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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.
Syrup
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.
Overprocessing
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 Cooperative Extension Whatcom County at 360/676-6736.
Information in the handout obtained from the USDA Complete Guide to Home Canning.
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