This study investigated the effect of varying proportions of rapeseed, avocado, and walnut oils on the oxidative stability of ternary lipid blends. A centroid simplex mixture design was applied, with oil fractions constrained to 100%. Oxidative quality was assessed using peroxide value (PV), acid value (AV), anisidine value (AnV), and the total oxidation index (Totox). Additionally, natural pigments, carotenoids, and chlorophylls were analyzed as response variables.

The findings showed that increasing walnut oil content above 7% markedly raised Totox, indicating enhanced susceptibility to oxidative degradation. In contrast, blends containing at least 72% rapeseed oil and 21–22% avocado oil, with a maximum of 6% walnut oil, demonstrated the lowest Totox values, reflecting the highest oxidative stability. This suggests a synergistic interaction between rapeseed and avocado oils, reducing both primary (PV) and secondary (AnV) oxidation.

The inclusion of carotenoids and chlorophylls as output variables highlighted their role as natural antioxidants, though their stability was strongly influenced by oil composition. Overall, the study confirms that mixture design methodology provides an effective framework for optimizing lipid systems and identifying interactions between components.

These results emphasize the potential of carefully balanced oil blends to achieve improved oxidative resistance and pigment stability. Such formulations may contribute to the development of functional fats and oils with superior nutritional quality and extended shelf life, supporting their application in the food industry.