Beli R. Thakur

Chemistry and uses of pectin : A review

Pectin is an important polysaccharide with applications in foods, pharmaceuticals, and a number of other industries. Its importance in the food sector lies in its ability to form gel in the presence of Ca2+ ions or a solute at low pH. Although the exact mechanism of gel formation is not clear, significant progress has been made in this direction. Depending 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-linking of pectin molecules involves a combination of hydrogen bonds and 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 molecule--influence the gelation of pectin. In the food industry, pectin is used in jams, jellies, frozen foods, and more recently in low-calorie foods as a fat and/or sugar replacer. In the pharmaceutical industry, it is used to reduce blood cholesterol levels and gastrointestinal disorders. Other applications of pectin include use in edible films, paper substitute, foams and plasticizers, etc. In addition to pectolytic degradation, pectins are susceptible to heat degradation during processing, and the degradation is influenced by the nature of the ions and salts present in the system. Although present in the cell walls of most plants apple pomace and orange peel are the two major sources of commercial pectin due to the poor gelling behavior of pectin from other sources. This paper briefly describes the structure, chemistry of gelation, interactions, and industrial applications soft pectin.

Food irradiation‐chemistry and applications∗

Abstract Food irradiation is one of the most extensively and thoroughly studied methods of food preservation. Despite voluminous data on safety and wholesomeness of irradiated foods, food irradiation is still a “process in waiting.” Although some countries are allowing the use of irradiation technology on certain foods, its full potential is not recognized. Only 37 countries worldwide permit the use of this technology. If used to its full potential, food irradiation can save millions of human lives being lost annually due to food‐borne diseases or starvation and can add billions of dollars to the world economy. This paper briefly reviews the history and chemistry of food irradiation along with its main applications, impediments to its adoption, and its role in improving food availability and health situation, particularly in developing countries of the world.

Quality attributes of processed tomato products: A review

Abstract Tomato is the second largest vegetable crop in dollar value in the United States and other parts of the world. World production of tomatoes for processing stands over 20 million tons per annum, with more than 50% in the United States. Processed tomato products are an important source of minerals and vitamins in the diet of U.S. consumers. An American consumes over 12 kg of processed tomatoes per year excluding tomato ketchup and sauce. In addition to nutritive value, the color, consistency, and flavor are the major quality attributes of processed tomato products which influence the buying behavior of the consumer. These attributes are highly variable and change with changes in fruit cultivar, growing conditions, and/or processing parameters. This paper reviews the quality factors of processed tomato products along with the factors that affect them.

High‐pressure processing and preservation of food

Abstract High pressure alone or in combination with other technologies offers great potential for producing foods with natural characteristics. Pressure works independent of size and geometry of food resulting in even preservation. The preservative effect itself is influenced by a number of factors with different foods requiring different levels of pressure. Various microorganisms also vary in their response to high pressure and the effect depends on the physical state of the microorganism and the composition of the medium. Because enzymes have a high resistance to pressure, enzymatic and oxidative spoilage are the major limiting factors in shelf‐life extension of pressure‐processed foods. This paper briefly reviews the effects of high pressure on various foods, enzymes, and microorganisms; and discusses some of the advantages and disadvantages associated with the use of this technology.

Chemistry of sorbates: a basic perspective

Abstract Sorbic acid and its potassium and calcium salts are used as preservatives in a large number of foods, feeds, Pharmaceuticals, and cosmetics. In the dry and crystalline state, sorbic acid is stable and no degradation occurs even if stored at room temperature for a long time. However, in solutions and in foods, it undergoes autoxidation during storage, forming carbonyls and other compounds. Many factors (e.g., pH, temperature, packaging, water activity, and composition of food) influence its stability. Degradation of sorbic acid is associated with development of browning in foods. Acetaldehyde and /3‐carboxylacrolein have been reported to be the major degradation products of sorbic acid in aqueous solutions. β‐Carboxylacrolein is found to be responsible for sorbate‐induced browning in foods as it reacts with amino acids and proteins to form brown pigments. Since sorbic acid mainly degrades by autoxidation, deoxygenation and vacuum packaging in oxygen impermeable films or laminates have been suggest...

Role of pectin methylesterase in tomato fruit ripening and quality attributes of processed tomato juice

Abstract We have created transgenic tomato fruits with over a 10-fold reduction in pectin methylesterase (PME) activity by expressing a PME antisense gene. Reduction in PME activity does not interfere with the fruit ripening and vegetative growth of plants, but is associated with increases in soluble and total solids, mol. wt. and methyl esterification of pectins, and modifies accumulation and partitioning of cations between soluble and bound forms. The processed juice from transgenic fruits shows increases in serum and efflux viscosity and precipitate weight ratio. Ketchup prepared from transgenic fruits has a significant lower Botswick value, reduced serum separation and higher serum viscosity than control. Collectively, a marked improvement in fruit processing attributes results from lower PME activity in fruits.