with very high and localized temperatures (5,000–10,000 K),
shear forces, and pressures ( 100–5,000 atm) that can generate physicochemical changes in the material where the wave is
This type of technique has been mainly used to induce or
accelerate the rate of chemical reactions and to induce the crystallization of inorganic and organic molecules. HIU has also
been used in several food science applications such as homogenization, ultrasound assisted extraction, pasteurization, and
defoaming, to name a few (Rastogui, 2011). Recently several
researchers have shown that HIU can be used as an additional
processing tool to process lipids commonly used by the food
HIU USED TO CHaNGE THE pHYSICaL
pROpERTIES OF LIpIDS
HIU was first used to change the crystallization of edible lipids
by Sato’s group (Higaki, et al., 2001; Ueno, et al., 2002, 2003) ,
followed by Patrick, et al. (2004). These authors showed that
HIU accelerated formation of the most stable polymorphic
form in cocoa butter, tripalmitin, trilaurin, trimyristin, and
tricaprin (Higaki, et al., 2001; Ueno, et al., 2002, 2003) and
induced the crystallization of palm oil (Patrick, et al., 2004).
Further research by Martini (Martini, et al., 2008; Suzuki, et
al., 2010; Ye, et al., 2011; Martini, et al., 2012; Wagh, et al.,
2013; Chen, et al, 2013) has shown that this technique can
also be used to alter the hardness, viscoelasticity, crystal size,
melting behavior, and other physical properties of the crystalline network that is formed.
Effect of HIU on crystal size and morphology: One of the
most significant effects of HIU is in the generation of small
crystals. Figure 1 shows pictures of crystals from different fats
systems— anhydrous milk fat (AMF), palm kernel oil (PKO),
and all-purpose shortening (APS)—taken with a polarized
light microscope. A significant reduction in crystal size can be
observed as a consequence of sonication (20 kHz, 10 sec). In
addition, some studies report changes in crystal morphology
possibly due to the formation of different polymorphic forms
(Patrick, et al., 2005; Martini, et al., 2008; Suzuki, et al., 2010;
Ye, et al., 2011; Chen, et al., 2013).
Effect of HIU on melting behavior and amount of solids: In
addition to the effect on crystal size and morphology, HIU can
generate a crystalline network with higher amounts of solids
(Suzuki, et al. 2010; Chen, et al., 2013). However, the effect of
HIU on inducing the formation of more solids depends on the
chemical composition of the fat and the processing conditions
that are used (crystallization temperature, storage time, sonication time and power). For example, higher amounts of solids
were generated in palm oil, palm kernel oil, and anhydrous
milk fat but no differences in the amount of solid material were
observed for commercial shortenings (Suzuki, et al. 2010; Ye,
et al., 2011) or for anhydrous milk fat crystallized at low temperatures (Suzuki , et al., 2010). Interestingly, HIU also affects
the melting behavior of the crystalline network that is formed.
In general, sonicated samples melt faster and within narrower
temperature ranges, which results in a sharper melting profile
(Suzuki, et al., 2010; Ye,, et al. 2011).
Effect of HIU on viscoelastic properties and texture: HIU
is very efficient at creating lipid crystalline networks with
increased texture, elasticity, and viscosity (Figure 2, page 116).
Changes in texture and viscoelastic properties of lipids
are mainly driven by the amount of solid material but also by
crystal sizes: The higher the solid content, the harder the material. However, given a similar content of solids, crystalline networks with smaller crystals tend to be harder and more elastic.
In general, the decrease in crystal size that results from sonication is the main factor responsible for generating a harder and
more elastic crystalline network.
• Higaki, K., S. Ueno, T. Koyano, and K. Sato, Effects of ultrasonic irradiation on crystallization behavior of tripalmi-toylglycerol and cocoa butter, J. Am. Oil Chem. Soc. 78:
• Martini, S., A.H. Suzuki, and R. W. Hartel, Effect of high-intensity ultrasound on crystallization behavior of anhydrous milk fat, J. Am. Oil Chem. Soc. 85: 621–628, 2008.
• Martini, S., R. Tejeda-Pichardo, Y. Ye, S.G. Padilla, F.K. Shen,
and T. Doyle, Bubble and crystal formation in lipid systems during high-intensity insonation, J. Am. Oil Chem.
Soc. 89: 1921–1928, 2012.
• Patrick M., R. Blindt, J. and Janssen, The effect of ultrasonic intensity on the crystal structure of palm oil,
Ultra-son Sonochem 11: 251–255, 2004.
• Rastogui, N.K., Opportunity and challenges in application of ultrasound in food processing, Crys Rev Food Sci
Nutr 51: 705–722, 2011.
• Suzuki, A., J. Lee, S. Padilla, and S. Martini, Altering functional properties of fats using power ultrasound, J. Food
Sci. 75: E208–E214, 2010.
• Ueno, S., R.I. Ristic, K. Higaki, and K. Sato, In situ studies
of ultrasound-stimulated fat crystallization using synchrotron radiation, J Phys Chem B 107: 4927–4935, 2003.
• Ueno, S., J. Sakata, M. Takeuchi, and K. Sato, Study for
ultrasonic stimulation effect on promotion of crystallization of triacylglycerols, Photon Factory Activity Report,
#20, Part B, page 182, 2002.
• Ye, Y., A. Wagh, and S. Martini, Using high-intensity ultrasound as a tool to change the functional properties of
interesterified soybean oil, J. Agric. Food Chem. 59: 10712–
• Wagh, A., M. Walsh, and S. Martini, Effect of lactose
monolaurate and high intensity ultrasound on crystallization behavior of anhydrous milk fat, J. Am. Oil Chem.
Soc. 90: 977–987, 2013.
• Zhong, H., K. Allen, and S. Martini, Effect of lipid physical
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continued on page 116