He explains, "Look for frozen pizzas with fewer additives - avoid dough conditioners in the crust and anti-caking agents like cellulose in the cheese." Anti-caking agents are additives used to prevent shredded cheese from clumping or sticking together. Sometimes, the agents are cellulose (or wood pulp) and other times, it's cornstarch. Anti-caking agents can interfere with how the cheese melts and browns, which is something pizza purists like Gemignani prefer to avoid.