This week the food detectives want to know if New York City really has the best pizza. And if so, is the secret in the water? We'll also find out what metals like iron and copper are doing in our food, and discover the good, the bad and the ugly truth about preservatives. Also, Ted Allen wants to know if tapping the top of a soda can to prevent it from exploding really works. Find out this week, on Food Detectives.