1. Introduction To Food Preservation
Arla m. Halpin Family and Consumer Science Program Associate, Powhatan County Extension Office, or

2. Canning = Preservation by Heat
Destroys Microorganisms
Inactivates Enzymes
Seals Container During the Heating Process to Prevent Recontamination
Canning = Preservation by Heat

3. Two Safe Types of Canning

4. Acidity (pH)of food determines which type of canning to use
High acid foods with a pH of 4.6 or less can be processed using the boiling water bath method. High acid foods include most fruits such as apples, peaches berries, most tomatoes, and many other fruits. The acidity of high acid foods prevents the growth of Clostridium botulinum and it’s spores.
Acidity (pH)of food determines which type of canning to use

5. Boiling Water Canning-> high acid food = pH of 4.6 or less
Includes;
Apples
Apricots
Berries
Cherries
Peaches
Pears
Plums
Fruit Juices
Tomatoes ( certain)
Tomato juice
Pickled products
Boiling Water Canning-> high acid food = pH of 4.6 or less

6. Clostridium botulinum
The Clostridium botulinum bacteria forms a protective structure called an endospore in response to unfavorable environmental conditions, such as the high temperature of boiling water. Because of these spores, low acid foods such as vegetables, vegetable mixtures, soups and meats have to be processed in a pressure canner where the temperature must reach at least 240 degrees Fahrenheit. A temperature of 240 degrees will destroy botulism spores. The steam heat combined with pressure create the higher temperatures. The water bath canner only reaches the temperature of boiling water which is 212 degrees and cannot destroy the botulism spore. If the spores are not destroyed they will germinate and form toxic producing cells.
Clostridium botulinum

7. Botulism –> Neurotoxin
Colorless, odorless, tasteless
Impairs speech and vision
Muscle weakness and difficulty swallowing
Symptoms appear w/in 6 – 10 hours
Causes paralysis and death if not treated immediately
Primary cause is improperly canned food
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 conditions for Clostridium botulism to flourish.
Spores germinate and form toxin producing cells.
Botulism –> Neurotoxin

8. Acidify Tomatoes & Tomato Products
Bottled Lemon Juice
(DO NOT USE FRESH )
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 p 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
Acidify Tomatoes & Tomato Products

9. Methods of Packing RAW PACK Place food directly in jar
Pour hot liquid over food
Firmly pack
HOT PACK (preferred)
Food cooked in liquid before packing
Liquid poured over food
Better color and flavor
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.
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.]
Methods of Packing

10. 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 foods may be starchy and swell when heated.
Too little
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
Headspace

11. 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.

12. Processing Times Determined By;
Type of food
COLD SPOT
Size of the jar
Size of the food
Consistency of
liquid in jar
Thermocoupler
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 so that it reaches 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 process food at the correct time the recipe calls for.

13. Boiling Water Method Boiling Water Canning (212°F at sea level)
Used for acid foods
Boiling water canner is used for high acid foods. Should be 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 allows 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.
Boiling Water Method

14. Boiling Water Canning Procedures
6” of water in the canner
Jars on rack in canner
Water must cover jars 1-2 inches
Add more water if necessary
Turn to highest setting, cover
Begin timing at full boil
After done, remove lid and wait 5 minutes
Remove jars
Cool 24 hours
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.

15. Pressure Canning (240°F)-low acid foods
2-3” of simmering water in canner
Jars on rack
Lid on with weight off
Vent 10 minutes
Close vent
Begin time when pressure is reached
Turn off heat when time is up
Let pressure drop to 0, undisturbed
Wait 2 minutes
Remove weight
Open, remove jars
Cool hours
In pressure canning the steam in the 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 of 240°F are necessary to destroy botulism spores, as well as spores of bacteria that cause spoilage. Pressure canning is the only safe method for canning low acid canned foods like green beans, corn, carrots and other vegetables, soups, meats and seafood.
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.
In pressure canning, you must “exhaust” the canner. Allow a steady stream of steam to escape 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.
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.

16. Pressure Canner Parts Vent Gasket Gauge
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
The gasket is a rubber or rubber like compound that helps seal the edges of the canner and lid to prevent steam from escaping. Gaskets may be removable for cleaning or replacement. Not all pressure canners have gaskets, the American pressure canner has a metal-to metal- seal ( So Easy To Preserve pp 21).
Heating the filled canner with its lid locked into place boils the water and generates steam that escapes 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.
Pressure Canner Parts

17. 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.

18. 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, bringing with it microorganisms' to recontaminate the food( So Easy To Preserve pp.17)

19. Testing for Seals 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.]

20. 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.

21. 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.