Mangoes with ‘brown fibers’ … Is this OK?

Answer

The brown spots could be a result of sugars changing as the mango ripens or a result of being stored at the wrong temperature (usually too cool). If there are just a few spots then it’s safe to remove them with a paring knife and eat the fruit. If the spots go all through the fleshy part of the mango, the taste may be unpleasant and therefore undesirable, even though it might still be safe to eat. I would take it back to the supermarket for a refund. Unless your grocer knows of these problems, they can’t identify the best fruit suppliers or problems in their own storage/handling