Hi,
Blackening around the edges is fine, but putting straight into a ziploc is not. The seeds need to be completely dry before putting into plastic. The seeds should be spread out on a paper plate or paper towels to dry for a week or so. Then I like to put them into paper envelopes. After I've saved them for like a month or more, I sometimes switch them to plastic baggies or film containers because I know it is completely safe to do so at that point.
Also peppers need to be fully ripe so the seed is mature and viable. When peppers are green, they are edible, but not fully mature. They need to change color which varies depending on the variety.
Remy