Commercial pectins are derived mostly from the peel of lemon and lime, orange and grapefruit, however, are used to a lesser extent.  The degree of methylation, molecular weight and pH  have a major impact on pectin which in turn plays a  potential role on human health.  Methylation influences the number of receptor binding sites that inhibit the spread of roaming tumor cells.  It is critical to have a maximum number of available binding sites on the pectin molecule.  It is believed that the higher the percentage of methylation, the fewer receptor binding sites.  Currently, commercial pectins have 50-70% methylation.  In several companies, however, MCP have low methylation percentages between 5-10%.  Another factor important in health benefits of pectin is molecular weight.  Commercial pectins have molecular weights ranging from 50,000 to 150,000 daltons.   To be absorbed by the digestive tract through the blood stream pectin needs to have a molecular weight between 8,000-10,000 daltons.  D-galacturonic acid is the principal constituent of the pectin molecule, but some neutral sugars are also commonly present in pectin.  The final factor in pectin and potential health benefits is its pH.  Commercial pectins typically have a pH of 3.2 which tends to be acidic to be useful.   The MCP produced by several companies, however, have more neutral pH of 5.7-6.3.   The potential health role of MCP depends on the appropriate methylation, molecular weight and pH.  Pectin levels published and cited for some fruits needs to be reconsidered since there are conflicting values reported from several authors.   Membranes which constitute 28% of the edible portion of grapefruit has approximately 4% pectin.  If consumed with juice vesicles, the membranes could add another 1%  pectin.  For example, for a significant serum cholesterol reduction, we need approximately 6 grams pectin per day.  Although consumption of peeled citrus fruits greatly increases pectin intake since juice vesicles and carpellary membranes are included.  Pectin levels in conventionally cut grapefruit sections are somewhat lower than those of peeled grapefruit because of the carpellary membranes have been excluded by the cutting process.  Moreover, newer technologies for peeling and sectioning grapefruit yield whole segments, with carpellary membranes largely intact.  As a result, dietary pectin contributed by these intact segments would be presumably similar to that of peeled oranges. 

                 The most effective sources of citrus pectin and dietary fiber are peel (albedo), membranes, and juice vesicles.  Peel and membranes are unsuitable for consumption due to excessive levels of bitter compounds such as naringin and limonin.   Juice vesicles, however, are relatively palatable and currently incorporated at low levels in many citrus juices and beverages to provide a more natural fruit juice appearance. To satisfy the need of 6 grams of pectin per day, about 125 grams of juice vesicles would be required if we consider an average of 4.8% pectin in grapefruit on a wet-weight basis. 

                Although commercial pectin has a potential role in the food industry, it has a  greater role on potential human health based on its processing conditions.