Effect of ripening and olive cold storage on oil yield and some olive oil characteristics

Systems increasing the processing capacity are of special interest in the olive oil production. Additionally, virgin olive oil quality is directly related to the physiological stage of the fruit when processed. This paper reports how the duration (0, 1, 2, 3 and 4 weeks) of cold storage (5 +/- 1 degrees C) of olive fruits affects oil yield, some quality parameters (free acidity, peroxide value, (K232 and K270)) and phenol content of oil ('Picual olives) according to the stage of ripeness of the fruits (green mature, veraison and black). Results showed that when the stage of ripeness was green, the value of free acidity of the oil was maintained below 0.8% for 4 weeks of cold storage, whereas this level was exceeded within 4 and 3 weeks, for veraison and black olives respectively. A significant decrease in the total phenol content in olives was revealed after the second week of cold storage for the three stages of ripeness. These results suggest that even if the free acidity stays at low levels in olive oil extracted from green mature olives stored in refrigeration for 4 weeks, a decrease in phenol content of olives after 2 weeks could limit the duration of storage at 5 +/- 1 degrees C for the three stages of ripening.