Animal rennet

The Rennet Animal is a substance present in the mucosa of the fourth stomach of ruminants mammals, mainly it contains enzyme called rennin , is also known as chymosin, used in the manufacture of cheeses whose function is to separate the casein (80% approximately of the total protein ) of its liquid phase ( water , whey protein and carbohydrates), called whey.

Vegetable rennets are used in the manufacture of some cheeses, which usually come from the flower of the thistle ( Cynara cardunculus or Cynara humilis ), wild variety).


The word “rennet” derives from the Latin verb “agere”; thus “coagulum” was ‘a consolidated lump of a liquid’.

Function and procurement

The enzyme’s action on casein and calcium dissolved in milk to form calcium paracaseinate, commonly called rennet. The old rennet was obtained from the stomach of lactating calves. A part of the stomach was immersed in brine , and after allowing it to rest until the renin diffused into the brine, part of that liquid was used in the milk to curdle. The drawback of this ancient method lies in the difficulty in obtaining precise doses of rennet, and in its variability of concentration throughout its time of use. Chemical rennet, pure chymosin, does not have this drawback, making it easier to standardize curdling times.

As for pure rennet, there are natural rennet: chymosin extracted by cutting from calves ‘stomachs, and synthetic rennet, discovered a decade ago and presented in tablets: it is chymosin obtained from chemical synthesis procedures without using calves’ stomachs like raw material.

In ancient times, shepherds used pieces of the stomach to curdle the milk , then they went to immerse them in brine, letting them rest so that the chymosin spread, and later this brine was in charge of curdling the milk, they obtained the first rennet extract.

The action of chymosin is well known to the dairy industry. It acts directly on a delimited point of casein with calcium. By altering this molecule, the formation of a gel that traps most of the solid components of milk begins; This gel contracts little by little, helped by the previous acidification of the milk by means of lactic acid bacteria, and when it contracts, it expels serum. A gel cutting the dicing, is capable of separating by 50 and 90% of the initial content of the whey milk .

The effectiveness of rennet is a function of temperature , the concentration of the substrate (milk), calcium concentration , and acidity. The usual coagulation temperatures can vary between 28 ° C and 41 ° C, although the most usual one is 35 ° C, depending on the type of cheese, milk mixes can be made with an acidity that can vary between 0.18 % of titratable acidity up to 0.46%.


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