Food preservation and canning troubleshooting guide

Reprocessing procedure

If a lid fails to seal on a jar, you have 3 options:

1. Remove the lid and check the jar-sealing surface for tiny nicks. If necessary, change the jar, add a new, properly prepared lid, and reprocess within 24 hours using the same processing time.

2. Adjust headspace in unsealed jars to 1½ inch and freeze instead of reprocessing.

3. Refrigerate unsealed jars and eat canned product within seven days of refrigeration.

Possible causes

• Use of jars other than official canning jars or lids.
• Chipped or uneven rim on jar.
• Screw bands are rusty or bent, causing poor contact.
• Bands not screwed down tightly enough before processing.
  • Turn band until you meet resistance, then turn it one-quarter turn.
• Rim on jar not clean. Wipe rim well before putting lid on.
• Liquid leaks out of jar during processing, leaving food particles on the sealing edge.
• Insufficient heat during processing - air not removed from jar so a vacuum seal never forms.
  • Remove air by inserting a rubber spatula or plastic knife inside the jar; gently lift food to remove any trapped air.
• Lids were improperly prepared before placing them on rims. Follow manufacturer's directions to prepare lids.
• Rapid, forced cooling of a pressure canner can cause a rapid pressure and temperature change inside the canner, causing the liquid to "boil" out of the jars, leaving particles on the sealing rim and unsealing the jars.
  • Do not force canners into cooling rapidly by submerging them in water.
• Insufficient processing of raw-packed food.
  • The air may not have been completely driven out of the food, leaving residual air in the jar so the seal does not form.
• Use of canning procedures that are not recommended, such as open-kettle canning and oven canning.
• Incorrect amount of headspace.

Possible causes

Processing at an incorrect temperature due to:

• Inaccurate pressure canner gauge.
  • Dial gauges should be checked every year. Free testing available. Contact your local Extension office.
• Failure to exhaust canner.
• Failure to make altitude adjustment.
  • In Minnesota, process at altitudes between 1001-2000 feet.
• Heat source fluctuates - inaccurate pressure or fluctuating pressure.
• Water not at a rolling boil when jars are put into water bath canner.
• Water not covering jar caps by 1 inch throughout processing.
• Water not at full boil throughout processing.
• Not processing long enough.
• Use of canning procedures which are not recommended.
  • Recommended procedures (USDA) are based on the time it takes to achieve a temperature which will sterilize the food in the jar.

Improper cooling of jars after processing:

• Failure to remove jars from canner when processing time is up or when pressure gauge reads 0.
• Failure to set jars at least 1 inch apart during cooling.
• Covering jars, which retains heat so vacuum does not develop.
• Attempting to cool either the canner or the jars very rapidly.

Other reasons for spoilage:

• Using damaged (freeze-damaged), spoiled, underripe or over-ripe food.
  • The pH may not be correct for the type of processing you used (water-bath vs. pressure).
• Ingredients were added that were NOT in an approved recipe.

Possible causes

• Jars filled too full (leave recommended headspace).
• Fluctuating pressure in a pressure canner. Not exhausting pressure canner long enough.
  • Allow steam to escape for 10 minutes before closing vent or valve.
• Forced cooling of a pressure canner.
• Jars packed too tightly.
• Removed jars from water bath canner too quickly.
  • After removing cover, let jars sit 5 minutes in canner before removing to reduce boil overs and ensure a tight seal.
• Removed jar from pressure canner too quickly.
  • After pressure returns to 0 and weight is removed, let jars sit in canner for 10 minutes before removing.
• The canner stood too long after pressure returned to zero.
• Starchy foods absorb some liquid.
• Water not 1 inch over jar lids during processing.

Possible causes

• Insufficient processing time.
• Processing temperature too low.
  • Water not at a full boil at beginning of processing or drops below full boil during processing.
• Water not 1 inch over jar lids during processing.
• Packing foods raw that should be precooked (pears).
• Liquid loss during processing, causing fruit at the top to be out of the liquid.

Possible causes

• Using overripe fruit.
• Packing fruit too loosely.
• Syrup too heavy.
• Processing too long - destroys pectin.
• Processing at too high a temperature (pressure canner).
• Raw packing - food contains a lot of air.
• Smashing or pureeing food prior to heating it activates enzymes which break down pectin in the juice so the food pieces are lighter and rise to the top.
  • Heat or crush while heating any food to be pureed or food to be packed in its own juice to help prevent separation.
• Enzyme changes during handling causes separation of juice, especially tomato.
  • Heat tomatoes quickly to simmering temperatures.

Possible causes

• Starch in vegetables like peas and dry beans.
• Minerals in water. Use soft water.
• Fillers in table salt. Use canning salt.
• Yellow sediment in green vegetables or onions (natural occurrence).
• White crystals in spinach (natural occurrence).
• Overripe fruit.
• Spoilage. Process using recommended method and recommended time.

Possible causes

• Overcooking or heating at a higher temperature in hot-packed products. Excessive heat changes all natural food pigments.

• Very dry, hot weather often causes fruit to turn pink (natural occurrence).

• Cauliflower with a purplish tinge is commonly grown. Purple cauliflower is safe to eat.

  • Purpling can develop in white varieties of cauliflower if the heads are exposed to light while developing.

  • Heat may induce a color change from purple to gray or slate blue, especially if the water is hard or had an alkaline pH.

  • If you prefer to have cooked cauliflower, add a little vinegar or cream of tartar (tartaric acid) to the water.

• Red pigments in beets fade if the beets are overcooked before canning or over-processed during canning.

• You can eat the food if the liquid is clear, the odor is natural, and if you used the recommended processing methods, time and temperature.

• Garlic has an iridescent greenish or purplish coloring, this is the result of using immature garlic - it was not completely dry.

Possible causes

• Overcooking the fruit when extracting the juice.
• Using incorrect proportions of sugar and juice.
• Undercooking.
• Using overripe fruit.
• Doubling the recipe.

You can re-cook the mixture or enjoy the soft jelly on ice cream, angel food cake or pancakes.

To remake with powdered pectin:

For each quart of jelly:

1. In a saucepan, mix 1/4 cup sugar, 1/2 cup water, 2 tablespoons bottled lemon juice and 4 teaspoons powdered pectin.
2. Bring to a boil while stirring.
3. Add jelly and bring to a rolling boil over high heat, stirring constantly.
4. Boil hard 1/2 minute.
5. Remove from heat and quickly skim foam off jelly.
6. Fill sterile jars leaving a 1/4 inch headspace.
7. Adjust new lids and process half-pints and pints in a boiling water bath canner for 10 minutes.

To remake with liquid pectin:

For each quart of jelly:

1. Measure 3/4 cup sugar, 2 tablespoons bottled lemon juice and 2 tablespoons liquid pectin.
2. In a saucepan, bring jelly only to boil over high heat while stirring.
3. Remove from heat and quickly add the sugar, lemon juice and pectin.
4. Bring to a full rolling boil, stirring constantly.
5. Boil hard for 1 minute.
6. Remove from heat and quickly skim off foam.
7. Fill sterile jars leaving 1/4 inch headspace.
8. Adjust lids and process half-pints and pints in a boiling water bath canner for 10 minutes.

To remake without added pectin:

For each quart of jelly:

1. In a saucepan, add 2 tablespoons bottled lemon juice to the jelly.
2. Heat to boiling and boil for 3 to 4 minutes.
3. To test for doneness, pour a small amount of boiling jam on a cold plate.
4. Put this in a freezer for a few minutes. If the mixture gels, it is ready to fill.
5. Remove from heat and quickly skim off foam.
6. Fill sterile jars leaving 1/4 inch headspace.
7. Adjust lids and process half-pints and pints in a water bath canner for 10 minutes.

When making jams and jellies, always follow directions on recipes and packages.