小麥胚芽(Wheat germ) 為小麥研磨時的副產品，含有高濃度的營養物質，但由於小麥胚芽中存在大量不飽和脂肪酸與高活性的脂解酶(Lipase, LA)與脂肪加氧酶(Lipoxygenase, LOX)，導致其製品容易出現酸敗味道而縮短其儲藏期限。浮動床乾燥加工具有良好的熱傳與質傳效能，曾用來乾燥小麥胚芽，然而，過高的乾燥溫度也可能減低其營養價值。因此本研究目的為探討浮動床中低溫乾燥條件對控制小麥胚芽的水活性及抑制LA與LOX活性之影響。實驗將兩公斤之小麥胚芽以直立批式浮動床乾燥機，調控入口溫度50、80和120℃以及入口風速度1.6 m/s和2.8 m/s，並測量乾燥後小麥胚芽之顏色、水份含量、水活性及酵素活性之變化。結果顯示，隨乾燥溫度的增加，小麥胚芽的亮度減弱、紅色度與黃色度提高，其亮度變化可做為乾燥加工的指標，且經浮動床乾燥處理可降低小麥胚芽的水份含量、水活性及LA與LOX活性。而80與120℃乾燥處理的小麥胚芽比50℃處理組有較低的酵素活性。另外，在相同乾燥溫度下，除了小麥胚芽之顏色與LOX活性外，浮動床乾燥之入口入風速度皆對實驗結果不具顯著性影響。整體而言，以120℃的乾燥溫度與入口風速2.8 m/s進行浮動床乾燥之小麥胚芽有較低之酵素活性，因能降低其水活性至0.3左右而有效達到抑制LA與LOX活性的目的。

Wheat germ (WG) is a by-product obtained from wheat milling and it contains highly concentrated nutrients. Due to large amounts of unsaturated fatty acids and the presence of highly activated lipase (LA) and lipoxygenase (LOX) in WG, WG products can easily turn into rancid flavor and shorten its shelf-life. The fluidized-bed drying is a good drying technique with good heat and mass transfer properties and has been used to drying WG. However, WG may reduce the nutritional value during high drying temperature process. The objective of this study was to investigate the effects of low (50 ℃) or medium (80 and 120 ℃) drying temperatures by fluidized-bed drying on controlling water activities and inhibiting LA and LOX activities in WG. The raw WG of 2 kg was dried with a vertical batch-type fluidized bed with following conditions, inlet air temperature of 50, 80 and 120 ℃, inlet air velocity of 1.6 m/s and 2.8 m/s. Changes in colors, moisture contents, water activities and enzyme activities of WG were determined. The decrease in the lightness can be an indicator of drying processing, because data showed that the lightness of WG decreased, while the redness and yellowness increased after drying. In addition, moisture contents, water activities and activities of LA and LOX of WG were all reduced after fluidized-bed drying processing. The enzyme activities in WG dried at 80 and 120 ℃ were lower than WG dried at 50 ℃. Except for the color and LOX activity, the inlet air velocity does not significantly affect the results under the same drying temperature. In conclusion, WG dried by fluidized-bed drying at 120 ℃ with inlet air velocity of 2.8 m/s possessed the lowest enzyme activities. In this drying condition, the water activity can reduced to about 0.3 and LA and LOX activities can be inhibited effectively in WG.