Blue cheese is believed to have been discovered by accident when cheeses were stored in natural temperatures and moisture-controlled caves which happen to be favorable environments for many varieties of harmless mold. It was moist in the cave so the mold would form. According to legend, one of the first blue cheeses, Roquefort, was discovered when a young boy, eating bread and ewes’ milk cheese, abandoned his meal in a nearby cave after seeing a beautiful girl in the distance. When he returned months later, the mold (Penicillium roqueforti) had transformed his cheese into Roquefort.
Gorgonzola is one of the oldest known blue cheeses, having been created around AD 879, though it is said that it did not contain blue veins until around the 11th century. Stilton is a relatively new addition, becoming popular sometime in the early 1700s. Many varieties of blue cheese that originated subsequently, such as the 20th century Danablu and Cambozola, were an attempt to fill the demand for Roquefort-style cheeses that were prohibitive due to either cost or politics.
Cambozola, a German variety of blue cheese
Similarly to other varieties of cheese, the process of making blue cheese consists of six standard steps. However, additional ingredients and processes are required to give this blue-veined cheese its particular properties. To begin with, the commercial scale production of blue cheese consists of two phases: the culturing of suitable spore-rich inocula and fermentation for maximum, typical flavor.
Penicillium roqueforti inoculum
In the first phase of production, a Penicillium roqueforti inoculum is prepared prior to the actual production of blue cheese. Multiple methods can be used to achieve this. However, all methods involve the use of a freeze-dried Penicillium roqueforti culture. Although Penicillium roqueforti can be found naturally, cheese producers nowadays use commercially manufactured Penicillium roqueforti. First, Penicillium roqueforti is washed from a pure culture agar plants which is later frozen. Through the freeze drying process, water from the frozen state is evaporated without the transition through the liquid state (sublimation). This retains the value of the culture and is activated upon the addition of water.
Salt, sugar or both are added to autoclaved, homogenized milk via a sterile solution. This mixture is then inoculated with Penicillium roqueforti. This solution is first incubated for three to four days at 21–25 °C (70–77 °F). More salt and/or sugar is added and then aerobic incubation is continued for an additional one to two days. Alternatively, sterilized, homogenized milk and reconstituted non-fat solids or whey solids are mixed with sterile salt to create a fermentation medium. A spore-rich Penicillium roqueforti culture is then added. Next, modified milk fat is added which consists of milk fat with calf pre-gastric esterase. This solution is prepared in advance by an enzyme hydrolysis of a milk fat emulsion. The addition of modified milk fat stimulates a progressive release of free fatty acids via lipase action which is essential for rapid flavor development in blue cheese. This inoculum produced by either methods is later added to the cheese curds.