Canning At Home Rick Sloan FCS Agent
Dec 29, 2015
What will we learn?
Principles of Canning Two Methods of Canning Packing Methods Canning Equipment Processing Time Boiling Water Processing Pressure Canning Processing
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Canning Basics
Food is placed in a canning jar and heated to a temperature that destroys targeted microorganisms.
Heat also inactivates enzymes that cause spoilage.
Air is driven from the jar during heating. As the jar cools a vacuum seal is formed.
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Commercial Sterility
All pathogens, spoilage bacteria, molds, and yeast are “killed.”
Those that survive are thermophilic bacteria that cause spoilage but not illness. Some produce gases. Some produce bad odors.
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Vacuum Seal
Holds the lid on the jar. Prevents recontamination of the food. Prevents air from drying out the food.
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Two Methods of Canning
Boiling Water Canning Used for high-acid foods
Pressure Canning Used for low-acid foods. Can also be used for high-acid foods but might
result in a soft texture.
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High-Acid Foods (pH < 4.6)
All fruits, except for: figs tomatoes, and melons
Rhubarb Fermented pickles, such as sauerkraut Acidified foods, such as pickles and tomatoes
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Low-acid Foods (pH > 4.6)
All vegetables, except for rhubarb Meats Poultry Seafood Soups Mixed canned foods (low-acid + high-acid)
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Why Two Methods of Canning?
Yeast, molds, and most bacteria are killed at boiling temperatures -- 212ºF at sea level.
C. botulinum forms spores that require higher temperatures for destruction in a reasonable period of time -- usually 240ºF or above at sea level.
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Clostridium botulinum
Clostridium botulinum bacteria are found naturally in soil and water.
Seven known types, but only A, B, E and F cause illness in humans.
This bacterium can produce heat-resistant spores.
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C. botulinum -- Growth
To germinate, the spores need the following conditions:
anaerobic environment (No Oxygen) low-acid food temperature between 40ºF and120ºF relatively high moisture
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C. botulinum -- Growth
Optimal conditions might be found in: Home canned foods Smoked fish and sausage Foil-wrapped baked potatoes sitting at room
temperature Packaged mushrooms Pot pies and other foods in gravy
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Botulinum Toxin
The botulinum toxin, one of the deadliest known, causes botulism.
1 mg can kill 655 tons of mice. Food can contain toxin without showing any signs. Antitoxin available, but slow recovery. Permanent
nerve damage possible.
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Botulism -- Symptoms
Symptoms usually appear within 12 to 72 h after eating contaminated food:
• Digestive upset (in some cases)• Blurred, double vision• Difficulty swallowing, speaking, and breathing• Possible death from suffocation• 10-35% mortality rate
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Preventing Botulism
Spores do not grow in high-acid foods. Spores killed when low-acid foods heated long
enough at a specific temperature. Process low-acid foods in a pressure canner,
which can reach a temperature of 240ºF.
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Preventing Botulism
Prepare and process food according to instructions in a tested recipe.
Canner gauge must be accurate and properly used.
Use only high quality raw ingredients. If toxin is suspected, detoxify food before
discarding. The toxin is destroyed by boiling even though the spores are not.
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Improperly Canned Foods
Never consume improperly canned foods. Throw out – do not feed to animals. Boiling will not always adequately destroy
toxin. When cleaning up surfaces contaminated by
unsafe canned foods, prepare a 1:5 bleach to water solution.
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Raw Pack
For foods that lose shape when cooked. Place raw food directly in jars. Pour boiling hot liquid
over the food. Pack firmly, do not crush. Add jars carefully to warm canner to prevent jar
breakage from heat shock. Preheat water to 140oF before putting raw-packed
foods into boiling water bath.
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Hot Pack
Preferred method for most foods. Food is cooked in liquid before packing. Cooking liquid
is then poured over food in jar. Less floating of food pieces in the jar. Better food color and flavor. Easier to pack, foods more pliable Heat in preparing kills some microorganisms. Preheat water to 180oF before putting into boiling water
bath.
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Pressure Canners
Flat rack in bottom Pressure regulator or indicator:
Dial or weighted gauge Older models have petcocks
Vent pipe for pressurizing Safety valves or overpressure plugs Safety locks when pressurized Rubber gaskets in lid (metal to metal seal)
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Replacement Parts
Dial gauges, when inaccurate Gaskets (sealing rings)
Every 2 years usually Rubber overpressure plugs
Every 2 years Vent pipes if clogged Air vent/cover lock from lid Weighted gauges or dead weight if lost
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Processing Schedules
Definition:Length of time at a specific temperature that a food must be processed.
Affected by:pH value of the foodComposition of the food
- Viscosity- Tightness of pack- Convection vs. conduction transfer of heat- Starches, fats, bones
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Affected by: Preparation style of food Initial temperature of food as it is filled into jar Temperature of processing Size of jar Shape of jar
Processing Schedules
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Significance of Heat Penetration
Processing time is affected by whether food heats by convection, conduction, or a combination of both.
Heat penetration studies used to scientifically determine safe processing times.
The “cold spot” in the food must reach the correct temperature for the correct length of time to destroy target pathogens.
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Heat Penetration
Follow recipe exactly. The following slows heat penetration:
Extra sugar or fat Oversized food pieces Added thickeners
Use recommended canners. Heat-up and cool-down times in pressure canners
are counted toward sterilizing value of the process. Do not rush them.
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Processing Time
Each food and preparation style has its own processing time so always use a tested recipe.
Time differs with size of jar. Too little = under processing spoiled or
unsafe food Too much = over processing overcooked
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Pressure Increases Temperature
Heat food to 240oF to destroy botulinum spores. Cannot achieve this in boiling water.
The only safe way to can low-acid foods is with pressure.
Temperature of 240ºF or above needed for reasonable processing times 10 psig = 240ºF at sea level 15 psig = 250ºF at sea level
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Boiling Water Bath
Have water simmering (180oF) in canner, high enough to cover jars when filled (about six inches for most loads). Hot packed jars = simmering water Raw packed jars = warm to hot water
Place jars on rack in canner. Add more hot water if necessary, once jars
are in canner. (Never pour hot water directly onto raw-packed jars).
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Boiling Water Bath
Start counting processing time after water returns to a full boil.
Adjust processing time for altitudes over 1,000 feet.
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Boiling Water Bath
If processing foods for more than 30 minutes, water should be two inches over jars when process begins.
If water stops boiling at any time during process, bring the water to a boil and begin the process over.
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Pressure Processing
Have 2 to 3 inches of water simmering or hot in canner. Hot packed jars = simmering water Raw packed jars = warm to hot water
Place jars on rack in canner. Put lid on canner with weight off or petcock
open.
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Pressure Processing
Exhaust canner for 10 minutes. Close vent or petcock. Start counting processing times when correct
pressure is reached. Adjust pressure for altitude, if needed. Turn off heat at end of processing. Let pressure drop to 0 psig naturally.
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Pressure Processing
Wait two minutes after pressure drops to 0 psig. (For some canners, check that locks in handles are released.)
Remove weight or petcock. Open canner. Watch steam! Remove jars to padded surface or rack. Cool jars 2 to 24 hours, undisturbed. Check that the jars have sealed.
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MODULE 3: Units
Definition of a High-Acid Food Preparing Foods for Canning Acidifying Tomatoes Canning High-Acid Foods
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High-Acid Foods (pH < 4.6)
All fruits, except for: figs tomatoes, and melons
Rhubarb Fermented pickles, such as sauerkraut Acidified foods, such as pickles and tomatoes
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Selecting Fruits and Tomatoes for Canning
Choose firm, ripe products. Do not use overripe fruits. Gather or purchase only what you are able to
can within 2 to 3 hours.
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Washing Fruits and Tomatoes for Canning
Dirt contains many microorganisms hardest to kill.
Wash everything, even foods to be peeled. Use several water changes. Lift the food, do not soak.
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Preventing Fruit Darkening
1 teaspoon (3000 mg) ascorbic acid added to one gallon of water
Commercial ascorbic acid mixture Heating the fruit
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Preventing Fruit Darkening
The following do not work as well: Citric acid solution Lemon juice Sugar syrup Salt/vinegar solution
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Canning Liquids for Fruits
Sweet syrup, water or juice can be used.
Sweet syrup: Helps retain shape, color, and flavor of fruit. Not needed for
safety Mix sugar with water or juice, heat to dissolve sugar. Proportions of sugar to liquid given in publications. Up to 1/2 the sugar can be replaced by corn syrup or mild
flavored honey. (Use more corn syrup if bland.)
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Canning Liquids for Fruits
Juice Packs: Commercial unsweetened apple, pineapple, or
white grape juice. Juice can also be extracted from fruit being canned
or from the above fresh fruits. Extracting juice:
Thoroughly crush ripe, sound fruit. Heat to simmering. Strain.
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Canning Liquids for Fruits
Artificial Sweeteners: Add just before serving Saccharin-based sweeteners turn bitter Aspartame-based sweeteners lose flavor
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Acidifying Tomatoes
pH between 4.0 - 4.6 (borderline) Even if pressure processing, tomatoes must be
acidified. For Pints:
1 tablespoon bottled lemon juice or 1/4 teaspoon citric acid
For Quarts: 2 tablespoon bottled lemon juice or 1/2 teaspoon. citric acid
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Acidifying Tomatoes
Add directly to jar before filling. If too acid tasting, add sugar. Use 4 tablespoons vinegar per quart or 2
tablespoons per pint. However, flavor might be off.
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Salt
Salt is only used for flavor in canned tomatoes and vegetables.
It can be omitted because does improve the safety of the final product.
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Canning High-Acid Foods
Heat canner with about six inches of water to simmering.
Treat new lids. Wash jars. Select and wash high quality raw product.
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Canning High-Acid Foods
Fill jars either hot pack or cold pack: hot pack (food and liquid heated before filling) cold pack (raw food put in jar and boiling liquid
poured over it) Leave appropriate headspace. Remove air bubbles.
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Canning High-Acid Foods
Wipe rim of jars. Adjust lids. Lower jars slowly into canner. Count processing time when the water
returns to a boil. Remove jars to a padded surface. Cool away from drafts, 12 to 24 hours.
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Headspace
Space in the jar between the inside of the lid and the top of the food or its liquid.
Check canning directions for that correct headspace for each food.
Usually: 1/4” for jellied fruit products 1/2” for high-acid foods, such as fruits,
tomatoes, and pickles 1” to 1-1/4” for low-acid foods
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Headspace
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 processing
time not long enough to drive all the air from inside the jar.
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