Pectinesterases microbial

The presence of salts of univalent and bivalent cations increases, by several-fold, the activity of pectinesterases from higher plants, which is minimal in the absence of salts.38,50,57,6, 63,64 66,69,7° The activating effect of salts on pectinesterases of microbial origin is not so great, an increase by 1.5- to 2-fold being reported.51 56,63 76-78,80 Table III shows the concentrations of sodium chloride and calcium chloride that caused the maximal activation of pectinesterases of plant and microbial origin. The mechanism of activation has not yet been satisfactorily explained. 

Among the microbial pectinesterases, the one from Coniothyrium diplodiella56 was purified by repeated chromatography on columns of Duolite A-2 and DEAE-cellulose. Two electrophoretically homogeneous forms of pectinesterase were obtained, having an identical pH optimum and the same behavior towards pectins of different d.e. 

Pectin methyl esterase in juices requires processing times of 10 min combined with pressures of 600 and 1000 MPa and temperatures of 57 and 20°C, respectively. These combinations prevent microbial deterioration, but must be combined with a mild blanching, refrigerated storage and addition of inhibitory enzymes to achieve a stable product with respect to pectin methyl esterase (Cheftel, 1992). Guava puree samples were treated with pressures of 400 and 600 MPa looking for pectinesterase and pol)q)henoloxidase inactivation. The residual activity of the former was greater than 76%, while of the latter was above 63% at the lower pressure. 

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