【発明の詳細な説明】[Detailed description of the invention]
本発明は、米穀を精白する方法に係り、特に酒
造原料米を得るに好適な精白方法に関する。
表皮が除去された精米は、一般に表層部に粗脂
肪分、粗蛋白分、灰分が多く存在しており、通常
は上記精米を更に精白して粗脂肪分等を除去して
いた。特に、精米を酒造原料に用いる場合には、
粗脂肪分が香りに、粗蛋白分が味に、灰分（特に
鉄分）が色及び貯蔵性に悪影響を及ぼすことか
ら、高度に精白された米（平均精米歩合73％）を
使用せざるを得ず、非常に原料利用効率が悪かつ
た。更に、酒造原料米には米粒の形状が保たれた
ものが好ましく、このため酒造原料米を精白する
とき、砕米発生が少ない搗精方法が採用されてい
る。しかるに、砕米の発生を抑えると、精白後の
胚芽の残存率は高く、このため、粗脂肪分等が高
い濃度で存在する胚芽部を除去するには、前述の
ように高度な精白率とすることが必要であつて、
これが米を酒造原料として用いる場合の利用効率
を大幅に低下させる原因となつていた。
本発明は、上記事情に鑑みてなされたもので、
精米から粗脂肪分、粗蛋白分、灰分を除去するこ
とができるうえに胚芽部を極めて効率良く除去す
ることができ、従つて高度な精白を必要とせずに
とくに酒造原料に適した精白米を得ることができ
る米穀の精白方法を提供することを目的とする。
本発明者等は、上記の目的を達成すべく鋭意研
究を行なつた結果、精米を液体状態または超臨界
状態の二酸化炭素に接触せしめると、胚乳部への
胚芽部の付着力が弱まり、胚芽部が脱落し易くな
ることを見出して本発明に至つた。
以下、本発明を詳細に説明する。
本発明の米穀の精白方法は、精米歩合75〜90％
の精米を液体状態または超臨界状態の二酸化炭素
と接触せしめて洗浄処理し、次いで処理後の精米
に物理的衝撃を与えて胚芽部を脱落せしめること
を特徴とする。
まず、この発明に用いられる二酸化炭素の性状
は、液体状態または超臨界状態である。ここでい
う超臨界状態とは、臨界点（二酸化炭素では温度
31.06℃、圧力75.2Kg／cm3）以上の温度又は圧力
の状態である。
この発明の方法においては、上記状態の二酸化
炭素に精米を接触させて、洗浄処理を行なう。具
体的には、まず耐圧容器内に精米を所定量収容す
る。次に上記状態の二酸化炭素を加えて洗浄処理
する。この際の二酸化炭素の温度は、−20〜150
℃、圧力は20〜300Kg／cm3とされる。また、外部
から撹拌等の外力を加える必要はないが、必要に
応じて静かに撹拌してもよく、さらには一定量の
二酸化炭素を容器内に連続的に循環させて洗浄す
るようにしてもよい。処理時間は、特に限定され
るものではなく、数分〜数時間の範囲で用途によ
つて適宜選択される。二酸化炭素の温度、圧力
は、上記の範囲から目的に応じて好ましい値が選
ばれる。すなわち、米中の臭気成分を主に除去し
ようとする場合（脱臭）には、低温、低圧で処理
すれば良く、20〜80Kg／cm3、−20〜20℃の範囲で
処理すればよく、また、臭気成分と脂肪分とを同
時に除去しようとする場合（脱脂、脱臭）には、
高温、高圧で処理すればよく、80〜300Kg／cm3、
20〜150℃で処理すればよい。一般に、高温、高
圧で処理すれば二酸化炭素の溶剤としての溶解性
が向上し、よく脱脂、脱臭されるようになる。
一定時間洗浄処理が行なわれたのち、まず二酸
化炭素を耐圧容器から排出し、常圧まで減じた
後、精米を取り出す。
次に、上記の洗浄処理を施した精米に物理的衝
撃を与え、胚乳部から胚芽部を脱落させる。この
胚芽分離処理は、通常の精米機、研磨機等を使用
して行なうことができる。この処理においては、
精米中の粗脂肪分が低下しているため胚芽部が容
易に脱落する状態となつているため、砕米を発生
しない程度の緩やかな精白方法が適している。胚
芽部を脱落せしめた後には、通常の振動ふるい等
を用いて、精米から胚芽部を分離、除去し、胚芽
中に濃縮されている粗脂肪分、粗蛋白分、灰分が
除去されると共に胚芽部が除去された処理米が得
られる。
しかして、例えば酒造用原料米をこの方法で処
理する場合には、精白度（精米歩合）は最小限の
91〜92％でも十分に粗脂肪分、粗蛋白分、灰分が
除去されたものを得ることができ、原料米の歩留
を向上させることができるが、本発明では、精米
歩合が75〜90％に搗精された精米を用いること
で、精白効果に万全を期するようにし、これによ
つて特に酒造原料米を好適に得ることができる。
また、処理米の吸水速度は、飛躍的に（未処理米
に比して２〜10倍）増加する。よつて、酒造原料
米としたときの蒸しもよくなる。
上記のようにして洗浄処理及び胚芽除去処理を
受けた精米は、胚芽がほとんど残存せず、かつ脱
脂、脱臭が行なわれ、光沢に富み透明感のある白
色の精米が得られ、清酒、ビール等の醸造原料米
として特に好適であるばかりでなく、米飯や各種
米加工品の原料としても広く使用されうるもので
ある。
また、二酸化炭素は周知のように食品衛生上安
全なものであり、全く無害であり、しかも処理中
に米中の害虫やその卵等を死滅させることもで
き、保存性の向上も期待される。
以下、実施例を示して本発明を具体的に説明す
る。
〔実施例〕
(a) 試料：佐賀県産レイホウの90％、85％、75％
精白米の三種を用いた。
(b) 処理法
試料140ｇを内容積0.25のオートクレーブ
中に入れ、液化二酸化炭素容器より二酸化炭素
をオートクレーブ内に導入する。次いで、液体
ポンプによりオートクレーブ内を昇圧すると共
に昇温し、圧力250bar、温度35℃とし、この
状態を１時間保持して洗浄処理を行なつた。そ
の後、再びポンプを稼動して、オートクレーブ
内の温度と圧力を保ちながらオートクレーブの
出口バルブを徐々に開放し、流量計を読みなが
ら250Nの二酸化炭素を排出し、その後徐々
に減圧した。次いで、オートクレーブを開放
し、試料を取り出し、さらに米粒を相互に摩擦
した後、ふるいにかけることにより胚乳部と胚
芽部とを分離した。
(c) 測定項目
上記の処理により得られた胚乳部と無処理の
精米とについて、水分量、粗脂肪分の含有率、
粗蛋白分の含有率、鉄分の含有量及び胚芽残存
率を測定した。
(d) 結果
本発明の処理を行なつて得られた精米は、砕
米を発生することなく、無処理の試料と比べ白
度が向上していた。また、いずれの精米歩合の
ものも糠臭が殆んど残らず、米粒を観察した結
果、胚芽部が奇麗に脱落していた。なお、分離
された胚芽は、粒状として得られた。
下記の表に測定結果を示す。
The present invention relates to a method of polishing rice grains, and particularly to a method of polishing rice suitable for obtaining raw material rice for sake brewing. Polished rice from which the epidermis has been removed generally contains large amounts of crude fat, crude protein, and ash in the surface layer, and the polished rice is usually further polished to remove crude fat and the like. Especially when using polished rice as raw material for sake brewing,
Because the crude fat content has a negative effect on the aroma, the crude protein content on the taste, and the ash content (especially iron content) on the color and storage stability, it is necessary to use highly polished rice (average polishing ratio of 73%). First, the raw material utilization efficiency was extremely poor. Furthermore, it is preferable that the grain shape of the rice grains is maintained in the raw material rice for sake brewing, and for this reason, when polishing the rice raw material for sake brewing, a milling method that reduces the occurrence of broken rice is adopted. However, if the occurrence of broken rice is suppressed, the survival rate of the germ after milling is high. Therefore, in order to remove the germ where a high concentration of crude fat etc. is present, a high polishing rate is required as described above. It is necessary that
This was a cause of a significant decrease in the utilization efficiency when using rice as a raw material for sake brewing. The present invention was made in view of the above circumstances, and
Crude fat, crude protein, and ash can be removed from polished rice, and the germ can be removed extremely efficiently. Therefore, it is possible to produce polished rice that is especially suitable as a raw material for sake brewing without the need for advanced polishing. The purpose of the present invention is to provide a method for polishing rice that can be obtained. As a result of intensive research to achieve the above object, the present inventors have found that when polished rice is brought into contact with liquid or supercritical carbon dioxide, the adhesion of the germ to the endosperm is weakened, and the germ The present invention was achieved by discovering that the parts become easy to fall off. The present invention will be explained in detail below. The rice polishing method of the present invention has a rice polishing ratio of 75 to 90%.
The method is characterized in that the polished rice is brought into contact with carbon dioxide in a liquid state or a supercritical state to undergo a cleaning treatment, and then a physical impact is applied to the treated polished rice to cause the germ part to fall off. First, the carbon dioxide used in this invention is in a liquid state or a supercritical state. The supercritical state here refers to the critical point (in the case of carbon dioxide, the temperature
31.06℃, pressure 75.2Kg/cm 3 ) or higher. In the method of the present invention, cleaning treatment is performed by bringing polished rice into contact with carbon dioxide in the above-mentioned state. Specifically, first, a predetermined amount of polished rice is placed in a pressure container. Next, carbon dioxide in the above state is added for cleaning treatment. The temperature of carbon dioxide at this time is -20 to 150
℃ and the pressure is 20 to 300 Kg/cm 3 . In addition, it is not necessary to apply external force such as stirring from the outside, but if necessary, it may be possible to stir gently, or even a certain amount of carbon dioxide may be continuously circulated inside the container for cleaning. good. The treatment time is not particularly limited, and is appropriately selected from several minutes to several hours depending on the application. Preferable values for the temperature and pressure of carbon dioxide are selected from the above ranges depending on the purpose. In other words, when mainly removing odor components from rice (deodorization), it is sufficient to process at low temperature and low pressure, at a temperature of 20 to 80 kg/cm 3 and -20 to 20°C. In addition, when trying to remove odor components and fat components at the same time (degreasing, deodorization),
It only needs to be treated at high temperature and high pressure, 80~300Kg/ cm3 ,
It is sufficient to process at 20 to 150°C. In general, treatment at high temperature and high pressure improves the solubility of carbon dioxide as a solvent, resulting in better degreasing and deodorization. After the washing process has been carried out for a certain period of time, carbon dioxide is first discharged from the pressure container, and after the pressure is reduced to normal pressure, the polished rice is taken out. Next, a physical impact is applied to the polished rice that has been subjected to the washing process to cause the germ part to fall off from the endosperm part. This germ separation treatment can be carried out using an ordinary rice mill, polisher, etc. In this process,
Since the crude fat content in milled rice is low and the germ part easily falls off, a gentle milling method that does not cause broken rice is suitable. After the germ is removed, the germ is separated and removed from the polished rice using a regular vibrating sieve, and the crude fat, crude protein, and ash concentrated in the germ are removed, and the germ is removed. Processed rice from which portions have been removed is obtained. Therefore, when processing raw rice for sake brewing using this method, for example, the degree of polishing (polishing ratio) is minimal.
Even with a polishing ratio of 91 to 92%, it is possible to obtain rice from which crude fat, crude protein, and ash have been sufficiently removed, and the yield of raw rice can be improved. By using polished rice that has been milled to 100%, the polishing effect can be ensured, and as a result, rice used as a raw material for sake brewing can be particularly preferably obtained.
In addition, the water absorption rate of treated rice increases dramatically (2 to 10 times that of untreated rice). As a result, steaming becomes better when used as raw material for sake brewing. The milled rice that has been washed and germ-removed as described above has almost no germ left, has been degreased and deodorized, and has a glossy and transparent white polished rice that can be used for sake, beer, etc. Not only is it particularly suitable as a raw material for brewing rice, but it can also be widely used as a raw material for cooked rice and various processed rice products. In addition, as is well known, carbon dioxide is safe from a food hygiene perspective and is completely harmless. Furthermore, it can kill pests and their eggs in rice during processing, and is expected to improve shelf life. . Hereinafter, the present invention will be specifically explained with reference to Examples. [Example] (a) Sample: 90%, 85%, 75% of Reihou from Saga Prefecture
Three types of polished rice were used. (b) Treatment method Place 140 g of the sample in an autoclave with an internal volume of 0.25, and introduce carbon dioxide into the autoclave from a liquefied carbon dioxide container. Next, the inside of the autoclave was pressurized and heated by a liquid pump to a pressure of 250 bar and a temperature of 35° C., and this state was maintained for 1 hour to perform a cleaning treatment. After that, the pump was operated again, and the autoclave outlet valve was gradually opened while maintaining the temperature and pressure inside the autoclave, and 250N of carbon dioxide was discharged while reading the flow meter, and then the pressure was gradually reduced. Next, the autoclave was opened, the sample was taken out, the rice grains were rubbed against each other, and then the endosperm and germ were separated by sieving. (c) Measurement items Water content, crude fat content,
Crude protein content, iron content, and germ survival rate were measured. (d) Results The polished rice obtained by the treatment of the present invention did not generate broken rice and had improved whiteness compared to the untreated sample. Furthermore, in all the rice milling ratios, almost no bran odor remained, and as a result of observing the rice grains, the germ part had fallen off cleanly. Note that the separated embryo was obtained in the form of granules. The measurement results are shown in the table below.
【表】
上記の結果から分かるように、本発明の精白方
法により胚芽残存率は著しく低下し、これに伴い
鉄分の量も大幅に減少した。また、本発明の処理
を施した90％及び85％精米の分析結果と、無処理
の75％精米の分析結果とを比較して分かるよう
に、本発明の方法によれば、90％、85％の精白率
の米でも酒造原料として使用できる程度に粗脂肪
分、粗蛋白分、灰分の含有量が少ないものが得ら
れることが確認できた。
以上、説明したように、本発明の米穀の精白方
法は、精米歩合75〜90％の精米を液体状態または
超臨界状態の二酸化炭素に接触させ、二酸化炭素
の溶解能によつて精米中の粗脂肪分を除去し、次
いで精米に物理的衝撃を与えて胚芽部を脱落、除
去し、粗蛋白分、および灰分を除去するものであ
るので、処理後の精米には胚芽部がほとんど残存
せず、かつ粗脂肪分等の量が低下し、異臭成分も
存在せず、かつ外観も美麗で、吸水性が向上し、
特に酒造用原料米として好適なものとなる。ま
た、洗浄により、脱糠されているため水洗の必要
がなく、洗米廃水による廃水処理等の問題もな
く、洗浄に伴う省力化も達成できる。さらに、二
酸化炭素は、食品衛生上の問題を招くことがな
い。特に酒造用原料米としては、従来のように高
度に精白する必要がなく、原料歩留が大幅に向上
し、ひいては清酒製造コストの低減が計れる。ま
た、除去された胚芽部は、容易に乾燥状態で回収
することができるので、その有効利用をも計るこ
とができる。さらに、処理によつて精米中の害虫
やその卵等を死滅させることができ、保存性が向
上する等のすぐれた利点を有する。[Table] As can be seen from the above results, the germ survival rate was significantly reduced by the polishing method of the present invention, and the amount of iron content was also significantly reduced. Furthermore, as can be seen by comparing the analysis results of 90% and 85% milled rice treated with the present invention and the analysis results of untreated 75% milled rice, according to the method of the present invention, 90%, 85% It was confirmed that even rice with a polishing rate of 1.5% can be obtained with low crude fat, crude protein, and ash contents to the extent that it can be used as a raw material for sake brewing. As explained above, in the rice milling method of the present invention, polished rice with a milling ratio of 75 to 90% is brought into contact with carbon dioxide in a liquid state or a supercritical state. The fat content is removed, and then the germ part is sloughed off and removed by applying a physical impact to the milled rice, and the crude protein and ash are removed, so almost no germ part remains in the polished rice after processing. , the amount of crude fat etc. is reduced, there are no off-flavor components, the appearance is beautiful, water absorption is improved,
It is particularly suitable as raw material rice for sake brewing. Furthermore, since the rice bran has been removed by washing, there is no need for washing with water, and there is no problem with waste water treatment due to waste water from washing rice, and labor savings associated with washing can also be achieved. Furthermore, carbon dioxide does not pose food hygiene problems. In particular, as raw material rice for sake brewing, it does not need to be polished to a high degree as in the past, and the raw material yield can be greatly improved, which in turn can reduce the cost of sake production. Furthermore, since the removed germ can be easily recovered in a dry state, it can be used effectively. Furthermore, the treatment can kill pests and their eggs during rice milling, and has excellent advantages such as improved storage stability.