Degree of pectin esterification

Additionally, the content of free and total acids as a measure of the degree of pectin esterification was investigated (Fig. 2). The amounts of both free and total acids were increased in the transgenic plants. However, their ratios are not significantly affected when both plant lines are compared (Fig. 2). 

It was established by Braudo and coworkers (1998) that an increase in the degree of pectin esterification leads to a greater extent of pectin association in aqueous solution (an increase in Mw). This is illustrated in Figure 6.7. The strength of the attractive interactions between the polysaccharide associates increases with the degree of pectin esterification, as reflected in the lowering of the value of the second virial coefficient. 

The possibility that the initial degree of methyl-esterification might be controlled by the properties of the methyltransferase enzymes was examined partial characterisation of these enzymes in suspension-cultured cells of fiax. Pectin methyltransferases beii enzymes characteristic of the Golgi apparatus [22], microsomes were fiactionated daily for ten days from suspension-cultured flax cells and incubated in the presence of C-SAM, the universal donor of methyl groups. 

Thus pectins in muro contain most elements of the cable model but have additional features due to esterification (acetyl- as well as methyl-) and branching. The ionic junction zones are similar to those of calcium pectate gels in vitro but also contam methyl-esterified junctions, and most of the single chains probably have a relatively high degree of methyl-esterification. 

N. O. Maness, J. D. Ryan, and A. J. Mort, Determination of the degree of methyl esterification of pectins in small samples by selective reduction of esterified galacturonic acid to galactose, Anal. Biochem., 185 (1990) 346-352. 

Fig. 10.15. Dependence of the lifetime of a foam from apple pectin solution on the degree of its esterification k curve 1 - with apricot juice added curve 2 - with morello-cherry juice added.

Materials. Commercial citrus pectins with degree of methyl esterification (DM) 35, 58-60, and 70 were gifts from Bulmers Limited, Hereford, England. Two other citrus pectin samples DM 37 and 72-73 were manufactured by Bulmers but were gifts from Drs. E. R. Morris and M. J. Gidley at Unilever. The DM 57 citrus pectin was a gift... 

Pectins are probably the most complex polysaccharides known, in terms of their chemistry and are certainly so in terms of their biosynthesis. Classically they were regarded as al,4-galacturonans, with various degrees of methyl esterification, and the terms pectic acid and pectinic acid referred to the non-esterified and partially esterified forms respectively. A third term protopectin , was used of insoluble pectin that could not be extracted from plant cell walls by hot solutions of chelating agents. It was considered that these three classes of pectin constituted a pectic triad . This view is now known to be erroneous, but it is still frequently put forward, especially in botanical texts. Consequently any discussion of the synthesis of pectins must be prefaced by a description of their chemistry, as it is now understood. 

MexPec 1200, MexPec 1400, and MexPec 1500 which had which had degrees of methyl esterification of 65%, 71%, and 74% respectively were obtained from Grindsted Products, Kansas City, KS, and were used as received. The MexPec 1500 was a lime pectin, while the other two materials were identified as citrus pectins. 

According to Mesbahi et aL (2005), long periods of direct boiling (T>90°C) during the extraction of pectin can result in the hydrolysis and degradation of pectin. Canteri-Schemin et al. (2005) extracted and characterized the pectin from apple pomace and obtained 17.82 % (d.m) of yield when the extraction conditions were 100 °C, 153 minutes and nitric acid concentration 6.2 % (w/v) the esterification degree of pectin extracted was 68.84 %. Marcon (2004) got a similar result, the yield of extraction was 16.80 % (d.m) when the extraction conditions were 100 °C, 80 minutes and the nitric acid concentration 5 % (w/v). 

Pectins are subdivided according to their degree of esterification (DE), a designation of the percent of carboxyl groups esterified with methanol. Pectins with DE >50% are high methoxyl pectins (HM pectins) [65546-99-8]-, those with DE <50% are low methoxyl pectins (LM pectins) [9049-34-7]. 

The source materials were commercial pectins apple A30 and citrus pectin C73 kindly supplied by Unipectine (France) and Copenhagen Pectin Factory (Denmark) respectively. Polygalacturonic acid samples (named SR) were obtained by acid hydrolysis of a fully de-esterified citrus pectin as previously described [24]. Citrus pectins with different degree of esterification (DE) were obtained by controlled acid de-esterification [8]. 

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]. 

Smooth regions contain esterified and unesterified blocks but also regions with randomly distributed methyl groups. How are these generated What is the exact degree of esterification of the pectins exported into the apoplast ... 

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