Pectins stabilizer

Sejersen, M.T., Salomonsen, T., Ipsen, R., Clark, R., Rolin, C., Engelsen, S.B. (2007). Zeta potential of pectin-stabilized casein aggregates in acidified milk drinks. International Dairy Journal, 17, 302-307. 

The enzymes used for juice clarification are almost exclusively pec-tolytic. The reasons for the clarification effect are as follows. Pectin stabilizes the suspended solids in the juice. Through addition of the enzyme, the pectin is converted to a dissolved form and broken down. This is associated with a significant decrease in viscosity. In addition, pectins that have been made soluble act as protective colloids for many of the suspended particles. As soon as the protective effect of pectin is lost, these suspended particles coagulate and are precipitated. A significant decrease in viscosity is accompanied by a significant increase in filtration performance. 

Pectin is a thickener in many products. If there is sufficient sugar in the mixture, pectin forms a firm gel. Jams and jellies are thickened with pectin. Pectin binds water, and thus keeps products from drying out. It stabilizes emulsions. 

Pectin combines with the calcium and whey proteins of milk, stabilizing foams and gels made with cream or milk. 

The HM and LM pectins give two very different types of gels the mechanisms of stabilization of the junction zones in the two cases are described and few characteristics given. The different molecular characteristics (DE, distribution of methoxyl or acetyl substituents, neutral sugar content or rhamnose content) play an important role on the kinetic of gelation, mechanical properties of the gel formed and also on the experimental conditions to form the stronger gels. All these points were briefly discussed. 

The effect of the nature of the divalent cation is very pronounced as illustrated in Figure 2 on sample A30. Pectins were found to be much more sensitive to copper than to calcium. A scale of affinity towards divalent cations can be easily obtained this way [18]. This result corroborates what has been measured by pH titration upon addition of increasing amount of cations [28,29], where the order of decreasing selectivity was Pb = Cu Zn > Cd = Ni > Ca. This scale does not follow the size of the radius of the cations but is in agreement with the sequence of complex stability of Irving-Williams [30]. 

Pectins show great stability towards shearing. 

This test is based on a preselected amplitude for the applied strain (y) at a constant frequency (f) and a constant temperature (T). The method can be applied to test the stability of substances with temporary physical changes of structure or the course of chemical reactions like gelling at a given temperature. Again the pectin sols are filled into the measuring system... 

The chromatogram of the serum from juice with poor cloud stability obtained after mash treatment with the enzyme mixture including the pectin depolymerisation enzyme combination of polygalacturonase and pectin methyl esterase is seen to be lacking the A-peak. High molecular pectin is therefore considered to be a prerequisite for a cloud stable juice. 

Thermostable pectinesterases (TSPE), operationally defined as activity that survives 5 min at 70°C, contribute most to cloud loss in juices at low temperatures and juice pH (26). The percentage of total activity that is thermostable is highly variable and differs in kinetic properties, (22, 26), ease of solubilization (28, 29), stability to low pH (25) and stability to freeze-thaw cycles (23). Some of the variability in reported total PE and TSPE may be related to limitations of current methods to quantify activity. Any processing treatment or assay condition that increases cell wall breakdown or release PE from a pectin complex would enhance detection of total and TS-PE activity. Commercially, PE is inactivated by pasteurization in a plate heat exchanger or during concentration in the TASTE evaporator. 

Castaldo, D., Lovoi, A., Quagliuolo, L., Servillo, L., Balestrieri, C. and Giovane, A. 1991. Orange juices and concentrates stabilization by a proteic inhibitor of pectin methylesterase. J. Food Sci. 56 1632-1634. 

In the specialised literature is paid greater attention to the influence of alkali and alkali-earth cations on the stability of the pectin macromolecules in water solution. Lineweaver [3] reported that the stability of the pectin is increased in neutral or slightly acid media when the salts concentration in the solution is minimum. 

Pectinases find industrial application in the food-industry during the extraction and stabilization of juices. Grape must contains pectins that are frequently removed by the action of fungal pectinases. It would, however, be preferable to use Saccharomyces cerevisiae yeast strains that could produce pectinases. 

Additionnally, we show that the PG activity of the SCPP strain is regulated. It is stimulated by polyglacturonic acid concentrations similar to the ones seen in various fruit juices. On an industrial point of view, this induction would be diminished by the elevated glucose concentrations found in these fruit juices when compared to the pectin concentrations. Basal activities would be sufficient to eliminate all pectins and obtain juice stabilization. It would also have been interesting to study the effect of glucose concentrations of 15% and 20% (concentrations found in fruit juices, beers and ciders) on the PG activity of the SCPP strain. 

This novel enzyme was the only esterase able to release acetyl from sugar beet pectin and removed about 30% of the total acetyl groups present. It also caused the release of acetyl groups from a range of other acetylated substrates, either synthetic or extracted from plants, in small amounts. PAE had an apparent molecular weight of 60 kDa and showed optimal activity at pH 5.5 and a temperature of 50 C. The enzyme is sensitive to buffer composition and requires a bivalent cation for optimal activity and stability. In purified form this enzyme proved unstable, especially in phosphate buffers. 

In most plants, ice pop mixes are prepared cold and the hydrocolloid should be readily dispersible and soluble in cold mix. The hydrocolloid must be compatible with acid. Karaya gum (0.4%), locust bean gum (0.25%), and pectin (0.2%) were originally the stabilizers used. More recently CMC (0.25%),... 

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