Incorporation of high-intensity ultrasound in a scraped surface heat exchanger

The objective of this research was to evaluate if high-intensity ultrasound (HIU, 20 kHz) could be used in a scraped surface heat exchanger (SSHE) to change the physical properties of low saturated fats. Experiments were performed in a 20L/h SSHE with two temperature-controlled barrels and one pin-worker where HIU was incorporated using a flow cell within the SSHE at various positions and time/power combinations (5 or 10 s/20-80% amplitude). Soybean- and palm-based fats were tested at various crystallization temperatures (20-32°C) and agitation conditions (344 and 185 rpm). These fats had similar melting points (~42°C) and low levels of saturated fatty acids (~32%).
For the soybean-based fat, the best results were found when the HIU was placed at the end of the SSHE (after the pin worker) or between the second barrel and the pin worker. Intermediate power levels for short pulses (5 s) were the most efficient at inducing the crystallization in the soybean-based fat crystallized at 32°C when sonication was applied after the pin worker.
Similar experiments were performed in the palm-based sample, but a lower temperature and higher supercooling was needed to obtain a significant amount of crystals. The best sonication condition found for the palm-based sample was when HIU was placed after first barrel, using 50% amplitude and 10 s pulses at 20°C. .
In addition, the effect of agitation was tested in the soybean sample and results showed HIU improved the physical properties of the sample when placed at any position of the SSHE when low agitation was used for the soybean- and the palm-based samples.
These results show that HIU can be incorporated in a SSHE process to induce secondary nucleation and improve the physical properties of low-saturated fats. However, processing and sonication conditions must be controlled to ensure desired results.