Background: The enzyme activity of peroxidise and polyphenoloxidase establish enzymatic browning and leading to undesirable changes in fruits and vegetables.

Objective: The aim of this study was to evaluate the effect of plant essential oils on reducing the activity of enzymes involved in enzymatic browning of broccoli.

Methods: Broccoli inflorescences were treated with distilled water (control), ascorbic acid (17 ppm) and concentration of 500, 750, 1000, and 2000 ppm of Pennyroyal, black Cumin and Cumin essential oils in both in vitro and in vivo, then peroxidase and polyphenol oxidase activity were evaluated.

Results: Cumin essential oil at 1000 ppm and all treated black Cumin essential oil under in vitro test as well as 500 ppm Pennyroyal essential oil, 500 and 750 ppm black Cumin essential oil, all treated cumin essential oil and ascorbic acid under in vivo test, significantly reduced peroxidase activity in Broccoli compared to control. Also, In vitro applied of essential oils including 500 ppm Pennyroyal, 500 ppm black Cumin, 2000 ppm Cumin and ascorbic acid treatment were dramatically decreased polyphenol oxidase activity in compare to control. The highest inhibition of polyphenoloxidase and peroxidase activities respectively were achieved using concentrations of 500 ppm and 750 ppm black Cumin essential oil in in vivo condition.

Conclusion: The essential oils used in these experiments depending on the concentration used reduced polyphenol oxidase and peroxidase activities in broccoli.