Table 1.

Experimental domains and codification of the independent variables in the factorial rotatable designs performed to optimize the enzyme hydrolysis of cartilage and the chemical treatments of the hydrolysates using alkaline or alkaline-hydroalcoholic solutions.

Coded Values	Natural Values
	Enzyme Hydrolysis		NaOH Treatment		NaOH-EtOH Treatment
	pH	T (°C)	NaOH (M)	Time (h): t	NaOH (M)	Ethanol (v)
−1.41	6.0	30.0	0.20	1.0	0.10	0.30
−1	6.6	37.3	0.39	4.4	0.20	0.46
0	8.0	55.0	0.85	12.5	0.45	0.85
+1	9.4	72.7	1.31	20.6	0.70	1.24
+1.41	10.0	80.0	1.50	24.0	0.80	1.40

Codification: V_c = (V_n − V₀)/∆V_n; decodification: V_n = V₀ + (∆V_n × V_c); V_c = codified value of the variable; ∆V_n = increment of V_n per unit of V_c; V_n = natural value of the variable to codify; V₀ = natural value in the center of the domain.