Optimization of pectin extraction from Ubá mango peel through surface response methodology

A central composite design was used to determine effects of pH (1.16-2.84), extraction temperature (63-97 °C) and time (35-85 min) on the yield, degree of degree of esterification (DE) and viscosity of pectins extracted. For pectin extraction, the previously sanitized mango shells were dried and crushed to obtain the flour that was treated with an ethanol solution obtaining the alcohol insoluble residue (AIR). Subsequently, the AIR was mixed in ethanol with the extraction solution of hydrochloric acid. Pectin yields ranged from 18.8 to 32.1 g/100 g of AIR, whereas the degree of esterification (DE) and viscosity values ranged from 62.2 to 86.2% and from 1.58 to 45.85 mPa·s, respectively. An inverse correlation was found between extraction yield and viscosity. Relying upon the desirability function, two optimum conditions were determined: 35 min < t < 48 min; 85.4 °C < T < 97 °C; 1.66 < pH < 2.4 and 80 min < t < 85 min; 94.3 °C < T < 97 °C; 1.66 < pH < 1.79. Under these conditions, yields >30% from the AIR, DE ≥ 70.0% and η ≥ 20.0 mPa·s.