Quick Answer
Rennet can be harvested from young, non-vaccinated calves that are less than 20 days old, with the highest concentrations found in the first few days of life. It is essential to handle the rennet carefully to preserve its natural enzymes. When stored correctly, rennet can last for up to 6 months.
Harvesting Rennet
Harvesting rennet requires a sterile, clean environment to minimize bacterial contamination. To collect rennet, gently cut the umbilical cord and allow the newborn calf to nurse for 30 minutes to stimulate the release of rennet into the stomach. Then, carefully insert a sterile tube into the stomach to collect the rennet-rich fluid. The collected rennet should be transferred to a clean container and stored in the refrigerator at 40°F (4°C) within 30 minutes of collection.
Storing Rennet
Rennet is a natural enzyme that can be sensitive to temperature, light, and oxygen. To maintain its potency, store the rennet in a sterile, aseptic environment, away from direct sunlight and moisture. The ideal storage temperature for rennet is between 35°F (2°C) and 45°F (7°C), with a storage time of up to 6 months. Rennet can also be frozen for longer-term storage, with a shelf life of up to 2 years. When freezing, it is essential to use airtight containers or freezer bags to prevent contamination and freezer burn.
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