科研之友
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摘要
Drying is the most common postharvest process to preserve medicinal and aromatic plants. Peppermint has a high worldwide commercial value. Newly harvested peppermint plants were dried by using four different drying air temperature profiles. They were constant 35 degrees C, constant 55 degrees C, incremental rises from 35 degrees C to 55 degrees C in four hours, and in eight hours. The samples were dried down to the final moisture content for 8 to 18.5 hours. The fastest drying was obtained with the use of the constant 55 degrees C and the slowest drying was obtained with the use of the constant 35 degrees C. The incremental rise of drying air temperature profile from 35 degrees C to 55 degrees C within 4 hours shortened the drying time by 46 %. Page's equation excellently represented all drying curves. Maximum color change and essential oil loss occurred with the drying at 55 degrees C; however, incremental rise of drying air temperature over time reduced the extent of color change and essential oil loss. The highest essential oil change was -21.95 % for the constant 55 degrees C, the lowest essential oil change was -2.32 % for the constant 35 degrees C. The temperature of heated air affected the composition of peppermint essential oil. Drying at constant 55 degrees C kept menthol content (43.31 %) close to that (47.64 %) of fresh peppermint but decreased menthone content (26.24 %) and increased cineol content (8.18 %). Considering the length of drying time and dried product quality values, the profile in which the drying air temperature rise within 4 hours was found to give the best results.
- 出版日期2016
