• Microbiology and Biotechnology Letters
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• v.39 no.2
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• pp.153-160
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• 2011

In this study, we have developed taste and other functional enhancements of yam chips, from tasteless and flavorless yam slices, through the process of soaking freeze-dried yam in different commercially available juices, including apple, omija (fruit of Maximowiczia typica), grape, wild grape, orange, tomato, red ginseng, and black garlic juice. The analyses of color (brightness, redness and yellowness), pH, brix, acidity, total polyphenol, total flavonoids, total sugar and reducing sugar, DPPH and ABTS scavenging activity, reducing power and nitrite scavenging activity, of the different yam chips showed that the freeze-dried yam slices absorb various components of fruit juices, such as flavonoids, sugars, organic acids and flavors, during the soaking process. These changes resulted in increased taste (both sweet and sour tastes), flavor and antioxidant activity in the yam chips. The soaking time for yam slices in juice is considered to be a crucial factor for the taste and bioactivity of yam chips. In the case of grape juice-yam chips, which had the highest preference among the 8 different chips, the optimum soaking time was noted as 120 seconds. The optimization of the soaking process is necessary for various juices. These results suggest that taste, and other functional enhancements, in yam chips can be developed by juice-soaking and freeze-drying methods.

• Food Science and Biotechnology
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• v.14 no.5
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• pp.661-666
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• 2005

The specific objectives of this study were to dry yam chips using microwave vacuum drying, freeze drying and hot air drying, then to coat the dried yam chips with ascorbic acid cocrystallized sucrose, and finally to compare the quality of yam chip snack foods with respect to drying and coating characteristics. The microwave vacuum dried sample showed the highest drying rates and much less surface damage than the hot air dried one did. The shape and color of the microwave vacuum dried/coated sample were allocated between those of the freeze dried/coated sample and the hot air dried/coated sample. The freeze dried/coated sample scored excessively low in organoleptic hardness and chewiness to be suitable as a snack. The hot air dried/coated sample was too deep in color, wrinkled, excessively high in organoleptic hardness and chewiness, and excessively low in mouthfeeling. Therefore, the microwave vacuum dried/coated sample presented the best overall attributes as a snack, with respect to organoleptic characteristics, shape, color, and drying rates.

• Microbiology and Biotechnology Letters
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• v.39 no.2
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• pp.146-152
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• 2011

In the course of a study in relation to the production of taste, and functional enhancements in root crop chips, which were prepared by soaking dried yam slices in fruit juices, we investigated the physiological characteristics and biological activities of 8 different commercially available juices including; apple, omija (fruit of Maximowiczia typica), grape, wild grape, orange, tomato, red ginseng and black garlic juice. The average water contents, pH, brix and acidity of the juices used were $85.59{\pm}5.80%$, $3.90{\pm}0.64$, $12.19{\pm}4.70%$, and $0.49{\pm}0.19%$, respectively. The polyphenol content of black garlic and grape juice were 1.50 and 1.21 mg/ml, respectively, and those were higher than the average content (0.57 mg/mL) of the juices. Evaluation of anticoagulation activity showed that only omija juice has a strong thrombin inhibition, which is comparable to that of aspirin (1.5 mg/mL). Omija, grape and orange juice all exhibited antibacterial activity, but no antifungal activity. The 8 different juices, and in particular grape and black garlic juice, showed strong antioxidant activity in DPPH and ABTS radical scavenging activity assays, with wild grape juice demonstrating potent nitrite scavenging activity. These results suggest that omija, grape and black garlic juice can be used as soaking solutions to produce taste, and other functional enhancements, for root crop chips.