In this study, immediate and long-term effects of high intensity ultrasound on crystallization mechanisms of anhydrous milk fat were examined. Short time (5 s) ultrasound treatment (24 kHz, 300 W/cm 2 , 17.5 J/mL) of milk fat induced crystallization onset at higher temperatures and a longer temperature interval between the crystallization of the high and low melting fractions. The solid fat content in ultrasonicated milk fat was higher during cooling to 5°C and for the first 20 min of incubation at this temperature. After 20 min, the increase diminished, and during further storage, the solid fat content in the ultrasonicated fat remained lower than in the nontreated fat. Ultrasound treatment promoted the formation of spherulite structures and a high degree of size uniformity. Nano-and microscopic changes lead to altered macroscopic properties, where a softer and less brittle milk fat material was obtained, and the effects were sustained during storage. These results contribute to clarify the mechanisms underlying the effects of ultrasound treatment on fat crystallization and shed light on the potential use of ultrasound in the processing chain to tailor products with desired textural properties.

In this study, the impact of high intensity ultrasound (HIU) treatment on anhydrous milk fat and milk fat/rapeseed oil blends with 10–30 w/w% rapeseed oil is examined. Effects of HIU treatment on crystallization kinetics, thermal behavior, microstructure, texture, and oxidation are evaluated. HIU treatment results in an acceleration of the crystallization process, especially for blends with a high rapeseed oil content. HIU treatment reduces the crystal size, however, HIU treatment does not have any significant effects on the melting behavior or hardness. No significant effects of HIU treatment on secondary oxidation products are observed, indicating that lipid oxidation is not facilitated by the HIU treatment. Practical Application: A great potential exists for the use of use of high intensity ultrasound in the food industry to obtain a shorter and more controllable fat crystallization process. Results from this demonstrate how the impact of ultrasound treatment is affected by diluting a hard fat with liquid oil. Such effects are of great importance in, for instance, the dairy industry, where high intensity ultrasound potentially provides an additional processing tool in the production of spreadable blends based on milk fat and rapeseed oil. Ultrasound treatment is introduced in a circulating flow system, a more realistic representation of an industrial setting compared with commonly used probe based bath systems. High intensity ultrasound accelerates the crystallization kinetics of anhydrous milk fat and rapeseed oil blends, resulting in the formation of smaller crystals but no differences in melting properties or hardness. This is obtained in a circulating flow cell, without detection of increased levels of secondary oxidation products.

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