Chymosin (rennet)
Chymosin is the aspartic protease that clots milk in cheesemaking by cutting kappa-casein. Animal rennet is an aqueous extract of the fourth stomach (abomasum) of calves, kids or lambs, while fermentation-produced chymosin (FPC) is made by yeasts, molds or bacteria carrying the prochymosin gene. Cheesemakers buy it as a liquid or powder standardized to a stated milk-clotting strength.
Suppliers sell different products under the same name. Specify the one you need.
Liquid or powder extract from calf, kid or lamb stomachs, containing chymosin with some pepsin; adult bovine rennet has a higher pepsin share.
Chymosin made by fermentation, such as bovine chymosin from Aspergillus niger or Kluyveromyces lactis, sold as a clear liquid and used in most industrial cheese.
FPC based on the camel chymosin gene, offered for lower proteolysis during ripening in some cheese types.
Liquid coagulants are dosed per volume of milk and usually kept refrigerated; powders and tablets suit small producers and longer storage.
Compare each result with your own specification when the lot arrives.
Keep liquid rennet and FPC refrigerated, usually between 2 and 8 °C, in closed opaque containers and away from light; do not freeze unless the supplier allows it. Powders and tablets are kept sealed in a cool, dry place. Shelf life is set by the supplier's specification as a minimum strength to a date, and older stock is checked for clotting strength before use.
Clotting strength can drift from the label, so record the IMCU for each lot and adjust the dose per liter of milk. Record the source (calf, adult bovine, camel FPC or microbial) and the vegetarian, kosher or halal status of each lot, and rotate stock first-expired, first-out.
Facts from regulators and standards bodies, each linked to its source.
21 CFR 184.1685 describes rennet as the aqueous extract of the fourth stomachs of calves, kids or lambs, and chymosin preparation as derived via fermentation from strains containing the prochymosin gene.
Source: ecfr.gov (opens in a new tab)21 CFR 184.1685 affirms rennet and chymosin preparation as generally recognized as safe as a direct human food ingredient, used in cheeses, frozen dairy desserts, puddings and milk products.
Source: ecfr.gov (opens in a new tab)GRN 230, for chymosin from Trichoderma reesei expressing the bovine prochymosin B gene (Genencor), closed with FDA having no questions.
Source: hfpappexternal.fda.gov (opens in a new tab)Health Canada's List of Permitted Food Enzymes includes rennet (item R.1) as aqueous extracts from the fourth stomach of calves, kids or lambs, and lists chymosin from fermentation sources.
Source: canada.ca (opens in a new tab)This is general information, not regulatory advice. Status differs by country and by how the ingredient is used, so check the rules for your product and market.
Manufacturers and distributors whose own websites say they sell it.
Manufacturer · Lyngby, Denmark
Sells it as Chy-Max
Danish biosolutions company formed from Novozymes and Chr. Hansen that supplies probiotic strains, HMOs, dairy cultures and enzymes to supplement, infant formula and food makers.
Manufacturer · Cadorago, Italy
Italian group producing lactic and probiotic cultures, starter cultures and rennet, supplying probiotic strains as single ingredients or blends to supplement and food makers.
Suppliers are in alphabetical order and none pays to appear. Each claim is checked against the supplier’s own website on the date shown. Ask for the specification sheet and a recent COA before you order, and confirm details with the supplier.
Common forms include animal rennet, fermentation-produced chymosin (FPC), camel chymosin and liquid vs. powder. Ask each supplier for the specification sheet of the exact grade they quote.
Expect milk-clotting strength, chymosin and pepsin composition, preservatives and salt, microbiology and source and production organism, each with its method, specification and result for that lot.
Keep liquid rennet and FPC refrigerated, usually between 2 and 8 °C, in closed opaque containers and away from light; do not freeze unless the supplier allows it. Powders and tablets are kept sealed in a cool, dry place. Shelf life is set by the supplier's specification as a minimum strength to a date, and older stock is checked for clotting strength before use.
21 CFR 184.1685 describes rennet as the aqueous extract of the fourth stomachs of calves, kids or lambs, and chymosin preparation as derived via fermentation from strains containing the prochymosin gene. 21 CFR 184.1685 affirms rennet and chymosin preparation as generally recognized as safe as a direct human food ingredient, used in cheeses, frozen dairy desserts, puddings and milk products. GRN 230, for chymosin from Trichoderma reesei expressing the bovine prochymosin B gene (Genencor), closed with FDA having no questions. Health Canada's List of Permitted Food Enzymes includes rennet (item R.1) as aqueous extracts from the fourth stomach of calves, kids or lambs, and lists chymosin from fermentation sources.
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