Design parameters for the separation of fat from natural whole milk in an ultrasonic litre-scale vessel

Abstract

The separation of milk fat from natural whole milk has been achieved by applying ultrasonic standing waves (1MHz and/or 2MHz) in a litre-scale (5L capacity) batch system. Various design parameters were tested such as power input level, process time, specific energy, transducer–reflector distance and the use of single and dual transducer set-ups. It was found that the efficacy of the treatment depended on the specific energy density input into the system. In this case, a plateau in fat concentration of ∼20% w/v was achieved in the creamed top layer after applying a minimum specific energy of 200kJ/kg. In addition, the fat separation was enhanced by reducing the transducer reflector distance in the vessel, operating two transducers in a parallel set-up, or by increasing the duration of insonation, resulting in skimmed milk with a fat concentration as low as 1.7% (w/v) using raw milk after 20min insonation. Dual mode operation with both transducers in parallel as close as 30mm apart resulted in the fastest creaming and skimming in this study at ∼1.6g fat/min.