The variability in the chemistry of pectin, including the number of esterified methoxyl groups to galacturonic acid, the differences in molecular weight among pectins, and its intrinsic properties, contribute to the interest in dietary soluble fiber. The amount of pectin in citrus and other fruits varies widely and can be dependent on climate, soils, and other factors, e.g., variety, method of extraction, and fruit maturity. Pectin is located in the middle lamellae of plant cell walls and is generally associated with cellulose, forming the insoluble protopectin. The primary mechanism of chain association for low-methoxyl pectins during gel formation is dimerization of polygalacturonate sequences. The range of food uses for pectins as thickening agents is increasing, and there are also some applications in pharmaceuticals and in the preparation of biodegradable films. Pectin has also been shown to increase bile acid excretion, although with much less of an effect compared to bile acid-binding resins.