That is the first question to ask because not all food is suitable for canning, and some types of food need handling with special care.
While it seems like everything can be canned and put away, there are some food items that are less safe to can. Many foods are great for canning, either partially cooked or raw, in order to properly store the food. Food between 2.0 and 6.9 pH levels are usually OK to can at home. Anything over 6.9, like black olives, becomes difficult to can because they have to be specially cured before the storage process begins.
Food that can't
Besides the pH issues there are some other foods that make canning difficult. For instance, how gooey foods are plays into the canning process. Foods such as pumpkin and squash purees are not the best things to can. These thick liquids make it difficult to heat through, creating cold spots in the middle, which allow bacteria to grow and become prevalent in your canning process.
Other items, which shouldn't be canned, for much the same reason, are refried beans, butter and leafy greens, like spinach and chard also make it difficult to can due to the cold spots in the middle of the food. Creams and soups also have a difficulty with canning because, you guessed it, and they become scorched and curdled on the outside while trying to raise the temperature in the middle.
Food that can
On the flip side, if you have pumpkin and squash that you would like to can, putting them in a jar in raw chunk form will allow them the proper canning temperature in a pressure canner. It also begins to moisten them up for later use. Other than that, just about everything falls into the category of able to be canned. Foods such as lemons, plums, figs, apples and some tomatoes can be home canned with ease.
Here is a brief list of foods and their respective pH levels, which are good for canning:
- pH 2.0-3.0 - Lemons, limes, gooseberries and under-ripe plums
- pH 3.0-3.5 - Ripe plums, under-ripe apples, ripe oranges and grapefruit, strawberries, rhubarb, blackberries, cherries, raspberries, blueberries, very under-ripe peaches and apricots
- pH 3.5-4.0 - Ripe apples, oranges, grapefruit, overripe blackberries, cherries, raspberries, and peaches, ripe apricots, under-ripe pears, pineapple, sauerkraut and other pickled items
- pH 4.0-4.6 (BORDERLINE) - Tomatoes and figs Above 4.6 or so, must be pressure canned.
- 4.6-5.0 - Some tomatoes, depending on the variety (Green tomatoes are below 4.6). Pimentos, pumpkin. The USDA suggests that pumpkin butter cannot be canned safely.
- 5.0-6.0 - Carrots, beets, squash, beans, spinach, cabbage, turnips, peppers, sweet potatoes, asparagus, mushrooms, white potatoes
- 6.0-7.0 - Peas, tuna, lima beans, corn, meats, cow's milk, salmon, oysters, shrimp.
Please make note of the borderline items, which must be pressure canned. Remember the pumpkin butter, along with many other purees and thick substances, which the USDA does not consider safe for canning. The USDA site is always a fail-safe place to check when determining which foods can be properly canned and which ones are not recommended. Go gather up everything you can think of and start preserving for your own household stash.