Method for producing fresh milk having a longer shelf life

Abstract

A method for producing fresh milk having a longer shelf life involves providing raw milk and performing an at least two-step centrifugal germ removal process of the raw milk before a standardization process of the raw milk is carried out. A method may also include performing a first step of a two-step centrifugal germ removal process before a skimming process separating skimmed milk is carried out and performing a second step of the two-step centrifugal germ removal process during the carrying out of the skimming process separating skimmed milk.

Claims

1. A method for producing milk having a shelf life of at least 20 days when stored at a temperature of less than or equal to 8 C., the method steps comprising: (1) providing raw milk; (2) performing a first step of a two-step centrifugal germ removal process; (3) performing a standardization process of the raw milk, after the first step of the two-step centrifugal germ removal process, wherein during the standardization process a skimming process occurs with a skimming separator in order to separate the milk into skimmed milk and cream, and (4) performing a second step of the two-step centrifugal germ removal process with the skimmed milk after the separation of the milk into cream and skimmed milk during the standardization process, wherein each of the at least two steps of the two-step centrifugal germ removal step of step (2) and step (4) is performed with a respective germ removal centrifuge each including a separator having a disk stack made of separation disks, wherein the separator includes fins arranged radially outside the separation disks in a drum of the separator, wherein for each of the at least two centrifugal germ removal steps of step (2) and step (4) there is a recirculation of a substream of clarified liquid withdrawn from the respective germ removal centrifuge to the feed of the respective germ removal centrifuge; wherein the germ removal in the at least two-step centrifugal germ removal steps of step (2) and step (4) is sufficient such that the milk shelf life is at least 20 days when stored at a storage temperature of less than or equal to 8 C.; wherein following step (4), at most 1 Bacillus cereus spore per 10 ml of liquid from which germs have been removed, or fewer of these spores, is detectable; and wherein no sterilized material is added into the milk at any step of the method.

2. The method as claimed in claim 1, further comprising the steps of: prior to step (2), heating the milk to a predetermined skimming temperature; following step (3), heating the standardized milk; then cooling the standardized milk; and then packaging the standardized milk; wherein an amount of cream is divided out from the cream portion generated in the skimming process on the basis of predetermined guide values; and wherein the standardization process of step (3) is performed by mixing the skimmed milk and an homogenized cream which includes at least a portion of the divided-out amount of cream to produce a standardized milk having a predetermined standardized cream concentration.

3. The method as claimed in claim 2, further comprising the step of: heating the cream portion for germ removal after the skimming of the milk.

4. The method as claimed in claim 3, wherein the heating of cream portion step is performed after the skimming of the milk and before the step of dividing out of the amount of cream.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 shows a schematic sequence of a method for producing fresh milk.

(2) FIG. 2 shows a schematic sequence of a first embodiment, according to the present disclosure, of a method for producing fresh milk having a longer shelf life.

(3) FIG. 3 shows a simplified circuit diagram of an arrangement for operating the first embodiment of FIG. 2.

(4) FIGS. 4a, 4b show schematic sequences of two embodiments according to the present disclosure, of a method for producing fresh milk having a longer shelf life.

(5) FIG. 5 shows a simplified circuit diagram of an arrangement for operating the embodiment of FIG. 4a.

DETAILED DESCRIPTION

(6) FIG. 1 shows a flow chart of a known production process for producing fresh milk.

(7) Stored raw milk 100 at a temperature of 2-8 C. is warmed or warmed up using a plate heat exchanger in step 200 to a skimming temperature of 50-60 C., for example, 55 C. Then, the raw milk is centrifugally separated in a separator into cream 310 and skimmed milk 360 in step 300. Or, the milk is skimmed. The cream 310 is then, according to the desired cream content of the milk, divided in step 320, where excess cream, step 340, can be stored, step 350, if desired. Then, the cream is homogenized in step 330 in such a manner that a breakdown of fat balls for stability against creaming results.

(8) The skimmed milk, step 360, is then mixed with the desired amount of cream, standardized, and in step 400 warmed or short-time heated to a temperature of 70-80 C., or for example, 74 C. That is done by way of a plate heat exchanger, and in step 500 kept hot for a correspondingly long time. At this temperature, spoilage-relevant microorganisms are to be destroyed and unwanted enzymes inactivated.

(9) For reduction of germ growth, the milk is then cooled, for example, using a plate heat exchanger, step 600, down to 4-6 C., or for example, 5 C., for storage, step 700. Aseptic packaging of the milk, step 800, in bottles or in aseptic drinking cartons and consumption of the packaged milk is possible in the course of 12 days.

(10) FIG. 2 is a flow chart showing, in addition to the previously known steps, two germ reduction steps, 900, 901, that are added in accordance with an embodiment of a method of the present disclosure. These two germ reduction steps are integrated into the process before the skimming, or before skimming of the raw milk, step 300.

(11) In this embodiment, after heating to a separation temperature of 50-60 C., or for example, 55 C., step 200, the raw milk is freed from bacteria and spores in the two germ-removal steps 900 and 901. Already before the skimming step, a germ removal, or removal of germs from the milk, is thereby carried out at, for example, 55 C.

(12) Therefore, on skimming, not only is substantially spore-free cream, step 310, but also germ-free skimmed milk, step 360, are thereby obtained. The cream in the later course can be added back to the skimmed milk for standardization. Pasteurization of the drinking milk after standardization can proceed, in this embodiment, at 74-85 C., or for example, at 80 C., such that remaining spoilage-relevant microorganisms and unwanted enzymes can be correspondingly destroyed or inactivated.

(13) FIG. 3 shows the circuit diagram of a plant which is operated according to the flow chart shown in FIG. 2. In this embodiment, raw milk passes via a feed Z into a storage tank 1 in which the raw milk is stored at, for example, 4-6 C. From the storage tank 1, the raw milk is passed via subsection 2a of a countercurrent-flow plate heat exchanger 2, where the raw milk is warmed to a temperature of 50-60 C., or for example, 55 C.

(14) The raw milk is then transferred at this temperature into a first germ-removal separator 3. In this step, there is a coarse germ removal from the milk, wherein the number of spoilage-relevant spore formers can be reduced by about 90%.

(15) After the coarse germ removal, the raw milk is transferred into a second germ removal separator 4. In this second germ removal step, germs are reliably cleared in such a manner that at least Bacillus cereus spores are no longer detectable.

(16) The raw milk from which germs have been removed is then skimmed by a skimming separator 5 in which the raw milk is separated into cream and skimmed milk.

(17) The cream leaves the skimming separator 5 via the line 8 and can be kept at, for example, 74 C. by the heat exchanger 9. Alternatively, within the scope of the present disclosure, the heat exchanger 9 can heat the cream to a temperature of 110-140 C., or for example, 125 C., in order in this manner, to connect an additional thermal post-removal of germs. Optionally, in accordance with the present disclosure, a cleaning-in-process, or CIP, of the plant can proceed via a separate feed line.

(18) By way of a valve (not shown), a quantitative division of the cream proceeds, wherein some of the cream can be removed from the process as excess cream E and stored. Alternatively, within the scope of the present disclosure, further additional cream can be fed to the process. After the amount of cream is set to a predetermined value, the cream is passed into a homogenizer 11. The cream is then recirculated to the skimmed milk via a valve (not shown).

(19) This process, also termed standardization, takes place in a connection piece (not shown) as a connection of the skimmed milk line to the cream line.

(20) The standardized fresh milk is then fed via a line to the plate heat exchanger 2 where it is warmed up on passage from for, example, 55 C., see section 2b to, for example, 74 C., see section 2c. For heating the milk, in the present embodiment, steam D is used, which introduces the required heat input in countercurrent by condensation. The milk, for hot holding, is then passed via a further heat exchanger 7. The heating to, for example, 74 C. introduces a mild inactivation of spore formers.

(21) The standardized fresh milk, at, for example, T.sub.milk=approximately 74 C., is then in section 2c of the plate heat exchanger. Then, via the section 2b, where T.sub.milk=approximately 55 C., section 2a, where T.sub.milk=approximately 8 C., and section 2d, where T.sub.milk=approximately 4 C., cooled down to a temperature of 4-6 C. Section 2d, according to the present disclosure, can be designed as ice cooling using a coolant feed CF and a coolant outlet CO. Via an outlet A, the fresh milk that now has a longer shelf life is passed onto an aseptic packaging system. Corresponding measurement and control devices for parameters, such as, for example, pressure, germ count, cell count, temperature, motor power of the separators, have not been shown in the FIG. 3 circuit diagram for the sake of clarity.

(22) In FIGS. 4a, 4b, the two germ-removal steps 900, 901 occur at various sites of the process sequence and are integrated therein. Whereas, in FIG. 4a the first germ removal 900 proceeds before the skimming 300 or the separation of the raw milk into cream, step 310, and skimmed milk, step 360, the germ-removal step 901 serves for removing germs from skimmed milk, step 360. The cream that is separated off, subsequently to the skimming step, is additionally heated to, for example, 125 C. in order to ensure in this manner freedom of the cream from germs.

(23) After the excess cream, step 340, has been separated off, step 320, a predetermined amount of cream is fed to the germ-free skimmed milk 360. Then, the drinking milk is again warmed up, step 400, in order to inactivate any remaining spoilage-relevant microorganisms or enzymes. A hot holding step 500 then follows and also a cooling process, step 600, in such a manner that the resultant drinking milk can be stored and packaged at a temperature of, for example, 5 C. or below.

(24) In the example of FIG. 4a, therefore, a first germ removal from the raw milk proceeds before the separation and a second germ removal from the skimmed milk after the separation of cream and skimmed milk. Therefore, germs are removed separately from both components of fresh milk, cream and skimmed milk, in this process.

(25) Alternatively, it is within the scope of the present disclosure, not to give the homogenized cream a high-temperature heat treatment but to pass it, after the homogenization, back into the skimmed milk for standardization and then to subject this mixture of skimmed milk and cream together to a second germ removal 901. This can then be followed again by the steps 400 to 800 for final processing of the packaged fresh milk (see FIG. 4b).

(26) FIG. 5 shows the circuit diagram of a system which is operated according to the schematic shown in FIG. 4a. In this embodiment, the raw milk, analogously to FIG. 3, is warmed to 55 C. in a plate heat exchanger 2 and then subjected to coarse germ removal in a germ removal separator 3.

(27) In contrast to the working example of FIG. 3, the raw milk from which germs have been removed is skimmed by a skimming separator 5 after the first germ removal step.

(28) After skimming, the skimmed milk is passed into a second germ removal separator 4 where the skimmed milk is again subjected to germ removal, separately from the cream.

(29) The remaining process steps are achieved in a manner similar to FIG. 3 in terms of apparatus.

(30) Compared with the methods of treatment in the pasteurization of traditionally produced fresh milk, in the production of fresh milk having a longer shelf life, in accordance with the present disclosure, greater demands are made of the quality of the raw milk, the processing, with respect to purity, and of storage, with respect to cooling. For instance, for packaging, primarily aseptic packaging comes into consideration. The raw milk should be of the highest quality and generally not older than 48 hours.

(31) Alternatively, to the three embodiments of the present disclosure shown, a two-step centrifugal germ removal after standardization of the milk is with the scope of the present disclosure. For this purpose, for example, as skimming separator, the applicant's model MSE 230-01-777 comes into consideration, and as germ-removal separators, the model CND-215-01-076, additionally converted to a PRO+ system, as described in E1786565, and the model CSE-230-01-777, come into consideration. As germ-removal and skimming separators, continuously operating self-emptying disk separators are, for example, utilized.

(32) In this embodiment, a previously conventional Pasteur system can be retrofitted without problems with two additional germ-removal separators and corresponding heating and cooling devices for cream, in accordance with the present disclosure.

(33) The phase of bacteria and possibly a fraction of milk removed in the embodiment of the method according to the present disclosure, may be subsequently discarded. Sterilization of this phase by heating, that is to say destroying the bacteria and recirculation of such a sterilized phase to the fresh milk from which germs have been removed may not be preferred, since this adversely affects the quality of the fresh milk, in particular the content thereof of -lactoglobulin and lactulose.

(34) -Lactoglobulin is a whey protein which occurs in cow's milk. A high content of -lactoglobulin is an indicator of high milk quality. In the heating of the milk, denaturation of the milk protein occurs and consequently a lower content of whey proteins, and so also of -lactoglobulin.

(35) Lactulose is a byproduct of a rearrangement reaction of lactose which proceeds on heat treatment. Lactulose acts as a laxative and cannot be used by the human body. Lactulose is not present in raw milk. Therefore, a low lactulose content is an indicator of freshness and quality of the milk.

(36) Hereinafter, some guide values are listed for lactulose content and -lactoglobulin content from the directive 92/46/EEC of the Council of the European Community. In addition, a proposal of the German Federal Ministry for Nutrition and Food (BFEL) for the -lactoglobulin content in various processed milk varieties is given.

(37) TABLE-US-00001 Product EU Proposal (92/46/EEC) Proposal of BEFL Sterilized Milk Lower limit >600 mg lactulose/l Lower limit <50 mg -lactoglobulin/l Upper limit <1200 mg lactulose/l UHT Milk Lower limit >100 mg lactulose/l Upper Limit <50 mg -lactoglobulin/l >400 mg lactulose/l Lower limit Peroxidase negative Peroxidase negative High-temperature heat Upper Limit <50 mg lactulose/l >2000 mg - treated milk lactoglobulin/l Upper Limit >2000 mg -lactoglobulin/l Lower Limit Phosphatase negative Phosphatase negative Pasteurized milk Upper Limit Peroxidase positive Peroxidase positive Upper Limit Lactulose not detectable Upper Limit >2600 mg -lactoglobulin/l >3000 mg - lactoglobulin/l

(38) In the table listed above, sterilized milk, ultraheat-treated milk (UHT), high-temperature heat-treated milk and pasteurized milk are compared and guide values for the individual varieties are stated in order to enable a definition of individual milk varieties and to avoid the risk of confusion on the part of the consumer. In this case, a pasteurized milk may be made equivalent to a traditionally produced fresh milk, wherein the processing method is shown in FIG. 1.

(39) Hereinafter, individual measured values of a pasteurized milk from raw milk, from which germs are removed and which was treated according to an embodiment of the method of the present disclosure, according to FIG. 2 are compared with the measured values of a microfiltered milk or direct-heated milk.

(40) In this case, the classification of a pasteurized milk is guided by the guide values stated in the table above for lactulose and -lactoglobulin.

(41) TABLE-US-00002 Product Values Category Pasteurized milk 3810 mg/l -lactoglobulin Pasteurized milk made from raw milk 5 mg/l lactulose from which germs were removed ESL milk produced by 3980 mg/l -lactoglobulin Still pasteurized filtration 9 mg/l lactulose milk ESL milk produced 1490 mg/l -lactoglobulin High-temperature by direct heating 26 mg/l heat-treated milk

(42) As can be seen from the measured values, the pasteurized milk produced from raw milk from which germs were removed is equivalent in quality to pasteurized milk, or traditionally produced fresh milk.

(43) Although the present disclosure has been described and illustrated in detail, it is to be clearly understood that this is done by way of illustration and example only and is not to be taken by way of limitation. The scope of the present disclosure is to be limited only by the terms of the appended claims.