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Incorporation of high intensity ultrasound (HIU) to a scraped surface heat exchanger: Effect of HIU position

da Silva, Thais Lomonaco Teodoro, Martini, Silvana
Journal of food engineering 2020 v.274 pp. 109824
barrels, binding capacity, crystallization, hardness, heat exchangers, lipid content, microstructure, oils, thermal properties, ultrasonics, viscoelasticity
The objective of this work was to introduce high-intensity ultrasound (HIU) in different positions within a scraped surface heat exchanger (SSHE) and evaluate the crystallization behavior and physical properties of a low saturated, soybean-based fat. The SSHE in this study was composed of one pump (flow rate of 11 L/h), two crystallization barrels (32 °C, 344 rpm), and one pin worker (208 rpm). HIU was placed before the first crystallization step, or barrel 1 (HIU-0), between the two barrels (HIU-1), between barrels 2 and the pin worker (HIU-2) and after complete crystallization in the SSHE (HIU-3). HIU amplitudes of 20% or 50% using 5-s pulses were used. Physical properties of the crystallized material such as microstructure, solid fat content, oil binding capacity (OBC), viscoelasticity, hardness, and melting behavior were evaluated. HIU induced crystallization and improved all physical properties when positioned at HIU-2 and HIU-3 using 50% amplitude, but in HIU-3 the effect was more pronounced than in HIU-2. Samples sonicated using 50% amplitude at HIU-3 position showed the following improvements (p < 0.05): OBC increased from 63% to 86%, elasticity (G’) values increased from 23 kPa to 97 kPa, and hardness from 2.2 N to 3.7 N. With these results, we can conclude that HIU can be used in combination with a SSHE and that the point at which HIU is incorporated is important. The position that produced the best results was when HIU was placed after primary nucleation had occurred in the SSHE and when using higher power levels (50% amplitude).