Turbidity of extra virgin olive oil: characterization and its effect on product quality during processing and distribution

The literature study on veiled extra virgin olive oils (VEVOO), and on the role of turbidity on olive oil quality, showed that the results obtained by different researchers were contradictory. Some authors have demonstrated that VEVOO were more stabile during storage than filtered extra virgin olive oils (FEVOO); on the contrary, other authors have demonstrated the opposite effect. The non-unanimity of results, and the increasing interest in consumer and producers for VEVOO, has led to a step-by-step study on extra virgin olive oil turbidity and its role on quality during processing and distribution. The general scope of the thesis can be split into four specific aims, which have driven four works carried out, and published, during the PhD: 1) In literature, there are no works that speak about different turbidities. Olive oil studies always report a comparison between FEVOO and VEVOO, considering turbidity as a dichotomous variable. Therefore, the first aim of PhD was to find what characterize olive oil turbidity the most and if all VEVOO are the same. 2) After a first characterization of a wide spectrum of turbidities, which have different water content and microbial contamination, a targeted study on the role of water and microorganism was carried out. The aim of this work was to understand what effects are strictly connected with water content, what effects depends on microbial contamination, and what effects are due to the joint present of water and microorganisms. 3) Since the development of “fusty” sensory defect, and the hydrolysis of phenolic compounds are phenomena always present in analyzed VEVOO, the third aim of the PhD thesis was to define how fast these degradative phenomena are, in order to indicate a filtration scheduling. 4) The last aim of this PhD thesis was to do a focused work on the effects of different “turbidities”, in term of water and insoluble solids content, and microbial contamination, both together and separately, on VEVOO quality during a longer storage.