Background and Objectives: Proxidase enzyme is one of the most important enzymes in plant tissues, which can bind to hydrogen peroxide and produce an activated complex that can react with a wide range of donor molecules. Therefore, inactivation of the enzyme may increase the shelf life of raw and un-blanched frozen vegetables. In order to inactivate the enzyme methods such as heating, lowering pH or aw or adding chemical additives (SO₂) can be used; however, each of the above mentioned methods has a kind of shortcoming. Nowadays consumer's trend has been oriented to use fresh products or foods prepared by little process, therefore producers are interested in using alternative methods in order that increase the product’s shelf life.

Materials and Methods: In this study the effect of natural essential oils (Golpar, Thyme and Clove oils) on peroxidase enzyme activity was investigated. Optimization of peroxidase enzyme inactivation under different variables (essential oils concentration, the time of enzyme activity, blanching time and temperature) was performed using response surface methodology.

Results: The results showed that peroxidase activity of celery extracts was affected by all the studied oils and its activity was reduced. Optimum conditions for non-thermal inactivation of peroxidase enzyme of celery for different used oils were as: Golpar concentration 50 ppm, the time of enzyme activity 60 seconds, and enzyme activity (absorption) 0.467599; Thyme concentration 50 ppm, the time of enzyme activity 60 seconds and enzyme activity (absorption) 0.0523847; and clove oil concentration 50 ppm, the time of enzyme activity 60 seconds and enzyme activity (absorption) 0.120615.

Conclusion: This study showed that essential oils have the ability to inhibit and inactivate peroxidase enzyme activity.

Key­words: Essential oils, Anti oxidant, Peroxidase enzyme activity, Optimization, Response surface methodology

Background and Objectives: Different factors affect on the quality and quantity of oil content in fried products, of which frying time and temperature are two main factors. Also the effective role of hydrocolloids in reducing the oil absorption of fried products (food products) has been demonstrated in many researches but few studies have been done on the role of Aleo Vera gel in low fat fried products. Therefore, in this study, the effect of Aleo Vera gel concentration, frying time and temperature on the oil absorption and quality attributes of fried carrot chips wad investigated.
Materials and Methods: The effect of different concentrations of Aleo Vera gel as a hydrocolloid (0, 10 and 20% W/V), frying temperature (150, 170 and 190 ⁰C) and frying time (2, 4 and 6 minutes) on the oil absorption and quality attributes of fried carrot chips was optimized by response surface method. All the experiments were performed duplicate.
Results: The amount of water loss and oil absorption during frying was reduced with increasing of coating agent concentration. Also the moisture content of the sample was decreased by increasing the frying time and temperature, while oil absorption level was increased. The sensory evaluation results showed that the total acceptance of fried carrot chips increased when frying time and temperature increased, but decreased with the increasing the Aleo­ Vera gel concentration. Optimization results showed that the optimum processing conditions were frying time of 2 minutes, Aleo­ Vera gel concentration 6.94% and frying temperature of 182 ⁰C; in these conditions, the quality attributes of fried carrot chips were in optimum level.
Conclusion: Application of Aleo Vera gel coating can lead to produce low-fat fried carrot chips without adverse effects on sensory attributes of the final product.