Effect of filtration on virgin olive oil stability during storage

The effect of filtration and dehydration on the stability and quality of virgin olive oil during storage at room temperature (25°C) and under accelerated conditions (40°C) was studied. Different types of monovarietal olive oil, namely unfiltered (UF), filtered (F) and filtered-dehydrated (FD), were obtained from Arbequina, Colombaia, Cornicabra, Picual and Taggiasca cultivars. Results showed that filtration and dehydration decreased the rate of hydrolysis of the triacylglycerol matrix, especially at the higher temperature and in oils with a higher initial free acidity (e.g. free acidity of 0.82% and 0.63% in UF and FD Colombaia samples, respectively, after 8 months of storage), and delayed the appearance of rancid defects (e.g. UF and FD Arbequina samples lost extra-virgin grade after 10 and 12 months of storage, respectively). The formation of simple phenols due to the hydrolysis rate of their secoiridoid derivatives was also greater in unfiltered olive oils (e.g. 174 mmol/kg and 137 mmol/kg in UF and FD Picual samples, respectively, after 8 months of storage). Thus, filtration and especially dehydration could help to prolong the shelf life of high-quality and less stable olive oils like those obtained from the Arbequina and Colombaia varieties.