Rennet (rennin or rennilase) and cheese making:
Back in the 1960's, the world faced a severe shortage of calf rennet.
Rennet is a protease enzyme added to milk, along with certain bacteria, which coagulate milk proteins, producing the curds. This then separates from the liquid, whey.
The semi-solid curds are then treated by adding salt and then matured in containers to make the cheddar-style cheeses.
(Rennet is an enzyme found in the stomachs of young mammals, like calves, and is important in the digestion of milk proteins.)
Over the past 30 years, alternatives to calf rennet have been sought.
Alternative sources of Protease for coagulating milk:
There are a number of alternatives available, which are not derived from animal sources directly.
One form is comes from fungi, such as Rhizomucor miehei. Fungi produce natural proteolytic enzymes as part of their extracellular digestion process.
The other are from genetically modified microbes, such as E.coli bacteria, a fungus Aspergillus niger and food yeasts.
Obtaining Chymosin from yeast cells:
About 90% of hard cheeses like Cheddar are made now using chymosin from GM microbes.
Advantages of using GM Chymosin:
- Chymosin was the first enzyme to be approved for used in the food industry, so its effects are well known.
- Chymosin behaves exactly the same way as the animal equivalent, but due to its structure, it is much more predictable and there are fewer impurities.
- As it is made in yeast, it is fully accepted by vegetarians and some religious authorities.
Chymosin and GMO's:
Cheese produced using genetically engineered Chymosin is not regarded as a problem as it does not contain the organism, but the product (enzyme) of that GMO.
The enzyme does not remain in the cheese either, but soon breaks down, as it is a relatively unstable protein.