Table 1.

Independent variables (factors) of the response surface central composite design.

Factor A Temperature (°C)	Factor B Time (Days)	Experiments (Codes)
12.1	3.58	1
13.2	1.60	2
13.2	5.52	3
16.0	0.81	4
16.0	3.48	5*
16.0	6.19	6
18.8	1.60	7
18.8	5.52	8
19.9	3.60	9

*Center point. Three replicate experiments were performed for the center point.