Clostridium botulinum bacteria
May as well start with the big one, botulism. It is caused by the bacteria above and thrives in a moist, anaerobic(no oxygen), low acid environment. Improperly canned foods can be perfect. The reason for concern is that there is no odour or obvious sign of spoilage with this particular little bug.
The good news, most fruit is acidic, vinegar is acidic so if those are the what you are using to can, jams, jellies, pickles, you are safe, carry on. One of the tricky ones is tomatoes. They straddle the safe pH level and you'll notice recipes for boiling water canning contain vinegar or lemon juice to boost the acidity to make them safe. Don't omit or reduce either.
To neutralise the bacteria, you need a temperature of 240 degrees for at least three minutes. You can only do that in a pressure canner. Your low acid food, vegetables, meats, dairy products and fish, all need to be processed in a pressure canner for the recommend times and pressures. Don't wing it, ever. Why take the risk?
The next big three, E. Coli, Salmonella and Listeria are also heat sensitive but at a lower temperature and a boiling water bath is sufficient. Again, make sure you process for the recommended amount of time.
All of the above are quite common and are present in our environments, the same goes for the variety of molds and fungi that can spoil your efforts. That is why it is important to keep your work spaces and utensils clean. You can contaminate your sterilized jars and lids if you aren't careful. Make sure all fruit and vegetables are properly washed, don't use the same knives or cutting boards if you are handling higher risk food like meat or poultry (or at all, really) and always wash your hands after handling food. It only makes sense.
If you don't get a proper seal, refrigerate and eat right away. If the lids bulge or buckle after storage, discard. Properly sealed, the lids should be hard to remove not just come off by themselves. Same thing for discoloured, moldy or food with a funny smell ( I was going to say unpleasant, but I have canned goods that don't smell great but that is what they smell like).
Use proper jars and lids and don't re use the lids, you can't guarantee a proper seal otherwise.
Use proper techniques. Boiling water or pressure canning is the only safe way to can at home. Open kettle, steam or the dishwasher are not safe. Yes, maybe 99.9 percent of the time nothing bad will happen but really, why?
Do consult with you local province, state or federal food safety agency. Most have very comprehensive lists on how to can just about everything safely. Here is the link to just one. I couldn't find the Canadian one, I've seen it so I know it exists, but where???
Canning at home has changed a lot over the years. Many things your mother, grandmother or anyone else for that matter did, may not be recommended today. I have had lots of heated discussions on the subject of food safety and canning at home. Check and make sure, be smart and be safe.
If you notice a mistake by all means let me know and I'll correct it. Same thing if I left something out. Next up is the Canning 101 post, all about the equipment you need to start making your own home made preserves. Thanks for stopping by.