JP7562268B2 - Soy milk-containing beverage and method for suppressing flavor deterioration of soy milk-containing beverage - Google Patents

Description

The present invention relates to a soy milk-containing beverage, a method for inhibiting flavor deterioration thereof, and an agent for inhibiting flavor deterioration of a soy milk-containing beverage.

To date, a wide variety of dairy beverages have been developed to suit a wide variety of targets. Meanwhile, against the backdrop of issues such as milk allergies, the recent trend toward health consciousness and diversifying tastes, new soy milk-containing beverages are being developed to replace dairy beverages. So far, soy milk has been popular as a highly nutritious plant-based milk, and many products that can be stored at room temperature are on the market. However, it is known that soy milk and soy milk-containing beverages lose their flavor during storage because the grassy soy milk smell derived from soybeans becomes more noticeable and an undesirable flavor is created, making them difficult to drink. In response to this issue, for example, efforts have been made to impart a fruity flavor to soy milk to make it easier to drink, but this can also damage the original flavor of soy milk.

Therefore, various means have been tried to mask the undesirable soy milk odor. For example, Patent Document 1 discloses a technique for masking the soy milk odor, which uses sesquiterpenes extracted from lemon oil, which is generally known to be effective in masking odors, as an active ingredient. Patent Document 2 also shows that the grassy odor inherent to soybeans can be suppressed by blending roasted soybeans into the raw material of soy milk and adjusting the amount of methylpyrazines contained in the resulting soy milk. However, Patent Document 2 also describes that the amount of hexanal, which is the cause of the grassy odor, increases with the addition of roasted soybeans.
Furthermore, Patent Document 3 describes a flavoring composition intended to mask odors in a wide variety of beverages, specifically, blending the flavoring composition with various products containing milk components, and Patent Document 4 describes a flavoring composition for imparting a more palatable milk or dairy product-like flavor, and discloses a wide variety of components as its active ingredients. In the techniques described in Patent Documents 3 and 4, 2-nonanone is listed as one component that can be used in combination with multiple aroma components used in the flavoring composition.

JP 2004-105011 A JP 2017-169481 A JP 2004-168936 A JP 2005-15685 A

The object of the present invention is to provide a soy milk-containing beverage in which flavor deterioration during storage is suppressed without impairing the soy milk feel, and a means for providing such a soy milk-containing beverage.

The present inventors, while diligently studying flavors and the like that can suppress flavor deterioration of soy milk-containing beverages and new means for suppressing flavor deterioration, unexpectedly discovered that flavor deterioration can be suppressed when 2-nonanone, which is not normally contained in soy milk, is added to unflavored soy milk or soy milk-containing beverages, and thus completed the present invention. That is, the present invention includes the following aspects.
[1] A soy milk-containing beverage containing 2-nonanone.
[2] The soy milk-containing beverage according to [1] above, having a pH of 4.6 or less.
[3] The soy milk-containing beverage according to [1] or [2] above, which contains 0.08 to 3 ppm of 2-nonanone.
[4] A method for suppressing deterioration of the flavor of a soy milk-containing beverage, comprising a step of blending 2-nonanone into the soy milk-containing beverage.
[5] An agent for suppressing flavor deterioration of soy milk-containing beverages, which contains 2-nonanone.

The present invention can provide a soy milk-containing beverage in which flavor deterioration during storage is suppressed without compromising the soy milk feel, and a means for providing such a soy milk-containing beverage.

The present invention relates to a soymilk-containing beverage containing 2-nonanone. Since soymilk produced without using anything other than soybeans as a raw material does not usually contain 2-nonanone, the soymilk-containing beverage according to the present invention can be obtained by adding an appropriate amount of 2-nonanone. By containing 2-nonanone, the soymilk-containing beverage according to the present invention can suppress flavor deterioration during storage without impairing the soymilk feel. One of the reasons for this suppression of flavor deterioration is thought to be that 2-nonanone alone can mask the flavor of hexanal and the like, which contributes to flavor deterioration, with respect to soymilk-derived components in the soymilk-containing beverage. Therefore, 2-nonanone can also be used as a flavor improver for soymilk-containing beverages.
The content of 2-nonanone in the soymilk-containing beverage according to the present invention is preferably 0.08 to 3 ppm, more preferably 0.1 to 3 ppm, even more preferably 0.2 to 2 ppm, and particularly preferably 0.3 to 1 ppm. In the present invention, commercially available 2-nonanone may be blended into the soymilk-containing beverage, or a food or drink containing a known concentration of 2-nonanone may be blended into the soymilk-containing beverage. When the concentration of 2-nonanone in the soymilk-containing beverage is unknown, it can be measured by subjecting the beverage to GC/MS measurement according to the MVM (Multi Volatile Method) method using an MPS manufactured by Gestell under the conditions described in this example. 2-nonanone is known as one type of heating flavor generated by ultra-high temperature (UHT) sterilization of milk (Journal of the Japanese Society of Food Chemical Technology, Vol. 46, No. 9, September 1999).

The soymilk-containing beverage according to the present invention is not particularly limited as long as it contains, for example, soymilk, prepared soymilk, or soymilk beverages described in Notification No. 683 of the Ministry of Agriculture, Forestry and Fisheries dated March 29, 2018. The soymilk-containing beverage according to the present invention may be a mixture of soymilk powder as a raw material. In the soymilk-containing beverage according to the present invention, the soybean solid content is preferably 0.1 to 0.5% by mass, more preferably 0.2 to 0.4% by mass. The soybean solid content can be determined according to a calculation based on the raw materials used in the production of the soymilk-containing beverage. In the soymilk-containing beverage according to the present invention, the soybean protein content is not particularly limited, but is preferably 0.05 to 0.3% by mass, and more preferably 0.1 to 0.2% by mass. The soybean protein content can be determined, for example, by weighing out about 5 g of the soybean-containing beverage, determining the amount of nitrogen by the Kjeldahl method, and multiplying this by 5.71, and the percentage of the value obtained relative to the sample weight is the soybean protein content. In addition, in the soybean-containing beverage according to the present invention, the ratio of soybean solids (mass%):2-nonanone content (ppm) is preferably 10-1:1-10, and more preferably 8-1:1-8. In the soymilk-containing beverage according to the present invention, the soybean lipid content (contained in the soybean solids) is preferably 0.05-0.3% by mass, and more preferably 0.1-0.2% by mass.

Here, the soy-containing beverage according to the present invention preferably has a pH of 4.6 or less, more preferably 4.0 or less, and preferably 3.0 or more, and more preferably 3.3 or more. If the pH exceeds 4.6, the stability of the soy protein may be impaired and precipitation may increase, and if the pH is less than 2.6, the beverage may taste too sour, reducing drinkability.

Preferred embodiments of the soy milk-containing beverage according to the present invention include, but are not limited to, a soy milk-containing soft drink that contains 0.5 to 1.5 ppm of 2-nonanone, has a pH of 3.0 to 4.0, and has a soy solids content of 0.2 to 0.4% by mass.

The sugar content of the soymilk-containing beverage according to the present invention is synonymous with the Brix (also written as Brix or Bx) value. That is, in the present invention, the sugar content is the reading of a sugar refractometer at 20°C, and can be, for example, the solid content measured at 20°C using a product name "Digital Refractometer Rx-5000" (manufactured by Atago Co., Ltd.). The sugar content is not particularly limited, but is preferably 3 to 12°Bx, and more preferably 5 to 10°Bx.
The sugar content of the soy milk-containing beverage according to the present invention can be adjusted to the above value by using a known sweetener. For example, it is preferable to adjust the sugar content by using sugars such as sucrose, glucose, granulated sugar, fructose, lactose, maltose, fructose glucose liquid sugar, and glucose fructose liquid sugar; low-intensity sweeteners such as xylitol and D-sorbitol; and high-intensity sweeteners such as thaumatin, stevia extract, disodium glycyrrhizinate, acesulfame potassium, sucralose, aspartame, saccharin, neotame, and saccharin sodium, either alone or in combination of two or more of them, and it is particularly preferable to adjust the sugar content by using sucrose, fructose glucose liquid sugar, acesulfame potassium, sucralose, and aspartame, from the viewpoint of the taste such as natural sweetness and refreshing acidity required for soy milk-containing beverages.

In addition, the soy milk-containing beverage according to the present invention preferably contains a protein stabilizer. As the stabilizer, any thickening polysaccharide that can be used in foods and beverages can be used without particular limitation, and soy polysaccharides are particularly preferred. The thickening polysaccharides may be used alone or in combination of two or more. Although not particularly limited, examples of the thickening polysaccharides used include soy polysaccharides and pectin.
Soybean polysaccharides are water-soluble polysaccharides obtained from soybeans, and are mainly composed of hemicellulose and sugars such as galactose, arabinose, galacturonic acid, rhamnose, xylose, fucose, and glucose. These soybean polysaccharides can be obtained by extracting, purifying, and sterilizing okara (fibrous residue) produced during the production of soybean oil and isolated soybean protein from soybeans. Commercially available soybean polysaccharides may also be used, and examples of such soybean polysaccharides include those available under the trade names "SM-700", "SM-900", and "SM-1200" (all manufactured by San-Ei Gen F.F.I.).
The blending ratio of the stabilizer in the soymilk-containing beverage can be appropriately determined depending on the type of stabilizer, etc., within a range that does not impair the effects of the present invention. The blending ratio is not particularly limited, but for example, in order to maintain good protein stability and good flavor, the lower limit is usually 2 g/L, preferably 4 g/L, and the upper limit is usually 8 g/L, preferably 6 g/L, based on the total mass of the beverage. If the blending ratio of the stabilizer is increased, there is a risk that the flavor and texture specific to the stabilizer will become stronger.

In addition, an acidulant such as citric acid (e.g., trisodium citrate), phosphoric acid, lactic acid, malic acid, etc. may be added to the soy milk-containing beverage of the present invention. The amount of citric acid, phosphoric acid, lactic acid, and malic acid added is not particularly limited as long as it does not impair the object of the present invention, but it is preferable to add, for example, 0.05 to 0.5% by mass, preferably 0.1 to 0.3% by mass in the soy milk-containing beverage. Furthermore, the taste may be adjusted by adding minerals such as sodium, magnesium, potassium, and calcium, as necessary.
The water used in the present invention is not particularly limited, and for example, ion-exchanged water can be used.

The soy milk-containing beverage according to the present invention may also contain a milk component. The milk component may be derived from any raw milk, such as animal milk or plant milk. Examples of animal milk include cow's milk, goat's milk, sheep's milk, and horse's milk. Examples of the form of the milk component include whole milk, skim milk, whey, milk protein concentrate, buttermilk powder, unsweetened condensed milk, sweetened skim condensed milk, whole sweetened condensed milk, fresh cream, and fermented milk. Milk reconstituted from powdered milk or concentrated milk can also be used. Among these, skim milk is preferred, and skim milk powder is particularly preferred because of its ease of handling. The milk component may be derived from a single type of raw material or from several types of raw materials.
Furthermore, as long as the flavor, etc., of the soybean-containing beverage of the present invention is not impaired, fruit juice, for example, citrus fruit juice such as orange, lemon, grapefruit, etc., or fruit juice such as grape, peach, apple, banana, etc. may be added as an optional acidic component as necessary.
Furthermore, the soy milk-containing beverage according to the present invention may include liquid or paste-like fermented soy milk food and drink obtained by fermenting a raw material (such as soy milk) using lactic acid bacteria, yeast, or the like.
Furthermore, the soy milk-containing beverage according to the present invention may contain commonly used food additives such as sweeteners and flavorings not mentioned above, various nutritional components, various plant extracts, colorants, diluents, antioxidants, etc., so long as the purpose of the present invention is not impaired.
The soy milk-containing beverage of the present invention is not particularly limited as long as it is a beverage containing soy milk, and examples thereof include unadjusted soy milk, adjusted soy milk, soy milk beverages, soft drinks, coffee beverages, tea beverages, fruit beverages, sports drinks, health drinks, and alcoholic beverages.

The soy milk-containing beverage of the present invention can be obtained by appropriately mixing soy milk, the above-mentioned 2-nonanone, sweeteners, flavorings, various nutritional components, various plant extracts, colorants, diluents, antioxidants, and other food additives. In the production process of the soy milk-containing beverage of the present invention, a homogenization treatment or a sterilization treatment can be added as appropriate, as necessary.
The homogenization treatment can be usually carried out using a homogenizer. The homogenization conditions are not particularly limited and can be carried out according to a conventional method.
The method of sterilization is not particularly limited, and conventional methods such as plate sterilization, tubular sterilization, retort sterilization, batch sterilization, and autoclave sterilization can be used.
The soymilk-containing beverage of the present invention after sterilization can be filled into containers, for example, by hot-packing the beverage into containers and then cooling the filled containers, or by cooling the beverage to a temperature suitable for filling into containers and aseptically filling the containers that have been previously washed and sterilized.
The present invention will be described in more detail below with reference to examples and comparative examples, although the present invention is not limited to these examples in any way.

The following raw materials (components) were used in the following Examples and Comparative Examples.
Modified soy milk (consisting of soy milk with 18% soy solids and antioxidants)
High fructose corn syrup (55% isomerized sugar)
Soybean polysaccharides, pectin, 50% lactic acid, trisodium citrate, 2-nonanone, ion-exchanged water (solvent making up the remainder)

The methods for obtaining the analytical or calculated values of the content of each component are as follows.
≪1 Sugar content (Bx°)≫
The sugar content was measured on the samples at 20°C using a Digital Refractometer Rx-5000 (manufactured by Atago Co., Ltd.).
2. Acidity (anhydrous citric acid) (mass% (w/w%))
The acidity of citric acid in the entire beverage sample was measured by the following titration method. Specifically, the acidity of citric acid was determined by titration using a phenolphthalein indicator and sodium hydroxide according to the following procedure.
(1) Accurately weigh 5 to 15 g of beverage into a 200 mL Erlenmeyer flask and dilute to approximately 50 mL with water.
(2) Add a few drops of 1% phenolphthalein indicator to the diluted beverage and stir.
(3) While stirring the diluted beverage solution in the Erlenmeyer flask with a magnetic stirrer, a titration test is carried out by dropping 0.1 M sodium hydroxide in a 25 mL burette into the beverage solution, the end point of which is when the beverage solution in the Erlenmeyer flask remains red for 30 seconds.
(4) Calculate the citric acid acidity (%) based on the results of the titration test using the following formula.
Citric acid acidity (%) = A × f × (100/W) × 0.0064 Formula (1)
[In formula (1), A represents the titer (mL) of 0.1 M sodium hydroxide solution, f represents the titer of 0.1 M sodium hydroxide solution, and W represents the mass (g) of the sample. The value of "0.0064" multiplied in formula (1) represents the mass (g) of anhydrous citric acid equivalent to 1 mL of 0.1 M sodium hydroxide solution.]
In the titration test, a hydrogen ion concentration meter may be used instead of the phenolphthalein indicator. In this case, the end point of the titration test is when the pH of the beverage solution in the Erlenmeyer flask becomes 8.1.

<3 pH>
The pH was measured using a pH meter.
≪4 Soybean solid content (mass% (w/w%))≫
Soy solids were calculated based on the raw materials used to make each beverage sample.
≪5 Lipid (mass% (w/w%))≫
The lipid content of soy solids was calculated based on the raw materials used to produce each beverage sample.

<6. 2-nonanone content (ppm)>
In this example, the content of 2-nonanone was calculated based on the raw materials used in the production of each beverage sample. For beverages with unknown 2-nonanone concentrations, the concentration (ppm) of 2-nonanone in the beverage was measured by GC/MS using the MVM (Multi Volatile Method) method with a Gestell MPS under the following conditions:
Equipment: GC: 7890B manufactured by Agilent Technologies
MS: Agilent Technologies 5977BMSD
HS: MPS manufactured by Gerstel,
TUBE: Tenax TA, Carbopack B/X
Column: DB-WAX UI 0.25 mm x 30 m x 0.25 μm
Quantitative ion: 2-nonanone m/z=58
Temperature conditions: 40℃ (2 minutes) ~ 8℃/min → 240℃ (10 minutes)
Carrier gas flow rate: He 1 ml/min injection method. Splitless ion source temperature: 230° C.

<Preliminary Examination>
We investigated the masking effect of 2-nonanone on hexanal, which is known to be the causative substance of grassy odor in soy milk. For comparison, we also investigated the masking effect of ethyl lactate, which is known to be an aroma component, on hexanal.
First, 2-nonanone was added to 1 ppm hexanal-containing water (which has a grassy smell) to prepare two samples. Similarly, ethyl lactate was added to the hexanal-containing water to a concentration of 10 ppm. Two expert panelists performed a sensory evaluation of the grassy smell of each sample.
As a result, it was confirmed that the addition of 2-nonanone had an effect of reducing the grassy odor of the sample, but even when 10 ppm of ethyl lactate was added, no change in the scent of the sample was confirmed.
Therefore, this result suggests that 2-nonanone alone can mask the grassy smell of soymilk.

[Control Example 1]
A prepared liquid was produced by blending prepared soy milk to give a soybean solids content (including lipids) of 0.2% by mass, and adding stabilizers (soybean polysaccharides, pectin), acidulants (50% lactic acid, trisodium citrate), and fructose-glucose liquid sugar (55% isomerized sugar) to give the Bx, acidity, and pH shown in Table 1 below. The obtained prepared liquid was sterilized by flash sterilization at 95°C, and then filled into a PET bottle to obtain a packaged beverage sample. 2-nonanone was not detected in Control Example 1.
[Example 1]
A beverage sample was obtained in the same manner as in Control Example 1, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 0.1 ppm.
[Example 2]
A beverage sample was obtained in the same manner as in Control Example 1, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 0.3 ppm.
[Example 3]
A beverage sample was obtained in the same manner as in Control Example 1, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 1 ppm.
[Reference Example 1]
A beverage sample was obtained in the same manner as in Control Example 1, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 0.05 ppm.
[Reference Example 2]
A beverage sample was obtained in the same manner as in Control Example 1, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 5 ppm.

<Accelerated test 1>
The beverage samples obtained in Control Example 1, Examples 1 to 3, and Reference Examples 1 and 2 were each stored in an environment of 55° C. for 2 days to accelerate deterioration.
After accelerated aging, each beverage sample was cooled to 4°C and subjected to a sensory evaluation by five expert panelists using the beverage sample of "Control 1" as the standard, and the scores were averaged. The sensory evaluation criteria were as shown in Table 2 below.

加速試験１においては、「対照例１」を基準とし、このスコアを４点に調整した。専門パネリストに各飲料サンプルの「豆乳の青臭さ、油臭さ」、「豆乳感」、「おいしさ（総合評価）」を１～７点の７段階評価してもらい、専門パネリスト５名の評点の平均値の小数第２位を四捨五入したものを最終評点とした。なお、「おいしさ（総合評価）」は、飲料としての嗜好性を豆乳に起因する風味以外も加味し、総合的に評価したものである。各専門パネリスト間の評価には、ばらつきはなかった。加速試験１の官能評価結果は表３に示される。

In Accelerated Test 1, "Control Example 1" was used as the standard, and this score was adjusted to 4 points. Expert panelists were asked to rate each beverage sample on a 7-point scale from 1 to 7 for "grainy smell of soy milk, oily smell,""soy milk feel," and "taste (overall evaluation)," and the final score was determined by rounding the average of the scores of the five expert panelists to one decimal place. Note that "taste (overall evaluation)" was a comprehensive evaluation of the preference as a beverage, taking into account factors other than the flavor attributable to soy milk. There was no variation in the evaluations between the expert panelists. The sensory evaluation results of Accelerated Test 1 are shown in Table 3.

表３の結果から、大豆固形分０．２質量％で、２－ノナノンを０．１～１ｐｐｍ含有する場合に、豆乳の青臭さ、油臭さを抑えつつ、豆乳感やおいしさを向上させる傾向にあることが確認された。また、２－ノナノンにより、劣化耐久性及び嗜好性が改善される傾向にあることが確認された。

From the results in Table 3, it was confirmed that when the soybean solids content is 0.2 mass % and 2-nonanone is contained at 0.1 to 1 ppm, there is a tendency for the soymilk's texture and deliciousness to be improved while suppressing the grassy smell and oily smell. It was also confirmed that 2-nonanone tends to improve durability against deterioration and palatability.

[Control Example 2]
A prepared liquid was produced by blending prepared soy milk to give a soybean solids content (including lipids) of 0.4% by mass, and adding stabilizers (soybean polysaccharides, pectin), acidulants (50% lactic acid, trisodium citrate), and fructose-glucose liquid sugar (55% isomerized sugar) to give the Bx, acidity, and pH shown in Table 4. The obtained prepared liquid was sterilized by flash sterilization at 95°C, and then filled into a PET bottle to obtain a packaged beverage sample.
[Example 4]
A beverage sample was obtained in the same manner as in Control Example 2, except that 2-nonanone was added to the preparation so that the 2-nonanone concentration was 1 ppm.

<Accelerated test 2>
The beverage samples obtained in Control Example 2 and Example 4 were each stored in an environment of 55° C. for 2 days to accelerate deterioration.
After accelerated deterioration, each beverage sample was cooled to 4°C and subjected to a sensory evaluation by five expert panelists using the beverage sample of "Control Example 2" as the standard in the same manner as in Accelerated Test 1, and the scores were averaged. The sensory evaluation results of Accelerated Test 2 are shown in Table 5.

表５の結果から、大豆固形分０．４質量％で、２－ノナノンを１ｐｐｍ含有する場合に、豆乳の青臭さ、油臭さを抑えつつ、豆乳感やおいしさを向上させ、表３の結果と同様な劣化耐久性、嗜好性を確保できた。

As can be seen from the results in Table 5, when the soybean solids content was 0.4% by mass and 2-nonanone was contained at 1 ppm, the grassy smell and oily smell of the soymilk were suppressed while the soymilk texture and deliciousness were improved, and durability to deterioration and palatability similar to those of the results in Table 3 were ensured.

Here, in order to confirm that 2-nonanone alone (i.e., in the absence of other additives, etc.) contributes to improving the soymilk flavor of a soymilk-containing beverage, the masking effect of 2-nonanone on the deteriorated flavor occurring in soymilk was confirmed.
[Control Example 3]
Soy milk (Kikkoman Corporation's "Oishii Unadjusted Soy Milk") was stored unopened in an environment of 55°C for 5 days to accelerate deterioration, preparing Control Example 3. Note that this soy milk deteriorated more slowly under the conditions of the above-mentioned Accelerated Tests 1 and 2, and therefore the storage period was extended compared to those in the accelerated tests. The composition and physical properties of the beverage sample of Control Example 3 are shown in Table 6.
[Example 5]
A beverage sample was obtained in the same manner as in Control Example 3, except that 2-nonanone was added to Control Example 3 so that the 2-nonanone concentration was 1.0 ppm.
[Example 6]
A beverage sample was obtained in the same manner as in Control Example 3, except that 2-nonanone was added to Control Example 3 so that the 2-nonanone concentration was 2.0 ppm.

<Study test>
The beverage samples obtained in Control Example 3, Examples 5 and 6 were cooled to 4°C, and five expert panelists performed a sensory evaluation using the beverage sample of "Control Example 3" as the standard, and the scores were averaged. The sensory evaluation criteria were as shown in Table 2 above. The sensory evaluation results of the study test are shown in Table 6.

表６の結果から、豆乳含有飲料において、２－ノナノン単独で、すなわち他の添加物等を添加しなくても、豆乳に生じた劣化風味のマスキング効果を発揮して、豆乳風味改善に寄与することが分かった。この結果から、２－ノナノン単独で豆乳由来の青臭さ、油臭さを抑えることができ、劣化促進した豆乳含有飲料であっても、嗜好性を保つことができることが示唆された。

The results in Table 6 show that in soymilk-containing beverages, 2-nonanone alone, i.e., without the addition of other additives, etc., exerts a masking effect on the deteriorated flavor of soymilk and contributes to improving the flavor of soymilk. These results suggest that 2-nonanone alone can suppress the grassy odor and oily odor derived from soymilk, and that even in beverages containing deteriorated soymilk, the palatability can be maintained.

Claims (5)

A soy milk-containing beverage containing 0.08 to 1.5 ppm of 2-nonanone . The soy milk-containing beverage according to claim 1, having a pH of 4.6 or less. 3. The soy milk-containing beverage according to claim 1, which contains 0.08 to 1 ppm of 2-nonanone. A method for suppressing deterioration of the flavor of a soy milk-containing beverage, comprising the step of blending 2-nonanone into the soy milk-containing beverage (excluding cases where the soy milk-containing beverage contains 0.05 ppt to 2 ppb of (E)-6-nonenal). An agent that suppresses flavor deterioration in soy milk-containing beverages, including 2-nonanone (excluding those that contain (E)-6-nonenal as an active ingredient).