Physical Properties of Monoglycerides Oleogels Modified by Concentration, Cooling Rate, and High‐Intensity Ultrasound

Abstract

The aim of this study was to investigate the effects of monoglycerides (MG) concentration (3, 4.5, and 6 wt%), cooling rate (0.1 and 10 °C/min), and high‐intensity ultrasound (HIU) application on physical properties of oleogels from MG and high oleic sunflower oil. Microstructure, melting profile, elasticity (G′), and solid fat content (SFC) were measured immediately after preparation of samples (t = 0) and after 24 hr of storage at 25 °C. Samples’ textural properties (hardness, adhesiveness, and cohesiveness) and oil binding capacity (OBC) were evaluated after 24 hr at 25 °C. In general, samples became less elastic over time. Slow cooling rate resulted in lower G′ after 24 hr compared to the ones obtained using 10 °C/min. Network OBC was improved by increasing MG concentration and cooling rate, and by applying HIU. After storage, oleogel melting enthalpy increased with MG concentration. In general, this behavior was not correlated with an increase in SFC. An improvement in the network structure was generally reached with the increase in cooling rate, according to texture and rheology results, for both sonicated and nonsonicated conditions. At the highest MG concentration, HIU application was more efficient at increasing OBC and hardness of the network at 0.1 °C/min. Microscopy images showed that the oleogels microstructure was changed as a consequence of HIU application and cooling rate, evidencing smaller crystals both in sonicated and faster cooled samples. Obtained results demonstrate that cooling rate, MG concentration, and HIU can be used satisfactorily to tailor physical properties of MG oleogels. Practical Application Oleogels have been studied in the last years as semisolid fat replacers in food products. Cooling rate is an important processing parameter in the oleogel preparation because it affects their final physical properties, while high‐intensity ultrasound (HIU) is a relatively novel technique to tailor lipid properties. This study is focused on the application of a slow/fast cooling rate in combination with/without HIU treatment at different monoglycerides and high oleic sunflower oil mixtures as a successful strategy to obtain oleogels with different physical properties and with potential applications in the food industry, such as fat substitutes in bakery.

Controlling oleogel crystallization using ultrasonic standing waves

“…Therefore, during crystallization, the forces acting on monoglyceride crystals increase and speed up the translation of the crystals to the nodal plane. Additionally, a fast cooling rate produces a high number of nucleation points, leading to a high number of small microcrystals with respect to the case where one applies a slow cooling rate 15,19,38 . In our case, possible differences in microcrystal dimensions 38 did not modify the final outcome, proving that USSWs can be applied as a robust method when employing commonly used cooling rates for oleogel preparation 15,17,19,38,39 .…”

“…10% monoglyceride treated at 1 MHz, 20% monoglyceride treated at 1 MHz and 2 MHz and all samples containing candelilla wax treated at 1 MHz and 2 MHz). This is because of some limitations of our current setup, the tightly packed crystal network formed in candelilla wax oleogels compared to sunflower wax oleogels 43 and the dense network of oleogels containing high concentrations of monoglycerides 38,41 . However, during crystallization we also observed the formation of bands in the latter samples (Fig.…”

“…Different concentrations and types of oleogelators modify the crystalline network density and oleogelator platelet dimensions 15,38,43 . For instance, candelilla wax forms a densely packed crystalline network composed of small oleogelator microcrystals compared to the less densely packed network formed by the bigger sunflower wax microcrystals 43 .…”

Effect of high‐intensity ultrasound on the oleogelation and physical properties of high melting point monoglycerides and triglycerides oleogels

“…Multicomponent systems are formed by the combination of two or more high or low structuration power oleogelators or by an oleogelator and an additive that can modify the properties of the gel, like a high‐sat fat, tri‐saturated triacylglycerols to name a few (Buerkle & Rowan, 2012). Additionally to the multicomponent systems, the combination of oleogelation with other physical processing techniques such as drying/foams (Patel et al., 2014) or high intensity ultrasound (HIU) (da Silva, Arellano, & Martini, 2019b; Giacomozzi, Palla, Carr, & Martini, 2019; Sharifi, Goli, & Fayaz, 2019) can be viewed as alternative routes to improve oleogelation. Previous studies have improved oleogelation, emulsification, and solubility of structured components as proteins (Lee et al., 2016; Paglarini, Martini, & Pollonio, 2019; Yildiz, Andrade, Engeseth, & Feng, 2017), MG (Giacomozzi et al., 2019; Giacomozzi, Palla, Ca, & Martini, 2020), and waxes (da Silva et al, 2019b; Martini, Carelli, & Lee, 2008; Sharifi et al., 2019) to form oleogels, emulsion gels, and nanoemulsions as a healthy alternative for food application.…”

“…Additionally to the multicomponent systems, the combination of oleogelation with other physical processing techniques such as drying/foams (Patel et al., 2014) or high intensity ultrasound (HIU) (da Silva, Arellano, & Martini, 2019b; Giacomozzi, Palla, Carr, & Martini, 2019; Sharifi, Goli, & Fayaz, 2019) can be viewed as alternative routes to improve oleogelation. Previous studies have improved oleogelation, emulsification, and solubility of structured components as proteins (Lee et al., 2016; Paglarini, Martini, & Pollonio, 2019; Yildiz, Andrade, Engeseth, & Feng, 2017), MG (Giacomozzi et al., 2019; Giacomozzi, Palla, Ca, & Martini, 2020), and waxes (da Silva et al, 2019b; Martini, Carelli, & Lee, 2008; Sharifi et al., 2019) to form oleogels, emulsion gels, and nanoemulsions as a healthy alternative for food application. In oleogels, the effect of sonication on physical properties can be attributed to the cavitation generated by the HIU, this cavitation creates bubbles that can either collapse or dissolve forming localized temperature and pressure zones that can act as nuclei and induce crystallization and structuration of the crystalline network (Higaki, Ueno, Koyano, & Sato, 2001).…”