Application of High Intensity Ultrasound to a Zero-trans Shortening During Temperature Cycling at Different Cooling Rates

Enhanced crystallisation kinetics of edible lipids through the action of a bifurcated streamer

The processing of healthy foods remains a challenge and any technology with the ability to tailor the physical properties of new materials is in demand. High-intensity ultrasound (HIU) has been identified as a useful processing technique for such activities particularly for edible lipids. HIU has been known to alter the crystallisation kinetics and in turn the resultant physicochemical properties for specific food applications. The role of cavitation dynamics during treatment of oils with HIU is of interest, with the knowledge gained allowing for insight into the complex and still undefined mechanism of action. To this end, the crystallisation kinetics of an edible lipid were investigated in the presence of several distinctly different cavitation conditions. Several cavitation clusters, including a bifurcated streamer (BiS), located on the surface of a piston-like emitter (PLE) were studied, each generated by a specific ultrasonic power level. Only samples crystallised at a low supercooling (ΔT_SC) value display significant differences in induction time for each of the selected HIU powers, at least 5 minutes earlier than without exposure to HIU. Substantially better energy efficiencies were seen for the BiS regime (ΔT_SC = 5 °C) which coincided with maximal crystal growth rates. An increase in melting enthalpy and elastic modulus is reported in the presence of HIU for all crystallisation temperatures, this effect is larger overall with increasing ultrasonic power. In addition, sonicated samples in the presence of the BiS event were composed of fewer smaller crystals compared to higher HIU powers after 60 minutes at 30 °C. Bubble dynamics recorded during a 10 s sonication period exhibited a greater acoustic attenuation effect for the highest ultrasonic power (75 W). The results suggest that the dynamics of the cluster and the presence of the BiS event are important in terms of energy efficiency and the physical properties of the crystallised lipid material.

Ultrasound-mediated interfacial protein adsorption and fat crystallization in cholesterol-reduced lard emulsion

Lard with a substantially reduced cholesterol content through aqueous enzyme extraction is an attractive source of lipid in healthy and nutritious emulsion food product development. The objective of this study was to elucidate the crystallization behavior (4-20 °C) of emulsions prepared from low-cholesterol lard in relation to protein emulsifier (2 and 4% whey protein isolate, WPI) and ultrasound (475 w, 5 min) treatments. The physicochemical properties and fat crystallization pattern of the emulsions were investigated. Emulsions with 4% WPI were superior to those with 2% WPI on interfacial adsorption and crystal size reduction. Ultrasonic treatment of prepared emulsions further decreased fat crystal size, promoted small and uniform crystal distribution, and slightly destabilized emulsions. Protein concentration and ultrasonic treatment had no obvious effect on crystal transition from β' to the more stable β-form based on X-ray diffraction. The melting properties determined by differential scanning calorimetry indicated that emulsified lard had a lower onset melting temperature than bulk lard, and with ultrasound treatment, the melting enthalpy increased remarkably. The ultrasound-induced change in fat crystalline structure and emulsion meta-stability may be valuable to the manufacture of healthy, emulsion-incorporated food products.

Application of high-intensity ultrasound to palm oil in a continuous system

High-intensity ultrasound (HIU) was used in a continuous system to change the crystallization behavior of palm oil. Different power levels (75, 110, and 180 W) and pulse durations (continuous application and 5, 10, and 15 s pulses) were used to optimize sonication conditions. Results showed that HIU applied at low power level (75 W) was the most efficient condition in inducing palm oil crystallization at 35 °C, generating a crystalline network with higher solid fat content (SFC), higher elasticity, and sharper melting profile after 60 min of crystallization. Changes in elasticity observed as a consequence of sonication were maintained after tempering the samples at 25 °C for 24 h, but were lost after tempering at 5 °C. No significant differences (α = 0.05) were observed in SFC values of the sonicated and nonsonicated samples after tempering, whereas the sharper melting behavior observed in the sonicated sample was maintained after tempering.