Fruits and vegetables are perishable products due to their high water content and high enzymatic activity, and large amounts of them are deteriorated each year before consumption. Different methods such as the use of heat or chemical preservatives are common to reduce food waste, but increasing consumer demand for fresh or minimal processed foods has led to increased research for finding alternative preservation methods. In this study, the ability of clove, cumin and fennel essential oils (concentrations of 50, 75, 100 and 200 ppm) in reducing peroxidase enzyme activity (as one of the main factors of biochemical deterioration) in apple fruit was investigated. Clove essential oil in pure state and in concentrations of 100 and 75 ppm reduced 66.67% of the peroxidase enzyme activity while concentrations of 200 and 50 ppm of clove essential oil reduced 62.97 and 48.15% of the peroxidase enzyme activity in apple fruit respectively. Cumin essential oil in all applied concentrations led to a 66.67% reduction in peroxidase enzyme activity in apple fruit samples. Also, the use of concentrations of 100, 75 and 50 ppm of fennel essential oil has reduced 62.97% of peroxidase enzyme activity in apple fruit samples, while increasing the fennel essential oil concentration reduces its inhibitory effect on peroxidase enzyme activity so that the application of pure state and concentration of 200 ppm of fennel essential oil reduced 18.52 and 55.56% of peroxidase enzyme activity in apple fruit, respectively. The results of response surface optimization method showed that the lowest peroxidase enzyme activity for clove, cumin and fennel essential oils were obtained in essential oil concentration and enzyme activity time of 200 ppm and 40 seconds for clove essential oil, 146 ppm and 112 seconds for cumin and 130 ppm and 183 seconds for fennel essential oil respectively.

Keywords: Apple fruit, Natural essential oils, Peroxidase enzyme, Response surface method.

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