JP2024122140A - Pre-fermented yogurt and its manufacturing method - Google Patents

Abstract

[Problem] To provide a pre-fermented yogurt that has a smooth and thick texture, is free of unpleasant flavors, and has the inherent rich flavor of milk.
[Solution] A pre-fermented yogurt, characterized in that the raw materials contain 60 to 97% by weight of raw milk and/or cow's milk, and contain at least one selected from the group consisting of skim milk, concentrated skim milk, and skim milk powder, and a milk protein concentrate (MPC).
[Selection diagram] None

Description

The present invention relates to pre-fermented yogurt and a method for producing the same.

Traditionally, yogurt has been noted for its health-promoting effects, but with the recent diversification of food, there has been a growing trend toward a preference for enjoying the texture and flavor of yogurt itself. In particular, there is a demand for a smooth, thick texture that also retains the rich flavor of milk, the main ingredient in yogurt.

There are two types of yogurt manufacturing methods: a pre-fermentation method in which a lactic acid bacteria starter is added to a yogurt mix, a mixture of yogurt ingredients, and fermented, and the curd formed by fermentation is crushed and then packed into containers; and a post-fermentation method in which a container is filled with a yogurt mix and a lactic acid bacteria starter, and then fermented in the container. Yogurt that requires a smooth and thick texture, such as liquid yogurt or soft yogurt, is usually manufactured by the pre-fermentation method, in which the yogurt is fermented, the curd is crushed, and then packed into containers.

Various methods have been proposed to impart a rich milk flavor to yogurt produced by a pre-fermentation method. For example, Patent Document 1 discloses that a pre-fermentation drink yogurt with a rich, satisfying taste can be obtained by adding a lactic acid bacteria starter to a fermented milk base containing milk proteins including whey protein, followed by fermentation, crushing and thickening to a specific particle size and viscosity. Patent Document 2 discloses that a fermented milk with a rich taste and excellent smoothness can be obtained by fermenting a milk preparation containing milk ingredients and concentrating the resulting fermented product under specified conditions.

However, the methods described in Patent Documents 1 and 2 both use mostly skim concentrated milk as a raw material for yogurt, and do not use raw milk or cow's milk. Although they achieve a rich milk flavor, they lose the original flavor of milk, and there is still room for improvement.

Patent Document 3 discloses a drinkable yogurt containing 70% raw milk that has not been subjected to any process such as concentration, and describes how smooth, uniform yogurt can be obtained without forming curds by adding a thermoreversible hydrocolloid that coagulates when heated to the raw material mixture. However, while the yogurt obtained by the method described in Patent Document 3 has an easy-to-sense milk flavor, it has an unnatural texture due to the thickening polysaccharides used.

JP 2020-22406 A JP 2017-60449 A JP 2015-156830 A

The objective of the present invention is to provide a pre-fermented yogurt that has a smooth, thick texture and is free of unpleasant flavors and has the rich, natural flavor of milk.

As a result of intensive research conducted by the inventors to solve the above problems, they discovered that a pre-fermented yogurt made from ingredients containing raw milk and/or cow's milk as the main ingredient, at least one selected from the group consisting of skim milk, concentrated skim milk, and skim milk powder, and milk protein concentrate (MPC) can provide a smooth, thick texture and a rich, natural milk flavor without any unpleasant flavors, and thus completed the present invention.

That is, the first aspect of the present invention relates to a pre-fermented yogurt, characterized in that the raw material contains 60 to 97% by weight of raw milk and/or cow's milk, and contains at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC). In the pre-fermented yogurt, the raw material may contain 14.5 to 18% by weight of milk solids and 4.5 to 6.5% by weight of milk protein. In the pre-fermented yogurt, the raw material may contain 18 to 22% by weight of whey protein in the milk protein. In the pre-fermented yogurt, the raw material may contain 0.5 to 7% by weight of at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and the milk protein concentrate (MPC) may contain 0.2 to 3% by weight by dry weight. In the pre-fermented yogurt, the median diameter of the curd may be 5 to 70 μm. The second aspect of the present invention relates to a method for producing a pre-fermented yogurt, which includes a step of heat-treating a yogurt mix containing 60 to 97% by weight of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC), a step of fermenting the heat-treated yogurt mix to which a lactic acid bacteria starter has been added until the pH reaches 4.1 to 4.85, and a step of crushing the curds of the fermented yogurt mix to a median diameter of 5 to 70 μm.

According to the present invention, it is possible to provide a pre-fermented yogurt that has a smooth and thick texture, is free of unpleasant flavors, and has the rich flavor of milk itself.

Hereinafter, an embodiment of the present invention will be described in detail.
The terms relating to milk and dairy products used in this specification will be explained.
- "Raw milk" refers to cow's milk in the state it is extracted.
"Milk" refers to cow's milk that is sold for direct consumption or for use in the manufacture or processing of food products using it as an ingredient, but does not include raw milk from which the milk fat and other components have been partially removed.
・"Special milk" refers to milk that is sold as special milk. Note that for "special milk", there are specific standards for the manufacturing method, even among "milk" (as stipulated in the "Ministry of Health and Welfare Ordinance No. 52 on December 27, 1951, "Ministry Ordinance on the Compositional Standards of Milk and Dairy Products").
"Skim milk" refers to raw milk, cow's milk, special cow's milk, or raw buffalo milk from which the milk fat has been removed. In this disclosure, low-fat milk and non-fat milk are included in skim milk.
"Skimmed concentrated milk" refers to milk that has been concentrated after removing the milk fat from raw milk, cow's milk, special cow's milk, or raw buffalo milk.
"Skimmed milk powder" refers to raw milk, cow's milk, special milk, or raw buffalo milk from which the milk fat has been removed (i.e., skimmed milk) from which almost all of the water has been removed and which has been made into a powder form.
"Milk Protein Concentrate (MPC)" generally refers to a product obtained by sterilizing skim milk, at least partially removing lactose and salts by membrane processing such as ultrafiltration membrane to concentrate milk protein, and then further heating, concentrating and drying as necessary. In this disclosure, milk protein concentrate (MPC) also includes milk protein concentrates obtained by similar production methods, such as milk protein isolate (MPI) and high-purity milk protein (TMP: Total Milk Protein), but does not include whey protein concentrate (WPC).
"Yogurt mix" refers to a mixture of yogurt ingredients, and in this disclosure, in particular, refers to a mixture of raw milk and/or cow's milk; at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder; milk protein concentrate (MPC); and other optional ingredients blended as necessary.

The yogurt disclosed herein is a pre-fermented yogurt that uses a specific amount of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and milk protein concentrate (MPC) as ingredients.

The content of the raw milk and/or cow's milk in the yogurt mix before fermentation, which is the raw material for yogurt, is preferably 60 to 97% by weight, more preferably 75 to 97% by weight, and even more preferably 90 to 97% by weight. If the content is less than 60% by weight, the rich flavor inherent to milk may be lacking. If the content is more than 97% by weight, it may be difficult to obtain a thick texture.

The type of raw milk and/or cow's milk used is not particularly limited, but from the viewpoint of enhancing the inherent rich flavor of milk, the protein reduction value of the raw milk and/or cow's milk is preferably 2 to 9, and more preferably 4 to 9.

Raw milk and milk may be used alone or in combination. When raw milk is used alone, the rich flavor of the milk is not lost during the pasteurization process, and a richer yogurt with a richer flavor of the milk can be obtained. When raw milk and milk are used in combination, the mixing ratio is not particularly limited, but it is preferable that the protein reduction value of the mixture of raw milk and milk is within the above range.

The protein reduction value can be measured by known methods. Examples of methods for measuring the protein reduction value include the method described in "Examination Methods for Dairy Products, Commentary, Edited by the Pharmaceutical Society of Japan" (Kanbara Publishing Co., Ltd., p. 131, published March 20, 1984).

In the yogurt of the present disclosure, the milk solids content in the yogurt mix before fermentation, which is the raw material for the yogurt, is preferably 14.5 to 18% by weight, more preferably 14.5 to 17% by weight, and even more preferably 15.5 to 16.5% by weight. When the milk solids content is 14.5% by weight or more, the inherent rich flavor of milk is felt more strongly compared to when the milk solids content is less than 14.5% by weight. When the milk solids content is 18% by weight or less, the smooth and thick texture is felt more strongly compared to when the milk solids content is more than 18% by weight.

The milk solids content refers to the total amount of milk fat and non-fat milk solids. The milk fat and non-fat milk solids contents can be measured based on the "Method for Quantitative Analysis of Milk Fat in Cow's Milk, Special Cow's Milk, Pasteurized Goat's Milk, Low-Fat Milk, Non-Fat Milk, and Processed Milk" (in other words, the Roese-Gottlieb Method) and "Method for Quantitative Analysis of Non-Fat Milk Solids in Milk and Dairy Products," which are quantitative methods described in the Ministry of Health, Labor and Welfare Ordinance No. 52 of Japan, "Ministerial Ordinance on the Compositional Standards of Milk and Dairy Products."

In the yogurt of the present disclosure, the milk protein content in the yogurt mix before fermentation, which is the raw material for the yogurt, is preferably 4.5 to 6.5% by weight, more preferably 4.5 to 6% by weight, and even more preferably 4.7 to 5.2% by weight. When the milk protein content is 4.5% by weight or more, the original rich flavor and thick texture of milk are felt more strongly compared to when the content is less than 4.5% by weight. When the milk protein content is 6.5% by weight or less, the smooth and thick texture is felt more strongly compared to when the content is more than 6.5% by weight.

The milk protein content refers to the total amount of all milk-derived proteins contained in the aforementioned yogurt ingredients (at least one selected from the group consisting of raw milk and/or cow's milk, skim milk, concentrated skim milk and skim milk powder, milk protein concentrate (MPC), and optional ingredients).

The milk protein content in the yogurt mix, which is the raw material for yogurt, can be measured by known methods, for example, by the combustion method.

The ratio of whey protein in the milk protein contained in the yogurt mix, which is the raw material for yogurt, is preferably 18 to 22% by weight, more preferably 19 to 21% by weight, from the viewpoint of better flavor and smooth texture.

The ratio of whey protein to milk protein in the yogurt mix, which is the raw material for yogurt, can be derived as a theoretical value calculated from the protein content of each raw material and the ratio of whey protein to the aforementioned proteins.

The types of skim milk, skim concentrated milk, and skim milk powder are not particularly limited, but skim milk powder is preferred from the viewpoint of ease of adjusting the components of the yogurt mix.

If the yogurt of the present disclosure does not contain at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, the rich flavor and thick texture inherent to milk may not be obtained.

The content of the skim milk, skim concentrated milk and skim milk powder in the yogurt mix, which is the raw material for yogurt, is preferably 0.5 to 7% by dry weight, more preferably 1.5 to 6% by weight, and even more preferably 3 to 5% by weight. If the content is 0.5% by weight or more, the thick texture and the original rich flavor of milk are more strongly felt compared to when the content is less than 0.5% by weight. If the content is 7% by weight or less, the unpleasant taste is less felt compared to when the content is more than 7% by weight, and the smooth and thick texture may be more strongly felt.

If the yogurt disclosed herein does not contain a protein concentrate (MPC), it may have a strong unpleasant taste.

The content of the milk protein concentrate (MPC) in the yogurt mix, which is the raw material for yogurt, is preferably 0.2 to 3% by dry weight, more preferably 0.3 to 2% by weight, and even more preferably 0.4 to 1% by weight. If the content is 0.2% by weight or more, the unpleasant taste is less noticeable than when the content is less than 0.2% by weight. If the content is 3% by weight or less, the original rich flavor of milk and the smooth and thick texture are more noticeable than when the content is more than 3% by weight.

In the yogurt of the present disclosure, from the viewpoint of the inherent rich flavor of milk and the smooth, thick texture, the milk fat content in the yogurt mix before fermentation, which is the raw material for the yogurt, is preferably 3 to 5% by weight, more preferably 3 to 4.5% by weight, and even more preferably 3 to 4% by weight.

The milk fat content refers to the total amount of milk fat contained in the yogurt mix, which is the raw material for yogurt, and refers to the total amount of all milk fat contained in the raw materials for yogurt mentioned above (at least one selected from the group consisting of raw milk and/or cow's milk, skim milk, concentrated skim milk and skim milk powder, milk protein concentrate (MPC), and optional ingredients).

The milk fat content in the yogurt mix, which is the raw material for yogurt, can be measured by known methods, for example, the Roese-Gottlieb method.

In the yogurt of the present disclosure, from the viewpoint of a smooth and thick texture, the median diameter of the curd after grinding is preferably 5 to 70 μm, more preferably 10 to 60 μm, and even more preferably 10 to 50 μm.

The median diameter of yogurt curd can be measured using a laser diffraction/scattering particle size distribution analyzer LA-960V2 (manufactured by Horiba, Ltd.) with water as the dispersion medium.

In order to obtain a smooth and thick texture, the yogurt of the present disclosure has a viscosity of preferably 20 to 60 Pa·s, more preferably 23 to 60 Pa·s, and even more preferably 25 to 55 Pa·s, when measured at 10°C using a BH type viscometer with a No. 4 rotor at a rotation speed of 2 rpm.

The yogurt of the present disclosure may contain optional ingredients other than raw milk, cow's milk, skim milk, concentrated skim milk, skim milk powder, and milk protein concentrate (MPC) in the yogurt mix before fermentation, which is the raw material of the yogurt, as long as the optional ingredients do not inhibit the effects of the yogurt mix. Examples of the optional ingredients include milk other than raw milk and cow's milk, dairy products, whey protein concentrate, casein protein, sugars, stabilizers, oils and fats, emulsifiers, flavorings, colorings, flavorings, antioxidants, etc.

Examples of milk other than raw milk and cow's milk include raw goat's milk, pasteurized goat's milk, raw sheep's milk, raw buffalo milk, composition-adjusted milk, and processed milk. The content of milk other than raw milk and cow's milk in the yogurt mix, which is the raw material for yogurt, is preferably 20% by weight or less, more preferably 10% by weight or less, and even more preferably 5% by weight or less.

Examples of the dairy products include whey, desalted whey, whey powder (including desalted whey powder), whey minerals, whole milk powder, whole fat concentrated milk, sweetened condensed milk, sweetened condensed skim milk, unsweetened condensed milk, unsweetened condensed skim milk, cream, fermented cream, butter, fermented butter, buttermilk, buttermilk powder, butter oil, etc. The content of the dairy products in the yogurt mix, which is the raw material for yogurt, is preferably 5% by dry weight or less, more preferably 3% by weight or less, and even more preferably 1% by weight or less.

Examples of the whey protein concentrate include whey protein concentrate (WPC) and whey protein isolate (WPI). The content of the whey protein concentrate in the yogurt mix, which is a raw material for yogurt, is preferably 0.15% by dry weight or less, more preferably 0.1% by dry weight or less, and even more preferably zero.

Examples of the casein protein include calcium caseinate, sodium caseinate, potassium caseinate, magnesium caseinate, acid casein, rennet casein, and casein peptide. The content of the casein protein in the yogurt mix, which is the raw material for yogurt, is preferably 1% by dry weight or less, more preferably 0.5% by dry weight or less, and even more preferably zero.

The dry weight of each component can be measured using the normal pressure heating and drying method.

Examples of the sugars include white sugar, granulated sugar, powdered sugar, glucose, fructose, sucrose, maltose, enzyme-saccharified starch syrup, reduced starch syrup, isomerized liquid sugar, sucrose-bound starch syrup, reduced sugar, reduced palatinose, sorbitol, lactose, reduced lactose, L-arabinose, trehalose, xylose, xylitol, maltitol, erythritol, mannitol, fructooligosaccharides, soybean oligosaccharides, galactooligosaccharides, lactofructose oligosaccharides, xylooligosaccharides, raffinose, lactulose, palatinose oligosaccharides, and other sugars and sugar alcohols, as well as natural sweeteners such as honey and maple sugar. The content of the sugars in the yogurt mix, which is the raw material for yogurt, is preferably 10% by weight or less, more preferably 5% by weight or less, and even more preferably 3% by weight or less.

Examples of the stabilizer include gum arabic, carrageenan, alginic acids (alginic acid, alginates), low methoxyl pectin (LM pectin), high methoxyl pectin (HM pectin), guar gum, tara gum, locust bean gum, tamarind seed gum, psyllium seed gum, water-soluble soybean polysaccharides, thickening polysaccharides such as glucomannan, gellan gum, xanthan gum, pullulan, curdlan, cellulose, carboxymethylcellulose salts, methylcellulose, chitin, chitosan, and gelatin; raw starches such as tapioca starch, potato starch, corn starch, waxy corn starch, wheat starch, and rice starch; and processed starches and dextrins obtained by subjecting the raw starches to treatments such as gelatinization, etherification, esterification, acetylation, crosslinking, and oxidation. The content of the stabilizer in the yogurt mix, which is the raw material for yogurt, is preferably 2% by weight or less, more preferably 1% by weight or less, even more preferably 0.5% by weight or less, and it is particularly preferable that it is not contained.

Examples of the fats and oils include various animal and vegetable fats and oils such as soybean oil, cottonseed oil, corn oil, safflower oil, olive oil, palm oil, rapeseed oil, rice bran oil, coconut oil, palm kernel oil, milk fat, lard, and fish oil, as well as processed fats and oils such as hardened oils, fractionated oils, and interesterified oils. The content of the fats and oils in the yogurt mix, which is the raw material for yogurt, is preferably 3% by weight or less, more preferably 2% by weight or less, and even more preferably 1% by weight or less.

Examples of the emulsifier include monoglycerides, monoglyceride derivatives bound to organic acids, sucrose fatty acid esters, polyglycerol fatty acid esters, propylene glycol fatty acid esters, polyglycerol condensed ricinoleic acid esters, calcium stearoyl lactylate, sodium stearoyl lactylate, etc. The content of the emulsifier in the yogurt mix, which is the raw material for yogurt, is preferably 1% by weight or less, more preferably 0.5% by weight or less, even more preferably 0.2% by weight or less, and it is particularly preferable that no emulsifier is contained.

Examples of the flavoring agent include yogurt flavor, fruit flavor, plant flavor, and mixtures thereof. Examples of the fruit flavor include citrus fruits such as lemon, orange, mandarin orange, grapefruit, shikuwasa, yuzu, and lime, strawberry, peach, grape, apple, pineapple, mango, melon, and banana. The content of the flavoring agent in the yogurt mix, which is the raw material for yogurt, is preferably 0.5% by weight or less, more preferably 0.3% by weight or less, and even more preferably 0.2% by weight or less.

Examples of the coloring agent include Monascus colorant, gardenia, lac, cochineal, carotene, etc. The content of the coloring agent in the yogurt mix, which is the raw material for yogurt, is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less.

Examples of the flavoring materials include cut, pureed, or grated pulp, leaf pulp, seeds, or skin of strawberry, peach, mango, papaya, watermelon, melon, apple, persimmon, pear (including pear), banana, loquat, pomegranate, lychee, plum, apricot, pineapple, grape, kiwi, plum, Japanese plum, cherry, passion fruit, blackcurrant, red currant, berries such as cranberry, blackberry, blueberry, and raspberry, citrus fruits such as orange and grapefruit, and aloe, as well as cut products such as jelly, agar gel, nata de coco, and almond tofu. The content of the flavoring material in the yogurt mix, which is the raw material for yogurt, is preferably 20% by weight or less, and more preferably 10% by weight or less.

Examples of the antioxidant include vitamin A, carotenoids, vitamin C, vitamin E, selenium, flavonoids, polyphenols, lycopene, lutein, lignans, etc. The content of the antioxidant in the yogurt mix, which is the raw material for yogurt, is preferably 0.2% by weight or less, more preferably 0.1% by weight or less, and even more preferably 0.05% by weight or less.

The yogurt disclosed herein is a pre-fermented yogurt. There are no particular limitations on the method for producing pre-fermented yogurt, but one embodiment of the production method is exemplified below.

The pre-fermented yogurt disclosed herein can be produced, for example, by the following production method. The production method includes a step of heat-treating a yogurt mix containing 60 to 97% by weight of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC), a step of fermenting the heat-treated yogurt mix to which a lactic acid bacteria starter has been added until the pH reaches 4.1 to 4.85, and a step of crushing the curds of the fermented yogurt mix to a median diameter of 5 to 70 μm.

(Heat treatment process)
The present invention relates to a process for heat-treating a yogurt mix containing 60 to 97% by weight of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, concentrated skim milk, and skim milk powder, and a milk protein concentrate (MPC). The heat-treating process produces yogurt with a rich milk flavor and a smooth, thick texture.

The heat treatment is carried out to emulsify and/or dissolve, and sterilize, a yogurt mix containing raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC). For example, the heat treatment may be carried out by holding the yogurt mix at a temperature of 80 to 98°C, preferably 85 to 95°C, for 1 to 50 minutes, preferably 5 to 20 minutes. In addition, the heat treatment method may be, for example, by raising the temperature of the yogurt mix using a device used for heat sterilization, and after reaching the temperature, placing the yogurt mix in a device capable of heating and maintaining the temperature, and maintaining the temperature for a predetermined period of time. In this way, the yogurt mix is sterilized. The device used for the heat sterilization is not particularly limited as long as it is a heating device for performing heat sterilization of milk, and may be appropriately selected, but in consideration of productivity, a flow path type sterilization device is preferable. Examples of such sterilization devices include, but are not limited to, a plate type sterilization device, a tube type sterilization device, a spin injection type sterilization device, a Joule type sterilization device, and the like. In addition, examples of devices capable of heating and maintaining the temperature include, but are not limited to, a container with a jacket that can keep the temperature warm, a tank, and the like.

In addition, before the step of heat-treating the yogurt mix, it is preferable to mix and dissolve the above-mentioned yogurt ingredients (at least one selected from the group consisting of raw milk and/or cow's milk, skim milk, concentrated skim milk, and skim milk powder, milk protein concentrate (MPC), and optional ingredients) in order to prepare the yogurt mix.

In addition, prior to the heat treatment step, a known homogenization process may be carried out in order to make the fat globules contained in the milk in the raw material yogurt mix uniform in diameter and stabilize the quality. In this case, a device such as a homogenizer, microfluidizer, or colloid mill can be used. Such homogenization can also be carried out after the heat treatment step and prior to the addition of the lactic acid bacteria starter.

(Fermentation process)
A lactic acid bacteria starter is added to the heat-treated yogurt mix, and fermentation is carried out until the pH reaches 4.1 to 4.85, to obtain a fermented yogurt mix. The pH is preferably 4.2 to 4.8, and more preferably 4.2 to 4.7.

The temperature of the yogurt mix during fermentation is preferably 36 to 42°C, more preferably 38 to 42°C. The temperature of the yogurt mix after the heat treatment is preferably adjusted to 36 to 42°C, more preferably 38 to 42°C, before the lactic acid bacteria starter is added.

The fermentation process can also be carried out in two stages. For example, the yogurt mix can be fermented to a certain extent (primary fermentation) at a temperature of 36 to 42°C, and then cooled to 15 to 25°C and subjected to secondary fermentation under the same temperature conditions (15 to 25°C). By carrying out secondary fermentation, larger curds are regenerated, improving the rich flavor and viscosity of the yogurt. The temperature condition during secondary fermentation is preferably 15 to 19°C.

When the secondary fermentation is carried out, from the viewpoint of further improving the rich flavor and viscosity of the yogurt, it is preferable to carry out the secondary fermentation until the pH of the yogurt mix reaches 4.2 to 4.75, more preferably 4.2 to 4.6, and even more preferably 4.3 to 4.6.

The lactic acid bacteria starter is not particularly limited, and any known lactic acid bacteria starter can be used, such as Lactococcus, Streptococcus, Pediococcus, and Leuconostoc, Lactobacillus belonging to Lactobacillus, and Bifidobacterium. Specific examples include Streptococcus thermophilus, Lactobacillus delbrueckii subsp. Bulgaricus, Lactobacillus acidophilus, and Bifidobacterium lactis.

The amount of the lactic acid bacteria starter to be added is not particularly limited, and may be an amount normally used in making yogurt. For example, 0.00001 to 5 parts by weight may be added per 100 parts by weight of yogurt mix, with 0.00001 to 0.05 parts by weight being the standard for freeze-dried types and 0.01 to 5 parts by weight being the standard for fermented liquid types.

(Crushing step)
The curd of the fermented yogurt mix obtained in the fermentation step is pulverized to a median diameter of 5 to 70 μm.

The curds can be crushed by known methods, such as using a mesh filter or stirring in a tank. From the standpoint of simplicity and uniformity of the curd size, the method using a mesh filter is preferred.

The mesh size of the mesh filter used is, for example, preferably 10 to 100 mesh, more preferably 20 to 90 mesh, and even more preferably 30 to 70 mesh.

Pressure conditions when passing through a mesh filter are, for example, preferably 0.01 to 0.45 MPa, more preferably 0.05 to 0.45 MPa, and even more preferably 0.1 to 0.4 MPa.

(Filling process and cooling process)
The yogurt obtained by the above-mentioned manufacturing method can be filled into any container. After filling into any container, it is preferable to cool it. From the viewpoint of storage stability, the cooling temperature is preferably 1 to 10°C, more preferably 3 to 10°C.

Each of the following items lists preferred aspects of the present disclosure, but the present invention is not limited to the following items.
[Item 1]
A pre-fermented yogurt, the raw material of which contains 60 to 97% by weight of raw milk and/or cow's milk, and which contains at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC).
[Item 2]
2. The pre-fermented yogurt according to Item 1, wherein the raw material has a milk solid content of 14.5 to 18% by weight and a milk protein content of 4.5 to 6.5% by weight.
[Item 3]
3. The pre-fermented yogurt according to Item 1 or 2, wherein the ratio of whey protein to milk protein in the raw material is 18 to 22% by weight.
[Item 4]
4. The pre-fermented yogurt according to any one of items 1 to 3, wherein the content of at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder in the raw material is 0.5 to 7% by dry weight, and the content of milk protein concentrate (MPC) is 0.2 to 3% by dry weight.
[Item 5]
5. The pre-fermented yogurt according to any one of items 1 to 4, wherein the median diameter of the curd is 5 to 70 μm.
[Item 6]
A method for producing pre-fermented yogurt, comprising the steps of:
A step of heat-treating a yogurt mix containing 60 to 97% by weight of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC);
fermenting the heat-treated yogurt mix to which the lactic acid bacteria starter has been added until the pH reaches 4.1 to 4.85;
The method for producing a pre-fermented yogurt includes a step of crushing the curds of the fermented yogurt mix to a median diameter of 5 to 70 μm.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples. Note that in the examples, "parts" and "%" are by weight.

The raw materials used in the examples and comparative examples are as follows.
1) Raw milk: (milk fat content: 3.7%, milk protein content: 3.2%, protein reduction value: 4.4)
2) Skim milk powder: Kaneka skim milk powder (milk fat content: 1.0%, milk protein content: 34.0%, water content: 3.8%) manufactured by Kaneka Corporation
3) MPC: Glanbia Nutritionals "MPC80 SOLMIKO" (milk fat content: 1.5%, milk protein content: 80.5%, moisture content: 4.2%)
4) Fresh cream: Meiji Tokachi Fresh Cream 47 (milk fat content: 47.0%, milk protein content: 1.0%) manufactured by Meiji Co., Ltd.
5) WPC: "WPC80" manufactured by Warrnambool Cheese and Butter (milk fat content: 4.8%, milk protein content: 76.5%)
6) Whey Mineral: Meito Kyodo Dairy Co., Ltd. "Whey Mineral NWP-20N" (milk fat content: 1.6%, milk protein content: 16.0%)
7) Lactose: "Lactose HILMAR FINE GRAIN" manufactured by HILMAR CHEESE CO.
8) Lactic acid bacteria starter: Danisco "YO-MIX207"

[Measurement method]
<Measurement of protein reducing value>
The protein reducing value was measured according to the method described in "Examination Methods for Dairy Products, Commentary, edited by the Pharmaceutical Society of Japan" (Kanbara Publishing Co., Ltd., p. 131, published March 20, 1984).

<Composition analysis of yogurt mix>
The contents of milk solids, milk protein, and milk fat were analyzed according to the general nutritional analysis method for dairy products as follows.
Milk solids: Measured based on the "Method for determining milk fat content in cow's milk, special cow's milk, pasteurized goat's milk, low-fat milk, non-fat milk and processed milk" (Roese-Gottlieb method) and "Method for determining non-fat milk solids in milk and dairy products" which are stipulated in the Ministerial Ordinance on the Compositional Standards of Milk and Dairy Products.
Milk protein: Combustion method Milk fat: Roese-Gottlieb method

The dry weights of skim milk, skim concentrated milk, skim milk powder, and MPC were measured using the normal pressure heat drying method.

The ratio of whey protein in milk protein in the yogurt mix, which is a raw material for yogurt, was calculated as a theoretical value calculated from the protein content in each raw material and the ratio of whey protein in the protein in each raw material. Specifically, the ratio of whey protein in the total protein in raw milk, fresh cream, skim milk powder, and MPC was set to 20% by weight, and the ratio of whey protein in the total protein in WPC was set to 100% by weight, and the ratio of whey protein in the milk protein in the yogurt mix, which is a raw material for yogurt, was calculated.

<Measurement of Viscosity>
The viscosity of the yogurt was measured at 10° C. using a BH type viscometer (manufactured by Tokyo Keiki Co., Ltd.) with a No. 4 rotor at a rotation speed of 2 rpm.

<Measurement of the median diameter of the curd>
The median diameter of the yogurt curd was measured with a laser diffraction/scattering type particle size distribution measuring device LA-960V2 (manufactured by Horiba, Ltd.) using water as a dispersion medium.

<Sensory evaluation>
Ten experienced panelists tasted each of the yogurts obtained in the Examples and Comparative Examples at a temperature of 10° C. and performed a sensory evaluation of each in terms of the absence of unpleasant flavors, the rich flavor inherent to milk, the smooth texture, and the viscosity, and the average scores are shown in the table as the sensory evaluation scores. The evaluation criteria were as follows:

(No off-flavors)
The absence of unpleasant flavors was evaluated from the perspective of whether there was any aftertaste, strange taste, bitterness, or saltiness that was different from the original taste of raw milk or cow's milk.
5 points: Better than the yogurt of Example 1, no unpleasant taste at all 4 points: Same as the yogurt of Example 1, no unpleasant taste 3 points: A little worse than the yogurt of Example 1, slight unpleasant taste but not at a level that would cause quality problems 2 points: Worse than the yogurt of Example 1, unpleasant taste is noticeable 1 point: Much worse than the yogurt of Example 1, unpleasant taste is clearly noticeable

(Rich, natural milk flavor)
The rich flavor inherent to milk was evaluated from the perspective of whether the richness and full-bodiedness of the milk flavor could be felt.
5 points: Better than the yogurt of Example 1, with a strong, rich milk flavor. 4 points: Same as the yogurt of Example 1, with a rich, milk flavor. 3 points: A little worse than the yogurt of Example 1, with the rich, milk flavor being a little difficult to detect. 2 points: Worse than the yogurt of Example 1, with the rich, milk flavor being difficult to detect. 1 point: Much worse than the yogurt of Example 1, with the rich, milk flavor not being detectable.

(Smooth texture)
The smooth texture was evaluated from the viewpoint of whether it felt smooth on the tongue without any roughness and whether it melted easily in the mouth.
5 points: Better than the yogurt of Example 1, with a very smooth texture 4 points: Equivalent to the yogurt of Example 1, with a smooth texture 3 points: Slightly worse than the yogurt of Example 1, with a slightly less smooth texture 2 points: Worse than the yogurt of Example 1, with a less smooth texture 1 point: Much worse than the yogurt of Example 1, with no smooth texture

(Thickness)
The thickness was evaluated from the viewpoint of whether the degree of fluidity when the yogurt was scooped with a spoon was appropriate.
5 points: Much better than the yogurt of Example 1, with a strong sense of viscosity. 4 points: Same as the yogurt of Example 1, with a sense of viscosity. 3 points: A little worse than the yogurt of Example 1, with a little difficulty in feeling the viscosity. 2 points: Worse than the yogurt of Example 1, with low or high fluidity making it difficult to feel the viscosity. 1 point: Much worse than the yogurt of Example 1, with a fluidity that is too low or too high, making it impossible to feel the viscosity at all.

(comprehensive evaluation)
An overall evaluation was made based on the evaluation results of the absence of unpleasant flavors, the rich flavor of milk itself, the smooth texture, and the viscosity. The evaluation criteria were as follows:
A: Freedom from unpleasant flavors, rich milk flavor, smooth texture, and viscosity all meet the criteria of 4.0 to 5.0 points.
B: Freedom from unpleasant flavors, rich milk flavor, smooth texture, and viscosity are all 3.5 to 5.0 points, with at least one being 3.5 to less than 4.0.
C: Freedom from unpleasant flavors, rich milk flavor, smooth texture, and viscosity are all 3.0 to 5.0 points, with at least one being 3.0 to less than 3.5.
D: Freedom from unpleasant flavors, rich milk flavor, smooth texture, and viscosity are all 2.0 to 5.0 points, with at least one being 2.0 to less than 3.0.
E: In the evaluations of the absence of unpleasant flavors, the rich flavor of milk itself, the smooth texture, and the viscosity, at least one of the following was scored less than 2.0 points.

[Yogurt production example]
Example 1
A yogurt mix was prepared by adding 3.9 parts by weight of skim milk powder and 0.5 parts by weight of MPC to 95.6 parts by weight of raw milk and dissolving them according to the formulation shown in Table 1. These were preheated to 60°C, homogenized at a pressure of 3.5/17 MPa using a high-pressure homogenizer, heated to 90°C using a plate-type sterilizer, and held at 90°C for 10 minutes in a jacketed tank for heat treatment.

The mixture was then cooled to 40°C, and 0.0014 parts by weight of lactic acid bacteria starter (Streptococcus thermophilus, Lactobacillus delbrueckii subsp. Bulgaricus, Lactobacillus acidophilus, Bifidobacterium lactis) was added, followed by fermentation at a temperature of 40°C until the pH reached 4.5. The fermented yogurt mix was passed through a 60-mesh filter at a pressure of 0.22 MPa to crush the curd, and then filled into retail containers and cooled to 8°C in a refrigerated warehouse to obtain pre-fermented yogurt.

The resulting yogurt was evaluated by a panel of 10 experienced people for its sensory quality, which was judged to be excellent in all respects: lack of unpleasant flavors, rich milk flavor, smooth texture, and thick consistency. Furthermore, the viscosity and curd median diameter were measured, and the results are shown in Table 1.

Example 2
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 60.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 7.0 parts by weight, and the MPC was changed from 0.5 parts by weight to 1.0 part by weight in accordance with the formulation in Table 1, and 3.0 parts by weight of fresh cream and 29.0 parts by weight of water were added and dissolved to prepare a yogurt mix. The viscosity and median diameter of the curd of the obtained yogurt were measured, and the results of a sensory evaluation are shown in Table 1.

Example 3
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 97.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 2.0 parts by weight, and the MPC was changed from 0.5 parts by weight to 1.0 part by weight in accordance with the formulation in Table 1. The viscosity and the median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 1.

Example 4
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 96.5 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 0.5 parts by weight, and the MPC was changed from 0.5 parts by weight to 3.0 parts by weight in accordance with the formulation in Table 1. The viscosity and the median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 1.

(Comparative Example 1)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 40.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 7.0 parts by weight, and MPC was changed from 0.5 parts by weight to 1.0 part by weight, and 4.5 parts by weight of fresh cream, 2.0 parts by weight of lactose, and 45.5 parts by weight of water were added in accordance with the formulation in Table 1. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 1.

As is clear from Table 1, all of the pre-fermented yogurts (Examples 1 to 4) in which the raw materials contained 60 to 97% raw milk by weight were evaluated as having good results in terms of the absence of unpleasant flavors, the rich flavor inherent to milk, the smooth texture, and the thickening. In particular, Example 1, in which the raw materials contained 15.5 to 16.5% milk solids by weight and 4.7 to 5.2% milk protein by weight, received an overall rating of A. On the other hand, pre-fermented yogurt (Comparative Example 1), in which the raw materials contained only 40.0% raw milk by weight, received a poor rating for the rich flavor inherent to milk, and received an overall rating of D.

(Comparative Example 2)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that skim milk powder was not added, and the raw milk: 95.6 parts by weight was changed to 93.5 parts by weight, and the MPC: 0.5 parts by weight was changed to 6.5 parts by weight, according to the formulation in Table 1. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 1.

(Comparative Example 3)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that MPC was not added, the raw milk was changed from 95.6 parts by weight to 95.0 parts by weight, and the skim milk powder was changed from 3.9 parts by weight to 5.0 parts by weight according to the formulation in Table 1. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 1.

(Comparative Example 4)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that skim milk powder and MPC were not added, raw milk: 95.6 parts by weight was changed to 98.0 parts by weight, WPC: 1.0 part by weight, and whey minerals: 1.0 part by weight were added according to the formulation in Table 1. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed. The results are shown in Table 1.

As is clear from Table 1, the pre-fermented yogurt that does not contain skim milk powder (Comparative Example 2) was poorly rated for its rich milk flavor, smooth texture, and thickening, and received an overall rating of D. The pre-fermented yogurt that does not contain MPC (Comparative Example 3) was poorly rated for its lack of unpleasant flavors, and received an overall rating of D. Furthermore, the pre-fermented yogurt that does not contain skim milk powder or MPC (Comparative Example 4) was poorly rated for its rich milk flavor and thickening, and received an overall rating of D.

Example 5
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 95.2 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 4.0 parts by weight, and the MPC was changed from 0.5 parts by weight to 0.8 parts by weight in accordance with the formulation in Table 2. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was carried out. The results are shown in Table 2 together with the results of Examples 1 and 3.

Example 6
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 87.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 7.0 parts by weight, and 5.5 parts by weight of water was added according to the formulation in Table 2. The viscosity and the median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 2.

(Example 7)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 70.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 6.0 parts by weight, MPC was changed from 0.5 parts by weight to 2.6 parts by weight, and 21.4 parts by weight of water was added in accordance with the formulation in Table 2. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 2.

(Example 8)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that the raw milk was changed from 95.6 parts by weight to 95.7 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 3.6 parts by weight, the MPC was changed from 0.5 parts by weight to 0.55 parts by weight, and 0.15 parts by weight of WPC was added in accordance with the formulation in Table 2. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 2.

As is clear from Table 2, the pre-fermented yogurts (Examples 1, 3, 5-8) in which the milk solids content in the raw materials was in the range of 14.5-18% by weight and the milk protein content was in the range of 4.5-6.5% by weight were all rated as good in terms of the absence of unpleasant flavors, the rich flavor inherent to milk, the smooth texture, and the thickening. In particular, Examples 1 and 5 in which the milk solids content in the raw materials was in the range of 15.5-16.5% by weight, the milk protein content was in the range of 4.7-5.2% by weight, and the proportion of whey protein in the milk protein was in the range of 19-21% by weight were rated as A overall. In addition, a pre-fermented yogurt (Example 8) in which the milk solids content and milk protein content in the raw materials were the same as those in Example 1 and the ratio of whey protein to the milk protein was 22% by weight had a better viscosity than a pre-fermented yogurt (Example 1) in which the ratio of whey protein to the milk protein was 20% by weight, but was inferior in the evaluations of the absence of unpleasant flavors, the original rich milk flavor, and the smooth texture.

(Comparative Example 5)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that no MPC was added, the raw milk was changed from 95.6 parts by weight to 95.0 parts by weight, the skim milk powder was changed from 3.9 parts by weight to 4.0 parts by weight, and 1.0 part by weight of WPC was added according to the formulation in Table 2. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed, and the results are shown in Table 2.

(Comparative Example 6)
A pre-fermented yogurt was obtained in the same manner as in Example 1, except that skim milk powder and MPC were not added, the raw milk content was changed from 95.6 parts by weight to 96.5 parts by weight, and 3.5 parts by weight of WPC was added according to the formulation in Table 2. The viscosity and median diameter of the curd of the obtained yogurt were measured, and a sensory evaluation was performed. The results are shown in Table 2.

As is clear from Table 2, the pre-fermented yogurt that does not contain MPC (Comparative Example 5) was poorly rated for the absence of unpleasant flavors, and received an overall rating of D. In addition, the pre-fermented yogurt that does not contain skim milk powder or MPC (Comparative Example 6) was poorly rated for the absence of unpleasant flavors and for the sense of thickness, and received an overall rating of D.

Example 9
The fermented yogurt mix obtained by fermenting in the same manner as in Example 1 under the production conditions in Table 2 was stirred in a tank having paddle-type stirring blades at a stirring speed of 0.35 revolutions/second for 90 minutes to crush the curds, and then filled into retail containers and cooled to 8° C. in a refrigerated warehouse to obtain a pre-fermented yogurt. The viscosity and median diameter of the curds of the obtained yogurt were measured, and a sensory evaluation was performed. The results are shown in Table 2.

As is clear from Table 2, the pre-fermented yogurt (Example 9), which had the same composition as Example 1 but in which the curd was pulverized by stirring and had a large median diameter, was inferior in smoothness and viscosity to Example 1 and received an overall rating of C.

Claims (6)

A pre-fermented yogurt, the raw materials of which contain 60 to 97% by weight of raw milk and/or cow's milk, and which contains at least one selected from the group consisting of skim milk, concentrated skim milk, and skim milk powder, and a milk protein concentrate (MPC). The pre-fermented yogurt according to claim 1, wherein the raw material contains 14.5 to 18% by weight of milk solids and 4.5 to 6.5% by weight of milk protein. The pre-fermented yogurt according to claim 1 or 2, wherein the ratio of whey protein to the milk protein in the raw material is 18 to 22% by weight. The pre-fermented yogurt according to claim 1 or 2, wherein the content of at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder in the raw material is 0.5 to 7% by dry weight, and the content of milk protein concentrate (MPC) is 0.2 to 3% by dry weight. The pre-fermented yogurt according to claim 1 or 2, in which the median diameter of the curd is 5 to 70 μm. A method for producing pre-fermented yogurt, comprising the steps of:
A step of heat-treating a yogurt mix containing 60 to 97% by weight of raw milk and/or cow's milk, at least one selected from the group consisting of skim milk, skim concentrated milk, and skim milk powder, and a milk protein concentrate (MPC);
fermenting the heat-treated yogurt mix to which the lactic acid bacteria starter has been added until the pH reaches 4.1 to 4.85;
The method for producing a pre-fermented yogurt includes a step of crushing the curds of the fermented yogurt mix to a median diameter of 5 to 70 μm.