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JKFN Journal of the Korean Society of Food Science and Nutrition



Online ISSN 2288-5978

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Journal of the Korean Society of Food Science and Nutrition 2015; 44(10): 1492-1503

Published online October 31, 2015

Copyright © The Korean Society of Food Science and Nutrition.

Combination Effect of Various Freezing and Thawing Techniques on Quality and Nutritional Attributes of Onions

You-Kyoung Jung1, Min-Young Jang1, In-Guk Hwang2, Seon-Mi Yoo2, Sang-Gi Min1, Yeon-Ji Jo1, Ji-Yeon Chun3, and Mi-Jung Choi4

1Department of Bioindustrial Technologies and 4Department of Bioindustrial Food Science, Konkuk University; 2Department of Agro-food Resources, National Academy of Agricultural Science, Rural Development Administration; 3Department of Food Bioengineer

Abstract

This study evaluated the combination effect of various freezing and thawing techniques on the quality and nutritional aspects of onions. Onions were frozen by natural air convection freezing (NCF), air blast freezing (ABF), and liquid nitrogen freezing (LNF). Onions were frozen for 76 min by NCF, 9 min by ABF, and 9 min by LNF. The freezing treatment was stopped when the core temperature reached -12°C for NCF and ABF, and -120°C for LNF. Frozen samples were thawed through natural air convection thawing, running water thawing, sonication thawing (ST), or microwave thawing. The quality and nutritional aspects of frozen-thawed onions were evaluated by measuring thawing loss, pH, texture, water content, color, and SEM image. ST was found to cause the least loss in onion sample among the tested thawing methods, whereas the freezing methods did not cause any significant loss. In our experiment, thawing is found to be a more critical technique when compared to that of freezing. There were no clear quantifications or trends of pH and water content among different freezing and thawing techniques. The highest total color difference (ΔE) was observed in the NCF sample. For morphological observation, ABF gave the smallest ice crystal size, as well as minimum cell collapse. Loss of vitamin C, free sugar, and organic acid content was lower in the ABF and ST sample, when compared to other trials. In our study, we found that combination of ABF and ST could preserve the quality and nutritional aspects of frozen-thawed onions better than other methods.

Keywords: onion, individual quick freezing, air blast freezing, cryogenic freezing, thawing

Article

Article

Journal of the Korean Society of Food Science and Nutrition 2015; 44(10): 1492-1503

Published online October 31, 2015

Copyright © The Korean Society of Food Science and Nutrition.

다양한 냉・해동 방법에 따른 양파의 이화학적 특성 및 영양성분 변화

Combination Effect of Various Freezing and Thawing Techniques on Quality and Nutritional Attributes of Onions

You-Kyoung Jung*1, Min-Young Jang*1, In-Guk Hwang*2, Seon-Mi Yoo*2, Sang-Gi Min*1, Yeon-Ji Jo*1, Ji-Yeon Chun*3, and Mi-Jung Choi*4

*1Department of Bioindustrial Technologies and *4Department of Bioindustrial Food Science, Konkuk University; *2Department of Agro-food Resources, National Academy of Agricultural Science, Rural Development Administration; *3Department of Food Bioengineer

Abstract

This study evaluated the combination effect of various freezing and thawing techniques on the quality and nutritional aspects of onions. Onions were frozen by natural air convection freezing (NCF), air blast freezing (ABF), and liquid nitrogen freezing (LNF). Onions were frozen for 76 min by NCF, 9 min by ABF, and 9 min by LNF. The freezing treatment was stopped when the core temperature reached -12°C for NCF and ABF, and -120°C for LNF. Frozen samples were thawed through natural air convection thawing, running water thawing, sonication thawing (ST), or microwave thawing. The quality and nutritional aspects of frozen-thawed onions were evaluated by measuring thawing loss, pH, texture, water content, color, and SEM image. ST was found to cause the least loss in onion sample among the tested thawing methods, whereas the freezing methods did not cause any significant loss. In our experiment, thawing is found to be a more critical technique when compared to that of freezing. There were no clear quantifications or trends of pH and water content among different freezing and thawing techniques. The highest total color difference (ΔE) was observed in the NCF sample. For morphological observation, ABF gave the smallest ice crystal size, as well as minimum cell collapse. Loss of vitamin C, free sugar, and organic acid content was lower in the ABF and ST sample, when compared to other trials. In our study, we found that combination of ABF and ST could preserve the quality and nutritional aspects of frozen-thawed onions better than other methods.

Keywords: onion, individual quick freezing, air blast freezing, cryogenic freezing, thawing