Optimized Conditions for Flavonoid Extraction from Pomelo Peel Byproducts under Enzyme- and Ultrasound-Assisted Extraction Using Response Surface Methodology

Table 4

ANOVA for response surface quadratic model analysis of the experimental results¹.

Source	Sum of squares	Df	Mean square	F-value	value
Model	21.72	14	1.55	41.78	<0.0001
X1	0.9974	1	0.9974	26.86	0.0001
X2	0.6193	1	0.6193	16.68	0.0011
X3	0.3024	1	0.3024	8.14	0.0128
X4	0.4562	1	0.4562	12.29	0.0035
X1X2	0.3299	1	0.3299	8.88	0.0099
X1X3	0.2157	1	0.2157	5.81	0.0303
X1X4	0.0008	1	0.0008	0.0225	0.8829
X2X3	1.95	1	1.95	52.59	<0.0001
X2X4	0.1861	1	0.1861	5.01	0.0420
X3X4	0.5911	1	0.5911	15.92	0.0013
X1^2	14.51	1	14.51	390.72	<0.0001
X2^2	1.50	1	1.50	40.27	<0.0001
X3^2	3.59	1	3.59	96.67	<0.0001
X4^2	0.6546	1	0.6546	17.63	0.0009
Residual	0.5198	14	0.0371
Lack of fit	0.3765	10	0.0376	1.05	0.5260
Pure error	0.1433	4	0.0358
Cor total	22.24	28
R^2	0.9766
Adjusted R^2	0.9532
Predicted R^2	0.8924
Adeq precision	20.0476
C.V. %	2.02

X₁: liquid-to-solid ratio (mL/g); X₂: enzyme concentration (%, v/m); X₃: incubation time (min); and X₄: ultrasonic time (min).