LU86856A1 - METHOD FOR PRODUCING A FERMENTED DAIRY PRODUCT - Google Patents

Description

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The invention relates to a method for producing a fermented milk product, milk being subjected to ultrafiltration and the retentate obtained being fermented.

Such a method is known from the Dutch patent application 73.06505. This application describes that curd cheese - a fresh cheese - can be made by concentrating milk using ultrafiltration to a volume suitable for making curd cheese and then acidifying it in the usual way.

Although a high-quality food is obtained in this way, it has been shown in practice that the known method does not lead to the production of a product which, in terms of taste and consistency, under all circumstances meets the requirements of the consumer.

In order to fully meet the demands of the consumer, a fermented milk product should taste 'freshly sour' and, incidentally, should be organoleptically acceptable. A disadvantage of the product that is made using the known method is that it is not 'smooth', i.e. it makes a somewhat chalky impression on the consumer. In addition, the organoleptic properties of such a product are not always considered acceptable, which applies in particular to the somewhat bitter and bitter taste (cf. Dairy Industries International 49 (1984) No. 12, page 11).

There is therefore a need for a fermented milk product which is on the one hand considerably 'firmer' than yoghurt and has a higher nutritional value per unit volume, in particular as far as the protein composition is concerned, but on the other hand the above disadvantages and in particular not the 'mouthfeel' which is less valued by some consumers 'of e.g. Quark owns.

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A number of problems are encountered in the manufacture of such a product. It has been shown that an uncomfortable mouthfeel is to a certain extent related to a non-homogeneous structure which is also caused by undissolved gases, in particular gaseous carbonic acid, present in the product.

Furthermore, it has been found that these gases cannot be removed after the fermentation has ended without impairing the structure and strength of such a product.

It has now been found that when a retentate is acidified, in which the ratio of protein to fat is kept at a certain value, while the ultrafiltration leading to the retentate ensures that the nitrogen gas content in the mixture to be fermented is at most 7 mg / kg, the problems described above are avoided.

According to the invention, a retentate with a protein content of 5-8%, a fat content of 0.5-5% and a nitrogen gas content of at most 7 mg / kg is acidified to a pH of 4.4-4.7, after which the product obtained is subjected to such shear forces that a homogeneous mass is obtained with a strength of 10-25, expressed in mm penetration depth per 10 seconds, of a conical body with an apex angle of 90 ° and a mass of 54.8 g.

Without being bound by any theory, it is believed that, using the method according to the invention, the maximum nitrogen gas content selected in the mixture to be acidified, together with the fat / protein ratio therein, the carbonic acid formed during the acidification largely in the Mixture dissolves and is therefore not available as a free gas.

Using the method according to the invention, it is important to ensure that the impact of air is avoided during the entire production process, in particular during and after ultrafiltration and when pumping over the milk and the retentate. If "3 milk is assumed, in which a lot of air has been hammered in, e.g. during the extraction and / or transport thereof, this can generally be brought back to an acceptable level by thermal treatment.

The method according to the invention makes it possible to set the desired final structure of the product within certain limits because the finished product does not need to be degassed. Nevertheless, a nice 'smooth' homogeneous structure is obtained.

To obtain a retentate with the desired fat-protein balance, in principle any milk type, e.g. whole milk or skimmed milk. If necessary, such a quantity of fat or cream or skimmed milk can be added to the retentate that the desired ratio is set.

The gaseous, free nitrogen is generally present mainly as atmospheric nitrogen. The measurement of the amount of free nitrogen present in the starting milk or in the mixture to be acidified can therefore be carried out in a suitable manner using a known measuring method, e.g. by measuring the free oxygen content using a known oxygen meter.

In principle, any known method is suitable for the measure of subjecting the acidified product to sufficient shear forces, and in particular that which is generally used for homogenization. Suitable methods are e.g. the use of a grinding stirrer (Ultra-Turrase), a turbine stirrer, a colloid mill, a homogenizer, etc.

The invention is illustrated by the following examples.

Example I

After pasteurization at 75 ° C., 80 liters of skimmed milk were subjected to an ultrafiltration treatment for 15 seconds using a Pasilac pilot plant ultrafiltration system (with a membrane 4: V ~

Surface of 4 m2) at a temperature of 48 ° C and an applied pressure drop across the membrane of 0.38 MPa. 48 liters of retentate were obtained, which was mixed with 2.5 liters of cream with 40% fat, resulting in a product with a protein content of 5.5% and a fat content of 2.0%. This product was then pasteurized at 85 ° C for 5 minutes and homogenized with a Rannie homogenizer at 65 ° C at a pressure of 20 MPa.

In the entire process described above, care was taken to ensure that there was no question of air entrapment or air intake; As a result, the retentate had a nitrogen gas content of 5.1 mg / kg at the moment of acidification, which was calculated from the analysis of the oxygen gas content (2.97 mg / kg, determined with an oxygen meter according to the Orbisphere model 2714, a membrane detector with a sensor, consisting of a polarographic element that generates an electrical current that is proportional to the amount of oxygen), taking into account the known oxygen / nitrogen ratio in air of 20.9 / 78.1, and assuming maximum solubility at 20 ° C and an atmospheric pressure of 44 mg / kg for oxygen and 19 mg / kg for nitrogen.

This retentate was treated with 1.5% of a BD acid alarm clock, consisting of a mixture of the bacterial strains Streptococcus lactis, Streptococcus cremoris, Streptococcus diacetylactis and Leuconostoc cremoris.

After acidification for 18 hours at 22 ° C. the pH was 4.62, after which the product was stirred with a paddle stirrer for 2 minutes at a speed of 1500 revolutions per minute and a peripheral speed of 9.8 m / s.

The product treated in this way was filled into plastic containers of 500 g and cooled. The product obtained in this way was nice and firm, had a completely smooth structure and had a pure, fresh taste and a pleasant, smooth, non-rough

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Mouthfeel.

The strength of the product was measured at 5 ° C with a penetration meter according to Sommer and Runge, such as in the dissertation 'Verdikken en geleren' by H. Beltman, 'Mededelingen Landbouwhoge-school Wageningen' 75-2 (1975), whereby a cone with an apex angle of 90 ° and a mass of 54.8 g for 10 seconds in the product penetrates. The distance covered was 22.4 mm. Even after 2 weeks of storage in cooling, the product still showed the excellent properties described above; the depth of penetration was 22.2 mm.

Example II

10,000 liters of milk with a fat content of 2.0% were pasteurized for 5 minutes at 90 ° C and then homogenized at 55 ° C with a pressure of 18 MPa.

This milk was ultrafiltered at 50 ° C. using a Rhône Poulenc ultrafiltration system, type Pleiade, membrane type IRIS 3038. 4,500 liters of retentate were obtained with a fat content of 4.4% and a protein content of 7.6%. This retentate was pasteurized at 85 ° C. for 30 seconds and 1% of a BD acid alarm clock (see Example I) was added.

During the implementation of the method, much attention was paid to the fact that the pipeline network was closed, the couplings were closed air-free, air impact during pumping was avoided, the inflow into the tanks and the like. was free of air. This gave a retentate which, at the moment of acidification, had a nitrogen gas content of 6.5 mg / kg (determined as described in Example I).

After acidification for 16 hours at 24 ° C, a pH of 4.58 was reached, after which the product was pumped through a homogenizer, where the product was subjected to a shear rate gradient of about 10,000 s "1 and then pumped through a cooler after a filling device where the product was filled in plastic containers 4 • 6 of 250 g.

The product was nice and firm with a penetration depth of 19.8 mm, measured with the penetration meter (see example I). The product had a very smooth structure, a pure and fresh-creamy taste and the mouthfeel was pleasant, smooth and non-rough.

After storage in the refrigerator for 2 weeks, the properties of the product were completely unchanged and the depth of penetration was 19.9 mm.

Comparative example

The procedure was entirely the same as that of Example II, but no particular attention was paid to air blowing in while the process was being carried out. This resulted in a nitrogen gas content of the retentate at the time of acidification of 15.1 mg / kg.

The end product obtained in this way had no smooth structure, which was both visually perceptible and palpable in the mouth.

This unpleasant mouthfeel generally gave the product a bad taste sensation.

In an attempt to obtain a smooth product, part of the fermented product was subjected to a long intensive stirring treatment. As a result, after about three hours of stirring, the product actually had a somewhat smoother structure, but the strength of the product treated in this way was very low, which was reflected in the penetration depth, which could no longer be measured reproducibly.

Claims (1)

«7 Verenigde Coôperatieve Melkindustrie, Nieuwstad 69, 7201 NM Zutphen Title: Process for the production of a fermented milk product Claim Process for the production of a fermented milk product, whereby milk is subjected to ultrafiltration and the retentate obtained is fermented, characterized in that a retentate with a protein content of 5-8%, a fat content of 0.5-5% and a nitrogen gas content of maximum 7 mg / kg to a pH of 4.4-4.7, after which the product obtained is subjected to such shear forces that a homogeneous Mass is obtained with a strength of 10-25, expressed in mm penetration depth per 10 seconds of a conical body with an apex angle of 90 ° and a mass of 54.8 g.