The damage is sunscald which, more than likely, occurred during one of the recent warmer than usual days. When the berries are still on the plant, it can be seen that the damaged berries are on the sunny side of the plants, also that the white portions are on the exposed side of the berries. The damage can be rather significant if the plants are short on water and/or have sparse leaf coverage.
Individual raspberries are composed of numerous small juice-filled cells called druplets. When the heat hits, or an excessively sunny day arrives, some of those druplets turn white. The colorless drupelets don’t affect the quality of the fruit which are still edible.
See “Understanding White Druplet in Caneberries” http://cesantacruz.ucanr.edu/files/99628.pdf