Method for producing yogurt containing DHA

Abstract

To provide a yogurt for drink containing DHA, with a reduced strange taste caused by the oxidation of DHA.SOLUTION: A yogurt for drink containing DHA is produced by lactic acid fermentation in which the fermentation is stopped at a pH of 4.5-5.5 and the pH is then reduced to 3.7-4.4 with acid. It can achieve reduction in a strange taste caused by the oxidation of DHA.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method for suppressing the generation of off-flavors derived from DHA in yogurt containing DHA, and to a method for producing yogurt containing DHA using said method. [Background technology]

[0002] 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 relating to yogurt containing highly unsaturated fatty acids. It is described in this document that the inclusion of a certain amount of lauric acid can suppress the generation of off-flavors over time. In the examples relating to the preparation of yogurt, fermentation is performed up to pH 4.5. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication WO2019 / 171788 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to suppress the generation of off-flavors resulting from the oxidation of DHA in DHA-containing yogurt. [Means for solving the problem]

[0005] 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. As a result, they 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 with an acid, thereby completing the present invention.

[0006] That is, the present invention provides: (1) A method for producing 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 a pH of 4.5 to 5.5; 5. A process of adjusting the pH of the fermented product from step 4 to 3.7 to 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 a pH of 4.5 to 5.5; 5. A process of adjusting the pH of the fermented product from step 4 to 3.7 to 4.4 with an acid. This is regarding. Effect of the Invention

[0007] According to the present invention, in yogurt containing DHA, the generation of off-flavors resulting from the oxidation of DHA can be suppressed without any restrictions on the composition. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] 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 the 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.

[0009] 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 milk or an equivalent or higher non-fat milk solid content 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 more preferably 3.7 to 4.0. By stopping fermentation at an appropriate pH and then adjusting the pH to an appropriate level, the generation of off-flavors derived from PUFA can be suppressed.

[0010] It is desirable to stop fermentation by lowering the temperature. Usually, fermentation takes place at around 43°C, but fermentation can be stopped by lowering this to below 15°C. Fermentation can also be stopped by raising the temperature, but in this case the lactic acid bacteria may die.

[0011] The acid for adjusting the pH can be lactic acid, acetic acid, citric acid, phosphoric acid, or hydrochloric acid, and is preferably lactic acid. By selecting an appropriate acid, the generation of off-flavors due to the oxidation of PUFA can be suppressed.

[0012] In the present invention, since stirring is required in the step of adjusting the pH, it is preferable 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 in the step 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.

[0013] In the present invention, yogurt preferably 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 containing an appropriate amount of DHA, it is possible to obtain yogurt that can claim to have the physiological effects, etc., of DHA.

[0014] 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 so that the particle size is 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.

[0015] The oil-soluble emulsifier is effective in maintaining the stability of the water-in-oil emulsified oil composition. In the present invention, emulsifiers with HLB of 7 or less and lecithin are defined as oil-soluble emulsifiers. As the oil-soluble emulsifier, one or more selected from polyglycerin esters, sugar esters, sorbitan esters, monoglycerin fatty acid esters, and lecithin are preferable, and polyglycerin esters, sugar esters, distilled monoglycerides, and lecithin are more preferable, and polyglycerin esters are particularly preferable, and among them, polyglycerin condensed ricinoleic acid esters are most preferable. Note that polyglycerin condensed ricinoleate is sometimes abbreviated as PGPR.

[0016] 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.

[0017] 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℃ Equilibrium time: 240 seconds Cell: Glass cell Measurement angle: 173° Positioning method: Selecting the optimal position Automatic attenuation selection: Yes

[0018] 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 called 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.

[0019] The present invention can also be considered as an invention relating to a method for suppressing the generation of off-flavors in DHA-containing yogurt. Specifically, in the production of DHA-containing yogurt, the pH during fermentation is stopped at 4.5 to 5.5, and this is then adjusted to a pH of 3.7 to 4.4 with an acid.

[0020] 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 and 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 type emulsion, strictly speaking, the yogurt according to the present invention has a W / O / W double emulsion structure.) 5. Lactic acid bacteria are inoculated into 4 and fermentation is carried out (the fermentation temperature is about 43°C). 6 When the pH reaches 4.5-5.5, lower the product temperature to below 15°C to stop fermentation. 7. Adjust the pH to 3.7-4.4 using an acid solution. The following examples are provided to illustrate the embodiments of the present invention in more detail. EXAMPLES

[0021] Study 1: Preparation of a water-in-oil emulsified oil composition containing DHA A water-in-oil type emulsified oil composition containing DHA was prepared according to the formulation in Table 1-1. The preparation method was in accordance with "Preparation method of water-in-oil type emulsified oil composition containing DHA".

[0022] Table 1-1 Mixture TIFF0007675486000001.tif8483·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 Co., Ltd. The emulsifier used was polyglycerol condensed ricinoleic acid ester "CRS-75" manufactured by Sakamoto Pharmaceutical 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.

[0023] Method for preparing water-in-oil emulsified oil composition containing DHA 1. The raw materials classified as the aqueous phase were mixed to prepare the aqueous phase. The raw materials classified as the oil phase were mixed to prepare the oil phase. 2. The water phase was added to the stirred oil phase to create 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).

[0024] Study 2: Preparation of yogurt Yogurt samples were prepared according to the formulation 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.

[0025] Table 2-1 Mixture TIFF0007675486000002.tif7791·The pectin used was "GENU Pectin YM-115-HJ" manufactured by Sansho Corporation. The water-in-oil emulsified oil composition containing DHA prepared in Study 1 was used.

[0026] Yogurt preparation method 1 Raw materials classified as "fermentation section" were mixed in the recipe. 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 which fermentation was stopped and the pH after adjustment were the same, no pH adjustment was performed. 5 The mixture of ingredients classified as "syrup part" in the recipe was added and mixed. The mixture was filled into 6 containers and stored at 3 to 7°C.

[0027] Table 2-2 Fermentation and pH adjustment conditions

[0028] Sensory evaluation method for yogurt Three experienced panelists who are involved 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: There is 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.

[0029] 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".

[0030] Table 3-1 Mixture TIFF0007675486000003.tif8386 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 Co., Ltd. The emulsifier used was polyglycerol condensed ricinoleic acid ester "CRS-75" manufactured by Sakamoto Pharmaceutical 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.

[0031] Study 4: Preparation of yogurt 2 Yogurt samples were prepared according to the formulation 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.

[0032] Table 4-1 Mixture TIFF0007675486000004.tif8991·The pectin used was "GENU Pectin YM-115-HJ" manufactured by Sansho Corporation. 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.

[0033] Table 4-2 Fermentation and pH adjustment conditions TIFF0007675486000005.tif24133

[0034] Consideration When the fermentation pH was stopped at 3.7, the yogurt still had a bad flavor, even if the pH was subsequently adjusted. When the fermentation pH was 4.9-5.5, yogurt with good flavor could be obtained by adjusting the pH to 3.7-4.4 after fermentation.

Claims

1. 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 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.

2. 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.

3. 3. The method for producing yogurt according to claim 1 or 2, wherein the yogurt has fluidity.

4. 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 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.

Images