Yes, you can! During shipping, the mycelium is exposed to warmer temperatures and therefore starts its growth. The white is the mycelium that is doing its job. When the shipping takes longer, the mycelium will grow, and thus more white parts will be in the bag of substrate. The process even speeds up when it’s warmer outside. But in the plastic bag, the material will stay moist, and alive.
Make sure to properly break down the substrate in small chunks to avoid air cavities when filling your mould. This will make the white colour disappear, but the mycelium will still be there! Do you want to know if it is moist enough? Make a small ball in your hand, and if it doesn’t fall apart the moist level is good. If not, add a little water.