Enzymes:

What they are; Examples; Animal-based enzymes; Dried out like wood (יבש כעץ); Inedible and se'or; The teshuvos; Davar Hama'amid. See seforim by Rabbi Cohen at ⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠⁠www.kashrushalacha.com⁠