From milk to curd:
To make cheese it is essential to separate milk into its curds and whey (solids and liquids). Curds consist of protein, milk sugars or lactose and fats. Liquid or whey is mainly water with some/ little protein. To achieve separation the milk is warmed to about 30ºC degrees to provide the perfect environment for the lactic bacteria in the milk to attract the lactose and convert into lactic acid ( causing the milk to go sour). To speed the process up (acidification and fermentation) a starter culture is added to the milk. However a natural starter culture occurs in raw milk, so in raw milk cheese production the cheesemaker can make it from the previous day's milk. If the milk is pasteurised then bacteria must be introduced. A coagulant is added after the starter culture; the most commonly used is rennet (which is an enzyme which is present in the stomach of milk feed animals. Its original purpose is to coagulate mothers milk in the infants stomach into solids and liquid). Animal rennet is still the most effective at ensuring that the majority of the solids (proteins and fats) are separated out and not left in the whey. Many cheeses now include a non-animal rennet making them suitable for vegetarians. This can be fungus based or created by changing the DNA structure of a yeast, but with the debate as to the safety of genetically modified products; cheese makers decide which is best in their process.
From curd to cheese:
When the milk is coagulated it turns into a jelly like blancmange, to separate the more solid curds from the liquid whey the cheese maker simply cuts the curd. The essence of cheese is its ability to last, so the more moisture extracted from the curd the longer the cheese will remain edible and keep its nutritional value. There are many different ways of squeezing the whey out of curd when making cheese. (i)The more times the curd is cut more whey is released, (ii)raising the temperature of the curd will cause the curd to contract and expel more moisture, (to the extent this is done determines the type of bacteria survive in the curd which has a significant effect on flavour development in the maturing process). (iii)Curds can also be stacked for example when newly formed cheeses are made and when still in their moulds, they are placed in stacks one on top of another (in towers) each pressing out more moisture from each other, over a period of time usually overnight.
The addition of salt is a key stage and fundamental in the preservation process, it has several functions in the cheese making process. Some immediate and some more long term. (i)When salt is applied directly to the cut curds it pulls moisture out into the whey. At this early stage the salt also temporarily slows the acidification of the curd by inhibiting the action of the acid producing bacteria. (ii)When salt is added to the rind of the cheese through brining or dry salting moisture is drawn out of the curds surface and evaporates, the surface of the cheese becomes dryer and a rind is formed. (iii)The amount of salt absorbed within the cheese also controls internal microorganisms, the cheese maker needs to get the proportions right to support the important microbes which help to develop flavour and ripen the cheese over the maturation period. This has a direct impact on how the cheese will taste.
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