Cooking with extra-virgin olive oila study to mantain its health properties

Resumen

Extra-virgin olive oil (EVOO) is widely consumed raw and cooked, due its flavor and its proven health benefits. However, cooking changes EVOO composition, diminishing these health effects. In this thesis, the effect of cooking on EVOO, how its minor and major fraction are modified, and how those changes may affect human health have been studied. For that, the experimental part of thesis has been divided in four main sections. First, an analytical method using mass spectrometry in tandem was developed and validated for the quantification of the four main secoiridoids: oleocanthal, oleacein, oleuropein aglycone and ligstroside aglycone. With this method, the changes in the phenolic profile that may affect EVOO could be quantified. Second, the effect of a domestic sautéing process, the most used technique in the Mediterranean countries, was assessed on the phenolic profile. The effect of the cooking temperature and time was determined. The temperature has a marked effect, while time had no significant effect on the sum of phenolic compounds and it had an effect just on few individual compounds. ortho-Diphenols degraded more easily than single phenols. The cooking process produced some degradation products, such as hydroxyelenolic acid. Finally, EVOO cooked at moderate temperature (120ºC) still meets the criteria for the European health claim that “Olive oil polyphenols contribute to the protection of blood lipids from oxidative stress”. Third, the effect of different cooking techniques was assessed. Three traditional techniques (oven, deep-frying and sautéing) and three innovative techniques (slowcooker, low temperature cooking and vacuum pot cooking) were investigated. EVOO cooked with the more innovative techniques was less degraded and transformed than the cooked with the more traditional techniques. Between the more traditional techniques, sautéing samples presented a different phenolic and lipidomic profile than the other two types of samples. Phenolic compounds are affected by temperature and oxygen availability, while the lipidic compounds are mainly affected by temperature, regardless of the oxygen availability. Cooking time seems to have no effect on both profiles. Several compounds were tentatively identified, from triglycerides degradation products to phenolic compounds. Fourth and last, the effect of the differently cooked EVOO on Caco-2 cell has been investigated. For this, a representative sample of each cluster found (raw, low temperature cooked using a Roner® apparatus, deep-frying and sautéing) in the previous work was digested, and Caco-2 cells were incubated with this digestion product. Then highresolution mass spectrometry lipidomic analysis of the cell lysates was carried out and using multivariate statistics the samples were compared. Surprisingly, the cells did not respond as the oils, Roner® samples were differentiated from the raw and sautéing samples, which behaved similarly. While deep-frying samples were in the middle. Roner® cell samples presented up-accumulation of ceramides, dyglycerides and oxidized lipidic compounds; and they also showed a down-accumulation of amino acids and derivatives, suggesting the presence of redox-mediated cell stress