Design of emulsion gels structured with freeze-dried and extruded citrus pomace for functional and sustainable applications

Solid fats, rich in saturated fatty acids, are common in the food industry as they are responsible for many food attributes, such as texture, flavor, and stability. However, their consumption is associated with an increased risk of cardiovascular diseases, obesity, and type II diabetes. Structuring liquid oils, which are rich in unsaturated fatty acids, into emulsion gels with the consistency and stability of solid fats presents a healthier alternative. Previous studies have explored using clementine pomace as a stabilizing agent to prepare low-viscosity emulsions. Physical treatments like freeze-drying and extrusion could modify the structuring properties of pomace, enabling its use for preparing emulsion gels while supporting clean labeling and increasing the content of bioactive compounds in the food product. The main objective of this work is to develop stable and sustainable emulsion gels using freeze-dried and extruded clementine pomace as structuring agent.

Emulsion gels structured with freeze-dried or extruded clementine pomace were prepared with 5 or 6% pomace and 40 or 50% oil. The content of bioactive compounds (carotenoids and phenolic compounds), microstructure (CLSM), and physical stability (after centrifugation) were studied.

The emulsion gels structured with freeze-dried pomace showed the highest carotenoid content, while those structured with extruded bagasse exhibited the highest phenolic compound content. The microstructure analysis revealed that emulsions structured with freeze-dried pomace featured smaller, uniformly dispersed fat globules within a continuous phase. In contrast, emulsion gels structured with extruded clementine pomace exhibited greater coalescence and a higher proportion of free fat. In terms of physical stability, the most stable emulsion gels were those structured with freeze-dried clementine pomace, regardless of the pomace and oil percentages.

Freeze-dried clementine pomace allows for the production of emulsion gels rich in bioactive compounds, offering a healthy alternative to solid fats. This innovative approach could have interesting applications in formulating clean-label foods.