Rennet and rennet concentrates are specifically identified in subheading 350710 because of their defined role in milk coagulation for cheese production. All other enzyme preparations — including microbial proteases, amylases, and multi-enzyme blends — fall under 350790 regardless of their source organism or industrial application.

Enzymes used as food processing aids or food additives are subject to FDA oversight, and importers must be able to demonstrate GRAS status or food additive approval for the specific enzyme and its intended use. Industrial enzymes not intended for food contact generally do not require FDA clearance, but documentation of end use should accompany the shipment to facilitate customs review.