White drupelets like those are usually caused by UV sunlight. Although any berry in the patch may be affected, the damage is prevalent on south and west-facing berries. Certain blackberry varieties are more prone to this.

I've seen that on some of my berries before too. If it just affects a couple of drupelets on the berry I go ahead and eat it. If if affects a lot of drupelets, I discard the berry.

Numerous white drupelets create an off flavor; these eventually shrivel and dry out, creating a crunchy berry with no off-flavor.

At least two of the berries pictured above would be discards.