Thank you for the query.
Its very hard to tell not seeing it. However its not any food parts or remaining fat fro years. You need to know that the main large intestine function is water absorption. Other food parts are absorbed in small intestine
. So the final stool does not contain any fat (if pancreas
works fine) or other food parts. There is also no place where this parts can remain for years.
So maybe this white clumps are parasites or pus (due to intestine inflammation).
I suggest you to have stool test
Hope this will help.