Structure of pumpkin pectin and its effect on its technological properties

The aim of this work is to investigate the structural features, physicochemical, rheological, and emulsifying properties of pectin extracted from pumpkin "Cucurbita maxima" pulp and peel. After the peel and pulp of fresh pumpkin were solubilized in water at high temperature (80 degrees C) and clarification, the obtained filtrate was treated with aluminum sulphate, which precipitates a fibrous coagulum. The results found that the major functional groups of pectin isolates identified by Fourier transform infrared are: -OH, CH2, C=C, -C-O-C-, and CH3. The results obtained using nuclear magnetic resonance methods suggest that these polysaccharides consist of two domains: the first one is homogalacturonan and the second is formed by rhamnogalacturonan. Mineral and metal ions on pectin surface detected using scanning electron microscopy coupled to energy dispersive X-ray analysis were different pulp and peel pectin. Rheological behavior of these biopolymers is suitably represented by the Herschel-Bulkley and power law models. The extracted pectin has a viscosity spectrum expressed by the following properties: G', G '', G*, and vertical bar(eta)over dot vertical bar(omega) which, respectively, have the following values: 0.28-57.63, 0.15-34.38, 0.39-67.12, and 1.82-831.08 Pa s. These macromolecules have a negative charge on their surface. Rheological properties and emulsifying activity are significantly influenced by the structural composition and physicochemical properties.