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KMID : 0380620140460020189
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Korean Journal of Food Science and Technology
2014 Volume.46 No. 2 p.189 ~ p.197
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Effects of Heat Treatment on the Quality of the Onion Juices Prepared with Sulfur-applied Onions
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Choi Bo-Gyoung
Surh Jeong-Hee
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Abstract
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Onion juices were prepared by various heat treatments (at 105-120oC for 4.5-5.5 h), from the onions cultivatedwith increasing numbers of sulfur applications (once for Sulfur-1, four times for Sulfur-4). As heat treatment intensityincreased, the onion juices darkened (p<0.001), which adversely affected the sensory preference. In addition, increasing theheating temperature significantly increased the organic acid content of onion juices (p<0.001), and therefore, decreased pH(p<0.001). Heat intensity did not affect the thiosulfinate content of onion juices, suggesting that the rate of decompositionof thiosulfinate into low-molecular weight sulfur derivatives is similar over the temperature range of 105-120oC. Totalflavonoids were higher in onion juices derived from Sulfur-4 than in Sulfur-1 onions, and increased with heat treatmentintensity (p<0.001). These results indicated that heat-facilitated conversion of bound forms of flavonoids to their free formsincreases the extractability of flavonoids from onions.
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KEYWORD
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onion, sulfur, heat, thiosulfinate, flavonoid
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