Table 1.

Factors and levels in the response surface design used for the optimization of ovalbumin (OVA) extraction by an aqueous two-phase system (ATPS).

Variables	Coded Variable Levels
	−1	0	1
X1 PEG1000 (w/w)%	18	20	22
X2(NH4)2SO4 (w/w)%	14	16	18
X3 pH	8	9	10
X4 Salt egg white solution/g	0.5	1	1.5