WO2007060288A1

WO2007060288A1 - Method of modifying the texture of a preparation

Info

Publication number: WO2007060288A1
Application number: PCT/FI2006/050506
Authority: WO
Inventors: Kirsi Rajakari; Anna Rautio; Olli Tossavainen; Aino Sivonen
Original assignee: Valio Ltd
Priority date: 2005-11-22
Filing date: 2006-11-21
Publication date: 2007-05-31
Also published as: EP1951061A4; FI20055616A; FI121525B; EP1951061A1; FI20055616A0; JP2009516522A

Abstract

The invention relates to a method of manufacturing soured fresh dairy products by the use of a transglutaminase enzyme, an enzyme-activating compound and an acidifying agent and by the addition thereof to a protein source under such circumstances that the enzyme is active during acidifying.

Description

METHOD OF MODIFYING THE TEXTURE OF A PREPARATION

[0001] The invention relates to a method of manufacturing sour milk preparations, such as soured fresh dairy products by the use of a transglutaminase enzyme and an enzyme-activating compound. The invention further relates to a sour milk preparation manufactured by the method according to the invention. The invention further relates to a method of modifying the texture of sour milk preparations by means of a transglutaminase enzyme and an enzyme-activating compound.

BACKGROUND OF THE INVENTION

[0002] Conventionally, sour milk preparations have been manufactured by acidifying milk with an acidifying agent specific to each product at a suitable temperature. Lactobacillus bulgaricus and Streptococcus thermophHus strains are conventionally used in the preparation of yoghurt, for example. Before acidifying, all necessary raw materials (sweetener, flavouring agents and texturizers) are added to the milk, and the milk is then typically pasteurized and homogenized. The milk is acidified to a pH specific to each product. Then, the texture is broken for all products other than products of the viiii (ropy sour milk, a typical Finnish milk product) type and set-type yoghurts, necessary flavouring agents (e.g. jam addition) are added, and the product is packaged. In the manufacture of products of the viili type, viili mould is used in addition to lactic acid bacterium starters. In contrast to other sour milk preparations, for products of the viili type and set-type yoghurts, acidifying occurs in the package.

[0003] Conventionally, the dry substance content of milk is increased or decreased for adjusting the texture of sour milk preparations. The dry substance content can be increased by evaporating the milk or by the use of powders. The protein content of the raw material milk affects the texture of the end product in a manner allowing the texture of the sour milk preparation, such as a soured fresh dairy product to be modified thicker or runnier by increasing or decreasing the protein content. The protein content of the raw material milk can be increased by evaporation or by the use of protein powder addition. The protein powder may originate from milk, such as milk powder, whey protein powder or casein protein powder, but proteins not originating from milk are also usable. For some products, for example fermented milk, thinning-down of the texture may be feasible. This may be influenced by the addition of milk permeate, cheese whey, sour whey (quark whey, cottage cheese whey) or lactose fraction to the raw material milk. Liquids not originating from milk, such as water, may also be used to liquidity the texture.

[0004] The use of a texture-modifying transglutaminase enzyme in the manufacture of milk preparations, particularly sour milk preparations, is known. In sour milk preparations, such as soured fresh dairy products (yoghurt, set-type yoghurt, viili, fermented milk), the use of a transglutaminase enzyme serves to harden the texture, modify the texture to be finer, and to reduce syneresis. The enzyme also serves to modify the texture thicker.

[0005] The transglutaminase enzyme catalyzes the generation of covalent linkages between the glutamine and lysine amino acid residues present in the protein molecules. When linkages are formed, ammonia is released. The enzyme was first used in Japan in the manufacture of surimi (seaf- ish paste) products (Kuraishi, et. a/., Food Rev. Int. 17(2), 2001 , pp. 221 to 246).

[0006] Patent publication EP 610 649 (Ajinomoto) describes a method of pre-processing yoghurt milk with transglutaminase enzyme and inactivating the enzyme before acidifying in connection with the pasteurization of yoghurt milk. Patent publication EP 689 383 (Novo Nordisk A/S) discloses a method of processing milk with transglutaminase enzyme, followed by acidifying the milk to the desired pH and heat-treating the gel obtained. The thus- formed gel may be used in the manufacture of yoghurt or cheese. Patent publication EP 1 206 912 (Friesland Brands B.V.) describes a method of adding transglutaminase enzyme after the heat-treatment of milk, during the acidifying step, and adding enzyme also after the acidifying. The method is characterized by adding enzyme always also after the acidifying. Patent publication JP 2001252011 (Koiwai Nyugo KK) discloses a method for the manufacture of yoghurt, wherein i.a. transglutaminase enzyme is added in an acidifying step when pH has dropped close to the value 5, and at this pH, acidifying is stopped by transferring the yoghurts into cold storage.

[0007] A common feature in the above-described methods is the use of transglutaminase enzyme only in the cross-iinking. Patent publication EP 1 197 152 (Ajinomoto) discloses a cross-linking method, wherein milk is pre-processed by means of a processing aid affecting the operation of transglutaminase and the enzyme, by means of glutathione, for example. After the processing, transglutaminase is inactivated by heat-treatment, and the milk is used in the manufacture of various milk products. This method enables the cross-linking to be accomplished more effectively than processing with transglutaminase alone. The method is particularly a pre-processing method of raw material milk prior to conventional manufacture of milk products.

[0008] In the above-described methods, the enzyme, any processing aid affecting the activity of the enzyme, and the acidifying agent used in any particular case, are added to the reaction mixture in different processing steps, and the enzyme, any processing aid affecting the activity of the enzyme or the acidifying agent are not allowed to react simultaneously in the mixture.

[0009] It has now been surprisingly discovered that the addition of transglutaminase enzyme, an enzyme-activating compound and an acidifying agent to a protein source under such circumstances that the enzyme is active upon the addition of the acidifying agent and/or during the acidifying, results in a simpler method that requires fewer processing steps, which enables a reduction in the protein content of sour milk preparations, especially soured fresh dairy products without any damage to or adverse effect on the texture of the preparation.

BRIEF DESCRIPTION OF THE INVENTION

[0010] The invention relates to a method of manufacturing sour milk preparations, such as soured fresh dairy products with the use of a transglutaminase enzyme, an enzyme-activating compound, and an acidifying agent by the addition thereof to a protein source under such circumstances that the enzyme is active upon the addition of the acidifying agent and/or during the acidifying. The method enables the modification of the texture of soured fresh dairy products more advantageously and easily than known methods. In addition, the method enables a significant reduction in the protein content of soured fresh dairy products without any damage to or adverse effect on the texture of the preparation.

[0011] The method also relates to a soured fresh dairy product manufactured by the method.

DETAILED DESCRIPTION OF THE INVENTION

[0012] It has now been surprisingly discovered that the addition of transglutaminase enzyme, an enzyme-activating compound, and an acidifying agent to a protein source under such circumstances that the enzyme is active upon the addition of the acidifying agent and/or during the acidifying, enables the modification of the texture of a sour milk preparation, such as a soured fresh dairy product significantly more efficiently than by the use of the above described pre-processing method of raw material milk. The method according to the invention, wherein the cross-linking occurs during the acidifying, is about 20% more effective compared with a method wherein transglutaminase enzyme alone is used during acidifying. The method according to the invention enables the manufacture of sour milk preparations, especially soured or fermented fresh dairy products, with a significantly lower protein content while the texture remains the same as in sour milk preparations manufactured in the conventional manner. This enables the manufacture of sour milk preparations, especially soured or fermented fresh dairy products, at a lower raw material cost level than in the manufacture of sour milk preparations at a conventional protein level. Fermented or more generally soured fresh dairy products include yoghurts, viili, fermented milks, quarks (a kind of low-fat curd cheese), fresh cheeses, cream cheeses and soured cream products, such as creme fraϊche and smetana, for example.

[0013] Transglutaminase enzyme (EC 2.3.2.13) catalyzes the generation of covalent linkages between the glutamine and lysine amino acid residues present in the protein molecules. Microbial transglutaminase preparations acceptable for use in foodstuffs are commercially available. The manufacturers recommend an enzyme dosage of 1 to 3 U/g of protein, depending on the use.

[0014] As the enzyme-activating compound, any compound possessing the necessary property may be used. For example, compounds whose chemical activity is based on either reduction or oxidation are usable. As examples of reducing compounds may be mentioned glutathione, cysteine, y- glutamyl cysteine, thiosulphuric acid, thioglycolic acid, sulphurous acid, ascorbic acid, erythorbic acid, dithiotreitol and salts thereof, accepted for use in foodstuffs, NaBH_-I, tocopherol, fatty acid ester of glycerine or lecithin. As an example of oxidizers, formic acid may be mentioned.

[0015] The enzyme-activating compound is preferably glutathione. Glutathione reduces whey proteins and its effect, when used together with transglutaminase enzyme, is thought to be based on this property. Glutathione may be used as such, as a commercially available purified compound, for example. Alternatively, a glutathione-containing mixture may be used. As an example of a glutathione-containing mixture accepted for use in the foodstuffs industry, yeast extract may be mentioned.

[0016] The term 'acidifying agent' refers to a microbiological starter or culture, a chemical acidifying agent or mixtures thereof.

[0017] Acidifying may be performed by fermenting with at least one product specific culture and/or by using chemical acidifying agents, such as organic or inorganic acids, for example.

[0018] In accordance with the method of the invention, transglutaminase enzyme, the enzyme-activating compound, and the acidifying agent are added to the protein source under such circumstances that the enzyme is active upon the addition of the acidifying agent and/or during the acidifying. This allows the enzyme and the enzyme-activating compound to be added to the protein source before the addition of the acidifying agent, in connection with the addition of the acidifying agent or after the addition of the acidifying agent. It is essential to the method according to the invention that the circumstances after the addition of the enzyme and the enzyme-activating compound, before the addition of the acidifying agent, or in a reverse order, after the addition of the acidifying agent, before the addition of the enzyme and the enzyme- activating compound, do not change and/or are not changed in a manner causing the enzyme to become inactive. Thus, in accordance with the invention, provided the enzyme is active upon the addition of the acidifying agent and/or during the acidifying, the enzyme and the enzyme-activating compound may be added to the protein source several hours, e.g. 2 to 10 hours, prior to the addition of the acidifying agent. The circumstances where the additions are performed in the method according to the invention depend on the properties of the enzyme used in the method. The properties of the enzymes, such as activity and substrate-specificity, depend typically on the temperature and the pH, for example. The transglutaminase enzymes commercially available at present are active in a temperature range of from 0 to 8O⁰C, the enzyme becoming inactive at temperatures of over 8O⁰C, and reaching its maximum activity at a temperature of about 50⁰C. In milk-based applications, the enzyme can be used preferably at a temperature range of from 3 to 6O⁰C. When transglutaminase enzyme is used in connection with an oxidation reaction, the temperature range is preferably from 20 to 5O⁰C. The transglutaminase enzymes commercially available at present are active in a pH range of from 3 to 10, reaching their maximum activity at a pH range of from 5 to 8. In milk-based applications, pH is preferably between 3.5 and 7.5 or it is adjusted to said pH value range.

[0019] In the method according to the invention, raw material milk as such or pre-processed in the desired manner usually constitutes the protein source. Decreasing the protein content of raw material milk may be mentioned as an example of pre-processing. The protein level may be lowered also simultaneously with the addition of the acidifying agent. Milk permeate, whey, lactose fraction, concentrates thereof or a mixture constituted by milk permeate, whey, lactose fraction and/or concentrates thereof, for example, may be used for decreasing the protein level. In addition, water, corn steep liquid, juice or any other liquid suitable for foodstuffs use may be used for decreasing the protein level. The above-mentioned liquids or mixtures thereof, suitable for decreasing the protein level, may be added up to 20 volume percent to the protein source used in the method.

[0020] in this context, raw material milk refers to milk obtained from an animal, e.g. a cow or a goat, as such or processed in various manners. Milk may be processed for instance by removing fat or lactose from it, resulting in fat-free, low-fat, lactose-free or low-lactose milk. In this context, raw material milk also refers to pre-processed or unprocessed milks used in the manufacture of yoghurt, viili and fermented milk, for example, which persons skilled in the art refer to as raw material milk for yoghurt, viili and fermented milk.

[0021] The milk may be fractionated for instance by means of chromatographic separation and/or micro, nano or ultra-filtering into fractions containing different amounts of different components, and the fractions may, in turn, be used for adjusting the protein content of the milk as such or as different mixtures thereof.

[0022] A milk permeate refers to a permeate that is obtained in the ultra-filtering of milk and contains mainly lactose, ash and protein. The protein content of the milk permeate depends on the filtering conditions, but is most generally between about 0.2 to 0.4 percent by weight, typically about 0.3 percent by weight of protein.

[0023] Whey refers to the liquid, non-precipitated part of milk that is separated from the curd in making cheese or curd cheese. The protein content of whey is usually between about 0.5 and 0.7 percent by weight, typically about 0.6 percent by weight.

[0024] A lactose fraction refers to a fraction that is obtained as the result of chromatographic separation and that contains mainly lactose, but also proteins, for example. The protein content of the lactose fraction depends on the separation conditions, but is most generally between about 0.2 and 0.4 percent by weight, typically about 0.3 percent by weight of protein.

[0025] Furthermore, not only animal milk, but also liquids originating from plants, such as oat, soy, rice or coconut milk that are commercially available, may be used as the protein source. Oat, soy and rice milk may be industrially manufactured in a process wherein grains or beans are crushed and the desired nutrients extracted into a suitable liquid, such as water, which may also contain oil, such as rapeseed oil, for example.

[0026] Fermented or more generally soured fresh dairy products refer to soured fresh products based on milk(s) originating from animal(s) and/or plant(s).

[0027] With the exception of the addition of transglutaminase enzyme and an enzyme-activating compound and the optional adjustment of the protein content of the protein source, acidifying takes place in the same way as for corresponding soured fresh dairy products manufactured conventionally by the use of an acidifying agent suitable for each particular case and/or each particular product, and suitable reaction conditions, however, in such a manner that the enzyme remains active.

[0028] The method of the invention is suitable for the manufacture of flavoured and non-flavoured fatty and fat-free, and homogenized and non- homogenized fresh products. It is further suitable for the manufacture of lactose-free and low-lactose (such as HYLA®) products.

[0029] fn an embodiment of the invention, the method comprises the following steps: addition of transglutaminase enzyme, an enzyme-activating compound and an acidifying agent to a protein source, acidifying, recovering the product obtained.

[0030] In another embodiment of the invention, the method further comprises a step of decreasing the protein content of the protein source by the addition of liquid suitable for the purpose to the protein source. In this case, the method comprises the following steps: addition of a liquid suitable for decreasing the protein content, such as milk permeate, whey, lactose fraction, a concentrate thereof or a mixture constituted by mifk permeate, whey, lactose fraction and/or concentrates thereof, to a protein source, addition of transglutaminase enzyme, an enzyme-activating com- pound and an acidifying agent to the protein source, acidifying, recovering the product obtained.

[0031] In addition to these steps, the method of the invention preferably comprises any other necessary manufacturing steps for accomplishing the end product, such as the addition of jam and/or sugar and/or heat- treatment (post-pasteurization).

[0032] An advantage of the method according to the invention is that it enables the utilization of raw material mifk having a lower protein content than in the use of the above-described, known methods. The protein content of the raw material milk used in the method of the invention may be as low as about 0.5 percent by weight, whereas the lower limit of the protein content is within the range 2 to 3 weight percent when known manufacturing methods are used, depending on the sour milk product. When known manufacturing methods are used, the protein content of yoghurt is typically within the range 3 to 5 percent by weight, of viili within the range 3 to 5 percent by weight, of fermented milk within the range 3 to 5 percent by weight, and of drinkable yoghurt within the range 2 to 4 percent by weight. There is no actual upper limit for the protein content, but in practice, a 10% protein content in raw material milk is seldom exceeded in industrial manufacture of yoghurt, viili and/or fermented milk.

[0033] An advantage of the method of the invention is that the amount of enzyme required in the method is smaller than the amount required when known methods are used. In the method of the invention, enzyme may be used in an amount of 0.1 to 300 ppm, preferably 1 to 200 ppm. A smaller amount of enzyme required results in clear cost saving in the production. In addition, another advantage of the method according to the invention is a simplified manufacturing process, since extra method steps binding energy and time can be omitted.

[0034] The invention also relates to a method of modifying the texture of sour milk preparations, especially soured or fermented fresh dairy products, by means of transglutaminase enzyme and an enzyme-activating compound. This method is characterized by adding the transglutaminase enzyme, the enzyme-activating compound and the acidifying agent to a protein source under conditions when the enzyme is active during the acidifying.

[0035] The following examples illustrate the present invention. They are in no way intended to restrict the claims.

Example 1. Preparation of yoghurt

[0036] In the example, it was studied how pre-processing of milk with transglutaminase enzyme and glutathione in accordance with prior art and processing with transglutaminase enzyme and glutathione together with an acidifying agent in accordance with the present invention affected the manufacturing process and the properties of the end product.

[0037] Reference yoghurt was manufactured from raw material milk having a protein content of 4.2% and fat content of 2.5%. 0.252 g of Activa® YG powder (Ajinomoto, contains i.a. transglutaminase and yeast extract)/1 ,000 g milk were added to the milk. The enzyme was allowed to act at a temperature of 6⁰C for 16 hours. The milk was then pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. Yoghurt starter culture was added and maturing occurred at a temperature of 42⁰C until pH had fallen to 4.5.

[0038] The test yoghurt according to the invention was manufactured from raw material milk having a protein content of 3.8% and fat content of 2.5%. The milk was pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. 0.171g/1 ,000 g milk of Activa® YG powder were added to the milk together with a yoghurt starter and was brought to maturity at a temperature of 42⁰C until pH had fallen to 4.5. In the manufacture of the test yoghurt, smaller amounts of transglutaminase enzyme and yeast extract were used than in the manufacture of the reference yoghurt. In addition, the manufacture of the test yoghurt according to the invention differed from the manufacture of the reference yoghurt in that the Activa® YG powder was added together with the culture.

[0039] The organoleptic quality and the viscosity of the yoghurts were observed during 20 days. The method according to the invention enabled the use of milk having a protein level lowered from 4.2% to 3.8% as raw material milk without any weakening of the quality of the yoghurt. In contrast, the texture of the test yoghurt was slightly thicker than the reference yoghurt (see Table 1) and the amount of enzyme preparation was smaller than in the manufacture of the reference yoghurt. Table 1. Viscosity of reference yoghurt and test yoghurt during the shelf-life.

Example 2. Preparation of yoghurt

[0040] In the example, it was studied how processing milk with transglutaminase during acidifying in accordance with prior art and the use of a yeast extract containing transglutaminase and glutathione during acidifying in accordance with the present invention affected the manufacturing process and the properties of the end product.

[0041] Reference yoghurt was manufactured from raw material mifk having a protein content of 4.2% and fat content of 2.5%. The milk was pasteurized at 92°C for 5 minutes and cooled to a temperature of 42⁰C. 0.252 g of Activa® MP powder (Ajinomoto, contains transglutaminase )/1 ,000 g milk were added to the milk, the yoghurt culture was added, and maturing occurred at a temperature of 42⁰C until pH had fallen to 4.5.

[0042] The test yoghurt according to the invention was manufactured in the same way as the reference yoghurt except that in connection with the culture addition 0.168g/1 ,000 g milk of Activa® YG powder containing yeast extract was added instead of Activa® MP powder.

[0043] The method of the invention enabled the manufacture of yoghurt of the same quality by using a 33% smaller enzyme preparation dosage when Activa® YG powder that contains yeast extract was used as compared with ordinary Activa® MP powder. Consequently, significant savings in enzyme costs are obtained.

Table 2. Viscosity of reference yoghurt and test yoghurt

Shelf- life [days] Reference, viscosity [Pas] Test yoghurt, viscosity [Pas]

3 2.2 2.2

21 2.7 2.6 Example 3. Preparation of yoghurt

[0044] In the example, it was studied how processing milk with transglutaminase enzyme and glutathione together with an acidifying agent in accordance with the present invention in the manufacture of yoghurt and the manufacture of yoghurt without processing with an enzyme in accordance with prior art affected the manufacturing process and the properties of the end product.

[0045] Reference yoghurt was manufactured from raw material milk having a protein content of 4.2% and fat content of 2.5%. The milk was pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. Yoghurt acidifier was added to the milk, and maturing occurred at a temperature of 42⁰C until pH had fallen to 4.5.

[0046] The test yoghurt according to the invention was manufactured from raw material milk having a protein content of 3.65% and fat content of 2.5%. The milk was pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. 0.15g/1 ,000 g milk of Activa® YG powder were added to the milk together with the yoghurt culture, and maturing occurred at a temperature of 42⁰C until pH had fallen to 4.5. In the manufacture of the test yoghurt according to the invention, transglutaminase enzyme and yeast extract were used in addition to the culture.

[0047] The method according to the invention enabled the use of milk having a protein level lowered from 4.2% to 3.65% as raw material milk without any weakening of the quality of the yoghurt. The viscosities of both yoghurts were at the same level and the yoghurts could not be distinguished from one another organoleptically.

Example 4. Preparation of set-type yoghurt

[0048] In the example, it was studied how processing milk with transglutaminase enzyme and glutathione together with an acidifying agent in accordance with the present invention in the manufacture of set-type yoghurt and the manufacture of set-type yoghurt without processing with an enzyme in accordance with prior art affected the manufacturing process and the properties of the end product.

[0049] Reference yoghurt was manufactured from raw material milk having a protein content of 4.2% and fat content of 2.5%. The milk was pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. Yoghurt culture was added to the milk, and maturing occurred at a temperature of 42⁰C until pH had fallen to 4.5.

[0050] The test yoghurt was manufactured from raw material milk having a protein content of 3.65% and fat content of 2.5%. The milk was pasteurized at 92⁰C for 5 minutes and cooled to a temperature of 42⁰C. 0.15g/1 ,000 g milk of Activa® YG powder were added to the milk together with the yoghurt acidifier and brought to maturity at a temperature of 42⁰C until pH had fallen to 4.5.

[0051] The method according to the invention enabled the use of milk having a protein level lowered from 4.2% to 3.65% as raw material milk without any weakening of the quality of the yoghurt. The consistencies of both yoghurts were at the same level and the yoghurts could not be distinguished from one another organoleptically.

Example 5. Preparation of viili

[0052] The test viili according to the invention was manufactured by adding 94 g of milk permeate to 906 g of raw material milk for viili having a fat content of 2.5%. The mixture was pasteurized at 93⁰C for 5 minutes and cooled to a temperature of 65⁰C. The raw material was then homogenized at 65⁰C at a pressure of 200 bar. The raw material was then cooled to an acidifying temperature of 24⁰C and viili culture and 88 mg of Activa® YG enzyme preparation were added.

[0053] Reference viili was manufactured in the same way as the test viili except that 1 ,000 g of raw material milk for viili (fat content 2.5%) were used and no milk permeate or Activa® YG enzyme preparation was added to the milk. Both viilis were packaged in 200 g beakers and the viilis matured at a temperature of 24⁰C until pH fell to 4.5. The viiiis were then transferred to cold storage. During a three-week storage time, the syneresis, the decomposition of the viili on a dish, the taste and the texture were followed organoleptically. In addition, consistency was measured at one week's intervals.

[0054] The method according to the invention enabled the use of milk having a lower protein level than the protein content of the milk used in the manufacture of the reference viili in the manufacture of viili without any weakening of the quality of the viili. Although the protein content of the viili manufactured with the method of the invention was smaller (2.9%) compared with the protein content (3.2%) of the reference viili, the organoleptic properties of both viilis were the same and their consistencies were almost equal.

Example 6. Preparation of fermented milk

[0055] The test fermented milk according to the invention was manufactured by adding 180 g of milk permeate to 820 g of fat-free milk. The mixture was high-pasteurized at 90⁰C for 10 minutes and tempered to an acidifying temperature of 24⁰C. Fermented milk cultures and 100 mg of Activa® YG enzyme preparation were added. The milk was allowed to become acidified for 24 hours until pH was 4.5.

[0056] Reference fermented milk was manufactured in the same way as the test fermented milk except that 1,000 g of fat-free milk were used and no milk permeate or Activa® YG enzyme preparation was added to the milk. Both fermented milks were then mixed and packaged into one-litre packages. The fermented milks were then transferred to cold storage. During a three-week storage time, the syneresis, the taste and the texture were followed organoleptically. In addition, viscosity was measured at one week's intervals.

[0057] The method according to the invention enabled the use of milk having a protein level lowered from 3.3% to 2.7% as raw material milk without any weakening of the quality of the fermented milk. The organoleptic properties of both fermented milks were the same and their viscosities almost equal.

Claims

1. A method of manufacturing a soured fresh dairy product, characterized by adding a transglutaminase enzyme, an enzyme- activating compound, and an acidifying agent to a protein source under such circumstances that the enzyme is active during acidifying, allowing to get acidified, and recovering the preparation obtained.

2. A method as claimed in claim ^characterized in that the enzyme-activating compound is yeast extract.

3. A method as claimed in claim 1 or 2, characterized in that the enzyme-activating compound is glutathione.

4. A method as claimed in any one of claims 1 to 3, characterize d by adding the enzyme and enzyme-activating compound to the protein source before addition of acidifying agent.

5. A method as claimed in any one of claims 1 to 3, characterize d by adding the enzyme and enzyme-activating compound to the protein source during addition of acidifying agent.

6. A method as claimed in any one of claims 1 to 4, characterize d by adding the enzyme and enzyme-activating compound to the protein source after addition of acidifying agent.

7. A method as claimed in any one of claims 1 to 6, characterize d by decreasing the protein content of the protein source used in the method.

8. A method as claimed in claim 7, characterized by decreasing the protein content by adding miik permeate, whey, lactose fraction, a concentrate thereof or a mixture constituted by milk permeate, whey, lactose fraction and/or concentrates thereof.

9. A method as claimed in any one of claims 1 to 8, characterize d in that the protein content of the protein source used in the method is at least 0.5 percent by weight.

10. A method as claimed in any one of claims 1 to 9, characterized in that the protein content of the protein source used in the method is between about 0.5 and about 10 percent by weight.

11. A method as claimed in any one of claims 1 to 10, characterized in that the protein source used in the method is raw material milk.

12. A method as claimed in any one of claims 1 to 11,charac- t e r i z e d in that the soured fresh dairy product is yoghurt, set-type yoghurt, villi, or fermented milk.

13. A soured fresh dairy product, characterized in that it has been manufactured according to the method as claimed in any one of claims 1 to 11.

14. A soured fresh dairy product as claimed in claim ^.characterized in that the product is yoghurt, set-type yoghurt, viili or fermented milk.

15. A method of modifying the texture of a soured fresh dairy product, characterized by adding a transglutaminase enzyme, an enzyme- activating compound, and an acidifying agent to a protein source under such circumstances that the enzyme is active during acidifying.