Indian Meal Moths can be a big problem when you have to do so much cooking and baking from scratch. A couple of years ago we had to deal with a terrible infestation. The moths were even in the pepper grinder! Be sure to not let it get out of hand.
My first mistake was thinking that those Pantry Pest traps were of any use. Don't bother. They only catch about 1/8 of the males!!! Still plenty of sperm around for the lady moths. ugh.
Secondly, the exterminator came... three times... also worthless. The caterpillars/eggs/moths were in places that the exterminator never touched.
Thirdly, no caterpillar is going to be in the slightest bit detered by a ziplock bag. You need heavy duty plastic containers with airtight lids.
Fourthly, the darn things don't just get into the flour, they get into rice, chocolate, dried fruit and nuts, spices, baked and packaged goods like cereal and cookies etc.
The moths get into your house through the products you buy at the health food store. They don't use pesticides on the organic stuff and the health food store doesn't use usually use pesticides in the store. The caterpillars crawl through the crevices on cartons and make cocoons in the creases of the corners (like between the plastic liner and the carton of a cereal box). When the moth is formed, there's a ready source of food available and they look for mates and places to lay eggs, with more ready sources of food.
Freezing kills the eggs. Think extra protein. What we had to do was throw just about everything out, and put the rest in the freezer. All new products go either into the freezer or are put into rubbermaid containers as soon as they come into the house. My whole pantry is full of tubs and cereal dispensers and the like. I watch for the "pterodactyls" (which is what we call them) like a hawk. I keep the traps as a monitoring device. If there are a lot of moths in the trap, you can be sure that there's about fifteen more times that flying around in the house. I also watch the corner/edges of where the walls meet the ceilings. New caterpillars tend to crawl up there to make their cocoons. When the exterminator came, he would spray along the wall and ceiling.
Stay vigilant! It's a war! Good luck