Do you use the open-kettle method?

Unsafe. The name is a little misleading, because it has nothing to do with a kettle. This is an old, outdated canning method that poses a serious health risk - particularly low-acid foods. In this process, the food was packed into sterilized jars and sealed. The theory was that the heat from the food was sufficient to create a vacuum seal in the jar without further processing. Many old recipes passed down through the years, or those found in older cookbooks, use the old-time, outdated canning directions for the open kettle method. This method is now considered unsafe because we now know that without heat processing, bacteria, yeast and mold contamination is common. The growth of these microorganisms, in addition to spoiling the food, often caused lids to later become unsealed. Spoilage was common using the open-kettle method. and resulted in a very real danger of botulism.

QUESTION - What is the problem with canners that do not have flat bottoms?

ANSWER - If the canner bottom is not flat, there will not be complete contact with a flat heating element. Therefore, it will take longer for the water to heat to the proper temperature. However, since process times start when boiling or the critical pressure occurs, the proeces will still be safe. It will just take a longer time to get to the point where the clock starts. The product will be somewhat overcooked but it will be safe.

I don't know of any apparatus that can improve the canner/heating element interface. Some people buy an old gas stove to keep in their garage or basement to use for canning. Howver, it is probobly cheaper to just get a new canner with a flat bottom.

Do you rely on paraffin or wax seals

Unsafe. Wax or paraffin coatings are a very old way of creating an airtight seal on top of as jam, jelly, or perserves. If properly done, this method was fairly reliable, and it is still used by some home canners. However, it is no longer considered safe and is not recommended by most canning manuals and extension services. Aside from being tedious to do properly, paraffin seals are fragile and subject to imperfections.

Do you use the Cold-Pack Processing method?

Unsafe. This old fashioned system is still in general use, but is no longer a recommended procedure. Cold-packing is the practice of packing food directly into storage jars without heating either the food or the jar first. Usually the product is raw fruit or vegetables, whole or chunked, over which a heated preserving liquid or syrup is poured. The food is then sealed and processed. This method is now considered unsafe because we  know that without heat processing, bacteria, yeast and mold contamination is common. For those reasons, it is no longer a recommended procedure except for certain pickles that are packed in a strong vinegar brine solution.

Do you use a steam canner?

Unsafe. This method heats jars by steam, but it is not considered safe because both low- and high-acid foods are often very under-processed and therefore could spoil. steam canner is not the same as a pressure canner. Steam canners are not recommended for home canning because steam canners do not heat foods in the same manner as do boiling-water canners or pressure canners. Using this method in conjunction with boiling-water process times may result in spoilage. The steam canner was designed as a means to process foods using steam without the aid of pressure. Studies have concluded that using steam canners as instructed by the manufacturer would result in under processing and spoilage.

Do you use a pressure cooker rather than a pressure canner?

Unsafe. Pressure cookers have less metal, are smaller in diameter, and will use less water than pressure canners. The result is that the come-up and come-down times will be less than for the standard pressure canner. The come-up and come-down times are part of the total processing time that was used to establish a reasonable margin of safety. See more...

Do you use the microwave to "can" foods?

Unsafe. A microwave oven cannot be used for home canning. Low-acid foods must be processed at 240 degrees Fahrenheit; which requires a pressure canner. A microwave can only reach 212 degrees Fahrenheit. Even acid foods must have the uniform heat provided by a conventional water_bath canner. Because of its uneven heating pattern, a microwave does not assure consistent heat to each jar during processing. There also is a danger of explosion of jars during heating or as the jars are removed from the oven.

Do you use a conventional oven to can foods?

Unsafe. Using your oven instead of a boiling water or pressure canner to process is extremely dangerous and definitely not a recommended procedure. Foods will be under processed because air is not as good of a heat conductor as water or steam. The jars also might blow up. The risk of jars breaking during heating, when the oven door is opened, or when jars are removed from the oven is extremely great. The danger of inadequate processing can also pose a health risk. Heat transfer in the oven is uneven and the food does not reach high enough temperatures.

Do you use a dishwasher to can foods?

Unsafe. Using your dishwasher to processing canned foods is dangerous. The temperature of the water during the cleaning and rinsing cycle is far below that required to kill harmful microoganisms. Thus the product will be under processed and unsafe to eat. The only safe procedures for canning are boiling water bath process for HIGH acid foods and pressure canning for low-acid foods

Do you use other, unconventional methods for canning?

Unsafe. Other unsafe methods include canning food in slow cookers or crock pots which can be extremely dangerous, especially with low-acid foods, and is not recommended. This can be dangerous because the temperature will vary according to the accuracy of oven regulators and circulation of heat. Dry heat is very slow in penetrating into jars of food. Also, jars explode easily in the oven. These outdated method is extremely unsafe. Foods are under processed because air does conduct heat as well as water or steam. So-called canning powders are useless as preservatives and do not replace the need for proper heat processing. See more...

Do you use proper canning lids?

Unsafe. Jars with wire bails and glass caps, clamp-on type lids, one piece lids, or old-fashioned rubber ring seals are no long considered safe for home canning. Old canning jars make a charming presentation or attractive storage containers for dry foods, but don't use them for canning. One-piece lids, Zinc lids or porcelain-lined caps are also no longer recommended. The latter are no longer manufactured, having been supplanted by modern, two piece vacuum lids with rubber seals built into them.

See more...

Do you use proper canning jars?

Unsafe. Pickle, mayonnaise, or other store jars were never intended to be recycled as canning jars. Reusable canning jars are the only type of jar that should be using in canning because they are made to seal properly with repeated use and to be used safely in a steam pressure canner. See more...

Do you allow processed jars to remain in the canner after processing is finished?

Unsafe. Jars will cool too slowly if left in the canner -- there is a group of harmless microorganisms called thermopiles, which can survive the canning process. If jars are held hot for long periods, they can produce acid. This results in the defect known as "flat sour." This condition results in a very undesirable flavor.

Do you know what to look for in spoiled canned goods and how to properly dispose of suspect jars?

Safe. The CDC estimates that foodborne diseases cause approximately 76 million illnesses, 325,000 hospitalizations, and 5,000 deaths in the United States each year, these figures do not include mild cases of food poisoning were patients did not seek medical care, or misdiagnosed cases. Most cases of food poisoning are associated with inadequately processed, home-canned foods. See more...

Do you guess at processing times or use outdated times?

Unsafe. Canning means heating foods at a specified temperature for a specified time according to the pH value of the food, the size of the jar, the use of a pressure canner (NOT a pressure cooker) and the altitude where you live. These are not things that you can determine at on your own. See more...

Do you store home canned products longer than one year?

Unsafe. The recommended storage time for most home canned food is one year. Storing food longer than is not recommended -- lengthy or overly hot storage will also decrease quality and some nutrients may be lost.

Do you recycle or re-use grocery store jars as canning jars?

Unsafe. Recycled jars from the grocery store, also known as packers' jars, are not made for home canning. The jars that contain pickles, mayonnaise or peanut butter are not made for the rigors of home canning. Even though standard home canning lids may seem to fit these jars, the lids may not seal because the glass is not as thick and slightly irregular. The jar neck may be too shallow for a standard home canning band to hold the lid tightly against the jar. In addition to sealing problems with commercial jars they may also be dangerous. Most of them are made of thin glass and are not heat tempered, as regular home canning jars. They may not withstand the high pressure of canning and break or explode. When you open the canner, the quick drop in temperature could cause the recycled jar to explode. Use only standard glass canning jars, also known as mason jars after their nineteenth century American inventor, John L. Mason. These reusable jars are produced in a variety of sizes, some with decorative finishes for gifting. They are made to seal properly, to be durable with repeated use and to be used safely in a steam pressure canner. The manufacturer's name is usually blown in the side of the jar.