How is Stilton made?
Early each morning fresh pasteurized milk is fed into an open vat to which acid forming bacteria (starter cultures), a milk clotting agent (such as rennet) and "penicillium roqueforti" (blue mould spores) are added. Once the curds have formed, the whey is removed and the curds allowed to drain overnight. The following morning, the curd is then cut into blocks to allow further drainage before being milled and salted. Each cheese requires about 24 lb (11 kgs) of salted curd that is fed into cylindrical moulds. The moulds are then placed on boards and turned daily to allow natural drainage for 5 or 6 days. This ensures an even distribution of moisture throughout the cheese so that, as the cheese is never pressed, it creates the flaky, open texture required for the important blueing stage. After 5 or 6 days, the cylinders are removed and the coat of each cheese is sealed by smoothing or wrapping to prevent any air entering the inside of the cheese. The cheese is then transferred to the store where temperature and humidity are carefully controlled. Each cheese is turned regularly during this ripening period. At about 5 weeks, the cheese is forming the traditional Stilton crust and it is then ready for piercing with stainless steel needles. This allows air to enter the body of the cheese and create the magical blue veins associated with Stilton.
At about 9 weeks of age, by which time each cheese now weighs about 17 lbs (8kgs), the cheese is ready to be sold. But before this happens every cheese must be graded using a cheese iron. The iron is used to bore into the cheese and extract a plug of cheese. By visual inspection and by smell the grader can determine whether the cheese is up to the mark and able to be sold as Stilton. Cheese that is not up to the mark will be sold as "blue cheese."
At this age, Stilton is still quite crumbly and has a slightly acidic taste. Some customers prefer a more mature cheese and after a few more weeks it will start to develop a smoother, almost buttery texture, with a more rounded mellow flavor.