Pectin/calcium gels

Melting temperatures (Tm) were determined for several LM pectin/calcium gels at different pectin and calcium concentrations. During the heating process of the gel. 

LM pectin/calcium gels (Cp = 4-8.5 g/L R = 0.3-0.5) 11-86 Temperature dependence of the shift factor required for time-temperature superposition of mechanical spectra (5-40=C). Gamier (1992) o a... 

Olive pomace dry matter produced by the two-phase system is a source of arabinan-rich pectic polysaccharides that should be exploited. They contain a diagnostic terminally-linked p-(l—>5)-arabinose residue in the a-linked backbone they are able to form elastic gels with calcium, which present syneresis for high calcium concentration and are more resistant to high temperature than commercially available low-methoxyl pectin/calcium gels. These properties make them valuable as food ingredients for specific applications. 

Fraeye, 1., Doungla, E., Duvetter, T, Moldenaers, R, Van Loey, A., and Hendrickx, M. (2009). Influence of intrinsic and extrinsic factors on rheology of pectin-calcium gels. Food Hydrocolloids, 23(8), 2069-2077. 

Much attention has been paid to the pectin-calcium system because of its application in the food industry as gelling agent. A large body of the litterature on this subject is devoted to the gel formation as function of calcium concentration, pH and temperature [1-8]. There were also some reports on the... 

Beaulieu, M., Turgeon, S.L., Doublier, J.-L. (2001). Rheology, texture and microstructure of whey proteins/low methoxyl pectin mixed gels with added calcium. International Dairy Journal, 11, 961-967. 

A different behavior is expected with thermoreversible gels. Using the LM pectin/calcium network as an example, the influence of temperature on SLR was... 

Lopes da Silva, J. A. L., Gonsalves, M. P., Doublier, J. L., and Axelos, M. A.V. 1996. Effect of galac-tomannans on the viscoelastic behaviour of pectin/calcium networks. Polymer Gels and Networks 4 65-83. 

LM pectin solutions gel only in the presence of divalent cations (only calcium ion is used in food applications, and almost all pectin is used as a food ingredient) which crosslink the poly-... 

Cardoso et al. [13] also compared the dependency of the viscoelastic properties of mature OPE/calcium gels upon the polymer and calcium concentrations to those of the LMP. They showed that, for these variables, both pectin systems exhibited a power law dependence of the G. At pH 7, for the different concentrations of non-esterified carboxyl groups available in the pectin (o-GalA ), the PPE/calcium and citrus LMP/calcium systems exhibited similar dependencies on the calcium concentration (Fig. 8a), with a power law dependence of 2.9-3.3. Still, the gelling ability of OPE/calcium systems was more dependent on the polymer concentration than the citrus pectin. For the different calcium concentrations tested, the corresponding exponents of power law dependency were approximately 3.0 and 1.9 for OPE/calcium and citrus LMP/calcium systems, respectively (Fig. 8b). These results also confirm the lower capability of the pectic olive extracts to form, under similar ionic conditions, elastically effective junctions zones. 

LM-pectin will gel only in the presence of divalent cations. Increasing the concentration of divalent cations (only calcium ion is used in food applications) increases the gelling temperature and gel strength. Divalent cations are unnecessary for the formation of a HM-pectin gel because of the low number of carboxylate groups that need to be bridged and because of the formation of hydrophobic areas parallel to the helix axes by a columnar stacking of methyl ester groups (15). 

The plant cell wall of wood is built up by the three components discussed above rigid, water-insoluble cellulose microfibrils, hemicellulose molecules, which are presumably fixated by hydrogen bonds on the fibril s surface, and pectin calcium salts, which form an aqueous connecting gel where side-arm carbohydrates act as hydrogen-bonded linkers (Fig. 4.2.25). 

Lopes da Silva J. A., Gongalves M. R, Doublier J. L., Axelos M. A. V. (1996). Effect of galactomannans on the viscoelastic behaviour of pectin/ calcium networks. Polvm. Gels Netw.. 4,65-83. 

The gel strength of pectin increases with the increase in the molecular weight of the pectin used thus, any treatment that leads to depolymerization of the pectin chains results in weaker gels [39]. Pectins can gel in different ways based on molecule type and structure. Acid or crosslinking with calcium ion, or reaction with alginate, can induce gelling of pectin [3]. 

Sriamornsak et.al [126] prepared chitosan - reinforced calcium pectinate (ChCP) beads by ionotropic gelation method. The swelling of ChCP gel beads and release behavior of indomethacin from the beads were investigated and compared with conventional calcium pectinate (CP) gel beads. 

Pectins are readily soluble in water to give viscous stable solutions. However, the importance of pectin to industry, in particular the food industry, is the abihty of its solutions to form gels with sugar (ca 65% soHds) and acid or calcium ion under suitable conditions (51). 

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