2026-07-11T07:23:37Zhttps://riubu.ubu.es/oai/requestoai:riubu.ubu.es:10259/50812022-04-20T12:29:24Zcom_10259_4244com_10259_5086com_10259_2604col_10259_4569
Repositorio Institucional de la Universidad de Burgos
author
Benito Román, Oscar
author
Sanz Díez, Mª Teresa
author
Illera Gigante, Alba Ester
author
Melgosa Gómez, Rodrigo
author
Beltrán Calvo, Sagrario
2019-03-20T12:46:10Z
2019-03-20T12:46:10Z
2018
http://hdl.handle.net/10259/5081
HPCD is a promising technology to inactivate the enzymes responsible for the juice spoilage, such as PPO and PME. In
order to understand the mechanism that induces this inactivation, a study using two commercial enzymes (PPO from
mushroom and PME from Aspergillus niger) was carried out. The effect of pressure, temperature, exposure time and ratio
CO2/enzyme ratio loaded in the reactor were studied. The experimental results (residual activity) were fitted to a kinetic
model that served to develop a complete kinetic study: the kinetic constants, activation volume and activation energy were
calculated, as well as the pressure and temperature sensitivity parameters (ZP and ZT, respectively). The changes in the
tertiary structure of the enzymes after different treatments were analyzed by fluorescence spectroscopy running different
tests: intrinsic fluorescence measurement, KI quenching and ANS binding experiments.
In the case of PPO, the experimental results revealed that this enzyme inactivation kinetics fitted the two fraction model,
which indicates the presence of labile and stable isoenzymes. Exposure time (2 to 15 minutes), temperature (25 to 45°C)
and pressure (50 to 200bar) were the studied experimental conditions that led to different physical states for the CO2 (gas,
liquid and supercritical). Despite the different experimental combinations of pressure and temperature tried, a similar
inactivation pattern was observed: a sudden decrease in activity (more than 75% of the total activity loss was observed
within the first 2 minutes) was followed by a slowed decay. At constant temperature, higher inactivation rates were observed
the higher the pressure, obtaining an almost complete inactivation at 200bar after 5 minutes regardless the temperature.
When temperature was increased, much faster inactivation rates were observed. ZP and ZT were in the range 69-78bar and
27-40°C, respectively.
In the case of the commercial PME, the use of supercritical CO2 (pressure 60-180bar, temperature 40-55°C and times up to
75 minutes) increased dramatically the PME inactivation rate, showing that pressure had a limited effect on PME inactivation
but temperature had an important effect. The pressure and temperature sensitivity parameters (ZP and ZT) confirmed that
trend, being in the range from 276 to 450bar and 8.7°C, respectively. The experimental data fitted the first order model and
the inactivation kinetics study of PME was completed with the calculations of the activation energy and volume of activation.
The ratio CO2/volume of enzyme (g/mL) loaded in the reactor was found to be critical for both enzymes. It was seen that
ratios higher than 3 did not improve the inactivation kinetics, being a waste of CO2 from the economic point of view. Bellow
that critical value, the inactivation of the enzyme strongly depended on pressure and temperature. In both cases the
structure of the enzyme was dramatically affected after exposure to HPCD, as revealed by the fluorescence spectroscopy
analysis that showed significant changes in the tertiary structure of the enzyme, which were compatible with the losses in
activity observed.
eng
PPO
PME
juice
Supercritical Carbon Dioxide
green process
food technology
Polyphenol Oxidase (PPO) and Pectin Meth ylesterase (PME) inactivation by means of High Pressure Carbon Dioxide (HPCD)
info:eu-repo/semantics/conferenceObject
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URL
https://riubu.ubu.es/bitstream/10259/5081/1/Polyphenol_oxidase%20_%28ppo%29.pdf
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URL
https://riubu.ubu.es/bitstream/10259/5081/3/Polyphenol_oxidase%20_%28ppo%29.pdf.txt
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Polyphenol_oxidase _(ppo).pdf.txt