There is a gel sac around each tomato seed which contains growth inhibitors. Fermenting removes this gel sac.
Years ago, I was taught by an old Italian woman who spoke no English how to save tomato seeds. She used few words, just did a step by step process, showing me how to clean the tomato seeds. She showed me how to shake the jar of seeds and water each day as the fermentation was happening. I had no clue why this was all so necessary, but I was not gonna argue with her.
