Chymosin

Function

Chymosin (also known as rennin) is the primary active ingredient in rennet. Rennet or

• chymosin is essential to the manufacture of firm cheeses. Chymosin splits the casein protein of milk at specific point and thereby effects clotting: casein clumps together to form curd and separates from the watery whey. Subsequently, the ripening process of cheese may begin.

Application

Chymosin is used exclusively in the manufacture of cheese.

However, it recently has become the case that the demand for cheese cannot be met with traditional rennet. Therefore, diverse rennet substitutes are in use. Such substitutes may also be plant-based (Galium verum). Microbial rennet substitutes also are widespread which are derived from (non-GM) microorganisms.

In comparison with classical rennet, such substitutes have disadvantages. During their use, enzymatic side reactions may occur that lead to undesirable changes in taste.

Gene technology

The production of chymosin with the aid of genetically modified organisms is widespread. A large part of global cheese production is conducted using GM chymosin.

Approval in Germany: In Germany, chymosin harvested from genetically modified micro-organisms is regarded as "rennet substitute" and must be allowed according to the regulations applicable to cheese. Since 1997, three chymosin preparations officially have been approved. These preparations, and the cheese made with their aid, may be marketed freely.

Approval exists in almost all western and eastern European countries (except France and Austria) as well as in the USA.

Application: According to estimates, between 80 and 90 per cent of cheese in the USA and Great Britain is manufactured using chymosin produced using gene technology. Exact statistics on German usage are unavailable. It is to be assumed that such chymosin is in use.

The majority of the applied chymosin is retained in the whey (see whey powder) and, at most, may be present in cheese in trace quantities. In ripe cheese, the type and provenance of chymosin used in production cannot be determined.

Labelling: Neither rennet nor chymosin is regarded in Germany as a food ingredient and is therefore not declared in the list of ingredients. Labelling of cheese in regard to gene technology and the use of chymosin is not required.

New EU regulations take effect in 2013. Since chymosin remains in the cheese it has to be declared as an ingredient on the list of ingredients. The use of genetically modified organisms in the production process is not explicitly labelled on the product.