Study of the effect of thyme essential oil on the reduction of peroxidase enzyme activity in black Spanish radish and green bean

Enzymes in plant tissues can have undesirable or desirable effects on the quality of fruits and vegetables; therefore management of their change in fruits and vegetables is one of the concerns in food industry. Nowadays consumer's trend has been oriented to use fresh products or foods prepared by little process, therefore producers are interested the ways to increase shelf life by alternative methods. The aim of this work was to study the ability of thyme (Thymus vulgaris L.) essential oil in reduction of peroxidase enzyme activity (as an important biochemical degradation factor) in the black Spanish radish and green bean. For this purpose, plant extract containing peroxidase enzyme was mixed with a substrate mixture composed from guaiacol, hydrogen peroxide, sodium phosphate buffer and different concentrations of thyme essential oil (50, 75, 100 and 200 μg/100 ml). The absorbance of the samples was measured at 470 nm for 400 seconds spectrophotometrically. Results of this study showed that the peroxidase enzyme activity in the black Spanish radish and green beans were 4625 and 51 (gram of vegetable × second / unit of activity) respectively and by addition of thyme essential oil in the above concentrations the peroxidase enzyme activity of black Spanish radish was 2655, 2550, 2015 and 2162 (gram of vegetable × second / unit of activity) respectively and the peroxidase enzyme activity of green bean was 708, 6/551, 579 and 690 (gram of vegetable × second / unit of activity) respectively.