Date: June 1988 (Reviewed June 1996)
Source: University of Minnesota
There are several reasons why fruit floats in jars. If the fruit is lighter than the syrup or if it's too ripe, it will float.Other causes of floating include processing too long or at too high a temperature, using a heavy syrup, or packing fruit too loosely.
Floating does not affect the flavor or keeping quality of fruit.But there are ways to prevent it.If fruits are loosely packed into jars, shrinkage during processing will result in floating.So one way to avoid floating is to pack fruit solidly into the jar, as closely as possible without crushing.
Raw packed berries can be pretreated with sugar to reduce floating.The fruit absorbs part of the sugar while some of the water in the fruit is released to form a syrup or juice.
You can also prevent or reduce floating by using firm, ripe fruit for canning, by heating it before packing, and by using light to medium syrups instead of heavy syrups.
After you fill a jar, run a narrow rubber spatula or plastic knife between the food and the jar to drive out the air bubbles.You may then be able to add more fruit and syrup.
If you are canning without a sweetener, make sure the fruit is firm but ripe.If hot-packed fruit is the preferred method, make sure you use the right time and method for processing the particular fruit you're canning.
Here is a summary of ways to prevent fruit from floating in jars: use fresh, ripe fruit; pack the fruit solidly; avoid heavy syrups; pretreat berries with sugar; heat fruit before packing and use the correct time and method for processing.Remember also that floating does not affect the flavor or keeping quality of fruit.
If you have further questions, please contact your county office of the NDSU Extension Service.
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