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AbstractDue to the perishable nature of food, especially vegetables, and the need for long-term storage, freezing is one of the best methods to preserve food, and thawing is often required to use frozen products. The purpose of this study was to use the combined method of defrosting using hot air-infrared radiation on the quality characteristics of defrosted cooked carrot samples. At first, after cutting, the carrot samples were cooked at 75 °C for 30 minutes, and after placing the thermocouple inside the samples, they were frozen at -18°C for 48 hours. Then, the effect of defrosting parameters including air temperature (30 and 40 °C), air velocity (0.5 and 5 ms-1) and infrared power (100 and 300 W) on the quality characteristics of defrosted cooked carrots was investigated and the sample thawed at 25 °C was considered as a control samples. Using this method, the thawing time for the control sample was reduced from 47 min to 6.11 min in the optimal conditions, The minimum amount of ascorbic acid was 2.63 mg100 g-1 for treatment 1 and the maximum for treatment 6 was 5.78 mg100 g-1 . The amount of beta-carotene in the control sample was 29.21 mg100 g-1 in the minimum condition and 49.33 mg100 g-1 in the optimal condition. The highest amount of loss due to defrosting belonged to treatment 8 by 18.32% and the lowest amount belonged to the control sample by 44.7%. The use of combined infrared-hot air method is very suitable for defrosting cooked carrots and in addition to reducing the duration of defrosting, it maintains the quality of the product to a great extent. This method is very cost-effective and its investment and setup costs are small and can be used for various products.

Introduction: Due to the perishable nature of food, especially vegetables, and the need for long-term storage, freezing is one of the best methods to preserve food, and thawing is often required to use frozen products. The purpose of this study was to use the combined method of defrosting using hot air-infrared radiation and the interaction effect of temperature, air velocity and infrared radiation source power on the quality characteristics of defrosted cooked carrot samples. Materials and Methods: At first, after cutting, the carrot samples were cooked at 75 °C for 30 minutes, and after placing the thermocouple inside the samples, they were frozen at -18°C for 48 hours. Then, the effect of defrosting parameters including air temperature (30 and 40 °C), air velocity (0.5 and 5 ms-1 ) and infrared power (100 and 300 W) on the quality characteristics of defrosted cooked carrots was investigated and the sample thawed at 25 °C was considered as a control sample. Increasing temperature, power of radiation and air velocity had a significant effect on thawing time, ascorbic acid, beta-carotene and thawing lost and pH (P≤0.05). Results and Discussion: Using this method, the thawing time for the control sample was reduced from 47 min to 6.11 min in the optimal conditions. The minimum pH was 5.49 for treatment 1 and the maximum for treatment 6 was 6.28. The minimum amount of ascorbic acid was 2.63 mg100 g-1 for treatment 1 and the maximum for treatment 6 was 5.78 mg100 g-1 . The amount of beta-carotene in the control sample was 29.21 mg100 g-1 in the minimum condition and 49.33 mg100 g-1 in the optimal condition. The highest amount of loss due to defrosting belonged to treatment 8 by 18.32% and the lowest amount belonged to the control sample by 44.7%. Conclusion: The use of combined infrared-hot air method is very suitable for defrosting cooked carrots. In addition to reducing the duration of defrosting, it maintains the quality of the product to a great extent. This method is very cost-effective and its investment and setup costs are small and can be used for various products. [ABSTRACT FROM AUTHOR]