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TROUBLESHOOTING   CANNING BASICS

Understanding the basics of canning as outlined in the Canning Introduction and using only reliable, tested recipes will, in most cases, result in successful home canning. However, problems can occur, which can be frustrating and disappointing. See the list below to find your circumstance and what may have caused the problem. Be sure to make a note of the remedy to avoid repeating the same situation.

IMPORTANT: If you cannot find a solution to your canning problem below and have an urgent need for information, contact our Consumer Service Department at 1-800-877-0441. Our business hours are Monday through Friday, 8 a.m. to 4 p.m., central time. If it is after business hours and you question the safety of the food you've canned, store the cooled jars in the refrigerator and contact us during business hours. 

1. Loss of liquid in jars during processing


Liquid loss can occur for several reasons:

  • Jars were packed too solidly with food or were overfilled.
    Allow 1⁄2-inch headspace for all fruits and tomatoes, and allow 1-inch for vegetables, meat, and fish. This is necessary since food expands during canning.
     
  • Failure to work out air bubbles from the filled jars before placement of lids and bands.
     
  • Ring bands were not adjusted according to manufacturer’s directions.
    Bands should be tightened fingertip-tight.
     
  • Canner was not allowed to vent for 10 minutes before the pressure regulator was placed on the vent pipe.
    Venting is necessary to ensure that all air is exhausted from the canner as well as the jars.
     
  • Air was exhausted too vigorously during the 10 minutes of venting.
    Adjust heat to maintain a steady but gentle-to-moderate flow of steam from the vent pipe.
     
  • Pressure fluctuated too much during processing due to:
    • Unsteady heat source
    • Steam leakage from the pressure canner
    • Rapid temperature change, such as drafts or air conditioner blowing on canner
       
  • The adjustable pressure regulator on a Weighted Gauge Canner was allowed to rock too vigorously during processing time.
    Adjustable pressure regulator should rock continuously but gently. See link for reference.
     
  • Pressure in canner was not allowed to drop naturally after processing time expired.
     
  • Failure to allow the canner to remain closed for 10 minutes after pressure had been completely reduced.
If liquid is lost during processing do not open the jar to replace liquid. If all canning procedures have been followed and the lids have sealed, the food is safe to store and eat. However, food that is above the liquid line may discolor during storage, so plan to use those jars first.

Liquid loss of at least half indicates that the processing procedures may not have been followed. Place those jars in the refrigerator and use the food within 2 to 3 days.

 

2. Food floats to top of jar


Food may float to the top of the jar for the following reasons:

  • Fruit was lighter than the syrup used for packing.
    Use firm, ripe fruit and a light to medium syrup.
     
  • Fruit was raw packed rather than hot packed. Raw fruit contains air that is released during heating.
     
  • Fruit was packed too loosely.
    Pack fruit as closely as possible without damaging it.
Floating does not affect the quality of the food.

 

3. Color change in fruits


Apples, pears, and peaches may develop a blue, red, pink or purple tint due to a natural chemical change that occurs in cooking. This is not harmful.

4. Jar(s) did not seal


Jars fail to seal for the following reasons:

  • Jars were packed too solidly with food or were overfilled.
    Allow 1/2-inch headspace for all fruits and tomatoes, and allow 1-inch for vegetables, meat, and fish. This is necessary since food expands during canning.
     
  • Failure to work out air bubbles from the filled jars before placement of lids and bands.
     
  • Food particles were left on the sealing surface of the jar.
    Wipe the sealing surface with a damp cloth or paper towel before placing the lid on the jar.
     
  • Ring bands were not adjusted according to manufacturer’s directions.
    Bands should be tightened fingertip-tight.
     
  • Air was exhausted too vigorously during the 10 minutes of venting.
    Adjust heat to maintain a steady but gentle-to-moderate flow of steam coming from the vent pipe.
     
  • Pressure fluctuated too much during processing due to:
    • Unsteady heat source
    • Steam leakage from the pressure canner
    • Rapid temperature change, such as drafts or air conditioner blowing on canner
       
  • The adjustable pressure regulator on a Weighted Gauge Canner was allowed to rock too vigorously during processing time.
    Adjustable pressure regulator should rock continuously but gently. See link for reference.
     
  • Pressure in canner was not allowed to drop naturally after processing time expired.
Jars that do not seal can be salvaged as long as corrective action is taken within 24 hours of the initial processing. The food can be used at once, refrigerated and consumed within a couple days, frozen, or can be reprocessed. If reprocessing is desired, remove the lid and check the jar sealing surface for nicks. Heat the food, change jars if necessary, and add a new lid. Reprocess using the same processing method and time.

 

5. Jar(s) broke during processing


Jars can break during processing for several reasons:

  • Commercial food jars, such as mayonnaise, pickle, etc. were used instead of the recommended home canning jars.
     
  • Jars were cracked, nicked, or just weakened with age and repeated use.
     
  • Jars were packed too solidly with food or were overfilled.
    Allow 1/2-inch headspace for all fruits and tomatoes, and allow 1-inch for vegetables, meat, and fish. This is necessary since food expands during canning.
     
  • Cold jars were immersed in boiling hot water.
    Filled jars should be hot when placed into the canner. When using the hot pack method of canning the water in the canner should be simmering, about 180°; when using the raw pack method the water in the canner should be about 140°.
     
  • Jars were placed directly on canner bottom rather than on canning rack.
     
  • Air was exhausted too vigorously during the 10 minutes of venting.
    Adjust heat to maintain a steady but gentle-to-moderate flow of steam coming from the vent pipe.
     
  • Pressure fluctuated too much during processing due to:
    • Unsteady heat source
    • Steam leakage from the pressure canner
    • Rapid temperature change, such as drafts or air conditioner blowing on canner.
       
  • The adjustable pressure regulator on a Weighted Gauge Canner was allowed to rock too vigorously during processing time.
    Adjustable pressure regulator should rock continuously but gently. See link for reference.
     
  • Pressure in canner was not allowed to drop naturally after processing time expired.
Although it is unfortunate to lose a jar to breakage, the remaining jars are usually not affected and are safe to use. Remove the jars from the canner and let them cool naturally for at least 12 hours. Once cooled, prepare as usual by removing the band and thoroughly wiping each jar clean with a wet cloth before storing.

 

6. Jar(s) seal, but then unseal during storage


Lids may seal during processing and then unseal during storage for the reasons listed below:

  • Food was processed incorrectly (wrong method or insufficient processing time or pressure).
     
  • Hairline cracks in jars permitted entry of spoilage organisms during storage.
     
  • Tightening screw band after processing dislodged the seal.
     
  • Loss of liquid during processing caused food particles to lodge on rim of jar.
     
  • Thin or uneven layer of sealant on canning lid.
All jars that become unsealed during storage should be considered spoiled and discarded.

 

7. Black deposits on underside of metal lid


The black deposit sometimes found on the underside of a lid is caused by tannins in the food or by hydrogen sulfide which is liberated from the food by the heat of processing.

This deposit is harmless and does not indicate spoilage.

 

8. Jam or jelly has mold or is fermented


Mold can form only in the presence of air. Therefore, jars are not sealed if mold is present.

Discard jams and jellies that have mold. Scooping out the mold and using the remaining jam or jelly is not recommended by USDA and microbiologists.

 

9. Bubbles in the jar after processing


Bubbles often appear in the jar after it is removed from the canner because food is still boiling in the jar. Ordinarily bubbles do not appear once the product has been allowed to thoroughly cool.

 

Canning Index | Canning Introduction | Frequently Asked Questions | Pressure Canning Method
Boiling Water Method | Fruits | Tomatoes and Tomato Products | Vegetables | Meat, Game and Poultry
Fish and Seafood | Stock and Soup | Troubleshooting | Care and Maintenance | Pressure Canner Comparison Guide