Introduction to Home Canning with Georgianne Mora
Saturday, June 19, 2010 at GNAT - TV Studio in Manchester, VT
This class will cover water-bath canning for high-acid foods.
Canning is a proven process for preserving foods for long storage without the need for refrigeration.
Because most fresh foods (fruits, vegetables, meats, fish, and dairy) contain a high percentage of water, they are susceptible to quality loss and spoilage. Things that cause spoilage include:
· Moisture loss
· Oxidization (exposure to air)
· Enzymatic activity
· Pathogen growth (yeast, mold, and bacteria)
Methods for preventing spoilage include:
· Inhibiting enzymes and pathogen growth – freezing, dehydration, application of salt/sugar/acid
· Fermentation – encouraging ‘good’ enzyme and pathogen activity
· Vacuum sealing – excludes oxygen and prevents moisture loss
· Exposure to high heat – kills pathogens and destroys enzymes
The canning process kills pathogens and enzymes through the application of high heat AND creates a vacuum-sealed environment.
Canning Methods, Botulism, and Food Acidity
There are two primary methods for canning:
In water-bath canning, sealed filled jars are placed in a large pot of water. The pot and its contents are brought to a boil (212°F) and held there for a period sufficient to expel the air from the jars and kill off pathogens.
The process for pressure-canning is similar, except that a special pressure-canning pot is required. Only a small amount of water is used, and the lid (of the pot) is screwed on tightly so that pressurized steam can build inside the pot. Under pressure, temperatures up to 250°F can be achieved.
Botulism
Every discussion of canning should include a discussion of botulism. Clostridium botulinum is a naturally-occurring bacterium. Botulism is a potentially fatal illness caused by a nerve toxin that is produced by the botulinum bacterium as it multiplies.
The spores of botulinum are present in our soil and water and are generally harmless. The spores require fairly specific conditions to grow:
· A moist, low-acid food
· A temperature between 40° and 120°F
· Less than 2% oxygen
Bacteria, yeasts, and molds are naturally present on most foods, but most are killed off at the boiling-water temperatures achieved in water-bath canning. However, killing botulinum spores requires temperatures between 240° – 250°F (which can only be achieved during pressure-canning). Foods processed using the lower temperature water-bath method will provide an ideal environment for the growth of botulinum unless the food is sufficiently acidic to prevent its growth.
Food Acidity
High-acid foods include most fruits, fruit jams/preserves/marmalades, and pickled vegetables. Low-acid fruits and vegetables will require the addition of some form of acid – lemon juice, vinegar, citric acid – to be considered safe for water-bath canning.
Only high-acid foods should be processed using the water-bath method. To ensure that your food is acidic enough, you should ONLY use proven recipes for canning.
NOTES:
Don’t be tempted to adjust your recipe by adding more low-acid ingredients (onions, peppers, garlic, for example) as this may reduce the overall acidity of the recipe.
Tomatoes, on their own, should be treated as a low-acid vegetable. To be safe for water-bath canning, lemon juice or citric acid should be added.
When canning recipes include vinegar, be sure to use vinegar with an acidity of 5% or higher (this should be noted on the bottle). Rice vinegar, for example, may have an acidity level of @ 4%, which would not be safe for canning.
Canning Equipment
Jars and Lids
Use jars specifically made for canning; other jars may not be properly tempered to handle high heat without breaking. Jars with one-piece or two-piece metal lids or those with rubber gaskets and wire bail or metal clips are all acceptable. Always use new lids; the sealing material deforms on use and cannot be counted on to seal properly a second time. With two-piece lids, the outer rings are reusable. Rubber gaskets can be used over and over again but will lose their ‘squish’ and elasticity over time.
Canning Pot
Use any large, flat-bottomed metal pot with a tight-fitting lid. The pot should be wide enough to hold the jars you intend to process with 1” space between the jars and between the jars and the sides of the pot. The pot should be tall enough that your jars can be covered with water to 1” above their tops, and their should still be room for the water to boil without running over.
Rack
Your canning pot should be fitted with a rack that will keep the bottom of the jars at least ½” off the bottom of the pan, to allow for full circulation of the boiling water during processing. Most canning-specific racks are designed to hold quart jars. Smaller jars will fit awkwardly, not stand upright, and even fall through. Better to get a round wire cake-cooling rack that will fit in the bottom of the pan. If the rack isn’t strong enough to hold all the jars without sagging, lay small wooden spoons or other utensils under it to maintain the space between the bottom of the pan and the jars.
Other Equipment
· Large ladle
· Jar lifter
· Wide-necked funnel
· Sturdy cookie sheets
· Rubber gloves
· Towels and pot holders
· Pots and bowls
· Assorted spoons and knives
All equipment should be washed and dried before using.
Choosing Fruit and Vegetables for Canning
Always choose fruits and vegetables at the peak of freshness. Avoid diseased, shrunken, rotting, or molding produce. Slight bruising on delicate fruits or vegetables is unavoidable. Small blemishes can be cut away.
Freshness is especially important when making pickles. Produce for pickling should be picked as close to processing as possible in order to ensure crispness.
Filling and Sealing Jars
Jars for canning should be clean, dry, and hot, but need not be sterilized unless the contents are to be processed for less than 10 minutes. Wash jars in hot soapy water then rinse very well with hot water, especially if your soap is highly perfumed – residual scents will linger in the jars and throw off the flavor of your food. Drain the jars in a dish drainer, then stand them upright on a sturdy cookie sheet and place them in an oven heated to 225°F. Leave the jars in the oven until ready to use, for at least 20 minutes.
Lids should be washed and kept in a pan of barely simmering water until ready to use. The hot water is intended to soften the sealing material. Alternatively, you can wait until your jars are filled, then place your lids in a heat-proof bowl and pour boiling water over them. Pre-heating isn’t necessary when using rubber gaskets.
Packing Method
Raw Packing (also called ‘cold packing’)
Raw packing is the practice of filling jars tightly with freshly prepared, but unheated, food – usually raw fruits and vegetables. Raw packing is best suited for pickles, since pickles require minimal processing due to the very high acid content – the crispness of the raw vegetable can be maintained. Raw packing is also recommended for small whole fruits, as it minimizes damage to the fruit (the jar is then filled with syrup). Raw packing is also used to pack vegetables for processing in a pressure canner.
Hot Packing
Hot packing is the practice of filling jars loosely with hot just-prepared food. Cooking food first helps to remove air from food tissues, shrinks food, helps keep the food from floating in the jars, increases vacuum in sealed jars, and improves shelf life. Preshrinking food also permits filling more food into each jar.
Jams and preserves are always hot-packed.
Whether food has been raw-packed or hot-packed, any additional liquid (juice, syrup, or water) should be heated to boiling before adding it to the jars.
Filling and Head Space
Remove jars from oven just before filling.
When filling jars with hot food or liquid, some ‘head space’ needs to be left at the top to allow for expansion during processing. Stand a funnel in the top of a jar and use a large ladle to fill the jar to within ¼” of the top for half-pints, up to ½” for pint and quart jars. Keep filling jars until all food is packed.
If raw-packing, pack the vegetables or fruit as tightly as possible without crushing or damaging it, then ladle in the hot liquid, allowing head space as described.
Lids and Sealing
To ensure a good seal, the rims of the jars should be perfectly clean before placing the lids on. Wipe the rims clean with a damp dishtowel or paper towel.
Place the preheated lids on the jars and screw them on just finger-tight. One-piece lids should be a little tighter. If using jars with rubber gaskets, place the gaskets on the jars and clamp down the bail or attach the metal clips.
Processing the Jars
Processing Times
Most recipes for high-acid foods call for 10 minutes processing for half-pint jars, 15 minutes for pint jars. In general, processing times assume the user is at an altitude no greater than 1,000 feet above sea level. At higher altitudes, water boils at a lower temperature, which may not be sufficient to kill bacteria in the specified time. Therefore, processing times should be increased as altitude increases:
Altitude Increase Processing Time
1,001 – 3,000 feet 5 Minutes
3,001 – 6,000 feet 10 Minutes
6,001 – 8,000 feet 15 Minutes
8,001 – 10,000 feet 20 Minutes
Water-Bath Canning
NOTE: It’s wise to fill and heat your canning pot before you start filling your jars.
1) Fill the canner halfway with water.
2) Preheat water to 140°F for raw-packed foods, 180°F (simmering with steam) for hot-packed foods. Starting raw-packed foods at a higher temperature may not allow them sufficient time to heat completely during processing.
3) Load filled jars into the canner one jar at a time, using a jar lifter.
4) Add more boiling water, if needed, so the water level is at least 1” above jar tops.
5) Cover with the canner lid and turn heat to its highest position until water boils vigorously.
6) Set a timer for the number of minutes required for processing the food.
7) Lower the heat setting to maintain a gentle boil throughout the processing time.
Add more boiling water, if needed, to keep the water level 1” above of the jar lids.
9) When the processing time has elapsed, turn off the heat and remove the canner lid. Allow the jars to sit in the canner for 5 minutes.
10) Using a jar lifter, remove the jars and place them on a metal cooling rack or a folded dishtowel (never put hot jars directly on the counter, as the temperature differential may cause them to break), leaving at least 1” between the jars during cooling. Keep away from air drafts and let the jars cool at room temperature.
11) Once the jars are completely cooled, check the seals. With two-piece lids, press gently in the center of the lid to ensure that the lid is sucked down. With other lid and jar types, gently check that the lids are on tight.
12) Wipe the jars clean, if necessary, and store them in a cool place away from direct sunlight.
CAUTION, AVISO, ATTENTION:
If, at any time during storage, the jars show signs of leakage, or if the lids bulge, THROW
THEM AWAY. If, when you open a jar, it hisses, bubbles, or sprays as though the contents
have expanded (a slight hiss on opening is normal as the vacuum releases), or if there is any
sign of mold or fizzing or fermentation, THROW THEM AWAY. NEVER sample the contents
of an ‘iffy’ jar!
Recipes
Pickled Rhubarb
1 lb. fresh rhubarb, washed
½ cup sugar
2 Tbsp. kosher salt
2½ cups cider vinegar
1-oz. piece fresh ginger
1 tsp. whole cloves
½ tsp. dried red pepper flakes
Slice the rhubarb on the diagonal into 1” pieces. Pack into clean 1-pint jars.
Peel the ginger and slice into thin rounds.
In a saucepan, combine the vinegar with the sugar and salt and heat gently, stirring, until the sugar and salt are dissolved. Add the ginger and spices and bring to a boil; boil for 2 minutes.
Ladle the hot syrup over the rhubarb in the jars, leaving ¼” head space. Seal and process the jars for 15 minutes, adjusting for altitude if necessary. Store in a cool, dark place for 1 month before eating.
Makes 2 pints.
Strawberry Jam
from the Ball pectin package
NOTE: Jams and jellies made with commercial pectin have a very specific ratio of sugar/acid/pectin. Don’t be tempted to change the quantities, or your jam may not set properly. If doubling the recipe, use two separate pans.
3¾ cups crushed strawberries (about 4 lbs.)
¼ cup lemon juice
7 cups sugar
1 3-oz. pouch liquid fruit pectin
Combine the strawberries, lemon juice, and sugar in an 8-qt. saucepan and bring to a full rolling boil over high heat, stirring frequently. Add the pectin all at once, squeezing the entire contents from the pouch. Continue hard boil for 1 minute, stirring constantly. Remove from heat.
Fill and seal jars. Process for 10 minutes, adjusting for altitude if necessary.
Makes about 7 half pints.
Links
My cooking blog, ‘A Cooking Life’, includes some recipes for jams, etc., and also has instructions for making sun-cooked jams.
http://acookinglife.typepad.com
There is a world of information about canning on the web, and blogs with good recipes abound. Google is your friend, but here are a few links to get you started:
http://www.uga.edu/nchfp/how/can_home.html
http://www.pickyourown.org/allaboutcanning.htm
http://www.canningpantry.com/home-canning-articles.html



