【発明の詳細な説明】[Detailed description of the invention]
〔産業上の利用分野〕
本発明は、塩や糖等の溶質がとけ込んでいる液
状物質を塊状に凍結し、その塊状の凍結品を真空
乾燥する液状物質の凍結乾燥方法に関する。
〔従来の技術〕
一般に、液状物質は濃度が均一なものでも凍結
すれば表面と内部とで濃度差が生じやすく、特に
凍結品の表面に濃度の高い部分が形成されると、
乾燥の際の水蒸気放散抵抗が増大し、凍結乾燥を
困難にしていた。そこで、従来では凍結乾燥を容
易にするために、凍結乾燥に際し、凍結品の表面
に０℃程度の水を滴下して表面濃度を低下させた
り、側面及び底面を保温しながら凍結させて表面
に溶質の濃度の高い部分を形成しないようにする
方法等が行われていた。
〔発明が解決しようとする問題点〕
しかし、上記従来の方法においても、特に塩あ
るいは糖などの溶質の濃度の高いみそや果汁等の
液状物質を凍結乾燥すると、溶質濃度の高い被乾
燥物体の表面が発泡して多孔状になり、商品価値
が無くなる虞があつた。
本発明の目的は、液状物質の凍結乾燥を容易に
すると共に、塩あるいは糖などの溶質の濃度の高
い液状物質であつても乾燥時に表面が発泡しない
ようにして、塊状の乾燥物を得る方法を提供する
事にある。
〔問題点を解決するための手段〕
本発明における液状物質の凍結乾燥方法の特徴
手段は、凍結品の表面に凹部を多数形成した後、
真空乾燥して塊状の乾燥物を得ることにあり、そ
の作用効果は、次の通りである。
〔作用〕
つまり、表面に凹部を多数形成してある塊状の
凍結品は、たとえ表面に溶質濃度の高い部分が形
成されたとしても、溶質濃度の低い部分が外部に
連通している凹部内の空間に露出しているので、
内部蒸気の外部への放散が助長され、容易に乾燥
できると共に、溶質濃度の高い表面部分を通つて
外部へ放散される水蒸気量が大幅に減少するの
で、たとえ溶質濃度の高い液状物質を凍結乾燥し
たとしても、乾燥物の表面に発泡現象を生じさせ
ずに、乾燥物を塊状に維持したまま真空乾燥でき
ることを実験的に確認できた。
〔発明の効果〕
従つて、液状物質の溶質の濃度に関わらず、表
面が多孔性になる等の荒れが少なく、良好な品質
の塊状の凍結乾燥品が短時間でえられ、品質の向
上と製造コストの低減化を一挙に図れるに至つ
た。
〔実施例〕
次に、本発明の実施例を図面に基づいて説明す
る。
第１図に示すように容器４に液状物質を入れて
凍結室５内に位置させ、タンク６から凍結室５内
に供給される液体窒素により冷却されて液状物質
が凍結した後、液状物質からなる凍結品Ａを容器
４から取り出して、その表面に第２図に示すよう
に、金具で掻き削ることによつて深さ１mm以上巾
0.5mm以上の溝Ｂを、縦横に適当間隔隔てて複数
本形成し、その複数の溝Ｂによつて表面層が破ら
れ、且つ、外部に露出する表面積が増大した凍結
品Ａを、第３図に示すようにトレイ７に載置して
密閉及び開放自在な乾燥室１を形成するタンク１
ａ内に入れ、乾燥室１を密閉する。そして、低温
トラツプ２を作動させて、約−40℃の冷媒を冷却
装置２ｂによつて冷却管２ａに供給し、真空ポン
プ３を作動させて、乾燥室１内の圧力を減圧状態
に維持すると共に、トレイ７に対して互いちがい
に位置する状態で乾燥室１内に並設した加熱板８
を備えた加熱装置９によつて、凍結した被処理物
中の氷を昇華させ、水蒸気を低温トラツプ２で捕
捉しながら乾燥を行う。
〔別実施例〕
前記溝Ｂを凍結品Ａの表面に形成する以外に、
液状物質を凍結する時、あるいは、凍結前に底面
が波型あるいは山型の凹凸面を有する容器４ａに
入れて凍結し（第４図イ）、凍結後、容器４ａの
底面形状と同形に形成された凍結品Ａの底面を上
方に向け（第４図ロ）、外部露出表面を増大させ
ても良い。
尚、前記各実施例の実験結果を、次の表に示
す。
[Industrial Application Field] The present invention relates to a method for freeze-drying a liquid substance, which involves freezing a liquid substance in which solutes such as salts and sugars have been dissolved into a lump, and vacuum-drying the frozen lump. [Prior Art] In general, even if a liquid substance has a uniform concentration, when it is frozen, a difference in concentration tends to occur between the surface and the inside, and especially when a high concentration area is formed on the surface of a frozen product,
The resistance to water vapor dissipation during drying increased, making freeze-drying difficult. Conventionally, in order to make freeze-drying easier, water at around 0°C is dropped onto the surface of the frozen product to lower the surface concentration, or the sides and bottom are kept warm while freezing. Methods have been used to prevent the formation of areas with high solute concentrations. [Problems to be Solved by the Invention] However, even in the conventional method described above, when freeze-drying a liquid substance such as miso or fruit juice that has a particularly high concentration of solutes such as salt or sugar, the drying object with a high solute concentration There was a risk that the surface would foam and become porous, resulting in loss of commercial value. The object of the present invention is to facilitate the freeze-drying of liquid substances, and to obtain dry lumps by preventing the surface from foaming during drying even when liquid substances have a high concentration of solutes such as salt or sugar. The goal is to provide the following. [Means for Solving the Problems] The characteristic means of the method of freeze-drying a liquid substance in the present invention is that after forming a large number of recesses on the surface of a frozen product,
The purpose of this method is to vacuum-dry to obtain a dried mass, and its effects are as follows. [Effect] In other words, for a frozen solid product with many concave portions formed on its surface, even if a portion with a high solute concentration is formed on the surface, a portion with a low solute concentration will remain in the concave portion communicating with the outside. Because it is exposed to space,
This facilitates the dissipation of internal vapor to the outside, making it easier to dry, and the amount of water vapor dissipated to the outside through the surface area with high solute concentration is greatly reduced. However, it was experimentally confirmed that vacuum drying could be performed without causing any foaming phenomenon on the surface of the dried material and while maintaining the dried material in the form of a block. [Effects of the invention] Therefore, regardless of the concentration of solute in the liquid substance, a block-like freeze-dried product with less roughness such as porosity on the surface and good quality can be obtained in a short time, resulting in improved quality. This made it possible to reduce manufacturing costs all at once. [Example] Next, an example of the present invention will be described based on the drawings. As shown in FIG. 1, a container 4 is filled with a liquid substance, placed in a freezing chamber 5, and after being cooled and frozen by liquid nitrogen supplied from a tank 6 into the freezing chamber 5, the liquid substance is removed from the container 4. Take out the frozen product A from the container 4 and scrape the surface with a metal tool to a depth of 1 mm or more as shown in Figure 2.
A frozen product A, in which a plurality of grooves B of 0.5 mm or more are formed at appropriate intervals vertically and horizontally, the surface layer is broken by the plurality of grooves B, and the surface area exposed to the outside is increased, is As shown in the figure, a tank 1 is placed on a tray 7 to form a drying chamber 1 that can be sealed and opened.
a and seal the drying chamber 1. Then, the low temperature trap 2 is activated to supply refrigerant at approximately -40°C to the cooling pipe 2a through the cooling device 2b, and the vacuum pump 3 is activated to maintain the pressure inside the drying chamber 1 in a reduced pressure state. In addition, heating plates 8 are arranged in parallel in the drying chamber 1 at different positions relative to the tray 7.
Ice in the frozen object to be processed is sublimated by a heating device 9 equipped with a heating device 9, and drying is performed while trapping water vapor in a low-temperature trap 2. [Another Example] In addition to forming the groove B on the surface of the frozen product A,
When freezing a liquid substance, or before freezing, it is placed in a container 4a whose bottom surface has a corrugated or chevron-shaped uneven surface (Fig. 4A), and after freezing, it is formed into the same shape as the bottom surface of the container 4a. The bottom surface of the frozen product A may be directed upward (FIG. 4B) to increase the externally exposed surface. The experimental results for each of the above examples are shown in the following table.
【表】
また、上記実験は、味噌についても同様の良い
結果が得られた。[Table] In addition, similar good results were obtained for miso in the above experiment.
【図面の簡単な説明】[Brief explanation of drawings]
図面は本発明に係る液状物質の凍結乾燥方法の
実施例を示し、第１図は凍結手段を示す概略説明
図、第２図は凍結品の斜視図、第３図は真空乾燥
手段の概略説明図、第４図イ，ロは、別実施例を
示す説明図である。
The drawings show an embodiment of the method for freeze-drying a liquid substance according to the present invention, in which FIG. 1 is a schematic explanatory diagram showing a freezing means, FIG. 2 is a perspective view of a frozen product, and FIG. 3 is a schematic explanation of a vacuum drying means. FIG. 4A and FIG. 4B are explanatory diagrams showing another embodiment.