The present invention relates to a new process for producing a fortified composition, in particular a calcium-fortified composition.

Calcium is an important element in human diets for adequate bone formation, and other metabolic functions. The recommended daily allowance (RDA) now termed the recommended daily intake (RDI) of a mineral is the specific recommendation considered by scientific experts to be adequate to meet the need for that nutrient. The RDI is from 800 to 1200 mg/day for adults, in particular around 1000 mg/day for women. Nevertheless, there are several known factors that affect the absorption of calcium by the human body. In healthy adults approximately 30 % of calcium contained in their diets is absorbed.

Dairy products are good source of calcium. However these products contain only limited quantities of calcium in each serving, requiring the person to consume a large quantity of products to obtain the recommended daily allowance (RDA) of calcium. The increased ingestion of dairy products has several drawbacks, which preclude their broad recommendation, such as lactose intolerance by some individuals; or logistics related to the need to monitor the quantity (the number) of products ingested to obtain the RDA.

Therefore, fortified products with an increased amount of calcium are always in demand, in particular a calcium fortified product in ready-to-serve (once daily or twice daily) and readily ingestible form which can provide a substantial amount of the recommended daily allowance of calcium.

Calcium fortification is a current practice in dairy product, in particular milk, especially for osteoporosis prevention. Direct incorporation of a significant quantity of a calcium source in a dairy matrix would be of high interest, specifically for fermented dairy product. However, addition of calcium to milk product, in particular fermented dairy product, can be very difficult. If insoluble sources of calcium are used, precipitation of the salts can occur especially if stabilizers are not used. Moreover, insoluble calcium sources such as tricalcium phosphate or calcium citrate tend to sediment during the fermentation, in the fermentation tank. After fermentation, the fermented dairy product needs to be homogenized, which is often difficult to complete. The risk is also to end up with a fermented dairy product which is not completely homogeneous regarding calcium content, leading to cup to cup variations once packed. If soluble sources of calcium are used, interaction between calcium and milk protein can occur and lead to coagulation of proteins during temperature treatment (pasteurization) and a phase separation. This results from the presence of a significant concentration of free calcium ions in the solution.

Moreover, flavor defects are also not uncommon with fortifying compositions such as dairy products with calcium. For example, some of the organic and inorganic salts used for fortification add taste defects such as grittiness or tangy tastes and/or even a bitter after- taste based on the use of calcium sources.

Consequently, it is desirable to develop a new process for preparing a calcium fortified fermented dairy product, which reduces and/or eliminates at least one of the above-mentioned problems, in particular protein flocculation or sedimentation upon heat treatment and flavor and texture defects. The inventors surprisingly found that when a soluble complex of calcium potassium and an alkaline compound is added in a milk product, which is then fermented, the issues are solved.

The present invention thus relates to a process for preparing a fortified fermented dairy product, preferably a calcium fortified fermented dairy product, comprising the following steps of:

a) mixing a calcium potassium compound with an alkaline compound, in a milk product, to obtain a non-fermented dairy product, and

b) fermenting said non-fermented dairy product to obtain a fermented dairy product.

The present invention also relates to a fortified dairy product obtainable by the process according to the invention.

Milk product as starting material:

As used herein, the term "milk product" is well-understood in the art and usually refers to a product made from whole milk and/or wholly or partly skimmed milk, which can be used in a powder form which can be reconstituted by addition of water. Other milk components can be added such as cream, casein, caseinate (for ex. calcium or sodium caseinate), whey proteins notably in the form of a concentrate (WPC), milk proteins notably in the form of a concentrate (MPC), milk protein hydrolysates and mixtures thereof. The milk and milk components have typically an animal origin such as a cow, goat, sheep, buffalo, donkey, ewe or camel origin.

The milk product is generally first pasteurized before being fermented. The pasteurization step is a heating treatment at a temperature comprised between 65 °C and 120°C, preferably during 2 seconds to 30 minutes, in particular at 95°C during 6 minutes. Such a step and its conditions are well known to the one skilled in the art.

Other food additives can be present in the milk product, notably chosen among:

- sugars and sweeteners: sugars and sweeteners are food- acceptable carbohydrate sweetening agents that may be natural or artificial, no or low calorie sweeteners. Preferred examples of appropriate sugars are sucrose, fructose, lactose, glucose and maltose. Such sugars can be incorporated in the form of beet sugar, cane sugar, maple sugar, molasses, corn syrup, malt syrup, maple syrup, agave nectar or also honey. Preferred examples of appropriate no or low calorie sweeteners are aspartame, sucralose, acesulfame potassium, saccharin, sodium cyclamate, thaumatin, tagatose, neohesperidin dihydrochalcone, isomaltulose, rebaudioside A or also a stevia extract (containing rebaudioside A),

- vitamins (e.g. vitamin A, Bl, B2, B6, B12, C, D, E or K, folic acid, etc.),

- anti-oxidants,

- pH-modifying agents (e.g. buffering agents or acidifying agents such as citric acid and its salts, for ex. sodium, potassium or calcium citrate),

- stabilizers such as agar, pectin,

- gelling/thickening agents such as guar gum, xanthan gum, pectin, starch, gelatine, agar, carrageenan, alginic acid, microcrystalline cellulose,

- emulsifiers such as mono-diglycerides, lactic esters of mono-diglycerides,

- flavouring aromatic agents of synthetic or natural origin (e.g. fruit flavours), and

- colouring agents (pigments, dyes, etc.).

If needed, the skilled artisan will be able to choose appropriate food additives among all the well-known food additives and excipients available on the market.

These food additives can be added before or after the fermentation step allowing the preparation of the fermented dairy product from a non-fermented dairy product, containing thus milk and milk components and optionally other food additives. Non-fermented dairy product:

In the context of the invention, the non-fermented dairy product results from the mixing of a milk product with a calcium potassium compound and an alkaline compound.

The non-fermented dairy product comprises an alkaline compound selected in the group consisting of: sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide, sodium carbonate, dicalcium malate, sodium acetate, potassium acetate, potassium phosphate, sodium phosphates such as monosodium phosphate, disodium phosphate, trisodium phosphate, and mixtures thereof. In the context of the invention, the term "alkaline compound" designates alkali or alkaline salts.

The non-fermented dairy product comprises also a calcium potassium compound which can be notably calcium potassium citrate phosphate or calcium potassium citrate or a mixture thereof. Preferably, the calcium potassium compound is in the form of powder. More preferably, the calcium potassium compound is the Calci-K complex® of Albion® (compound obtained by the process described in WO01/54511). As described in WOO 1/54511, Calci-K complex® belongs to calcium potassium compounds comprising:

- 5 to 28% by weight of phosphate ions, based upon the total weight of the solids in said calcium potassium compound taken as 100% by weight;

- 5 to 32% by weight of citrate ions,

the molar ratio of citrate ions to phosphate ions being from 1: 1.35 to 1:2.35;

- at least 3% by weight of calcium ions;

- at least 15% by weight of potassium ions; and

- less than 5% by weight of water,

said calcium potassium compound having a solid content of at least 35% by weight. Thus, preferably, the calcium potassium compound is as described in the previous sentence. Preferably, the calcium potassium compound is obtainable, preferably obtained, by the following process:

a) mixing citrate ions, calcium ions, potassium ions and water;

b) adding phosphate ions to the mixture obtained in step a), so as to obtain another mixture; and c) heating the mixture of step b) to a temperature comprised between 87°C and 100°C, preferably comprised between 90°C and 95°C, until the desired solid content is achieved.

More preferably, the calcium potassium compound comprises:

- 7 to 15% by weight of phosphate ions, based upon the total weight of the solids in said calcium potassium compound taken as 100% by weight;

- 15 to 35% by weight of calcium ions;

- 15 to 18% by weight of potassium ions; and

- less than 3% by weight of water,

said calcium potassium compound having a solid content of at least 35% by weight. Even more preferably, the calcium potassium compound comprises 18 % of calcium and 17% of potassium.

In the present invention it was found that a soluble source of calcium cannot be used alone in a process for producing a fortified fermented dairy product. While a calcium source where calcium is solubilized in the form of a soluble complex is known to be more soluble and used to calcium fortification of dairy product, a soluble source of calcium cannot be used in a fermented dairy product. Indeed, a calcium soluble complex confers to the dairy matrix a slightly too acidic pH, leading to protein flocculation upon the heat treatment and grainy texture of the fermented dairy product as a consequence. The combination of a calcium soluble complex and an alkaline compound was found to be particularly suitable for producing a fermented dairy product. In other words, it has been found that a mixture of a calcium potassium compound with an alkaline compound, in a milk product, is needed to provide a fortified fermented dairy product with good organoleptic properties and without the issue of protein flocculation upon heat treatment.

In a preferred embodiment, the non-fermented dairy product comprises 0,1 to 0,5 wt%, notably 0,2% to 0,4 wt% of dicalcium malate relatively to the total weight of the fortified fermented dairy product. The chemical formula of dicalcium malate is as follows:

If the amount of dicalcium malate is below 0, 1%, the final product has degraded organoleptic properties (grainy mouthfeel) and a high production of serum during the shelf life.

If the amount of dicalcium malate is above 0,5%, the pH increases which is detrimental for fermentation time and for the stability of the final product.

According to the invention, the alkaline compound is preferably added to adjust the pH of the milk product between 7 and 7,5. The exact quantity of alkaline compound added is not critical to practice of the invention. But it is desired to introduce the alkaline compound in a quantity sufficient to have a pH between 7 and 7,5, in particular between 7, 1 and 7,4 and more particularly between 7,2 and 7,3.

The order of addition of alkaline compound and calcium potassium compound during the mixing step is not critical, although it is preferred that the calcium potassium compound be added to the milk product initially, followed by the addition of the alkaline compound. Preferably the mixing step of the alkaline compound is carried out until reaching a pH between 7 and 7,5 in the non-fermented dairy product.

In a preferred embodiment, to perform such mixing, all ingredients are mixed in a powder form, and then dispersed in water. If desired, an additional amount of alkaline compound is added to adjust the pH.

Fermentation step:

The fermentation step is a lactic fermentation using techniques which are known to skilled person.

When reference is made to a "lactic fermentation", this means an acidifying lactic fermentation which results in milk coagulation and acidification following the production of lactic acid which may be accompanied by the production of others acids, carbon dioxide and various substances such as exopolysaccharides (EPS) or aromatic substances, for example diacetyl and acetaldehyde. To perform such a lactic fermentation, lactic ferments are added to the non-fermented dairy product, which has generally been pasteurized beforehand, and the temperature is kept between 15°C and 45°C, in particular at 38°C. The fermentation is stopped when the fermentation medium reaches a desired target pH. Generally the target pH will be of from 3.7 to 4.9, preferably of from 4 to 4.8, most preferably of about 4.6.

In the framework of the present invention, various ferments can be used for performing the fermentation of the non-fermented dairy product and in particular a culture of lactic acid bacteria such as:

- Lactobacillus sp. (for ex. Lactobacillus bulgaricus, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus pentosus, Lactobacillus helveticus, Lactobacillus reuteri, Lactobacillus plantarum, Lactobacillus bifidus and combinations thereof),

- Lactococcus sp. (for ex. Lactococcus lactis),

- Bifidobacterium sp. (for ex. Bifidobacterium bifidum, Bifidobacterium infantis, Bifidobacterium animalis, especially Bifidobacterium animalis subsp. lactis, Bifidobacterium breve, Bifidobacterium longum and combinations thereof), or

- Streptococcus sp. (for ex. Streptococcus thermophilus, Streptococcus lactis, Streptococcus raffinolactis, Streptococcus cremoris and combinations thereof).

Preferred lactic acid bacteria to be used in the present invention are selected from Lactobacillus bulgaricus, Streptococcus thermophilus, Lactococcus lactis, Bifidobacterium animalis subsp. lactis, and combinations thereof.

In the context of the present invention, a "fermented dairy product" designates more particularly a fermented dairy product ready for human consumption, such as a fermented milk, a yoghurt (a stirred or a set yoghurt). It can be also a strained fermented dairy product such as a strained yoghurt also called concentrated yoghurt or Greek-style yoghurt.

The terms "fermented milk" and "yoghurt" are given their usual meanings in the field of the dairy industry, that is, products destined for human consumption and originating from acidifying lactic fermentation of a milk substrate. These products can contain secondary ingredients such as fruits, vegetables, sugar, etc.

The expression "fermented milk" is thus reserved in the present application for a dairy product prepared with a milk substrate which has undergone treatment at least equivalent to pasteurisation, seeded with microorganisms belonging to the characteristic species or species of each product.

The term "yoghurt" is reserved for fermented milk obtained, according to local and constant usage, by the development of specific thermophilic lactic bacteria known as Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus thermophilus, which must be in the living state in the finished product, at a minimum rate. In certain countries, regulations require the addition of other lactic bacteria to the production of yoghurt, and especially the additional use of strains of Bifidobacterium and/or Lactobacillus acidophilus and/or Lactobacillus casei. These additional lactic strains are intended to impart various properties to the finished product, such as that of favouring equilibrium of intestinal flora or modulating the immune system. The yoghurt can be stirred or set yoghurt. In practice, the expression "fermented milk" is therefore generally used to designate fermented milks other than yoghurts. It can also, according to country, be known by names as diverse as, for example, "Kefir", "Kumtss", "Lassi", "Dahi", "Leben", "Filmjolk", "Villi", "Acidophilus milk".

Fortified fermented dairy product:

By "fortified fermented dairy product" is meant a fortified foodstuff that has been "fortified" by addition of a compound rich in calcium. Fortification with calcium, according to the invention, provides a supplemented or fortified (both terms can be used interchangeably) foodstuff that has organoleptic properties unchanged from unfortified foodstuff. Fortification according to the invention does not adversely affect physical appearance or physical parameters (viscosity, texture...) of the product.

The fortified fermented dairy product obtained by the process according to the invention has a calcium content of at least 250mg, preferably at least 350 mg, more preferably at least 400 mg per 100 g of fortified fermented dairy product.

In the context of the invention, the "calcium content" corresponds to the weight (in mg) of calcium present in the product per 100 g of product.

The calcium content can be measured for example by the method ISO 8070/ IDF 119:2007 which specifies a flame atomic absorption spectrometric method for the determination of calcium, sodium, potassium and magnesium contents in milk and milk products and/or by the AOAC Official Methods (AOAC 991.25, AOAC 984.27, AOAC 985.35 or AOAC 2011.14). If the calcium content is known for all the ingredients used to prepare the fortified fermented dairy product, the calcium content of the fermented dairy product can be calculated from these data.

The amount of calcium potassium compound to add to the milk product is not critical and is dependent upon the calcium content of the non-fermented dairy and the desired level of fortification.

The "fat content" of a product corresponds to the weight of the fat components present in the product relatively to the total weight of the product. The fat content is expressed as a weight percentage. If the fat content is known for all the ingredients used to prepare the fermented dairy product, the fat content of the fermented dairy product can be calculated from these data. The fat content can be any fat content commonly used in fermented dairy products since it is not an essential parameter for the process according to the present invention. The fortified fermented dairy product according to the process of the present invention can have thus a fat content of between 0 and 10%, notably between 1 and 5%, in particular between 1.5 and 4%.

The "protein content" of a product corresponds to the weight of the protein components present in the product relatively to the total weight of the product. The protein content is expressed as a weight percentage. If the protein content is known for all the ingredients used to prepare the fermented dairy product, the protein content of the fermented dairy product can be calculated from these data. The protein content can be any protein content commonly used in fermented dairy products since it is not an essential parameter for the process according to the present invention. The fortified fermented dairy product according to the process of the present invention can have thus a protein content of between 2.5 and 20%, notably between 3 and 10%, in particular between 3.9 and 5%.

As shown in the examples, the fortified fermented dairy product is preferably devoid of grainy texture. By "grainy texture", it is meant a texture with a lot of grains. Preferably, the fortified fermented dairy product has a smooth, homogenous texture.

Preferably, the fortified fermented dairy product has less than 10 ml of serum per 125 g of product after 14 days of preparation. For the measurement of serum production, the product is prepared and put at 10°C during 14 days, and then turned out in a plate and the production of serum collected in the plate is measured in a graduated tube (in ml).

Preferably, the fortified fermented dairy product has a viscosity of at least 400 mPa.s, in particular 14 days after preparation. The viscosity is measured with a Rheomat RM 200 at a temperature of 10°C and at a shear rate of 64 s ^"1 .

The fortified fermented dairy product can be in any container commonly used for fermented dairy product with any shape. The container can be made notably of plastic, metal (e.g. aluminium), glass or combinations thereof.

The container can be in particular a container for a single serving. It will be more particularly adapted for a portion of fortified fermented dairy product of 50 to 250 g. For example, a portion of 150g of fortified dairy product according to the invention can provide between 375 mg and 750 mg of calcium in a serving. According to a more preferred embodiment, the process according to the invention comprises the following steps of:

a) mixing a calcium potassium compound with an alkaline compound in a milk product, to obtain a non-fermented dairy product,

said alkaline compound being introduced in a quantity sufficient to have a pH of the non-fermented dairy product between 7 and 7.5, and

b) fermenting said non-fermented dairy product to obtain a fermented dairy product.

According to a preferred embodiment, the process according to the invention comprises the following steps of:

a) mixing calcium potassium citrate phosphate with dicalcium malate, in a milk product, to obtain a non-fermented dairy product,

said dicalcium malate being introduced in a quantity sufficient to have a pH of the non-fermented dairy product between 7 and 7.5, and

b) fermenting said non-fermented dairy product to obtain a fermented dairy product.

According to a preferred embodiment, the process according to the invention comprises the following steps of:

a) mixing calcium potassium citrate phosphate with dicalcium malate, in a milk product, to obtain a non-fermented dairy product, said dicalcium malate being introduced in a quantity sufficient to have a pH of the non-fermented dairy product between 7 and 7.5, and

b) fermenting said non-fermented dairy product with lactic acid bacteria such as Lactobacillus bulgaricus, and/or Streptococcus thermophilus and/or Lactococcus lactis, and/or Bifidobacterium animalis subsp. lactis, to obtain a fermented dairy product

EXAMPLES The following examples set forth preferred processes in accordance with the invention. It is to be understood, however, that these examples are provided by way of illustration and nothing therein should be taken as a limitation upon the overall scope of the invention.

Characterization of the ingredients

The ingredients used in examples are defined as follow:

-CPCP: calcium potassium citrate phosphate distributed by the Albion company under the name of Calci K complex®. It has a calcium content of around 18%. This ingredient can be made according to a method detailed in the international patent application WOO 1/54511. -DCM: dicalcium malate distributed by the Albion company. It has a calcium content of around 30%. This ingredient can be made according to a method detailed in the international patent application WO2004/050031.

-Ca(OH)2: calcium hydroxide distributed by the Shaefer company under the name of PRECAL®54. It has a calcium content of around 54%.

- Na ₃ P0 ₄ : trisodium phosphate or NaOH: sodium hydroxide.

-Milk product: The milk product is made by mixing skimmed milk, cream, milk protein concentrate and skimmed milk powder. The milk product has a protein content of around 4% and a fat content of around 1,5%.

Preparation of the products

For each test, the ingredients above mentioned were combined in continuous mixing, in order to achieve a pH between 7 and 7.5. Then, the mixture was heated to a temperature of 95 °C for 6 minutes. Lactic acid bacteria were inoculated and the fermentation was stopped when the fermentation medium reaches the target pH 4.65. All examples expect the "H" test, have an added calcium content of around 300mg/100g and a total calcium content of around 440 mg/lOOg of fermented dairy product.

A comparative example has been carried out without mixing alkaline compound (test B).

Characterization of the products

For each test, the viscosity was measured, the mouthfeel was determined and the serum production was measured after 14 days at 10°C.

The viscosity was measured with a Rheomat RM 200 at a temperature of 10°C and at a shear rate of 64 s ^"1 .

The mouthfeel was determined by a sensory panel of testers. It was asked to these testers to determine the mouthfeel for each product (A to L). The expression "smooth" designates that the product has acceptable organoleptic properties (e.g. homogeneous texture) whereas the expression "grainy ++" designates that the product presents a lot of grains (heterogeneous and rough texture).

For the measurement of serum production, each product is turned out in a plate and the production of serum collected in the plate is measured in a graduated tube (in ml).

Results are presented in the tables below.

Table 1

The examples above demonstrate that a fermented dairy product without alkaline compound (test B) has degraded organoleptic properties (grainy mouthfeel) and a high production of serum during the shelf life.

In test C, a high quantity of alkaline compound induces an important pH rise which is detrimental for fermentation time and for the stability of the final product.

Table 2

Test CPCP NaOH Ca(OH) Na ₃ P0 ₄ pH of the non- Fermentation Texture Mouthfeel Serum (g i) (mg/1) ₂ (g/i) (g/i) fermented time D + 14 D + 14 dairy product (hours) (mPa.s) (ml/125g)

D 16.45 0.33 - - 7.27 8h00 800 Smooth 5

E 13.17 - 1.11 - 8.1 8h50 360 Smooth 23

F 14.81 - 0.55 - 7.2 7h30 1100 Smooth 3

G 15.14 - 0.44 - 7 7h40 1300 Smooth 7

H 16.45 - 0.70 - 7.25 6h45 1000 Smooth 1

I 16.45 - - 2.78 7.22 8h00 850 Smooth 9

Table 3

These tests evidence the importance of the combination of a calcium potassium compound with an alkaline compound in a dairy product.