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Chemometrical optimization and fast determination of debittering of table olives by means of capillary electrophoresis

Table olives require a thorough process of debittering in order to achieve the organoleptic quality of olives before consumption. Several chromatographic analytical methods have been used in order to ascertain the debittering process. Capillary electrophoresis (CE) offers several advantages to the determination of the bitter responsible compound oleuropein in table olives, such as speed, reduced amount of solvents and reagents (green chemistry), small amount of sample, high efficiency and lower costs. Despite the evident advantages of CE, this technique has not been used so far for the verification of the debittering of table olives.
Our objective was to extract oleuropein from table olives and optimize the analysis via CE using a design of experiments.
Soluble biophenols, oleuropein among them, were extracted using sequential liquid partition methods with methanol:acetone and hexane from table olives as previously described (1). Finally the samples in methanol were transferred to vials. CE was run in a P/ACE System using an uncoated fused-silica capillary (50 m ID x 375 m OD, 50 cm length). UV detection performed at 214 nm in cationic mode with pressure injection for 7 s.
The optimization was accomplished by means of a central composite design using as response the resolution between oleuropein and its nearest peak. A preliminary experiment screened the appropriate parameters that required further optimization. The factors for the central composite design were: separation buffer pH, voltage and buffer composition. The best separation was achieved at 21ºC, voltage 10 kV, and 20 mM tetraborate in 20 mM phosphate buffer at pH 10.0.