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Washington State University

Food Safety Resources

Reasons Why Fruit Turns Dark

1. Fruit not processed long enough.
2. Processing temperature not high enough.
a. Water not at rolling boil at beginning of processing.
b. Water not boiling throughout processing time.
3. Time was not counted accurately.
a. Started counting before rolling boil.
b. Did not process long enough.
c. Did not make adjustment for altitude over 1000 feet.
4. Boiling water level not one to two inches above cap of jar during processing.
5. Packing fruits raw that should be precooked (pears, apples, and pineapples).

For more information on any of the above situation you may have questions on or need more information, please call the Whatcom County Extension at (360) 676-6736.


Why Home Canned Fruit Floats

Home canned fruit sometimes has a tendency to float. This is not necessarily an indication of food spoilage or poor canning procedures but it can be visually disturbing. Fruit floating could be caused by one, or a combination of, several factors. Some fruits such as apricots, berries and rhubarb have natural buoyancy due to air in the cells. Floating can be controlled by taking into consideration the following:
Ripeness and maturity of the fruit
Use only unblemished fruit at the peak of ripeness.

Packing the jar
Loosely packed jars and improperly exhausted jars cause fruit to float. When putting the fruit in the jar, pack it snugly tight and then add your liquid. After filling the jars to the correct headspace, exhaust any trapped air bubbles by running a plastic chopstick or spatula around the inside of the jar. This dislodges any air under pieces of fruit. You may notice after exhausting that the fruit settles. You may need to add more fruit and/or liquid to maintain prooer headspace and tightness of pack. If you do add more product or liquid, exhaust again before putting on the two-piece lid.

Raw pack vs. Hot Pack
All fruit contains air in the cells. Raw packed fruit is put into the jar uncooked. It appears to fill the jar. During processing, the air present in the fruit is cooked out. The fruit shrinks in size creating more room in the jar, allowing the fruit to rise to the top. Sometimes the fruit rises above the syrup causing discoloration. Hat packed fruit is heated prior to being packed in jars. The fruit will have less air and will be more dense, lessening the amount of float. An additional benefit is more fruit can be packed in the jar and processing time is usually reduced.

A heavier or more sugary syrup tends to prevent floating. Light syrups, juice syrups or water creates an environment in which fruit wants to equalize its sugar content with its environment. The fruit releases its own sugar, becoming lighter.

Be exact according to your recipe and the latest Washington State University/USDA recommendation. Overcooking the fruit makes the fruit lighter by destroying the cell structure. This also gives the finished product a ragged appearance.

Possible Food Spoilage
In addition to the unappealing appearance, floating can contribute to food spoilage. When the fruit rises above the syrup, discoloration and drying out can occur. In extreme cases the fruit can rise up and touch the lid and even dislodge the lid. Air in the jar caused by a broken seal also causes fruit to float. Check seals before serving. Also look for a bulged or rusting lid and any leaking. Store all jars with the rings off once a seal has occurred. If spoilage has occured dispose of the product correctly using the current USDA/Washington State University recommendation.

For further information contact WSU Extension Whatcom County at (360) 676-6736.
Information in the handout obtained from the USDA Complete Guide to Home Canning.


Reasons for Liquid Loss From Jars

There are many reasons for loss of liquid from jars during processing:

  1. Leaving wrong amount of headspace when filling jars.
    1 inch headspace for LOW ACID foods such as most meats and vegetables.
    1 ¼ inch headspace for chicken and rabbit.
    ½ inch headspace for HIGH ACID foods such as fruits, tomatoes, and fruit juices.
    ¼ to ½ inch headspace for pickles and relishes as directed.
    ¼ inch headspace for jams and jellies.
    Check USDA instructions for each food.
  2. Food packed so tightly that liquid did not fill the spaces between pieces of food.
  3. Starchy foods may absorb some of the liquid.
  4. Liquid added to cover cold raw food was not hot enough when placed in canner.
  5. Air bubbles not removed at time of packing. Use a plastic spatula around the inside of the jar to remove air bubbles.
  6. Jars processed in boiling water bath not covered with 1-2 inches of water.
  7. Pressure canner not sufficiently exhausted.
  8. Allowing pressure to fluctuate or sudden lowering of temperature during processing.
  9. Too sudden changes in temperature when processing period is over. (If the canner cools too quickly while the contents of the jar remain at a much higher temperature, the liquid will boil over. The contents of the jar and the canner have to cool down gradually from 240°F to 212°F. The “coming down” period should be gradual and even.)
  10. Opening the petcock before the pressure has returned to zero. (When the pressure has returned to zero, open the petcock very cautiously and if steam escapes, close and wait a few minutes. This avoids cooling the atmosphere around the jars too fast which causes liquid to boil over.)
  11. Letting the canner stand too long after pressure returned to zero. It should be opened within a couple of minutes after it returned to zero pressure.
  12. Removing the jars too quickly after removing the cover. Let the jars remain in the canner a few minutes after removing the cover, or until the boiling in the jars is less vigorous.
  13. Having an inaccurate dial pressure gauge that does not return to zero. (The petcock in this case could be opened too soon or not soon enough.)
  14. Not removing particles of food, seeds, seasonings, or pulp of fruit from top of jar or threads with damp paper towel before putting on lid. Particles left on rim of jar can because of lid sealing, then loosening..
  15. Screwing band too tight can cause lid to buckle. A band MUST be tight enough to hold the rubber sealing compound closely against the top of the jar. However, if the band is forced as far as it can be turned with a strong hand, the jar cannot vent. When the jar can’t vent, pressure within the jar causes the lid to buckle. We suggest you tighten bands comfortably tight to prevent buckled lids.
  16. Not screwing band tight enough. As in No. 16, we suggest you tighten band comfortably tight so rubber sealing compound will be held closely against the top of the jar.
  17. Insufficient heat to seal the lid such as “open kettle”. Do follow recommended processing times and methods.
  18. Leakage of steam from pressure canner.

Loss of liquid may cause the food to darken, but does not interfere with the keeping qualities unless the liquid that has been lost has caused food, grease or seeds to lodge under the lid and prevented a seal from forming. If liquid has been lost, do NOT open jar at the end of the processing to replace liquid. Opening the jar will result in spoilage of the food unless you use the contents immediately.

NOTE: Fruit packed raw must have 1 ½ inch of space for syrup – fruit juice cooks out of fruit, and fills jar with liquid. Otherwise too much liquid will boil over and siphoning will cause loss of liquid and possible sealing failures.

For more information on any of the above situation you may have questions on or need more information, please call the Whatcom County Extension at (360) 676-6736.


Reasons Why Jars Do Not or Cannot Seal

1. Failure to read and follow instructions on package for using caps and lids. Taking for granted all home canning caps are alike and are used exactly the same way is one cause of sealing failure.
2. Using make shift supplies:
a. Off-standard jars called packers’ jars (mayonnaise jars)
i. Mouths are not accurate width. Lids ride on edge.
ii. Sealing edges not level – have dips.
b. One-piece caps instead of screw bands.
3. Using screw bands that are rusty or bent.
4. Using jars with damaged sealing edges.
5. Screwing bands on too loosely.
6. Not cleaning the edge of jar.
7. Siphoning of liquid, causing food particles to lodge between lid and sealing edge of jar.
8. Lack of heat in processing.
9. Screwing bands on too tightly (they may buckle and not seal).

For more information on any of the above situation you may have questions on or need more information, please call the Whatcom County Extension at (360) 676-6736.


Acidification of Home Canned Tomatoes
Tomatoes differ in acidity depending on the variety and growing conditions. Although tomatoes usually are considered an acid food, some are now known to have pH values slightly above 4.6. Therefore, if they are to be canned as acid foods, they must be acidified to a pH of 4.6 or lower with bottled lemon juice or citric acid. Properly acidified tomatoes are acid foods and can be safely processed in a boiling-water bath canner.

To ensure safe acidity in whole, crushed or juiced tomatoes, the USDA/WSU recommends adding acid in the form of bottled juice (never fresh) or citric acid power in the following increments:

1 tablespoon bottled lemon juice per pint
– or –
¼ teaspoon citric acid powder per pint

2 tablespoons bottled lemon juice per quart
– or –
½ teaspoon citric acid powder per quart

The acid may be added at the bottom of the pack or at the top. Always put the acid directly in the jar and not into the batch. The movement of the contents during processing will distribute it.

Some flavor changes may occur with the addition of the acid. The addition of sugar, (1 teaspoon per pint, 2 teaspoons per quart), can offset the tartness. You may add salt to enhance the flavor at a rate of ½ teaspoon per pint and 1 teaspoon per quart. Salt is added for taste only, and does not aid in preservation.

ADDING ACID IS NOT A CRUTCH! Always use current USDA/WSU recommendations for processing times and methods. Never take shortcuts or reduce processing times.

In 1998, the USDA and Washington State University changed the processing times for water-bath canning and pressure canning of tomatoes. Check with your local Extension Office for the current processing times.

For further information contact Washington State University Whatcom County Extension at (360) 676-6736. Low cost publications are available for purchase at the Whatcom County Extension Office. Volunteers are available during the canning season to answer your questions.