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.