No rennet, no cheese. Rennet contains the digestive enzyme rennin, used to curdle milk in the cheesemaking process, separating it into solids (curd) and liquid (whey). Rennet is typically extracted from the fourth stomach of a calf, also known as the abomasum, though the rennet of other young animals are sometimes used. The enzyme is present in all mammalian stomachs — that includes humans — as it is essential for digesting mother’s milk.

Vegetarian? Look for organic cheeses that are labeled rennet-free. In modern times, rennet-sourcing has branched out to non-animal options. Ah, technology. 

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