Citral-containing beverage comprising pyrroloquinoline quinone as flavor deterioration inhibitor

Abstract

An object of the present invention is to provide a new technique for inhibiting an off-odor of a citral-containing beverage. The present invention employs pyrroloquinoline quinone or a salt thereof.

Description

CITRAL-CONTAINING BEVERAGE COMPRISING PYRROLOQUINOLINE QUINONE AS FLAVOR DETERIORATION INHIBITOR

[0001] The present invention relates to a beverage containing citral and pyrroloquinoline quinone or a salt thereof, and a related method.

[0002] Citrus fruits such as lemon contain a large number of components. Among them, a plurality of components such as citral provide a characteristic aroma or taste of citrus fruits. Citral is used in applications such as a flavoring.

[0003] As described in Patent Literature (PTL) 1, it is known that citral in an aqueous solution such as a beverage or a perfume is reduced by heating or reduces over time during distribution or storage, and is converted into a cyclization product such as p-menthadien-8-ols, and then off-odor-causing substances such as p-methylacetophenone and p-cresol are generated. It has been found that in particular, reduction of citral proceeds rapidly under low pH conditions (for example, pH 4.0 or less), such as in acidic beverages.

[0004] Various substances have been used to inhibit the generation of such off-odor-causing substances. For example, in PTL 1, theaflavins, which are a type of polyphenol contained in black tea, are used for the inhibition.

[0005] Meanwhile, pyrroloquinoline quinone, also referred to as PQQ, is used in various fields such as beverages. For example, in PTL 2, PQQ is used to impart a fruity flavor to a non-alcoholic beer-taste beverage.

[0006] In addition, PTL 1 discloses a result that even when epigallocatechin gallate, which is known to be a polyphenol exhibiting a particularly strong antioxidative action, was added to a citral-containing acidic aqueous solution at a high concentration (60 ppm), the generation of p-cresol was not inhibited at all. PTL 1 also indicates that L-ascorbic acid (vitamin C), which is widely used as an antioxidant, added at a concentration of 5 ppm does not inhibit the generation of p-cresol. That is, it is difficult to infer, from the strength of the antioxidative action of a substance, the presence or absence of the effect of inhibiting the generation of the citral-derived off-odor-causing substance as well as the strength of the effect (concentration required for exhibiting the effect).

[0007] JP 2005-171116 AJP 2019-076045 A

[0008] As described above, although there are techniques for inhibiting the off-odor of a citral-containing beverage, when a large amount of a food raw material or a food additive is added for such a purpose, problems may be caused in terms of the influence on the flavor and appearance of the beverage and the transportation cost of the raw material, and therefore, the techniques are not necessarily satisfactory.

[0009] An object of the present invention is to provide a new technique for inhibiting an off-odor of a citral-containing beverage.

[0010] The present inventors have found that PQQ can strongly inhibit the generation of an off-odor of a citral-containing beverage, and thus completed the present invention.The present invention relates to the following, but is not limited thereto:1. A beverage containing citral and 5 ppb or more of pyrroloquinoline quinone or a salt thereof;2. The beverage according to item 1, wherein a content of pyrroloquinoline quinone or a salt thereof is from 5 to 1000 ppb;3. The beverage according to item 1, wherein a content of citral is from 0.01 to 30 ppm;4. The beverage according to any one of items 1 to 3, the beverage being an alcoholic beverage;5. The beverage according to any one of items 1 to 3, the beverage being a non-alcoholic beverage;6. The beverage according to any one of items 1 to 3, the beverage having a pH of 4.0 or less;7. A method for inhibiting an off-odor of a citral-containing beverage, the method including mixing raw materials so that the beverage contains 5 ppb or more of pyrroloquinoline quinone or a salt thereof; and8. An off-odor inhibitor for a citral-containing beverage, the off-odor inhibitor containing pyrroloquinoline quinone or a salt thereof.

[0011] The present invention can strongly inhibit an off-odor of a citral-containing beverage. Specifically, PQQ used in the present invention has a stronger effect of inhibiting the generation of an off-odor at a lower concentration than theaflavins known in the art.

[0012] The present invention also provides a unique citral deterioration product profile. In this regard, there are several known off-odor-causing substances generated by deterioration of citral, and examples thereof include α,p-dimethylstyrene, in addition to p-methylacetophenone and p-cresol. When α,p-dimethylstyrene is generated, p-cymen-8-ol, which is a molecule obtained by hydration of α,p-dimethylstyrene, is also generated, and p-cymen-8-ol has a low possibility of exhibiting an off-odor. More specifically, it has been reported that the smell threshold (concentration) of p-cymen-8-ol is 250 times or more higher than that of α,p-dimethylstyrene (Toshio Ueno, doctoral dissertation “Shokubutsu Polyphenol no Riyo ni Kansuru Syokuhinkagakuteki oyobi Syokuhinkinougakuteki Kenkyu (Studies on Use of Plant Polyphenols in Food Chemistry and Food Function)”, 2015). The present invention can preferentially generate p-cymen-8-ol having only a weak off-odor over α,p-dimethylstyrene having a strong off-odor. That is, the present invention can reduce the generation ratio of α,p-dimethylstyrene / p-cymen-8-ol, and as a result, can more efficiently inhibit the off-odor.

[0013] Hereinafter, the beverage of the present invention and a related method are described.Unless otherwise specified, “ppm” and “ppb” used in the present description mean ppm and ppb by weight / volume (w / v), and are synonymous with “mg / L” and “μg / L”, respectively.

[0014] The term “alcohol” described in the present description means ethanol unless otherwise specified.(Citral)The beverage of the present invention contains citral. Citral (also known as 3,7-dimethylocta-2,6-dienal, chemical formula: C10H16O) is a monoterpene having an aldehyde group. Citral contains geranial, which is a trans isomer, and neral, which is a cis isomer. Citral is a component contained in citrus fruits and having a lemon-like aroma, and generates an off-odor. The content of citral in the beverage of the present invention is preferably from 0.01 to 30 ppm, and more preferably from 0.1 to 20 ppm. The content of citral in the present description is the total amount of the two isomers, but the beverage of the present invention does not have to contain both geranial and neral. That is, the beverage of the present invention contains geranial, neral, or both of them.

[0015] The content of citral in the beverage of the present invention may be measured at an arbitrary time point by any known method, and can be analyzed, for example, by high performance liquid chromatography (HPLC) or gas chromatography / mass spectrometry (GC-MS). Even in a case where the deterioration of components has progressed and decomposition of citral has progressed during distribution to the market and storage after production of the beverage, the content of citral at the time of production of the beverage can be estimated using the content of an initial cyclization product derived from citral, such as p-menthadien-8-ols and p-menth-2-ene-1,8-diol. Therefore, even if the content of citral is below the lower limit of quantification when the beverage is analyzed at an arbitrary time point after distribution, the citral concentration at the time of production of the beverage can be estimated.

[0016] In the present invention, the source of citral is not particularly limited, and for example, at least one material selected from the group consisting of citrus fruit, citrus peel, citrus fruit juices, processed products thereof, and citrus flavorings can be used. When such materials are used, the beverage of the present invention contains at least one material selected from the above-mentioned group.

[0017] Examples of citrus fruits for the fruit, peel, and fruit juices include orange, Citrus unshiu, grapefruit, lemon, lime, Citrus junos, Citrus iyo, Citrus natsudaidai, Citrus sudachi, Citrus hassaku, Citrus poonensis, Citrus depressa, and Citrus sphaerocarpa, and preferred citrus fruits are orange, lemon, grapefruit, and lime. One of these citrus fruits may be used alone, or two or more of these citrus fruits may be used in combination. For example, orange fruit juice and lemon fruit juice may be used, or orange peel and lemon fruit juice may be used.

[0018] In the present description, the “fruit juice” means a juice obtained from the fruit, and it may be in the form of a straight fruit juice that is a direct fruit juice obtained by squeezing the fruit, or a concentrated fruit juice obtained by concentrating the straight fruit juice. In addition, a transparent fruit juice or a cloudy fruit juice can also be used. A whole fruit juice obtained by crushing the whole fruit including the outer skin of the fruit and removing only particularly coarse and hard solids, such as seeds; fruit puree obtained by straining a fruit; or a fruit juice obtained by crushing or extracting the flesh of a dried fruit can also be used.

[0019] When the beverage of the present invention contains a citrus fruit juice, the content of the juice is not particularly limited, and is, for example, from 0 to 30 w / w% or from 0 to 20 w / w% in terms of percent fruit juice content. For confirmation, the content of the fruit juice in the present description means the total amount. Therefore, when the beverage contains only one type of citrus fruit juice, the content of the citrus fruit juice in the beverage of the present invention means the content of the fruit juice alone, and when the beverage contains a plurality of types of citrus fruit juices, the content means the total amount of the fruit juices.

[0020] In the present invention, the “percent fruit juice content” in the beverage is calculated by the following conversion formula using the amount (g) of the fruit juice blended in 100 ml of the beverage. The concentration factor is calculated in accordance with the JAS standards, and the sugar refractometer reading of sugars, honey, and the like added to the fruit juice is excluded.

[0021] Percent fruit juice content (w / w%) = <amount (g) of fruit juice added> × <concentration factor> / 100 mL / <density of beverage> × 100The beverage of the present invention may, but does not have to, contain a non-citrus plant raw material, that is, fruit, peel, and / or a fruit juice of a plant other than citrus fruits, in addition to a citrus raw material, that is, fruit, peel, and / or a fruit juice of citrus fruits. The type of such non-citrus plant raw material is not particularly limited, and examples thereof include apple, grape, peach, tropical fruits (pineapple, guava, banana, mango, acerola, lychee, papaya, passion fruit, and the like), Japanese apricot, pear, apricot, Japanese plum, berries, kiwifruit, strawberry, and melon. One of these non-citrus plant raw materials may be used alone, or two or more of these non-citrus plant raw materials may be used in combination. With respect to the fruit juice, the total content of the fruit juices including the citrus fruit juices in the beverage of the present invention is not particularly limited, and is, for example, 30 w / w% or less, or 20 w / w% or less in terms of percent fruit juice content. In one aspect, the beverage of the present invention does not contain a fruit juice of the fruit of a non-citrus plant.

[0022] The processed product obtained from the citrus fruit, citrus peel, and / or citrus fruit juice is not particularly limited, and examples thereof include an infused liquor and a freeze-crush-infused liquor of the fruit or peel. The former is obtained by immersing the fruit and / or peel in an alcohol-containing liquid for a certain period of time, and removing the insoluble matter from the obtained immersion liquid as necessary. The latter is obtained by freezing the fruit and / or peel, crushing the obtained frozen product, immersing the obtained crushed product in an alcohol-containing liquid for a certain period of time, and removing the insoluble matter from the obtained immersion liquid as necessary. A specific method for producing a freeze-crush-infused liquor is described, for example, in WO 2006 / 009252.

[0023] In the present invention, the term “citrus flavoring” means a flavoring containing an aromatic component contained in citrus fruits or a flavoring having a citrus aroma, and examples thereof include natural flavorings, food extracts, and synthetic flavorings. The above-mentioned examples of citrus fruits and preferred citrus fruits also apply to citrus flavorings. The beverage of the present invention may contain one type of citrus flavoring, or may contain two or more types of citrus flavorings.

[0024] When the beverage of the present invention contains a citrus flavoring, the content of the flavoring is not particularly limited, and is, for example, from 0 to 10000 ppm, or from 10 to 3000 ppm. For confirmation, the content means the total amount.

[0025] The content of the citrus flavoring in the beverage of the present invention may be measured at an arbitrary time point by any known method, and can be analyzed, for example, by high performance liquid chromatography (HPLC) or gas chromatography / mass spectrometry (GC-MS).

[0026] (Pyrroloquinoline quinone)The beverage of the present invention contains pyrroloquinoline quinone (PQQ, chemical formula: C14H6N2O8) or a salt thereof, or both of them.

[0027] The content of PQQ or a salt thereof in the beverage of the present invention is 5 ppb or more, preferably from 5 to 1000 ppb, more preferably from 10 to 1000 ppb, more preferably from 10 to 100 ppb, and more preferably from 50 to 100 ppb. For confirmation, the content means the total amount of PQQ and a salt thereof in the beverage.

[0028] If the content of PQQ or a salt thereof is low, the effect of inhibiting the off-odor tends to be low, and if the content is high, an undesirable taste in the beverage tends to be strong.The content of PQQ or a salt thereof in the beverage may be measured by any known method, and can be analyzed, for example, by high performance liquid chromatography (HPLC) or liquid chromatography mass spectrometry (LC / MS).

[0029] Examples of the salt of PQQ include alkali metal salts such as lithium salts, sodium salts, and potassium salts; alkaline earth metal salts such as magnesium salts and calcium salts; transition metal salts such as zinc salts, iron salts, cobalt salts, and copper salts; aluminum salts; organic amine salts such as choline salts, ethanolamine salts, triethanolamine salts, trimethylamine salts, triethylamine salts, dicyclohexylamine salts, dibenzylamine salts, phenethylbenzylamine salts, procaine salts, morpholine salts, pyridine salts, piperidine salts, piperazine salts, and N-ethylpiperidine salts; ammonium salts; and basic amino acid salts such as lysine salts and arginine salts. Preferred salts are sodium salts and potassium salts.

[0030] For confirmation, the scope of PQQ and a salt thereof as used herein also includes hydrates, such as salt hydrates. For example, a sodium salt such as pyrroloquinoline quinone disodium salt may form a trihydrate or a pentahydrate, and these are also included in the salt of PQQ in the present description.

[0031] (Alcohol)The beverage of the present invention may, but does not have to, contain an alcohol.When the beverage of the present invention contains an alcohol, that is, when the beverage is an alcoholic beverage, the alcohol content of the beverage is, for example, from 1 to 50 v / v%, or from 1 to 10 v / v%.

[0032] In the present description, the alcoholic strength of the beverage can be measured by any known method, and can be measured, for example, with a vibrating densimeter. Specifically, the alcoholic strength can be determined by preparing a sample from the beverage by removing carbonic acid gas as necessary through filtration or with ultrasonic waves, distilling the sample with water vapor, measuring the density of the resulting distillate at 15°C, and converting the density using “Dai 2 Hyo, Alcohol-bun to Mitsudo (15°C) oyobi Hiju (15 / 15°C) Kansanhyo (Table 2. Conversion Table of Alcohol Content, Density (15°C), and Specific Gravity (15 / 15°C))”, which is an attached table of the Official Analysis Method of the National Tax Agency (Hei 19 Kokuzei-cho Kunrei Dai 6 go (H19 National Tax Agency Order No. 6), revised on June 22, 2007).

[0033] When the alcohol content is low, other analysis methods such as gas chromatography may be used.When the beverage of the present invention is an alcoholic beverage, the alcohol may be added to the beverage by any means. Typically, the beverage contains an alcohol raw material, and thereby contains 1 v / v% or more of the alcohol. The alcohol raw material is not particularly limited, and examples thereof include spirits (rum, vodka, gin, tequila, and the like), liqueurs, whiskey, brandy, and shochu. The alcohol raw material may also be effervescent alcoholic beverages such as beer and Happosyu (low-malt beer), and brewed alcoholic beverages such as sake and fruit wine including wine. Preferably, the alcohol raw material is whiskey, brandy, or neutral spirits. These alcohol raw materials may be used alone or in combination.

[0034] When the present invention is an alcoholic beverage, the type thereof is not particularly limited, but the alcoholic beverage is preferably a chuhai (in the context of the present invention, it means an alcoholic carbonated beverage obtained by diluting a distilled alcoholic beverage with another beverage such as water, juice, or tea) and a concentrated liquid thereof, a cocktail (in the context of the present invention, it means a beverage containing spirits or a liqueur, a sour fruit juice such as a citrus fruit juice, a sweet component, and if necessary, carbonic acid), a sour (in the context of the present invention, it means a beverage containing spirits, a sour fruit juice such as a citrus fruit juice, a sweet component, and carbonic acid), or the like.

[0035] The present invention may be a non-alcoholic beverage, that is, a beverage having an alcohol content of less than 1 v / v%. The type of the non-alcoholic beverage is not particularly limited, and an example thereof is an alcoholic taste beverage having a taste similar to that of an alcoholic beverage. Examples of the alcoholic taste beverage include, but are not limited to, beer-taste beverages, chuhai-taste beverages, non-alcoholic cocktails, sour-taste beverages, wine-taste beverages, and Japanese sake-taste beverages. To give a more detailed description by raising a chuhai-taste beverage, a non-alcoholic cocktail, and a sour-taste beverage as examples, these beverages refer to beverages that realize tastes like a chuhai, a cocktail, and a sour as models, respectively, while being non-alcoholic. Another example of the non-alcoholic beverage of the present invention is a soft drink. Examples of the soft drink include, but are not limited to, carbonated beverages (including flavored water), fruit juice beverages, fruit and vegetable-based beverages, milk-based beverages, and lactic acid bacteria beverages.

[0036] (pH)In one aspect, the pH of the alcoholic beverage according to the present invention is 4.0 or less, preferably from 2.3 to 4.0, more preferably from 2.8 to 3.8, and still more preferably from 3.0 to 3.5. In the case of adjusting the pH of the beverage, the adjustment method is not particularly limited. The pH can be adjusted using a substance usually used for adjusting the pH of a beverage, such as citric acid or trisodium citrate, and the pH can also be adjusted by adjusting the contents of other components (for example, a fruit juice).

[0037] The present invention is particularly suitable for beverages having a pH in the above-mentioned range, since citral is prone to deterioration at a low pH.(Carbonic acid gas)The beverage of the present invention may contain carbonic acid gas. The carbonic acid gas can be added to the beverage using a method commonly known to those skilled in the art. Examples of such a method include, but are not limited to, a method of dissolving carbon dioxide in the beverage under pressure; a method of mixing carbon dioxide with the beverage in a pipeline using a mixer, such as a carbonator available from Tuchenhagen GmbH; a method of spraying the beverage into a tank filled with carbon dioxide to allow carbon dioxide to be absorbed into the beverage; and a method of mixing the beverage with carbonated water. The carbonic acid gas pressure is adjusted using these means appropriately.

[0038] When the beverage of the present invention contains carbonic acid gas, the carbonic acid gas pressure is not particularly limited, but is preferably from 0.7 to 4.5 kgf / cm2, and more preferably from 0.8 to 2.8 kgf / cm2. In the present invention, the carbonic acid gas pressure can be measured using Gas Volume Analyzer GVA-500A available from Kyoto Electronics Manufacturing Co., Ltd. For example, the temperature of a sample is set to 20°C, and the sample is subjected to degassing (snifting) and shaking in the air in the container of the Gas Volume Analyzer. Subsequently, the carbonic acid gas pressure is measured. In the present description, unless otherwise specified, the carbonic acid gas pressure means the carbonic acid gas pressure at 20°C.

[0039] (Other components)As long as the effects of the present invention are not impaired, to the beverage of the present invention, additives usually blended in beverages, such as a flavoring, a vitamin, a dye, an antioxidant, a preservative, a coloring agent, a seasoning, an extract, a pH adjuster, citric acid, or a quality stabilizer can be blended.

[0040] (Packaged beverage)The beverage of the present invention can be provided in a packaged form. Examples of the form of the package include, but are not limited to, a metal container such as a can; a PET bottle; a paper pack; a bottle; and a pouch. A sterilized packaged product can be produced, for example, by a method in which the beverage of the present invention is filled into a container and then subjected to heat sterilization such as retort sterilization, or a method in which the beverage is sterilized and filled into a container.

[0041] (Related method)In one aspect, the present invention is a method for producing a beverage containing citral and 5 ppb or more of pyrroloquinoline quinone or a salt thereof. The method includes mixing raw materials so that the beverage contains 5 ppb or more of pyrroloquinoline quinone or a salt thereof. The method may further include mixing raw materials so that the beverage contains citral.

[0042] Since the production method can inhibit the off-odor of a citral-containing beverage, the method is, in another aspect, a method for inhibiting an off-odor of a citral-containing beverage.Examples of the raw materials include citral or a raw material containing citral, pyrroloquinoline quinone or a raw material containing pyrroloquinoline quinone, water, and an alcohol.

[0043] The types of components in the beverage, and the content, pH, carbonic acid gas pressure, and preferred range thereof, as well as methods for adjusting them are as described above for the beverage of the present invention or self-evident from such descriptions. The timing is also not limited.

[0044] (Off-odor inhibitor)In one aspect, the present invention is an off-odor inhibitor for a citral-containing beverage, the off-odor inhibitor containing pyrroloquinoline quinone or a salt thereof. The content of pyrroloquinoline quinone or a salt thereof in the inhibitor is not limited as long as the inhibitory effect is exhibited. Meanwhile, the content of pyrroloquinoline quinone or a salt thereof in the beverage is preferably 5 ppb or more. A more preferred ranges of the content are as described above for the beverage.

[0045] The form of the inhibitor is not particularly limited, and may be a flavoring or a seasoning.(Numerical range)For clarification, numerical ranges in the present description include endpoints thereof, that is, the lower limit value and the upper limit value.

[0046] Hereinafter, the present invention will be described in more detail with reference to specific experimental examples, but the present invention is not limited to the following experimental examples.(Test Example 1) Effect of PQQ and theaflavin on generation of citral-derived off-odor componentCitral, ethanol, water, citric acid, and trisodium citrate were used to prepare a standard solution having a pH of 3.4, an alcohol content of 5 v / v%, and an initial citral concentration of 5 ppm (citric acid concentration: 10 mM). The source of citral was “Citral (Tronto Research Chemicals)”.

[0047] A part of the standard solution was taken and used as a control sample. Next, another part of the standard solution was divided into a plurality of parts, and an off-odor inhibiting material, that is, a salt of pyrroloquinoline quinone (PQQ) or a theaflavin was added to the parts at various concentrations to prepare a plurality of samples. The source of the salt of PQQ was pyrroloquinoline quinone disodium salt (FUJIFILM Wako Pure Chemical Corporation, hereinafter also referred to as “PQQ salt” or simply “PQQ”), and the source of the theaflavin was Theaflavin (FUJIFILM Wako Pure Chemical Corporation). The content of the PQQ salt or the theaflavin in each of the samples is shown in the following table.

[0048] Next, the control sample and the samples were stored in a glass vial (Mighty Vial, Maruemu Corporation) at 55°C for 5 days under a light-shielding condition so that the samples were deteriorated, and then the concentrations of p-cresol, p-methylacetophenone, and α,p-dimethylstyrene as off-odor-causing substances, and p-cymen-8-ol as a deterioration product in the samples were measured by analyzing the samples together with solutions of the substances having known concentrations using HPLC. Since the amount of p-cresol in the samples was very small, the samples were concentrated by solid phase extraction and then the concentration was measured. More specifically, 20 ml of each of the samples was added to a polymeric reverse phase filler (Oasis HLB Plus Short Cartridge (amount of filler: 225 mg, particle size: 60 μm) available from Waters Corporation) to adsorb p-cresol contained in the sample to the filler, 4 ml of ethanol was then passed through the filler using a syringe, p-cresol was desorbed to give an eluate, and the eluate was subjected to HPLC analysis.

[0049] The p-cresol and p-methylacetophenone contents (amounts generated) of each sample are shown in the following table in the form of relative amount (%) to the control sample.The weight ratio of the content of α,p-dimethylstyrene to the content of p-cymen-8-ol is shown in the column of “Dimethylstyrene / p-cymen-8-ol” in the following table.

[0050]

[0051] PQQ exhibited a stronger effect of inhibiting the generation of a citral-derived off-odor component than the theaflavin did.For example, when sample 1-4 is compared with sample 1-14, only a low concentration, which was as low as about 1 / 50 of that of the theaflavin, of PQQ was required to exhibit a comparable effect of inhibiting the generation of an off-odor component. That is, it can be said that PQQ is a component capable of inhibiting the off-odor in a small amount.

[0052] In addition, PQQ preferentially generates p-cymen-8-ol, which has a high smell threshold (concentration) and a low possibility of exhibiting an off-odor, over α,p-dimethylstyrene, which is a related substance having a strong off-odor. That is, PQQ reduced the generation ratio of α,p-dimethylstyrene / p-cymen-8-ol compared to the theaflavin. From this viewpoint too, it can be said that PQQ can more efficiently inhibit the off-odor.

[0053] Conditions of the HPLC analysis are as follows.Apparatus: Vanquish Binary Pump H (Thermo Fisher Scientific)Column: Unison UK-C18 HT 100 × 3 mm (particle size: 3 μm) (Imtakt Corporation)Temperature: 40°CMobile phase:(A) Ultrapure water (for LC / MS (FUJIFILM Wako Pure Chemical Corporation))(B) Acetonitrile (for LC / MS (FUJIFILM Wako Pure Chemical Corporation))Flow rate: 0.8 ml / min Gradient (%B): 0 min. 0% → 0.5 min. 0% → 4.5 min. 100% → 6.4 min. 100% → 6.5 min. 0% → 8 min. 0%Detection method: UV Wavelength: 280 nm (p-cresol), 254 nm (p-methylacetophenone), 240 nm (α,p-dimethylstyrene), 200 nm (p-cymen-8-ol)Injection volume: 5 μl(Test Example 2) Effect of PQQ on deterioration of citral added at high initial concentrationThe experiment was performed in the same manner as in Test Example 1 except that the initial concentrations of the PQQ salt and citral were changed. The alcohol content was 5 v / v%.

[0054] A sample containing no PQQ salt was used as a control, and the control and the sampleseach were stored at 55°C for 5 days under a light-shielding condition so that the control and the samples were deteriorated. After deterioration, relative concentrations of p-cresol and p-methylacetophenone of each of the samples to the control samples were measured. The initial citral concentration and the PQQ salt concentration of each sample, and the measurement results after deterioration are shown below.

[0055]

[0056] Even when the initial citral concentration was high, PQQ inhibited the generation of the off-odor-causing substance.(Test Example 3) Influence of ethanol contentThe experiment was performed in the same manner as in Test Example 1 except that the ethanol content was changed to 0.8 v / v%. The initial citral concentration was 5 ppm. Note that only 10 ppb and 50 ppb were used as the PQQ salt concentration.

[0057] A sample containing no PQQ salt was used as a control, and the control and the sampleseach were stored at 55°C for 5 days under a light-shielding condition so that the control and the samples were deteriorated. After deterioration, relative concentrations of components including p-cresol and p-methylacetophenone of each of the samples to the control sample were measured. The PQQ salt concentration of each sample and the measurement results after deterioration are shown below.

[0058]

[0059] Even though the ethanol content was changed to less than 1%, the same tendency as in Test Example 1 was observed.(Test Example 4) Influence of PPQ on tasteIn the same manner as in Test Example 1, citral, ethanol, water, citric acid, and trisodium citrate were used to prepare a standard solution having a pH of 3.4, an alcohol content of 5 v / v%, and an initial citral concentration of 5 ppm (citric acid concentration: 10 mM). The standard solution was used as a control sample. Next, a PQQ salt, which is an off-odor inhibiting material, was added to the standard solution at various concentrations to prepare a plurality of samples.

[0060] The obtained control sample and each of the samples without being deteriorated were subjected to sensory evaluation by three evaluators according to the following criteria. Next, the results of the sensory evaluation were discussed between the evaluators, and the evaluation was determined.

[0061] Criteria◎: There is no difference in taste quality as compared with the control.○: A difference in taste quality is observed as compared with the control, but the taste quality is within a range acceptable for drinking.

[0062] △: A difference in taste quality is observed as compared with the control, and the sample is not preferred for drinking.The PQQ salt concentration of each sample and the evaluation results are shown below.

[0063]

[0064] An artificial taste (grainy feeling) of the beverage tended to increase with increasing PQQ concentration, but the taste was sufficiently acceptable for drinking at PQQ concentrations equal to or less than a certain level.

Claims

1.A beverage comprising citral and 5 ppb or more of pyrroloquinoline quinone or a salt thereof.2.The beverage according to claim 1, wherein a content of pyrroloquinoline quinone or a salt thereof is from 5 to 1000 ppb.3.The beverage according to claim 1, wherein a content of citral is from 0.01 to 30 ppm.4.The beverage according to any one of claims 1 to 3, the beverage being an alcoholic beverage.5.The beverage according to any one of claims 1 to 3, the beverage being a non-alcoholic beverage.6.The beverage according to any one of claims 1 to 3, the beverage having a pH of 4.0 or less.7.A method for inhibiting an off-odor of a citral-containing beverage, the method comprising mixing raw materials so that the beverage contains 5 ppb or more of pyrroloquinoline quinone or a salt thereof.8.An off-odor inhibitor for a citral-containing beverage, the off-odor inhibitor comprising pyrroloquinoline quinone or a salt thereof.

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