應用灰色田口法於茶葉真空乾燥最適化之研究

乾燥為茶葉製造必要之製程，茶葉乾燥的方式以熱風乾燥為多數，使用真空乾燥仍不普遍。但真空乾燥相較於熱風乾燥，具有低溫乾燥可達較快的乾燥速度及獲得較佳的乾燥品質之優點，因此有其應用之潛力。本研究利用灰色田口法，探討滾筒式茶葉真空乾燥機之最適化操作參數，以乾燥溫度、壓力及滾筒轉速為控制因子，採用三因子三水準之L9直交表進行茶葉真空乾燥試驗及分析。研究結果顯示，田口法結合灰關聯分析可找出茶葉真空乾燥多重品質特性之最適化參數組合。由變異數分析可知溫度為影響乾燥效率及乾燥品質之最重要因子。以驗證試驗評估最適化參數之有效性，與原始參數比較，其乾燥效率及乾燥品質之信號雜音比（S／N），分別提升0.23dB及0.57dB，綜合效益提升0.02dB，顯見所找出的最適化參數對於茶葉乾燥有進一步的改善效果。因此，應用灰色田口法於解決茶葉真空乾燥之多重品質特性決策的問題，為可行之方法。

關鍵字

茶葉；真空乾燥；田口法；灰關聯分析

並列摘要

Tea drying is a necessary process of tea manufacturing. Although hot-air is commonly used in most tea drying methods, the vacuum drying has potentials to improve tea quality and efficiency in drying. In this study, the Grey-Taguchi method was used to conduct experiments to decide optimal operating parameters for the tea vacuum dryer. The drying temperature, pressure and rotation speed were used as the control factors, and the three factors and three levels of L9 orthogonal array were used for the tea vacuum drying experiments and analyses. The results show that the Grey-Taguchi method could find the optimal parameters of multiple quality characteristics of tea vacuum drying; and from the ANOVA, the temperature was the most important affecting factor of drying efficiency and quality. The verification experiments were confirmed the optimal parameters by the evaluation of signal to noise ratio (S/N), which the S/N ratio of drying efficiency and drying quality were increased 0.23dB and 0.57dB respectively, and the total efficiency increased 0.02dB, compared to the original parameters. The found optimization parameters could further improve the performance of tea vacuum dryer. Therefore, the Grey-Taguchi method is a feasible method for the study of multiple quality characteristics in tea vacuum drying.