I have a piece of comte (French hard cheese) open for some time (1 week or so). How do I recognize that it's moldy and therefore not good to eat? There're a thin non-connected layer flour on the piece of the cheese which makes it quite difficult to visually detect mold.
This is what the cheese should look like.
Edges on a cheese like this are referred to as the rind. Any white on there is fine unless it starts looking fluffy, even then you could probably just cut it off. The rind here and on many hard cheeses is a quite hard layer of dried cheese and protects the cheese inside.
If the yellow section of the cheese had mold on it that would indicate the cheese had become moldy after being cut or if there was a blue or green mold growing anywhere on this type of cheese. This would normally indicate the cheese had been kept badly. If your fridge is clean and dry wrapped hard cheese should keep a couple of months.
to see if a hard cheese like comte is rotting, you can usually smell it but i assume you may not be used to the original taste. If it is really not good for eating, some moss will start to developp on, this will happen when it is kept in a humid place; if you are keeping the cheese in a dry place it will just become hard as hell and if it start to get cracks on the surface, the taste can be not so good.