• Food Science and Preservation
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• v.21 no.2
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• pp.199-205
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• 2014

This study was conducted to investigate the physicochemical properties and antioxidant activity of black Doragi-apple juice to increase the utilization of Doragi, which is known as a high-functional horticultural crop. To prepare the black Doragi, it was steamed for 15 days at $60^{\circ}C$ and was then dried at $30^{\circ}C$ for 3 h. The five types of black Doragi-apple juice were prepared based on different mixing ratios of black Doraji extract, apple extract, and jujube extract. The mixing ratios of black Doraji extract, apple extract, and jujube extract were 3:3:1, 4:2:1, 2:4:1, 2:2:1, and 2:6:1 for samples A, B, C, D, and E, respectively. The pH and acidity of black Doragi-apple juice were within the ranges of 3.9-4.15 and 1.26-1.51%, respectively. Black Doraji-apple juice E showed the highest sugar content (9.33 $^{\circ}Brix$), reducing sugar content (85.05 mg/mL), and sugar content/acid ratio (6.98). Based on the sensory evaluation, sample C was most preferable in terms of color, taste, sugar-acid ratio, and overall preference, except for the flavor. Black Doragi-apple juice D showed a higher total polyphenol content (706 ${\mu}g/mL$) than sample C (586.22 ${\mu}g/mL$), but there was no statistically significant difference between samples C and D in terms of antioxidant activities. Therefore, it is suggested that the best mixing ratio of black Doraji extract, apple extract, and jujube extract for the production of the best black Doragi-apple juice with excellent taste and antioxidant activities is 2:4:1 (sample C).

• Food Science and Preservation
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• v.20 no.4
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• pp.510-517
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• 2013

This study was conducted to investigate the antioxidant and antimicrobial activities of the hot-water and methanol extracts of raw and black Doraji to increase its utilization. In order to prepare the black Doraji, it was steamed for 15 days at a temperature of $60^{\circ}C$ and then it was dried at a temperature of $30^{\circ}C$ for 3 hr. The methanol extract from the black Doraji (BM) contained the highest levels of total polyphenols among the extracts, and the total polyphenol content of the extract from a black Doraji was higher than that of the extract from a raw Doraji. The total flavonoid contents of the hot-water extract from a black Doraji (BW) was the highest (7.94 mgQE/g) among the samples. The DPPH and ABTS radical scavenging activities increased according to the increase in the concentrations of the Doraji extracts. The BM has the highest radical scavenging activity among the extracts. Each extract showed a slight difference in the antibacterial activity according to the tested strains. The Black Doraji showed a higher antimicrobial activity compared to the raw Doraji. The hot-water extracts demonstrated higher activities than the methanol extracts, and the BW revealed the strongest activity. In this study, the black Doraji showed more effect of the antioxidant and anti-microbial activities than the raw Doraji. These results will provide fundamental data for improving the sitological value and the black Doraji can be used as a valuable resource for the development of nutraceutical foods.