I have noticed lately, in my flour, teeny tiny bits of black. We think it's a flaking off of the machinery used to mill the flour..it is not a bug.
I have noticed it when kneading for quite awhile and couldn't figure out the source. A few weeks ago I sifted through my bag of robin hood whole wheat flour and deduced that's where it's coming from. I've contacted them and sent a small sample to see if they can tell me what it is. I decided to buy my whole wheat at my local bulk barn and was surprised to see, if I look very closely, the small black bits in the spelt and the rye flours....possibly others, but I didn't want to attract attention :)
I'm sure it's not harmful but I've googled and can see no other reference. I saw the black bits and pointed it out to my husband so I know I'm not crazy..in the bulk barn we were both looking in the bins and pointing out the bits...so I wonder....has anyone else noticed it? It's not in the whites..only in the 'whole grain' types...
It is most likely part of the bran as the bran is removed from white flour.