Effect of acid extraction conditions on yield and quality characteristics of pectin from sour orange peel

Sour orange is one of native fruits of Iran, which are widely used in the food industry, medicine and cosmetics. Sour orange peel is rich source of pectin and generally discarded as waste. In this research, response surface methodology (RSM) with Box–Behnken design was employed to optimize and to study the effects of the independent variables (temperature, time and pH) on the yield of pectin and degree of esterification of pectin extracted. percent of galacturonic acid, emulsifying properties, the viscosity and FT-IR spectra of the pectin from optimal conditions. The results showed, extraction efficiency and the degree of esterification of pectin extracted from various conditions are variable at range 5-27.5 and 6.6-46.5, respectively. The highest yield of pectin (28.78) was obtained in temperature of 95◦C, time of 90 min and pH of 1.5. Pectin extracted in optimal conditions was with degree of esterification of 24.6%, yield of galacturonic acid of 75.5%, the emulsifying activity of 45.6% and suitable emulsion stability and also the flow behavior is Newtonian in low concentrations (≤ 1 %w/v), but behavior is changed with increasing concentration of Newtonian to pseudoplastic.