Potato peels contain valuable substances such as pectin extraction and the use of potato peels to produce pectin with appropriate properties can solve the biological problems resulting from these wastes in addition to value-added. The overall objective of this study is to investigate the effect of three variables including temperature (۳۵, ۶۵, and ۹۵ °C), time (۴۰, ۱۲۰, and ۲۰۰), and pH (۱, ۲, and ۳) on the yield, galacturonic acid percentage and degree of pectin esterification extracted from the potato peels and optimization of the condition of extraction. The response surface method is used to optimize the conditions of extraction. The physicochemical properties of extracted pectin under optimum conditions were compared with commercial citrus and apple pectins by pectin flow behavior tests at different concentrations, FT-IR spectrum, and pectin molecular weight. The results of optimized single independent variables showed that the highest extraction yield of potato peel was ۱۴.۸۷% at ۹۵ °C, ۱۲۰ min time, and pH ۱. The highest percentage of extracted galacturonic acid pectin in potato peel was ۳۶.۳۷% at ۹۵ °C in ۱۲۰ min and pH ۱. The highest degree of esterification of extracted pectin from potato peel was ۴۱.۸۲۰% at ۶۵ °C in ۴۰ min time and pH ۳.۰۰. Simultaneous optimization of extracting pectin to achieve maximum yield was galacturonic acid with ۱۰۰% desirability at ۹۵ °C, ۲۰۰ min time, and pH ۱ in this condition, the yield was ۱۵.۲۳% and galacturonic acid was ۳۸.۰۷۱۲%. The highest stability of extracted pectin emulsion from potato peel was observed at ۴ °C on the first day. Also, the FT-IR results showed that the strong absorption between ۳۲۰۰-۳۵۰۰ cm-۱ in the extracted pectin sample was related to the intracellular and extracellular vibration of the hydrogen bond in the galacturonic acid polymer. By increasing the concentration of pectin (۰.۱ to ۲%) their viscosity was increased and the behavior of all samples was Newtonian and their flow index was about one. The molecular weight of extracted pectin from potato peel under optimum conditions was ۵۳.۴۶ kDa after ۳۰ days of storage at ۴ and ۲۳ °C with emulsion stability ۸۵.۱ and ۶۳.۱, respectively. The results of this research showed that extracted pectin from potato peel can be introduced as a source of pectin to the market.
