Table 1 Levels and target values of variables in Box-Behnken design

	Independent variable	Symbol	Level
			-1	0	1
			Formulation	Water	X1	25	30	35
variable	Yeast	X2	1	2	3
Process variable	Fermentation time	X3	30	45	60
	Dependent variable	Symbol	Lower value	Target value	Upper value
	Hardness	Y1	60	70	80
	Cohesiveness	Y2	1	2.5	3
	Springiness	Y3	1	1.25	1.5