The uses of ultrasonic power and solvents in lactose cooling crystallisation

This paper studies the role of ultrasonic power, solvents and cooling strategies to make fine lactose particles for use as seed slurries in the dairy industry. The objective is to select optimum levels of power and solvents to produce the finest possible crystals in the highest yield. Lactose syrup at 44°Brix was rapidly cooled and held at low temperatures in a 2L crystalliser while an organic solvent and ultrasonic power at different levels were introduced. Short chain alcohols and acetone were tested to measure their effects on the shape, particle average size, size distribution range, number of nuclei formed and beta to alpha isomer ratio of the products. Introducing ultrasonic power at 0.1 W/g mixture and ethanol at a ratio of 0.17 g/g mixture at low temperatures enabled the extraction of a high total mass of solid finer than 20 mm. These crystals have almost perfect shape with minor changes in morphology, less agglomeration and consequently faster growth rate compared to particles collected from common size reduction methods.