【発明の詳細な説明】
本発明は食品、飼料、化粧品等の粉粒物原料を
加熱殺菌する方法に関するものである。
微生物等により汚染された食品原料等を殺菌す
る方法の一つとして、乾燥あるいは湿熱による加
熱殺菌があり、乾燥状態で粉粒物を処理したい場
合等には、熱風や過熱水蒸気による乾燥殺菌が行
なわれる。そして過熱水蒸気は熱風に比し、熱容
量が大きく殺菌効果が大であること、処理物の酸
化が少ないことなどのメリツトがあり、これを用
いて流動式あるいは通気式の加熱殺菌方法が知ら
れている。
一方、気流加熱方式による膨化食品の製造方法
及び装置として特公昭46−34747号が公知である
が、この方法は粒状又は粉状の食品原料を細長い
流路内を高速で流れる高圧の過熱水蒸気の流れに
のせて加熱し、急激に大気中に放出する膨化食品
の製造法（装置）である。
本発明者等は、この膨化食品の製造法を粉粒物
の加熱殺菌に利用することにつき検討の結果、流
動式あるいは通気式の加熱殺菌方法よりも、気流
加熱方式の方が短時間で、かつ均一に加熱殺菌す
ることができるという知見を得た。
気流加熱方式の場合、過熱水蒸気の気流中に投
入された粉粒物原料は初速０ｍ／secから徐々に
速度を上げ、過熱水蒸気の流速とほぼ同じ速度
（例えば15ｍ／sec）に達し、管路内を浮遊しなが
な移動する。
すなわち投入された直後の粉粒物の過熱水蒸気
との接触速度（相対速度）が非常に大きいので、
流動式や通気式に比べて境膜伝熱係数が大きくな
り、短時間で粒子内部まで加熱され殺菌すること
ができる。更に粉粒物は管路内をバラバラな状態
で浮遊移動するので、均一に加熱殺菌することが
できるのである。
しかしながら膨化を必要とせず、単なる加熱殺
菌をを目的とする場合には、特公昭46−34747号
の様に殊更高圧の過熱水蒸気は不要であり、むし
ろ低圧の過熱水蒸気を用いた方が、装置を簡略化
することができるほか、殺菌効果も上昇し更には
操作上も好ましいという知見を得た。
すなわち高圧の過熱水蒸気を用いる場合には、
装置全体を耐圧設計としなければならず、また流
路に粉粒物を供給したり、流路から粉粒物を排出
したりする場合、シール性の高いバルブが必要で
ある等設備コストの増蒿の他、以下の如き不都合
が生じる。
(1) 加熱殺菌に用いる高圧の過熱水蒸気は低圧の
それに比し、粉粒物の投入バルブが隙間から漏
れ易いこと。
すなわち一般的にシール部の一定平行隙間か
ら漏れるガスの量は次式で示される様に高圧側
と低圧側の圧力差に比例して増加するものであ
る。
Ｑ＝980・Δp・h3／12η1（cm3／sec）
Δp：圧力差（Kg／cm2）
ｈ：隙間（cm）
η：ガス粘度（ｐ）
１：シール部の流れ方向の長さ（cm）
そして漏れた過熱水蒸気は冷えてホツパー内
の粉粒物に水分として付着し、粉粒物を団塊化
させ、そしてこのかたまりとなつた原料を流路
内に投入して過熱水蒸気により浮遊移送させて
も、かたまりの内部まで殺菌ができず、全体的
にみて殺菌効果が減少し、更にはなはだしいと
きにはこのかたまりが流路の閉塞を惹起するこ
と。
(2) 排出バルブの場合も圧力が高いとシール部か
らの過熱水蒸気の漏れが増加するのみならず、
粉粒物移送のためのバルブポケツトの空容積に
入る過熱水蒸気量も圧力が高い程多くなるの
で、原料に同伴して排出される過熱水蒸気量は
更に増加する。そしてこの過熱水蒸気は温度の
低下と共に粉粒物に水分として付着し、加熱殺
菌後の粉粒物の団塊化や二次汚染の原因となる
こと。
(3) 高圧で加熱殺菌したのち急激に低圧下に放出
すると粉粒物は膨化し、組識が易砕性となり、
このため例えばパン粉などは微細化してパン粉
としての商品価値を低下させる場合があるこ
と。
本発明はこれらの知見にもとずき完成したもの
であつて、粉粒物を低圧の過熱水蒸気で管路内を
浮遊移送させることを特徴とする粉粒物の加熱殺
菌方法である。
以下本発明を添付の図面によつて具体的に説明
する。
本発明における粉粒物は特に限定されることは
なく、例えば穀類、豆類あるいはこれらの粉末化
物、野菜等の細片、パン粉、デンプン粉、コシヨ
ー粉、カレー粉等の食品原料、薬品、及び薬品原
料、更には飼料や化粧品原料等が挙げられる。
この様な粉粒物はホツパー１から投入バルブ２
を介して管路３内に投入される。一方図示しない
蒸気発生機で発生させた蒸気は蒸気パイプ９を通
して過熱器８に送られ、過熱水蒸気となり管路３
に送られる。そして管路３内に投入された前記粉
粒物は、過熱水蒸気に浮遊移送されながら管路３
内で加熱殺菌される。そしてサイクロン４で過熱
水蒸気と分離し、排出バルブ５から受ホツパー６
に排出される。サイクロン４で粉粒物と分離した
過熱水蒸気は循環ブロワー１０に接続された循環
パイプ７を介して過熱器に送られ、過熱され更び
加熱殺菌に使用される。
本発明方法に用いられる投入バルブ２及び排出
バルブ５は高圧シール型ロータリーバルブの必要
はなく、低圧の圧力をシールするバルブでよいた
め、製作も簡素化される。また管路３は内壁に凹
凸のない鋼管等が用いられ、その形状は図面に示
す如きＵ字型、あるいは直線型でもよい。
本発明における過熱水蒸気の圧力は0.8Kg／
cm2・Ｇ以下であり、またその温度は処理する粉粒
物の性状、目的とする殺菌の程度等によるが120
℃〜250℃である。
管路３内に供給する過熱水蒸気の風速は粉粒物
の形状、供給量等により異なるが概略10ｍ／sec
〜30ｍ／secであり、加熱時間もまた種々の要因
によつて異なるが、ほぼ２〜15秒である。
尚、管路３は過熱水蒸気の凝縮を防止する上か
ら保温することが好ましく、また付着性の高い粉
粒物を処理する場合には処理前の粉粒物を予熱す
ることが好ましい。
以上の如く本発明は粉粒物を管路内で低圧の過
熱水蒸気に浮遊移送させながら加熱殺菌する方法
であつて、粉粒物を短時間で、しかも均一に加熱
殺菌することができ、高圧の過熱水蒸気による方
法に比し装置が簡略化され、しかも粉粒物の団塊
等が生じることなく殺菌効果の高い加熱殺菌方法
である。
実施例 １
水溶性窒素指数80（NSI80）の脱脂大豆粉（水
分9.5％）を、図面に示す装置を用いて250Kg／hr
の処理量で以下により加熱殺菌した。
直径２ 1/2インチ、長さ20ｍの管路内を圧力
0.5Kg／cm2Ｇ、温度170℃の過熱水蒸気を20ｍ／
secの速度で流し、約３秒間の加熱時間で殺菌し
た。処理前の汚染度、大腸菌群の生菌数は２×
106ケ／ｇで、殺菌処理後の生菌数は０であつた。
殺菌処理後通常の空気輸送を行ない、殺菌した
大豆粉を移送したが、移送先でのサンプリング
（処理後３時間）でも再汚染されていなかつた。
また対照例１として上記と同様の大豆粉を、圧
力５Kg／cm2Ｇ、温度190℃の過熱水蒸気を用いた
こと、及び排出時に大気中へ急激に排出する以外
は、上記と同様の条件で殺菌を行なつたところ、
大豆油の団塊が生じ、その中心部は殺菌が不充分
であつて、平均的には生菌数1.5×102ケ／ｇであ
つた。さらに空気輸送後のサンプリング（処理後
３時間）では2.3×103ケ／ｇとなつて二次汚染さ
れていた。
第１表に処理前と処理後の粒度分布を示す。
【表】DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for heat sterilizing powdery raw materials for foods, feeds, cosmetics, etc. One method for sterilizing food materials contaminated with microorganisms, etc. is heat sterilization using drying or moist heat.If you want to process powder or granules in a dry state, dry sterilization using hot air or superheated steam is used. It will be done. Compared to hot air, superheated steam has the advantages of a large heat capacity, a greater sterilization effect, and less oxidation of the processed material. There is. On the other hand, Japanese Patent Publication No. 46-34747 is known as a method and apparatus for producing puffed foods using an air current heating method, but this method uses high-pressure superheated steam that flows at high speed in a long and narrow channel to feed granular or powdered food ingredients. This is a method (equipment) for producing puffed foods that is heated in a stream and rapidly released into the atmosphere. The present inventors investigated the use of this puffed food manufacturing method for heat sterilization of powdered and granular materials, and found that the airflow heating method is faster and faster than the fluidized or ventilated heat sterilization methods. It was also found that heat sterilization can be performed uniformly. In the case of the airflow heating method, the powder and granular material introduced into the airflow of superheated steam gradually increases its speed from an initial velocity of 0 m/sec, reaches almost the same velocity as the flow velocity of superheated steam (for example, 15 m/sec), and then passes through the pipe. Floating inside and moving around. In other words, the contact speed (relative speed) of the powder and granules with the superheated steam is very high immediately after they are introduced, so
The film heat transfer coefficient is larger than that of flow type or ventilation type, and the inside of particles can be heated and sterilized in a short time. Furthermore, since the powder particles float and move in a separate state within the pipe, it is possible to uniformly heat and sterilize them. However, if expansion is not required and the purpose is simply heat sterilization, there is no need for particularly high-pressure superheated steam as in Japanese Patent Publication No. 46-34747, and it is actually better to use low-pressure superheated steam. In addition to being able to simplify the process, the sterilizing effect was also improved, and it was found that it was also favorable in terms of operation. In other words, when using high-pressure superheated steam,
The entire device must be designed to withstand pressure, and when supplying or discharging particulate matter to the flow path, valves with high sealing performance are required, increasing equipment costs. In addition to this, the following inconveniences occur. (1) The high-pressure superheated steam used for heat sterilization is more likely to leak from the gap in the powder input valve than the low-pressure one. That is, in general, the amount of gas leaking from a constant parallel gap in the seal portion increases in proportion to the pressure difference between the high pressure side and the low pressure side, as shown by the following equation. Q = 980・Δp・h 3 /12η 1 (cm 3 /sec) Δp: Pressure difference (Kg/cm 2 ) h: Gap (cm) η: Gas viscosity (p) 1: Length of seal part in flow direction (cm) The leaked superheated steam cools down and adheres to the powder and granules in the hopper as moisture, causing the powder and granules to form agglomerates, and the lumped raw material is then introduced into the channel and suspended by the superheated steam. Even if it is transferred, it is not possible to sterilize the inside of the mass, which reduces the sterilizing effect as a whole, and furthermore, in severe cases, the mass causes blockage of the flow path. (2) In the case of exhaust valves, high pressure not only increases the leakage of superheated steam from the seal, but also
The amount of superheated steam that enters the empty volume of the valve pocket for transferring powder and granules also increases as the pressure increases, so the amount of superheated steam that is discharged along with the raw material further increases. This superheated steam adheres to the powder and granules as moisture as the temperature decreases, causing agglomeration and secondary contamination of the powder and granules after heat sterilization. (3) If the powder is sterilized by heating at high pressure and then suddenly released under low pressure, the powder will swell and its structure will become friable.
For this reason, bread crumbs, for example, may become finer and reduce their commercial value as bread crumbs. The present invention was completed based on these findings, and is a method for heat sterilization of powder and granular materials, which is characterized by floating and transporting the powder and granular materials in a pipe using low-pressure superheated steam. The present invention will be specifically explained below with reference to the accompanying drawings. The powders and granules in the present invention are not particularly limited, and include, for example, grains, beans or powdered products thereof, fine pieces of vegetables, food raw materials such as bread crumbs, starch powder, koshiyo powder, curry powder, drugs, and pharmaceuticals. Raw materials include feed, cosmetic raw materials, etc. Such powder and granules are transferred from hopper 1 to input valve 2.
It is introduced into the pipe line 3 through the . On the other hand, steam generated by a steam generator (not shown) is sent to a superheater 8 through a steam pipe 9, and becomes superheated steam through a pipe line 3.
sent to. The powder and granules introduced into the pipe 3 are suspended in the superheated steam and transferred to the pipe 3.
Heat sterilized inside. Then, it is separated from the superheated steam by a cyclone 4, and then passed through a discharge valve 5 to a receiving hopper 6.
is discharged. The superheated steam separated from the powder by the cyclone 4 is sent to a superheater via a circulation pipe 7 connected to a circulation blower 10, superheated, and used for heat sterilization. The input valve 2 and the discharge valve 5 used in the method of the present invention do not need to be high-pressure seal type rotary valves, but may be valves that seal against low pressure, so manufacturing is also simplified. Further, the pipe line 3 is made of a steel pipe or the like having no irregularities on its inner wall, and its shape may be a U-shape as shown in the drawings or a straight line shape. The pressure of superheated steam in the present invention is 0.8Kg/
cm2・G or less, and the temperature depends on the properties of the powder and granules being treated, the desired degree of sterilization, etc.
℃~250℃. The wind speed of the superheated steam supplied into the pipe 3 varies depending on the shape of the powder, the amount supplied, etc., but is approximately 10 m/sec.
~30 m/sec, and the heating time also varies depending on various factors, but is approximately 2 to 15 seconds. In addition, it is preferable to keep the pipe 3 warm in order to prevent condensation of superheated steam, and when processing highly adhesive particles, it is preferable to preheat the particles before treatment. As described above, the present invention is a method of heating and sterilizing powder and granular materials while floating them in low-pressure superheated steam in a pipe, and is capable of heat-sterilizing powder and granular materials uniformly in a short time and under high pressure. This heat sterilization method has a simpler equipment than the method using superheated steam, and has a high sterilization effect without producing lumps of powder particles. Example 1 Defatted soybean flour (moisture 9.5%) with a water-soluble nitrogen index of 80 (NSI80) was processed at 250 kg/hr using the equipment shown in the drawing.
Heat sterilization was performed using the following method at a processing amount of . Pressure inside a pipe with a diameter of 2 1/2 inches and a length of 20 m
0.5Kg/cm 2 G, superheated steam at a temperature of 170℃, 20m/
It was sterilized by flowing at a speed of 3 seconds and heating for about 3 seconds. The degree of contamination before treatment, the number of viable coliform bacteria is 2x
106 bacteria/g, and the number of viable bacteria after sterilization was 0. After the sterilization treatment, the sterilized soybean flour was transferred using normal pneumatic transportation, but sampling at the destination (3 hours after treatment) showed no recontamination. In addition, as a control example 1, the same soybean flour as above was used under the same conditions as above, except that superheated steam at a pressure of 5 kg/cm 2 G and a temperature of 190°C was used, and that it was rapidly discharged into the atmosphere at the time of discharge. After sterilization,
Nodules of soybean oil were formed, the center of which was insufficiently sterilized, with an average number of viable bacteria of 1.5×10 2 cells/g. Furthermore, sampling after air transportation (3 hours after treatment) showed secondary contamination at 2.3 x 103 pieces/g. Table 1 shows the particle size distribution before and after treatment. 【table】
【図面の簡単な説明】[Brief explanation of drawings]
第１図は本発明方法の概略説明図である。
１……ホツパー、２……投入バルブ、３……管
路、４……サイクロン、５……排出バルブ、６…
…受ホツパー、７……循環パイプ、８……過熱
器、９……蒸気パイプ、１０……循環ブロワー。
FIG. 1 is a schematic explanatory diagram of the method of the present invention. 1...Hopper, 2...Input valve, 3...Pipe line, 4...Cyclone, 5...Discharge valve, 6...
...Receiving hopper, 7...Circulation pipe, 8...Superheater, 9...Steam pipe, 10...Circulation blower.