Table 1. Face-centered central composite design with independent (temperature and time) and response variables (extraction yield and gel strength) for gelatin extraction from Korean native black goat skin

Experiment number Factors Response variables
X1 X2 Extraction yield (%, w/w) Gel strength (g)
1 60 3 12.1 260.4
2 60 3 12.6 262.9
3 60 3 12.5 263.9
4 70 4 13.3 251.8
5 70 3 13.2 255.6
6 50 3 10.7 271.6
7 60 2 12.0 264.3
8 60 3 12.6 262.2
9 60 4 13.4 252.5
10 60 3 13.0 266.4
11 70 2 12.7 256.1
12 50 2 10.2 263.2
13 50 4 11.2 265.2
X1, extraction temperature (°C); X2, extraction time (h).