MXPA97004365A - Method for preparing dairy products that have storage life increment - Google Patents

Abstract

A method for preparing dairy products which have increased storage life by incorporating carbon dioxide into such products, which comprises contacting a fluid milk fraction of a dairy food with carbon dioxide, mixing the fluid milk fraction and carbon dioxide in a solution and, subjecting the solution to conditions sufficient to reach a stable state between the fraction of fluid milk and the dissolved carbon dioxide. The invention is adapted for dairy products of a wide variety, such as milk, whey, yoghurt, sour cream, cottage cheese, ricotta cheese, other mild, semi-soft and hard cheeses, ice cream mixtures and the like.

Description

METHOD FOR PREPARING DAIRY PRODUCTS THAT HAVE LIFE OF INCREASED STORAGE FIELD OF THE INVENTION This invention relates generally to the use of carbon dioxide in the processing of dairy products to increase its refrigerated storage life. More specifically, the invention is directed to a method for incorporating carbon dioxide into dairy products. The method of the present invention provides dairy products that have storage life without compromising the appearance and taste of the product.

BACKGROUND OF THE INVENTION It is well known that dairy products have a limited storage life in the dairy industry. The "storage life" of dairy products is defined as the time between manufacturing or processing and when the product is considered inappropriate for consumption by the buyer. Usually dairy products are considered unsuitable for consumption due to the presence of flavors in the taste, changes in the physical appearance or appearance of the ferment or molds.

One of the main causes of taste flaws, changes in the physical appearance and appearance of ferment or molds, in dairy products is the activity of microbes. Fresh milk is a complex biological fluid that includes fats, proteins, minerals, vitamins, enzymes, sugar and various microorganisms. Although fresh milk contains very few microorganisms, additional microbes can enter fresh milk due to environmental factors that include contamination during transport, storage and processing. The microorganisms present in fresh milk eventually lead to putrefaction of milk, as well as milk products produced from milk. This is because certain bacteria are found in milk, while other bacteria produce enzymes of milk degradation, both leading to putrefaction of milk and milk products due to their biochemical activity. These microorganisms will grow (some even under low temperature conditions), increasing bacterial counts and the amount of enzymes present in dairy products, unless they are removed, destroyed or controlled. It is considered that the presence and growth of microorganisms in fresh milk has a direct correlation with the time during which the dairy products are suitable for consumption, that is, the storage life. In fact, several countries have established classifications for fresh milk based on bacterial counts. Milk and milk products with bacterial counts above the prescribed limit are considered unsuitable for consumption. The microorganisms in milk and milk products include several types of bacteria which, among other things, lead to their putrefaction. In pasteurized milk, putrefaction is frequently exhibited by a separation of milk associated with a sour flavor; In cottage cheese, putrefaction is often exhibited by a "whey separation" effect where a milky white layer is separated from the solids portion of the product, and may also be associated with the growth of the ferment or mold on the internal seal of the product. package; and in ice cream, putrefaction is frequently exhibited by a lack of flavor in the product. Factors that affect the storage life of dairy products include: (1) the presence of thermoduric bacteria in raw milk, which are able to grow under refrigeration; (2) the presence of psychotropic bacteria, as well as heat-stable enzymes produced by said bacteria, in foods and dairy products, which are also capable of growing under refrigeration and eventually cause putrefaction as a result of their biochemical activity; (3) the storage temperature, which when raised increases the growth rate of the bacteria; (4) the action of lipase (an enzyme) on fatty corpuscles in raw milk, which can result in rancid flavors in the final products; and (5) excessive temperatures (> 75 ° C) during pasteurization, which can germinate microbial spores present in fresh milk that are capable of growing at low temperatures. It has been recognized, therefore, that it is important to limit microbial growth in milk as early as possible in its processing. This will limit the production of enzymes that degrade milk and milk products, resulting in the extension of shelf life. In industry, the bacterial growth in fresh milk has traditionally been controlled by keeping the milk in a low temperature environment during storage and transportation until the milk is processed in, for example, a dairy plant. At the beginning of milk processing, bacterial growth is further controlled by the destruction or substantial removal of the existing bacteria. Traditional means of destroying such bacteria have focused on the heat treatment used in the pasteurization process. Ultrafiltration techniques have also been developed to remove bacterial contamination, without heat treatment. However, not all psychotropic bacteria are associated with pasteurization (or ultrafiltration) and are problematic as they continue to grow in fluid milk and dairy products through standard dairy operations. In addition, after pasteurization, fluid milk and / or dairy products are frequently kept in holding tanks for long periods between the processing steps and before packing and, therefore, are subject to further bacterial growth. In addition, it is known that psychotropic bacteria produce heat-stable proteolytic enzymes and enzymes that are not destroyed during pasteurization. These enzymes break down proteins and fat in dairy products, during and after processing, eventually causing their putrefaction. In an effort to extend the shelf life of dairy products by controlling bacterial growth, the dairy industry initially focused on the higher heat treatment of fluid milk, using a process commonly referred to as "ultrapasteurization" or ultrapasteurization. (also called UHT, ultraheating or ultra-high temperature treatment) uses a substantially higher temperature scale (generally around 130-150 ° C) for pasteurization which is considered to destroy all psychotropic bacteria and can provide a storage life of Up to five months Ultrapasteurization has the disadvantage, due to the high heat, of changing the taste and appearance of the treated fluid milk, giving the milk a cooked or burnt taste and a slightly toasted or caramelized appearance. may result in an increase in the shelf life The taste and appearance are sacrificed. Therefore, ultrapasteurized dairy products have not been widely accepted by the general public due to this change in taste and appearance. Alternative efforts have focused on improving packaging as a means to increase the storage life of dairy products. Modified atmosphere (or MAP) packaging, which uses various types of barrier materials, has been developed for use with various food products. Containers with inner layers and overwrap, made of metal foil, mylar film, polyethylene and polyvinylidene chloride casing, are currently being used in various sectors of the food industry for this purpose. The "fresh" pasta available in the refrigerated section of supermarkets uses MAP packaging. Carbon dioxide has also been added to the top space of those vessels to inhibit oxidation. Nevertheless, those packages commonly exhibit a bulging or "bulging" effect, apparently due to the amount of gas in the upper space. Although this may not be of interest with respect to "fresh" pasta, it is considered that consumers of dairy products would consider such "bulging" to be indicative of inferior quality. It is also confusing how excess gas in the upper space can affect the taste of those products, since those foods are normally sewn before consumption.

However, the dairy industry has begun to use a MAP form with better barrier packaging materials, especially metal foil and mylar film, for internal seals. The examination has also shown that CO2 can be added to the headspace of such MAP containers resulting in some way in a longer storage life. Maniar et al., Have reported that the storage life of the cottage cheese extended from an expected storage life of 21 days to approximately 28 days, where the containers were packed using MAP, with the C02 added to the upper space of the container and stored at 4 ° C. Maniar, A.B., Marcy, J.E., Bishop, J.R., and Duncan, S.E., "Modified Atmosphere Packaging to Mantain Direct-Set Cottage Cheese Quality," J. Food Sci., 1991, vol. 59, no. 6, pp. 1305-1308. However, the results, so far, have not shown a substantial increase in storage life and have not yet shown the effects on the taste and appearance of the product. Researchers have also studied the use of carbon dioxide in dairy products to increase storage life. It is known that carbon dioxide inhibits the growth of Gram-negative bacteria that includes the psychotropic bacteria commonly found in fresh fluid milk. It was considered, and research in this area suggests, that carbon dioxide can dissolve in milk to inhibit bacterial growth. In unprocessed milk, King and Mabbitt reported an increase in preservation of unpasteurized farm milk from approximately 3 days to approximately 6 days, by the addition of carbon dioxide at a concentration of 30 mmol / L, stored at 7 ° C. King, J.S., and Mabbitt, L.A., "The Use of Carbon Dioxide for the Preservation of Milk," Soc. Appl. Bacteriol. Tech. Ser., 1987, vol. 22, pp. 35-43. King and Mabbitt concluded that their experiments showed that the addition of C02 to refrigerated milk doubled the storage time of unprocessed milk without putrefaction by psychotropics. However, such studies have been directed only to the use of CO2 with unprocessed milk. In addition, King and Mabbitt note that the C02 must be removed from the milk by heating and light agitation to be suitable for consumption. To the extent that the moment that C02 is removed by heat and agitation, it is considered that CO2 would be removed by pasteurization and homogenization in standard dairy operations, thus eliminating its effect as an inhibitor of bacterial growth that follows the pasteurization. Although CO2 must remain in the milk, and if it is necessary to remove the CO2 by heating and agitation before consumption, it is considered that such a carbonated product would not be suitable for use in packaged dairy products. The use of carbon dioxide within consumable fluid products has generally been limited to carbonated beverages, such as soft drinks and mineral waters. However, such carbonation levels are not considered adequate for dairy products. While carbonated milk drinks have been prepared, such drinks do not have the taste or appearance of ordinary dairy products. As described in U.S. Patent No. 4,804,552, carbonated liquid dairy products are prepared so that the taste and mouth feel of the carbonated dairy product is no longer that of the non-carbonated dairy product. Carbonation generally reduces the pH of carbonated beverages, resulting in a taste that is somehow acidic. In addition, it is known that such beverages exhibit an effervescent appearance. It is considered that carbon dioxide has not been generally used in dairy products since its addition can result in a lack of acid flavors (since carbon dioxide is a weak acid) and effervescence (due to carbonation), none of which is acceptable to the consumer. However, the use of carbon dioxide in dairy products seems to be an attractive alternative to previously used methods to increase storage life. Recent studies have suggested that carbon dioxide can be added to dairy products at relatively low levels to obtain a substantial extension of storage life without adversely affecting appearance. Chen and Hotchkiss have reported that C02 dissolved in the creamy dressing of cottage cheese before mixing with rennet and packing in high barrier containers can inhibit the growth of Gram-negative bacteria. Chen, JH, and Hotchkiss, JH, "Effect of Dissolved Carbon Dioxide on the Growth of Psychrotrophic Organisms in Cottage Cheese, J. Dairy Sci., 1991, vol 74, No. 9, pp. 2941-2945. Chen and Hotchkiss were conducted on cottage cheese with 2% fat that has an initial inoculated bacterial count of approximately 103 cfu / g, stored in sealed glass jars, with 35% up to 45% C02 (in air) in the upper space of the cells. jars, at a temperature of 7 ° C. Chen and Hotchkiss reported that carbonated samples showed no bacterial growth for 30 days, while cottage cheese packed without dissolved C02 104 times more units of colony formation; It was also reported that the carbonated samples had maintained a fresh appearance for 60 days. However, Chen and Hotchkiss did not measure the amount of CO2 dissolved in the cream or cottage cheese dressing, the pH of the product or, if the carbonated cottage cheese would be acceptable to consumers based on flavor. Additional research by Hotchkiss has suggested that cottage cheese can withstand the growth of putrefying microorganisms up to 60 days when C02 is added to a level of 300 ppm in cottage cheese and packaged in polystyrene tubes wrapped by shrinkage of high barrier film (or tubes). high barrier secured with a sheet / polyolefin laminate seal). "Commitment to Cottage Cheese, Dairy Foods," April 1996, p. 29. The process for obtaining such results is described as the injection of carbon dioxide directly into the cream dressing of the cottage cheese before the addition of the rennet and before packing; C02 is injected into the dressing in the processing line between the dressing tank (retention) and then mixed and packed. However, in such a process, when the carbon dioxide is added in the last stage before packing, the microbial action has already degraded the dairy product, up to a certain degree, between the time of pasteurization and packing. Furthermore, it is considered that the packaged product will necessarily undergo degassing of undissolved carbon dioxide introduced into the product and / or C02 that has not reached a stable state with the cottage cheese. This would provide a lack of acid flavors, affecting consumer acceptance. In addition, excess gas in the upper space of the containers could lead to a "bulging" effect in some packages, raising the problems of product quality. In addition, results on consumer acceptance of such products based on taste and appearance have not yet been shown. If CO2 imparts an acidic flavor to cottage cheese or if cottage cheese appears to be "bubbly" or effervescent, it will not be acceptable to consumers. It is equally likely that such effects occur when the amount of C02 exceeds a threshold level, either dissolved in the cottage cheese or present in the upper space of the container.

Although it is considered that these thresholds can be determined through experimentation, a process must still be developed that will maintain the specified levels of C02 in the product and in the upper space of the container. In addition, despite all previous efforts to increase the storage life of dairy products, a process has yet to be developed that will prepare dairy products that have increased storage life that are acceptable to the consumer with respect to taste and appearance.

OBJECTS OF THE INVENTION It is therefore an object of the present invention to provide means for increasing the storage life of dairy products without adversely affecting consumer acceptance with respect to taste and appearance. It is another object of this invention to provide a method for preparing dairy products with carbon dioxide which has increased the shelf life. It is even another object of this invention to provide a method for preparing dairy products that controls the growth of microorganisms, especially Gram-negative bacteria.

BRIEF DESCRIPTION OF THE INVENTION It is considered that those objects and advantages are achieved by the present invention. The present invention is directed to a method for preparing dairy products that have an increased storage life by incorporating carbon dioxide into such products. The present invention is adapted for consumer dairy products of a wide variety, including, but not limited to, milk, whey, yoghurt, sour cream, cottage cheese, ricotta cheese, other mild, semi-soft and hard cheeses, mixtures of ice cream and the like. The method of the present invention is contemplated for use within a standard dairy processing system, as well as independent processing. Average storage lives for several dairy products are listed below. Product Standard Storage Life Average Fluid Milk 17 days Cottage Cheese 22 days Ricotta Cheese 30 days Ice Cream Mix 18 days It is expected that the method of the present invention will at least double the shelf life for most dairy products. In general, in accordance with the method of the present invention, a fluid milk fraction of a milk feed is treated with carbon dioxide. "Dairy food" as used herein is intended to indicate the consumable milk during processing, including the liquid and solids contained therein, starting with fresh milk and ending with the product before packing. By "fresh milk fraction" is meant that portion of a dairy food that is in a fluid (i.e., liquid or semi-liquid) state. The fluid milk fraction can be any portion of the dairy food, up to and including 100 percent when the dairy food is totally fluid. More specifically, the present invention is directed to a method for preparing dairy products, before packing, which comprises contacting a fluid milk fraction of a milk feed with carbon dioxide, mixing the fluid milk and the carbon dioxide in a solution, and subjecting the solution to sufficient conditions to reach a "steady state" between the fraction of fluid milk and the dissolved carbon dioxide. By "steady state" is meant a concentration of carbon dioxide in fluid milk that is relatively stable to agitation and minor fluctuations in, for example, the temperature or pressure at which milk products may normally be subjected during mixing , packaging, storage, shipping and supply to consumers. The present invention may be conducted as part of a dairy processing plant or as an independent process.

The present invention can also be conducted optionally in a carbon dioxide environment, where the entire process, either within a dairy plant or the independent process, is conducted in a carbon dioxide environment or any or all of the Process equipment is covered with carbon dioxide.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects, features and advantages will be devised by those skilled in the art from the following description of the preferred embodiments and the accompanying drawings, in which: Fig. 1 is a process flow diagram of a modality of the invention within a dairy plant for a fully fluid dairy food; and Fig. 2 is a process flow diagram of an embodiment of the invention within a dairy plant for a dairy food, a portion of which is fluid and a portion thereof is solid; and Fig. 3 is a process flow diagram of a closed creamer quark processing system in a dairy plant operation; and Fig. 4 is a process flow diagram of an embodiment of the invention within an open tank cottage cheese processing system in a dairy plant operation.

DETAILED DESCRIPTION OF THE INVENTION The inventors of the present invention have realized that the most important factors in increasing the storage life of milk and milk products are providing means to inhibit bacterial growth as soon as possible in a dairy processing and the means to maintain inhibition during all stages of processing and during storage until the product reaches the consumer. The inventors have determined that this could be achieved by using carbon dioxide in the processing of milk and milk products, especially by incorporating carbon dioxide into milk and milk products. However, the problem was to develop a method that would provide the maximum level of bacterial inhibition, while also being suitable for commercial application. It is understood that in the processing of milk and milk products, food is subjected to various destabilizing forces including heat, pressure and high shear conditions throughout its processing. The methods of the prior art sought to take care of these forces by adding carbon dioxide in the last stage of processing, thereby minimizing the possibility of destabilization, followed by barrier packaging.

The present invention has discovered a means to add carbon dioxide to milk and milk products at the beginning of their processing. By the present method, carbon dioxide can be added at any time. It has been found that dissolving carbon dioxide in milk and milk products in one step, followed by a step that allows carbon dioxide to reach a "steady state" of equilibrium with the fluid portion of the milk or milk product results in a uniform and stable solution. In addition to the objects set forth herein, the use of the preferred method can avoid the need for modified atmosphere packaging (MAP) and may also result in the reduction and / or elimination of the use of preservatives. It is contemplated that since carbon dioxide is stably incorporated into the dairy product and provides for the inhibition of bacterial activity, high barrier packaging and natural and / or artificial preservatives may be unnecessary. This would provide cost savings in the preparation of such products. Although these steps can be done at any time, it is preferred that homogenization be done immediately after pasteurization, when bacterial growth is considered to be at its minimum level. This will advantageously provide maximum inhibition of bacterial growth. This is also convenient for the purpose of many dairy products that normally keep the fraction of fluid milk in a holding tank or equalizer after pasteurization or homogenization until final processing. Since carbon dioxide has already been added to the fraction of fluid milk, bacterial growth and enzymatic activity are advantageously inhibited during storage and further processing. It is contemplated that during the "steady state" stage, that the fluid milk fraction will be maintained under a pressurized carbon dioxide shell. In a preferred embodiment, all process equipment is kept under a pressurized carbon dioxide cover. Alternatively, the entire process system or, discrete segments thereof, may be contained in a carbon dioxide environment. The method of the present invention comprises the steps of contacting a fluid milk fraction of a dairy food with carbon dioxide, mixing the fluid milk fraction and carbon dioxide in a solution, and subjecting the solution to conditions sufficient to achieve a stable state between the fraction of fluid milk and the dissolved carbon dioxide. The fraction of fluid milk is treated by contacting the milk with carbon dioxide and, mixing to dissolve the carbon dioxide in the milk. The contact means may include, but is not limited to, injection, spraying and bubbling. The contact can be made in any of any suitable means that would be apparent to someone skilled in the art which includes the online process stream, the holding tank, process vessel and the like. The carbon dioxide is mixed and dissolved within the fluid milk fraction in a predetermined amount and in a manner consistent with the contacting step, including but not limited to, pressurized injection or spraying into a process stream or vessel, or bubbling through a holding tank. Other mixing means will be apparent to those skilled in the art. The rate of addition of carbon dioxide is contemplated to be between about 0.0373 kg to about 2.238 kg of CO2 per 373 kg of the fluid milk fraction. It is further contemplated that different dairy products may use different amounts of carbon dioxide, within this scale, in the process of the present invention. The preferred scales of the rate of addition of C02 by 373 kg of the fluid milk fraction are provided, as follows, for different milk products.

After the carbon dioxide has dissolved in the fluid milk fraction, the solution is placed under conditions sufficient to reach a "stable state" between the carbon dioxide and the fluid liquid milk phase. This can be achieved by transferring the milk solution and carbon dioxide to a container (eg, the holding tank or equalizer) and keeping it under suitable conditions and for a sufficient time to reach the steady state. As contemplated, the holding container is pressurized under a carbon dioxide cover. Those skilled in the art will recognize other suitable means and conditions with which the stable state of the solution is obtained. It is contemplated that the container will be maintained at a temperature of about 1.6 ° C to about 10 ° C and, preferably at about 2.7 ° C to about 7.2 ° C. The retention time is contemplated to be at least 0.5 hours approximately and, preferably, at least 1.0 hours. It is also contemplated that the cover of C02 will be pressurized to approximately 5.08 to 15.24 cm in the water column and, preferably, to approximately 7.62 to 12.7 cm in the water column. As contemplated, any single stage, or combination thereof, may be conducted under a cover of C02 or, the entire method may be within a C02 environment. In the aforementioned method it can be used for the preparation of any commercial dairy product. However, it will be appreciated that the processing parameters may differ slightly for the various dairy products, although the general method remains the same. Various embodiments of the present invention in dairy products are shown in the figures and are generally described below. However, it should be recognized that they are provided for illustrative purposes only and are not intended to be limited in any way. The specific features are shown in one or more of the drawings only for convenience, since each feature may be combined with other features in accordance with the invention. Those skilled in the art will recognize alternative embodiments and are intended to be included within the scope of the claims. A process for preparing a fluid dairy feed (eg, fluid milk or fluid milk product) is generally shown in Figure 1. As shown, the fluid milk is taken from the storage container 2 and is fed via line 4 to the pasteurizer / homogenizer 6. Upon leaving the pasteurizer / homogenizer 6, the C02 is injected by means of an injector 8 into the the line of fluid milk 10, where the C02 is mixed and dissolved inside the milk by the action of the injector in the process stream. The milk / C02 solution flows from the fluid milk line 10 into the holding tank 12, where the solution is maintained under suitable conditions to reach the steady state between the fluid milk and the dissolved C02. Upon reaching the steady state, the milk / C02 solution is transferred by means of a transfer line 16 to the packing system 18. During packing, the C02 can be added to the upper space of the milk container. Before and after entering the holding tank 12 and packing system 18, the C02 is added via lines 13 and 20, respectively, to purge and cover the tank and packing system. After packing, the milk containers are transferred for cold storage or shipping. In Fig. 2 a process for preparing a dairy product including dairy solids is generally shown. As shown, the liquid milk mixture is taken from the storage container 30 and is fed via line 32 to the pasteurizer / homogenizer 34. Upon leaving the pasteurizer / homogenizer 34, the C02 is injected by means of an injector 36 into the fluid milk mixture line 38, where the C02 is mixed and dissolved within the fluid milk mixture by the action of the injector in the process stream. The milk / C02 solution flows from the line 38 into the holding tank 42, where the solution is maintained under suitable conditions to reach the stable state between the fluid milk mixture and the dissolved C02. Upon reaching the steady state, the milk / C02 solution is transferred by means of a transfer line 44 to the mixer 44. Concurrently, the milk solids in the holding tank 50 are transferred by means of the transfer line 52 to the mixer 54. The milk solution / C02 is then mixed with the milk solids and then transferred via the outlet line 56 to the packing system 60. During packing, the CO 2 can be added to the upper space of the dairy product container. after entering the holding tank 42, the holding tank 50, the mixer 54 and the packing system 60, the C02 is added by means of the lines 40, 48, 46 and 58, respectively, to purge and cover each one of the two tanks, the mixer and the packing system After packing, the milk product containers are transferred for cold storage or shipping The preparation of the cottage cheese in a system Closed creamer, as shown in Fig. 3, follows those described above for a milk product with dairy solids. In a closed creamer system, the cream and formula 70 (ie, the cream dressing) are replaced by the liquid dairy mixture and rennet of cheese 90 by dairy solids Cream and rennet are mixed in creamer 94 which produces creamy cottage cheese Carbon dioxide is injected in line 78 after pasteurization and maintained for steady state 82 with the cream dressing The carbon dioxide is also added as a purge and cover for the holding tank 82, the skimmer 94 and the packing system 100 The present invention can also be conducted in an open tank system as shown for a cottage cheese system as in Fig. 4. In said process, the cream and the formula are supplied from the storage container 110 and fed through the line 112 to the pasteurizer / homogenizer 114. When leaving the pasteurizer / homogenizer 114, the C02 is injected by means of the injector 116 into the cream dressing line 118, where the CO 2 mixes and dissolves within the cream dressing by the action of the injector in the process stream. The cream / C02 solution flows from the cream dressing lines 118 to the holding tank 122, where the solution is maintained under suitable conditions to reach the steady state between the cream dressing and the dissolved C02. Upon reaching the stable line, the cream / C02 solution is transferred via line 124 to the cheese / skimmer tank 126 in which the rennet of the cheese is already prepared and stored. The rennet of the cheese and the cream / C02 solution are then mixed to produce the creamy cottage cheese which is transferred by way of the outlet line 130 to the packing system 134. During packing, the C02 can be added to the upper space of the container. of cottage cheese. Before and after entering the holding tank 122, the tank / creamer 126 and the packing system 134, the C02 is added by means of lines 120, 128 and 132, respectively, to purge and cover the tank, tank / skimmer and packaging system. After packing, the cottage cheese containers are transferred for cold storage or shipping.

The method of the present invention is further illustrated by the following examples. However, it is recognized that these examples are not intended to limit the scope of the present invention in any way.

Examples Cottage cheese production The cottage cheese was prepared by mixing a pasteurized and homogenized cream dressing with a cheese rennet that has been produced from pasteurized skim milk. A typical mixing ratio is from about 40% to about 45% cream dressing with about 55% to about 60% cheese rennet. Cottage cheese products are classified mainly by rennet size and percent milk fat. The regular small cottage cheese commonly has about 4% milk fat, a low fat product has about 1% to about 2% milk fat and the fat free product has less than about 1% milk fat. In a closed skimmer process, the creamy cottage cheese is produced by starting with approximately 7460 kg of cream and formula dressing. The cream dressing is pumped through an HTST pasteurizer (high temperature, short time) and then homogenized. The carbon dioxide is sprayed at a specific rate, during the course of about 55 to about 60 minutes, into the cream dressing as it is pumped into the storage vessel purged with C02. The upper pressure of the carbon dioxide is maintained at about 7.62 to about 10.16 cm in the water column. The cream dressing sprayed with carbon dioxide is kept in the storage container overnight. The next day, 932.5 kg of the cream dressing was pumped into a skimmer purged with C02 and mixed with 1454.7 kg of cheese rennet for approximately 25 minutes. The resulting cottage cheese is then analyzed for the final fat content and pumped to the final fill lines. The cottage cheese is packed in HDPE (high density polyethylene) tubes with an internal metallic mylar seal and refrigerated at approximately 4.4 ° C.

Example 1 Cottage cheese was prepared as described above, with carbon dioxide injected at 0.746 kg and 1492 kg. The C02 for 373 kg of cream dressing, for regular and low fat varieties. Table 1 shows the processing parameters for each test, along with their results. The flavor and appearance of the final product were tested one or two days after packing, by measuring the pH of the product, the flavor qualities ("sensitivity") and by observing the internal seal of the package for the bulge. The pH of the product was considered normal as long as it was between approximately 4.7 and 6. The sensitive determination was made based on the flavor changes with and without C02. When no change in taste was detected, a "clean" notation was listed. The internal package seals were inspected for the effects; and when they were not affected, an "intact" annotation was listed. The upper space of carbon dioxide was also measured. The storage life for the control samples was shown to be up to approximately 21 days, while the storage life for the cottage cheese sprayed with 1492 kg of C02 per 373 kg of cream was at least 45 days (the end point of the proof).

Table 1 Example 2 The cottage cheese was prepared, as before, although without the purge and cover of C02. The injection velocity of carbon dioxide was 0 559 kg C02 per 373 kg of cream dressing. The results were measured on a microbiological basis. The controls showed positive microbial activity at approximately 23 to 24 days, while the treated product remained free. of microbial activity (ie, negative results) for the full 47-day course. The results are shown in Table 2 * The test indicates that the average result of 3 sample tubes (each obtained from the Start, Middle and End of the Lot) Example 3 The cottage cheese was prepared, as before, and additionally with the filling hopper subjected to purge and covered with carbon dioxide. Carbon dioxide was also injected at speeds of 0.746 and 1.492 kg C02 per 373 kg of cream dressing. The results are shown in Table 3, characterized in a manner similar to that shown in Example 1 Table 3

Claims (10)

1. A method for preparing a packaged dairy product having increased storage life, comprising the steps of: (a) contacting the fluid milk fraction of a dairy food with carbon dioxide, (b) mixing the fluid milk fraction and carbon dioxide in a solution, and (c) subjecting the solution to conditions sufficient to reach the steady state between the fluid milk fraction and carbon dioxide, and wherein steps (a) - (c) are conducted before the packing of the dairy food.

The method of claim 1, wherein at least one of steps (a) - (c) is conducted under a cover of carbon dioxide.

The method of claim 2, wherein at least one of steps (a) - (c) includes a purge of carbon dioxide.

The method of claim 1, wherein each of steps (a) - (c) are conducted under a cover of carbon dioxide.

The method of claim 4, wherein each of steps (a) - (c) includes a purge of carbon dioxide.

6. The method of claim 1, wherein steps (a) - (c) are within a dairy processing system, which includes pasteurization and homogenization, and wherein carbon dioxide is contacted and mixed with the fraction of fluid milk using an injector or inline sprayer immediately after pasteurization and homogenization.

The method of claim 2, wherein the steady-state step (c) is conducted at approximately 1.6-10 ° C for at least 0.5 hours inside a holding tank or equalization.

The method of claim 2, wherein the carbon dioxide is mixed with the fluid milk fraction at a scale of approximately 0.037 kg C02 / 373 kg fluid milk fraction.

The method of claim 2, wherein the carbon dioxide cover is maintained under a normal positive pressure of about 7.62-12.7 cm in the water column.

10. A method for preparing dairy products having a refrigerated storage life of from about 45 days to about 60 days and pure non-acid taste, comprising the steps of: (a) pasteurizing and homogenizing a dairy food and immediately thereafter, (b) ) contact a milk fraction of the milk feed with carbon dioxide, and (c) mix the fluid milk fraction and carbon dioxide in a solution, and (d) subject the solution, under a cover of carbon dioxide , to conditions sufficient to reach the stable state between the fraction of fluid milk and carbon dioxide.