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ABSTRACT
Wasabi (Eutrema yunnaense) is a popular, commonly known as a specially health and a very precious flavoring food, which is served together with other foods, such as sushi and sashimi throughout the world. Isothiocyanate is the major flavor substance of wasabi which is extremely volatile, thus affecting the quality of wasabi products. The aim of this study was to obtain wasabi with the highest isothiocyanate content as well as other physicochemical and nutritional characteristics. Wasabi samples were dried by four different drying methods including, hot air-drying (HD), radio frequency-assisted hot air-drying (RFD), pulse-spouted microwave-assisted freeze-drying (PSMFD), and freeze-drying (FD). After drying, color, odor, taste, volume shrinkage, sensorial analysis, water content, and distribution as well as chlorophyll, ascorbic acid (vitamin C), and isothiocyanate content of the final dried products were measured. The drying time of each drying method was also measured. Highest contents of vitamin C, chlorophyll, and isothiocyanate of wasabi were obtained by FD followed by PSMFD. The volume shrinkage of wasabi dried by FD was the largest, followed by PSMFD, RFD, and HD, which is 0.992, 0.988, 0.894, and 0.882, respectively. The best color, highest sensorial scores, and small discrepancy (difference) of odor and taste substances from fresh samples of drying wasabi were obtained by freeze-drying which were close to PSMFD samples. As for drying time, RFD lasted 4.5 h compared to HD which lasted 9.5 h. PSMFD took 4.5 h less than FD (9 h).