Darkening of brined olives by rapid alkaline oxidation

Abstract

Alkaline oxidation of olives called Californian process is a recommended method of the International Olive Oil Council that generally uses three to five lye treatments. The present investigation was carried out to reduce the number of lye treatments to one and consequently minimize the process duration to about 24 h, preventing the health hazards and environmental pollution. Results revealed that no significant differences were noted between the two cultivars used in this study (Gordal and Ladoelia) in response to ferrous gluconate concentration. Ferrous gluconate (0.4%) should be added during the fixation to stabilize the color produced during air injection. Optimum fixation time was 8 and 12 h for Ladoelia and Gordal cultivars, respectively. When the oxidized black olives were stored in hermetically sealed containers for 4 months in slight brine at different pH values, results revealed that pH 5 was more suitable for maintaining color intensity and firmness of the olives. PRACTICAL APPLICATIONS The black oxidizing or Californian processing is one of the three main methods of preparing table olives. In the traditional Californian process, three to five lye treatments are generally used, and when applying this technique on some cultivars stored in brine for more than 6 months, the color cannot be stained enough and fruit firmness becomes softer. Moreover, the duration of the process is long (72-80 h) and the final product is easy to deteriorate. The main goal of this investigation was to modify the Californian process to minimize processing period and improve quality attributes of the obtained olives by using oxidation with one-lye treatment. The results obtained from this study could help table olive industries to design new processes or change the already existing ones in order to improve product quality and make it more competitive in the international market. © 2008 The Author(s).