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Canning: Keep Your Summer Year Round

Updated: Apr 3, 2019

While spring and summer cannot last forever, your summer bounties can certainly be enjoyed year round. Canning is a wonderful way to preserve the season's offerings at the height of its freshness without sacrificing taste and nutrition. Not only is canning good for you, it is good for the environment as well by keeping excess food that cannot be consumed during harvest out of landfills.


Canning was developed in France in the late 18th century to provide quality food supply for the army. Nicholas Appert discovered that spoilage can be prevented/delayed when food is heated and sealed in an air-tight container. The canning process was then developed to destroy bacteria, remove oxygen and create a vacuum in the container. Besides offering a safe food choice, this process is able to preserve much of the food’s nutrients. According to a study published in 2007, the nutrition value (in terms of carotenoids, vitamin E, minerals, and fiber) of canned food is similar to that of fresh and processed products.

Over time, canning spread beyond military usage. The canning technique was perfected and commercialized in the early 19th century. Canned food was well-adopted by the growing working class who were looking for convenient yet healthy meal options.

Home canning has also gain popularity, especially for those with large gardens. It is a wonderful way to preserve food at the peak of freshness when it is in abundance. Ingredients are often less expensive during the high season and the flavor is spectacular and can hold up well during the canning process. Imagine opening a can of tomatoes in the winter. The fragrance and sweetness can instantly bring back the reminiscent of summer. 

Canning is also a great way to use “ugly” fruits and vegetables.  Many farmers and stores discard or compost these items as they are hard to sell. While these fruits and vegetables may not win the beauty contest, they are just as tasty as the pretty ones. Reduce food waste while satisfying our cravings, what a win-win.


A main concern in any food preservation process is food safety. One bacterium that draws special attention is Clostridium botulinum, which produces a deadly toxin in a low-oxygen, low acidity environment. This bacterium can only be eliminated at temperatures above the boiling point of water. Hence it is important to choose the right canning method based on the food item to be preserved.

Bacteria that cause spoilage come in many forms. They require different oxygen content, temperature, and acidity to grow. Canning recipes are developed with these conditions in mind, and provide the recommended temperature, pressure and canning timing to ensure food safety. For this reason, it is important to follow recipes from credible sources.


Water Bath

Pressure Canning

There are two methods for canning depending on the acidity of food being preserved. Acidity can be measured in pH levels which range from 0 to 14. The lower the pH level, the more acidic the item is.

Foods that are acidic, such as plain fruit, have ph levels below 4.6. These types of food can be sterilized with water-bath. In water bath canning, filled canning jars are submerged in a hot water bath and boiled for a specified period of time based on the recipe. The internal pressure of the jars increases with heat and pushes out the air at the top. Once out of the water bath, the jars cool and a vacuum is created.

Foods with low acidity, that is foods with ph levels above 4.6, have to be sterilized at a temperature higher than the boiling point of water in order to eliminate deadly microorganisms. Hence pressure canning is required. Examples include plain vegetable, soup and meat.

A couple of cautious points:

As water boils at lower temperatures as altitude increases, process time or canner pressure needs to be increased to compensate for lower boiling temperatures. Today's tomatoes are sweeter with reduced acid level. When canning tomatoes, it is recommended that acid be added.


Home canning is simple and does not require a large investment in specific equipment.

Pots: Water-bath canning does not require special pots. However, be sure that the pots have room above the jars (at least 1” plus extra space) to hold enough water and prevent overspill. Many of the canning pots come with a rack that lifts the jars off the bottom of the pot and holds them in place. Pressure canning requires pots that can heat water above its normal boiling point. You can use pressure canners or pressure cookers that are rated for canning by the manufacturers.

Jars: There are a few styles of canning jars. They are all made to withstand high temperature and create an air tight seal. You’ll find two common sealing mechanisms -- a flat lid screwed onto the jar with a threaded ring, or a lid with gasket held in place by a lock. These jars can be reused if they are not damaged. However the lids and gaskets will need to be replaced.

Food Strainers and steam Juicers: Tomato sauce, apple sauce and jams are a few favorite home canning items. But removing the skin and seeds can be tedious and time consuming. Both the food strainers and steam juicers are great time-savers. Food strainers remove the skin and seeds from the fruit with a few cranks. They can be motorized as well. Steam juicers can be used to extract juice from soft fruits. Be creative with the byproducts. The leftover skin and pulp can be dehydrated and grinded into seasonings or natural coloring agents.

Other tools: Ladles, funnels, and jar lifters are useful tools as well for handling the food and jars.


If canning is a little too involved, refrigerator pickling is a good and easy alternative to prolong the life of produce.  Making refrigerator pickles simply requires soaking the vegetable in an acid, such as acetic (vinegar), citric (lemon juice), and lactic (whey). As these pickles are not heat processed, it should be kept in the refrigerator for safety.

Refrigerator pickling is flexible. You can use any kind of vegetables — cucumbers, carrots, radish, cauliflower, broccoli, beans…  Depending on the hardness of the vegetables, you may need to precook them.  You can add any kind of herbs and spices.  Rosemary, dill, bay leaf, oregano, red chili flakes, peppercorns… are our favorites.


The pickles should last in the refrigerator for 3 months. However, the timing depends on the amount of acid in your brine which slows down the food's deterioration. If you use less acid, your pickles may go bad faster.

Ingredients for the brine:

1 cup Apple Cider vinegar 1 cup water 1 table spoon salt Herbs and spices

Plus 1lb of mix vegetables, cut into bit sizes.  


Vegetables ready to be eaten raw do not require additional preparations. If you are using hard vegetables such as green beans, blanch them first.  Do not over cook and keep them crisp!  Add all ingredients for brine and bring it to boil.  Place prepared vegetables and herbs in clean jars, and cover with the hot brine.  Vegetables get cooked a little in the hot brine. If you are using vegetables such as carrots, radish, or daikon, it is not necessary to blanch them.  Cut them thinner if necessary.  Let it stand until the brine cools down, place cap and refrigerate for two days and it is ready for your enjoyment.

For additional information for canning, USDA has an excellent website with many methods and recipes necessary for home canners.

Photo Credit: Heating the Canning Jars by Ryan Snyder, Cooking and Canning by B.D.’s World, Heating strawberries and sugar for jam by Ruth Hartnup, Refrigerator Pickles by 21 Acres Library


Recipe and contributing material from the 21 Acres Kitchen Team: The 21 Acres Center for Local Food and Sustainable Living in Woodinville, WA is a nonprofit leaning center and living laboratory focusing on organic agriculture, sustainable living and green building technologies.

Canning by Wikipedia

How Canning Preserves Foods by National Center for Home Food Preservation

The History of Food Canning by

Best Canning Jars by


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