What we need to prepare this slightly sour and very refreshing snack is fresh milk (not UHT – that’s important) and the juice of a lemon. Let them sit for a few minutes and you will see when you stir the mixture that the milk is starting to thicken, as the acidity of the lemon reacts with the milk protein, causing it to coagulate. This curdling process, and the curds it creates, explain why the product is also sometimes called curd cheese.
The next step is to separate the curds from the fluid. Take a coffee filter and a coffee filter paper, and place them over an empty glass. Pour in the mixture. The fluid (whey) drips into the glass below, leaving the curd cheese in the filter above. We are not adding any rennet, as DMK does in its plants, so our quark will be softer than what you might buy at the store. Don’t wait too long to eat it. And don’t miss out on the green-yellow whey in the jar either, as it is fresh and tasty, thanks to the lemon.
Rennin is an enzyme that used to be extracted from calves’ stomachs. Nowadays, microbial rennet is used to begin the coagulation process and start curdling the milk.
Lactic acid bacteria metabolize the lactose into lactic acid. The protein in milk is sensitive to acidity and the lactic acid causes it to precipitate, making the milk thicker (fermentation process). The bacteria used influences the taste of the product, its consistency and creaminess. Each producer uses a different strain of bacteria to shape the product’s specific character.