Influence of Processing Conditions on the Physicochemical Properties of Complex Fat Systems

Recent Advances in Lipid Crystallization in the Food Industry

This review discusses fundamental concepts of fat crystallization and how various processing conditions such as crystallization temperature, cooling rate, and shear or agitation affect this process. Traditional methods used to process fats, such as the use of scraped surface heat exchangers, fractionation, and interesterification, are described. Parameters that affect fat crystallization in these systems, such as shear, crystallization temperature, type of fat, and type of process, are discussed. In addition, the use of minor components to induce or delay fat crystallization based on their chemical composition is presented. The use of novel technologies, such as high-intensity ultrasound, oleogelation, and high-pressure crystallization is also reviewed. In these cases, acoustic and high-pressure process parameters, the various types of oleogels, and the use of oleogelators of differing chemical compositions are discussed. The combination of all these techniques and future trends is also presented.

Effect of processing conditions as high-intensity ultrasound, agitation, and cooling temperature on the physical properties of a low saturated fat

The objective of this work was to evaluate the effect that agitation rate, crystallization temperature, and sonication have on the physical properties of a soybean-based fat with low levels of saturated fatty acids crystallized in a scraped surface heat exchanger (SSHE). The sample was crystallized at two temperatures (20 and 25 °C) and agitation rates (344/208 rpm in the barrels/pin worker-high agitation HA and 185/71 rpm barrels/pin worker-low agitation LA), and a constant flow of 11 L/hr. High-intensity ultrasound (HIU - 12.7 mm-diameter tip, 50% amplitude, 5 s pulses) was coupled to a water jacketed flow-cell and placed at three different positions within the SSHE. The combination of all those parameters affected samples' physical properties. Higher oil binding capacity (OBC) and elasticity (G') were obtained at 20 °C compared to 25 °C (77% vs. 63.78% for OBC and 30.4 kPa vs. 6 kPa for G', respectively) due to the smaller crystals formed at 20 °C. Fewer or no differences were observed due to agitation alone, but LA conditions allowed for more secondary nucleation to form due to sonication and resulted in a higher improvement on the properties of the fat. PRACTICAL APPLICATION: Fat crystallization in a scrapped surface heat exchanger (SSHE) combined with a high-intensity ultrasound (HIU) gives a realistic idea of how the HIU would work in an industrial line under continuous flow, shaved shear, and different supercooling. Results from this research will provide industry with tools on how and where to incorporate HIU in their processing line. Moreover, will give information on how to combined crystallization conditions and sonocrystallization in order to obtain improved physical properties.

Sonocrystallization as a tool to reduce oil migration by changing physical properties of a palm kernel fat

Oil migration (OM) has been an immense issue in fat-based foods such as peanut butter and chocolate fillings. The objective of this study was to evaluate the effect of high-intensity ultrasound (HIU) on OM in a palm kernel oil-based fat used in chocolate fillings, coatings, and confectionery applications. The sample was crystallized at 30 °C for 90 min and stored for 48 hr at 25 °C. HIU was applied after 20 min at 30 °C using a 3.2-mm diameter tip operating at an amplitude of 216 µm (90 W) for 10 s. OM was measured using a centrifuge- and a filter paper-based method. Crystal morphology and size, solid fat content (SFC), melting behavior, and hardness were evaluated after 90 min, 48 hr, and after OM. Results showed that HIU reduced OM (P < 0.05) by 52.0% when measured using the filter paper method while a reduction of 97.4% was observed when measured with the centrifuge method. HIU also reduced the crystal size (P < 0.05) and formed a more organized crystalline network. A reduction in peak temperature (T_p ) after 90 min of crystallization and 48 hr of storage was observed in sonicated samples without affecting the enthalpy. However, enthalpy and T_p were higher in the sample without HIU analyzed after OM due to the migration of low melting point triacylglycerols out of the crystalline network. HIU also increased the hardness (P < 0.05) from 1.37 N and 3.17 N. But no differences (P > 0.05) were found on SFC due to sonication. Overall, HIU changed the crystalline structure of the fat allowing for a better entrapment of liquid oil in the crystalline matrix. Results from this study will benefit food producers that are looking for fat sources with better capacity to entrap oil. PRACTICAL APPLICATION: OM is one of the main problems facing the fat industry, especially since the elimination of partially hydrogenated fats from foods. Efforts are being focused on finding new technologies to reduce OM and therefore to improve the shelf life of the product. This study introduces for the first time, a new processing technology to reduce OM in a palm kernel fat with high content of saturated fatty acids that is commonly used in confectionery applications.