Table 1.

Coded levels and actual values (in parentheses) of the variables in Box–Behnken design: extraction time (X₁, min); temperature (X₂, °C); pH (X₃); pectin yield (PY, %); degree of esterification (DE, %)

Run	Independent variables			Measured responses		Predicted responses
	X1	X2	X3	PY	DE	PY	DE
1	− 1 (30)	− 1 (75)	0 (2.25)	9.20	61.23	9.09	60.15
2	+ 1 (90)	− 1 (75)	0 (2.25)	12.76	54.92	12.67	54.39
3	− 1 (30)	+ 1 (95)	0 (2.25)	13.75	50.05	13.83	50.58
4	+ 1 (90)	+ 1 (95)	0 (2.25)	14.34	48.27	14.45	49.35
5	− 1 (30)	0 (85)	− 1 (1.50)	22.26	45.83	22.14	45.93
6	+ 1 (90)	0 (85)	− 1 (1.50)	25.98	45.88	25.84	45.43
7	− 1 (30)	0 (85)	+ 1 (3.00)	7.03	69.48	7.17	69.92
8	+ 1 (90)	0 (85)	+ 1 (3.00)	7.55	63.54	7.67	63.43
9	0 (60)	− 1 (75)	− 1 (1.50)	20.41	45.11	20.64	46.08
10	0 (60)	+ 1 (95)	− 1 (1.50)	27.95	44.10	28.00	43.47
11	0 (60)	− 1 (75)	+ 1 (3.00)	8.20	71.15	8.16	71.78
12	0 (60)	+ 1 (95)	+ 1 (3.00)	7.56	60.76	7.33	59.78
13	0 (60)	0 (85)	0 (2.25)	11.02	58.57	10.62	58.54
14	0 (60)	0 (85)	0 (2.25)	10.65	58.03	10.62	58.54
15	0 (60)	0 (85)	0 (2.25)	10.20	59.01	10.62	58.54