The Ingredient Essential to Diverse Cheeses: Time

This basic technique of curdling milk with the help of the stomach extract now called rennet, then draining and brining the curds, was eventually carried west and north into Europe. Here people gradually discovered that curds would keep well enough in these cooler regions with much milder treatments: a less puckery souring and only a modest brining or salting. This was the discovery that opened the door to the great diversification of cheeses, because it introduced a fifth ingredient after milk, milk bacteria, rennet, and salt: time. In the presence of moderate acidity and salt, cheese became a hospitable medium for the continuing growth and activity of a variety of microbes and their enzymes. In a sense, cheese came to life. It became capable of pronounced development and change; it entered the cyclical world of birth, maturation, and decline.