Unripe tomatoes are more acidic than ripened fruit and can be canned safely with any of the following recommendations. To ensure safe acidity levels in whole, crushed, or juiced tomatoes use the following recommendations. If desired, add up to 1 Tablespoon of sugar per quart to offset acidic taste. Vinegar may cause undesirable flavor changes. The use of salt is optional in all canned tomato products.
Salt is used in canning only for flavor or color protection.
Processing Even though both boiling water bath and pressure processing times are given, pressure processing will result in higher quality and more nutritious canned tomato products. Wash tomatoes and dip in boiling water for 30 to 60 seconds or until skins split, then dip in cold water. Slip off skins and remove cores. Trim off any bruised or discolored portions and quarter. Heat one-sixth of the quarters quickly in a large pot, crushing them with a wooden mallet or spoon as they are added to the pot.