San Jamar Lettuce Knife Plastic Knife with Serrated Edge for Kitchens and Restaurants, Nylon, 0.5 X 4.25 X 15.5 Inches, Green

They do make special plastic knives for cutting lettuce. It’s the metal in the knife that starts the browning along the edges of a cut piece. https://a.co/d/0iKxRcwY