I know that we are supposed to fast one hour before we receive Holy Communion. I have come across kind of a stupid issue with this sometimes, though... this sounds ridiculous, but sometimes I will be aware of the fast and not eat, etc. but then maybe like 10 minutes or so before Mass, I realize that there is like a little piece of food in the back of my mouth from earlier or something like that. What am I supposed to do in this situation? Does that break my fast and therefore, I can't receive communion? If it's something that I really and truly don't realize until later but I had every intention to fast, and it was like an accident... then am I not allowed to receive?
Also, would it be a mortal sin, if so? Thanks!