Ultrasound Acceleration of Milk Fat Separation

Ultrasonic separation of milk with high-frequency ultrasound (0.4–3 MHz) is a subject of interest for the dairy industry since it separates milk without centrifugal separators. The article introduces the optimal sonication modes for separation of nonhomogenized pasteurized milk. The research featured non-homogenized pasteurized milk sonicated at 0.88 MHz. The fat content analysis involved an Expert Profi ultrasonic analyzer (NPP Laboratorika, LLC). The experiments focused on the correlation between the milk fractionation and the processing time. The conditions were as follows: 880 kHz at continuous and pulsed sonication at 10 and 40℃. Both temperatures made it possible to accelerate the fractionation process. At 10℃, the fat content gradient between the upper and lower fractions was non-monotonic at continuous sonication. The pulse sonication (1 min sonication, 1 min exposure) made it possible to achieve a linear dependence. Ten minutes of sonication corresponded to a gradient of 4.74 wt.% after 24 h of refrigeration. The fat content of the original milk was 3.8%. Milk fat melted at 40℃, changing the correlation: the dependence of the fat content gradient on the sonication time became linear, and the separation rate was constant after sonication. To minimize the exposure to high temperatures, the longest separation time was 1 h at room temperature. The fat content gradient equaled 0.90 wt.% with the fat content of the original milk being 2.8%. In this study, sonication with 880 kHz accelerated the separation of homogenized milk. Pulse sonication was optimal at 10℃ while continuous sonication was most effective at 40℃.