The effects of application of ultrasonic waves to recombined milk emulsions (3.5% fat, 7% total solids) and raw milk on fat destabilization and creaming were examined. Coarse and fine recombined emulsions (D[4,3]=9.3 μm and 2.7 μm, respectively) and raw milk (D[4,3]=4.9 μm) were subjected to ultrasound for 5 min at 35°C and 400 kHz or 1.6 MHz (using a single transducer) or 400 kHz (where the emulsion was sandwiched between two transducers). Creaming, as calculated from Turbiscan measurements, was more evident in the coarse recombined emulsion and raw milk compared to that of the recombined fine emulsion. Micrographs confirmed that there was flocculation and coalescence in creamed layer of emulsion. Coalescence was confirmed by particle size measurement. These results imply that ultrasound has potential to pre-dispose fat particles in milk emulsions to creaming in standing wave systems and in systems with inhomogeneous sound distributions.

No abstract

This paper proposes a further potential improvement of the prediction using the Posthumus funnel. The application of the Posthumus funnel is cheaper than most rheological measurements; it is easier to handle and depending on the measurement does not need a calibration. Therefore, it represents a very promising possibility for enhancing the prediction of the texture properties of liquid and semisolid foods showing Ostwald‐de‐Waele and Newtonian properties. A model is introduced for Newtonian fluids to compute the geometry of the Posthumus funnel so that the shear rates that appear are in the same range as in the oral cavity, by treating it as a system of two cylinders connected via a nozzle. This model can also be applied to other technical applications. The model is verified by means of numerical simulations and experimentally by particle image velocimetry. This results in a ready‐to‐use model for product development or quality assurance. PRACTICAL APPLICATIONS In the preliminary work, it could be shown that the introduction of values derived from the Posthumus funnel can enhance the prediction accuracy of the mouthfeel attribute “oral viscosity” or consistency compared with rheological data from rheometers alone. During the oral processing of foods, they are subjected to a wide range of shear rates and a complex flow field. In this paper, a ready‐to‐use model is proposed to adapt the geometry of the empirical measurement technique Posthumus funnel to shear rates in the range where they appear in the oral cavity and an approach is introduced combining the Posthumus funnel with rheological flows. Therefore, the prediction capability is increased. This can be used by product developers or in quality assurance to obtain an approximate impression of the textural properties of liquid and semisolid foods such as yoghurt and custard sauce. The model can also be used for similar fields of fluid mechanics.