Comparative Studies of Combined Influence of Variables on the Esterification Degree of Pectin Extracted by Sulfuric Acid and Citric Acid

Figure 4

Surface plots for DE of pectin extracted by citric acid. (a) Effect of extraction time and temperature on the DEc with pH of 2. (b) Effect of extraction time and pH on the DEc with extraction temperature of 90°C. (c) Effect of extraction temperature and pH on the DEc with extraction time of 1.5 h.

(a)

(b)

(c)