What makes Cheddar "Sharp"?
As the cheese ages, especially in the early phases, the first two months of aging, the culture that was originally added to the milk is multiplying. As time passes the cultures are growing and eating more and more of the lactose in the milk and changing it to lactic acid. Lactic acid is what gives certain types of cheeses their sharpness or tanginess. Sharp Cheddar is sharp because of the lactic acid. That is why older Cheddar is sharper, because the culture has had more time to eat the lactose and change it to lactic acid. Eventually, all of the lactose in the milk will be eaten and changed into lactic acid. That is why cheese that is eight months or older is safe for lactose intolerant people to eat. After eight months, all of the lactose has been converted to lactic acid.
Cheddar begins as a cheese curd and as it ages, it becomes sharper and sharper!