Home Canning: Definitions Guide & Signs Of Spoilage

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Tomatoes & PicklesAcid Foods: Fruits, tomatoes, rhubarb and pimientos are acid foods.

Botulinus: Bacteria found in the soil have been known to cause toxin to form in carelessly canned foods. No danger when clean, sound, unblemished fresh produce is selected, prepared and processed according instructions. Low acid foods should be boil 15 minutes before tasting. The 15 minute boiling is to destroy any toxin which may be present.

Cold Pack: To fill jars with raw food.

Enzymes: Substances which bring about natural changes in raw foods.

Flat-Sour: The most common form of spoilage in vegetables. Flat-soured food may look good but it tastes, and usually smells, bad.

Fruit Jar: Glass jars used when putting up fruits, vegetables, meats, etc.

Head Space: The space left at the top of the jar when filling, or packing with food.

Low Acid (Commonly called Non-acid Foods): All vegetables, except those mentioned as acid foods; soups, meats, poultry, game and fish are low acid.

Metal Band: A screw-on band of metal used to fasten lid on jar.

Open Kettle: The way of processing fruits by cooking them in an uncovered kettle, then filling hot jars, one at a time, from the boiling kettle. Each jar must be filled and sealed quickly.

Organisms of Spoilage: Bacteria, yeasts, and moulds are low forms of plant life, known to scientists as micro-organisms. These organisms ruin any canned food in which they are allowed to grow.

Pack: Manner in which jars are filled also refers to the food in the jars.

Partly Seal: Leaving caps or lids loose enough for steam to get out of the jars while they are processing. The must be tightly sealed as soon as removed after processing is completed.

Pre-Cook: To heat food thoroughly before putting it into jars.

Processing: Cooking jars of food in hot water bath or in steam pressure canner or cooker.

Sealing: Closing jars airtight.

Spoilage: Foods are spoiled when they mould, become cheesy, sour or otherwise unfit to eat.

Steam Pressure Canner Or Cooker: A kettle fitted with steam-tight lid. Lid has safety valve, petcock, and pressure gauge.

Sterilize: To heat food, jars, caps and rubbers long enough to kill the organisms that would, if not killed, cause food to spoil.

Water Bath Canner: A deep, flat bottom kettle or can, in which water can be boiled; must have cover and also rack, platform, or basket to keep jars from touching canner.

Vacuum: Vacuum in a jar plus the natural pressure of air on the outside will hold a lid down to make and keep an airtight seal. When a jar is heated, the solids, liquids, and air in it expand and some of the air is forced out. As the jar cools, everything in it shrinks, leaving an airless space at the top. The empty space with no air in it is called vacuum.

Source: Home Canning Guide, Dominion Glass Co. Limited

Packed Peppers

Canning produce from the garden is an excellent way to preserve food and save money on groceries, but you do have to take care and watch for signs of spoilage or contamination before eating the food you preserved.

Here’s a handy list of signs to watch for:

  • Jar seals have bulging lids or the seal is broken
  • Jar is dirty on the outside (a sign of food seepage)
  • Liquid is cloudy or bubbling/fermenting or foaming
  • Liquid is seeping out from under the sealed lid
  • Contents spurt out when the jar is opened
  • Mold has grown on food or under the lid
  • Food is slimy or mushy
  • Food smells off or unusual
  • Food is discolored (usually darker).

If a jar is showing signs of spoilage, throw it out safely so that no children or animals can get at it.

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Published: July 2, 2009
Updated: June 14, 2012

What Readers Are Saying:
7 Comments to “Home Canning: Definitions Guide & Signs Of Spoilage”
  1. Terri says:

    I just canned stewed tomatoes this afternoon. This is the first time ever canning.Followed all instructions using hot water bath 3 jars fit in my kettle and recipe did not say to cover while boiling. Should I be concerned that the lids did not pop down?

    • Annie McDaniel says:

      Yes, it is important that they seal properly. If you have a few jars that the lids did not pop, I would suggest refrigerating them and use them up as quickly as you can. Always better safe than sorry.

    • Karen says:

      Terri, always cover the tops of the lids with water in the boiling water bath. Sterilize the jars, and process for the correct amount of time. If the lids did not seal down, the product is NOT sealed and can spoil. You need to do a web search for how to process tomatoes in a boiling water bath and follow the directions exactly. Better yet, purchase Ball Blue Book of canning and preserving. Walmart, Menards, Amazon, or just about any grocery store will have this book. It is not expensive and it explains all the steps. Eating improperly processed food can make you sick or kill you.

  2. NancyS says:

    Terri, if your lids did not seal properly your stewed tomatoes are NOT preserved and could harbor dangerous bacteria. Tomatoes are naturally high in acid and if you added vinegar to your recipe that increases the acidity even more so that’s good. I would open one and taste a small amount. If tastes OK, store jars in refrigerator and heat to boiling for 5 – 10 minutes before consuming. They won’t last nearly as long as jars that were processed in a hot water bath. I am no expert and hope others will weigh in here! That being said, don’t give up on canning! I started doing a little bit last year with a water bath canner and this year bought a pressure canner as well and have gone all out. It’s a lot of work, but so worth it and so much healthier! Do some research on this site and before you know it you will be a canning pro!! Good Luck!

  3. Joyce says:

    Please do NOT turn your Canned/ sealed jars over onto the lid/upside down,this
    Is an old unsafe and no longer recommended method.
    As pretty as this photo is,it is an outdated method.

  4. Angela says:

    I made a tomatillo salsa and canned it this afternoon. This was not done following a recommended recipe. I was unaware of the necessity of acid in order to preserve salsa until after completing the canning process. I place them in a hot water bath for 15 minutes and the lids have sealed. Will placing the salsa in the refrigerator immediately after cooling prevent botulism? I plan to consume these jars within 2-3 weeks. Is it still a danger? This was definitely a lesson learned the hard way, however, I hope these can be salvaged.


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