Figure 3 shows an example of how HIU can be used in
combination with other processing conditions to tailor physi-
cal properties of the material. In this example, anhydrous milk
fat was crystallized with and without the addition of the emul-
sifier lactose monolaurate (LML). The emulsifier delayed the
crystallization of the fat, which increased the induction time of
crystallization at 31 °C from 34.2 ± 1.7 min to 47.1 ± 1.3 min
(Wagh, et al., 2013). This delay in the crystallization resulted
in a significantly less viscous crystalline network. However,
when the samples were crystallized in the presence of ultra-
sound, a significant increase in the viscosity of the samples was
obtained, and the viscosity of the sonicated fat and emulsifier
reached levels similar levels to those obtained in the unsoni-
cated fat (Figure 3). The use of HIU in this case was very helpful
in restoring the crystalline network lost in the samples due to
the addition of an emulsifier.
SOME pRaCTICaL CONSIDERa TIONS
The use of high-intensity acoustic waves is usually associated
with the generation of physical and chemical changes in materials. In contrast, research performed in our laboratory showed
that although sonication generated physical changes in edible
lipids, it did not produce any observable changes in the chemical properties of the material. For example, no changes in
oxidative stability (measured as peroxide value) or fatty acid
composition were observed. In addition, the sonicated shortenings did not exhibit any off-flavors when tested in baked
products such as cakes, cookies, and pie crusts (Zhong, et al.,
2014). It is important to note that changing the sonication conditions might produce different results. Our experiments used
HIU for very short periods of sonication time (10 sec) and a
relatively low power density (< 1W/cm3). Altering the power
levels, densities and duration of the pulse could theoretically
produce observable chemical effects.
The use of HIU as a tool in lipid processing is still in its infancy.
A significant amount of research must be performed to better
understand the effect of acoustic waves on lipid crystallization
and to optimize its use in a production plant. The effects that
HIU has on lipid crystallization depend strongly on the chemical composition of the initial material. That is, conditions
(power levels, crystallization temperature) that might work
for a specific fat might not work for a different one. Therefore
it is important to optimize the technique for a specific type of
fat and crystallization condition. With further development,
this novel technology could be an additional tool to tailor the
physical properties of lipids low in saturated fats and free of
trans-fats in a way that produces healthful and functional trans-fat replacers.
Silvana Martini is an associate professor in the Department
of Nutrition, Dietetics and Food Sciences at Utah State University. Martini is also a senior associate editor of the Journal
of the American Oil Chemists’ Society. Her research interests are related to the physicochemical and sensorial characterization of food materials—particularly lipids, and she
studies how the quality of food materials is affected by their
nano-, micro- and macroscopic characteristics. Martini has
participated in more than 100 conferences and published
57 peer-reviewed journal articles, seven book chapters, and
one book. She can be contacted at email@example.com.
FIG. 2. Effect of HIU on (a) hardness of anhydrous milk fat (AMF)
crystallized at different temperatures (Martini et al., 2010), and
(b) G’ values of a low saturated shortening crystallized at 32 °C
(Ye et al., 2011). HIU was applied for 10 sec using an acoustic
wave of 20 kHz.
FIG. 3. Effect of HIU on viscosity values of anhydrous milk fat
(AMF) crystallized at 31 °C with and without the addition of an
emulsifier (lactose mononlaurate, LML) (Wagh et al., 2013).
HIU was applied for 10 sec using an acoustic wave of 20 kHz.