CHEMISTRY AND USES OF PECTIN - A REVIEW

Pectin is an important polysaccharide with applications in foods, phar maceuticals, and a number of other industries. Its importance in the f ood sector lies in its ability to form gel in the presence of Ca2+ ion s or a solute at low pH. Although the exact mechanism of gel formation is not clear, significant progress has been made in this direction. D epending on the pectin, coordinate bonding with Ca2+ ions or hydrogen bonding and hydrophobic interactions are involved in gel formation. In low-methoxyl pectin, gelation results from ionic linkage via calcium bridges between two carboxyl groups belonging to two different chains in close contact with each other. In high-methoxyl pectin, the cross-l inking of pectin molecules involves a combination of hydrogen bonds an d hydrophobic interactions between the molecules. A number of factors- pH, presence of other solutes, molecular size, degree of methoxylation , number and arrangement of side chains, and charge density on the mol ecule-influence the gelation of pectin. In the food industry, pectin i s used in jams, jellies, frozen foods, and more recently in low-calori e foods as a fat and/or sugar replacer. In the pharmaceutical industry , it is used to reduce blood cholesterol levels and gastrointestinal d isorders. Other applications of pectin include use in edible films, pa per substitute, foams and plasticizers, etc. In addition to pectolytic degradation, pectins are susceptible to heat degradation during proce ssing, and the degradation is influenced by the nature of the ions and salts present in the system. Although present in the cell walls of mo st plants, apple pomace and orange peel are the two major sources of c ommercial pectin due to the poor gelling behavior of pectin from other sources. This paper briefly describes the structure, chemistry of gel ation, interactions, and industrial applications of pectin.