【発明の詳細な説明】[Detailed description of the invention]
本発明は通常の精白米と全く同様の操作によつ
て炊飯可能な玄米の製造法に関する。
玄米の構造は外皮といわれる果皮、種皮、更に
外胚乳、糊粉層と続き、糊粉層の内部は澱粉粒か
ら成る内胚乳及び胚芽で構成されており、そして
上記外皮（特に種皮）は半透過性隔膜の生理作用
をもつていて、内胚乳を強く保護している。この
ため通常の炊飯方法では内胚乳にまで充分に水分
が供給されず、ボソボソとした咀嚼感の悪い飯米
しか得られず、これを解決するため従来は圧力釜
を用いたりあるいは二度炊き等が行なわれてい
た。
この様に玄米は特殊な炊飯方法によらなけれ
ば、咀嚼感上満足できる飯米とはならず、それ故
精白米に比し栄養的に優れているにもかかわら
ず、一部愛好者のみにしか利用、普及されていな
いのが現状であつた。ところが近時自然食指向が
高まりつつある中で、通常の炊飯方法によつて炊
飯可能な玄米の要望が強く、これについての研究
が各方面で行なわれている。
その一つとして玄米の吸水を容易にさせる目的
で、外皮に亀裂を生ぜしめた玄米の製造方法があ
り、例えば特開昭51−151354号、特開昭52−
94442号に見られる玄米をローラで押圧する方
法、特開昭54−32643号のように105〜130℃の熱
風で乾燥後急冷する方法、あるいは特開昭54−
119043号の如く回転網かごに収容して玄米が焦げ
ないように撹拌しながら加熱する方法がある。
これらの方法はいずれも玄米の外皮に亀裂を生
ぜしめ、易吸水性とするもので、この様にした玄
米は通常の方法で炊飯可能となる。
しかしながら上記した方法は必ずしも満足出来
る方法とは云い難く、例えば破砕米が生じる、
（ローラーによる方法）玄米の油脂分が酸化され
飯米として異臭がつくなどの欠点がある。
本発明者等は玄米の外皮に亀裂を生ぜしめる方
法につき研究の結果、玄米を過熱水蒸気で加熱す
ることにより、破砕米となる様なことがなくしか
もほとんど酸化が生じることなく玄米の外皮に亀
裂を生ぜしめることができ、しかも内胚乳がポー
ラスとなり極めて吸水性が向上し、通常の炊飯方
法で容易に炊飯可能な玄米が得られるという知見
を得て本発明を完成した。
すなわち本発明は玄米を過熱水蒸気で加熱し
て、見掛比重0.50〜0.75に膨化させ、玄米外皮に
亀裂を生ぜしめることを特徴とする易炊玄米の製
造法である。
以下本発明を具体的に説明する。
玄米をそのままあるいは軽く水洗後、過熱水蒸
気により加熱し玄米の見掛比重を0.50〜0.75に膨
化させる。この膨化により玄米の外皮に適宜の亀
裂が生じ、炊飯時の吸水が好適に行なわれること
になる。そして膨化の程度は上記した範囲の見掛
比重になるように行なうことが肝要で、見掛比重
がこの範囲より大であるときは、吸水が悪く通常
の炊飯方法では硬い飯米となり、また見掛比重が
上記範囲より小さい場合、すなわち膨化し過ぎた
場合、飯米は粥状となるので好ましくない。
玄米を過熱水蒸気で加熱し、見掛比重0.50〜
0.75に膨化させるには、常圧、加圧いずれの状態
で行なつてもよく、例えば常圧の場合、150〜250
℃の過熱水蒸気に10秒〜300秒接触加熱する。
また加圧状態で加熱する場合には圧力1.0〜3.5
Kg／cm2Ｇ、温度130〜250℃、好ましくは圧力2.0
〜3.0Kg／cm2Ｇ、温度190〜210℃で５〜20秒間加
熱し、急激により低圧下に放出して膨化させる。
加熱の方法は、常圧、加圧いずれの場合でも玄
米がむらなく、均一に加熱される方法であればど
の様な方法でもよいが、特に玄米が流動撹拌状態
で加熱される装置を好適に用いることが出来る。
例えば加圧状態で加熱する場合には、特公昭45
−26695号「膨化食品の製造装置」あるいは特公
昭46−34747号「気流加熱方式による膨化食品の
製造装置」等が挙げられ、また常圧で加熱する場
合には通常の気固接触装置あるいは上記した膨化
装置を常圧で用いることができる。
これらの装置を用いて加熱膨化させた玄米は、
外皮に亀裂が生じ、しかも内胚乳部がポーラスと
なり吸水性がよく、通常の炊飯方法で炊飯可能な
玄米となる。
そして過熱水蒸気で加熱するため、従来公知の
方法に比し、焦臭や、酸化による異臭がなく、炊
飯玄米として好ましい品質のものが得られるので
ある。
また加熱時間が極めて短いため、玄米中のビタ
ミン類等の栄養成分の破壊が少ないという効果も
有する。
以下実施例を示す。
実施例 １
53年度産こしひかり種の玄米（水分14.5％、見
掛比重0.86）をそのまま、特公昭46−34747号に
示す膨化装置を用い、圧力２Kg／cm2Ｇ、温度210
℃の過熱水蒸気で10秒間の加熱を行なつたのち、
急激に大気圧下に放出して易炊玄米を得た。
この易炊玄米は水分7.0％、見掛比重0.60であ
り粒度は６〜８メツシユが98％であつた。
実施例 ２
実施例１と用いたと同様の玄米をそのまま流動
式乾燥機により常圧180℃の過熱水蒸気で30秒間
加熱したところ、水分８％、見掛比重0.63の易炊
玄米が得られた。
比較例
実施例１、実施例２で得た易炊玄米及び対照と
して特開昭54−32643号に準じて得た易炊玄米320
ｇに水500mlを加え、家庭用電気炊飯器で25分炊
飯し、その飯米の官能検査及び硬さの測定を行な
つたところ第１表〜第３表に示す結果を得た。
尚官能検査は15名のパネルにより、対照（特開
昭54−32643号）との２点比較法によつた。
また飯米の硬さは飯尾電気K.K.のRMT−1300
型レオロメーターで、感度電圧3V、感圧軸直径
10mmの平板試料支持台との最終クリアランス0.5
mmとして測定した曲線の高さを硬さとして表わし
たもので、数値の高いものほど硬くなることを示
しており、表中の数値は50粒の平均値である。
The present invention relates to a method for producing brown rice that can be cooked in exactly the same manner as ordinary polished rice. The structure of brown rice consists of a pericarp called the outer skin, a seed coat, an ectosperm, and an aleurone layer.The inside of the aleurone layer is composed of endosperm and germ made of starch grains, and the outer skin (particularly the seed coat) consists of a semi-aleurone layer. It has the physiological function of a permeable diaphragm and strongly protects the endosperm. For this reason, with normal rice cooking methods, sufficient water is not supplied to the endosperm, resulting in rice that is crumbly and has a poor chewability.To solve this problem, conventional methods such as using a pressure cooker or double-cooking have been used. It was being done. In this way, unless brown rice is cooked in a special rice cooking method, it cannot be made into rice that is satisfying to chew, and even though it is nutritionally superior to polished rice, it is only enjoyed by some enthusiasts. Currently, it is not being used or popularized. However, with the recent trend toward natural foods, there is a strong demand for brown rice that can be cooked using conventional rice cooking methods, and research on this topic is being conducted in various fields. One of them is a method for producing brown rice in which cracks are created in the outer skin in order to make it easier to absorb water.
A method of pressing brown rice with a roller as shown in No. 94442, a method of drying with hot air at 105 to 130 degrees Celsius and then quenching as in JP-A-54-32643, or a method of rapidly cooling after drying with hot air at 105 to 130 degrees Celsius as in JP-A-54-32643.
There is a method, such as No. 119043, in which brown rice is stored in a rotating mesh basket and heated while stirring to prevent brown rice from burning. All of these methods create cracks in the outer skin of brown rice, making it easy to absorb water, and brown rice made in this way can be cooked in the usual manner. However, the above-mentioned method is not necessarily a satisfactory method, for example, broken rice is produced.
(Roller method) There are disadvantages such as the oil and fat in brown rice being oxidized and the cooked rice having a strange odor. As a result of research on a method for creating cracks in the outer skin of brown rice, the present inventors found that by heating brown rice with superheated steam, cracks in the outer skin of brown rice could be created without causing the rice to become broken, and with almost no oxidation. The present invention was completed based on the knowledge that the endosperm becomes porous, has extremely improved water absorption, and that brown rice that can be easily cooked using a normal rice cooking method can be obtained. That is, the present invention is an easy-to-cook brown rice production method characterized by heating brown rice with superheated steam to expand the brown rice to an apparent specific gravity of 0.50 to 0.75, thereby causing cracks in the outer skin of the brown rice. The present invention will be specifically explained below. The brown rice is heated as it is or after being lightly washed with water and heated with superheated steam to expand the apparent specific gravity of the brown rice to 0.50 to 0.75. This swelling causes appropriate cracks in the outer skin of the brown rice, which facilitates water absorption during cooking. It is important that the degree of puffing is done so that the apparent specific gravity is within the above range. If the apparent specific gravity is greater than this range, the rice will not absorb water well and will be hard when cooked with normal rice cooking methods, and the apparent specific gravity will be higher than the above range. If the specific gravity is lower than the above range, that is, if the rice is too puffed, the cooked rice will become porridge-like, which is not preferable. Brown rice is heated with superheated steam to give an apparent specific gravity of 0.50~
In order to expand to 0.75, it may be carried out under either normal pressure or pressurized conditions. For example, in the case of normal pressure, 150-250
Heat in contact with superheated steam at ℃ for 10 seconds to 300 seconds. In addition, when heating under pressure, the pressure is 1.0 to 3.5.
Kg/ cm2G , temperature 130-250℃, preferably pressure 2.0
It is heated at ~3.0 Kg/cm 2 G and a temperature of 190-210° C. for 5-20 seconds, and then rapidly discharged under lower pressure to cause swelling. Any heating method may be used as long as the brown rice is heated evenly and uniformly, whether under normal pressure or under pressure, but a device that heats brown rice in a fluidized agitation state is particularly preferred. It can be used. For example, when heating under pressure,
-26695 ``Apparatus for producing puffed foods'' and Japanese Patent Publication No. 1983-34747 ``Apparatus for producing puffed foods using air current heating method''. In addition, when heating at normal pressure, a normal gas-solid contact apparatus or the above-mentioned The expanded device can be used at normal pressure. Brown rice heated and expanded using these devices is
Cracks appear in the outer skin, and the endosperm becomes porous and has good water absorption, resulting in brown rice that can be cooked using normal rice cooking methods. Since the rice is heated with superheated steam, compared to conventionally known methods, there is no burnt odor or off-flavor due to oxidation, and it is possible to obtain rice of a desirable quality as cooked brown rice. Furthermore, since the heating time is extremely short, it also has the effect of minimizing the destruction of nutritional components such as vitamins in brown rice. Examples are shown below. Example 1 Brown rice of the Koshihikari variety produced in 1953 (moisture 14.5%, apparent specific gravity 0.86) was heated as it was using the expansion device shown in Special Publication No. 1983-34747 at a pressure of 2 Kg/cm 2 G and a temperature of 210
After heating with superheated steam at ℃ for 10 seconds,
Easy-to-cook brown rice was obtained by rapidly releasing the rice to atmospheric pressure. This easy-to-cook brown rice had a moisture content of 7.0%, an apparent specific gravity of 0.60, and a grain size of 6 to 8 mesh (98%). Example 2 When brown rice similar to that used in Example 1 was heated as it was in a fluidized fluid dryer with superheated steam at normal pressure of 180°C for 30 seconds, easy-to-cook brown rice with a moisture content of 8% and an apparent specific gravity of 0.63 was obtained. Comparative Examples Easy-cooking brown rice obtained in Examples 1 and 2 and easy-cooking brown rice 320 obtained according to JP-A-54-32643 as a control
500 ml of water was added to the rice, and the rice was cooked for 25 minutes in a household electric rice cooker.The rice was subjected to sensory tests and hardness measurements, and the results shown in Tables 1 to 3 were obtained. The sensory test was conducted by a panel of 15 people using a two-point comparison method with a control (Japanese Patent Application Laid-Open No. 54-32643). Also, the hardness of the rice is RMT-1300 from Iio Denki KK.
Type rheometer, sensitivity voltage 3V, pressure sensitive shaft diameter
Final clearance with 10mm flat sample support stand 0.5
The height of the curve measured in mm is expressed as hardness, and the higher the value, the harder it is, and the values in the table are the average values of 50 grains.
【表】【table】
【表】【table】
【表】【table】