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Foamed food products like ice cream, chocolate mousse, fresh cheese or bakery products are increasingly popular due to their soft and creamy sensory properties.The perception, stability and ow behavior of food foams strongly depend on gas fraction and bubble size distribution. Ideally, foams contain smallest possible gas bubbles of equal size. If the gas bubbles are small enough, they can not be distinguished from fat particles in the mouth. Hence, fat can be replaced by gas, leading to a fat-free yet creamy product. A narrow size distribution slows destabilization mechanisms, and thus, the amount of stabilizers can be reduced or the shelf life prolonged. In numerous life science related application areas foams are manufactured using rotor-stator gas dispersing devices where gas is added to the uid mix and dispersed by the ow forces (shear, elongation, inertia) acting in the whipping head. Improvements with regards to foam characteristics are often achieved by altering the ingredients composition but maintaining the same processing conditions. Contrary to this approach, the focus of this work was to understand and develop a new foaming process in which smaller and more narrowly distributed bubbles can be achieved without changing the recipe. were found for viscosity ratios between 3.1 · 10 −7 and 6.7 · 10 −8 , respectively.Another aim of this study was to determine the impact of reduced static pressure acting during the foaming process on the resulting foam microstructure. Since the gaseous disperse phase is compressible, static pressure plays a major role in foam production. Commonly, industrial foam production takes place in a pressure range of 2 -4 bar absolute in order to reduce the eective gas volume fraction in the whipping device. However, the bubbles expand as soon as they are exposed to atmospheric pressure. To investigate the inverse eect, namely a bubble shrinkage during adaptation to atmospheric pressure, the static pressure in the whipping head was reduced to partial vacuum of 0.6 bar. The comparison of pressures between 0.6 and 4.0 bar, however, showed that best foaming results are achieved at atmospheric pressure compared to both increased and reduced static pressure.For foams whipped at increased pressure, the bubbles grew during expansion to xxvii Abstract atmospheric condition while at reduced pressure coalescence probability was in-

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