Table 1 The range and levels of the variables
Variable | Symbol | Unit | Range and level of actual and coded values | ||||
|---|---|---|---|---|---|---|---|
− 2 | − 1 | 0 | 1 | 2 | |||
pH value | A | – | 3.5 | 4.5 | 5.5 | 6.5 | 7.5 |
Mannose | B | (g/L) | 5.0 | 7.5 | 10.0 | 12.5 | 15 |
Meat extract | C | (g/L) | 2.5 | 5.0 | 7.5 | 10.0 | 12.5 |
Incubation time | D | (day) | 3 | 4 | 5 | 6 | 7 |