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KMID : 1024420140180040293
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Food Engineering Progress
2014 Volume.18 No. 4 p.293 ~ p.299
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Effects of Air Blast Freezing and Microwave Thawing on Physicochemical and Nutritional Properties of Carrots
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Jung Kyung-Hun
Jo Yeon-Ji
Hwang In-Guk
Yoo Seon-Mi
Choi Mi-Jung
Min Sang-Gi
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Abstract
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This study was carried out to observe the effects of various combinations of air blast freezing and microwave thaw-ing on the physicochemical and nutritional properties of carrots. Carrots were cut into 0.5×0.5×5cm cubes and thenfrozen at -40oC at various freezing rates (0.2, 0.4 or 1.6oC/min) until a -12oC central temperature in the carrot wasreached by using an air blast freezer. Then, the frozen carrots were thawed by using natural air convection andmicrowaves at 200, 400, and 800 watts. After the thawing treatment, physicochemical properties of the carrots suchas pH, thawing loss, hardness, color, morphological images and changes in nutritional compositions were also ana-lyzed. In physicochemical characterization, thawing loss and hardness decreased with increasing the freezing rate.In morphological observation, ice crystal pore sizes in frozen carrots were 0.7, 0.3 and 0.1mm at 0.2, 0.4 and1.6oC/min, respectively. They significantly decreased as the freezing rate increased. For the nutritional characteriza-tions, the vitamin C and organic acid contents did not differ depending on the freezing rate. The sucrose contentwas the highest at the 0.2oC/min freezing rate. Therefore, we suggest that a faster freezing rate is effective to main-tain frozen food quality by minimizing tissue damage and changes in physical properties.
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KEYWORD
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Individual quick freezing, Microwave thawing, Physicochemical, Nutritional
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