Functional dairy products are usually fortified or enriched with unsaturated lipids of known positive health effects, mainly in prevention of cardiovascular diseases and cancer. The main lipids used are omega-3 long-chain polyunsaturated fatty acids, conjugated linoleic acid and phytosterols. Lipid oxidation can occur during processing and storage of functional dairy products enriched with such unsaturated lipids and results in formation of undesirable offflavours and unhealthy compounds. This review highlights the importance of studying oxidative stability of functional dairy products in order to ensure the integrity of the original lipids and hence guarantee the quality and safety of functional dairy products. A survey of the recent literature shows that there is still scarce information on lipid oxidation in functional dairy products, in part due to its complexity in these multiphase food systems. Experimental protocols of most of the studies found start from enrichment of plain milk or dairy products with functional lipids, and examine oxidation along storage. Particular emphasis is placed in this review on discussion of the methods used for evaluation of oxidation. Among them, sensory evaluation is essential to ensure consumer acceptance, while quantitative analysis of non-volatile lipid oxidation compounds and antioxidants stand out as the most adequate methods to determine the lipid oxidation state in functional dairy products.
Keywords: Lipid oxidation, functional dairy products, omega-3 fatty acids, conjugated linoleic acid (CLA), phytosterols