

Yogurt with raw milk, white area on top
Hello, i made raw milk yogurt 5 days ago and found out on at least one of them today some white on the surface of the fat pelicule. Is it safe ?
Maybe it is a contamination in my fridge from cheese ?
Or is it because i didn't use a retail starter ?
Thanks
My process : start with clean pot (no sterilization) and lid. Heat the milk for 20mn between 80 and 90°c. Cool down the container in cold water until it is less than 40°c. Mix it with my previous yogurt (same process). Put it for 8H in my seb multidelice yogurt machin. And finally directly in the fridge.