Extraction and investigation of physicochemical properties of pectin extracted from eggplant cap waste

Along with increased production and fruit and vegetable processing, there is a lot of byproducts. Eggplant cap is also one of the byproducts which contains valuable materials such as pectin which is both economically and environmentally beneficial. The general objective of this research was to investigate the effect of three temperature variables (60, 75 and 90°C), time (50, 100 and 150 min) and pH (1.5, 2.52 and 3) on the rate of yield, percentage of galacturonic acid and degree of pectin esterification extracted from the eggplant cap. The response surface methodology was used to optimize the extraction conditions. In order to study the physicochemical properties of obtained pectin, emulsion stability tests were carried out at different days and temperatures and flow behavior in different concentrations and FT-IR were performed. According to the results, the highest extraction yield of the eggplant cap was observed in 12.30% under severe conditions of extraction at 90 °C, 150 min and pH 1.5. The highest galacturonic acid percentage of extracted pectin of eggplant cap was observed 39.84%, at 75°C, 100 min and pH, 2.52. The highest esterification degree of extracted pectin of eggplant cap was 51.750, at 60°C, 50 min and pH 3. The results of analysis of variance showed that extraction temperature was the most effective factor on the yield and esterification degree of extracted pectin. The highest emulsion stability of eggplant cap pectin was at 4 °C and the first day. With increasing the concentrations of pectin samples (from 0.1 to 2%), their viscosity was increased and flow behavior of all samples were Newtonian and their flow index was close to one. FT-IR results also showed that the strong absorption between 3000 cm-1 in the extracted pectin samples was related to intra-and extracellular vibration of the hydrogen bond in the galacturonic acid polymer.