lake Rat feeding time aggression?

My 2 female rats get along fine until their food bowl is filled. They have been housed together for the past year and a half and I recently completely cleaned their cage very well. After cleaning, I noticed that one rat hordes all the food when I put it in the bowl and then doesn't want to share with her sister. When the sister approaches where the food is stored, she is quickly pinned and forced away very aggressively. I'm thinking she is protective of the food because I washed away the familiar scents of the cage. Is there any way to get her to share and be less aggressive or will I just have to wait until there are familiar scents around the cage again?there