Invited review. Milk clotting enzymes: A transcendental decision in goat<acute accent>s milk cheese quality

Cheese production has increased more than 3.5-fold since 1960, while animal rennet production has declined, thus other proteolytic enzymes have been developed. Cheese quality depend on many factors, some of them are linked to milk composition (genetic aspects: species, breed and animal, lactation stage and number, type of kidding, animal feeding and health, offspring season, etc.) and other due to cheesemaking aspects and storage processing (raw or pasteurized milk, coagulation enzymes and coagulation parameters (temperature and time), moulding, drainage, salting, ripening, smoking, etc.). All these factors interact and only under experimental conditions it is possible to analyse the effect of any particular feature by itself. Between all these factors, milk coagulation process is one of the most important steps for the cheese final characteristics. The differences in protein matrix degradation due the origin of coagulant agents affect cheese texture, odour, flavour and taste and consequently consumer's preference. This last assertion is especially important for the economic choices of the dairy firm. In the past, cheesemakers used animal rennet for curdling milk; it was produced by macerating the stomachs obtained from suckling ruminants according to the local uses, although plant coagulant was used in some typical specific cheesemaking processes. Nowadays, several types of coagulant are available, with different origin and variability in proteases for milk coagulation: animal origin rennet and vegetable coagulants than can be both artisan or commercial, microbial proteases and recombinant from genetically modified microorganism with cDNA for chymosin. In this paper the state of the art of these enzymes used in goat ' s cheese industry is presented, also focused on artisan cheeses. Coagulant effect in physical-chemical and sensory profile of cheeses is analysed, also under an ethical and religious point of view. Finally, the importance of the market target in producing new cheese with vegetable coagulant is met, with an overview on the trends on cheese labelling issue.