Hello Rabbi!
Is it safe to assume that most cheeses in the US are made with non-animal sources of rennet?
Is it permissible to use the cheeses mentioned above?
When eating at an unsupervised pizza restaurant, why is there no issue with either the pan or pizza cutter that may have been used to cook or cut a pizza with non- kosher meat toppings?
Thanks,
Jacob
Animal rennet itself is not what concerns me with ordinary cheese. I would not tell you that you need to determine whether the rennet is animal, microbial, or vegetable before eating the cheese.
We have written quite a bit on Kashrut.org about the halachot of cheese, and if you want to understand the issue properly, I would suggest reading those articles, because the subject is more complicated than simply asking what kind of rennet was used.
For ordinary inexpensive cheeses, such as the mozzarella that you would normally get in a pizza shop or a regular restaurant, I would not be concerned. The animal rennet used in the cheesemaking process is not being eaten as a meaningful food ingredient or flavor in the finished cheese.
The cheeses that deserve more attention are generally the more expensive, aged cheeses. That concern is not primarily because of animal rennet. It is because of the gezeirah of גבינת עכו״ם. In my understanding, that gezeirah relates to the traditional types of cheese that were made and aged in the manner that Chazal were discussing. In today’s market, those would generally be the more sophisticated or expensive aged cheeses.
So if you are going into an ordinary pizza shop and they are using normal commercial mozzarella, I would not worry about the cheese. If you are in an upscale restaurant serving specialty or aged cheeses, then it may be worthwhile to look into the particular cheese.
As far as the pizza pan, oven, pizza cutter, or other utensils that may also have been used with non-kosher meat toppings, the answer is essentially the same as with the vegetable omelet. We do not assume that because a utensil may have touched non-kosher food at some other time, your food now contains a meaningful taste of that food. If you order a plain cheese or vegetable pizza and it looks and tastes like what you ordered, I would not investigate the history of the pan, oven, or cutter.
If you actually see pieces of non-kosher meat on your slice, that is obviously a different situation. But you do not need to create a concern based merely on the possibility that the same equipment was previously used for another pizza.
If you want the fuller explanation of cheese and גבינת עכו״ם, take a look at the cheese articles in the Jewish Law section of Kashrut.org.