Sampling from the vat during cheesemaking may be necessary to study the impact of curd washing, which affects both whey composition and the curd's aqueous phase. The objective of this work was to develop a sieving protocol of curd-whey samples, ensuring enough time for drainage of the free whey, while limiting the loss of the aqueous phase entrapped in the curd grains. We studied the flow rate and lactose content of whey during sieving. Both measurements showed a two-stage dynamic representation of both aqueous phases, the intersection indicating the transition point between the flow of free and entrapped whey.