Whey leakage, also known as curd slippage, occurs when the thin rind of the cheese gives way and the moist curd inside, rich in whey, seeps out during ripening. This not only compromises appearance but also alters the flavor profile, introducing bitter and sharp notes. The main cause is often the type of rennet used: an excess of pepsin—present in certain blends—has such an intense proteolytic action that it weakens the casein network, leaving the rind unable to contain the inner mass.
However, the cause is not always limited to the coagulant; whey management also plays a key role. When whey expulsion is insufficient, fermentation continues and proteolysis intensifies: overly coarse curd cutting retains more liquid in the granules, while curd-cooking and ripening temperatures kept below 12 °C slow evaporation and promote moisture buildup. The use of “defective” milk—such as from cows affected by mastitis—also alters the mechanical properties of the curd, increasing the risk of whey leakage.
To counter this, careful control during stufatura (curd resting) and pressing is essential to promote additional controlled whey expulsion and strengthen the rind. Another effective measure is choosing rennet from suckling animals that is rich in chymosin and low in pepsin, to better regulate the speed and intensity of proteolysis.
During ripening, constant monitoring of temperature and humidity allows the stufatura cycle to be interrupted at the first sign of rind deformation, preventing sudden ruptures. Finally, quick analysis of the incoming milk’s protein content can detect batches excessively rich in abnormal proteins, allowing them to be discarded or pretreated before coagulation. In certain contexts—such as the production of Squacquerone di Romagna—this same phenomenon is intentionally sought after: controlled whey leakage gives the cheese a soft, fluid texture and a delicate, slightly tangy flavor, becoming a hallmark of one of Italy’s most appreciated fresh cheeses.
