Fiber: composition, structures, and functional properties

Abstract

Kiwifruit dietary fiber consists of cell-wall polysaccharides that are typical of the cell walls of many dicotyledonous fruits, being composed of pectic polysaccharides, hemicelluloses, and cellulose. The kiwifruit pectic polysaccharides consist of homo- and rhamnogalacturonans with various neutral, (arabino)-galactan side chains, while the hemicelluloses are mostly xyloglucan and xylan. The proportions of pectic polysaccharide, hemicellulose, and cellulose in both green 'Hayward' and 'Zespri® Gold' are similar and are little affected by in vitro exposure to gastric and small intestinal digestion. The hydration properties of the kiwifruit-swelling and water retention capacity-are also unaffected by foregut digestion, indicating that the functional properties of kiwifruit fiber survive in the foregut. However, in the hindgut, kiwifruit fiber is fermented, but whole kiwifruit consumed in association with slowly fermented fiber leads to distal displacement of fermentation, indicating that hindgut benefits of kiwifruit may result from its interaction with other dietary sources of fiber.