Pineapple Shell as a Source of Dietary Fiber with Associated Polyphenols

Some properties of a high dietary fiber powder prepared from pineapple fruit shell were evaluated and compared to those of several commercial fruit fibers. Total dietary fiber (TDF) content (70.6%) was similar to some commercial dietary fibers from apple and citrus fruits; however, its sensory properties (neutral color and flavor) were better than those from commercial fibers above mentioned. The insoluble dietary fiber fraction amounted to 99% of the TDF. Major neutral sugars in soluble and insoluble dietary fiber were, respectively, xylose (36% of total sugar) and glucose (43% of total sugar). Total uronic acids (5.1%) and Klason lignin (11.2%) were also measured. Antioxidant activity (AA), a new property derived from the bioactive compounds associated with dietary fiber, was evaluated. At the concentration of 0.5 g of powdered sample/100 mL in the assay mixture, pineapple fiber showed a higher AA (86.7%) than orange peel fiber (34.6%), while commercial lemon and apple fibers did not exhibit any activity. Myricetin was the major polyphenol identified in pineapple fiber, which could be responsible for the AA shown. The AA together with its sensory properties, which would not interfere with those from the food to be added, make pineapple shell a suitable source of dietary fiber. Keywords: Pineapple byproducts; dietary fiber; antioxidant activity; polyphenols