Rennet / Chymosin (Milk-Clotting Enzyme)とは？用途・使用量・代替品・規格

Rennet, English name is Chymosin (also known as Rennet), chemically classified as an aspartic protease (EC 3.4.23.4), with CAS number 9001–98–3. It is a natural protease located in the stomach cells of mammals that can efficiently and specifically hydrolyze the Phe105-Met106 peptide bond of κ-casein in milk, causing milk proteins to coagulate into curd, thereby effectively separating whey from curd. As an irreplaceable key enzyme preparation in cheese production, it occupies a strategic core position with the widest application and most urgent demand in the global food industry and dairy processing. In terms of chemical structure, chymosin belongs to the aspartic protease family, containing approximately 340—365 amino acid residues, with a molecular weight of about 35—40 kDa. Chymosin is synthesized as a precursor form – prochymosin – which is automatically activated to active chymosin under acidic conditions (pH approx. 2). Recombinant chymosin (fermentation chymosin) is the gold standard for cheese production and is considered the most ideal milk-clotting enzyme for global cheese processing. Chymosin typically appears as a white to light yellow powder, granules, or liquid, almost odorless and tasteless. It is stable and optimally active in acidic media, with reduced thermal stability under neutral to alkaline conditions. The significant advantage of chymosin lies in its extremely high substrate specificity, only specifically hydrolyzing the specific peptide bond of κ-casein without significantly degrading other milk proteins, thus not forming bitter peptides and preserving the mild, balanced original flavor of cheese.

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Chymosin is recognized as the soul of cheese, holding an undisputed dominant position in the scaled and standardized production systems of global industrial cheese and traditional handmade cheese. As the most efficient mammalian milk-clotting enzyme, its scientific and economic value is very prominent in the dairy industry. Its core competitiveness comes from four dimensions: extremely high substrate specificity, mild curd quality and flavor control, highly efficient and economically suitable clotting activity and heat sensitivity, and sustainable production through recombinant technology that overcomes the limitations of animal sources. 1 High Substrate Specificity – High-Quality Preservation: Chymosin only hydrolyzes the Phe105-Met106 peptide bond of κ-casein, hardly acting on other types of caseins, thus not producing bitter peptides from casein degradation. This ensures balanced and pleasant cheese flavor after ripening, suitable for both direct consumption and further processing. This is a premium advantage that common commercial proteases cannot match. 2 Sufficient Clotting Strength, Very Low Self-Digestion Risk: The ratio of clotting activity to proteolytic activity of chymosin is very high. In standard cheese manufacturing, this means it can complete curdling within several tens of minutes, yet does not cause subsequent texture collapse or bitter defects in the product, maximizing the retention of the original texture of fat and protein in fresh milk. 3 Heat Sensitive, Easy Process Control: Chymosin is a protease that is easily inactivated when heated and is rapidly inactivated under conventional pasteurization conditions. Once curdling is completed and the process enters the hot stretching or ripening stage, residual enzyme activity is effectively inhibited under heating conditions, avoiding flavor deviations and texture problems caused by excessive hydrolysis. 4 Clean Label, High Genetic Safety: Since its approval by the US FDA in 1990, fermented/recombinant chymosin has become the standard in the global cheese industry. Microbial fermentation or recombinant chymosin does not involve the slaughter of calves, offering outstanding competitiveness in ethics and sustainability. 5 Supply Ecological Safety, Low Cost, Stable Source: To address the supply shortage and high price of calf rennet, which only meets 20–30% of global cheese production demand, the first recombinant chymosin approved in 1990 was produced by recombinant E. coli fermentation, ushering in the industrial production of chymosin.