EXPERIMENTAL RESEARCHES ON THE DOUBLE MIL LING OIL EXTRACTION METHOD FROM OLIVES BY PERCOLATION-CENTRIFUGATION SYSTEM

The Authors carried out extraction experiments on oil from olives by t he percolation-centrifugation system, comparing a single milling with a double one, carried out by hammer crusher and combined hammer crushe r-grindstone milling, respectively. ''Leccino'', ''Coratina'' and ''Dr itta'' olive varieties were processed. The research results showed tha t double milling industrial outputs were significantly higher. This ph enomenon was confirmed by the lower quantity of total oil found in the two by- products (husk and vegetation water). Such phenomenon was als o confirmed by the higher P/S and FSf/CSf ratios ascertained on the so lid by-product and also by the lower content of dry residue as well as by the lower average turbidity values in the effluent. Besides, with double milling, oils of better quality (richer in poliphenols and o-di phenols, less susceptible to oxidization, with better sensorial charac teristics and with higher values of the global indices of quality), we re obtained with greater frequency. Therefore, the use of the hammer c rusher-grindstone mill binomial appeared technically advantageous in t he industrial processing of the olives. The economic advantage, howeve r, subsists only if the value of the increase in qualitative-quantitat ive output is greater than the cost of carrying out a second milling.