Table 5.

Response surface experimental design and results

Run	Solid–liquid ratio (g/ml)	Ethanol (%)	Time (min)	pH	Anthocyanins yield (mg/g)
1	−1	1	0	−1	2.70
2	−1	0	0	1	2.69
3	−1	0	0	1	2.61
4	1	0	0	0	4.89
5	−1	0	−1	1	2.52
6	1	0	−1	0	4.78
7	−1	0	1	0	2.69
8	0	0	−1	−1	4.94
9	0	0	−1	0	4.79
10	0	1	−1	1	3.47
11	0	1	1	−1	3.79
12	0	1	0	0	4.51
13	0	1	0	0	4.45
14	1	1	0	0	4.91
15	0	0	1	0	4.07
16	0	−1	−1	0	4.12
17	0	−1	1	−1	4.49
18	0	−1	0	−1	4.02
19	0	−1	0	0	4.11
20	0	0	0	0	5.69
21	0	0	0	0	5.59
22	0	0	0	0	5.59
23	0	0	0	0	5.87
24	−1	−1	0	0	3.46
25	1	−1	0	0	5.17
26	0	0	1	0	4.71
27	1	0	0	1	4.39
28	1	0	1	−1	4.46
29	0	0	0	1	5.16