Dairy products such as yogurt, kefir, and cheese result from similar processes. Outcomes that range from soft and spreadable quark to hard grana-style cheeses like Parmigiano–Reggiano DOP (Protected Designation of Origin in Italian) result from variations in process time, process temperature, and the selection of microbiological cultures. While the constancy of dairy products made by large cheese plants and skilled artisans is difficult to achieve at home, it is possible to make good versions of most dairy products with simple tools. After all, fermented dairy products predate the complex equipment and manipulations now common in milk processing.
Cheese, yogurt, and kefir all begin as milk, yet they finish with dramatically different appearances, textures, aromas, and flavors. Each variation represents a particular decision made along the way during processing. Home processors will find that while recipes for making yogurt, kefir, and cheese are helpful guides, the best way to develop reliable methods is over successive attempts. It helps to keep records of each batch so that the next effort can be just slightly tweaked to influence the outcome.