Experimental Trials to Optimize the use of Physical Coadjuvants in Olive Oil Extraction 
Francesco Caponio, Giacomo Squeo, Roccangelo Silletti, Vito Michele Paradiso, Carmine Summo, Antonella Pasqualone, Tommaso Gomes
Università degli Studi di Bari Aldo Moro, Dipartimento di Scienze del Suolo, della Pianta e degli Alimenti, Bari, Italy
 
It is well known that a fraction of the oil located into the vacuoles of olive pulp cells is not recovered during the extractive process. In fact, it remains inside intact drupe cells, or is retained by the olive paste colloidal system as microgel, or remains emulsified with the water phase. The difﬁculty of freeing this ‘bound’ oil, more evident for the so-called ‘difficult olive pastes’, lies mainly in the fact that the droplets of dispersed or emulsified oil are surrounded by a lipoprotein membrane (phospholipids and proteins) that keeps them in that state.
To improve oil yield, several researches have been carried out in order to evaluate the effects of technological coadjuvants with exclusive physical action (salt, talc, and calcium carbonate) which, added at the malaxation step, help to break down water-oil emulsions and consequently make oil extraction easier. The use of coadjuvants in olive oil extraction has progressively increased in the last years. Calcium carbonate is the most diffused, mainly due to the its low cost.
Coratina, that is one of the most diffused Italian cultivars, gives a difficult paste because it has a rather low ripening index at the time of processing. The aim of this research has been to point out the efficacy of physical coadjuvants in the oil extraction process from Coratina olives, also considering batches of olives having different ripening indices. 
The results, obtained using two different particle size distribution of calcium carbonate, evidenced an increase of extraction yield respect to control in every trial. A minor effect of particle size was observed, whereas a significant difference was observed as a function of the ripening index and of the amount of coadjuvant added. The analytical results, regarding both chemical and sensory parameters, evidenced only a slight influence of calcium carbonate on the quality of the extracted oils.