1. Family and Consumer Science Associate Powhatan County Extension Office
An Overview of Canning
Arla M. Halpin
Family and Consumer Science Associate
Powhatan County Extension Office
ext. #3

2. Two Safe Types of Canning
Boiling Water Bath Canning
Pressure Canning
Canning is an important and safe way to preserve food…if it is done correctly. Not counting your labor, canning home grown food, may save you half the cost of buying commercially canned food (Complete Guide To Home Canning pg. 1-5).
“There are two safe types of canning, depending on the type of food being canned; boiling water and pressure. The canning process involves placing foods in jars or cans and heating them to a temperature that destroys microorganisms that could destroy food” ( So Easy To Preserve pg 17).
Which method you use depends on the acidity of the food.

3. Acidity (pH level ) of Foods
Acid Foods
Neutral Foods
Low Acid Foods
The term “pH” is a measurement of the acid level in a food. pH is measured on a scale from 1 to 14. The lower it’s pH value the, the more acid in the food.
Whether food should be processed in a pressure canner or boiling water bath canner to control the botulium bacteria depends on the acidity of the food( We’ll talk about botulism in a few more slides).
Acidity may be natural as in most, or increased by adding lemon juice, citric acid, or vinegar, as in pickled food.
Low acid canned foods are not acidic enough to block their growth or destroy them more rapidly when heated. The acidity level in foods can be

4. Acid Foods pH less than or equal to 4.6 Generally all fruits
Tomatoes and figs are borderline –
Sauerkraut
Foods to which large amounts of acid are added (pickles)
Acid” foods have a pH less than or equal to Acid foods include most all fruits. However, tomatoes, figs and Asian pears are borderline and specific amounts of bottled lemon juice or citric acid must be added to them before canning to ensure safety of the recommended process.
Acid foods also include sauerkraut and naturally fermented foods that are preserved by natural acids produced during the fermentation process and foods to which large amounts of acid (usually in the form of vinegar) are added. An example would be pickles.

5. Tomatoes Acidify Tomatoes & Tomato Products Bottled lemon juice
Citric acid
Because tomatoes have a pH value close to 4.6 you must take some precautions to safely can them ( So Easy To Preserve pp 50).
Acidify for safety
1 Tab. Lemon Juice or ¼ teaspoon citric acid per pint
2 tbsp. bottled lemon juice or ½ tsp. citric acid
Tomatoes have traditionally been canned in boiling water 212 Degrees Fahrenheit .
Tomato recipes that specify only pressure canning have so many low acid ingredients added to them that they are only safe when canned in a pressure canner at the specified pressure ( So Easy To Preserve pp 50).
Ball Blue Book; “ The following tomato recipes must be processed in a pressure canner because of the combination of acid and low- acid foods” ( pp 64).
Tomatoes and Celery
Tomatoes wit Okra
Stewed Tomatoes

6. Low Acid Foods pH < 4.6 Generally all vegetables Meats Poultry
Seafood
Soups
Mixtures of acid and low acid foods (spaghetti sauce – meat, vegetables and tomatoes)
Low acid have a pH higher than This category includes vegetables, meats, poultry, seafood, soups and other mixtures of both acid and low acid ingredients. An example would be spaghetti sauce with tomatoes, meat and vegetables.

7. How Canning Preserves Food; High Temperatures in Canning
Destroys microorganisms
Inactivates enzymes
Removes oxygen from jars
Forms a vacuum seal
Microorganisms include molds, yeasts and bacteria. Microorganisms are everywhere, in the air, in soil and on people and animals and can easily contaminate food. Physically damaged like bruising or puncture on produce, provide places where microorganisms' can start to grow. During the canning process the heat destroys microorganisms, most of the bacteria, and inactivates enzymes that can cause spoilage.

8. What Can Happen If Low Acid Foods Are Not Pressure Canned?
Botulism
When conditions become favorable:
40 – 140 degrees F
High moisture > Spores germinate
No air in jar and form toxin
producing cells
When the canned food cools down, here is what you have:
A temperature that is in the danger zone between 40 and 140°F
A lot of moisture in the jar.
No air in the jar…a vacuum seal.
These are the perfect condition for Clostridium botulism to flourish.

9. Clostridium botulinum” bacteria
Forms protective, heat resistant spores
Most bacteria is destroyed by heat. However, the Clostridium botulinum bacteria forms botulism spores when conditions are not favorable for the organism to grow (high heat, dryness, etc.), the bacterial cell forms a protective structure called a spore. To destroy the spore, it takes a higher temperature than boiling. If the spores are not destroyed, they will germinate and produce toxin in the food when it is stored on the shelf.
Because of these spores, low acid foods have to be processed in a pressure canner where the temperature must reach at least 240 degrees Fahrenheit, which is hotter that the boiling point of water, these higher temperatures cannot be reached in a boiling water bath canner.

10. Signs of Botulism Food may not look “bad”*
Symptoms usually appear within 12 to 72 hours:
Digestive upset (in some cases)
Blurred, double vision
Difficulty swallowing, speaking and breathing
Death
Food can contain the toxin without any visible signs of spoilage. It causes a very deadly type of food poisoning that begins usually within 72 hours after consuming the contaminated food. Symptoms can include digestive upset, blurred or double vision, difficulty swallowing or breathing, paralysis and eventually death.

11. Preventing Botulism Home Canned Foods
Spores won’t germinate in acid environments.
Spores are destroyed when heated long enough at a specific temperature.
USDA recommends a canner temperature of at least 240oF at sea level for canning low acid foods.
Pressure canner must be used for all low acid foods.
Botulism can be prevented…IF YOU FOLLOW THE RULES!
The spores will not germinate in acid environments. This is why acid foods or foods that have acid added to them like tomatoes and pickles can be safely canned in a boiling water bath. Spores are destroyed when heated long enough at a specific temperature. For canning low acid foods, USDA recommends a canner temperature of 240°F at sea level. Temperatures this high can only be reached in a pressure canner. Pressure processing is the only safe way to can all low acid foods.

12. Follow Directions Exactly
* The following slow heat penetration:
Adding extra sugar or fat.
Having food pieces larger than called for in directions.
Adding thickeners.
That is why it is important to follow directions exactly. If you add extra sugar or fat, or if you do not prepare the food according to the directions, or if you add thickeners like starch, rice or noodles, then the process time tested as being accurate to heat even the cold spot in the jar may not be safe.

13. Methods of Pack Raw Pack For foods that lose shape when cooked.
Place raw food directly in jars. Boiling hot liquid is then poured over the food.
Pack firmly, don’t crush.
Add jars carefully to canner.
The method of packing the jars also plays an important role in heat transfer through the product. In a raw pack, raw food is placed directly in the jars. Then hot, boiling liquid is poured over the contents. Pack firmly, but do not crush. Free the bubbles or trapped air between the pieces of food. Wipe the jar rims. Add lids, adjust ring bands and process.

14. If directions only list hot pack instructions, then hot pack!
Preferred method for most foods.
Food is cooked in liquid before packing. Cooking liquid poured over food in jar.
Fewer jars needed.
Less floating.
Better color and flavor.
Easier to pack, foods pliable.
The preferred method of pack for most foods is the hot pack. In a hot pack, foods are cooked in liquid before packing. Then the cooking liquid is poured over the food in the jar. The advantages of this method are that fewer jars are needed, there is less floating of the food because air has cooked out of it, the color and flavor are better retained, and the foods are easier to pack in the jars because they are more pliable. Always follow directions for the specific type of pack called for.
[Activity: Have jars of food canned by hot pack method and same food canned using a raw pack. Ask the audience which method they think was used for each jar and why. Raw packs usually have more floating food than hot packs.]
If directions only list hot pack instructions, then hot pack!

15. Jars and Lids Use only canning jars Wash Prepare lids and ring bands
Remove air bubbles (plastic knife).
* Wipe
* Adjust
“Mason type jars are designed to withstand the high temperatures during canning. Mayonnaise jars may not seal and could break during heating.
To prepare jars for canning, follow these steps.
* Wash canning jars; don’t use if chipped or scratched – keep hot until used.
* Prepare 2-piece canning lids and ring bands according to package instructions for the brand you are using.
* Remove air bubbles. Use a plastic knife or bubble freer for this so as not to scratch the jars. Don’t use a metal knife you could chip the jar or put a tiny crack in it.
* Wipe jar rims with wet, clean cloth or paper towel to remove any residue.
* Adjust the two-piece lids; tighten until fingertip-tight.

16. Headspace
Space in the jar between the inside of the lid and the top of the food or its liquid. Check directions for the correct headspace.
The space at the top of the jar between the top of the food and the bottom of the lid is the headspace.
The amount of headspace needed depends on the type of food being processed.
.. Usually:
1/4” jellied fruit products
1/2” fruits, tomatoes and pickles
1” to 1-1/4” low acid foods like vegetables, meats and mixtures of acid and low acid foods. These food may be starchy and swell when heated.

17. Headspace * Too little * Too much
Food may bubble out during processing.
Deposit on rim may prevent proper sealing.
* Too much
Food at the top is likely to discolor.
Jar may not seal properly, because not all air may be forced from jar during process.
What happens if you do not leave the correct headspace?
If there is too little, food may bubble out or run over during processing. Then deposits on the rim may keep the jar from sealing properly. If there is too much headspace, the food at the top of the jar is likely to discolor during storage, and the jar may not seal because all of the air was not forced out.

18. Processing Times Determined By;
Type of food
COLD SPOT
Size of the jar
Size of the food
Consistency of
liquid in jar
Each food has it’s own processing time.
The way the food is prepared (such as the size of pieces, with or without the peel, etc.), the consistency of the canning liquid and the size of the jar have an effect on how heat penetrates through the product.
The process time is determined based on the length of time it takes to adequately heat all of the food in the jar has reached the temperature needed to destroy the dangerous microorganisms. Each jar has a “cold spot” in the middle of the jar that is the last part of the jar to reach the desired temperature, so processes food at the correct time the recipe calls for.

19. Important “Musts” for Canning
Food must be properly prepared and processed the correct amount of time.
Canner must be accurate and operated correctly.
You may need to make altitude adjustments, depending on your altitude.
Directions from a reputable source must be followed (USDA, Cooperative Extension, National Center for Home Food Preservation ( Ball Blue Book, So Easy To Preserve.
Up-to-date methods and information should be used; beware of “granny’s method.”
Besides selecting the appropriate method of canning, there are certain other rules you must follow to have safely canned products.
If the directions say to peel and chop, then peel and chop. If they say to leave whole, then leave whole. If it says process 30 minutes for pint jars, then put it in pint jars and process not 20, not 25, but how long??? … 30 minutes.
Whatever type of canner you have, it must be operated correctly.
You may need to make altitude adjustments, depending on where you live.
Only use directions from reputable sources such as USDA, Cooperative Extension, the National Center for Home Food Preservation, the Ball Blue Book or So Easy To Preserve.
Don’t rely on recipes from granny or your friends. Check reputable sources before you begin. Canning recommendations have changed over the years as new research has led to safer methods.

20. Boiling Water Method Boiling Water Canning (212°F at sea level)
Used for acid foods
A boiling water bath canner is a coated covered pot with a rack that s is deep enough for at least 1 or 2 inches of briskly boiling water to cover the tops of the jars. The diameter of the canner should be no more than 4 inches wider than the diameter of your burner to ensure proper heating of all the jars. Using a kettle that covers 2 burners is not recommended because the middle jars do not get enough heat.
The canner must have a tight fitting lid and a rack. The rack keeps the jars from touching the bottom of the canner and allow the water to circulate freely around the jars as they process. The rack also has dividers, jars will not touch each other or fall against the sides of the canner during processing.
A boiling water canner is used for canning acid foods like fruit, jams and jellies, tomatoes and pickled foods. Water boils at 212°F. at sea level. As altitude increases, water boils at lower temperatures. The higher the altitude the longer the processing time to ensure that all bacteria are killed.

21. Boiling Water Canning Procedures
* Have about 6” of water simmering or hot in canner.
Hot packed jars - simmering water
Raw packed jars - hot water
* Place jars on rack in canner.
* Water must be over the tops of the jars by at least one to two inches.
To can foods in a boiling water canner, you need about 6 inches of water in the canner. Be sure to have extra water boiling in a separate pan in case you need to add more once the jars are in the canner.
The temperature of the water in the canner when you add the jars depends on the type of pack you are using. For hot packed jars, the water should be simmering when the jars are placed in the canner. (Simmering is about 180 degrees F.)
For raw packed jars, the water should be hot, but not simmering. (If you are using a thermometer, this water should be about 140F only.) This will help to avoid breakage.
Place the jars on a rack in the canner so they do not come in contact with the bottom of the canner. This allows the water to circulate around the jars and also helps to prevent breakage. If your canner does not have a rack, you can place ring bands in the bottom of the canner. You can use any rack that will fit in the canner. DO NOT PUT TOWELS IN THE BOTTOM. We do not recommend that method.
Once you have the jars in the canner, the water must be one to two inches above the tops of the jars.

22. Boiling Water Canning Procedures cont.
Add water if necessary.
Turn to highest setting, cover canner.
* Begin timing at full boil.
After processing time is complete, turn off canner, remove lid and wait 5 minutes.
Remove jars straight up out of canner and place on padded surface.
* Cool 12 to 24 hours, undisturbed.
* Check seals.
* Remove rings.
* Wipe off jars before storing in a
cool, dry, dark place.
If necessary to get the water 1 to 2 inches above the tops of the jars, add more hot or boiling water. If more hot water is needed, pour the water around the jars, not on them.
Wait until the canner has come to a full boil before you begin timing the process.
If your altitude is above 1000 feet, you will need to make altitude adjustments. You will need to check an altitude adjustment table in a reputable canning guide to find how long to process the specific food and jar size you are canning.
After the process is complete, turn off the canner, remove the lid being careful to allow the steam to escape away from your face, and wait 5 minutes before removing the jars.
While you are waiting, you can prepare the area where you will put the jars to cool. You will need to lift the jars straight up out of the canner and place them on a towel or padded surface or on a wire cooling rack in an area away from drafts. The jars must sit for 12 to 24 hours undisturbed.
After that time, check to be sure the jars are sealed. Remove the ring bands for storage. Wipe off the jars and store them in a cool, dry, dark place. The ring bands can be washed and re-used.

23. Pressure Canning Method
Pressure Canning (240°F)
Used for low acid foods (and mixtures of acid and low acid foods)
A pressure canner is a specially made heavy pot that has a lid that can be locked to prevent steam from escaping The steam in a pressure canner circulates around the jars , transferring heat and bringing the internal temperature of the food to 240 degrees Fahrenheit, which is a higher temperature than the boiling point of water. “The pressure does not destroy microorganisms, but the high temperatures applied for adequate periods of time do kill microorganisms'’ ( The Complete Guide to Home Canning pp 1-19). These higher temperatures 240°F are necessary to destroy botulism spores, as well as spores of bacteria that cause spoilage. Pressure canning is only safe method for canning low acid canned foods like green beans, corn, carrots and other vegetables, soups, meats and seafood.

24. Pressure Canner Parts Vent Gasket Gauge
The gasket is a rubber or rubber like compound that helps seal the edges of the canner and lid to prevent stem form escaping. Gaskets may be removable for cleaning or replacement. Not all pressure canners have gaskets, some have a metal-to metal- seal ( So Easy To Preserve pp 21).
The vent port or petcock is a short hollow pipe that sticks up above the canner lid. When open, it allows air and steam to escape from the canner. When closed, it holds steam inside.
Heating the filled canner with it’s lid locked into place boils the water and generates steam that escaped through the petcock or vent port. Pressure caners must be vented for 10 minutes before they are pressurized. When steam first escapes set a timer for 10 minutes. After venting for 10 minutes, close the vent to pressurize the canner.
The pressure gauge registers the pressure inside the canner. A dial gauge displays the amount of pressure inside the canner with a needle pointer. The gauge should be tested before each canning season. Chesterfield County Extension Office has a tester. If you gauge is off by more than 2 pounds, replace it.

25. Pressure Canning Procedures
* 2” to 3” water simmering or hot in canner.
Hot packed jars - simmering water
Raw packed jars - hot water
* Place jars on rack in canner.
* Put lid on canner with weight off or petcock open.
For pressure canning, have only 2 to 3 inches of water simmering or hot in the canner. Again, if you used a hot pack, the water should be simmering. If you used a raw pack, it should just be hot. You will also need to use a rack in the pressure canner. Once the jars are in place, lock the lid on the canner securely, with the weight off or the petcock open.

26. Pressure Canning Procedures – continued…
* Exhaust 10 minutes – steady stream of steam escaping.
* Close vent or petcock.
* Count time when correct pressure is reached.
* Adjust for altitude, if needed (water bath too).
Turn off heat at end of processing.
* Let pressure drop to 0, undisturbed
In pressure canning, you must “exhaust” the canner. To do this, you watch for a steady stream or funnel of steam to begin escaping from the vent pipe. Allow the steam to escape in this manner for 10 minutes. Then place the weight on the pipe to close the vent or close the petcock, depending on the type of pressure canner you are using.
When the canner gets up to the correct pressure, start timing the process. In a dial gauge canner, you will start timing when the correct pressure is reached on the dial. In a weighted gauge canner, you will start timing when the weight rocks gently back and forth or jiggles 2 to 3 times per minute, depending on the type of weight.
Remember to make altitude adjustments, if needed.
Once the processing time has passed, turn off the heat and let the pressure drop to 0.

27. Pressure Canning Procedures – continued…
Wait about 2 minutes after pressure drops to 0 psig to make sure no pressure remains.
(For some canners, check that locks in handles are released.)
Remove weight or open petcock. Wait 10 min.
Open canner. (Be careful of steam!)
Remove jars to padded surface or rack.
Cool jars 12 to 24 hours, undisturbed.
Check that jars have sealed.
Once the pressure has dropped (the weight stops rocking or jiggling, the dial goes to 0, and for some canners, locks in the handles release), wait 2 minutes.
Then, remove the weight or open the petcock, and wait 10 more minutes.
Next, open the canner being careful to allow steam to escape away from your face.
Lift jars straight up out of the canner and place on a padded surface or cooling rack (do not tilt jars to remove water on top).
Cool jars undisturbed for 12 to 24 hours away from drafts. After that time, remove the ring bands and check for seals.

28. Vacuum Seal Holds the lid on the jar.
Prevents recontamination of the food.
Prevents air from drying out the food.
In the canning process air is driven from the jar or can during heating and as it cools a vacuum seal is formed. This seal prevents air from getting back in the jar, brining with it microorganisms' to recontaminate the food( So Easy To Preserve pp.17)

29. Testing for Seals * Lid curved inward, won’t move when pressed.
* Listen for “pop”.
* Lid curved inward, won’t move when pressed.
* Clear ringing sound when tapped.
How do you test to see that jars are sealed?
There are basically three ways.
1) Listen for a popping sound as jars begin to cool.
The lids will curve down or inward toward the jar and will not move when pressed.
If you tap on the center of the top with a metal spoon, you will hear a clear ringing sound rather than a dull thud.
[Activity: Have some sealed and unsealed jars of food. Let audience practice checking for seals.]

30. Reprocess Unsealed Jars
Within 24 hrs
Remove lid
Check jar rim
New lid
Reprocess
Label
24 hour window to reprocess jars
Check jar sealing surface for tiny nicks
Change the jar if necessary, add a new treated lid.
Label as reprocessed, and use first, it will be softer and less nutritional value than food processed only once
From;” So Easy To Preserve” pp32
If you do not wish to reprocess, you can either refrigerate the food and use it quickly or you can freeze it for longer storage.

31. Storing Home Canned Food
Store in a cool, dry, dark place.
Avoid temperature extremes.
Use within 1 year for best quality.
If the jars sealed properly, store the food in a cool, dry, dark place. Avoid storing them where they are near heat pipes or in areas where they will be exposed to temperature extremes.
For best quality, use home canned foods with one year.