Fermented dairy products Field of the invention

The present invention relates to fermented dairy products having reduced protein content and to a process for manufacturing such products.

Background of the invention

Texture and particularly viscosity or sensorial consistency of fermented dairy products is positively correlated with protein content which enables the formation of acidified gels. Since dairy protein is one of the most expensive components in finished products such as fresh cheeses, quarks, tvorogs or simply yoghurts, manufacturers have always tried to reduce their content. On top of the cost, a high amount of dairy protein increases recipe-buffering capacity which leads to a rather acidic fermented product and possibly bitterness defects during storage.

Different attempts have been made in the art to reduce the protein content like optimizing the cultures, the processing conditions or including stabilizers system mainly composed of modified starches, gelatin and/or low methoxyl pectins.

The use of hydrocolloids in fermented dairy products is well known. For example, US 2,956,885 teaches that combining instant starch with carboxy methylcellulose allows the production of dried baker's- type cheese. This document is silent about any possible reduction of the protein content.

FR 2 326 875 discloses a thickener system containing carboxy methylcellulose, xanthan gum and locust bean gum. Optionally some starch is added to the system. This combination simulates the formation of a lactic gel during acidification and avoids the precipitation of the protein.

After that, WO 96/03860 describes that on one side mixtures of carboxy methylcellulose and gelatin and on the other side mixtures of gelatin and locust bean gum are useful stabilizers, particularly to help fresh cheeses retain their shape without suffering from syneresis and have the required mouthfeel.

US application 10/134,020 aims at the production of mozzarella which does not exhibit liquid losses and allows a hot filling. This is obtainable thanks to the use of xanthan gum in combination with locust bean gum.

Fermented Dairy products and particularly fresh cheeses, quarks, or tvorogs have a protein content usually between 10 and 15% by weight of the lactic curd. As discussed previously, proteins are quite expensive but any reduction of their content results in a loss of texture and a higher tendency to syneresis.

As apparent from the art, there is still a need for fermented dairy products having a lowered protein content while keeping their original features of smoothness, shape and liquid retention. Another need is to avoid the use of gelatin which is not well perceived by consumers. The present invention fulfils these needs.

Summary of the Invention

The present invention pertains to a fermented dairy product containing a stabilizer system comprising carboxy methyicellulose, starch and at least a galactomannan but said stabilizer system does not comprise xanthan gum, gelatin, carrageenan, microcrystalline cellulose and mixtures thereof. The galactomannan is preferably locust bean gum, tara gum, cassia gum and/or guar gum, more preferably locust bean gum and/or tara gum, and even more preferably locust bean gum.

The fermented dairy products according to the present invention are preferably fresh cheeses, fermented milks or yoghurts.

Also part of the present invention is a process for the manufacture of fermented dairy products comprising the steps of standardizing milk, and adding a starter culture to acidify the milk to a desired pH. Optionally, the pH can be adjusted by adding some food acidulants. After that, the whey serum can be removed and the stabilizer system comprising carboxy methyicellulose, starch and at least a galactomannan but not containing xanthan gum, gelatin, carrageenan, microcrystalline cellulose and mixtures thereof is added. Optionally, the starch can be added during milk standardization.

Another object of the invention is the use of the stabilizer system in order to reduce the protein content of the fermented dairy product while keeping its matting, water

binding and textural properties. The protein content reduction varies depending on the application but the decrease is preferably from 20 to 80 %.

Detailed Description of the Invention

All the percentages herein are percentages by total weight unless stated to the contrary.

The fermented dairy product according to the present invention contains a stabilizer system which comprises carboxy methylcellulose, starch and at least a galactomannan. This stabilizer system allows a reduction of the protein content while simultaneously keeping the textural properties intact. This stabilizer system does not contain xanthan gum, gelatin, carrageenan, microcrystalline cellulose and mixtures thereof.

By "fermented dairy products" it has to be understood fresh cheeses, quark, tvorog, mato, mozzarella, yoghurts, flavored yoghurts, fermented cream, sour cream and any products based on the fermentation of milk or obtained by direct acidification and normally containing at least 3% of proteins, preferably at least 6%, more preferably at least 8% and most preferably at least 10%. In the context of the present invention, the fermented dairy product contains viable microorganisms. In a preferred embodiment, the fermented dairy product is fresh cheese or yoghurt. In a highly preferred embodiment the fermented dairy product is fresh cheese.

In a preferred embodiment, the fermented dairy product according to the invention comprises a stabilizer system which contains carboxy methylcellulose, starch and locust bean gum, cassia gum, tara gum and/or guar gum. In a more preferred embodiment the stabilizer system comprises carboxy methylcellulose, starch and locust bean gum and/or tara gum. In an even more preferred embodiment the stabilizer system according to the present invention comprises carboxy methylcellulose, starch and locust bean gum. In a most preferred embodiment, the stabilizer system according to the present invention consists of carboxy methylcellulose, starch and locust bean gum, tara gum, cassia gum or guar gum and mixtures thereof.

Carboxy methylcellulose is a polymer of insoluble anhydroglucose units which react with monovalent salts to render it soluble. The number of anhydroglucose units corresponds to the degree of polymerization (DP). Each anhydroglucose contains 3 hydroxyls groups able to be substituted by carboxymethyl groups; this corresponds to the degree of substitution (DS). These substitutions confer an anionic profile to the carboxymethyl cellulose allowing it to react both with proteins and other hydrocolloids. Without being bound by any theory, it is believed that carboxy methylcellulose forms, at acidic pH between 3 and 6 and particularly at pH of about 4.6, complexes with proteins and particularly with caseins. Theses complexes are soluble, highly viscous, and stable to acidic pH even during prolonged storage.

In the present invention the carboxy methylcellulose is used both for its texturizing properties and its ability to interact with proteins and hydrocolloids. The carboxy methylcellulose used in the present invention preferably has a viscosity, when present in 1% water solution, of from about 1000 to about 10000 cps, more preferably from 1000 to 5000 cps, even more preferably from 2500 to 3500 cps when measured by Brookfield method. The DS of the carboxy methylcellulose according to the invention is preferably from about 0.7 to about 1.2, more preferably about 0,90 to about 1.1, even more preferably about 1.

Within the context of the present invention, the term "starch" denotes a mixture of two molecular entities, namely amylose and amylopectin. Amylose is the starch polysaccharide that primarily consists of long chained α-l,4-linked D-glucose molecules with a degree of polymerization (DP) of typically about 500 to 5,000. Amylopectin consists of relatively short chain α-l,4-linked D-glucose molecules interconnected by many α-l,6-branch points. The molecular weight of amylopectin molecules is typically in the range of several millions. The amylopectin to amylose ratio can vary between 100:0 and 10:90 depending on the plant source. Typical commercial starch sources that may be used within the present invention are maize, waxy maize, high amylose maize, wheat, potato, tapioca, rice, pea and sago.

Starches are typically organized in the form of cold water insoluble granules with a diameter usually ranging from 0.5 μm to about 1.0 μm.

In addition to starch also "modified starches" may be used in the context of the present invention. Modified starches in the sense of the present invention are starch products whose properties have been altered by physical or chemical means or by the introduction of substituents and whose granular and molecular structures,

respectively, are more or less retained. Chemical modification can include esterification or etherification and oxidation reactions at the hydroxyl groups at carbon atoms 2, 3 and 6 of the D-glucose residues. Typical substituents at the hydroxyl groups in modified starches are acetyl, n-octenyl succinate, phosphate, hydroxypropyl, or carboxymethyl groups. Furthermore, the modification can also lead to the formation of cross-links by appropriate substituents, such as phosphate, adipate or citrate. These chemical modifications can be followed by scission of the glucosidic α-1,4 and α-1,6 bonds. Such a partial degradation of starch is usually obtained by treatment with acids, oxidizing agents or with hydrolytic enzymes. Finally, the modified starches also may include native or modified starches that have been converted into a cold-water dispersible form by a heat-moisture treatment followed by drying (e.g. drum drying or spray-cooking). Maltodextrins are also part of this definition.

In a preferred embodiment, chemically modified starches or thermally inhibited starches are used.

The third component of the inventive combination is at least a galactomannan chosen from the group consisting of locust bean gum, tara gum, cassia gum and guar gum. Locust bean gum is insoluble in cold water even if it can partially swell. Tara gum is partly soluble in cold water. Cassia gum is insoluble in cold water. Guar gum is soluble in cold water.

Without wishing to be bound by any theory, it is believed that carboxy methylcellulose interacts via hydrogen bonds with the large region non-substituted in the galactomannan. At this point, the galactomannan is adsorbed to the cellulosic part of the carboxy methylcellulose and an increase of the thickening power is observed. Starch by binding a large quantity of water improves and increases the thickening power while developing additional mouthfeel.

According to the present invention, the weight ratio of carboxy methylcellulose to galactomannan in the stabilizer system is preferably from 4:1 to 1:1, more preferably from 3:1 to 1:1, most preferably about 2:1. The weight ratio of carboxy methylcellulose and galactomannan to starch in the stabilizer system is preferably from 1:20 to 1:5, more preferably from 1:10 to 1:3, most preferably about 1:1 to 1:2.

The combination of hydrocolloids of the inventive fermented dairy product has shown a synergestic effect. Indeed, some attempts have been made to stabilize fermented dairy products by using carboxy methylcellulose or starch alone and the inventors were not able to obtain a gel suitable for such kind of products; the product was liquid. When the inventors tried to use only locust bean gum, cassia gum, tara gum and/or guar gum to stabilize the fermented dairy product, the texture was not suitable either; it was grainy and the viscosity was insufficient.

Another feature observed by the inventors is that the presence of other hydrocolloids can have a detrimental effect on the stabilizing power of the present stabilizer system. Indeed, it has been observed that when low methoxyl pectins, for example, are included in the formulation the re-texturization which normally occurs after heat treatment is unsatisfactory. It has also been observed that the addition of alginates, carrageenan or xanthan gum causes precipitation of the proteins.

Other hydrocolloids can, however, be added without destroying the synergy of the inventive stabilizer system. For example, agar or high-methoxyl pectin and mixtures thereof can be added.

The fermented dairy product according to the present invention preferably contains less than 3% of the stabilizer system, preferably less than 1.8%, more preferably less than 1.0% and most preferably less than 0.75%

Also part of the invention is a process for the manufacture of a fermented dairy product comprising the steps of:

(i) Standardizing milk,

(ii) Adding starter cultures and letting them ferment until reaching a suitable pH and/or adding food acidulants until reaching a suitable pH, (iii) Removing the serum to obtain a curd,

(iv) Adding the stabilizer system to the curd, (v) Mixing and,

(vi) Optionally filling in pack.

In a preferred embodiment the milk is first standardized to the desired level of protein and fat; in an embodiment the starch is added at this step. After that, the

standardized milk is often pasteurized at this stage to remove the pathogenic organisms. Then said milk is inoculated with a starter culture of an acid-forming microorganism and optionally with food acidulants. After that, the inoculated milk is allowed to ferment for about 12 to 24 hours. When the pH approaches the iso- electric point of the caseins, the protein coagulates. In the case of, for example, fresh-cheese production, whey is then removed by natural drainage, centrifugation or ultra-filtration. If a yoghurt is manufactured, the removal of the whey is not necessary. The stabilizer system according to the invention is preferably injected after the whey removal in order to avoid losses and to recover a whey serum free of hydrocolloids. In order to optimize the texture, a mixing step is done, preferably by gentle stirring. Further ingredients may be added simultaneously; these can include butter, cream, vegetable fats, herbs, spices, salt, aroma, flavoring agents, fruit preparation and mixtures thereof. Finally, a heat treatment may be applied at this stage, often a pasteurization. Such a heat treatment step serves to destroy pathogenic microorganisms but also has the advantage of increasing the consistency of the curd. The stabilizer system according to the invention avoids whey-off and textural defects such as sandiness and graininess.

In a preferred embodiment, the stabilizer system is also injected directly in the fresh cheese or yogurt to avoid whey removal in order to increase production yield.

Otpionally, when composed of separated ingredients, the stabilizer system can be added for a part (starch) during milk standardization and the remaining (carboxy methylcellulose and at least a galactomannan) directly in the fermented dairy product according to the present invention.

In another embodiment the coagulation can occur by acid alone or the combined action of acid and heat; in this case the pH of coagulation is slightly higher than the iso-electric point of the caseins (about 4.6).

It has been observed that when the carboxy methylcellulose is included in the fermented milk at a pH above about 6, the stability of the complexes formed with proteins is lower. Thus it is preferable to let the milk acidify until a pH lower than 6 is reached before including the stabilizer system according to the present invention.

In a highly preferred embodiment the stabilizer system is injected through a pre- solution. The pre-solution, amongst the three essential types of components,

additionally contains water and the stabilizer system according to the present invention. In a preferred embodiment, the pre-solution represents from 15 to 80 % of the weight of the finished dairy product, preferably from 20 to 60%, more preferably from 20 to 40%. In yet a further preferred embodiment, the pre-solution is injected after the removal of the whey serum.

In a highly preferred embodiment, the present invention is a fresh cheese containing about 75% standardized milk and about 25% pre-solution. In this embodiment, the pre-solution preferably contains about 97.5% of water, about 0.25% galactomannan, about 1.75% starch and about 0.5% of carboxy methylcellulose

The present invention also pertains to the use of a stabilizer system comprising carboxymethyl cellulose and at least a galactomannan to decrease the protein content of fermented dairy products. Indeed, using said stabilizer system in fermented dairy products enables a protein reduction up to 80%. This decrease varies depending on the initial amount of protein in the product and on the application per se. In a preferred embodiment, the stabilizer system according to the present invention enables a reduction of the protein content of about 60%, preferably between 10 and 40%, more preferably between 20 and 40%.

Using the present stabilizer system in fresh cheeses allows a reduction of the protein content of at least 10% in fresh cheeses, preferably at least 15%, more preferably at least 20% and most preferably about 25%. When used in yoghurts, the reduction of the protein content is preferably from 20 to 40%, more preferably from 25 to 35%.

In a preferred embodiment, also encompassed by the present invention is a method of decreasing the protein content in fermented dairy products by adding a stabilizer system comprising carboxy methylcellulose, starch and at least a galactomannan to a fermented dairy base. Without wishing to be bound by any theory, it is believed that the combination carboxymethylcellulose and at least a galactomannan allows the protein reduction in fermented dairy product whereas starch is added for further reducing syneresis and for texture purposes.

The protein reduction achievable is at least 10% in fresh cheeses, preferably at least 15%, more preferably at least 20% and most preferably about 25%. When used in yoghurts, thε reduction of the protein content is preferably from 20 to 40%, more preferably from 25 to 35%.

The invention is further defined by reference to the following examples describing in detail the preparation of the present invention. The invention described and claimed herein is not to be limited in scope by the specific embodiments herein disclosed, since these embodiments are only intended as illustrations of several aspects of the invention. Any equivalent embodiments are intended to be within the scope of this invention. Indeed, various modifications of the invention in addition to those shown and described herein will become apparent to those skilled in the art from the foregoing description. Such modifications are also intended to fall within the scope of the appended claims.

Example 1: Reduction of the protein content

A fresh cheese was manufactured with a classical formulation and compared with a fresh cheese according to the present invention.

Table 1: Formulations used

Preparation of the Pre-solution:

The carboxy methylcellulose, starch and the locust bean gum were in powdered form. The powders were blended and dispersed into water at ambient temperature using a THERMOMIX at speed 4. The dispersion was then heated in the THERMOMIX at 90 ⁰ C during 5 minutes. The dispersion was then cooled until 25°C and maintained at this temperature.

Preparation of the Dairy base:

Standardized milk was inoculated with a conventional starter culture and fermentation was allowed until reaching a pH of 4.6.

Preparation of the comparative samples:

The fermented milk was then centrifuged in order to remove the whey.

The curd was then divided in 3 portions. The first one was the normal fresh cheese with 10% protein. The second one was maintained at 25°C in a scrapped surface heat exchanger in order to add 25% of pre-solution and then it was mixed at this temperature and then stored at 5°C. In the last one, 25% of water was added in the same conditions in order to decrease the protein content to 7.5%.

The viscosity of the 3 portions was measured using HAAKE viscosimeter, the fresh cheese containing 7.5% of proteins was almost liquid whereas the fresh cheese containing the stabilizer system according to the present invention exhibits a viscosity which was even higher than the fresh cheese with 10% proteins.