Incorporation of microbubbles into milk pasteurization for fouling mitigation

Abstract

The dairy industry faces significant challenges of fouling formation in processing equipment, which accounts for about 80 % of the total operating costs. In this study, we incorporated microbubbles (MBs), i.e., fine air bubbles with a respective diameter of 10 −100 μm, into milk and investigated their effect on fouling formation during pasteurization. Skim and whole milks were thermally treated using a spinning disc apparatus (SDA) operated at an initial surface temperature of 95 °C and different disc rotational speeds (50–150 rpm) to generate shear stress from 0.063–0.15 Pa, and MBs were infused into milk using a venturi-type generator. Computational fluid dynamics (CFD) simulations were performed to model the interactions between the flow and MBs in the SDA. Simulations indicated that MBs accumulated in the vicinity of the disc with average density decreasing by 60 % as the disc rotational speed increased from 50 to 150 rpm. The fouling curves revealed that the presence of MBs in milk caused removal of formed deposit, resulting in less fouling in all cases. Among the types of milk and shear stresses tested, MBs led to the largest reduction in fouling when incorporated into skim milk and operated under 0.077 Pa, from 0.0134 to 0.0052 m²K/W. Besides, protein carbonyl measurements showed that MB treatments did not induce protein oxidation in milk. The results proved that MBs can serve as a novel agent for incorporation into milk pasteurization to effectively mitigate fouling formation in heat exchanger, thereby reducing the operating costs and improving the productivity of dairy processing plants.