Degree of esterification

Sucrose reacts with fatty acids to produce esters with degrees of esterification (DE) from 1 to 8 and hydrophi1 ic /Iipophi1 ic balances that provide them with numerous appHcations. Primary producers are Japan and the Netherlands, with total production at 6000 t/yr. Sucrose esters are nontoxic and biodegradable, and are approved for use in the EC, Japan, and the United States. 

The partially alkoxylated chlorotitanates, (RO) TiCl, can be prepared in high purity by reaction of TiCl with an organosilane ester, Si(OR)4 (see Silicon compounds). The degree of esterification of the titanium can be controlled by the amount of silane ester used. When is 3 or 4, the addition of the appropriate alcohol and an amine receptor is required (5). 

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]. 

One recent report involving the use of the in vitro digestion procedure noted that the micellarization of zeaxanthin from digested foods was dependent on its degree of esterification with transfer efficiency levels of 80, 44, and 11%, respectively, for the free form, monoesters, and diesters of zeaxanthin." In vivo studies" " ... 

Alkaline hydrolysis (saponification) has been used to remove contaminating lipids from fat-rich samples (e.g., pahn oil) and hydrolyze chlorophyll (e.g., green vegetables) and carotenoid esters (e.g., fruits). Xanthophylls, both free and with different degrees of esterification with a mixture of different fatty acids, are typically found in fruits, and saponification allows easier chromatographic separation, identification, and quantification. For this reason, most methods for quantitative carotenoid analysis include a saponification step. 

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 ... 

The most conspicuous concentrations of calciiun in the cell-walls of the flax hypocotyl were in the epidermal and subepidermal layers, especially at the tricellular junctions (figure 13 D), where these were filled with pectic polymers [67], Open tricellular jimctions with intercellular spaces had smaller areas of calcium accumulation where the walls of each pair of cells diverged. These sites were occupied by relatively linear pectic polymers with a low degree of esterification, which could be visualised with gold-kbeUed endopolygalacturonase [68] and were extractable by chelation of calcium with CDTA. Similar pectic polymers are located in the corresponding sites in other plant tissue, as established by susceptibility to polygalacturonase... 

Thixotropic behaviour of pectins can be observed with the drop of their degree of esterification, and with the onset of a distinct reactivity towards divalent cations. The common measuring principal is pictured in figure 3. 

The dynamic Weiflenberg number of pectin gels is influenced by the raw material used for pectin extraction and by the degree of esterification of the applied pectin. With a decreasing degree of esterification the dynamic WeiBenberg number also decreases. 

Analytical methods. The anhydrouronic acid content (AUAC), degree of esterification (DE), degree of amidation (DA) and ash content were determined according to the methods described in Food Chemical Codex II ed [5]. 

Quantitative Vibrational Spectroscopy on Pectins. Prediction of the Degree of Esterification by Chemometrics... 

The importance of the degree of esterification (%DE) to the gelation properties of pectins makes it desirable to obtain a fast and robust method to determine (predict) the %DE in pectin powders. Vibrational spectroscopy is a good candidate for the development of such fast methods as spectrometers and quantitative software algorithms (chemometric methods) becomes more reliable and sophisticated. Present poster is a preliminary report on the quantitative performance of different instrumentations, spectral regions, sampling techniques and software algorithms developed within the area of chemometrics. 

For this spectroscopic investigation 98 amidated pectin samples were provided by Copenhagen Pectin A/S (Hercules Inc.). The samples are spanning a degree of esterification between 20 and 55 per cent and a degree of amidation between 4 and 24 per cent (see Fig. 1). The powder samples were all measured as is without any form of pre-treatment such as drying and dilution. 

Figure 3. Loading (left) and score (right) plots from a PCA on chemical data measured on the pectins (%DE=degree of esterification, %DA=degree of amidation, %DFA=100-%DE-%DA, Transp=transparency, Cal-Ca4 and SAG are gel strength measures).

The optimal spectroscopic PLS models for the degree of esterification of amidated... 

The degree of esterification of the methyl ester of PGA was determined acidimetrically after hydrolysing the ester with sodium hydroxide [6]. 

For a univalent counterion the charge density parameter X was found to be A = 1.551a where a value of 7 = 1.06 was employed because of the degree of esterification of the methyl ester of PGA ( 5.34 per cent). A comparison of calculated and experimental values of i,pK -pKl) at different degrees of dissociation is shown in Fig. 2. For pK the values from Table 2 were used. 

Methods of analysis. The polyuronic acid content (PUAC) and the degree of esterification (DE) were determined according to Owens et al (10). 

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