Compositional Analysis of Insoluble Pectins from Pericarp Tissue of Pear Fruit and Its Enzymatic Hydrolysis
2008
Kim, J.K. (Chung-Ang University, Ansung, Republic of Korea), E-mail: jkkim@cau.ac.kr | Hwang, B.H. (Chung-Ang University, Ansung, Republic of Korea) | Cha, J.H. (Chung-Ang University, Ansung, Republic of Korea) | Hong, J.H. (Diotech Institute, Glonet BU, Doosan Corporation, Yongin, Republic of Korea)
In order to improve juice quality and filtration process of pear (Pyrus pyrifolia) pulp extracts, insoluble pectins were obtained from pear fruit after enzymatic hydrolysis of the pulp tissue with commercial pectinases. Compositional analysis revealed that the insoluble pectin has a high ratio in rhamnose to galacturonic acid, 0.19, which was a very similar to 'modified hairy region' of apple pectin. In addition, the pear pectin was also rich in glucose and mannose, comprising approximately 40% of the polymer. Enzyme (s) capable to degrade the insoluble pectins was isolated from a commercial Aspergillus pecteolytic enzyme preparations using an alginate affinity chromatography. Aspergillus polygalacturonase (PG) was tightly bound to the alginate resin at pH 4.0 and efficiently separated by raising the pH of the elution buffer into 8.0. Gel permeation chromatography of the hydrolysates of insoluble pectin by the enzyme fractions unbound to the alginate resin showed a molecular weight shift from a large to a smaller weight polymers. The enzyme product, insoluble by PG, was further incubated with a α-rhamnosidase of commercial naringinase to hydrolyse terminal rhamnose. An increase in soluble, monomeric rhamnose confirmed that the fungal pectinase had an activity of hydrolyzing rhamno-galacturonosyl backbone of pectin in pear fruit. From the results obtained, it was concluded that insoluble pectins from pear fruit juice was effectively degraded by a fungal pectinase, generating oligosaccharides rich in terminal rhamnose.
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