Mozzarella color on pizza
I want to know how to reproduce the white color of melted mozzarella one finds on certain restaurant pizzas. I use fresh mozzarella, bought in water, but it always turns at least slightly yellowish after it cooks. I'm not sure if this happens due to the kind of mozzarella, or the oven temperature and cooking time. Or perhaps from brushing too much olive oil on the dough before it goes in the oven? More than color, I think it's also a matter of texture.
I cook my pizzas on a preheated stone at 500 degrees, heated from the lower oven element, for about 4 minutes, and then under the broiler element for one or two (by this point the cheese has already lost its color though).
Are you grating the fresh mozzarella? slicing? I would suggest try cubing to about 1/2" and keep them cold until use. Maybe that'll help allow them to spread and stay gooey without the unwanted browning? Is it browning we're talking about here? I thought a little browning was good, but...yellow? hmmmm
Your mozzarella slices will turn yellow as soon as any of the fat renders out of them. The fat comes out when you have too much exposure to heat. Oftentimes you'll find that pizzerias will cook their pies and then only allow the residual heat of the pie to melt the mozzarella slices in place. That is what keeps them so white and milky in texture. The mozarella slices are put on the pie immediately AFTER the pie comes out of the oven. (Do the same for basil ... allow the basil to wilt in place and stay green ... if you cook it, it turns black.).
Are you using fresh buffalo mozzarella?
If, when you say "More than color, I think it's also a matter of texture", you mean your mozzarella is tough and stringy, then it's overcooked.
Also, I'm assuming that you bake it for 4 minutes, then move the pizza to the top rack, turn off the bake function, and turn on the broiler. If this is the case, the mozzarella (and other toppings as well as the entire pizza as a whole) is being overcooked and exposed to heat for longer than it needs to be. This is because it will take a couple of minutes at best for your broiler to heat up. Yet, the entire time this is happening, the pizza is still cooking from the residual heat from the baking portion as well as the increasing heat of the broiler as it heats up.
If you're heating your oven and baking stone for 30 minutes on as high of heat as your oven will go, there is no need to broil the top.
Try moving the rack to the top of the oven and cooking your pizza there. The top should cook and be done at about the same time your crust is sufficiently browned/charred (depending on the style of pizza you're cooking).
What style of pizza are you cooking?