Table 1.
Box–Behnken experimental design (BBD), coded levels, and actual values (in parentheses) of the variables: Extraction temperature (X1, °C); time (X2, min); pH (X3). The responses considered were the yield (Y), degree of esterification (DE), anhydrouronic acid content (AUA) and methoxyl content (MeO).
| Independent Variables | Experimental Values | ||||||
|---|---|---|---|---|---|---|---|
| Run | X1 (°C) | X2 (min) | X3 (pH) | Y (%) | DE (%) | AUA (%) | MeO (%) |
| 1 | −1 (70) | 0 (60) | −1 (1) | 6.88 | 65.47 | 59.54 | 6.87 |
| 2 | +1 (95) | −1 (30) | 0 (2) | 10.72 | 75.30 | 56.92 | 7.55 |
| 3 | −1 (70) | +1 (90) | 0 (2) | 7.55 | 76.65 | 55.56 | 7.51 |
| 4 | 0 (82.5) | −1 (30) | +1 (3) | 2.45 | 87.28 | 43.22 | 6.66 |
| 5 | +1 (95) | 0 (60) | −1 (1) | 9.95 | 52.48 | 69.08 | 6.39 |
| 6 | −1 (70) | 0 (60) | +1 (3) | 2.03 | 81.04 | 33.48 | 4.78 |
| 7 | 0 (82.5) | −1 (30) | −1 (1) | 8.50 | 62.97 | 66.96 | 7.43 |
| 8 | +1 (95) | 0 (60) | +1 (3) | 4.44 | 88.25 | 49.70 | 7.73 |
| 9 | +1 (95) | +1 (90) | 0 (2) | 12.19 | 76.08 | 57.29 | 7.68 |
| 10 | 0 (82.5) | +1 (90) | −1 (1) | 10.81 | 58.98 | 66.44 | 6.90 |
| 11 | −1 (70) | −1 (30) | 0 (2) | 6.92 | 76.85 | 53.60 | 7.26 |
| 12 | 0 (82.5) | +1 (90) | +1 (3) | 3.44 | 89.05 | 47.91 | 7.03 |
| 13 | 0 (82.5) | 0 (60) | 0 (2) | 8.61 | 78.52 | 61.32 | 8.48 |
| 14 | 0 (82.5) | 0 (60) | 0 (2) | 8.04 | 80.88 | 63.16 | 9.00 |
| 15 | 0 (82.5) | 0 (60) | 0 (2) | 7.80 | 80.83 | 54.85 | 7.80 |
| OP | 95 | 90 | 1.36 | 13.4 | 61.62 | 66.42 | 6.76 |
| AP | - | - | - | - | 77.18 | 62.17 | 9.00 |
| CP | - | - | - | - | 55.19 | 69.62 | 6.78 |
Y: yield; DE: degree of esterification; MeO: methoxyl content; AUA: anhydrouronic acid content.