Characterizing Methylation- and Acetylation Patterns in Pectins from Various Sources
|Title||Characterizing Methylation- and Acetylation Patterns in Pectins from Various Sources|
|Thesis||Master thesis in Food Technology, Wageningen University|
|Abstract||The structure of sunflower 2002, sunflower 2012-1, sunflower 2012-2, quince, lemon (CSP), lemon (NCSP), potato, and sugar beet derived pectins is studied in this current research. All pectins were degraded with PG (Polygalacturonase), PL (Pectin Lyase), and RG degrading enzymes and the products of this enzymatic degradation are studied. The aim of this project is to study the methylation- and acetylation pattern of various sources of pectins.
HPSEC analysis of the digested products shows high digestion of sunflower 2002, sunflower 2012-1, sunflower 2012-2, quince, lemon (CSP), and lemon (NCSP) pectins which is also supported by the quantification result with HPAEC-PAD. However, potato and sugar beet pectins have very low digestion profile. According to sugar composition analysis, potato pectin is known to have huge amount of galactose in RG-I region which potentially hinder the enzymes from acting in the HG region. High DM and DA in sugar beet pectin does also limit the action of enzymes.
Structure analysis of the formed oligomers is done by HPAEC-PAD, HILIC-ELSD-ESI- MSn, and MALDI-TOF/TOF-MS. For some GalA oligomers which could not be detected due to separation limitation, MALDI-TOF/TOF-MS provides a robust identification analysis of GalA oligomers without the need for separation. Based on the analysis, most of oligomers GalA found in digested pectins are unsaturated. Methyl groups appear mostly at the reducing end and non-reducing end of the digest as the result of PL digestion at both sides of oligomers. Lemon pectin (CSP) has more saturated oligomers GalA as the result of PG digestion. The acetyl groups attached at the O-2 or the O-3 position. Acetyl groups in pectin samples are mostly found in O-3 position. Ferulic acid could also be detected in some of the pectins. Its presence is an advantage since it contributes to improve the gelling property by cross-linking reactions.
Quantification of compounds obtained from digested pectins were done with HPAEC-PAD and HILIC-ELSD-ESI-MSn. The results explain that sunflower 2002, sunflower 2012-1, sunflower 2012-2, quince, lemon (NCSP), potato, and sugar beet pectins have dense distribution of metyl-esterified GalA since the digest yield much more unsaturated oligomers. However, lemon pectin (CSP) has block wise distribution of methyl groups as it has a high concentration of saturated products. The highest DBMethyl found in lemon pectin (CSP) also supports this assumption.
Keywords: Sunflower, Quince, Lemon, Potato, Sugar beer, Pectin, Oligomers, HPSEC, HPAEC, HILIC-ELSD-ESI-MSn, MALDI-TOF/TOF-MS