Canning food

with Sharon Peterson
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How to can and know that your home canning recipes are safe.

The first question many individuals ask when embarking on the process of canning food is: What exactly do I need? Before you fill your first jar, or use your home canning recipes from your great grandmother, it is important to understand the science of what you are doing.

Learning these fundamentals will help answer many future questions, as well as the initial question of 'What do I need'?

The Science: Chemical Changes and Microorganisms

When home preserving foods, you should be aware of two types of spoilage; Chemical changes and microorganisms. 

Chemical Changes

* Enzymes cause the process of decomposition in foods. This starts as soon as food is picked Enzymes are why it is important to use fresh picked produce. 

* Oxidation occurs when fruit is exposed to air, this causes browning in fruits like apples or pears. If you’re not careful, it may cause your fruit to look very unattractive.


* Yeast, the main cause of fermentation and bubbling.

* Mold, this is the green fuzzy stuff that we’re all familiar with. It grows in a wide range of foods and conditions.

* Bacteria is what causes Botulism. Botulism is a very serious type of food poisoning. It thrives in low acid and oxygen free environments. This bacteria will only be killed in very high temperatures of over 240 degrees F. These temperatures are achievable under pressure, but NOT in a water bath canner.

Repeat: Canning food in a pressure canner stops botulism, a boiling water bath does not. Botulism is a serious, but avoidable risk in canning low acid food.

How Processing Stops Spoilage in Your Foods.

During processing, as the contents boil, food spoilers are stopped and oxygen is expelled from the jar. As the jar cools after processing, its contents shrink and the lid is pulled down flat to form a seal. This prevents further contamination of the freshly sterilized foods inside the jar.

Remember, canning food in a boiling water bath will NOT prevent botulism. However, it will – prevent yeasts and molds from forming, oxidation from occurring and stops enzyme action in high acid foods.

All fruits are high acid foods. Pie fillings, jams, jellies and fruit spreads (such as apple butter) are all included in this group. 

Pickled products have acid added during preparation, usually in the form of vinegar or lemon juice. Salsa, some condiments including ketchup and barbecue sauce, as well as the dill pickle are included in this group. Because the acid is added during the cooking process, these are also considered high acid foods.

When processing jars in a boiling water bath, the heat achieved is about 212 degrees F. This temperature is sufficient to stop any yeast or molds from forming as well as halting enzyme actions. 

Pressure Canning – prevents yeasts, mold, oxidation and stops enzyme action ; most importantly, it stops BOTULISM.

Vegetables and meats are low acid foods. Botulism thrives in low acid, low oxygen environments. In order to safely preserve low acid foods, pressure is necessary. 

As in a hot water bath, the process involves heating the foods in order to sterilize them and stop any spoiling factors. Once the jars are removed from the heat, the food cools and shrinks. As the food cools it pulls down on the lid, forming a seal. Your food is then protected from further contamination. 

The difference between the two processing methods is the amount of heat produced. A pressure canner produces a much higher level of heat. And remember, Botulism can only be prevented at very high temperatures. 

Self Check :

Think about this statement... "My grandmother used a boiling water bath and boiled her veggies and meats for a very long time, this made them safe to eat.".

True or False? Why?

Answer to yourself, then scroll down to find what my answer is. 

home canning

False - All vegetables and meats are at risk of botulism. Canning food in a pressure canner is the only way to assure that botulism is stopped. The higher heat will stop botulism. The heat produced in a boiling water bath will not. 

Articles that restate or further explain canning food safety.

Unsafe methods
Tomatoes ~ a special case of changing acidity
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The Legal Stuff

by Sharon Peterson, Copyright © 2009-2019

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Any statements or claims about the possible health benefits conferred by any foods have not been evaluated by the Food & Drug Administration and are not intended to diagnose, treat, cure or prevent any disease. You are encouraged to verify all canning and food preservation advice on the USDA food preservation website. 

See my Full Disclaimer here.

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