RT info:eu-repo/semantics/conferenceObject
T1 Polyphenol Oxidase (PPO) and Pectin Meth ylesterase (PME) inactivation by means of High Pressure Carbon Dioxide (HPCD)
A1 Benito Román, Oscar
A1 Sanz Díez, Mª Teresa
A1 Illera Gigante, Alba Ester
A1 Melgosa Gómez, Rodrigo
A1 Beltrán Calvo, Sagrario
K1 PPO
K1 PME
K1 juice
K1 Supercritical Carbon Dioxide
K1 green process
K1 food technology
K1 Ingeniería química
K1 Chemical engineering
AB HPCD is a promising technology to inactivate the enzymes responsible for the juice spoilage, such as PPO and PME. Inorder to understand the mechanism that induces this inactivation, a study using two commercial enzymes (PPO frommushroom and PME from Aspergillus niger) was carried out. The effect of pressure, temperature, exposure time and ratioCO2/enzyme ratio loaded in the reactor were studied. The experimental results (residual activity) were fitted to a kineticmodel that served to develop a complete kinetic study: the kinetic constants, activation volume and activation energy werecalculated, as well as the pressure and temperature sensitivity parameters (ZP and ZT, respectively). The changes in thetertiary structure of the enzymes after different treatments were analyzed by fluorescence spectroscopy running differenttests: 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 similarinactivation pattern was observed: a sudden decrease in activity (more than 75% of the total activity loss was observedwithin the first 2 minutes) was followed by a slowed decay. At constant temperature, higher inactivation rates were observedthe 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 and27-40°C, respectively.In the case of the commercial PME, the use of supercritical CO2 (pressure 60-180bar, temperature 40-55°C and times up to75 minutes) increased dramatically the PME inactivation rate, showing that pressure had a limited effect on PME inactivationbut temperature had an important effect. The pressure and temperature sensitivity parameters (ZP and ZT) confirmed thattrend, being in the range from 276 to 450bar and 8.7°C, respectively. The experimental data fitted the first order model andthe 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 thatratios higher than 3 did not improve the inactivation kinetics, being a waste of CO2 from the economic point of view. Bellowthat critical value, the inactivation of the enzyme strongly depended on pressure and temperature. In both cases thestructure of the enzyme was dramatically affected after exposure to HPCD, as revealed by the fluorescence spectroscopyanalysis that showed significant changes in the tertiary structure of the enzyme, which were compatible with the losses inactivity observed.
YR 2018
FD 2018
LK http://hdl.handle.net/10259/5081
UL http://hdl.handle.net/10259/5081
LA eng
NO Trabajo presentado en: 6th International Congress on Green Process Engineering (GPE 2018), 3 a 6 de junio de 2018, Toulouse
NO Spanish Governme nt (MINECO) and the European Regional Development Fund (ERDF) for financial support ofproject CTQ2015-64396-R and A.E. Illera’s contract. To Junta de Castilla y León and ERDF for financial support of projectBU055U16 and O.Benito-Román’s Post-doctoral contract
DS Repositorio Institucional de la Universidad de Burgos
RD 23-nov-2024