Pectins fractional extraction

Figure 3. Titration of pectin fractions extracted from young cell walls. A, B, C, pectins extracted with boiling water D, extracted with hot EDTA. A, B, intact PFi C, demethylated PFj. Titrations were performed...

TABLE VI. Sugar composition (%) of apple CWM and AIR, and pectin fractions extracted with (A) cold water, (B) hot water, and (C) ammonium oxalate... 

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. 

DM and DAc of various pectin fractions except those of OHSP (due to deesterification during extraction) are summarized in Table 5. The DM of WSP of conventionally canned carrots did not significantly differ from that of fresh carrots,while in the presence of CaCk a considerable increase was observed. This increment can be ascribed to cross-Unking of water soluble-low methylated... 

ChSS and DASS were rich in arabinose, galactose and uronic acids. These were, as expected, pectin-rich extracts and had a very similar sugar composition. The 1 MASS fraction was also rich in arabinose, galactose and uronic acids, but next to that it is also enriched in... 

The polysaccharides present in the pectin-rich extract ChSS were fractionated, based on their charge density for further characterisation. The elution pattern of ChSS is shown in Figure 1, and it can be seen that the relative uronide content of the fractions increased with increasing salt concentration of the eluens. 

Since the determination of the water, oxalate and alkaline soluble pectin is just an extraction followed by a precipitation, this loss could be either the result of a poorer extractability or of a degradation into lower molecular weight pectin fractions which no longer can be precipitated by ethanol. Obviously the degradation is negligible, because the viscosity of pectin solutions which should be a sensitive indicator for the breakage of already few bonds is not altered by the application of HP. 

In order to study the composition and structure of pectins and their changes during ripening, storage and processing, various procedures have been developed for fractional extraction of pectins. A typical laboratory scheme for sequential extraction of pectin from plant cell wall materials is summarized in Figure 9.3. (Selvendran and O Neill, 1987 Voragen et al., 1995, Vierhuis et al., 2000). Not every step in the scheme is used by all of the researchers, and decisions depend on the source materials. 

In all the colorimetric methods, galacturonic acid is liberated during the assay by hydrolysis of polymeric pectin. An application of the carbazole method, after extraction of pectin from various fruits and vegetables, has been described (6), as has been an automated carbazole method for monitoring uronic acid levels in pectin fractions (7). 

Figure 1. Extraction of pectin fractions of AIS of apples (peeled and cored).

Extraction and purification. An alcohol-insoluble residue was prepared from sugar-beet pulp. Products successively extracted from this material were water-soluble pectin (WSP), oxalate-soluble pectin (OXP), acid-soluble pectin (HP) and alkali-soluble pectin (OHP). Extractions were done according to the procedure described by Barbier and Thibault (7). The pectins were purified by chromatography at pH 4.8 on Whatman DEAE-cellulose DE 52 under the conditions described by Barbier and Thibault (7). As the alkali-soluble pectin binds irreversibly to this column, this fraction was purified by precipitation with CuSO and extensive washing of the precipitate. Cupric ions were subsequently removed by dialysis against Na2EDTA at pH 4.8. 

During the course of bile acid binding assays of carrot AAIR it was noted that a peak emerged at the void volume during HPLC of the solution of bile acid that had been in contact with the fiber. We therefore suspected that the bile acid solution was solubilizing some small fraction of the AAIR. Accordingly, carrot AAIR was then extracted with sodium deoxycholate and a pectin fraction was isolated by alcohol precipitation of the... 

Preparation of Apple CWM and AIR and Extraction of Pectin Fractions. Apples ( Granny Smith variety) were cored and peeled and the resulting pulp (2 kg batches) was stored in ethanol suspension to minimize enzymic oxidation. Separate batches of pulp were processed, as described for carrot preparations, to furnish apple CWM (32.5 g) and apple AIR (39.8 g) for which analytical data are recorded in Table VI. Polysaccharide fractions B (4 g) and C (2.5 g) were extracted from CWM with water at 80° and aqueous 1% ammonium oxalate at 80°. Likewise polysaccharide fractions A (2.1 g), B (5.2 g), and C (4.5 g) were Isolated from AIR by extraction with water at room temperature, 80°, and with aqueous 1% ammonium oxalate... 

O beirne, D., Buren, J. P. van, and Mattick, L. R. (1982). Two distinct pectin fractions from senescent idovned apples extracted using non-degradative methods. Journal of Food Science 47, 173-176. 

In 2012, different pectin fractions were extracted from the above-ground part of St. John s wort Hypericum perforatum L) [110]. Using an aqueous solution of ammonium oxalate, the results obtained indicate that pectins have a low degree of esterification with 4.8% for the fraction with higher nelds, and a total of 6.2%. With the results obtained, the above-ground part of St John s wort can be considered a source of LDE pectin extraction, and relatively low yields can be improved using other extraction methods. 

Detergent Methods. The neutral detergent fiber (NDF) and acid detergent fiber (ADF) methods (2), later modified for human foods (13), measure total insoluble plant cell wall material (NDF) and the cellulose—lignin complex (ADF). The easily solubilized pectins and some associated polysaccharides, galactomaimans of legume seeds, various plant gums, and seaweed polysaccharides are extracted away from the NDF. They caimot be recovered easily from the extract, and therefore the soluble fiber fraction is lost. 

Figure 3 Size fractionation of EDTA-soluble polyuronides from Rutgers and transgenic fruit juice processed by cold- and hot-break methods. Pectin from processed juice was extracted as ethanol-insoluble solids and size fractionated on a Sepharose CL4B column. Under the same chromatographic conditions, elution of the branched dextrans with average molecular mass 2000, 500, 252, 151, 40 and 17.7 kD-peaked in fraction number 46, 50, 54, 62, 67 and 72, respectively. Modified from Thakur et al. [23].

To study the cell wall alterations diiring processing in detail, total pectic fractions were separated by extraction of AIR from fresh, blanched and sterilized beans with acetate buffer, CDTA and NajCOj. Analysis showed that sterilization caused a lai e increase in the amount of buffer soluble pectins (Figure 1). 

Pectin degradation requires fee combined action of various enzymatic activities. However, evaluation of fee contribution of individual pectinases in Suit juice extraction and clarification is rather complicated. Most commercial pectinolytic enzyme preparations are produced by fermentation wife filamentous fungi, mostly strains belonging to fee genus Aspergillus,. plication studies with mixtures of isolat enzymes obtained by fermentation or by means of fractionation of commercial enzyme preparations can be used to assess the importance of fee various individual enzymes. Subsequently, molecular biology and fermentation technology can be used to enhance specific desirable enzymatic activities. 

---