JP7675486B2 - Method for producing yogurt containing DHA - Google Patents

Description

The present invention relates to a method for suppressing the occurrence of off-flavors resulting from DHA in yogurt containing DHA, and to a method for producing yogurt containing DHA using the method.

Polyunsaturated fatty acids, such as DHA (docosahexaenoic acid) and EPA (eicosapentaenoic acid), have been attracting attention in recent years for their physiological effects. However, polyunsaturated fatty acids are easily oxidized and can produce off-flavors.
Patent Document 1 is an application related to yogurt containing highly unsaturated fatty acids. It is described in the patent document 1 that the generation of off-flavors over time can be suppressed by including a certain amount of lauric acid. In the examples related to the preparation of yogurt, fermentation is performed up to pH 4.5.

International Publication WO2019/171788 Brochure

The objective of the present invention is to suppress the occurrence of off-flavors resulting from the oxidation of DHA in yogurt containing DHA.

The present inventors have conducted extensive research to solve the problems. Patent Document 1 requires the inclusion of a specific amount of lauric acid, which may result in limitations on the formulation.
The present inventors have conducted extensive research into whether it is possible to easily suppress the generation of off-flavors resulting from the oxidation of DHA in DHA-containing yogurt using a simpler method, and have found that the generation of off-flavors resulting from the oxidation of DHA can be suppressed by stopping lactic acid fermentation at a pH of 4.5 to 5.5 and then further adjusting the pH to 3.7 to 4.4 using an acid, thereby completing the present invention.

That is, the present invention provides:
(1) A method for producing yogurt containing DHA by the following steps:
1. A step of preparing an aqueous phase having a water-soluble antioxidant dissolved therein;
2. A step of finely dispersing the aqueous phase of 1 in an oil phase containing DHA to a particle size of 300 nm or less to obtain a water-in-oil type emulsified oil composition;
3. A step of mixing the water-in-oil emulsified oil and fat composition of 2 as one of the raw materials with other raw materials including a dairy raw material, and carrying out lactic acid fermentation;
4. A step of stopping the lactic acid fermentation of 3 at pH 4.5 to 5.5;
5. A process of adjusting the pH of the fermented product from step 4 to 3.7-4.4 with an acid.
(2) The method for producing yogurt according to (1) above, wherein the amount of DHA in the yogurt containing DHA is 0.05 to 1.0% by mass.
(3) The method for producing yogurt according to (1) or (2) above, wherein the yogurt has fluidity.
(4) A method for suppressing the generation of off-flavors resulting from the oxidation of DHA in a yogurt containing DHA, comprising the steps of:
1. A step of preparing an aqueous phase having a water-soluble antioxidant dissolved therein;
2. A step of finely dispersing the aqueous phase of 1 in an oil phase containing DHA to a particle size of 300 nm or less to obtain a water-in-oil type emulsified oil composition;
3. A step of mixing the water-in-oil emulsified oil and fat composition of 2 as one of the raw materials with other raw materials including a dairy raw material, and carrying out lactic acid fermentation;
4. A step of stopping the lactic acid fermentation of 3 at pH 4.5 to 5.5;
5. A process of adjusting the pH of the fermented product from step 4 to 3.7-4.4 with an acid.
This is regarding.

According to the present invention, it is possible to suppress the occurrence of off-flavors resulting from the oxidation of DHA in yogurt containing DHA without any restrictions on the composition.

In the present invention, DHA is an abbreviation for docosahexaenoic acid, and EPA is an abbreviation for eicosapentaenoic acid.
In the present invention, containing DHA means containing an oil or fat that contains DHA as one or more of the constituent fatty acids of a triglyceride.
DHA and EPA are sometimes referred to as PUFAs (polyunsaturated fatty acids), and oils containing DHA and EPA are sometimes simply referred to as PUFA oils.

The present invention relates to a method for producing yogurt.
In the present invention, yogurt is synonymous with fermented milk, and refers to a product obtained by fermenting a raw material mixture containing cow's milk or an equivalent or greater amount of non-fat milk solids with lactic acid bacteria, etc. The present invention is characterized in that the pH during fermentation is stopped at 4.5 to 5.5, and then the pH is adjusted to 3.7 to 4.4 by adding an acid.
The pH during fermentation is preferably stopped at pH 4.7 to 5.5, and even more preferably pH 4.9 to 5.5. The pH is then adjusted to preferably 3.7 to 4.2, and even more preferably 3.7 to 4.0. By stopping fermentation at an appropriate pH and then adjusting the pH to an appropriate level, it is possible to suppress the generation of off-flavors derived from PUFAs.

It is best to stop fermentation by lowering the temperature. Usually, fermentation takes place at around 43°C, but fermentation can be stopped by lowering the temperature to below 15°C. Fermentation can also be stopped by raising the temperature, but in this case the lactic acid bacteria may be killed.

Acids that can be used to adjust the pH include lactic acid, acetic acid, citric acid, phosphoric acid, and hydrochloric acid, with lactic acid being more preferable. By selecting an appropriate acid, it is possible to suppress the generation of off-flavors resulting from the oxidation of PUFAs.

In the present invention, since stirring is required at the stage of adjusting the pH, it is desirable to apply the present invention to a product called a fluid yogurt for drinking. In addition, it is also possible to add solid matter such as fruit pulp or sugar to the yogurt at the stage of adjusting the pH.
In the present invention, "fluid yogurt for drinking" refers to yogurt or a food product mainly made of yogurt that is fluid enough to be eaten or drunk by tilting the container without using a spoon or the like.

In the present invention, it is preferable that the yogurt contains 0.05 to 1.0% by mass of DHA. This amount is more preferably 0.07 to 0.5% by mass, and even more preferably 0.1 to 0.3% by mass. By using an appropriate amount of DHA, it is possible to obtain yogurt that can claim to have the physiological effects, etc., of DHA.

In the present invention, the water-in-oil type emulsified oil composition must be formed by finely dispersing the water-soluble antioxidant dissolved in the oil phase containing DHA to a particle size of 300 nm or less. Here, the water phase refers to the water-soluble antioxidant dissolved in water, and may contain other water-soluble components as long as they do not interfere with the effects of the present invention. Specific examples of the water-soluble components include carbohydrates and organic acids.
The oil phase contains DHA and also contains other oil-soluble components, such as oil-soluble emulsifiers and oil-soluble antioxidants, within the scope of not impairing the effects of the present invention.
In order to prevent oxidation of DHA, it is common to use an oil-soluble antioxidant, but the use of an oil-soluble antioxidant is not essential in the present invention. As described above, the present invention is characterized in that the aqueous phase containing the water-soluble antioxidant dissolved in water is finely dispersed in the oil phase containing DHA.

Oil-soluble emulsifiers are effective in maintaining the stability of water-in-oil emulsified oil and fat compositions. In the present invention, emulsifiers with an HLB of 7 or less and lecithin are defined as oil-soluble emulsifiers. As the oil-soluble emulsifier, one or more selected from polyglycerol esters, sugar esters, sorbitan esters, monoglycerol fatty acid esters, and lecithin are preferred, and polyglycerol esters, sugar esters, distilled monoglycerides, and lecithin are more preferred, and polyglycerol esters are particularly preferred, of which polyglycerol condensed ricinoleate esters are the most preferred. Polyglycerol condensed ricinoleate is sometimes abbreviated as PGPR.

The concentration of the water-soluble antioxidant in the aqueous phase is preferably 30 to 50% by mass, more preferably 35 to 45% by mass, and even more preferably 38 to 43% by mass. The water-soluble antioxidant is preferably one or more selected from ascorbic acid or a salt thereof, and polyphenols, and even more preferably one or more selected from polyphenols. As the polyphenols, it is preferable to use a tea extract containing catechin as an active ingredient.
By using an appropriate type and concentration of the water-soluble antioxidant, it is possible to suppress off-flavors in the yogurt of the present invention.

The particle size of the aqueous phase dispersed in the oil phase can be measured by the following method.
Device name: Zetasizer Nano S,
Manufacturer: Malvern. 10 μl of the oil composition to be measured was diluted with 2 ml of hexane and measured. (The measurement results on the first day after sample preparation were used as the judgment index.)
Temperature: 20.0℃
Equilibration time: 240 seconds
Cell: Glass cell
Measurement angle: 173°
Positioning method: Selecting the optimal position
Automatic attenuation selection: Yes

In order to finely disperse the aqueous phase in the oil phase to a particle size of 300 nm or less, various emulsifiers can be used. Specifically, a high-pressure homogenizer, an ultrasonic emulsifier, or a two-liquid collision type emulsifier also known as a wet jet mill can be used. By using an appropriate emulsifier, a desired antioxidant oil composition can be obtained. The general emulsification conditions when using a high-pressure homogenizer are 30 to 40 MPa and 10 to 30 passes.
If no visible precipitate was observed, the particle size of the aqueous phase was 300 nm or less.

The present invention can also be understood as an invention relating to a method for suppressing the generation of off-flavors in DHA-containing yogurt.
Specifically, in the production of yogurt containing DHA, the pH during fermentation is kept at 4.5 to 5.5, and then the pH is adjusted to 3.7 to 4.4 with an acid.

Next, a method for producing yogurt according to the present invention will be described step by step as an example.
1. Prepare an aqueous phase by dissolving a water-soluble antioxidant in water. Prepare an oil phase, which contains an oil containing DHA as an essential component.
2. The aqueous phase is added to the oil phase, and emulsified using an emulsifier so that the particle size of the aqueous phase is 300 nm or less. In other words, the emulsion here is a water-in-oil type emulsion.
3. Prepare the yogurt ingredient mix (e.g. mix milk, milk powder, sugar).
4. Add the DHA-containing emulsion prepared in 2 to the mixture of yogurt raw materials in 3 and homogenize. (Since yogurt itself is an oil-in-water emulsion, strictly speaking, the yogurt of the present invention has a W/O/W double emulsion structure.)
5. Ferment 4 by inoculating it with lactic acid bacteria. (The fermentation temperature is about 43°C.)
6. When the pH reaches 4.5 to 5.5, the product temperature is lowered to below 15°C to stop fermentation.
7. Use an acid solution to adjust the pH to 3.7-4.4.
The following examples are provided to illustrate the embodiments of the present invention in more detail.

Study 1: Preparation of a water-in-oil type emulsified oil composition containing DHA According to the formulation in Table 1-1, a water-in-oil type emulsified oil composition containing DHA was prepared. The preparation method was in accordance with "Preparation method of a water-in-oil type emulsified oil composition containing DHA".

・水溶性抗酸化剤には、太陽化学株式会社製「サンフェノン９０S」を使用した。
・糖アルコールには、三菱商事フードテック社製「ソルビットT-70」を使用した。
・乳化剤には、阪本薬品工業株式会社製ポリグリセリン縮合リシノレイン酸エステル「CRS-75」を使用した。
・PUFA油にはDHAを３２．５質量％含有する油脂を使用した。
・水相の粒子径は３００ｎｍ以下であった。これは、沈殿を生じていないことから判断された。 Table 1-1 Mixture

The water-soluble antioxidant used was "Sunphenon 90S" manufactured by Taiyo Kagaku Co., Ltd.
- The sugar alcohol used was "Sorbit T-70" manufactured by Mitsubishi Corporation Foodtech.
The emulsifier used was polyglycerol condensed ricinoleic acid ester "CRS-75" manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.
The PUFA oil used contained 32.5% DHA by mass.
The particle size of the aqueous phase was less than 300 nm, as determined by the absence of precipitation.

Method 1 for preparing a water-in-oil type emulsified oil composition containing DHA: Raw materials classified as an aqueous phase were mixed to prepare an aqueous phase. Raw materials classified as an oil phase were mixed to prepare an oil phase.
2. The water phase was added to the oil phase while stirring to form a roughly water-in-oil emulsion.
3. The approximately water-in-oil emulsion of 2 was emulsified into a water-in-oil emulsion using a high-pressure homogenizer (37 MPa, 20 passes).

Study 2 Preparation of yogurt Yogurt samples were prepared according to the composition in Table 2-1 and the conditions in Table 2-2. The preparation method was in accordance with "○ Yogurt preparation method".
The obtained yogurt samples were evaluated according to the "Sensory Evaluation Method for Yogurt". The results are also shown in Table 2-2.

・ペクチンには三晶株式会社製の「GENU ペクチン YM-115-H-J」を使用した。
・DHAを含有する油中水型乳化油脂組成物は検討１で調製したものを使用した。 Table 2-1 Mixture

- For the pectin, we used "GENU Pectin YM-115-HJ" manufactured by Sansho Co., Ltd.
The water-in-oil emulsified oil composition containing DHA prepared in Study 1 was used.

Yogurt preparation method 1: The ingredients classified as the "fermentation portion" in the recipe were mixed.
2. The mixture of 1 was inoculated with lactic acid bacteria and fermented at 43°C.
3. Once the desired pH was reached, the fermentation vessel was placed in ice water to lower the product temperature to 15°C.
4. The pH was adjusted to a predetermined value using a 10% by mass lactic acid aqueous solution or a 10% by mass calcium carbonate aqueous solution. However, when the pH at the time of fermentation termination and the pH after adjustment were the same, the pH was not adjusted.
5. The mixture of ingredients classified as the "syrup part" in the recipe was added and mixed.
6. Fill into containers and store at 3-7°C.

Table 2-2 Fermentation and pH adjustment conditions

Sensory evaluation method for yogurt Three experienced panelists who are engaged in the development of yogurt daily tasted the yogurt samples and performed a sensory evaluation according to the following criteria. The results were finalized by consensus of the panelists.
5 points: Contains no PUFA oils and has a flavor comparable to regular yogurt.
4 points: Does not contain PUFA oils. There is a certain difference in flavor compared to regular yogurt, but it is acceptable.
3 points: Has a certain fishy smell that is unacceptable.
2 points: A strong fishy smell was detected.
1 point: An extremely strong fishy smell.
A score of 4 or above was considered a pass.

Study 3: Preparation of a water-in-oil type emulsified oil composition containing DHA 2
A water-in-oil type emulsified oil composition containing DHA was prepared according to the formulation in Table 3-1. The preparation method was in accordance with "Preparation method of water-in-oil type emulsified oil composition containing highly unsaturated fatty acid".

・水溶性抗酸化剤には、太陽化学株式会社製「サンフェノン９０S」を使用した。
・糖アルコールには、三菱商事フードテック社製「ソルビットT-70」を使用した。
・乳化剤には、阪本薬品工業株式会社製ポリグリセリン縮合リシノレイン酸エステル「CRS-75」を使用した。
・PUFA油にはDHAを３２．５質量％含有する油脂を使用した。
・水相の粒子径は３００ｎｍ以下であった。これは、沈殿を生じていないことから判断された。 Table 3-1 Mixture

The water-soluble antioxidant used was "Sunphenon 90S" manufactured by Taiyo Kagaku Co., Ltd.
- The sugar alcohol used was "Sorbit T-70" manufactured by Mitsubishi Corporation Foodtech.
The emulsifier used was polyglycerol condensed ricinoleic acid ester "CRS-75" manufactured by Sakamoto Pharmaceutical Industry Co., Ltd.
The PUFA oil used contained 32.5% DHA by mass.
The particle size of the aqueous phase was less than 300 nm, as determined by the absence of precipitation.

Study 4: Preparation of yogurt 2
Yogurt samples were prepared according to the formulations in Table 4-1 and the conditions in Table 4-2. The preparation method was in accordance with "○ Yogurt preparation method."
The obtained yogurt samples were evaluated according to the "Sensory Evaluation Method for Yogurt".

The results are also shown in Table 4-2.

・ペクチンには三晶株式会社製の「GENU ペクチン YM-115-H-J」を使用した。
・アスパルテームには味の素株式会社製の「ＰＡＬ ＳＷＥＥＴ ＤＩＥＴ(R)」を使用した。
・高度不飽和脂肪酸を含有する油中水型乳化油脂組成物は検討３で調製したものを使用した。 Table 4-1 Mixture

- For the pectin, we used "GENU Pectin YM-115-HJ" manufactured by Sansho Co., Ltd.
- The aspartame used was "PAL SWEET DIET(R)" manufactured by Ajinomoto Co., Inc.
The water-in-oil emulsified oil composition containing highly unsaturated fatty acids prepared in Study 3 was used.

Table 4-2 Fermentation and pH adjustment conditions

Discussion: When the fermentation was stopped at pH 3.7, the flavor of the yogurt was poor even if the pH was subsequently adjusted.
- When the fermentation was stopped at a pH of 4.9 to 5.5, yogurt with a good flavor was obtained by subsequently adjusting the pH to 3.7 to 4.4.

Claims (4)

A method for producing yogurt containing 0.05 to 0.3% by mass of DHA by the following steps.
1. A step of preparing an aqueous phase having a water-soluble antioxidant dissolved therein.
2. A step of finely dispersing the aqueous phase of step 1 in an oil phase containing DHA to a particle size of 300 nm or less to obtain a water-in-oil type emulsified oil composition.
3. A process of mixing the water-in-oil emulsified oil and fat composition of 2 as one of the raw materials with other raw materials including a dairy raw material, and carrying out lactic acid fermentation.
4. Process to stop lactic acid fermentation at pH 4.9 to 5.5.
5. The process of adjusting the pH of the fermented product, whose fermentation was stopped in step 4, to 3.7-4.4 with acid. A method for producing yogurt containing 0.05 to 0.18% by mass of DHA by the following steps.
1. A step of preparing an aqueous phase having a water-soluble antioxidant dissolved therein.
2. A step of finely dispersing the aqueous phase of step 1 in an oil phase containing DHA to a particle size of 300 nm or less to obtain a water-in-oil type emulsified oil composition.
3. A process of mixing the water-in-oil emulsified oil and fat composition of 2 as one of the raw materials with other raw materials including a dairy raw material, and carrying out lactic acid fermentation.
4. Process of stopping the lactic acid fermentation in 3 at pH 4.9 to 5.5.
5. The process of adjusting the pH of the fermented product, whose fermentation was stopped in step 4, to 3.7-4.4 with acid. The method for producing yogurt according to claim 1 or 2, wherein the yogurt has fluidity. A method for suppressing the generation of off-flavors resulting from the oxidation of DHA in yogurt containing 0.05 to 0.3% by mass of DHA, comprising the steps of:
1. A step of preparing an aqueous phase having a water-soluble antioxidant dissolved therein.
2. A step of finely dispersing the aqueous phase of step 1 in an oil phase containing DHA to a particle size of 300 nm or less to obtain a water-in-oil type emulsified oil composition.
3. A process of mixing the water-in-oil emulsified oil and fat composition of 2 as one of the raw materials with other raw materials including a dairy raw material, and carrying out lactic acid fermentation.
4. Process to stop lactic acid fermentation at pH 4.9 to 5.5.
5. The process of adjusting the pH of the fermented product, whose fermentation was stopped in step 4, to 3.7-4.4 with acid.