Anyone that has ever eaten a tomato should know where the seeds are. Each fruit contains dozens, maybe even hundreds, of seeds depending on the variety and size. Choose a ripe tomato that you are going to use to cook or that has past its prime and you’d rather not eat from which to harvest seeds. Squeeze the pulp from the tomato into a glass or plastic container; either use the rest of the fruit or add it to your compost pile. This next part really had my husband in a knot – fermenting the seeds.
In the jar with the seeds and pulp add as much water as their is juice and set the jar in a warm place out of direct light. After three days the viable seeds will sink to the bottom and the rest with the majority of the pulp will float to the top with a layer of stinky mold. Scoop out the mold and adjacent seeds with a spoon and discard (add them to your compost). At this point I used my sieve or small kitchen strainer to pour out the rest of the liquid, drain and rinse the seeds.
Apparently in this process it’s easy to keep the viable seeds. From experience it makes it easy to remove the pulp. Once your seeds are well rinsed spread them over a paper towel and set them in a warm, dry place. On top of the refrigerator is a good place. After they have dried – usually within a few days to a few weeks (I’d give them at least a week), put the seeds in paper or plastic envelopes (paper retain less moisture and keep the possibility of mold to a minimum).