What Causes Brown Stool With White Inside?

hi, i was wondering what the implications of having stool that was brown on the outside, but partially white on the inside. i know this because it had broken into pieces in the toilet, but it was a small part. perhaps it was undigested food that was white to begin with. it was smaller than 1 centimeter. i understand clay or white stool is indication of gallstones or liver problems, but white on this inside like that didnt seem to fit any symptons i have researched