Independent variables
Range and level coded value (xi)
-α
-1
0
+1
+α
X
1
: initial soluble starch (g L
-1
)
6.95
8
10
12
13.05
X
2
: initial ferrous iron (mg L
-1
)
73.77
100
150
200
226.23
X
3
: initial L-cysteine (mg L
-1
)
247.54
300
400
500
552.46
Table 1:
Experimental range and levels of the independent variables.
