花生連續式流動層焙炒:乾燥機之設計與應用

Abstract

本研究設計、組裝一臺連續式流動層焙炒／乾燥機，並探討用於焙炒花生仁及帶殼花生之可行性。為能迅速加熱空氣，本設計採用瓦斯加熱器，配合空氣迴流管路，來得到高溫熱風及維持焙炒期間溫度之恆定。此外，另裝設一臺變頻器，調節熱風流速，以適當流動化具有不同表面密度之花生仁及帶殼花生。熱風上吹之焙炒區域寬15cm，長150cm。花生原料經由覆有金屬網之輸送帶送入焙炒區域，進行連續式流動層焙炒。為了增加焙炒均勻性，輸送帶上每隔15cm加裝一片隔板，使花生原料不會過早吹出焙炒區或滯留於焙炒區內。焙炒所得花生產品之焙炒香氣及鬆脆程度由5人品評小組以討論方式評定，以決定適當的焙炒條件。此外，測定焙炒後帶膜花生仁及脫膜花生仁之色澤（L、a、b值），與批式流動層焙炒／乾燥機所得產品之色澤比較，作為連續式流動層焙炒／乾燥機焙炒均勻性之指標。結果發現，運用瓦斯加熱器及空氣迴流管路，可在十分鐘內將焙炒空氣之溫度升高至200℃以上，與批式流動層焙炒／乾燥機比較，連續式流動層焙炒l乾燥機有較高的生產速度，且同樣可得焙炒均勻、品質良好之花生產品。帶生仁及帶殼花生產品之適當焙炒溫度／時間、組合分別為，花生仁185℃/5分鐘及200℃/3分鐘：帶殼花生185℃/19分鐘及200℃/7分鐘。 A continuous fluidized bed roaster/dryer was designed, assembled and tested for roasting peanut kernels and shell peanuts in this study. A natural gas burner was used for rapid heating and a recirculating loop was set up to obtain high temperature hot air and maintain constant temperature during roasting process. In addition, a frequency modulator was installed to adjust hot air velocity for appropriately fluidizing peanut kernels and shell peanuts which have different apparent density and dimensions. A porous conveyer was used to convey raw peanuts through a roasting zone in which continuously roasting of raw peanuts was carried out. The roasting zone is a rectangular-shaped opening (15 cm width and 150 cm length) through which hot air was blown up. To ensure roasting uniformity , partition plates were installed on the conveyer every 15 cm apart to prevent peanuts from blowing out too quickly or remaining in the roasting zone for a long time. Sensory evaluation of roasted products on roasting flavor and crunchness was conducted by a five member panel using the discussion method to determine the appropriate roasting conditions. In addition, color (L,a, and b value) of roasted peanut kernels with and without skin was measured, and compared with products roasted by a batch-type fluidized bed roaster to assess roasting uniformity. It was found that temperature of roasting air could be raised to above 200℃ within 10 minutes by using a natural gas burner and recirculating loop, and peanut kernels and shell peanuts could be roasted uniformly and rapidly using the continuous fluidized bed roasting method. The optimal roasting conditions for peanut kernels were 185℃/5 mm. and 200℃/3 mm.