[ZBQ, I'm editing Feldon's response because he covered the process very thoroughly and accurately, and I just want to add a couple of details that only represent my opinion ...]
1) Start with fully ripened tomatoes, not overly ripe. Preferably save seed from 2 or more tomatoes.
Sometimes, I keep the seeds from a particular tomato separate because it came from a plant that showed superior qualities. But I always also keep a mix of seeds from more than one tomato off the same plant, if I only have one plant, or a mix of seeds from tomatoes off of more than one plant of the same variety just to preserve potential genetics.
I may be off base on this, but sometimes I think selection is preferred. So, I also never save seeds from tomato fruits that have any deformity. I know some folks say BER doesn't affect the seed ... maybe not. But I think catfacing, zippers, and double or multiple fused blossoms producing deformed fruit is all genetic and I never save seeds from those types of deformities.
2) Collect the seeds and some of the surrounding "goop" and put it in a container. If you have an overabundance of tomatoes, you can just cut a tomato in half and squeeze the contents into a cup. I cut the tomato into slices and then carefully spoon the seeds and goop into a cup, leaving intact slices that I can then use on a sandwich. Putting the seeds into clear plastic containers are preferable so you can see the fermentation process.
I do just as Feldon has described depending on whether I want to use the deseeded fruit for fresh eating, or just simply cut the fruit in half, squeeze out the seeds and use the resulting discarded fruit for cooking ... which is seldom in my case.
However ... a cautionary note here ... when you scoop out the seeds with a spoon you should ALWAYS check your spoon before moving on to another variety. In fact, inbetween extracting seeds from a group of tomato varieties, I always thoroughly rinse everything ... cutting board, knife, spoon, whatever, and wipe everything down with a sponge, clean the sponge of seeds (don't take the seeds off the sponge ... they may be mixed from previous clean-ups), and check under my fingernails, etc.
3) Optionally, 1 tbsp or so of water and swish it around.
You frequently will have to add water especially for paste varieties and other dense fleshed tomatoes. Sometimes, too much water will slow the fermentation. And chlorinated water takes a little more time to start fermenting ... so you may want to use bottled water.
5) Clearly label the container with the variety name and perhaps the source of your seeds from the previous year.
I always use 8 - 12 ounce plastic cups and ALWAYS label the cup BEFORE you squeeze or otherwise put the seed pulp into the cup ... ALWAYS. Don't wait ... you may get interupted and forget what you were working on. For markin' the cups I use wide masking tape and a ball point or Sharpie pen. I guess you could write right on the cup with a Sharpie, but I reuse some of the cups sometimes (after THOROUGHLY washing them to remove any stuck on seeds) and the masking tape can be put right over the previous label.
Something else I do is to take a fork and mash up the pulp that holds the seeds ... you know ... sometimes the tomato has that white hard membrane inside the seed cells ... and later, if the fermentation is not quite far along enough, but you have already started washing the seeds as in the next set of instructions, you'll find that a good amount of seed may still be clinging to the partially fermented pulp and will float out with the waste.
So, if you mash that stuff up with a fork against the sides of the cup, it will ferment quicker and more thoroughly and you won't lose any seeds in the rinse (except the bad ones that float out and you want them to float out with the waste). WASH THE FORK before using it on the next variety.
9) Uncover the container and add water. Wait a few moments for the viable seeds to sink to the bottom.
Okay, here is where I differ with Feldon. I used to do it the way he describes ... in the cup. But I found that if you dump the contents of the cup into a large deep mixing bowl and run a bunch of water into the bowl to almost fill it to the brim, the seeds will swirl around in a whirlpool and settle to the bottom of the mixing bowl and the pulp with float out a lot easier without losing any seed.
Maybe I'm fermenting more seed at once, but this works really well for me. The first bowl full of water is very murky and stinky and you should let it settle for a minute so the seeds get together in the bottom. Then tip out the water slowly 'til you can see the seeds in the bottom. Don't decant all the water the first time.
Refill the bowl by running the water kinda down the side of the bowl ... oh, by the way ... I'm doing this in the kitchen sink and into the garbage disposal ... anyway, run the water into the bowl so it makes a whirlpool and spins the seeds around so they settle to the bottom in a cluster. Decant the waste again. Keep doing this until the seeds look nice and clean. Gently tip the last of the water out slowly slowly until the seeds rest in a clump on the side of the bowl. Then rake them onto your paper plate.
12) Dump seeds out into a strainer and rinse thoroughly.
I skip this step because I usually don't need to rinse the seeds any further and because seeds tend to cling to the strainer and can possible result in a stray seed from one variety getting mixed into a subsequent batch from another variety. Besides, you have to "knock" the seeds outta the strainer and onto a plate and that's just another step that can cause stray seeds to fly about.
14) Put the seeds on a plate or similar (I use paper plates) to dry. The drying process can take up to a week. Some seeds will stick together. Separate them.
Again, mark the plate BEFORE you put the seeds onto it. I think this is important because you can always get distracted by the phone, the TV, your spouse (who usually can find a million things you should be doing besides fiddlin' around with tomato seeds), etc.
If you have the marked fermentation cup up on the counter and use a rinsing bowl, you can always refer back to the cup to remind you which variety you're workin' with. I always do this step by step and throw away, or invert (if I'm recycling) the cup after I mark the paper plate with the variety name. That way if I'm interupted, I always have something to refer back to so I know which variety is where in the process.
Also, I've already edited out where Feldon says about drying, storage, etc., but here are some observations from my point of veiw ...
Pre-dry your seeds a while on the paper plates spread out in a warm place BEFORE stacking the paper plates one on top of the other to dry for a week or two ... WHY???
Because if you're doin' a bunch of seed and you stack the paper plates while the seed is still freshly rinsed and wet on the paper plate, the seeds will stick to the bottom of the plate set on top of them in the stack ... INVARIABLY.
Then later, when you take a notion to look for one particular seed type, you'll invariably restack the stack of paper plates in a different order and the seed stuck to the bottom of the plates will then be resting on a different variety than that from which it came. Trust me here.
And be very very careful when you do stack plates and undstack plates later to move the seed into storage containers.
Anyway, Feldon's information is all good ... I just wanted to add my 2 cents from recent experiences.
PV
Oh yeah ... and NEVER sniff the bottoms of the fermentation cups ... WHEW
:wink:
