I had a Chocolate lab. You can use bitter apple spray, but my suggestion would be to crate train the dog, and leave him in the crate when you are out. When you are around, if you see him chewing, scold him sternly and consistently. Chocolate labs are very smart dogs and he will be trained in a few weeks.
Rocky used to be able to open the front door of our house and close it after himself. I was also training him to open the fridge and bring me a beer, but once he learned to open the fridge, my reward wasn't enough to compensate for whatever was on the bottom shelf. Then we had to train him not to open the fridge.
