no pressure is applied, but the molds are inverted frequently to promote this process. Salt is then added to provide flavor as well as to act as a preservative so the cheese does not spoil through the process of brine salting or dry salting for 24–48 hours. The final step is ripening the cheese by aging it. When the cheese is freshly made, there is little to no blue cheese flavor development. Usually, a fermentation period of 60–90 days are needed before the flavor of the cheese is typical and acceptable for marketing. During this ripening period, the temperature and the level of humidity in the room where the cheese is aging is monitored to ensure the cheese does not spoil or lose its optimal flavor and texture. In general, the ripening temperature is around eight to ten degrees Celsius with a relative humidity of 85–95%, but this may differ according to the type of blue cheese being produced. At the beginning of this ripening process, the cheese loaves are punctured to create small openings to allow air to penetrate and support the rich growth of the aerobic Penicillium roqueforti cultures, thus encouraging the formation of blue veins. Throughout the ripening process, the total ketone content is constantly monitored as the distinctive flavor and aroma of blue cheese arises from methyl ketones (including 2-pentanone, 2-heptanone, and 2-nonanone) which are a metabolic product of Penicillium roqueforti. Once the specified level of total ketone production is attained, the blue cheese is sterilized at ultra high temperature/short time at for four seconds. This heat treatment also inactivates the Penicillium roqueforti, inhibiting further fermentation. Toxins from the production of blue cheese Penicillium roqueforti, responsible for the greenish blue moldy aspect of blue cheese, produces several mycotoxins. While mycotoxins like roquefortine, isofumigaclavine A, mycophenolic acid and ferrichrome are present at low levels, penicillic acid and PR toxin are unstable in the cheese. Because of the instability of PR toxin and lack of optimal environmental conditions (temperature, aeration) for the production of PR toxin and roquefortine, health hazards due to Penicillium roqueforti metabolites are considerably reduced. Additionally, mycotoxin contamination occurs at low levels and large quantities of cheese are rarely consumed, suggesting that hazard to human health is unlikely. Physicochemical properties Structure The main structure of the blue cheese comes from the aggregation of the casein. In milk, casein does not aggregate because of the outer