Lv 5
暱稱 asked in 社會與文化語言 · 2 decades ago



In drying, the object also is to remove water with minimum damage to the food.

Whereas evaporators will concentrate foods twofold or threefold, driers will take foods very close to total dryness in many cases less than 2% or 3% water. Driers are used to prepare such well-known products as dried milk powder and instant coffee. Although food traditionally has been dried to preserve it from spoilage and to reduce its weight and bulk, some foods are dried as convenience items and for their novelty appeal; an example has been freeze-dried fruits for cereals. Drying, as well as several of the other unit operations, is treated in detail in later chapters, and so only a few brief comments are needed here.

Liquid foods such as milk and foods in chunk form like shrimp or steak may be dried. It is generally much easier to dry liquid foods because these are easier to subdivide, either as a spray or a film, and in a subdivided form, the moisture can be removed more quickly.

Subdivision of a liquid is the principle behind the widely used spray drier (Fig. 5.10).

Liquid food such as milk, coffee, or eggs is pumped into the top of the large tower, at which point the liquid is atomized by a spray nozzle or equivalent device. At the same time heated air is introduced to the tower. The heated air in contact with the fine droplets of food dries the droplets, and dehydrated particles fall to the bottom of the

Tower and are drawn off into collectors. The moisture removed during drying is exhausted separately. Most commercially dried liquid foods are made this way.

Drying by subdividing food as a thin film is commonly done on a drum or roller drier of the kind illustrated in Fie. 5.11. The drum is heated by steam from within,

and the applied laver of food flashes off its moisture on contact with the heated drum.

The dried food is then mechanically scraped from the drum with long knives. Mashed

Potatoes, tomato puree, and several milk products are frequently dried this way.

Small food pieces such as peas and diced onions can be dried by moving them through a long tunnel-oven, and many types are in use. However, overheating and shrinkage in the course of water removal may give poor quality products in the case of particularly many kinds of vacuum freeze-driers. In all types the food pieces first are frozen and then dehydrated under vacuum from the frozen state. The ice dos not melt but under the conditions of high vacuum goes off directly as gaseous water vapor, a process known as sublimation. This very gentle kind of drying protects all food quality attributes such as texture, color, flavor, and nutrients. Freeze-drying is by no means restricted in its use to solid and particulate foods. Brewed coffee and quality juice products are dehydrated by freeze-drying.



3 Answers

  • 2 decades ago
    Favorite Answer





    使用液態細分的廣泛原則是利用噴霧乾燥器。(Fig. 5.10)液態食物像是牛奶、咖啡或是蛋汁,脫水的方法是藉由噴霧的噴嘴或是利用相同功能的裝備,使其原子分裂,並在同時間,將熱空氣打入。當熱空氣接觸到食物因脫水後產生的水滴時,脫水後的顆粒就會落在塔的底端,然後就集中收集。在脫水的過程中,濕氣的移除是個別分開的。大部分市面上的乾燥液態食品都是利用此方式脫水的。

    利用細分食物的脫水像是薄片,大部分是用滾軸或是鼓狀物的裝備做成的(Fie. 5.11)。鼓狀物的裝備是利用水蒸氣在裡面加熱,而食物去除水分仍有亮澤也是因藉由加熱的鼓狀物裝備。然後脫水食物會被在鼓狀物裝備上的長刀子無情地刮破。混和馬鈴薯、番茄濃湯、以及多種牛奶製品是以此種方式製造的。


    Source(s): 自己
  • 2 decades ago

    烘乾 在乾燥, 對象並且將取消水以對食物的極小的損傷。但是蒸發器將集中食物兩重或三倍, 烘乾機將採取食物非常緊挨總乾燥在許多情況下少於2% 或3% 水。烘乾機被使用準備如此知名的產品像奶粉粉末和速溶咖啡。雖然食物傳統上被烘乾保存它從損壞和減少它的重量和大塊, 一些食物被烘乾當便利項目和為他們的新奇呼籲; 例子是被冰凍乾燥的果子為穀物。烘乾, 並且數其它單位操作, 詳細被對待在最新章節裡, 並且那麼唯一幾個簡要的評論必要這裡。 液體食物譬如牛奶和食物在大塊形成像蝦或牛排也許被烘乾。它一般更加容易烘乾液體食物因為這些更加容易細分, 或作為浪花或影片, 並且以被細分的形式, 濕氣可能迅速被取消。 液體的細分是原則在廣泛被應用的浪花烘乾機(圖5.10 之後) 。液體食物譬如牛奶、咖啡, 或蛋抽入大塔的上面, 到時液體由噴嘴或等效設備霧化。同時激昂的空氣被介紹給塔。激昂的空氣與食物聯繫美好的小滴烘乾小滴, 並且被脫水的微粒下跌對塔的底部和撤退入收藏家。濕氣被取消在乾燥期間分開地被用盡。最商業乾液體食物被製作這樣。 烘乾由細分食物作為薄膜共同地完成在種類的鼓或路輾烘乾機被說明在Fie 。5.11 。鼓被蒸汽加熱從內, 並且食物應用的紫菜閃動它的濕氣在聯絡與激昂的鼓。乾食物機械上然後被刮從鼓與長的刀子。土豆泥、蕃茄純汁濃湯, 和奶製品頻繁地被烘乾這樣。 小食物片譬如豌豆和切成小方塊的蔥可能被移動烘乾他們通過一個長的隧道烤箱, 並且許多型是在使用中。但是, 過度加熱和收縮水撤除其間可以特別給質量差產品在許多种真空freeze-driers 情況下。在所有型食物片首先是凍結和然後脫水在真空之下從凍結狀態。冰dos 不是融解而是在高真空的條件下去直接地作為氣體水蒸氣, 過程以昇華著名。這种非常柔和的乾燥保護所有食物質量屬性譬如紋理、顏色、味道, 和營養素。冰凍乾燥絕不被制約在它的用途對堅實和屬於顆粒的食物。釀造的咖啡和質量汁液產品由冰凍乾燥脫水。

  • 烘乾

    在乾燥, 對象並且將取消水以對食物的極小的損傷。

    但是蒸發器將集中食物兩重或三倍, 烘乾機將採取食物非常緊挨總乾燥在許多情況下少於2% 或3% 水。 烘乾機被使用準備如此知名的產品像奶粉粉末和速溶咖啡。 雖然食物傳統上被烘乾保存它從損壞和減少它的重量和大塊, 一些食物被烘乾當便利項目和為他們的新奇呼籲; 例子是被冰凍乾燥的果子為穀物。 烘乾, 並且數其它單位操作, 詳細被對待在最新章節裡, 並且那麼唯一幾個簡要的評論必要這裡。

    它一般更加容易烘乾液體食物因為這些更加容易細分, 或作為浪花或影片, 並且以被細分的形式, 濕氣可能迅速被取消。

    液體的細分是原則在廣泛被應用的浪花烘乾機之後(圖 5.10).

    液體食物譬如牛奶, 咖啡, _ 或蛋是抽入這上面這大塔, 到時液體由噴嘴或等效設備霧化。 同時激昂的空氣被介紹給塔。 激昂的空氣與食物聯繫美好的小滴烘乾小滴, 並且被脫水的微粒下跌對底部

    聳立和撤退入收藏家。 濕氣被取消在乾燥期間分開地被用盡。 最商業乾液體食物被製作這樣。

    烘乾由細分食物作為薄膜共同地完成在種類的鼓或路輾烘乾機被說明在Fie 。 5.11. 鼓被蒸汽加熱從內,


    乾食物機械上然後被刮從鼓與長的刀子。 搗碎

    土豆, 蕃茄純汁濃湯, 並且幾奶製品頻繁地被烘乾這樣。

    小食物片譬如豌豆和切成小方塊的蔥可能被移動烘乾他們通過一個長的隧道烤箱, 並且許多型是在使用中。 但是, 過度加熱和收縮水撤除其間可以特別給質量差產品在許多种真空freeze-driers 情況下。 在所有型食物片首先是凍結和然後脫水在真空之下從凍結狀態。 冰dos 不是融解而是在高真空的條件下去直接地作為氣體水蒸氣, 過程以昇華著名。 顏色, 味道, 並且營養素。 冰凍乾燥絕不被制約在它的用途對堅實和屬於顆粒的食物。 釀造的咖啡和質量汁液產品由冰凍乾燥脫水。

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