Influence of Free and Microencapsulated Extracts from Onion Peels on the Performance of Fortified Fresh Cheese

As a strategy to valorise onion peel (OP), a phenolic-rich extract was obtained and microencapsulated using the double emulsion technique for improved stability. Both free and microencapsulated OP extracts were added to fresh cheese to enhance its nutritional composition. The extract exhibited a high total phenolic content (TPC) and strong antioxidant capacity towards ABTS and DPPH radicals, with IC₅₀ of 9.5 and 36.1 mg_Extract∙L^-1, respectively. The extract demonstrated inhibitory capacities of 71% against α-amylase and 82% towards β-glucosidase. Quercetin was identified as the main phenolic compound, while potassium was the predominant mineral. The microencapsulation yielded an encapsulation efficiency of 91%, with an average particle size of 17.9 µm. Incorporating free and microencapsulated OP extract into the fresh cheese reduced syneresis, a favourable outcome, while preserving moisture levels, protein and ash content, and the pH. The incorporation of the free and microencapsulated OP extract enhanced the TPC and DPPH scavenging capacity of the cheeses. Results demonstrated the potential of using OP extract to enhance the antioxidant properties of fresh cheese, and to reduce syneresis, while promoting sustainability. These outcomes are particularly relevant from an industrial point of view, since an increase in antioxidant content might contribute to extending the product shelf-life.