Saving Tomato Seeds
Each tomato has between a couple of dozen seeds to a couple hundred seeds.Tomato seeds are mature when the tomato is ripe, unlike like cucumbers that need to be over ripe well after the fruit has passed the edible stage. A tomato is considered ripe when the green stem at the top of the fruit is 1/4 to 1/2 brown.
Tomato seeds need to go through a fermentation process, because the seeds have a gelatinous coating around them. The coating needs to be removed before they can germinate the following season. Fermentation can also help in reducing or eliminating viruses.
To start this process, cut the tomatoes in half horizontally. This exposes more seed than if you cut the tomato from the stem end to the bottom of the fruit. Use a pointed knife to flick out any exposed seeds. Drop the seeds into a glass or plastic container.Then to extract any remaining seeds, squeeze the tomato so that some pulp and seeds fall into the container. If the seeds are not floating in liquid from the tomato, add a small amount of water. Adding too much water, slows down the fermentation process.
Cover the container with a paper towel or cheesecloth to keep fruit flies and insects out. Keep the container of tomato seeds and pulp at room temperature or in a warm place like on top of the refrigerator. As a general rule, allow 3-4 days for the fermentation to take place. Warmer temperatures speed up the process and cooler temperatures slow it down. Cherry tomatoes don't ferment as much because there isn't as much pulp.The mixture will begin to smell as mold develops over the top of the tomato mixture.
Once a mold has developed and covered the surface, the gelatinous material around the seed will start to break down and separate from the seed. When this occurs, the seeds are ready to be washed. Add some water to the container. Viable seeds will settle on the bottom.
Slowly pour off the water, pulp and juices. Add more water and repeat the process of pouring off the juices until you have almost nothing left except seed. Place the seeds into a strainer and run water through until the seeds are clean. Rub the seeds as you do this to make sure all the coatings have washed off. Wipe the bottom of the strainer with a dry cloth to remove as much moisture as possible.
After the seeds have been washed, place the remaining seeds on a plate to dry. Don't use a paper plate or paper towel because the seeds will stick. It is also not recommended that you use a cookie sheet because it can get too hot. Put a label on the plate. Separate the seeds with your fingers or a knife and then repeat after about an hour. This prevents the seeds from clumping together. Do not put seeds in an oven to dry as they will die in temperatures over 110 degrees. After 3-5 days, depending on your ambient humidity, the seeds will be dry enough for storage.
Store seeds in paper envelopes with the name of the tomatoes and that date they were saved. The envelopes can be placed in a glass jar that has a tight fitting lid or sealed with a rubber gasket. Desiccant can be added to the jar to monitor moisture. The jars should be kept in a cool, dry and dark location - the opposite of what the seeds need to germinate. Stored properly, the seeds should last between 8 and 12 years.