Oyster mushroom (Pleurotus ostreatus) leftovers were used to replace some of the fat in pork burgers, boosting fiber by as much as 110% while adding more minerals and antioxidants. The mushroom-enhanced burgers also stayed fresher longer, with less fat oxidation and slower microbial growth during 7 days of refrigeration. Instead of becoming waste, mushroom stems and growing material helped turn an everyday burger into a more nutritious food.