فهرست مطالب رضا قزاق جاهد

Evaluation of the effect of ohmic pretreatments and blanching (enzyme removal) on changes in the biochemical properties of carrots was the purpose of this research in the drying process using the response surface method. Sliced carrot samples were added and left at 3, 5, and 7 minutes and 40, 60, and 80 volts. In the blanching pre-treatment, carrot samples were subjected to hot air from boiling distilled water for 5, 10, and 15 minutes to complete the pre-treatment process. This study dried slices of carrot samples at 360, 600, and 900 W using a microwave dryer. After drying, the amounts of antioxidant, total phenol, and flavonoid contents were determined. Then the results were analyzed using response surface methodology. The findings revealed that the high voltage and time in the ohmic pretreatment, as well as the time in the blanching pretreatment, had the lowest decreasing antioxidant content during the drying process. The lowest concentration of antioxidants was at the lowest voltage and time. Increasing the microwave power reduced the content of antioxidants, and lower drying powers had a higher antioxidant content in the dried samples. For the total phenol and flavonoid content in the ohmic pretreatment, the time and voltage of the pretreatment decreased their content, and increased power caused more total phenol and flavonoid content to be retained in the samples. Also, based on the optimization performed, the best microwave power was 360, 40 V ohmic voltage, and 3 minutes.

In this research, the carrot was first grounded in equal pieces; the pieces underwent pretreatment using Ohmic and blanching methods. The treatments were preheated at 3 ohmic voltage levels as 40, 60 and 80 Volt and 3 period levels of 2, 4 and 6 minutes. Then parameters examined in the pretreatment blanching in 3 period levels of 2, 4 and 6 minutes. After the pre-treatment, samples were dried in microwave in 3 power levels of 360, 600 and 900 W. The qualitative properties of samples including antioxidant, flavonoids and total phenol content were determined for pre-treated and dried samples. A multilayer neural network of perceptron was used to teach data using 3 and 6 neurons in the hidden layer and three functions of hyperbolic, sigmoid, and linear tangent activation. According to the results obtained from the network, for Ohmic premixing method the best values of R2 and RMSE were observed for antioxidant content (sigmoid-6 neuron), flavonoids content (hyperbolic tangent-6 neuron) and total phenol content (sigmoid-6 neuron). Also, the activation network with 3 neurons in the hidden layer and the hyperbolic tangent activation function were able to obtain the best values of R2 and RMSE for the total phenol content, flavonoids and antioxidants in the blanching pre-treatment.

In this research, carrots were first cut into equal pieces and then subjected to different treatments at different levels. The voltage levels were at 40, 60 and 80 volt in ohmic pretreatment and at 3, 5, and 7 minutes. The parameters studied in the blanching pretreatment included time, with different levels of 5, 10, and 15 minutes. Immediately after pretreatment, samples were dried in microwaves at 360, 600 and 900 watts. Finally, for each case of microwave dried and pretreated samples and their different levels, the energy efficiency values and their lost energy were calculated. According to the results, in the majority of cases, we see that increasing the amount of microwave power increases the energy efficiency, and subsequently, the lost energy decreases, so that the maximum value was 15.8797%. In the study of the effect of voltage in the ohmic pretreatment, a similar result was obtained, with the highest energy efficiency of 15.7061%. Also, in evaluating the effect of time parameter in ohmic pretreatments, it was observed that with increasing pretreatment time, the amount of energy efficiency was also increased and the energy lost was reduced, so that the highest amount of energy efficiency and the lowest amount of energy lost were respectively 15.7409% and 8.2358 MJ were measured.