JP7305466B2 - Liquid quality improver for cooked rice and method for producing cooked rice - Google Patents
Liquid quality improver for cooked rice and method for producing cooked rice Download PDFInfo
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本発明は、米飯用液状品質改良剤に関する。また、本発明は、当該液状品質改良剤を用いる米飯の製造方法にも関する。 The present invention relates to a liquid quality improver for cooked rice. The present invention also relates to a method for producing cooked rice using the liquid quality improver.
スーパーマーケットやコンビニエンスストア等では、様々な形態で米飯が販売されている。例えば、市販弁当の主食として容器詰めされた形態で販売されたり、当日消費用にそれだけを透明プラスチック容器に詰めた形態で販売されたりしている。これらの米飯の多くは、必要に応じて電子レンジで加熱後、そのまま食されているが、チャーハン、オムライス、雑炊等の他の米料理に手軽に応用できるため、近年、その販売量が家庭用・業務用共に増加傾向にある。 Cooked rice is sold in various forms in supermarkets, convenience stores, and the like. For example, it is sold in the form of being packed in a container as a staple food for commercially available lunch boxes, or in the form of being packed in a transparent plastic container for consumption on the day itself. Most of these types of cooked rice are eaten as they are after being heated in a microwave oven as needed, but since they can be easily applied to other rice dishes such as fried rice, omelet rice, and rice porridge, in recent years the sales volume has increased to household use.・Both commercial use is on the rise.
ところで、これらの米飯は、一般的に、スーパーマーケットのバックヤードや惣菜工場等において、機械設備によって大量に製造されている。そのため、米飯の製造適性が重要になり、米飯に油を多量に添加する必要がある。また、コスト面からも歩留り向上のために炊飯時の加水を増やすため、食感が損なわれる恐れがある。また、米飯は、チルド温度帯又は常温で店頭販売されたり、流通したりしており、チルド温度帯又は常温に長時間保持された米飯においては、細菌数の増加、食感や風味の劣化といった問題の発生が懸念される。 By the way, these cooked rices are generally mass-produced by machines in supermarket backyards, prepared food factories, and the like. Therefore, the production suitability of cooked rice is important, and it is necessary to add a large amount of oil to cooked rice. In addition, from the viewpoint of cost, the amount of water added during cooking is increased in order to improve the yield, so there is a risk that the texture may be impaired. In addition, cooked rice is sold or distributed at stores in a chilled temperature range or at room temperature. There is concern about the occurrence of problems.
上記の課題を解決するために、米飯原料に、グルコースオキシダーゼ等の酸化還元酵素と、鉄含有酵母や鉄塩等の金属含有物とを添加した後に炊飯することで、炊飯米のもちもち感を増強することが提案されている（特許文献１参照）。また、米飯原料に、枝作り酵素を特定量で添加した後に炊飯することで、米飯の品質を改良することが提案されている（特許文献２参照）。 In order to solve the above problems, the rice raw material is added with an oxidoreductase such as glucose oxidase and a metal-containing substance such as iron-containing yeast and iron salt, and then the rice is cooked to increase the stickiness of the cooked rice. It has been proposed to do so (see Patent Literature 1). Further, it has been proposed to improve the quality of cooked rice by adding a specific amount of a branching enzyme to the cooked rice material and then cooking the rice (see Patent Document 2).
しかしながら、特許文献１及び２に記載の技術は、いずれも粉末状の製剤や酵素を添加するものであり、取り扱いが煩雑であった。また、これらの技術は、米飯の微生物増殖を抑制できる日持ち機能を有するものではなかった。 However, the techniques described in Patent Literatures 1 and 2 both involve the addition of powdered formulations and enzymes, and are complicated to handle. In addition, these techniques do not have a shelf life function that can suppress the growth of microorganisms in cooked rice.
また、単に粉末状の酵素を液体に添加して、液状の米飯用品質改良剤を調整しようとしても、活性を十分に維持した状態で流通させることが難しかった。さらに、この傾向は、米飯の微生物増殖を抑制するために、前記改良剤に酢酸を多量に加えた場合には特に顕著であった。 Moreover, even if an attempt was made to prepare a liquid quality improver for boiled rice by simply adding a powdered enzyme to a liquid, it was difficult to distribute the agent while maintaining its activity sufficiently. Furthermore, this tendency was particularly remarkable when a large amount of acetic acid was added to the improver in order to suppress the growth of microorganisms in cooked rice.
したがって、取り扱い易い液状でありながら、米飯の品質を改善する酵素活性を十分に維持しつつ、同時に添加した米飯の微生物増殖も抑制できる米飯用品質改良剤が求められている。 Therefore, there is a demand for a cooked rice quality improver that can suppress the growth of microorganisms added to the cooked rice while sufficiently maintaining the enzyme activity that improves the quality of the cooked rice while being in an easy-to-handle liquid form.
本発明者らは、上記課題に対して誠意検討した結果、意外にも、食酢を含み、酢酸含有量が特定量超であり、米飯のｐＨが一定以下となるように添加される米飯用液状品質改良剤において、酵素及び有機酸塩を含み、酵素としてαアミラーゼ及びグルコースオキシダーゼを用い、液状品質改良剤のＢｒｉｘ値を特定の範囲内に調節することにより、上記の課題を解決できることを知見した。本発明者らは、このような知見に基づき、本発明を完成するに至った。 As a result of a sincere study on the above problems, the present inventors unexpectedly found that a liquid for cooked rice that contains vinegar, has an acetic acid content exceeding a specific amount, and is added so that the pH of cooked rice is below a certain level The quality improver contains an enzyme and an organic acid salt, α-amylase and glucose oxidase are used as enzymes, and the above problems can be solved by adjusting the Brix value of the liquid quality improver within a specific range. . The present inventors have completed the present invention based on such findings.
すなわち、本発明の一態様によれば、
食酢を含有し、
酢酸含有量が３．０質量％超であり、
炊飯後の米飯を以下の測定方法で測定したときのｐＨが６．２０以下となるように添加される、
米飯用液状品質改良剤において、
酵素及び有機酸塩を含み、
前記酵素が、αアミラーゼ及びグルコースオキシダーゼを含み、
Ｂｒｉｘ値が４５．０％以上７５．０％以下であることを特徴とする、
米飯用液状品質改良剤が提供される。
＜米飯のｐＨ測定方法＞
米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえで、１気圧、品温２０℃とした時にｐＨ測定器を用いて測定した値。
That is, according to one aspect of the present invention,
Contains vinegar,
The acetic acid content is more than 3.0% by mass,
It is added so that the pH of the rice after cooking is 6.20 or less when measured by the following measurement method.
In the liquid quality improver for cooked rice,
containing enzymes and organic acid salts,
the enzyme comprises α-amylase and glucose oxidase;
characterized by a Brix value of 45.0% or more and 75.0% or less,
A liquid quality improver for cooked rice is provided.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.
本発明の態様においては、前記液状品質改良剤が、食塩を２質量％以上含有することが好ましい。 In the aspect of this invention, it is preferable that the said liquid quality improver contains 2 mass % or more of salt.
本発明の態様においては、前記液状品質改良剤の酢酸含有量が、７．０質量％以下であることが好ましい。 In the aspect of this invention, it is preferable that the acetic acid content of the said liquid quality improver is 7.0 mass % or less.
本発明の態様においては、前記液状品質改良剤が、炊飯後の米飯の酢酸含有量が０．０３質量％以上となるように添加されるものであることが好ましい。 In the aspect of the present invention, it is preferable that the liquid quality improver is added so that the acetic acid content of the cooked rice becomes 0.03% by mass or more.
本発明の態様においては、前記食酢の酢酸含有量が１０質量％以上２０質量％以下であることが好ましい。 In the aspect of this invention, it is preferable that the acetic acid content of the said vinegar is 10 mass % or more and 20 mass % or less.
本発明の態様においては、前記有機酸塩が、酢酸塩、クエン酸塩、乳酸塩、フマル酸塩、酒石酸塩、リンゴ酸塩、及びグルコン酸塩からなる群から選択される少なくとも１種であることが好ましい。 In an aspect of the present invention, the organic acid salt is at least one selected from the group consisting of acetate, citrate, lactate, fumarate, tartrate, malate, and gluconate. is preferred.
本発明の態様においては、前記有機酸塩を２種以上含むことが好ましい。 In the aspect of the present invention, it is preferable that two or more of the above organic acid salts are included.
本発明の態様においては、前記有機酸塩が、酢酸塩及びクエン酸塩を含むことが好ましい。 In the aspect of this invention, it is preferable that the said organic acid salt contains an acetate and a citrate.
また、本発明の別の態様によれば、
米飯の製造方法であって、
米飯原料に上記の液状品質改良剤を添加する工程を含み、
以下の測定方法で測定したときのｐＨが６．２０以下であることを特徴とする、
米飯の製造方法が提供される。
＜米飯のｐＨ測定方法＞
米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえで、１気圧、品温２０℃とした時にｐＨ測定器を用いて測定した値。
Also, according to another aspect of the present invention,
A method for producing cooked rice,
Including the step of adding the liquid quality improver to the cooked rice raw material,
characterized by having a pH of 6.20 or less when measured by the following measuring method,
A method for producing cooked rice is provided.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.
本発明によれば、液状でありながら、米飯の品質を改善する酵素活性を十分に維持しつつ、同時に添加した米飯の微生物増殖も抑制できる米飯用品質改良剤を提供することができる。また、本発明によれば、当該米飯用品質改良剤を用いる米飯の製造方法を提供することもできる。 According to the present invention, it is possible to provide a cooked rice quality improving agent that can suppress the growth of microorganisms in the cooked rice added at the same time while sufficiently maintaining the enzyme activity that improves the quality of cooked rice, even though it is in a liquid state. Moreover, according to this invention, the manufacturing method of the cooked rice using the said quality improving agent for cooked rice can also be provided.
＜米飯用液状品質改良剤＞
本発明の液状品質改良剤は、少なくとも、特定の酵素、食酢、及び有機酸塩を含むものであり、液状でありながら、米飯の品質を改善する酵素活性を十分に維持しつつ、同時に添加した米飯の微生物増殖も抑制することができる。本発明において、米飯の品質とは、米飯の食感、風味、または日持ち等を指すものであり、これらの少なくともいずれか一つが改善されればよい。
<Liquid improver for cooked rice>
The liquid quality improver of the present invention contains at least a specific enzyme, vinegar, and an organic acid salt, and is added at the same time while sufficiently maintaining the enzyme activity that improves the quality of cooked rice while being in a liquid state. Microbial growth in cooked rice can also be suppressed. In the present invention, the quality of cooked rice refers to texture, flavor, shelf life, etc. of cooked rice, and at least any one of these should be improved.
（米飯）
本発明において、米飯とは、白飯や玄米を炊飯して得た米飯だけでなく、白米と大麦とを一緒に炊飯して得た麦飯、精米したもち米を炊飯又は蒸して得たおこわ等も含まれる。また、米飯には、各種炊き込みご飯、茶飯、酢飯、赤飯、栗又は豆等の具材入りご飯等の調理加工米飯も含まれる。
(rice)
In the present invention, cooked rice means not only cooked rice obtained by cooking white rice or brown rice, but also barley rice obtained by cooking white rice and barley together, steamed rice obtained by cooking or steaming polished glutinous rice, and the like. included. Cooked rice also includes cooked and processed rice such as various types of cooked rice, brown rice, vinegared rice, red rice, and rice containing ingredients such as chestnuts or beans.
（米飯のｐＨ）
本発明において、米飯のｐＨとは、米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえ、１気圧、品温２０℃とした時に、ｐＨ測定器（株式会社堀場製作所製卓上型ｐＨメータＦ－７２）を用いて測定した値である。
本発明における米飯の、上記方法で測定したｐＨは６．２０以下である。下限は好ましくは５．４０以上であると、風味の面で好ましい。
(pH of cooked rice)
In the present invention, the pH of cooked rice is defined by adding 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, pulverizing the mixture with a mixer or the like so that the whole is uniform, and adjusting the pressure to 1 atm and the product temperature to 20 ° C. It is a value measured using a pH measuring device (desktop pH meter F-72 manufactured by Horiba, Ltd.).
The cooked rice in the present invention has a pH of 6.20 or less as measured by the above method. A lower limit of 5.40 or more is preferred in terms of flavor.
（液状品質改良剤及び米飯の酢酸含有量）
米飯用液状品質改良剤の酢酸含有量は、３．０質量％超であり、上限値は例えば、７．０質量％以下であり、下限値は好ましくは３．２質量％以上であり、より好ましくは３．５質量％以上であり、上限値は好ましくは６．８質量％以下であり、より好ましくは６．７質量％以下である。液状品質改良剤の酢酸含有量は、下記の食酢や酢酸を添加することにより調節することができる。液状品質改良剤の酢酸含有量が上記数値範囲内であれば、米飯のｐＨを所望の範囲内に調節し易く、米飯の微生物増殖を抑制することができる。液状品質改良剤の酢酸含有量が上記範囲を下回ると、米飯の微生物増殖を抑えるために多量に添加する必要があるため、コストの面で好ましくない。
なお、液状品質改良剤及び米飯の酢酸含有量の測定方法は、以下の方法（中和滴定法：定量式）により算出することができる。なお、米飯の酢酸含有量は、米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕し、以下の方法で算出された数値を３で乗ずればよい。
まず、液状品質改良剤または米飯粉砕物を正確に採り、イオン交換水で１０倍に希釈し、その希釈液（１００ｇ）に、指示薬として３．１％フェノールフタレイン溶液を２滴加え、力価既知の０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液で中和滴定して、下記式により、液状品質改良剤の酢酸含有量を求める。
液状品質改良剤の酢酸含有量（質量％）＝｛（６０．０５×０．１×Ｆ×Ｖ）×１００｝／｛サンプル採取量（１０ｇ）×１０００｝
６０．０５：酢酸の分子量
０．１：水酸化ナトリウム溶液のモル濃度（ｍｏｌ／Ｌ）
Ｆ：０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液の力価
Ｖ：０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液の滴定量（ｍＬ）
(Liquid quality improver and acetic acid content of cooked rice)
The acetic acid content of the liquid quality improver for cooked rice is more than 3.0% by mass, the upper limit is, for example, 7.0% by mass or less, and the lower limit is preferably 3.2% by mass or more. It is preferably 3.5% by mass or more, and the upper limit is preferably 6.8% by mass or less, more preferably 6.7% by mass or less. The acetic acid content of the liquid quality improver can be adjusted by adding vinegar or acetic acid as described below. If the acetic acid content of the liquid quality improver is within the above numerical range, the pH of the cooked rice can be easily adjusted within the desired range, and microbial growth in the cooked rice can be suppressed. If the content of acetic acid in the liquid quality improver is below the above range, a large amount of acetic acid must be added to suppress microbial growth in cooked rice, which is undesirable in terms of cost.
The acetic acid content of the liquid quality improver and cooked rice can be calculated by the following method (neutralization titration method: quantitative formula). The acetic acid content of cooked rice is calculated by adding 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, pulverizing the whole with a mixer or the like so that the whole is uniform, and multiplying the value calculated by the following method by 3. Just do it.
First, a liquid quality improver or pulverized cooked rice was accurately collected, diluted 10 times with deionized water, and 2 drops of 3.1% phenolphthalein solution was added as an indicator to the diluted solution (100 g) to determine the titer. Neutralization titration is performed with a known 0.1 mol/L sodium hydroxide solution, and the acetic acid content of the liquid quality improver is determined by the following formula.
Acetic acid content of liquid quality improver (% by mass) = {(60.05 x 0.1 x F x V) x 100}/{sample collection amount (10 g) x 1000}
60.05: Molecular weight of acetic acid 0.1: Molar concentration (mol/L) of sodium hydroxide solution
F: titer of 0.1 mol / L sodium hydroxide solution V: titration volume (mL) of 0.1 mol / L sodium hydroxide solution
（液状品質改良剤のＢｒｉｘ値）
液状品質改良剤のＢｒｉｘ値は、４５．０％以上７５．０％以下であり、下限値は好ましくは４８．０％以上であり、より好ましくは５０．０％以上であり、さらに好ましくは５５％以上であり、また上限値は好ましくは７３．０％以下であり、より好ましくは７０．０％以下であり、さらに好ましくは６７．０％以下である。液状品質改良剤のＢｒｉｘ値が上記範囲を下回ると、酵素活性を十分に維持することができない。液状品質改良剤のＢｒｉｘ値が上記範囲を超えると、極端に高粘度となり、米飯原料と混合しづらく好ましくない。液状品質改良剤中のＢｒｉｘ値の調製は一般的に食品に使用されているものを配合することで調製でき、マルトース等の糖類を使用することが、風味の面で好ましい。
なお、液状品質改良剤のＢｒｉｘ値は、２０℃で、屈折計を用いて測定した値であり、２０℃のショ糖水溶液の質量百分率に相当する値である。
(Brix value of liquid quality improver)
The Brix value of the liquid quality improver is 45.0% or more and 75.0% or less, and the lower limit is preferably 48.0% or more, more preferably 50.0% or more, and still more preferably 55%. % or more, and the upper limit is preferably 73.0% or less, more preferably 70.0% or less, and still more preferably 67.0% or less. If the Brix value of the liquid quality improver is below the above range, the enzymatic activity cannot be sufficiently maintained. If the Brix value of the liquid quality improver exceeds the above range, the viscosity of the liquid quality improver becomes extremely high, making it difficult to mix with the cooked rice material. The Brix value in the liquid quality improver can be prepared by blending those commonly used in foods, and the use of saccharides such as maltose is preferable from the standpoint of flavor.
The Brix value of the liquid quality improver is a value measured at 20°C using a refractometer and corresponds to the mass percentage of the sucrose aqueous solution at 20°C.
（酵素）
本発明においては、酵素として、少なくとも、αアミラーゼ及びグルコースオキシダーゼを用いる。米飯の添加酵素としてαアミラーゼ及びグルコースオキシダーゼの２種を併用することで、米飯表面の粘り及び粒感の両方を改善することができ、舌触りが滑らかで、かつ程よい硬さを持つ、非常に好ましい品質の米飯となる。αアミラーゼのみを用いると、米飯表面の粘りを改善させることはできるが、粒感が損なわれた米飯となってしまう。一方、グルコースオキシダーゼのみを用いると、米飯の粒感を改善することはできるが、全体としてざらざらとした舌触りの悪い米飯となってしまう。
(enzyme)
In the present invention, at least α-amylase and glucose oxidase are used as enzymes. By using α-amylase and glucose oxidase together as additive enzymes for cooked rice, both the stickiness and graininess of the surface of the cooked rice can be improved, and the texture is smooth and has moderate hardness, which is very preferable. It becomes quality rice. The use of α-amylase alone can improve the stickiness of the surface of the cooked rice, but the cooked rice loses graininess. On the other hand, if only glucose oxidase is used, the texture of the cooked rice can be improved, but the cooked rice as a whole will be rough and have a bad texture.
α－アミラーゼとは、澱粉のα－１，４－結合を不規則に切断し、多糖、マルトース、オリゴ糖に分解する酵素である。米飯にα－アミラーゼを添加することで、澱粉であるアミロースを分解することにより、米飯表面の粘りを改善させることができる。なお、本発明において用いるα－アミラーゼは市販品であってもよく、酵素活性は例えば５０００００～１０００００００Ｕ／ｇのものを用いることができる。 α-Amylase is an enzyme that randomly cleaves α-1,4-bonds of starch to decompose it into polysaccharides, maltose and oligosaccharides. By adding α-amylase to cooked rice, the stickiness of the surface of cooked rice can be improved by decomposing amylose, which is starch. The α-amylase used in the present invention may be a commercial product, and those with an enzymatic activity of, for example, 500,000 to 1,000,000 U/g can be used.
液状品質改良剤中のα－アミラーゼの含有量は、液状品質改良剤全体に対して、好ましくは０．０１質量％以上５質量％以下であり、より好ましくは０．０５質量％以上２質量％以下であり、さらに好ましくは０．１質量％以上１質量％以下である。α－アミラーゼの含有量が上記数値範囲内であれば、米飯の品質を改善する酵素活性を十分に維持することができる。 The content of α-amylase in the liquid quality improver is preferably 0.01% by mass or more and 5% by mass or less, more preferably 0.05% by mass or more and 2% by mass, based on the total liquid quality improver. or less, more preferably 0.1% by mass or more and 1% by mass or less. If the α-amylase content is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.
グルコースオキシダーゼとは、グルコース、酸素、水を基質としてグルコン酸と過酸化水素を生成する反応を触媒する活性を有する酵素である。当該反応により生成された過酸化水素は、タンパク質中のＳＨ基を酸化することでＳ－Ｓ結合（ジスルフィド結合）生成を促進し、タンパク質中に架橋構造を形成するものと推定している。グルコースオキシダーゼは、微生物由来、植物由来のものなど種々の起源のものが知られているが、本発明において用いるグルコースオキシダーゼは、上述の活性を有すればその起源は特に制限されず、いかなる起源のグルコースオキシダーゼであっても使用でき、また組み換え酵素を使用してもよい。米飯にグルコースオキシダーゼを添加することで、米飯の粒感を改良することができる。なお、本発明において用いるグルコースオキシダーゼは市販品であってもよく、酵素活性は例えば５００～５０００Ｕ／ｇのものを用いることができる。 Glucose oxidase is an enzyme that has the activity of catalyzing a reaction that produces gluconic acid and hydrogen peroxide using glucose, oxygen, and water as substrates. It is presumed that the hydrogen peroxide produced by this reaction oxidizes the SH groups in the protein, thereby promoting the formation of SS bonds (disulfide bonds) and forming a crosslinked structure in the protein. Glucose oxidase is known to have various origins such as those derived from microorganisms and plants, but the origin of glucose oxidase used in the present invention is not particularly limited as long as it has the above-mentioned activity, Even glucose oxidase can be used, and recombinant enzymes can also be used. Addition of glucose oxidase to cooked rice can improve graininess of the cooked rice. The glucose oxidase used in the present invention may be a commercial product, and one having an enzymatic activity of, for example, 500 to 5000 U/g can be used.
液状品質改良剤中のグルコースオキシダーゼの含有量は、液状品質改良剤全体に対して、好ましくは０．００１質量％以上１質量％以下であり、より好ましくは０．００３質量％以上０．５質量％以下であり、さらに好ましくは０．００５質量％以上０．１質量％以下である。グルコースオキシダーゼの含有量が上記数値範囲内であれば、米飯の品質を改善する酵素活性を十分に維持することができる。 The content of glucose oxidase in the liquid quality improver is preferably 0.001% by mass or more and 1% by mass or less, more preferably 0.003% by mass or more and 0.5% by mass, relative to the entire liquid quality improver. % or less, more preferably 0.005 mass % or more and 0.1 mass % or less. If the content of glucose oxidase is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.
（食酢）
本発明の液状品質改良剤は、食酢を含むものである。酢酸を含有する原料として食品由来の食酢を使用することで、米飯本来の風味を損なうことなく、微生物の増殖を抑えることができる。食酢としては、米、麦芽、酒粕等の穀類、ブドウ、リンゴ等の果実、タマネギ、ニンジン、トマト等の野菜、その他農産物、アルコール等を酢酸発酵させたものである。このような食酢としては、例えば、米酢、黒酢、五穀酢、ワインビネガー、リンゴ酢、及びトマト酢等が挙げられる。これらの食酢は、１種単独で用いてもよいし、２種以上を併用してもよい。
(vinegar)
The liquid quality improver of the present invention contains vinegar. By using food-derived vinegar as a raw material containing acetic acid, the growth of microorganisms can be suppressed without impairing the original flavor of cooked rice. Vinegar is obtained by acetic acid fermentation of grains such as rice, malt and sake lees, fruits such as grapes and apples, vegetables such as onions, carrots and tomatoes, other agricultural products, and alcohol. Examples of such vinegar include rice vinegar, black vinegar, five grain vinegar, wine vinegar, apple vinegar, and tomato vinegar. These vinegars may be used individually by 1 type, and may use 2 or more types together.
食酢の酢酸含有量は特に限定されないが、例えば、１０質量％以上２０質量％以下であり、下限値は好ましくは１３質量％以上であり、より好ましくは１５質量％以上であり、また、上限値は好ましくは１９質量％以下であり、より好ましくは１８質量％以下である。なお、本発明において用いる食酢は市販品であってもよい。なお、食酢の酢酸含有量は、上述の液状品質改良剤の酢酸含有量の測定方法と同様にして測定することができる。 The acetic acid content of the vinegar is not particularly limited, but is, for example, 10% by mass or more and 20% by mass or less, the lower limit is preferably 13% by mass or more, more preferably 15% by mass or more, and the upper limit is is preferably 19% by mass or less, more preferably 18% by mass or less. Incidentally, the vinegar used in the present invention may be a commercially available product. The acetic acid content of vinegar can be measured in the same manner as the method for measuring the acetic acid content of the liquid quality improver described above.
液状品質改良剤中の食酢の含有量は、液状品質改良剤全体に対して、好ましくは５質量％以上５０質量％以下であり、より好ましくは１０質量％以上４５質量％以下であり、さらに好ましくは１５質量％以上４０質量％以下である。食酢の含有量が上記数値範囲内であれば、米飯の品質を改善する酵素活性を十分に維持しつつ、同時に添加した米飯の微生物増殖も抑制することができる。 The content of vinegar in the liquid quality improver is preferably 5% by mass or more and 50% by mass or less, more preferably 10% by mass or more and 45% by mass or less, and still more preferably, based on the total liquid quality improver. is 15% by mass or more and 40% by mass or less. If the content of the vinegar is within the above numerical range, it is possible to sufficiently maintain the enzyme activity that improves the quality of the cooked rice, and at the same time suppress the growth of microorganisms in the cooked rice added.
（有機酸塩）
本発明の液状品質改良剤は、有機酸塩を含むものである。有機酸塩としては、酢酸、クエン酸、乳酸、フマル酸、酒石酸、リンゴ酸、及びグルコン酸塩等の有機酸の塩（例えば、ナトリウム、カリウム、カルシウム等）が挙げられる。これらの中でも、酢酸ナトリウム、クエン酸ナトリウム、乳酸ナトリウム、フマル酸ナトリウム、酒石酸ナトリウム、リンゴ酸ナトリウム、グルコン酸ナトリウム等を用いることが好ましく、さらに酢酸ナトリウム、クエン酸ナトリウムを用いると米飯の品質改良の点で好ましい。これらの有機酸塩は、１種単独で用いてもよいし、２種以上を併用してもよい。
(Organic acid salt)
The liquid quality improver of the present invention contains an organic acid salt. Organic acid salts include salts of organic acids such as acetic acid, citric acid, lactic acid, fumaric acid, tartaric acid, malic acid, and gluconate (eg, sodium, potassium, calcium, etc.). Among these, it is preferable to use sodium acetate, sodium citrate, sodium lactate, sodium fumarate, sodium tartrate, sodium malate, sodium gluconate and the like. point is preferable. These organic acid salts may be used individually by 1 type, and may use 2 or more types together.
液状品質改良剤中の有機酸塩の含有量は、液状品質改良剤全体に対して、好ましくは１質量％以上２０質量％以下であり、より好ましくは３質量％以上１５質量％以下であり、さらに好ましくは５質量％以上１２質量％以下である。有機酸塩の含有量が上記数値範囲内であれば、米飯の品質を改善する酵素活性を十分に維持しつつ、同時に添加した米飯の微生物増殖も抑制することができる。 The content of the organic acid salt in the liquid quality improver is preferably 1% by mass or more and 20% by mass or less, more preferably 3% by mass or more and 15% by mass or less, relative to the entire liquid quality improver, More preferably, it is 5% by mass or more and 12% by mass or less. If the content of the organic acid salt is within the above numerical range, the growth of microorganisms in the cooked rice added at the same time can be suppressed while sufficiently maintaining the enzyme activity that improves the quality of the cooked rice.
（他の原料）
液状品質改良剤は、上述した原料以外に、本発明の効果を損なわない範囲で液状品質改良剤に通常用いられている各種原料を適宜選択して配合することができる。他の原料としては、例えば、酢酸、アミノ酸、食塩、甘味料、増粘剤等が挙げられる。これらの中でも、液状品質改良剤は、液状品質改良剤全体の質量に対して、好ましくは２質量％以上、より好ましくは３質量％以上１０質量％以下、より好ましくは４質量％以上８質量％以下の食塩を含むことが好ましい。食塩の含有量が上記数値範囲内であれば、米飯の品質を改善する酵素活性を十分に維持することができる。
(Other raw materials)
In addition to the raw materials described above, the liquid quality improver can be blended by appropriately selecting various raw materials commonly used for liquid quality improvers within a range that does not impair the effects of the present invention. Other raw materials include, for example, acetic acid, amino acids, salt, sweeteners, thickeners, and the like. Among these, the liquid quality improver is preferably 2% by mass or more, more preferably 3% by mass or more and 10% by mass or less, more preferably 4% by mass or more and 8% by mass, based on the total mass of the liquid quality improver. It is preferable to include the following salts. If the salt content is within the above numerical range, the enzymatic activity that improves the quality of cooked rice can be sufficiently maintained.
（液状品質改良剤の調製方法）
液状品質改良剤の調製方法は、特に限定されず、従来公知の方法により行うことができる。例えば、攪拌タンクに、清水、酵素、食酢、有機酸塩、及び食塩や甘味料等の他の原料を投入して、ミキサーを用いて均一に混合することにより、液状品質改良剤を調製することができる。
(Method for preparing liquid quality improver)
A method for preparing the liquid quality improver is not particularly limited, and a conventionally known method can be used. For example, fresh water, enzymes, vinegar, organic acid salts, and other raw materials such as salt and sweeteners are put into a stirring tank and uniformly mixed using a mixer to prepare a liquid quality improver. can be done.
（製造装置）
本発明の液状品質改良剤の調製には、通常の食品製造に使われる装置を用いることができる。このような装置としては、例えば、一般的な攪拌機、スティックミキサー、スタンドミキサー、ホモミキサー、ホモディスパー等が挙げられる。攪拌機の攪拌羽形状としては、例えばプロペラ翼、タービン翼、パドル翼、アンカー翼等が挙げられる。
(Manufacturing equipment)
For the preparation of the liquid quality improver of the present invention, equipment commonly used for food production can be used. Examples of such devices include general stirrers, stick mixers, stand mixers, homomixers, homodispers, and the like. Examples of the shape of the stirring blades of the stirrer include propeller blades, turbine blades, paddle blades, anchor blades, and the like.
＜米飯の製造方法＞
本発明の米飯の製造方法は、米飯原料に上記の液状品質改良剤を添加する工程を含むものである。得られる米飯の、上記方法で測定したｐＨが６．２０以下となるように、上記の液状品質改良剤の添加量を適宜調節すればよい。また、液状品質改良剤は、炊飯後の米飯の酢酸含有量が０．０３質量％以上となるように添加されることが好ましい。
<Method for producing cooked rice>
The method for producing cooked rice of the present invention includes the step of adding the liquid quality improver to the cooked rice raw material. The amount of the liquid quality improver to be added may be appropriately adjusted so that the obtained cooked rice has a pH of 6.20 or less as measured by the above method. Moreover, the liquid quality improver is preferably added so that the acetic acid content of the cooked rice is 0.03% by mass or more.
続いて、液状品質改良剤を添加した米飯原料を炊飯する工程を行うことで、米飯を得ることができる。炊飯の方法は、特に限定されず、従来公知の方法により行うことができる。さらに、得られた米飯を容器や包装材に収容または包装する工程を行ってもよい。 Subsequently, the cooked rice can be obtained by performing a step of cooking the cooked rice raw material to which the liquid quality improving agent is added. A method of cooking rice is not particularly limited, and a conventionally known method can be used. Furthermore, a step of accommodating or packaging the obtained cooked rice in a container or packaging material may be performed.
以下に、実施例と比較例を挙げて本発明をさらに詳細に説明するが、本発明は以下の実施例の内容に限定して解釈されるものではない。 EXAMPLES The present invention will be described in more detail below with reference to examples and comparative examples, but the present invention should not be construed as being limited to the contents of the following examples.
＜米飯用液状品質改良剤の調製＞
表１及び２に記載の配合割合に準じて、米飯用液状品質改良剤を調製した。具体的には、攪拌タンクに、マルトース、食酢（酢酸含有量１５質量％）、食塩、有機酸塩としてクエン酸ナトリウム及び／又は酢酸ナトリウム及び／又はリンゴ酸ナトリウム及び／又は乳酸ナトリウム、酵素としてαアミラーゼ（５０００００～５００００００Ｕ／ｇ）及び／又はグルコースオキシダーゼ（１０００～２０００Ｕ／ｇ）、５０％酢酸、清水を投入して、ミキサーを用いて均一に混合することにより、液状品質改良剤を調製した。得られた各米飯用液状品質改良剤について、１気圧、品温２０℃とした時に、ｐＨ測定器（株式会社堀場製作所製卓上型ｐＨメータＦ－７２）を用いてｐＨを測定したところ、ｐＨはいずれも３．５～５．５であった。
また、それぞれの液状品質改良剤について、αアミラーゼ及びグルコースオキシダーゼの酵素活性を表１及び２に示した。
<Preparation of liquid quality improver for cooked rice>
A liquid quality improver for cooked rice was prepared according to the blending ratios shown in Tables 1 and 2. Specifically, in a stirring tank, maltose, vinegar (acetic acid content: 15% by mass), common salt, sodium citrate and/or sodium acetate and/or sodium malate and/or sodium lactate as an organic acid salt, α as an enzyme Amylase (500,000 to 5,000,000 U/g) and/or glucose oxidase (1000 to 2000 U/g), 50% acetic acid, and pure water were charged and uniformly mixed using a mixer to prepare a liquid quality improver. For each of the obtained liquid quality improvers for cooked rice, the pH was measured using a pH measuring device (desktop pH meter F-72 manufactured by Horiba, Ltd.) at 1 atm and a product temperature of 20 ° C. were all 3.5 to 5.5.
Tables 1 and 2 show the enzymatic activities of α-amylase and glucose oxidase for each liquid quality improver.
（酢酸含有量の測定）
液状品質改良剤の酢酸含有量の測定方法は、以下の方法（中和滴定法：定量式）により算出した。まず、液状品質改良剤を正確に採り、イオン交換水で１０倍に希釈し、その希釈液（１００ｇ）に、指示薬として３．１％フェノールフタレイン溶液を２滴加え、力価既知の０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液で中和滴定して、下記式により、液状品質改良剤の酢酸含有量を求めた。結果を表１及び２に示した。
液状品質改良剤の酢酸含有量（質量％）＝｛（６０．０５×０．１×Ｆ×Ｖ）×１００｝／｛サンプル採取量（１０ｇ）×１０００｝
６０．０５：酢酸の分子量
０．１：水酸化ナトリウム溶液のモル濃度（ｍｏｌ／Ｌ）
Ｆ：０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液の力価
Ｖ：０．１ｍｏｌ／Ｌ水酸化ナトリウム溶液の滴定量（ｍＬ）
(Measurement of acetic acid content)
The acetic acid content of the liquid quality improver was calculated by the following method (neutralization titration method: quantitative formula). First, a liquid quality improver was accurately taken and diluted 10-fold with deionized water. Neutralization titration was carried out with a 1 mol/L sodium hydroxide solution, and the acetic acid content of the liquid quality improver was determined according to the following formula. The results are shown in Tables 1 and 2.
Acetic acid content of liquid quality improver (% by mass) = {(60.05 x 0.1 x F x V) x 100}/{sample collection amount (10 g) x 1000}
60.05: Molecular weight of acetic acid 0.1: Molar concentration (mol/L) of sodium hydroxide solution
F: titer of 0.1 mol / L sodium hydroxide solution V: titration volume (mL) of 0.1 mol / L sodium hydroxide solution
（Ｂｒｉｘ値の測定）
液状品質改良剤のＢｒｉｘ値は、デジタル屈折計（株式会社アタゴ製デジタル屈折計ＲＸ－７０００ｉ）を用い、２０℃に温度調整して測定した。結果を表１及び２に示した。
(Brix value measurement)
The Brix value of the liquid quality improver was measured by adjusting the temperature to 20° C. using a digital refractometer (Atago Digital Refractometer RX-7000i). The results are shown in Tables 1 and 2.
＜米飯の製造＞
市販の生米を洗米、水切りした後、生米の質量に対して１．５倍量の清水を加えて、常温で１時間浸漬した。その後、上記で調製し、４℃、２１日間保存した液状品質改良剤を、生米の質量に対して２．０質量％の割合となるように加え、全体が均一になるように十分に混合した。続いて、炊飯ジャーにより、常法に従い炊飯を行った。
<Production of cooked rice>
After washing and draining the commercially available uncooked rice, 1.5 times the mass of the uncooked rice was added with fresh water and immersed at room temperature for 1 hour. After that, the liquid quality improver prepared above and stored at 4°C for 21 days was added in a proportion of 2.0% by mass with respect to the mass of uncooked rice, and mixed well so that the whole was uniform. bottom. Subsequently, rice was cooked by a rice cooker in accordance with a conventional method.
実施例１の液状品質改良剤については、別途、生米の質量に対して５．０質量％の割合となるように加えた以外は同様にして炊飯を行った（実施例１－２）。
実施例５の液状品質改良剤については、別途、生米の質量に対して１．０質量％、及び１．３質量％の割合となるように加えた以外は同様にして炊飯を行った（実施例５－２、５－３）。
Rice was cooked in the same manner, except that the liquid quality improver of Example 1 was separately added in a proportion of 5.0% by mass with respect to the mass of uncooked rice (Example 1-2).
Rice was cooked in the same manner, except that the liquid quality improver of Example 5 was added separately at a rate of 1.0% by mass and 1.3% by mass with respect to the mass of uncooked rice ( Examples 5-2, 5-3).
＜米飯のｐＨ、酢酸含有量測定＞
米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえで、１気圧、品温２０℃とした時に、ｐＨ測定器（株式会社堀場製作所製卓上型ｐＨメータＦ－７２）を用いてｐＨを測定した。結果を表３及び４に示した。
また、米飯の酢酸含有量は、比較例１を除き０．０３質量％以上であった。
<Measurement of pH and acetic acid content of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of cooked rice, grind it with a mixer or the like so that the whole is uniform, and set it to 1 atmospheric pressure and a product temperature of 20 ° C. pH was measured using a desktop pH meter F-72). The results are shown in Tables 3 and 4.
Moreover, the acetic acid content of the cooked rice was 0.03% by mass or more, except for Comparative Example 1.
＜米飯の官能評価＞
上記で炊飯した米飯の食感について、訓練されたパネルにより、下記の基準で官能評価を行った。評価結果を表３及び４に示した。なお、下記の評価は、評価が３点以上であれば、良好な結果であるといえる。なお対照区とは、液状品質改良剤を加えることなく、上記と同様の方法で炊飯した米飯を指す。
［米飯の食感の評価基準］
４：対照区と比較し、米飯表面の粘り及び米飯の粒感のどちらも著しく改善されており、食感が非常に好ましかった。
３：対照区と比較し、米飯表面の粘り及び米飯の粒感のどちらも改善されており、食感が好ましかった。
２：対照区と比較し、米飯表面の粘りまたは米飯の粒感のどちらかが改善されておらず、食感改善が十分ではなかった。
１：対照区と比較し、米飯表面の粘り及び米飯の粒感のどちらも改善されておらず、食感が同等であった。
<Sensory evaluation of cooked rice>
The texture of the cooked rice cooked above was sensory evaluated by a trained panel according to the following criteria. Evaluation results are shown in Tables 3 and 4. In the following evaluation, if the evaluation is 3 points or more, it can be said that the result is good. The control section refers to rice cooked in the same manner as above without adding the liquid quality improver.
[Evaluation criteria for texture of cooked rice]
4: Compared to the control group, both the stickiness of the surface of the cooked rice and the graininess of the cooked rice were remarkably improved, and the texture was very favorable.
3: Compared to the control group, both the stickiness of the surface of the cooked rice and the texture of the cooked rice were improved, and the texture was favorable.
2: Compared to the control group, either the stickiness of the surface of the cooked rice or the grainy texture of the cooked rice was not improved, and the improvement of the texture was not sufficient.
1: Compared to the control group, neither the stickiness of the surface of the cooked rice nor the graininess of the cooked rice was improved, and the texture was equivalent.
＜米飯の日持ち評価＞
上記で炊飯した米飯の質量に対し、添加菌（バチルス・サブティリス（Bacillus subtilis））を約１０個／ｇとなるように、培養液を希釈したものを加えた後、２５℃で４８時間の培養を行った。その後、標準寒天培地に接種し、さらに３５℃で４８時間培養した後のコロニー数を測定した。評価結果を表３及び４に示した。
○：菌添加試験後の菌数が１０５ｃｆｕ以下であった。
×：菌添加試験後の菌数が１０５ｃｆｕ超であった。
<Evaluation of longevity of cooked rice>
After adding a diluted culture solution so that the amount of added bacteria (Bacillus subtilis) is about 10 / g with respect to the mass of the cooked rice, it is heated at 25 ° C. for 48 hours. cultured. After that, it was inoculated onto a standard agar medium and cultured at 35° C. for 48 hours, and then the number of colonies was measured. Evaluation results are shown in Tables 3 and 4.
○: The number of bacteria after the bacteria addition test was 10 5 cfu or less.
×: The number of bacteria after the bacteria addition test was over 10 5 cfu.
＜酵素活性残存率評価＞
［α‐アミラーゼ］
（使用試薬及び試液）
１）０．２ｍｏｌ／Ｌ酢酸緩衝液：
酢酸ナトリウム（３水和物）１３．６ｇを水に溶かして５００ｍＬとし、０．２ｍｏｌ／Ｌ酢酸溶液を用いてｐＨ５．７に調整した。
２）ヨウ素試液：
水に０．０５Ｍヨウ素溶液５ｍＬ、２５％ヨウ化カリウム溶液０．４ｍＬを加え、２０ｍＬとした。このヨウ素・ヨウ化カリウム溶液５ｍＬに６Ｎ塩酸を５．８ｍＬ加え、水で２５０ｍＬにした。
３）１．０％溶性デンプン溶液：
溶性デンプン（メルク社製、分析用特級試薬）２ｇを精密に量り、１０５℃で４時間加熱し、あらかじめ乾燥減量を測定した。乾燥物２ｇに相当する溶性デンプンを精密に量り、約２０ｍＬの水に懸濁した。この懸濁液を沸騰水約１００ｍＬ中に徐々に加え溶かした後、３０秒間穏やかに煮沸した。放冷後、上記で調製した０．５ｍｏｌ／Ｌ酢酸緩衝液（ｐＨ６．０）４０ｍＬを加え、水で２００ｍＬとした。
４）基質液：
上記で調製した１．０％溶性デンプン溶液１０ｍＬに水１ｍＬを加えて混和し、その液０．１ｍＬをとり、上記で調製したヨウ素試液１０ｍＬ中に入れ、直ちに混和して得られた空試験溶液の吸光度を波長６２０ｎｍで測定し、吸光度０．９～１．０を示した１．０％溶性デンプン溶液を選び、基質液として用いた。
<Enzyme activity residual rate evaluation>
[α-amylase]
(Reagents and reagents used)
1) 0.2 mol/L acetate buffer:
13.6 g of sodium acetate (trihydrate) was dissolved in water to make 500 mL, and the pH was adjusted to 5.7 using a 0.2 mol/L acetic acid solution.
2) Iodine test solution:
5 mL of 0.05 M iodine solution and 0.4 mL of 25% potassium iodide solution were added to water to make 20 mL. 5.8 mL of 6N hydrochloric acid was added to 5 mL of this iodine/potassium iodide solution, and the volume was adjusted to 250 mL with water.
3) 1.0% soluble starch solution:
2 g of soluble starch (manufactured by Merck & Co., special reagent for analysis) was weighed precisely, heated at 105° C. for 4 hours, and the loss on drying was measured in advance. Soluble starch corresponding to 2 g of dry matter was accurately weighed and suspended in about 20 mL of water. This suspension was slowly added to about 100 mL of boiling water and dissolved, followed by gentle boiling for 30 seconds. After standing to cool, 40 mL of the 0.5 mol/L acetate buffer (pH 6.0) prepared above was added, and the volume was made up to 200 mL with water.
4) Substrate solution:
Add 1 mL of water to 10 mL of the 1.0% soluble starch solution prepared above and mix, take 0.1 mL of the solution, put it in 10 mL of the iodine test solution prepared above, and immediately mix to obtain a blank solution. was measured at a wavelength of 620 nm, and a 1.0% soluble starch solution exhibiting an absorbance of 0.9 to 1.0 was selected and used as a substrate solution.
（活性測定法）
基質液１０ｍＬを正確にとり、４０℃の振とう恒温槽で１０分間振とうした後、これに質量で２０倍、イオン交換水を用い希釈した液状品質改良剤１ｍＬを正確に加え、直ちに振りまぜた後、４０℃で振とうした。反応開始より１分間経過ごとに、０．１ｍＬを分取し、あらかじめ用意したヨウ素試液１０ｍＬ中に入 れ、直ちに混和して試験溶液とした。試験溶液の青色が消失し、赤色に変色したときの吸光度Ａｔを波長６２０ｎｍで測定した。空試験溶液は試料溶液の代わりに水１ｍＬを用い、試験溶液と同様に操作して吸光度Ａｂを測定した。Ａｂ及びＡｔを用い、次式より酵素活性を求めた。単位は、酵素１ｇが基質液（溶性デンプン）のヨウ素による青色を１分間に１０％減少させる酵素活性を１Ｕ／ｇとした。
酵素活性（Ｕ／ｇ）＝（Ａｂ－Ａｔ）／Ａｂ × １００／１０ × １／ｔ × １／ｗ
ｔ：反応時間（分）
ｗ：２０倍希釈した液状品質改良剤１ｍＬ中の酵素の量（ｇ）
(Activity measurement method)
Exactly 10 mL of the substrate liquid was taken and shaken for 10 minutes in a constant temperature shaking bath at 40°C, and then 1 mL of the liquid quality improver diluted with ion-exchanged water (20 times by weight) was accurately added and immediately shaken. After that, it was shaken at 40°C. A 0.1 mL aliquot was taken every 1 minute from the start of the reaction, placed in 10 mL of an iodine test solution prepared in advance, and immediately mixed to obtain a test solution. The absorbance At when the blue color of the test solution disappeared and changed to red was measured at a wavelength of 620 nm. As a blank test solution, 1 mL of water was used instead of the sample solution, and the absorbance Ab was measured in the same manner as the test solution. Using Ab and At, the enzymatic activity was determined from the following formula. As a unit, 1 U/g was defined as the enzymatic activity of 1 g of the enzyme that reduces the blue color caused by iodine in the substrate solution (soluble starch) by 10% per minute.
Enzyme activity (U/g) = (Ab-At)/Ab x 100/10 x 1/t x 1/w
t: reaction time (minutes)
w: Amount (g) of enzyme in 1 mL of 20-fold diluted liquid quality improver
［グルコースオキシダーゼ］
グルコースを基質として、酸素存在下でグルコースオキシダーゼを作用させることで過酸化水素を生成させ、生成した過酸化水素にアミノアンチピリン及びフェノール存在下でペルオキシダーゼを作用させることで生成したキノンイミン色素が呈する色調を、波長５００ｎｍで測定し定量する。１分間に１μｍｏｌのグルコースを酸化するのに必要な酵素量を１Ｕ（ユニット）と定義した。これを、酵素の量（ｇ）で除した数字を、酵素活性（Ｕ／ｇ）とした。
[glucose oxidase]
Using glucose as a substrate, glucose oxidase is allowed to act in the presence of oxygen to produce hydrogen peroxide, and the produced hydrogen peroxide is allowed to act with peroxidase in the presence of aminoantipyrine and phenol to produce a color tone exhibited by a quinoneimine dye. , measured and quantified at a wavelength of 500 nm. The amount of enzyme required to oxidize 1 µmol of glucose per minute was defined as 1 U (unit). The enzyme activity (U/g) was obtained by dividing this by the amount (g) of the enzyme.
液状品質改良剤調整直後及び保存後（４℃、２１日間）のものについて、上記方法を用いて、α‐アミラーゼ及びグルコースオキシダーゼそれぞれの酵素活性を算出し、保存後の酵素活性を調整直後の酵素活性で除したものを、酵素活性残存率とし、以下の基準で評価した。評価結果を表３及び４に示した。 Immediately after preparation of the liquid quality improver and after storage (4°C, 21 days), the enzymatic activities of α-amylase and glucose oxidase were calculated using the above method, and the enzymatic activities of the enzymes immediately after adjustment after storage were calculated. The value divided by the activity was defined as the residual enzyme activity rate, which was evaluated according to the following criteria. Evaluation results are shown in Tables 3 and 4.
［酵素活性残存率の評価基準］
○：α‐アミラーゼ及びグルコースオキシダーゼ、両方の酵素活性残存率が８０％以上１００％以下であった。
△：α‐アミラーゼ及びグルコースオキシダーゼ、両方の酵素活性残存率が５０％以上であり、どちらか、または両方の酵素活性残存率が８０％未満であった。
×：α‐アミラーゼ及びグルコースオキシダーゼ、どちらかの酵素の残存率が５０％未満であった。
[Evaluation Criteria for Residual Enzyme Activity]
◯: Both enzyme activity residual rates of α-amylase and glucose oxidase were 80% or more and 100% or less.
Δ: Both of α-amylase and glucose oxidase had a residual enzyme activity rate of 50% or more, and either or both of them had a residual enzyme activity rate of less than 80%.
x: The residual rate of either α-amylase or glucose oxidase was less than 50%.
実施例１～１６の米飯用液状品質改良剤はいずれも、炊飯後米飯の食感の評価基準が４点であり、米飯の日持ち評価、及び酵素活性残存率評価についても良好な結果となった。
比較例１の米飯用液状品質改良剤は、酢酸含有量が３．０質量％であり、また、炊飯後の米飯のｐＨが６．２を上回っており、炊飯後米飯の日持ち評価が悪かった。
比較例２の米飯用液状品質改良剤は、αアミラーゼの酵素活性残存率は８０％以上１００％以下であったが、グルコースオキシダーゼを全く配合していないため、炊飯後米飯は、対照区と比較すると表面の粘りは改善されたが粒感が損なわれたものとなり、好ましくなかった。
比較例３の米飯用液状品質改良剤は、グルコースオキシダーゼの酵素活性残存率は８０％以上１００％以下であったが、αアミラーゼを全く配合していないため、炊飯後米飯は、対照区と比較すると粒感が改善したが、全体としてざらざらとした舌触りが悪いものとなり、好ましくなかった。
比較例４の米飯用液状品質改良剤は、Ｂｒｉｘ値が４５％を下回るため、αアミラーゼ及びグルコースオキシダーゼの酵素活性を十分に維持することができなかった。
All of the liquid quality improvers for cooked rice of Examples 1 to 16 had an evaluation standard of 4 points for the texture of the cooked rice after cooking, and good results were obtained for the evaluation of the shelf life of the cooked rice and the evaluation of the residual rate of enzyme activity. .
The liquid quality improver for cooked rice of Comparative Example 1 had an acetic acid content of 3.0% by mass, and the pH of the cooked rice after cooking was higher than 6.2. .
The liquid quality improver for cooked rice of Comparative Example 2 had an α-amylase enzymatic activity residual rate of 80% or more and 100% or less, but since it did not contain glucose oxidase at all, the cooked rice after cooking was compared with the control group. As a result, the stickiness of the surface was improved, but the graininess was impaired, which was not preferable.
In the liquid quality improver for cooked rice of Comparative Example 3, the enzyme activity residual rate of glucose oxidase was 80% or more and 100% or less, but since α-amylase was not blended at all, the cooked rice after cooking was compared with the control group. As a result, the graininess was improved, but the texture as a whole was rough and unfavorable.
Since the liquid quality improver for cooked rice of Comparative Example 4 had a Brix value of less than 45%, the enzymatic activities of α-amylase and glucose oxidase could not be sufficiently maintained.
Claims (9)
酢酸含有量が３．０質量％超であり、
炊飯後の米飯を以下の測定方法で測定したときのｐＨが６．２０以下となるように添加される、
米飯用液状品質改良剤において、
酵素及び有機酸塩を含み、
前記酵素が、αアミラーゼ及びグルコースオキシダーゼを含み、
Ｂｒｉｘ値が４５．０％以上７５．０％以下であることを特徴とする、
米飯用液状品質改良剤。
＜米飯のｐＨ測定方法＞
米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえで、１気圧、品温２０℃とした時にｐＨ測定器を用いて測定した値。 Contains vinegar,
The acetic acid content is more than 3.0% by mass,
It is added so that the pH of the rice after cooking is 6.20 or less when measured by the following measurement method.
In the liquid quality improver for cooked rice,
containing enzymes and organic acid salts,
the enzyme comprises α-amylase and glucose oxidase;
characterized by a Brix value of 45.0% or more and 75.0% or less,
Liquid quality improver for cooked rice.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.
請求項１に記載の液状品質改良剤。 characterized in that the liquid quality improver contains 2% by mass or more of salt,
The liquid quality improver according to claim 1.
請求項１または２に記載の液状品質改良剤。 The acetic acid content of the liquid quality improver is 7.0% by mass or less,
The liquid quality improver according to claim 1 or 2.
請求項１～３のいずれか一項に記載の液状品質改良剤。 The liquid quality improver is added so that the acetic acid content of the cooked rice is 0.03% by mass or more,
The liquid quality improver according to any one of claims 1-3.
請求項１～４のいずれか一項に記載の液状品質改良剤。 The acetic acid content of the vinegar is 10% by mass or more and 20% by mass or less,
The liquid quality improver according to any one of claims 1-4.
請求項１～５のいずれか一項に記載の液状品質改良剤。 The organic acid salt is at least one selected from the group consisting of acetate, citrate, lactate, fumarate, tartrate, malate, and gluconate,
The liquid quality improver according to any one of claims 1-5.
請求項１～６のいずれか一項に記載の液状品質改良剤。 characterized by containing two or more of the organic acid salts,
The liquid quality improver according to any one of claims 1-6.
請求項１～７のいずれか一項に記載の液状品質改良剤。 characterized in that the organic acid salts include acetates and citrates,
The liquid quality improver according to any one of claims 1-7.
米飯原料に請求項１～８のいずれか一項に記載の液状品質改良剤を添加する工程を含み、
以下の測定方法で測定したときのｐＨが６．２０以下であることを特徴とする、
米飯の製造方法。
＜米飯のｐＨ測定方法＞
米飯１質量部に対しイオン交換水を２質量部加え、ミキサー等で全体が均一となるように粉砕したうえで、１気圧、品温２０℃とした時にｐＨ測定器を用いて測定した値。 A method for producing cooked rice,
A step of adding the liquid quality improver according to any one of claims 1 to 8 to the cooked rice raw material,
characterized by having a pH of 6.20 or less when measured by the following measuring method,
A method for producing rice.
<Method for measuring pH of cooked rice>
Add 2 parts by mass of ion-exchanged water to 1 part by mass of boiled rice, pulverize with a mixer or the like so that the whole is uniform, and measure with a pH measuring instrument at 1 atmospheric pressure and 20°C product temperature.
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