Pectin determination

Pectin in almond kernels can be determined by extracting ground samples with water (soluble pectins) and then 0.05 M HCL at 100 °C for 90 min (insoluble pectins). Pectins can be determined as uronic acid by the carbazole method, using galacturonic acid as standard (Bitter and Muir 1962). 

The method can be automated as described by Berlepsch (1969) or Faichney and White (1985). Almond kernels contain only small amounts of soluble pectin (approximately llOmg/lOOg kernel), but do contain relatively large quantitives of insoluble pectin, between 1 and 2% by weight (Saura-Calixto et al. 1983). 

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Schultz, T.H. 1965a. Determination of acetyle in pectin. Determination of acetate ester content by alkaline hydrolysis followed by distillation and titration of the liberated acetic acid. In Methods in Carboydrate Chemistry, Vol. 5 (R.L. Whistler, ed.) pp. 187-189. Academic Press, New York. 

A segment factor / related M to the constant ratio between the carboxyl group and the monomer. With specific reference to pectin, a second factor (/") was later postulated to account for the degree of carboxylation.7 Subsequently, a series of pectins determined to have an anhydrogalacturo-nan content of 68-96% (/" = 0.68-0.96) did not always change the exponent of M. A CMC sample with a 0.75 degree of carboxylation, making /" = 0.25, increased the exponent by 1. 

Schultz, T.H. 1965. Determination of the degree of esterification of pectin. Determination of the ester methoxyl content of pectin by saponification and titration. Determination of the anhydrouronic acid content by decarboxylation and titration of the liberated carbon dioxide, in Methods in Carbohydrate Chemistry 5, New York Academic Press, pp. 189-194. 

Sperber BLHM, Cohen Stuart MA, Schols HA et al (2010) Overall charge and local charge density of pectin determines the enthalpic and entropic contributions to complexation with p-lactoglobulin. Biomacromolecules 11 3578-3583... 

Arabinan. This highly soluble polymer is found in the extracts of many fmits and seeds, in the boiling water extracts of pine wood (127), in the extracts of marshmallow roots (A/t/jaea officina/is) (128), and aspen (63) and willow (Sa/ix a/ba F) (129) bark. Because arabinan can be isolated from mildly degraded pectin fractions, it is often difficult to determine whether it is a hemiceUulose or a labile fragment of a larger polysaccharide and/or lignin complex. Arabinans have a complex stmcture composed almost entirely of 5-linked a-L-arabinofuranosyl units with similar residues linked to them at C-2 and/or C-3 and is soluble in 70% aqueous methanol solution. 

The aim of the investigation was to study the influence of calcium and sodium ions, pectin containing extracts of aromatic vegetative raw materials and mumio on the carbopol gelation to develop the procedure of calcium and sodium ions mass part determination in extracts of aromatic vegetative pectin containing raw materials to establish the macro- and microelement composition of mumio. 

Determination of Na " and Na" ions in raw cosmetic materials was conducted with the developed method of flame photometry. A necessity of development of method of samples preparation arose up in the work process, as this spicily-aromatic raw material contained pectin in amount 0.1-0.5% and that prevented preparation of samples by standard method of extracts dilution and required incineration of analyzed sample, time of analysis was increased in 60 times. It was established that CaCl, solution with the concentration 0,4 % caused destmctions of the carbopol gel. It was established that the addition of 0,1% CaCl, and 0,1% NaCl salts solutions into the system intensified the effect of negative action of these salts onto the gel stmcture and the gel destmcted completely. 

The determined macro- and microelement stmcture of mumio specifies onto the expediency of the application of this biologically active substance as a cosmetic raw material in the cosmetic compositions, which do not contain carbopol. The developed procedure for calcium and sodium ions determination in pectin-containing vegetative extracts is express and it is recommended for application at elaboration of cosmetic production compositions on the carbopol base. 

The stems of the tree were foimd to contain polysaccharides consisting of arabinose, galactose and galacturonic acid and only minor amoimts of rham-nose. Structural studies indicate that the polymeric material consists of 1,4-linked galacturonic acid residues, terminal, 1,4-, 1,6- and 1,3,6 galactose units and terminal and 1,5-linked arabinofuranose residues. Further studies must be performed on this in order to determine what type of pectin it can be classified as. The Hnkage data indicate that both AG-I and AG-II are present. This polymer was shown to activate polyclonal B-cells [78]. 

This paper concerns the main properties of water soluble pectins in sol and gel states. First of all, the methods of purification and characterization are discussed. The method of steric exclusion chromatography equipped with different detectors is demonstrated as the most useful to determine the macromolecular characteristics of these polymers the role of aggregation is pointed out. 

Whatever Is the technic used to determine the molecular weights on pectins, it is necessary to eliminate aggregates often mentionned in the litterature [13, 19, 21-23] for this, ultracentrifugation was used but it seems that filtration through hydrophilic membranes with very small pores (as low as 0.1 or 0.05 pm) is easier. 

At the moment, one recommends to determine the molecular characteristics of pectins using SEC chromatography equipped with a differential refractometer, a multiangle laser light scattering detector and a viscometer as previously described [25]. This technique needs no calibration with the usual molecular weight standards such dextrans and pullulans... 

The rheological behaviour in the range of LM pectin was analyzed and the sol-gel diagram established [59] for different stoichiometric ratios. In their paper, these authors determined the gel times for sodium pectate during calcium-induced gelation and the variation of the gel time with polymer concentration, stoichrometric ratio and temperature. 

The pectin solutions were mixed at 70°C with hot CaCl2 or CuCl2 solutions for 3 minutes and then poured into sealed tubes. After standing at least 48 hours at the setting temperature, the tubes were tilted and phase diagrams were determined by visual inspection. 

The sol-gel transition has been determined visually, with calcium and copper, for different pectins under different external conditions. As shown in Figure 5 for sample C44 the homogeneous gel phase is situated between the two transition lines. The extension of this phase was found to depend mainly on the DE, temperature and nature of the cation. With calcium the amount of cation required to get a gel increased with the degree of esterification and above 50% it became impossible to get a gel [8]. 

Determination of the degree of methylesterification of pectin was performed by the method of Maness et al. [8]. 

Mort, A.J., Qiu, F., and Maness, N.O. (1993) Determination of the pattern of methyl esterification in pectin. Distribution of contiguous nonesterified residues. CarbohydrJies. 247 21-35. 

Table II. Carbohydrate compositions (weight percentage) of individual oligomer peaks purified (QAE-Sephadex or HPLC ion-exchange separation, respectively) from mixtures of citrus pectin oligomers or B fruit extracts Compositions shown are for peaks whose biological activity is described in Figure 4. Uronic acid values are based on colorimetric assay. Proportions of neutral sugars were determined by GC and adjusted so that totals equal 100%. In fact, some oligomers (G7 peaks 8, 9 and 10. B extract peak 10) produced small (less than 1 % of the total integrated area), unknown peaks in the GC chromatograms.

HPAEC analyses were carried out to determine the oligomeric products released from various pectic substrates after depolymerization by the PL isoenzymes. Action pattern analyses for the concerted action of PL isoenzymes utilized 68% esterified pectin as substrate. One-ml reaction mixtures in a buffer system as detailed in section 2.2. comprising 0.5% (w/v) substrate and 5 U of enzyme were incubated for 30 s to 18 h, and then thermoinactivated. Samples of 750 pi were applied to a Carbopac PA-1 (Dionex) column before the carbohydrates were eluted over a period of 70 min using a gradient of 0.2 M KOH, 0.05 M K-acetate to 0.2 M KOH, 0.7 M K-acetate. Detection employed a Pulsed Electrochemical Detector (PED, Dionex) in the integrated amperometry mode according to the manufacturer s recommendations. 

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