Pectin is characterized as a water-soluble dietary fiber (Roehrig, 1988). A characteristic feature of dietary fiber is that it is resistant to hydrolysis by human digestive enzymes. However, some fibers are partially degraded by intestinal bacteria in the colon. Thus, soluble fibers are almost completely metabolized to short-chain fatty acids, methane, carbon dioxide, hydrogen, and water.
Cummings and co-workers (1979) have suggested that pectin is completely metabolized in the human gut, whereas Müller and Kirchgessner (1985) reported an apparent digestibility value of 79% and a metabolizability of 71%. Net energy values were measured as 9 kJ/g digestible pectin corresponding to 7 kJ/g pectin. The net energy value of pectin is thus only 64% of the energy value of starch digested in the small intestine.
In most countries, food legislative authorities recognize pectin as a valuable and harmless food additive. If regulated, permitted use levels are generally in accordance with "good manufacturing practice". Pectin was evaluated and cleared toxicologically by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1981 (WHO, 1981). It was verified that there are no toxicological differences between pectins and amidated pectins and a group ADI (Acceptable Daily Intake) "not specified" was established for pectins and amidated pectins.
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