Pectins precipitation

Pectin. Pectin [9000-69-5] is a generic term for a group of polysaccharides, mainly partially methoxylated polygalacturonic acids, which are located in the cell walls of all plant tissues. The main commercial sources of pectin are citms peel and apple pomace, where it represents 20—40% and 10—20% of the dry weight respectively. The pectin is extracted, the extract purified, and the pectin precipitated (50) increased extraction times lead to the production of low methoxyl pectins. 

Method of purification Following decolorization, the extracts are concentrated by evaporation or the pectins precipitated with alcohol or acetone. 

Low-methoxyl pectinates precipitated by calcium were compared with like pectinates precipitated by alcohol. All the pectinates were prepared by a simultaneous acid extraction and demethylation of pectins from apple pomace at 60 C. Calcium pectinates were of higher grade but lower in yield than alcohol-precipitated pectinates prepared under comparable conditions on the basis of 65% soluble solids. Alcohol coprecipitates materials other than pectin, which act as diluents, increasing the apparent yield of the alcohol-precipitated pectinates and lowering their grades. Demethylation increased with time of treatment and acidity. The calcium-precipitated pectinates were purer, as denoted by the calcium pectate content. The calcium pectinates were studied primarily for their use in gels of low sugar content. 

The edible salts of calcium and magnesium do not precipitate pectins until the degree of esterification of the pectin molecule has been reduced below 8.2% methoxyl content on the basis of 100% calcium pectate (10, 17). In 1935 a patent (16) was granted on the use of soluble salts of alkaline earth metals, such as calcium chloride, to precipitate pectic substances which had received a partial de-esterification treatment. Olsen and Stuewer obtained a patent (IS) on a digestion-extraction procedure, termed pickling and carried out at less than 50 C. below pH 1 for a period sufficient to produce pectin precipitable by calcium salts at pH 4. The metal-free pectinic acids can be isolated from either the aluminum or calcium salts by treatment with acidified alcohol in accordance with methods well known for years. 

Cation adsorption appears to be important in the formation of cationic bridges as a mechanism for bile acid, fatty acid and mineral adsorption in the upper intestine (20). The affinity of copper for carboxylic acid groups has been employed in pectin precipitation (10, 21) and in determinations of cation exchange... 

The extraction of pectin is determined by the intended field of application. If it is to act as a gelling agent, then the plants are extracted with water with the addition of acid, when pectin precipitates out on adding alcohol. Pectin as thickener is extracted with alkali. A distinction can be made between gelling agent grades with and without Ca ... 

When appreciable amounts of pectin, proteins, lipids, unwanted polyphenols, or other compounds are suspected to be present in anthocyanin-containing extracts, some of them can be precipitated or the anthocyanins may be crystalhzed and separated from the others. Pectin and proteins can be removed by organic solvents such as methanol and acetone in order to reduce their solubility, then precipitated and separated by centrifugation. Gelatin was used to remove proanthocyanidin due to its high molecular weight. Anthocyanins were reported to be precipitated early by lead acetate to achieve isolation from other materials. ... 

The A. irakense strain is clearly able to hydrolyze pectin on solid medium. A clear halo was observed after incubation for seven days and overlayed with HTAB, indicating the degradation of pectin, whereas non-hydrolyzed polymer is precipitated. For the other Azospirilhim species, we were not able to demonstrate pectinolytic activity in this way. 

Qualitatively, the results observed with ferric chloride and lead acetate were highly variable. It was first noted with ferric chloride that gels were forming within the reaction vessel We observed the formation of translucent gels in the reaction vessel with calcium chloride, spermidine and ferric chloride. In the case of lead acetate, a feathery type precipitate formed in the reaction vessel. Macdonald et al. (14) observed formation of a clear gel and flocculated precipitate in high ester pectin treated with lemon endocarp and peel PE isozymes, respectively. They hypothesized that the different gel structures were due to unique mechanism of deesterification by the PE isozymes. Our results with different cations and formation of different gel structure or precipitate seems to be similar to that reported by Macdonald et al. (14). If there is a different mechanism of de-esterification for plant PEs,... 

AE catalyses the cleavage of acetyl groups from different substrates. The enzyme activity was determined by measuring the release of acetic acid. The amount of acetic acid was measured spectrophotometrically using an acetic acid analysis kit (Boehringer, Mannheim). The activity of AE was measured in 0.6% sugar beet pectin solubilised in 25 mM Na-succinate pH 6.2 and incubated with enzyme fraction in total 500 nl assay. The samples were incubated at 40°C and aliquots were examined after 0, 1, 2 and 3 hours of incubation. The enzyme reaction was stopped by incubating the samples at lOO C for 5 min. Precipitated... 

Preparation of enzyme. Culture fluids of three days on glucose 0.5% (w/v) and then four days on pectin 0.5% (w/v), cleared by passing through glass fibre filter, were used for the purification of PNL. A small quantity was remainder, dialyzed, and assayed for enzyme actitity and the remained was precipitated. 

Figure 5. Analytical isoelectric focusing. Ultrathin layers (0.4 nun) of polyacrylamide with ampholytes pH 2-11 were used. Samples of 10 pg of protein in 10 pi of 1 % glycine were applied. A.- Silver staining. B.- Stain for activity on overlays containing pectin in tris/HCl buffer at pH 8.0 with CaClj M.- Broad pi Calibration Kit protein (Pharmacia), samples of 5 pg of protein were applied. 1.-Ammonium sulphate precipitated proteins from cultures on pectin. 2.- Fractions with PNL activity eluted from the Superdex 75HR1030 column. 3.- Purified PNL.

Total RNA was isolated from mycelia cultured 6 days on PG-inducing and non- inducing conditions (apple pectin and glucose, respectively). The RNA extraction was performed according to the phcnol-SDS method combined with selective precipitation using LiCl. RNA concentration was estimated by absortion at 260nm. 

The second assumption was that the maceration released cells Cj and hydrosoluble pectin P. The cell wall of these cells may have been partially degraded to produce non-degradable cells C2 and pectin P]. PI was also partially degraded to ultimate alcohol precipitable pectins P2 and oligouronides O. 

During a study of the biosynthesis of pectin substances, a sensitive micromethod for the assay of pectinesterase activity was developed111 that uses a biosynthetically prepared [14C] methyl-labelled pectin as the substrate after enzymic de-esterification, the substrate remaining is precipitated with an excess of methanol and, after centrifugation, the [14C]methanol present in the supernatant liquor is counted in a liquid scintillation counter in order to assess the pectinesterase activity. 

Rather than practicing medicine he helped establish the Industrial Testing Laboratory, Inc. in Kansas City by the mid-1920s. He developed a process for the production of pectin as a precipitate from apples from a vinegar plant. 

Pectin is dissolved in the NDF method, but is part precipitated with ADF. 

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