The first step in making cheese is coagulation of milk. Milk can be coagulated by the action of rennet enzyme or by acidification. The coagulum has a natural tendency to syneresis— contraction and expelling of whey (i.e., water and water-soluble compounds of the milk (Fig. 1). Larger particles such as fat globules and bacteria will be retained in the shrinking coagulum, the cheese curd. The syneresis can be accelerated by cutting up the gel and by heating. The resulting firm curd can be pressed and formed into cheeses of various shapes.
The fresh curd contains valuable nutrients and can therefore quickly be spoiled by bacteria, yeasts, and molds if not preserved. The main factors contributing to preservation are low moisture content (concentration), acidification by adventitious or added lactic acid bacteria, and salting. Spoilage of the cheese by molds on the surface can be prevented by drying and cleaning the surface or by exclusion of oxygen by immersion in brine or by coating the cheese with wax or synthetic film material.
Cheese may be consumed as fresh curd or it may undergo ripening by means of enzymes from the milk, from the rennet, and from microorganisms in the cheese or on the surface. During ripening, which may last for months, the organic solids of the cheese will gradually be hydrolysed and metabolized during which have the characteristic flavor, consistency, and texture of the cheese is being developed.
Was this article helpful?