Calcium pectinate

In 65% sugar jellies the hydrogen bridges alone are active. Such gels are easily deformed and are elastic. In calcium pectinate gels, the most effective cross links are calcium ion bonds between the carboxyl groups. The bond distances are short therefore an inelastic, rather brittle, gel results. 

Enzymic de-esterification of the methyl esters of pectin proceeds linearly along the chain of the molecule, giving rise to blocks of free carboxyl groups.40-44 The same conclusion was reached on the basis of the high stability-constant of calcium pectinates prepared by par-... 

Rubinstein, A., and Rudai, R., In vitro and in vivo analysis of colon specificity of calcium pectinate formulations, Eur. J. Pharm. Biopharm., 41 291-295 (1995). 

Phosphates have the ability to combine with metal ions, such as calcium, magnesium, iron, and copper, and so render the metals nonactive. Calcium and magnesium arc primarily responsible for the hardness of water. The addition of tripolyphosphate or hexametaphosphale will hind these elements and produce soft water. In a similar manner, sequestration is used to soften the skins of fruits and vegetables for faster cooking, and to increase the extraction and recovery of pectin in fruit. Calcium pectinates, which are... 

Figure 6-8 Rate of Aging for Low-Methoxyl Pectin Gelled Systems Studied near the Pseudo Plateau Region (A) AG /A log t, against pectin concentration (0.1 mol L NaCl, pH 7) for different calciumipectin ratios C> R = 0.34 R = 0.42 = 0.54 (B) dG /dlogr, against the stoichiometric calcium pectin...

Another system was based on a swelling core tablet and a surrounding coating consisting of a combination of hydrophobic and hydrophilic polymers. The insoluble hydrophilic polymer, such as calcium pectinate or calcium alginate, was dispersed in the coating and served as a channel-former in order to control the water penetration. The core contained a swelling, but... 

In contrast, low-methoxy (LM) pectins gel in the presence of divalent cations, especially calcium, by the egg box mechanism proposed for alginates. Moreover, calcium pectinate gels prepared at neutral pH are heat stable, whereas acidic pH gels are thermo-reversible. Gel strength depends on the extent of esterification (levels from 30% to 50% are optimal), the distribution of ester groups on the chain, and the average molecular weight. LM pectins have been used traditionally in antidiarrheal formulations with kaolin. HM pectins were evaluated in controlled release matrix formulations. Pectin microspheres were reported to improve ophthalmic bioavailability of piroxicam in rabbits compared with commercial piroxicam eye drops. ... 

Pillay V, Fassihi R. In vitro release modulation from cross-linked pellets for site-specific drug delivery to the gastrointestinal tract. Part 2. Physicochemical characterization of calcium-alginate, calcium-pectinate and calcium-alginate-pectinate pellets. / Control Release 1999 59 243-256. 

The sodium and calcium activity coefficients were determined by specific electrodes, in dilute salt-free solutions (c < 10 equiv/I) of sodium and calcium pectinates. Results were compared to those calculated from Manning s theory (21). This model is proposed for infinitely dilute solutions of rodlike polyelectrolytes and the activity coefficients are directly imposed by the charge parameter ... 

In addition, the dependence of calcium activity coefficients upon the calcium pectinate concentration has been investigated. Solutions of pectinic acids of different concentrations were prepared, neutralized by calcium hydroxide and the resulting calcium salts were analyzed by potentiometry for the calcium activity coefficient. 

Samples with a DE higher than 50% have constant calcium activity coefficients over the concentration range tested (0.8 - 3 x 10 equiv/1). In contrast, pectins with lower DE are characterized by a calcium acti ity coefficient which is decreasing above a concentration of 10 equiv/1. Furthermore, the concentration in calcium pectinates has a profound influence on the calcium activity coefficient for samples with the lowest DE or for enzyme-deesterified pectins since the calcium activity coefficient decreases to zero. With higher concentration in pectins, (c > 3 x 10 equiv/1), a... 

Similar curves can be obtained for other samples and a generalization was tried. The acidic form of the pectins was taken as a reference since it was shown that only one conformation exists whatever is the level and pattern of esterification. In an other hand the degree of neutralization was substituted by the effective charge parameter (o x X ) by neglecting the autodissociation of the polyacid. A master curve can therefore be drawn where all the experimental points fall (Figure 5) and where the transition for the calcium pectinates occur for values of the charge parameter higher than... 

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. 

Aluminum salts precipitate all pectins, and this principle has been applied in the commercial production of pectins (8). The aluminum process as applied to high-methoxyl pectins accounts for over 1,000,000 pounds of powdered pectin per year, or about 15% of present production. On the other hand, the calcium process for low-methoxyl pectins is seldom used, perhaps because of lack of fundamental knowledge about calcium pectinates and the preference of industry for alcohol precipitation. 

In general, the source of pectic material, conditions of treatment, and general procedure for preparing the partially demethylated pectinates, prior to their precipitation and recovery as calcium pectinates, are practically identical with those previously described (17), except for the calcium precipitation. 

Procedure. The method of acid extraction and demethylation of pectin from apple pomace at 60 C. was essentially that previously described (17), up to the point of clarification of the pectin extract. Prior to clarification, the temperature of the extract was raised to about 50 C. in order to aid dispersion of the pectinates. Following the clarification and removal of starch, the pectin was precipitated as calcium pectinate by adding 20% calcium chloride solution to the extract at room temperature. The quantity of calcium chloride was such that any excess of the salt did not give a further precipitate after the precipitated material had stood from 1 hour to overnight as a practical handling procedure. After the calcium pectinate had been filtered off through muslin by hand, the relative completeness of precipitation was estimated by determining the relative viscosity (Ostwald at 26 C.) of the liquid pressed out. A relative viscosity of 1.2 or less indicated practically complete precipitation. 

The pectin was then wrapped in canvas and pressed in a Carver press at 10,000 pounds per square inch on the ram. The press cake was granulated and dried at 60° C. for 20 hours. The calcium pectinate was then ground to pass a 40-mesh screen and stored in a closed container for future evaluation. 

The calcium pectinate, as prepared, is insoluble in cold or hot water without added acid. Before it can be dispersed and utilized, use of acidified alcohol or treatment with a calcium sequestering or deionizing agent is necessary. 

Methods (4, IS) are available for treating calcium pectinate with acidified alcohol of such concentration that the ash constituents will be readily soluble while pectin will not be soluble. It is not necessary to remove all the calcium from the pectinate in order to disperse it in water. A calcium sequestering agent, such as sodium hexametaphosphate, when added to calcium pectinate will suppress the activity of the calcium ions, so that the pectinate can be dispersed. Pedersen (1I ) describes the use of sodium pyrophosphate to improve the solubility of low-methoxyl pectin in liquids containing calcium ions or other polyvalent metal ion. The result of this treatment is similar to that of sodium hexametaphosphate used by the authors. 

In order to evaluate the prepared calcium pectinates, they were subjected to the following acid-alcohol treatment. 

Twenty-five grams of calcium pectinate were treated with 100 ml. of acid-alcohol (65% isopropyl alcohol containing 3.5% hydrochloric acid) for 30 minutes with an electric stirrer at room temperature. The pectinate was then filtered on a sintered-glass filter using suction and washed with 50 ml. of 65% isopropyl alcohol. The pectinate was transferred to a beaker and 50 ml. of 65% isopropyl alcohol was added. pH was adjusted to 4.5, using ammonium hydroxide after the mixture had stood for at least 30 minutes. The pectinate was refiltered, washed with 50 ml. of... 

In Table I, the conditions of time, temperature, pH, and yields of the calcium pectinates prepared by the simultaneous acid-extraction and demethylation of pectin from apple pomace are presented, as well as the evaluation of the acid-alcohol treated calcium pectinates as to calcium pectate content, methoxyl content (expressed on the basis of 100% calcium pectate), relative viscosity, grade, and optimum pH. These data were obtained by methods described below in the order that they appear in the table. 

Yield of Calcium Pectinates. The recovery of calcium pectinates, based on the weight of pomace treated, ranged from 4.2 to 9.7%. 

The yields of the prepared calcium pectinates are somewhat lower than the alcohol-precipitated products prepared under similar conditions (17), as shown in Figure 1. Figure 1 presents only trends as to the yields of the pectinates, and the slope of the curves may change for various source materials of pectin. 

Calcium Pectate. Calcium pectate was prepared from the calcium pectinates by the method of Emmett and Carre (5) in amounts ranging from approximately 89 to 96%. The alcohol-precipitated products, prepared under similar conditions (17), ranged from approximately 72 to 90%. Hinton (7) has shown that calcium pectate can be used as a measure of the purity of a pectin. 

Methoxyl Content. The saponification method of von Fellenberg (, ff) was used to determine the methoxyl content, and the results in Table I are expressed on the basis of 100% calcium pectate for uniformity. The methoxyl content of the calcium pectinates prepared by acid de-esterification ranged from 3.1 to 6.4% Trend curves, showing a comparison of de-esterification as denoted by the methoxyl contents of the alcohol-recovered samples and calcium-precipitated samples, are presented in Figure 2. Under comparable conditions of pH and time of treatment, the methoxyl contents of the alcohol- and the calcium-precipitated samples prepared by acid de-esterification at 60 C. were similar. 

Relative Viscosity. The relative viscosities (Ostwald at 26 .) were determined on the acid-alcohol-treated calcium pectinates using 0.5% solutions at pH 4.5. Measurement of the relative viscosity at greater acidities than pH 4.5 was not... 

Table I. Conditions of Preparation, Yields, and Properties of Calcium Pectinates...

Grades ranged from 68 to 204 for the alcohol-precipitated pectinates, and from 92 to 244 for the comparable acid-alcohol-treated calcium pectinates. Trend curves in Figure 3 show that the calcium pectinates treated with acid-alcohol are superior in grade to the alcohol-precipitated products (17). The effect of the addition of calcium and sodium hexametaphosphate upon the grade of acid-alcohol-treated cal-... 

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