Table 1.

Code and levels of variables chosen for the trails

Factors	Symbols		Levelsa
	Coded	Uncoded	−1	0	+1
Peppermint extract (μg/g cheese)	x 1	X1	220	440	660
Starter (g/100 Kg retentate)	x 2	X2	1.30	2.00	2.70
Rennet (g/100 Kg retentate)	x 3	X3	1.30	1.90	2.50
Ripening time (day)	x 4	X4	10	30	50

^a x ₁  = (X ₁ -440)/220; x ₂  = (X ₂ -2.00)/0.70; x ₃  = (X ₃ -1.90)/0.60; x ₄  = (X ₄ -30)/20