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Kinetics properties of polyphenol oxidase in hawthorn (Crataegus spp.)

100%
Saeidian S.
International Letters of Natural Sciences
|
2014
|
tom 20
Polyphenol oxidase (PPO) from hawthorn was extracted and partially purified through (NH4)2SO4 precipitation, dialysis and ion exchange chromatography. The activity of polyphenol oxidase was investigated in Crataegus spp. Spectrophotometric method was used to assay the enzyme activity and the kinetic constants - maximum enzyme velocity (Vmax) and Michealis - Menten constant (Km). Of the substrates tested, catechol was the best substrate for PPO with a Km value of 2.2 mM. The optimum pH for PPO activity was found to be 7. The enzyme showed high activity over a broad pH range of 4 - 8. The optimal pH and temperature for enzyme activity were found to be 7 and 40-45 °C, respectively. km value for hawthorn PPO is calculated 22 mM for catechol and 6.7 mM for pyrogallol and 9.7 mM for L-dopa. As can be seen, affinity of PPOs for various substrates varies widely. The enzyme showed a broad activity over a broad pH and temperature range. The thermal inactivation studies showed that the enzyme is heat resistant. The enzyme showed the highest activity toward pyrogallol and no activity toward tyrosine. Of the inhibitors tested, the most potent inhibitors were kojic acid, cysteine and glycine , respectively.
2

The possibility of thermal inactivation of Alicyclobacillus acidoterrestris spores in fruit and vegetable juices

84%
Chmal-Fudali E. E., Papiewska A. A.
Biotechnology and Food Science
|
2011
|
tom 75
|
nr 1
3

The effect of microwave and conventional heating on the activity of proteolytic enzymes isolated from broad bean [Vicia faba] seeds - short report

67%
Baraniak B., Czuba A.
Polish Journal of Food and Nutrition Sciences
|
2001
|
tom 10
|
nr 3
The aim of the presented study was to evaluate the changes of the activity of proteolytic enzymes connected with albumin fraction of proteins in frozen horse bean seeds subjected to thermal processing in microwave heater and blanching. The process lasted 2, 4, 6, or 8 minutes. The power of 0.35, 0.5, 0.6, 0.75 and 0.9 kW at 2.450 MHz frequency was used in microwave heater by Philips/Whirlpool (M606 model). Changes occurring due to temperature impact in whole seeds and after peeling were observed. The proteolytic enzyme activity in whole seeds was higher than that in peeled ones and it amounted to 2.75 and 1.82 units/g, respectively. In both cases, temperature caused gradual decrease of the protease activity. Inactivation process was greater along with the time course and increased power of microwaves applied. Enzymes extracted from whole seeds were much more inactivated both after blanching and microwave action. Their activity decreased by 82% after 6-minute operation using 0.9 kW microwaves, while activity of enzymes extracted from peeled seeds decreased by 73% at the same time period and due to the same factor.
4

Znaczenie kwasowosci srodowiska podczas wyjalawiania

51%
Iciek J., Blaszczyk I., Papiewska A.
Przemysł Fermentacyjny i Owocowo-Warzywny
|
2005
|
tom 49
|
nr 11
31-33
The results of the works over thermal inactivation of the Bacillus stearothermophilus spores are presented in the paper. The inactivation process was performed in the water milieu with the presence of the citric acid. The influence of the citric acid on the sprout and growing of the spores was analyzed. Before this process the spores were stored in the sterilization temperature.
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