The aim of this work was to optimize olive oil extraction, at laboratory-scale (Abencor system), from fruits of “Cobrançosa” and “Galega Vulgar” Portuguese cultivars, either in the absence or in the presence of enzymes and natural microtalc. Using a Placket–Burman design to select significant variables followed by a central composite rotatable design (CCRD), Abencor operation conditions were optimized: no water addition in 30 min malaxation and 14% w/w water addition at 50°C in centrifugation. The combined effects of the concentrations of natural microtalc (MT: 0.04–0.46 w-%) and enzyme preparation (E: 0.003–0.117 w-%) added at the beginning of malaxation, on quality criteria, total phenols and chlorophyll pigments concentrations, and on oil extraction yield, were investigated using a CCRD. The results showed that the addition of both an enzyme preparation and natural microtalc could enhance olive oil yield (up to 34% for 0.4–0.5% of microtalc and 0.1% of enzymes for “Galega Vulgar”) without any effect on quality of the obtained virgin olive oil.
Practical applications: Abencor system is the most used laboratory-scale installation in olive oil technology to carry out trials that would be very difficult to perform at industrial scale. This study presents an optimization of the Abencor extraction process, as well as the optimization of extraction with two adjuvants, enzymes and natural microtalc, using two different cultivars. The effect of E and/or MT addition depend on the cultivar. However, an improvement in extractability was always found for both cultivars. This study shows that for “Cobrançosa” olives, considering both olive oil yield and economical aspects, the chosen conditions are 0.05–0.15% of microtalc in the absence of added enzymes. For “Galegar Vulgar” olives, the highest extractability is observed under the presence of enzyme preparation amount higher than 0.10% and microtalc amount of 0.4–0.5%.
The simultaneous addition of an enzyme preparation and natural microtalc could enhance olive oil yield. The use of adjuvants, and their respective amounts, must be adjusted to each cultivar.