To enable the continuous aseptic preparation of the subject dough by passing an egg and a gas under pressure through a whipping apparatus in a casing, thereby applying a uniform whipping action necessary for forming bubbles in a short time, reducing the physical damage on the dough and increasing the frothing performance.

A solution containing a mixture of food materials such as egg, wheat flour, cow's milk and sugar is charged in a tank 2 and supplied under pressure to a whipping apparatus 5 with a pump 4 while introducing a gas from a gas source 3 into the solution under pressure. The solution and the gas are subjected to the whipping action in the course of passing through the whipping apparatus 5 to form a whipped material containing the gas entrained in the material in a state of uniformly distributed fine bubbles. The overrun is easily controllable by this process and the bubble-containing dough is continuously discharged from the apparatus.