Advisor(s)
Abstract(s)
Textural changes during fruit ripening have been attributed to pectin
degradation due to pectic enzymes such as pectinmethylesterase (PME, EC 3.1.1.11).
PME catalyzes the de-esterification of pectin, a complex mixture of polysaccharides,
namely methyl esterified polygalacturonic acid, with the release of hydrogen and
methanol, producing shorter chains causing drastic losses in firmness. Thus, control of
PME activity in fruits aiming at texture maintenance and/or improvement is
extremely important to the food industry. However, PME activity and properties are
dependent on product, environmental and physico-chemical conditions, such as pH
and temperature. Therefore, the aim of the present work was to optimize the pectinmethylesterase
(PME) enzyme assay from tomato (Solanum lycopersicum ‘Zinac’)
fruits, and determine its kinetics behavior and thermal stability. The highest PME
activity was found with a 1.0 M of NaCl extraction solution, with 0.5% citrus pectin,
and revealed optima of temperature at 60°C and pH of 8.8. The low kM value (0.011%)
for tomato PME describes the high affinity between enzyme and substrate (citrus
pectin), whereas the obtained Vmax value (0.712 U mg-1) relates to the enzyme quantity
present in the reaction. The study of PME thermal stability showed two distinct
behaviors: an increase of activity from 40 to 50°C and a decrease from 55 to 80°C. At
50°C/10 min an increase in activity up to 17% of activity was observed. At 60°C, about
50% of the activity still remained after heating for 25 min, and PME was completely
inactivated at 80°C after 10 min. Data obtained in the temperature range of 55 to
80°C were also satisfactorily described by an Arrhenius first-order kinetic model.
These results provide useful information about the different factors that affect tomato
PME activity and may be used as a tool for firmness control during postharvest
handling and fruit processing.
Description
Keywords
pH Temperature NaCl concentration Heat stability Quality
Citation
PINHEIRO, J. ...[et al.] - Optimization, Heat Stability and Kinetic Characterization of Pectin- Methylesterase Enzyme from Tomato (Solanum lycopersicum ‘Zinac’) Fruits. In XXVIII International Horticultural Congress on Science and Horticulture for People (IHC2010): International Symposium on Postharvest Technology in the Global Market, Lisboa, Portugal, 22-27 August, 2010 - ISHS Acta Horticulturae. ISSN 0567-7572. N.º 934 (2012), p. 1283-1290
Publisher
International Society for Horticultural Science