Choose tomato varieties that you want to grow the next year. These should be the plants which you love taste wise and are also resistant to the weather conditions. Choose healthy tomato plants as they will have all the useful trait in their seeds. Pluck as many tomatoes as you need according to the amount of seeds you want to store. The tomatoes can be used in the kitchen after the seeds are conserved.
Bring in the tomatoes to the kitchen. Slice them in half and use a spoon to scoop off the seeds along with the pulp from the inside cavity. Place the seed pulp in a bowl or glass. Now add a couple of tablespoon of water to the seeds. Cover the glass or bowl with a plastic wrap to make an environment for fermentation.
Poke in the middle of the plastic wrap with a pen tip or pen knife to create a small hole for air entry. This air will aid in the fermentation process.
Now place the seeds in a warm place. This could be the window side or top of the refrigerator. This fermentation process is going to take up to three days.
It is necessary to remove any seeds which look small so that plants next year are perfect healthy. Remove the plastic wrap at nights, stir the contents and replace the wrap. If the first wrap wears out, use a new one. However, do not forget to pinch the hole for the air.
After the third day when you notice the scum floating to the top, take the container to the sink. Scoop off the scum with a spoon and discard it. Now pour out the seeds into a large sieve. Rinse them well under the sink water to get rid of the pulp remains. Remove all the pulp and as much water as possible from the seeds.
Spread out the seeds on a large tray. Lay them in a single layer and place them in a safe location where they can get dry. When the seeds are totally dry, store them in airtight jars or envelopes for next year.