Nothing can be more frustrating when canning food than finding you do not have enough liquid left in your jars to cover the food. This is one of the most common problems canners experience says Janie Burney, a professor and food preservation specialist with the University of Tennessee Extension Department of Family and Consumer Sciences.
 
In a few short questions and answers, Burney explored the answer to this and other related questions.
 
Question:  Why do I lose liquid from my canned green beans when I process them?
Burney: It could have to do with the change in pressure. When you remove the lid of the pressure canner and there is still pressure inside the canner and jars, the change in pressure can force liquid out of your jars. Make sure you allow enough time for your canner to depressurize, but don’t try to force it. Forcing a canner to depressurize by placing it in a draft, on an air conditioning vent, or in cold water leads to loss of liquid from jars and may result in unsafe food or food spoilage. Forcing a canner to cool to quickly also can cause it to warp and not maintain pressure.   

Question:  How long does it take for a canner to depressurize?
Burney:  It depends on the canner. Standard-size heavy-walled canners require about 30 minutes when loaded with pints and 45 minutes when loaded with quarts. If you have an older canner that is heavy and does not have a dial gauge to determine when the pressure drops, use a timer. Newer, thin-walled canners cool more rapidly and have vent locks. Vent locks have a piston that drops to a normal position when the canner is depressurized.
 
Question: How soon after it depressurizes should I remove the weight from the vent port or open the petcock.
Burney: Wait ten minutes after the canner has depressurized. Remove the weight or open the petcock. Unfasten the lid and remove it carefully so that steam does not burn your face or hands.

Question:
  I allow my canner to depressurize correctly, but I still lose liquid. What is causing this?
Burney: The pressure may be fluctuating during processing. Closely watch the canner during processing to maintain a steady pressure at or slightly above the correct gauge pressure. If your canner has a weighted gauge rather than a dial gauge, follow the manufacturer’s directions for how the weighted gauge should move and how often it should jiggle or rock.
Also, pay attention to how you pack your jars when using a pressure canner or water-bath canner. Work the air bubbles from jars before processing them by running a plastic spatula between the food and the jar. Avoid over packing the jars because food packed too tightly in jars can boil over during processing and start a siphon.
 
Be sure you have enough liquid to fill in around the solid food in the jar and cover the food. It takes from ½ to 1 ½ cups of liquid for a quart jar.
 
Question:  What happens if I lose liquid from my jars? Is it safe to eat?
Burney: If you lose liquid from your jars, do not replace the liquid. Loss of liquid does not cause food to spoil. However, the food above the liquid may darken. If the loss is excessive (if at least half of the liquid is lost), refrigerate the jars and use within 2 to 3 days.
 
For more information about home canning and food preservation, contact your local county UT Extension Office.

UT Extension provides a gateway to the University of Tennessee as the outreach unit of the Institute of Agriculture. With an office in every Tennessee county, UT Extension delivers educational programs and research-based information to citizens throughout the state. In cooperation with Tennessee State University, UT Extension works with farmers, families, youth and communities to improve lives by addressing problems and issues at the local, state and national levels.

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Contact:
 
Dr. Janie Burney, Department of Family and Consumer Sciences, 865-974-7402, jburney@utk.edu
 
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