Pectins analysis

Hourdet, D. and Muller, G. 1991. Solution properties of pectin polysaccharides—HI molecular size of heterogeneous pectin chains. Cahbration and application of SEC to pectin analysis, Carbohydrate-Polymers, 16(4) 409-432. 

Kinter, P.K. and Van Buren, J.P Carbohydrate interference and its correction in pectin analysis using the m-hydroxydiphenyl method, /. Food Sci, 47, 756, 1982. 

New methods have been developed for texture analysis of jams and jellies. These indicate that the SAG test is unreliable for predicting the effect of pectin on the final product. Is the SAG method the pectin analysis for the future, or should it be complemented by other analyses to give a more complete picture of any pectin ... 

Pectin analysis also needs more refining and emphasis. Pectic substances are a group of related substances (protopectin, pectin, and pectic acids), each with specific chemical characteristics (9). Both the protopectin and the pectic acid, pectinic acid, form insoluble complexes with metals, especially calcium. These too, like the protein, are concentrated in the persistent middle lamella-primary wall complex. 

Pectin Most standard procedmres for pectin analysis in vegetables and legumes involve extraction of the pectin as pectic acid followed by precipitation. Aqueous extraction of the pectin is followed by saponification with cold alkali, acidification, and the quantification of the precipitate. The pectic acid can be precipitated as calcium pectate or, as in the AOAC procedure, using ethanol. 

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 worm like chain behaviour of the pectins is developped allowing to predict the dimensions of the chain as soon as the persistence length is known. The experimental data are compared with the theoretical prediction obtained from conformational analysis. 

How might these oligomers be produced in the fruit The easiest answer is that limited PG action on cell wall pectins generates them, and we have tested this point in vitro. CDTA- and Na2C03-soluble pectins and PGA (included as a positive control) were incubated with purified tomato PGl. Surprisingly, only the carbonate-soluble material and PGA were digested (based on HPLC analysis of reaction mixtures and generation of... 

Structural analysis of the two pectate lyases PelC and PelE (5, 6), demonstrated that these proteins fold in a large heHx of parallel P strands. A stack of asparagine residues parallel to the helix probably plays a role in the stabUity of this structure. Identification of the structurally conserved amino adds lead to a reaHgnment of the protein sequences (7). In addition to Erwinia extracellular pectate lyases, the multiple aHgnment indudes the Bacillus subtilis pectate lyase, Aspergillus tdger and E. carotovora pectin lyases and plant proteins. 

Digestion of PGA by the PelL enzyme yielded a mixture of unsaturated ohgogalacturonides, giving evidence that PelL is an endo-deaving lyase (17). An exo-enz3mie, such as the EC 16 PelX, would generate a single product (15). The PelL protein differs from the major E. chrysanthemi pectate lyases in its ability to cleave both PGA and methylated pectin (17). The PelL activity has a basic optimum pH and an absolute requirement for Ca + ions. Analysis of culture supernatants demonstrated that PelL is an extracellular enzyme, such as the other secondary pectate lyases (17). 

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