Structure, Physicochemical Property, and Functional Activity of Dietary Fiber Obtained from Pear Fruit Pomace (Pyrus ussuriensis Maxim) via Different Extraction Methods

In this study, soluble dietary fiber (SDF) and insoluble dietary fiber (IDF) were extracted from Pyrus ussuriensis Maxim pomace via three methods including enzymic extraction (EE), microwave-assisted enzymatic extraction (MEE), and three-phase partitioning (TPP). The effects of different extraction methods on the structure, physicochemical property, and functional activity of the extracted dietary fiber were evaluated. The results showed that different extraction methods had significant effects on the extraction yield, molecular weight distribution, thermal stability, antioxidant activity, and hypoglycemic activity in vitro, but resulted in no difference in the structure and composition of functional groups. It is noteworthy that SDF extracted by TPP has a more complex and porous structure, lower molecular weight, and higher thermal stability, as well as better physicochemical properties and in vitro hypoglycemic activity. IDF extracted by MEE showed the greatest water and oil holding capacity; the highest adsorption capacity for glucose, cholesterol, and nitrite ion; as well as the strongest inhibitory activity on α-amylase. These results suggest that PUP may be a source of cheap natural dietary fiber.