It is a silicone ring that seals it. The manual states that you must keep the ring clean by removing and cleaning the ring AND lid after each time you use it or that there may be a risk it holding smells. Both the ring and lid should not be washed in the dishwasher of course!! So far, I have not noticed any stains or smells after using it while pressure cooking with really intense seasonings like rosemary, celery, and onions/garlic, and I've thoroughly cleaned the seal and appliance every time after each use as the manual states. My recommendation is going to be follow what it says in the manual and you should be okay. In terms of stains, I wouldn't rule them out from being possible to happen in the right conditions though I can't imagine it affecting anything. My thoughts on that are that the only reason you wouldn't ever see it on other kinds of seals is because the seal itself is black or another color but in terms of stains on the one i have, I've seen none so far!