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Canning procedures

Canning in practice

Canning procedure No.1

  • Clean the jars
  • Pack product to within ¼” / 0.5cm of top and seal.
  • Heat process in boiling water bath canner for 15 minutes (or check chart below). Count time from when water returns to boil after putting the jars in the water.
  • Allow the jars too cool down to room temperature slowly.
  • A day after canning test for the lids are closing properly. Press the lid down, if it pops back up then the jar is not sealed properly. Repeat the canning process or use the food up.
  • Store the jars in a dark cool place.

Canning procedure No.2 (for cooked food only, like jam)

  • Clean and sterilize the jars by boiling them for 15 minutes and keep them hot.
  • Pack product to within ¼” / 0.5cm of top and seal.
  • Heat process by thermally isolate the jars for 24-48 hours. Wrap them in clothes and tuck them under several highly isolating covers like a duvet.
  • Take them out when cooled to room temperature then test if the lids are sealing properly. Press the lid down, if it pops back up then it is not closed properly. Repeat the canning process or use the food up.
  • Store the jars in a dark cool place.

Canning science

Jam, marmalade, preserves and conserves are fruit products preserved by sugar. These products differ in gel consistency, ingredients and how the fruit is prepared. They are easy to make at home.

  • Jam is made out of crushed or ground fruit and usually has thick consistency due to high pectin content.
  • Marmalade is a jelly with pieces of fruit suspended in it. Citrus peel and juice is frequently the basis of marmalade.
  • Preserves contain whole fruit or small pieces of fruit in a thick sugar syrup.
  • Conserves are jams made from a mixture of fruits. They usually contain citrus fruit, nuts and raisins.

Ingredients and their roles

Fruit gives the product its special flavor and provides pectin for thickening.

Pectin provides thickening or gel formation.

  • Every fruit contains some pectin.
  • Apples, crabapples, gooseberries, some plums, highbush cranberries and citrus peel contain large amounts of pectin.
  • Fruit like blueberries, strawberries, cherries or huckleberries contain little pectin. Thicker products can be made with these fruit by combining them with fruit rich in pectin or with powdered or liquid pectin.

Acid must be present to form gel in marmalade and thickenings in jam, preserves and conserves.

  • For fruit lacking in natural acid, like strawberries, recipes call for lemon juice or other citrus fruit.
  • Commercial pectin products contain organic acids that increase the acid content of fruit.

Sugar aids in gel formation, develops flavor by adding sweetness, and helps preserve texture but otherwise not necessary. Adding syrup to canned fruit helps to retain its flavor, color, and shape. Sugar is not needed for safety because the heat used in canning is what kills microorganisms and preserves the product. If you are on a special diet or are just watching your calories you may want to try canning without sugar; it is a good option.

  • Corn syrup or honey can replace half of the sugar in a recipe.
  • Use light colored, mild-flavored honey; note: too much honey can overpower the fruit flavor.

Canning jam, marmalade, preserves and conserves

Filling jars and heat processing

Proper heat processing seals in food quality and destroys bacteria, yeast and molds that can cause food to spoil.
Paraffin wax is no longer recommended for sealing jars. Paraffin does not form a complete seal and does not protect against mold growth and toxin production in jelly. The process is a potential health risk.

Processing time in a boiling water canner for jam and jelly

Jar size: Half or quarter pints

  • 0-1000 feet / 0-300m | Processing time: 5 minutes.
  • 1001-2000 feet / 301- 600m | Processing time: 6 minutes.
  • 2001-3000 feet /601- 900m | Processing time: 7 minutes.

Jar size: Pints

  • 0-1000 feet / 0-300m | Processing time: 10 minutes.
  • 1001-2000 feet / 301- 600m | Processing time: 11 minutes.
  • 2001-3000 feet /601- 900m | Processing time: 12 minutes.

Processing time in thermal isolation:

  • 24 to 48 hours: When the jars reach room temperature the heat processing is done.

Jar cleaning

Before reuse, wash empty jars in hot water with detergent and rinse well by hand, or wash in a dishwasher. Unrinsed detergents may cause unnatural flavors and colors. These washing methods do not sterilize jars. Scale or hard-water films on jars are easily removed by soaking jars several hours in a solution containing 1 cup of vinegar (5 percent) per gallon of water.

Sterilization of empty jars

All jams, jellies and pickled products processed 10 minutes or less should be filled into sterile empty jars. To sterilize empty jars, put them right side up on the rack in a boiling-water canner. Fill the canner and jars with hot (not boiling) water to 1” / 2.5cm above the tops of the jars. Boil 10 minutes at sea level. At higher elevations, boil 1 additional minute for each additional 1,000 feet / 300m elevation. Remove and drain hot sterilized jars one at a time. Save the hot water for processing filled jars.

Empty jars used for vegetables, meat and fruit to be processed in a pressure canner need not be pre-sterilized. It is also unnecessary to pre-sterilize jars for fruit, tomatoes, and pickled or fermented food that will be processed 10 minutes or longer in a boiling-water canner.

Lid selection, preparation and use

The common self-sealing lid consists of a flat metal lid held in place by a metal screw band during the process. The flat lid is crimped around its bottom edge to form a trough, which is filled with a colored gasket compound. When jars are processed, the lid gasket softens and flows slightly to cover the jar-sealing surface, yet allows air to escape from the jar. The gasket then forms an airtight seal as the jar cools. Gaskets in unused lids work well for at least five years from date of manufacture.

To prepare lids, wash them with soapy water and keep at room temperature until ready to be used, preheat the metal canning lids is not necessary.

The gasket compound in older unused lids may fail to seal on jars. Buy only the quantity of lids that will be used in a year. To ensure a good seal, carefully follow the manufacturer’s directions in preparing lids for use. Examine all metal lids carefully. Don’t use lids that are old, dented, deformed or have gaps or other defects in the sealing gasket.

After filling jars with food, release air bubbles by inserting a flat plastic (not metal) spatula between the food and the jar. Slowly turn the jar and move the spatula up and down to allow air bubbles to escape. Adjust the headspace and then clean the jar rim (sealing surface) with a dampened paper towel. Place the lid, gasket down, onto the cleaned jar-sealing surface. Uncleaned jar-sealing surfaces may cause seal failures.

Fit the metal screw band over the flat lid. Follow the manufacturer’s guidelines enclosed with or on the box for tightening the jar lids properly. Do not re-tighten lids after processing jars. As jars cool, the contents in the jar contract, pulling the self-sealing lid firmly against the jar to form a high vacuum. If rings are too loose, liquid may escape from jars during processing, and seals may fail. If rings are too tight, air cannot vent during processing, and food will discolor during storage.

Overtightening also may cause lids to buckle and jars to break, especially with raw-packed, pressure-processed food.

Fitting screw band

Screw bands are not needed on stored jars. They can be removed easily after jars are cooled. When removed, washed, dried and stored in a dry area, screw bands may be used many times. If left on stored jars, they become difficult to remove, often rust, and may not work properly again.

Cooling jars

When hot jars are removed from a canner, don’t re-tighten their jar lids. Re-tightening of hot lids may cut through the gasket and cause seal failures. Cool the jars at room temperature for 12 to 24 hours. Jars maybe cooled on racks or towels to minimize heat damage to counters. The food level and liquid volume of raw packed jars will be noticeably lower after cooling. Air is exhausted during processing and food shrinks. If a jar loses excessive liquid during processing, don’t open it to add more liquid. Check for sealed lids as described below.

Testing jar seals

After cooling jars for 12 to 24 hours, remove the screw bands and test seal. Press the middle of the lid with a finger or thumb. If the lid springs up when the finger is released, the lid is unsealed.
Reprocessing unsealed jars

If a jar fails to seal, remove the lid and check the jar sealing surface for tiny nicks. If necessary, change the jar, add a new, properly prepared lid, and reprocess within 24 hours using the same processing time.

Headspace in unsealed jars may be adjusted to 1½” / 3cm and jars could be frozen instead of reprocessed. Foods in single unsealed jars could be stored in the refrigerator and consumed within several days.

Preparing with or without added pectin

The two main methods for preparing jam, marmalade, preserves and conserves are by cooking fruit and sugar either:
• With no added pectin.
• With added pectin.

No added pectin

Jam, preserves, conserves and marmalade are made without added pectin:

  • Require longer cooking.
  • Have a slightly different flavor from those with added pectin.
  • They also yield a less finished product.
  • The product is done when the temperature reaches 220–222 °F / 104 – 105 °C.

Added pectin

When using powdered or liquid pectin, be sure to follow the directions that come with the pectin product. The order of combining ingredients depends on the type of pectin used.

Successful preparation of pectin-added jam, marmalade, preserves and conserves depend on accurate timing. Begin counting time when the mixture reaches a full rolling boil that cannot be stirred down.

The jam is done when 2 big drops slide together and form a sheet that hangs from the edge of the spoon.

Making Freezer Jam

Freezer or refrigerator jam does not require cooking the fruit.

Raspberries, strawberries and blackberries work well in uncooked freezer jam recipes. Uncooked jam must be stored in the refrigerator or freezer. They’ll last for several weeks in the refrigerator and up to a year in the freezer. Once the container is opened, keep refrigerated and use the jam within 2-3 weeks. If it is kept at room temperature, they will mold or ferment in a short time.

Prepare the fruit

  1. Sort and wash fully ripe fruit. Drain.
  2. Remove caps and stems from berries and crush.
  • If we use frozen fruit, these first steps have already been done.
  • If the fruit was frozen with sugar added: The container should have been labeled with how much fruit and sugar had been added before freezing. Subtract that amount of sugar from what is called for in the freezer jam recipe.

Follow the instructions on the powdered pectin package or use this basic recipe.

Uncooked jam with powdered pectin recipe

  • 2 cups crushed berries (about 1-1/2 quarts of berries).
  • 4 cups sugar.
  • 1 package powdered pectin.
  • 1 cup cold water.

To make the jam:

  1. Add 2 cups of prepared fruit to a large mixing bowl.
  2. Add the sugar and mix well.
  3. Let the mixture stand for 20 minutes, stirring occasionally.
  4. Dissolve powdered pectin in 1 cup cold water in a saucepan.
  5. Bring it to boil and keep boiling it for 1 minute.
  6. Add pectin solution to the fruit and sugar mixture.
  7. Stir vigorously for 2-3 minutes until the sugar is completely dissolved and no longer grainy.

Put the jam into containers and freeze:

  1. Pour the jam into clean freezer containers or canning jars, leaving 1/2-inch headspace. (Plastic freezer containers with tight-fitting lids work well for storing freezer jams and jellies.)
  2. Cover the containers and let stand for 24 hours, or until the jam has set and become firm.
  3. Freeze containers.
  4. This quantity makes about 5 or 6 half-pint jars or freezer containers.

Freezer jam is less firm than cooked jam but has more of a fresh-fruit taste.

To use jam:

  • When jam comes out of the freezer, thaw overnight in the refrigerator.
  • If the jam is too firm, we can soften it by stirring. If it tends to separate, stirring will blend it again.
  • If freezer jam is too soft, bring the jam to a boil in a saucepan for 1 minute. It will thicken again as it cools down.

Low-sugar jam

If we want to reduce the amount of sugar, use a modified low- or no-sugar pectin that allows us to do so. Follow the pectin package directions carefully.
Follow these tips to create successful jams and jellies from frozen fruit or juice:

  • The best frozen fruits for jam or jellies are blueberries, red and black currants, gooseberries and rhubarb.
  • Before freezing fruit, measure the fruit and label the container. Many fruit collapse as they thaw and may create an inaccurate measure.
  • Jam and jellies from frozen fruit and juice are better if no sugar is added to the fruit and juice before freezing.
  • When freezing fruit for jelly or jam, use ¼ under-ripe and ¾ ripe fruit.
  • Thaw frozen fruit in the refrigerator until only a few ice crystals remain. Follow directions for the type of jam is being made and follow the recommended proportions of fruit (measured before freezing), pectin and sugar.

When making jelly from frozen juice, thaw frozen juice in the refrigerator overnight. Measure juice and use it immediately in recommended proportions with sugar and pectin.


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