Table 3.
Effect of the pH of the aqueous phase on the recovery of different substances.
| pH of Aqueous Phase | Extract (g/kg d.w.) | Sugars (g/kg d.w.) | TPC (g/kg d.w.) | Hydroxytyrosol (g/kg d.w.) | Hydroxytyrosol in Extract (%) |
|---|---|---|---|---|---|
| 1 | 51.07 ± 7.70 | 4.01 ± 0.64 | 19.86 ± 3.46 | 2.33 ± 0.03 | 4.57 ± 0.75 |
| 2 | 44.07 ± 5.23 | 4.01 ± 0.22 | 17.72 ± 3.46 | 2.45 ± 0.23 | 5.56 ± 1.18 |
| 4 | 36.08 ± 5.78 | 3.91 ± 0.05 | 17.50 ± 3.61 | 2.67 ± 0.18 | 7.40 ± 1.70 |
| 6 | 17.44 ± 3.82 | 1.74 ± 0.65 | 10.36 ± 4.15 | 2.35 ± 0.29 | 13.48 ± 4.64 |
| 8 | 11.17 ± 1.36 | 2.07 ± 0.40 | 8.92 ± 1.78 | 2.60 ± 0.11 | 23.23 ± 3.83 |
| 9 | 9.08 ± 0.86 | 1.34 ± 0.37 | 5.40 ± 0.52 | 2.26 ± 0.08 | 24.84 ± 3.30 |
| 10 | 6.10 ± 0.16 | 1.39 ± 0.09 | 3.64 ± 0.05 | 1.36 ± 0.02 | 22.33 ± 0.93 |
| 11 | 3.61 ± 0.04 | 1.62 ± 0.05 | 2.00 ± 0.21 | 0.38 ± 0.12 | 10.40 ± 3.57 |
| 12 | 2.42 ± 0.39 | ND * | 0.56 | ND * | ND * |
Experimental conditions: solid–liquid extraction performed with 3 M HCl(aq.) for 20 min; pH adjusted with NaOH(aq.); liquid–liquid extraction performed 3 times with ethyl acetate; organic phase washed two times with saturated NaCl; ethyl acetate evaporated under vacuum. Errors represented as standard deviation; * not detected.