香蕉片的干制

實驗一 脫水香蕉片 一 一 實驗目的實驗目的 掌握蔬菜干制品的加工方法和設備 二 實驗原理二 實驗原理 本實驗的目的是研究香蕉熱風干燥過程中水分的傳遞現(xiàn)象 并觀測加工過程中褐變引起 的顏色變化 以探索生產高質量脫水香蕉制品所適宜的干燥技術 在干燥過程的初始階段 水分在潮濕的物料內自由移動在最后階段 殘留的水分在近乎干燥的物體內擴散 人們一般 將干燥過程視為兩個階段 即恒速干燥階段和減速干燥階段 從恒速干燥階段向減速干燥 階段轉變時的水分含量水分臨界含量 是每一物料在給定干燥條件的干燥特性 微波產熱是 由于食品中有水的存在 當含水量一定時 微波功率越高 產熱量越大 食品升溫越快 膨化時氣 泡產生也越快 食品內氣體壓力也越大 同時 干燥越快 過高的微波密度使生熱太快太高 不 利于控制 食品宜焦化 過低的微波密度使食品內氣壓太小 不利于膨化 三 材料與設備三 材料與設備 香蕉 檸檬酸 亞硫酸鈉 食鹽 玉米淀粉 蜂蜜 電熱恒溫烘箱 微波爐 砧 板 不銹鋼刀 小托盤 四 工藝流程四 工藝流程 原料驗收 浸泡 切片 漂白 干燥 分選 包裝 入庫 五 操作要點五 操作要點 1 原料驗收 香蕉 新鮮 無病蟲害或機械損傷 市售 2 干燥處理 A 常壓熱風干燥 a 將香蕉去皮 然后將其切成厚度約 2 3 mm 和 3 5mm 的薄片 b 稱取香蕉片 液固比 3 1 放入護色液冷浸 10min 將其放置在恒溫熱風干燥箱中 以 60 70 溫度進行干燥 直至安全水分 香蕉片含水量在 30 35 為了研究熱風溫 度對香蕉片質量的影響 對香蕉片進行熱風干燥實驗 設定熱風干燥過程的 0 1 2 3 4 5 小時測定含水率 c 繪制干燥速率曲線 評定其外觀質量品質 并對其營養(yǎng)物質進行分析 B 微波干燥 a 香蕉去皮 切成 2 3mm 和 3 5mm b 將適量香蕉片至于護色液冷浸 10min c 每次投料量為 120 g 分別測得不同厚度的蘋果片在中火下微波 0 2 4 6 8 分鐘 香蕉片的質量 以確定香蕉片的微波密度 3 評定產品外觀質量品質 并對其營養(yǎng)物質進行分析 4 平衡水分 烘干后的香蕉片稍冷卻后 立即裝人套有塑料袋的箱內 保持 1 2 天 使 干品內水分相互轉移 達到均衡 5 包裝 經過分選后進行包裝 每箱凈重為 20kg 內為尼龍袋包裝 外包裝為紙箱 采用水膠紙袋 密封箱口 六 質量標準六 質量標準 1 感官指標 脫水香蕉片為白色略淡黃 無深色 香蕉片濃郁 口感酥脆 香蕉片薄厚 大小應基本均勻 碎屑另行包裝銷售 2 理化指標 含水量小于 6 七 注意事項七 注意事項 1 整個加工過程中 切忌使用鐵器 銅容器 可用不銹鋼器具 2 脫水香蕉片成品為白色略淡黃 無深色 香蕉片成品的水分不得超過 6 3 貯藏成品香蕉蒜片必須在干燥 涼爽的庫房內 貯運過程中不得與有毒有害物質接觸 八 思考題八 思考題 1 香蕉片護色的原理 2 不同干制條件對香蕉片質量的影響 實驗序號干制方法溫度 時間香蕉片質量 1 熱風 烘箱 60 65 2 5h 255 6 7h 3 微波 4 冷凍干燥 Experiment 1 Dehydrated banana slice Experimental purpose Master the processing method and equipment of dried vegetables Experimental principle During drying fruit slices can undergo enzymatic and nonenzymatic darkening and visible color change is considered However diffusion is generally accepted as the principal mechanism of moisture transport in drying processes the moisture transfer phenomenon during banana drying and observe the color change caused by browning in processing to explore the production of high quality dehydrated banana products that were suitable to the drying technology In drying water molecules must make their way through the food product to the surface internal resistance to drying in contact with drying air Once at the surface water molecules are transfered into the air external resistance to drying based on the difference in vapor pressure between same value as the vapor pressure of water at the surface of the food drying ceases The rate of drying may be limited by either the rate of internal migration of water molecules to the surfaces or the rate of evaporation of water molecules from the surface into the air depending on the conditions of drying The initial period of constant rate drying is called the constant rate period or CRP once the critical moisture content is reached at later stages of drying the rate at which moisture migrates to the surface limits drying The rate of drying decreases this is called the falling rate period FRP Here drying rate depends on the moisture content remaining in the product Microwave energy offers several advantages compared to conventional heating methods including speed of operation energy savings precise process control and faster start up and shut down times However as microwaves penetrate within a food and generate heat internally their greater processing interest is the capacity to deliver energy within the product In thermal processing this means accelerated and more uniform internal heating and thus substantially decreased processing times which leads to higher product quality as the detrimental effects of high temperatures are minimised Other benefits include that microwave processing can also help control energy costs since heating takes place only in the food material being processed and not in the surrounding medium Materials and equipment Bananas citric acid sodium sulfite salt corn starch CMC honey electrothermal constant temperature oven microwave oven chopping boards stainless steel knife the small tray Process flow The check and acceptance of raw materials soaking slicing bleaching drying sorting packaging storage Operation points 1 The check and acceptance of raw materials Banana fresh no pests or mechanical damage commercially available 2 Drying process At ambient pressure drying The fruit was peeled manually and cut into slices of 2 3 mm and 3 5mm thick Slices were placed into glass jars filled with six times their weight of a sucrose solution solution and left for up to four hours of drying The syrup was mixed gently with a magnetic stirrer Sugarcane was of the first class commercial grade and pH was controlled by citric acid or calcium hydroxide solutions Three slices were removed from the batch every 30 min gently washed with distilled water to eliminate syrup from the surface and residual water was removed with tissue paper For the purpose of estimating the initial and final moisture contents banana samples from each experiment were dried in an oven at 60 for 3 4 h Banana samples were prepared from the fresh bananas and the dried bananas that had been dried in the kiln The empty containers were weighed before they were used The masses of the containers with the samples in them were measured before and after drying Drying curves Analysis of banana drying behavior using the concept of a characteristic drying curve The average moisture content of the dried bananas is plotted as a function of time Microwave drying The fruit was peeled manually and cut into slices of 2 3 mm and 3 5mm thick Slices were placed into glass jars filled with six times their weight of a sucrose solution solution and left for up to four hours of drying The syrup was mixed gently with a magnetic stirrer Sugarcane was of the first class commercial grade and pH was controlled by citric acid or calcium hydroxide solutions 3 Sensory evaluation 4 Balance moisture Dried banana chips after cooling slightly immediately loaded with plastic box keeping 1 2 days so that the moisture of dried food will be transferred to achieve equilibrium 5 Packaging After sorting then packaging it the weight of each box should be 20kg Inner space pack with nylon bag outer would package carton Use the glue water bag to seal the mouth Quality standard 1 Sensory index In the scores obtained for color texture taste crispness and overall impression Dehydrated banana slices are white and slightly yellowish no dark color Banana is full of flavor And taste crisp The thickness and size of Banana slice should be the basic uniform what s more the fragement should be packaged separately and then sale out 2 Physicochemical indexes moisture content should be less than 6 Attention 1 Slicing foods allows the dry air to circulate and dry the surface area of the food first Cut foods into 1 8 inch to