Most people know that a lot of fruit we eat is covered with an edible, protective coating. Research into food coatings that protect food and reduce packaging has been underway for several years. One "system of packaging" currently being researched in Spain uses milk serum (protein), mesquite gum and starch. The milk serum, or WPI (whey protein isolate) appears to be the most effective food coating—although its use is still in its infancy. The study goes on to suggest that while edible coatings is the "packaging of the future" it is still cost-prohibitive, and will remain so for some time. But its ability to eliminate multi-layers of packaging make edible coatings a viable alternative down the packaging road.
Source: Bio-medicine.org