Abstract
Pectin methylesterase (PME) hydrolyzes methyl ester groups in pectin chains to form carboxylic groups, releasing methanol and H3O+. The aim of this study was to determine PME activity in samples of pectinases by UV-VIS spectroscopy, to measure the acid and methanol produced in the reaction of pectin with pectinase and to verify the thermal inactivation of exogenous PME in mango juice. The activity of PME in samples of pectinase was determined by potentiometry, UV-VIS spectroscopy, and by the action of alcohol oxidase. The reaction showed greater activity at pH 4.0 to 4.5 and at a temperature of 45° C. PME activity determined by UV-VIS spectroscopy with bromophenol blue indicator showed a good correlation with the activity determined by potentiometry and with alcohol oxidase. The results showed that bromophenol blue indicators can be used to determine PME activity in samples of pectinases where the optimum pH is located in the acidic range. The thermal inactivation of exogenous PME in mango juice occurred at 75° C for 20 min of exposure.
Highlights
Pectin methylesterase (PME), EC 3.1.1.11, is an enzyme that acts mainly in the hydrolysis of methyl ester groups in pectin chains to form carboxylate groups, releasing methanol and H3O+ (JAYANI et al, 2005)
According to Duvetter et al (2005) for samples of commercial pectinases obtained from Aspergillus aculeatus and Aspergillus niger the PME optimum pH was 4.0 to 4.5
The PME activity in the pectinase samples was determined in the presence of bromophenol blue indicator
Summary
Pectin methylesterase (PME), EC 3.1.1.11, is an enzyme that acts mainly in the hydrolysis of methyl ester groups in pectin chains to form carboxylate groups, releasing methanol and H3O+ (JAYANI et al, 2005). According to Zocca et al (2007) reaction of pectin with PME in the presence of an appropriate indicator at the optimum pH for the enzyme activity can be monitored by UV-VIS. A study showed that PME activity can be determined with an indicator dye known as bromocresol green (CECI; LOZANO, 1998). Klavons e Bennett (1986) showed that an alcohol oxidase can be used for methanol oxidation and subsequent reaction with 2,4-pentanedione. Mangos e Haas (1997) determined PME activity in reactions with pectin and the methanol released was oxidized by alcohol oxidase
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