I LOVE canning! I haven't read what others have posted because I only have a few minutes, so if there is duplicate info, I apologize. I just couldn't resist replying!
Note: I live in the US
Before I jump into this, I would recommend buying the Ball Blue Book Guide to Preserving. The intro has the answers to a lot of your questions.1. What kind of jars can you use? I suppose I can't re-use jars from the supermarket?I use Kerr/Ball jars (same company, same style jar, different name). Kerr is simply the name Ball puts on jars that they distribute out west. I don't remember why...
These jars are made to withstand high temperatures necessary for canning. There are two main reasons I can think of not to re-use jars from the market:
1. You don't know if the jars are made to withstand high temperatures, i.e. they could explode while processing (this refers to the actual step of canning).
2. You would need to find lids that fit the jar. This directly leads to your next two questions:
i. What is with the two-part lids that I keep seeing?The two part lids consist of a lid and the ring to hold the lid on the jar. You don't have to use a two part lid, they do make "all-in-one" lids, they are just not as easy to find. These also may be more finicky about sealing, I haven't used them before.
ii. Why can't you re-use lids if you wash them properly?You can and you can't. You CAN reuse the ring portion of the lid. You CANNOT reuse the lid. This is because the lid has a sealing agent that helps it seal to the jar post processing. These seals are one and done use. They may seal a second time but you can't be confident it is a good seal, it may lose it's seal over time causing the food in the jar to become exposed to outside pathogens.
iii. How much is reasonable (UK) to pay per jar?N/A
iv. Is there a maximum size that's safe to use?The size jar you use is dictated by the food you are canning.
2. What can you can and what can't you can?i. How do I know if a food is high-acid and low-acid?My general rule of thumb:
Fruits and tomatoes are high acid. Though tomatoes aren't really that high acid, which you may find surprising...
Everything else is low acid.
When I can tomato sauce (water bath can) I add lemon juice to punch up the acidity a bit. Also interesting to note: I use lemon juice from a bottle (Ick, I know...) because the acidity has actually been breed out of lemons, so you can't rely on fresh lemons consistently. I have actually debated buying my own pH meter, but now we are starting to get off topic.
Acidity is also dictated by the recipe you use. When you are starting out and learning PLEASE ALWAYS FOLLOW A RECIPE FROM A REPUTABLE SOURCE. I can't stress how important this is. A mommy blogger and/or pinterest is most likely NOT a reputable source. The internet is a scary place for safe canning practices.
ii. Which foods lose texture during canning? (I hate sloppy textures!)It depends on the recipe and canning time.
3. Can you water bath can in a normal saucepan? (They seem like elaborate saucepans to me, and I already have one HUGE pan for making jam which could fit a good few jars)I'm not sure what you are specifically calling a sauce pan, but if you have a pot that you can fit the jars in, cover them completely with water + 2 more inches of water and it has a lid, then yes! That is all you need for water bath canning.
Pressure canning is a different beast though, that requires a pressure CANNER (not COOKER). Although a pressure canner can double as a pressure cooker. It's one of those a "square is a rectangle but a rectangle isn't a square" situations...
4. Can you can prepared food? Like, can you make soup and can it? Or pesto? My husband isn't crazy about the idea of canned vegetables but we eat a lot of soup.Yes, but for the most part this will require pressure canning, not water bath canning. Soups, definitely, but NOT pureed soups. Those are too dense for the heat of processing to get to the center of to kill the bacteria. I'm not sure about pesto.
These are the foods I prepare most often and the processing they require:
Water bath canning prepared foods:- Jams, jellys, preserves
- Plain tomato sauces
- many different types of salsa
Pressure canning prepared foods:- stock/broth
- broth based soups
5. How can you tell, when you open the jar, if your food has gone off?Smell and look.
If it smells off, it is. If you look at the underside of the lid and there is mold, there is an issue. Sometimes you can't tell and you have to trust in your best practices. Botulism is scary.
6. I know this sounds silly, but when you open the jar, is it just like buying a tin of fruit/vegetables from the supermarket?If you find the right recipe!
7. What's the difference between canning vegetables and pickling them?There isn't. Everything you do is called canning. Pickling is a specific instance of canning that uses vinegar as the acid to keep away bacteria.
Some of my favorite canning blogs:
* Some of these aren't very active anymore, but the recipes are still useful
http://foodinjars.com/http://www.allfourburners.com/http://wellpreserved.ca/http://hitchhikingtoheaven.com/http://hungrytigress.com/http://www.canningacrossamerica.com/http://www.savingtheseason.com/http://puttingupwiththeturnbulls.com/I could go on for hours... I'll stop now ;)