it will pulverize and liquify the seeds-probably imparting a bad color and taste. Do it the old way. I personally like jam, but not too many seeds, so I do half with the seeds and add juice to it--some seeds, but not many in proportion. I did a version of Alton Browns tomato sauce--basically roasted seeded, but not peeled tomatoes in the oven for 2.5 hours, no salt, then vitamixed the cooked tomatoes, some small amount of seeds were left, and peels--perfectly smooth!!! Then I heated it enough to can and added salt at that time. No more spitting on the stove and scorching and it's a whole food!