HOME CANNINGTHE BASICS

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MARTHA SMITH PATNOAD, CP-FS

CE FOOD SAFETY EDUCATION SPECIALIST

DEPT OF NUTRITION AND FOOD SCIENCES

UNIVERSITY OF RHODE ISLAND

401-874-2960

mpatnoad@uri.edu

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Two Approved Methods of Canning Foods At Home

1) Boiling Water Canning (212°F)

Acid foods, ie- tomatoes, pickles, relishes, salsas, jams and jellies

2) Pressure Canning (at least 240°F)• Low acid foods• Mixtures of acid and low acid

foods )

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Why Two Methods?

Depends upon the food item

Acid vs Low Acid

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Why Two Methods?

Clostridium botulinum

Yeasts, molds and most bacteria are destroyed at boiling temperatures (212oF).

C. botulinum forms spores that require higher temperatures for destruction in a reasonable period of time

(usually 240oF).

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Botulism Foodborne Illness The botulinum toxin, one of deadliest

known, causes botulism food poisoning.

1 mg can kill 655 tons of mice.

Food can contain toxin without showing signs.

Antitoxin is available, but there is slow recovery. Permanent nerve damage is possible.

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Botulism Foodborne Illness

Symptoms usually appear within 12 to 72 hours:

Digestive upset (in some cases)Blurred, double visionDifficulty swallowing, speaking and

breathingPossible death from suffocation

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Botulism Poisoning To germinate and produce toxin, the

spores need the following conditions:Anaerobic ( no air)Low acid (pH > 4.6)40oF to 120oFRelatively high moisture

spore (germinates) bacterium

waste materials and toxins

growth(multiplies)

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Preventing Botulism

Home Canned FoodsSpores won’t germinate in acid foods

(pH < 4.6).Spores are killed when heated long

enough at a specific temperature.USDA usually recommends 240oF

canned low-acid foods.Pressure canner MUST be used for

all low-acid foods.

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Preventing Botulism, cont. Food must be properly prepared

and processed for the correct time Pressure canner accurate and

operated correctly Foods checked when opening jars Foods should be boiled for at least

10 minutes before serving

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Preventing Botulism, cont.

Follow the recipe- NO MODIFICATIONS

The following slow down heat penetration:Extra sugar or fatOversize food piecesAdded thickeners

Use recommended canners

Heat-up and cool-down times in pressure canners are counted toward “sterilizing” the contents of the jar. Don’t rush!!!

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HOME CANNING :THE PROCESSES

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Home Canning Basics

FOODS CAN BE DIVIDED INTO TWO CATOGORIES:

1. ACID

2. LOW ACID

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Acid FoodsGenerally all fruits

Tomatoes (specific amounts of citric acid or bottled lemon juice areadded to acidify)

Sauerkraut

Foods to which largeamounts of acid are added (pickles, relishes, salsas)

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Low Acid Foods

Generally all vegetablesMeatsPoultrySeafoodSoupsMixtures of acid and low acid foods

(spaghetti sauce – meat, vegetables and tomatoes)

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Acidity Acidity measurement = pH Low pH values = high amount

of acidity Bacteria can grow between

pH 4.6 and pH 9.0 Bacteria grows best

between pH 6.0 and pH 7.5

Vinegar

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AcidityAcid Alkaline

0 1.0 2.0 3.0 4.0 4.6 5.0 6.0 6.4 7.0 8.0 8.5 9.0 10.0 11.0 12.0 13.0

14.0

LimesPickles

Vinegar

Commercial Mayonnaise

Apples Beef,

Veal

Pork

Carrots, Pumpkins

Sweet Potatoes

Cheddar Cheese

Chicken

Milk

Corn

Distilled

Water

Soda

Crackers

Egg White

Acidity levels affect bacterial growth

Different bacteria, different acid tolerance

OrangeJuice

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Home Canning Basics

• Use only recipes/directions and DO NOT MODIFY from: USDA/ Cooperative Extension, National Center for Home Food Preservation (www.homefoodpreservation.com), Ball Blue Book, So Easy To Preserve.

• Always use current methods and information. NEVER USE “granny’s method.”

• Use only high/ quality food/ fresh produce.

• Food must be properly prepared and processed the correct amount of time.

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Home Canning Basics

• Food is placed in a canning jar with a 2-piece lid and is heated to a temperature that destroys microorganisms.

• Pressure canner must be accurate and operated correctly.

• Heat also inactivates enzymes that can cause changes in color, flavor and texture.

• Air is driven from the jar during heating.

• As the jar cools, a vacuum seal is formed.

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Home Canning Basics Processing Time

* Each food has its own processing time.

Follow directions carefully!

* Time differs with size of jar.

* Too LittleSpoilage

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How Canning Process Times Are Determined

• Foods are prepared by a specific procedure.

• The length of time it takes to adequately heat the coldest spot in the jar is determined.

• Size of the jar, size of the food, consistency of the canning liquid, etc. all have an effect on how heat penetrates through the product.

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EQUIPMENT

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Jars and Lids• Wash canning jars; don’t use if nicked

or scratched – keep hot until used

•ALWAYS use new flat lids

•Follow package instructions to prepare 2-piece lids and ring bands

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Home Canning Basics Vacuum Seal

• Holds the lid on the jar.• Prevents recontamination of the

food. • Prevents air from drying out the

food.

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Testing for Seals

• Listen for “pop”

• Lid curved inward, won’t move when pressed

* Clear ringing sound when tapped

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Packing Methods

Raw/Cold PackUse fo foods that lose their shape when

cooked

Raw food put into jars Boiling hot liquid is poured over the

food

Pack firmly, don’t crush

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Hot Pack

Preferred method for most foods.Food is cooked in liquid before

packingCooking liquid poured over food in

jarFewer jars neededLess floatingBetter color and flavorEasier to pack, foods pliable

Note: If directions say only hot pack then hot pack!

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Headspace

• Is the space in the jar between the inside of the lid and the top of the food or it’s liquid

• Check directions for the correct headspace

* Usually:1/4” jellied fruit products1/2” fruits, tomatoes and pickles1” to 1-1/4” low acid foods

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Headspace

* Too littleFood may bubble out during

processingDeposit on rim may prevent sealing

* Too muchFood at the top is likely to discolor. Jar may not seal properly, as all the

air may not be forced from jar during processing

Pressure Canning

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Low Acid FoodspH greater than 4.6

MeatsPoultrySeafoodGenerally all vegetablesSoupsMixed canned foods

(low acid + acid) However, if pH < 4.6 = acidified

foods

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Pressure Canners vs. Cookers To be considered a pressure canner

for USDA processes, the canner must be big enough to hold at least 4 quart-size jarsPressure cookers/saucepans with

smaller volume capacities are not recommended for use in canning

Enough heat may not be delivered

during pressurizing and the cool-down period in smaller pressure cookers/saucepans

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Pressure Canner Features Flat rack in bottom

Pressure regulator or indicator

Dial or weighted gauge

Vent pipe (port) for pressurizing

Safety valves or overpressure plugs

Safety locks when pressurized

Flexible gasket in lid

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Pressure Canners Features

Dial Gauge

Indicates pressure inside the canner

Must be checked for accuracy

Has dead- or counter-weight to close open vent for pressurizing

Pressure is increased or decreased by adjusting burner heat.

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Pressure Canners Features

Weighted GaugeRegulates pressure inside the canner

Open vent is the same one that pressure regulator fits

Will continue to allow some air to be released from canner during process

Can’t be tested for accuracy

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Weighted Gauges cont’d

One pieceFitting for 5, 10 or 15 poundsDo not use dead- or counter-weight from

dial gauge canner or pressure cooker.• Mirro: “jiggles” 3 to 4 times per minute.

Three pieceNumber of pieces used determines 5, 10 or

15 pounds • Presto: rocks gently throughout entire process.• Mirro: “jiggles” 3 to 4 times per minute.

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Pressure CannerHow it Works

Steam inside the pressurized canner circulates around the jar

Transfers heat by conduction

Food in center of jar much reach 240°F

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Pressure Canner Processing

Use 1 inch headspace in jars. A few products use 1-1/4”

Have 2” to 3” of water simmering or hot in canner. Hot packed jars – simmering water, 180 F Raw packed jars – warm to hot water, 140 F

Place jars on rack in canner.

Put lid on canner with weight

off or petcock open.

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Venting the Canner Also called “exhausting” the canner.

As the water boils in the canner, the “empty” space becomes a mixture of steam and air.

The temperature of a steam/air mixture is lower than the temperature of pure steam.

Venting eliminates (“exhausts”) the air so processing takes place in a pure steam environment. Process times are intended only for a pure

steam environment.

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Venting the Canner, cont.

Some manufacturers of weighted gauge canners say venting is not necessary.

USDA instructs to vent ALL pressure canners.The one difference in “following

manufacturer’s directions” if not included there.

Without proper venting, up to 30% of the sterilizing value of a 20-minute process may be lost.At 10 pounds.

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Venting the Canner, cont. Steam must flow freely from the open vent port in the lid for

10 minutes prior to pressurizing. After putting filled jars in the pressure canner, fasten the

lid in place. Leave the ventport open.

• Pipe where weighted gauge or dead weight will go. Turn the heat on high. When water boils, steam will start to come out of open

vent. Wait until there is a constant, strong funnel of steam, then

start timing 10 minutes.

At the end of the 10 minutes, place weight in place to start the processing for the time sprecified in the directions.

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Loss of Pressure Drop in pressure during processing means

the sterilizing value of the process will be decreased.Underprocessing.

Foodborne illness (botulism) and/or spoilage could result.

If pressure drops below target anytime during the process time, bring the canner back up to pressure and start timing the process over, from the beginning.

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Fluctuating Pressure Large and/or quick variations in pressure

during processing may cause loss of liquid from jars.

If the variation is a drop in pressure after process has begun, it also means the process must be started over.

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Opening the Pressure Canner Turn off the heat at end of process and let

jars cool in canner until pressure is 0

(Dial gauge should read zero)

Wait 10 minutes to remove the canner lid.

When the canner lid is opened, tilt it so the steam is pushed away from your face.

The steam, water and jars in the canner will still be very hot, even bubbling or boiling.

Hot Water Bath Canning

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Tomato-Pepper Salsa

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• The canner must have a rack in the bottom

• Fill the about half full of water, and begin heating

• There must be enough water so the filled jars will be covered with 1 to 2 inches of water

• The temperature should be about 180°F when it is time to add your filled jars

Prepare the Canner

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• Wash tomatoes. Make an “x”-shaped slit in the skin at the base of each tomato.

• Dip washed tomatoes into boiling water for 30-60 seconds until skins just begin to split.

• Then dip immediately into cold water.• Slip the skins off the tomatoes and core

them.• Chop the tomatoes into small pieces.

Measure out the required amount.

Prepare the Tomatoes

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Prepare peppers Caution: Wear plastic or rubber gloves and do not touch your

face while handling or cutting hot peppers. Wash hands thoroughly before touching your face or eyes.

Wash the peppers well. Cut the peppers lengthwise. Remove the stems and white membranes. Remove seeds; the more seeds you remove, the milder the salsa will be.

Chop the peppers into small pieces. Measure out the required amount.

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Prepare onions and garlic Remove the outer skin. Wash the onion and

garlic cloves well. Cut away any tough stem or root end parts. Chop the onions into small pieces. Use a

garlic press to finely mince the garlic (or chop very small by hand).

Measure out the required amount of each.

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Cook Salsa Mixture• Canned salsa is a hot pack.• 1. Combine all the measured prepared vegetables in

a large saucepan with the vinegar and seasonings.

• 2. Bring to a boil, stirring frequently.

• 3. Reduce the heat and simmer for 20 minutes, stirring occasionally.

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Fill Jars: Part 1

• 1. Pour the hot salsa mixture into clean, hot canning jars.

• 2. Use a ladle and a funnel to avoid getting salsa on the sealing surface (and prevent a big mess!)

• 3. Leave ½”HEADSPACE

• 4. Liquid should cover the salsa mixture

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Fill Jars: Part 2• 5. Remove air bubbles and adjust headspace

if needed, leaving ½” empty. Use a plastic knife or special bubble remover tool. Do not use metal knives or spoons.

• 6. Wipe the rims (top surface) of the jars with a dampened clean paper towel, to make sure no food or liquid is on them. This could interfere with sealing.

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Place Lids on Jars 1. Remove the pretreated lids from the warm

water 2. Apply the lids to the tops of the jars.

3. Tighten the ring bands over the lids until “fingertip-tight” and snug. DO NOT over tighten and cut through the warm gasket.

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Place Jars in Canner Water Temperature should be about

180°F (simmering)

Carefully add the jars to the canner, using a jar lifter.

Keep jars straight up; do not tilt.

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Processing

Turn the heat on high and bring the water in the canner to a full boil over the jars.

After the water is fully boiling, process the jars for the required process time.

The water must never stop boiling. If it does, return the water to a boil and start timing the process again.

After all the jars are in the canner, make sure the water is 1 to 2 inches over the tops of the jars. Place the lid on the canner.

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Removing Jars Turn off the burner.

Remove the lid, turning away from you to avoid getting steam in your face Leave the jars in the canner for 5 minutes.

Using the jar lifter, remove the jars from the canner, not tilting

Place on a thick clean towel, or plastic or wooden cutting board to cool. Do not sit the jars directly on a cool surface.

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Cooling Jars If jar seals properly, the lid will be curved

inward and there will be a clear ringing sound when tapped.

Let jars sit undisturbed while they are cooling (between 12-24 hours).

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Storing Home Canned Food Remove ring bands from sealed jars

Gently wash the lid area andthreads of the jar removing any food or liquid residues

Rinse and dry; label and date

Store without ring bands in a cool, dark, dry place

Refrigerate unsealed jars

Avoid temperature extremes

For best quality, use within a year

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Disclaimer and Credits Disclaimer:

Trade and brand names are used only for information. The Cooperative Extension Service, University of Georgia College of Agricultural & Environmental Sciences and College of Family & Consumer Sciences, and the U.S. Department of Agriculture do not guarantee nor warrant published standards on any product mentioned; neither does the use of a trade or brand name imply approval of any product to the exclusion of others which may also be suitable.

Document Use: Permission is granted to reproduce these materials in whole or in

part for educational purposes only (not for profit beyond the cost of reproduction) provided the author and the University of Georgia receive acknowledgment and this notice is included:

Reprinted (or Adapted) with permission of the University of Georgia. Andress, E.L. 2003. Freezing fruits and vegetables at home (slides). Athens, GA: The University of Georgia, Cooperative Extension Service.

This material is based upon work supported by the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture, under Agreement No. 00-51110-9762.

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Photography Credits

Elizabeth Andress and Elaine D’Sa, National Center for Home Food Preservation, University of Georgia.

Information Staff, Agricultural Research Service, USDA.

North Caroline State University