Answer: There's no need to ferment the seeds. Eggplants ready for seed saving will be dull, off-colored and hard. Cut the ripe eggplants in half and pull the flesh away from the seeded areas. If you want to save more than a few seeds, a food processor comes in handy to mash the flesh and expose the seeds.
By the way, eggplant flowers can be cross-pollinated by insects, so different varieties of these would have had to be separated by 500-feet this season for seed purity.
Q&A Library Searching Tips