Microwave heating extraction of pectin from lime peel: Characterization and properties compared with the conventional heating method

The extraction of pectin from grapefruit peel by ultrasound-assisted heating extraction (UAHE) was investigated using response surface methodology and compared with the conventional heating extraction (CHE). The optimized conditions were power intensity of 12.56 W/cm(2), extraction temperature of 66.71°C, and sonication time of 27.95 min. The experimental optimized yield was 27.34%, which was well matched with the predicted value (27.46%). Compared with CHE, UAHE provided higher yield increased by 16.34% at the temperature lowered by 13.3°C and the time shortened by 37.78%. Image studies showed that pectin extracted by UAHE showed better color and more loosen microstructure compared to that extracted by CHE, although Fourier Transform Infrared Analysis indicated insignificant difference in their chemical structures. Furthermore, UAHE pectin possessed lower viscosity, molecular weight and degree of esterification, but higher degree of branching and purity than CHE pectin, indicating that the former was preliminarily modified during the extraction process.

Pectins are defined as a group of widely distributed plant cell wall polysaccharides that contain galacturonic acid linked at both the 1 and 4 positions. The wide use of pectin as an ingredient which imparts rheological and textural properties to various food products and the development of applications beyond the food industry have brought about its increase in production and influenced research towards alternative sources and improving the overall isolation process of pectic polysaccharides. In this context, this paper aims to give a complete perspective on the current state of pectin research by mainly focusing on recent research on the extraction of pectin from other feasible sources, on the post-extraction stages of pectin recovery from plant materials (purification and fractionation), and, finally, on the advancements in the study of the physical, chemical, rheological, and functional properties of pectin.