Table 1. Codes of the independent variables and experimental design for enzymatic hydrolysis of tuna cooking juice concentrate
| Runs | Independent variables | DPPH radical scavenging activity (%) |
| Coded | Uncoded |
| X1(%) | X2(min) | X1(%) | X2(min) | Experimental | Predicted |
| 1 | 0 | 0 | 2 | 180 | 63.21 | 65.56 |
| 2 | 0 | 0 | 2 | 180 | 68.26 | 65.56 |
| 3 | 0 | 1.414 | 2 | 350 | 67.94 | 67.02 |
| 4 | –1 | –1 | 1 | 60 | 49.39 | 46.53 |
| 5 | –1 | 1 | 1 | 300 | 62.49 | 60.45 |
| 6 | 0 | –1.414 | 2 | 10.30 | 44.54 | 44.78 |
| 7 | –1.414 | 0 | 0.60 | 180 | 48.36 | 51.99 |
| 8 | 1.414 | 0 | 3.40 | 180 | 60.74 | 67.77 |
| 9 | 1 | 1 | 3 | 300 | 61.78 | 65.37 |
| 10 | 1 | –1 | 3 | 60 | 45.07 | 47.85 |
| 11 | 0 | 0 | 2 | 180 | 67.58 | 65.56 |
| 12 | 0 | 0 | 2 | 180 | 62.92 | 65.56 |
| 13 | 0 | 0 | 2 | 180 | 65.80 | 65.56 |
X1 = Alcalase concentration and X2 = hydrolysis time.
DPPH, 2,2-diphenyl-1-picrylhydrazyl.