Submitted to: Food Hydrocolloids Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/11/2009
Publication Date: 5/28/2009
Citation: Yoo, S., Lee, B., Savary, B., Lee, S., Lee, H.G., Hotchkiss, A.T. 2009. Characteristics of enzymatically-deesterified pectin gels produced in the presence of monovalent ionic salts. Food Hydrocolloids 23. p.1926-1929. Interpretive Summary: The enormous volume of fruit and vegetable processing residues, such as orange peels and sugar beet pulp, has become a problem in this country. These residues can be used as cattle feed components but their value is low (< 5 ¢/pound) and there is more supply than demand. However, these residues are rich in carbohydrates that may have value as ingredients in food and biobased products. One of these carbohydrates, pectin is a valuable food gum with new applications as a functional food ingredient and in biobased products. Previously, pectin was known to gel in the presence of calcium and sugar under acidic conditions. We developed a new system for pectin gelation. Enzymes were used to change the structure of pectin so that it could gel in the presence of another salt, potassium chloride. We demonstrated that a combination of fungal and plant enzymes worked best to dramatically improve the gel strength of pectin in the presence of potassium. Use of this pectin gelation system will expand the functional food ingredient applications of pectin and add value to citrus processing residues benefiting citrus growers and processors as well as consumers.
Technical Abstract: Pectin methylesterases (PMEs) from Valencia orange (p-PME) and Aspergillus aculeatus (f-PME) were used to produce pectin gels in the presence of 0.2 M monovalent ionic salts. At pH 5.0, pectin gels were induced during enzymatic deesterification of high methoxy pectin, with greater deesterification observed using p-PME compared to f-PME. The limit of f-PME deesterification was pectin with DE of 30.5-31.9 which did not gel, while p-PME reduced the pectin DE to 16.0-17.2 which gelled under these conditions. The pectin gel induced by KCl was significantly stronger than the NaCl-induced gel, but LiCl did not induce pectin gelation. The gel strength was influenced by both DE and species of monovalent cation. The KCl-induced gels released less water than NaCl-induced gels. A synergistic effect on gel strength was observed from pectin treated with a combination of (p + f)-PMEs, producing even more stable gels. These results indicated that the pectin gelation of our system would be enhanced both by using larger monovalent cation and by lowering the DE value, which would presumably be attributed to the different action patterns recognized for p- and f-PMEs. This pectin gelation system could provide a useful alternative to acid-sugar or calcium cross-linked gels in food and other industrial applications.