Statistical and multivariate evaluation of olive oil degradation during long-term storage

Abstract

Extra virgin olive oil (EVOO) is valued for its flavor and health benefits. However, its quality can decline during storage, reducing food quality and the effectiveness of therapeutic compounds when used as a pharmaceutical excipient. While the oxidative stability of extra virgin olive oil has been widely studied for food quality and shelf life, its crucial role as a pharmaceutical excipient and the impact of long-term degradation on the effectiveness and stability of active compounds remain largely unexplored. This study examined 14 commercial EVOO samples immediately after opening and after three years of storage. Standard methods were used to measure the peroxide value, p-anisidine value, acidity, antioxidant activity, and extinction coefficients. The data were analyzed with statistical and chemometric tools. Initially, all oils met international quality standards. After three years, most samples showed significant deterioration, especially a decline in antioxidant activity and an increase in K232 values. Statistical tests confirmed differences among samples, and pairwise comparisons indicated significant differences consistent with degradation between T0 and T1. Principal component analysis (PCA) identified three main patterns related to oxidation and antioxidant capacity, and clustering distinguished between stable and unstable samples. Overall, the stability of the studied EVOOs varied by brand, influenced by their natural composition and storage conditions. Multivariate analysis confirmed that antioxidant activity and extinction coefficients are key indicators of oxidative degradation. This finding highlights multivariate analysis as a valuable approach for monitoring the oxidative stability of oils and ensuring EVOO quality for both food and pharmaceutical application.