Measuring Primary Lipid Oxidation in Food Products Enriched with Colored Microalgae

Microalgae are a valuable alternative source of n-3 LC-PUFA and have already proven their potential in different food products. However, enrichment of food products with n-3 LC-PUFA implies an increased sensitivity to lipid oxidation. Numerous analytical techniques have already been developed to determine and follow lipid oxidation. Photoautotrophic microalgae often contain, besides n-3 LC-PUFA, other compounds like carotenoids and chlorophylls. These colored compounds may interfere with the standard analytical techniques. This study contributes to optimize a simple and low-cost method to measure the degree of primary lipid oxidation in food products enriched with photoautotrophic microalgae. The standard iodometric titration and three spectrophotometric methods (FOX, IDF, and CD & CT) were investigated. The FOX method was selected as the preferable method, although interference due to the presence of metal ions could occur. This could partially be solved by a supplemental step with TPP addition. However, as this additional step did not change the trend in oxidative values during storage, it was suggested to normalize the values of the FOX method to week zero to investigate the trend of oxidation during storage of products enriched with photoautotrophic microalgae.