After rinsing the tomatoes, soak them in pickling lime for at least 2 hours. You can soak them overnight in the fridge. However, this step isn’t absolutely necessary if you don’t mind a softer texture in your pickled foods. Pickling lime is a white powder that introduces calcium to the pectin of the food to add crispness. Because it is alkaline, you must make sure to wash it all off before introducing the food to the vinegar, otherwise you may end up with a less acidic pickling solution, which could allow bacteria to grow. For this reason, make sure to rinse the tomatoes in three rinses of water and soak them again in a clean ice bath for at least 3 hours. Once this is done, you can prepare the jars for canning and the pickling solution. If you will not be canning the pickles (heat sealing the jars) they will last up to 3 months in the fridge. Canned pickles will last up to 1 year.
Source: Garden Connect and Share