De‐esterification pattern of Valencia orange pectinmethylesterases and characterization of modified pectins |
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| Authors: | Hyoungill Lee Josh Rivner Jeffrey L Urbauer Nissim Garti Louise Wicker |
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| Affiliation: | 1. Food Science & Technology, University of Georgia, Athens, GA 30602, USA;2. Biochemistry and Molecular Biology, University of Georgia, Athens, GA, 30602, USA;3. Chemistry, University of Georgia, Athens, GA 30602, USA;4. Casali Institute of Applied Chemistry, The Hebrew University of Jerusalem, 91904 Jerusalem, Israel |
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| Abstract: | BACKGROUND: Pectinmethylesterase (PME, E.C. 1.1.11) isozymes from Valencia orange preparations with different specific activities were used to de‐esterify citrus and sugar beet pectins. Enzymatic modification offers the opportunity to create pectins of tailored functionality and gelling ability. RESULTS: Based on nuclear magnetic resonance spectra, catalysis by all PME extracts produced block‐wise de‐esterification patterns in both citrus and sugar beet pectins. PME activity resulted in increased numbers of contiguous de‐esterified groups and decreased numbers of contiguous esterified groups. De‐esterification by PMEs increased the elastic property (G′) of citrus and sugar beet pectins in the presence of calcium from 10 to 571 and from 0.05 to 201 Pa, respectively. CONCLUSIONS: The results demonstrate the predilection of citrus PMEs toward block wise de‐esterification of pectins and the relationship between calcium binding ability and de‐esterification degree and patterning. Within a narrow range of de‐esterification (37–48%) and with a narrow distribution of contiguous groups, PME modification did not markedly change gelling ability. At lower or higher de‐esterification values, a 2‐fold increase or 50‐fold decrease, respectively in G′ values was observed. Copyright © 2008 Society of Chemical Industry |
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| Keywords: | block wise calcium sensitivity gel strength functionality |
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