Optimization of Extraction of Natural Pigment from Purple Sweet Potato by Response Surface Methodology and Its Stability

Table 2

Results of Box-Behnken of response surface methodology.

Test code	𝑋1	𝑋2	𝑋3	𝑋4	𝑌 (mg/g)
1	−1	−1	0	0	11.3175
2	−1	1	0	0	11.1425
3	1	−1	0	0	11.3365
4	1	1	0	0	11.0685
5	0	0	−1	−1	11.9935
6	0	0	−1	1	10.9165
7	0	0	1	−1	11.5735
8	0	0	1	1	11.3900
9	−1	0	0	−1	11.8120
10	−1	0	0	1	10.7630
11	1	0	0	−1	11.1080
12	1	0	0	1	11.3585
13	0	−1	−1	0	11.3780
14	0	−1	1	0	11.3700
15	0	1	−1	0	11.4760
16	0	1	1	0	11.0735
17	−1	0	−1	0	11.3995
18	−1	0	1	0	11.0815
19	1	0	−1	0	10.8575
20	1	0	1	0	11.1065
21	0	−1	0	−1	11.6355
22	0	−1	0	1	11.2575
23	0	1	0	−1	11.7305
24	0	1	0	1	11.1630
25	0	0	0	0	12.4465
26	0	0	0	0	12.4800
27	0	0	0	0	12.4800