RU2438337C1 - Curd freezing method - Google Patents

Abstract

FIELD: food industry.

SUBSTANCE: invention relates to the field of food industry, in particular, to milk products cooling technology using a cooling agent. The method envisages usage of a cooling agent represented by liquid nitrogen to freeze curd. Curd freezing is performed in a consumer container in one stage, the curd layer height in the container is no more than 40 mm. Liquid nitrogen is added in an amount of 30.0-60.0% of the product weight taking into account the curd fat content, the container is sealed and stored.

EFFECT: invention allows to freeze curd in one stage.

3 cl, 2 tbl, 8 ex,1 ex

Description

The invention relates to the food industry, namely to the refrigeration technology of dairy products using a refrigerant, and can be used, in particular, when storing cottage cheese.

A known method of canning mare’s milk with cold for the production of koumiss, including freezing mare’s milk in bags of polymer and combined materials with a volume of 1000 ± 50 ml in low-temperature chambers with a temperature regime of -22 to -32 ° C for 1.5-2 hours, and followed by storage for up to 6 months in freezers and glaciers with a temperature regime of -15 ° C (RF patent 2272415, A23C 3/04, 2005).

The disadvantages of the method of canning milk include the fact that during slow freezing in water ice crystals form, in the liquid non-frozen part, the concentration of colloidal particles and electrolytes increases. The concentration of electrolytes in a colloidal solution can so increase that it will lead to a decrease in the charges of protein molecules and cause their dehydration, denaturation, and then aggregation of denatured proteins. Thawed milk with a partially denatured protein is not restored to a colloidal solution.

In addition, during slow freezing, mare's milk is stratified into layers: the upper layer is softer and enriched with fat, the peripheral layer is transparent and consists mainly of ice crystals, the central one is white, with a high concentration of proteins, sugar, ash, and the lower one with a significant protein content . After defrosting, such milk sours much worse or separate flakes form in it. Slow freezing leads to a decrease in the pH of the residual liquid, to obtain larger ice crystals, to further destabilize casein and the shells of fat globules, as well as to crystallize lactose.

There is a method of freezing food products with liquid nitrogen transported on a conveyor belt in a tunnel freezer, including blowing products with vapor of evaporated liquid nitrogen in a pre-cooling zone, subsequent irrigation of the product with liquid nitrogen in the freezing zone and passage of frozen products through the temperature equalization zone. The duration of the stage of blowing products with vaporized nitrogen is chosen on the basis of freezing 35-45% of the volume of the product, the remaining product is frozen at the stage of irrigation with liquid nitrogen (RF patent 2000126187 A, F25D 3/10, F25D 13/06, 2003).

The disadvantage of the above method of freezing in relation to cottage cheese is its duration, because the process of low-temperature processing of the product according to this method is carried out in three stages.

In addition, the implementation of the above freezing method leads to a significant increase in the cost of the product due to the high consumption of liquid nitrogen due to the fact that the product is frozen in bulk form by blocks in the tunnel volume of the freezer, where liquid nitrogen is fed, which is scattered through the tunnel volume. As is known from the literature (O. Anokhina, B. N. Semenov. “Scientific basis and technological aspects of the refrigeration technology of fish products using nitrogen. Kaliningrad, 2009, p. 32), the flow of liquid nitrogen for freezing the product in the freezer is 1.2-1.5 kg per 1 kg of product, which significantly increases the cost of cottage cheese. At the end of the shelf life of frozen cottage cheese, the blocks of cottage cheese are defrosted and packaged before shipping to the consumer. This is a long and time-consuming process, which is inevitably accompanied by microbiological contamination of the product, which reduces the time of its implementation in the distribution network. The total loss of the product, taking into account the operations of defrosting and packaging increase.

A device for freezing pasta-minced food products (SU No. 1655436 A1, publ. 06/15/1991), adopted for the closest analogue. The method of freezing food products, including cottage cheese, when using this device is carried out in two stages: at the first stage, using liquid nitrogen, the product is frozen only in the central part of the container, after which, at the second stage, the product is frozen at the walls of the container, directly in the refrigerator.

The disadvantages of the described method of freezing cottage cheese include the lowered quality characteristics of cottage cheese:

firstly, due to the formation of ice crystals of different sizes in the curd, due to the two-stage method of freezing (cryogenic freezing of the center of the product, followed by freezing of the product in the refrigerator);

secondly, due to the inevitable microbiological contamination of cottage cheese during subsequent defrosting and packaging, the more so that the covers remaining in the cottage cheese during nitrogen freezing will create additional unsanitary conditions in which the defrosting process will take place;

thirdly, when freezing with liquid nitrogen, the optimal dose of liquid nitrogen is not determined taking into account the fat content of cottage cheese;

fourthly, they freeze large volumes of the product, which increases the duration of the low-temperature processing process.

These shortcomings will adversely affect the quality of cottage cheese, reduce the time for its implementation in the distribution network, in addition, the total loss of the product during defrosting and packaging operations will increase.

The invention solves the problem of preserving the quality of cottage cheese, reducing the freezing process and reducing the cost of frozen cottage cheese by freezing pre-packaged cottage cheese and using the optimal amount of liquid nitrogen, taking into account the fat content of the cottage cheese and the height of the cottage cheese layer in the container. Freezing the packaged cottage cheese eliminates the defrosting and packing of the cottage cheese before its sale, which reduces the total loss of the product.

To obtain the desired technical result in the known method of freezing cottage cheese, including the use of liquid nitrogen, it is proposed to pre-pack freshly prepared cottage cheese in portioned consumer containers, and the height of the layer of cottage cheese in the container is proposed to choose no more than 40 mm, add liquid nitrogen in an amount of 30.0-60 , 0% by weight of the product, taking into account the fat content of the cottage cheese, after which the container is sealed and stored. It is suggested to choose the maximum amount of liquid nitrogen for nonfat cottage cheese, and the minimum for cottage cheese with a fat content of 23%. It is proposed to store frozen cottage cheese at a temperature of minus 18 ° C.

The proposed method of freezing cottage cheese using liquid nitrogen compared with the combined freezing described in the closest analogue has several advantages. Only environmentally loyal refrigerant - liquid nitrogen is used. The chemical inertness of nitrogen excludes reactions with the product. Intensifies the speed of freezing several times. Guaranteed preservation of the quality of cottage cheese during long-term refrigerated storage and sale. After defrosting, cottage cheese completely restores its original organoleptic properties, because under the influence of only liquid nitrogen, smaller ice crystals form in the product and the process of syneresis slows down. If ice formation occurs quickly in both inter-micellar and intramuscular spaces with the complete transition of free water to ice, rapid freezing and storage at minus 18 ° C reduces the effect of concentrated salts on the protein. During slow freezing, fat globules under pressure of large ice crystals are deformed, their shell is damaged, as a result of which, after thawing, the balls are destabilized and merged.

Cottage cheese, frozen with liquid nitrogen according to the proposed method, is stored 1.5-2 times longer than frozen in a combined way at a storage temperature of minus 18 ° C. At the same time, the organoleptic properties are stabilized, the microbiological and physico-chemical characteristics of cottage cheese do not deteriorate.

In the technology for the production of cottage cheese from dairy raw materials in accordance with GOST R 52096-2003, certain indicators of the mass fraction of fat are established (except for "from natural milk"):

- fat-free not more than 1.8%;

- non-greasy 2.0%; 3.0%; 3.8%;

- classic 4.0%; 5.0%; 7.0%; 9.0%; 12.0%; 15.0%; 18.0%;

- fatty 19.0%; 20.0%; 23.0%.

The drawing attached to the description shows the dependence of the flow of liquid nitrogen, necessary for freezing pre-packaged cottage cheese with a layer height of 40 mm, on the fat content of cottage cheese. It has been experimentally established that there is a definite relationship between the fat content of cottage cheese and the optimal dose of liquid nitrogen necessary for freezing it, and the higher the fat content of cottage cheese, the lower the required dose of liquid nitrogen. This is due to the different moisture content in the curd with its different fat content. In accordance with GOST R 52096-2003, certain indicators of the mass fraction of moisture of cottage cheese depending on fat content (not more) are established:

- low fat 80%

- non-greasy 76%

- classic 75%, 73%, 70%

- fatty 65%, 60%

The experimental data confirm that the dependence of the flow of liquid nitrogen on the fat content of the cottage cheese shown in the diagram is true only when the layer thickness of the packaged cottage cheese is not more than 40 mm. An increase in the thickness of the curd layer increases the consumption of liquid nitrogen, which ultimately leads to an increase in the cost of the product. The packaging used in the distribution network, which is usually used for packaging cottage cheese, has a size of 137 × 137 × 45 mm (used in the research) or a diameter of 144 mm and a height of 40 mm and therefore the proposed size of the cottage cheese layer usually does not exceed 40 mm, which corresponds to a consumer packaging of 200 g. Using the proposed chart, it is possible in practice to easily determine the necessary optimal flow rate of liquid nitrogen to freeze a given portion of cottage cheese of a certain fat content and prevent nitrogen overruns, and therefore not increase the cost of the product.

In the study of this method, refrigerated storage of cottage cheese was carried out at minus 18 ° C in accordance with TU 9222-180-00419785-04, i.e. at the recommended storage temperature for this type of product. Storage at lower temperatures leads to an increase in energy consumption to maintain lower temperature conditions and is reflected in the cost.

Specific Examples of the Method

Example 1. For freezing, freshly prepared fat-free cottage cheese (fat content 0%) was used. Cottage cheese was packaged in portions of 200 g per container. The height of the layer of cottage cheese in the container is 40 mm. The dose of liquid nitrogen was taken from the calculation of 60% by weight of the product, which amounted to 120 g. For a uniform irrigation of the surface of the curd with nitrogen, a spray nozzle was used that was commensurate with the selected container. After irrigation of the cottage cheese with liquid nitrogen, the container was hermetically sealed. After that, a batch of frozen cottage cheese was sent for storage. Packaged cottage cheese was stored at a temperature of minus 18 ° C.

After 21 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. Organoleptic indicators: crumbly consistency, decay of curd grain; color from white to light cream, uniform throughout the mass; the smell and taste are clean, without extraneous smacks. Titratable acidity was 194 ° T. Recommended shelf life of skimmed cottage cheese is 21 months. Cottage cheese can be eaten without preliminary processing to refine it, i.e. improvement of organoleptic indicators.

After 22 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. It was removed from storage due to inconsistency with organoleptic indicators: the consistency is dry, crumbly, the breakdown of curd grain; the color acquired a creamy hue throughout the mass; smell and taste are mild, not clean. Titratable acidity was 196 ° T.

Example 2. The sequence of operations is similar to that described in example 1. Freshly cooked cottage cheese was frozen (fat content 9%). Liquid nitrogen was taken in an amount of 100 g based on 50% by weight of the product.

After 19 months of storage, the cottage cheese had microbiological indicators at the level of the requirements of the standard. Organoleptic indicators: crumbly consistency, decay of curd grain; color from white to light cream, uniform throughout the mass; the smell and taste are clean, without extraneous odors and tastes. Titratable acidity was 189 ° T. The recommended shelf life of classic cottage cheese, frozen by the proposed method, 21 months. Cottage cheese can be eaten without preliminary processing to refine it, i.e. there is no need to improve organoleptic indicators.

After 22 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. It was removed from storage due to inconsistency with organoleptic indicators: crumbly consistency, decay of curd grain; the color acquired a light yellowish tint, uneven throughout the mass; the smell and taste are mild, not clean with different flavors. Titratable acidity was 193 ° T.

Example 3. The sequence of operations is similar to that described in example 1. Freshly cooked cottage cheese was frozen (fat content 18%). Liquid nitrogen was taken in an amount of 80 g based on 40% by weight of the product.

After 15 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. Organoleptic indicators: the texture is slightly smeared; color - blotches of yellow shades, uneven throughout the mass; the smell and taste are clean, sour milk without various flavors. Titratable acidity was 186 ° T. The recommended shelf life of cottage cheese, frozen by the proposed method, 17 months. Cottage cheese can be eaten without preliminary processing to refine it, i.e. improve organoleptic characteristics.

After 18 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. It was removed from storage due to inconsistency with organoleptic indicators: the texture is slightly smeared; color - sprinkling of yellow shades, uneven throughout the mass; the smell and taste are not clean, the taste of the packaging material. Titratable acidity was 190 ° T.

Example 4. The sequence of operations is similar to that described in example 1. Freshly cooked cottage cheese was frozen (fat content 23%). Liquid nitrogen was taken in an amount of 60 g based on 30% by weight of the product.

After 11 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. Organoleptic characteristics: consistency spreading on the surface; the color of yellow shades, uneven throughout the mass; the smell and taste of sour milk. Titratable acidity was 178 ° T. The recommended shelf life of cottage cheese, frozen by the proposed method, 13 months. Cottage cheese can be eaten without preliminary processing to refine it, i.e. improve organoleptic characteristics.

After 14 months of storage, the cottage cheese had microbiological indicators at the level of standard requirements. It was removed from storage due to inconsistency with organoleptic indicators: the texture spreading on the surface, loose inside; the color of yellow shades, uneven throughout the mass; smell and taste are musty, oxidized. Titratable acidity was 180 ° T.

Example 5. To study the flow of liquid nitrogen to freeze the curd, freshly prepared fat-free curd was used (fat content 0%). Cottage cheese was packaged in portions of 200 g per container. The height of the layer of cottage cheese in a container is 40 mm. The dose of liquid nitrogen was taken from the calculation of 70% by weight of the product, which amounted to 140 g. For uniform irrigation of the surface of the curd with nitrogen, a spray nozzle was used, which was proportional to the selected container. There was freezing of the product throughout the volume, but the consumption of liquid nitrogen was significant, which affected the cost of the product - it increased.

Example 6. Analogously to example 5, experiments were carried out to freeze fat cottage cheese (fat content 23%). A dose of liquid nitrogen was used at the rate of 20% by weight of the product. Non-freezing of the lower layers of cottage cheese in the container was observed. It is rational for freezing fatty cottage cheese to take a dose of nitrogen at least 30% by weight of the product.

Example 7. For freezing, freshly prepared skimmed cottage cheese (fat content 0%) was used. Cottage cheese was packaged in portions of 200 g per container. The height of the layer of cottage cheese in a container is 50 mm. The dose of liquid nitrogen was taken from the calculation of 60% by weight of the product, which amounted to 120 g. For a uniform irrigation of the surface of the curd with nitrogen, a spray nozzle was used that was commensurate with the selected container. After irrigation of the cottage cheese with liquid nitrogen, non-freezing of the cottage cheese layer was observed. To freeze cottage cheese with a fat content of 0% by weight of 200 g in a consumer container with a cottage cheese layer height of 50 mm, the flow rate of liquid nitrogen amounted to 80% by weight of the product.

Example 8. The sequence of operations is similar to that described in example 7. Freshly prepared cottage cheese was frozen (fat content 23%). Liquid nitrogen was taken in an amount of 60 g based on 30% by weight of the product. After irrigation of the cottage cheese with liquid nitrogen, non-freezing of the cottage cheese layer was observed. For freezing cottage cheese with a fat content of 23% by weight of 200 g in a consumer container with a layer height of cottage cheese of 50 mm, the flow rate of liquid nitrogen was 40% by weight of the product.

Based on the above examples of the implementation of the claimed invention in laboratory conditions, we can state compliance with its criterion of "industrial applicability".

The proposed method of freezing packaged cottage cheese with liquid nitrogen in comparison with the method described in the closest analogue has several advantages:

1. Freezing of the proposed method allows you to save the quality of cottage cheese, because there is no defrosting operation during which the curd is seeded, which reduces the shelf life and extends the sale of packaged curd in retail chains.

2. Reduction of the stages of the freezing process and its duration by several times.

3. Prolongation of the shelf life of cottage cheese frozen with liquid nitrogen at a storage temperature of minus 18 ° C by 1.5-2 times in comparison with the closest analogue.

4. The reduction in the cost of frozen cottage cheese is a consequence of the summation of the reduction in material costs of the following components:

- a decrease in the flow of liquid nitrogen (without taking into account the fat content of the cottage cheese, the used mass of nitrogen is 60% of the mass of the product) was at least 60% (a decrease in the cost of cottage cheese by at least 15%);

- a decrease in the mass loss of cottage cheese when packing freshly prepared cottage cheese per 1 ton of product in consumer packaging is an average of 5.5 kg, and when packing defrosted cottage cheese blocks - 7.5 kg per 1 ton, which is associated with the features of technological equipment;

- the exclusion of product mass losses associated with defrosting (moisture loss that reduces its quality);

- optimization of the added dose of liquid nitrogen, taking into account the fat content of cottage cheese, which leads to a noticeable decrease in the consumption of liquid nitrogen, starting with a fat content of 4% (see the attached chart), and with a fat content of cottage cheese of 23%, a decrease in the consumption of liquid nitrogen reaches a minimum of 25%, which reduces the cost of fatty frozen cottage cheese is about 14%;

- optimization of the added dose of liquid nitrogen, taking into account the height of the layer, which should not exceed 40 mm, which, as shown by studies, significantly affects the flow of liquid nitrogen: when exceeding the height of the curd layer, for example, at a height equal to 50 mm, incomplete freezing is observed layer of cottage cheese, which necessitates an increase in the dose of liquid nitrogen, and therefore leads to an increase in the cost of the product.

Thus, the maximum reduction in the cost of frozen fat-free cottage cheese in comparison with the closest analogue is about 15% for fat-free cottage cheese and 12% for fat cottage cheese.

Table 1 shows the duration of storage of frozen cottage cheese.

Table 1 Duration of storage, months Moisture content, % Mass fraction of protein,% Acidity, ° T Curd fat content 0% 6 79 eighteen 183 10 77 eighteen 186 fourteen 77 eighteen 190 eighteen 75 eighteen 193 22 74 eighteen 196 Curd fat content 9% 6 72 16 179 10 71 16 184 fourteen 70 16 186 eighteen 70 16 189 22 68 16 193 Curd fat content 18% 6 69 fourteen 180 9 69 fourteen 182 fourteen 67 fourteen 186 eighteen 65 fourteen 190 Curd fat content 23% 6 60 fourteen 173 9 58 fourteen 178 fourteen 58 fourteen 180

In the process of refrigerated storage in all studied samples of cottage cheese of various fat content, frozen with liquid nitrogen by the proposed method, the stability of physico-chemical and microbiological parameters was observed.

The indicator titratable acidity is one of the criteria for assessing the quality of cottage cheese. In the studied batches of cottage cheese, this indicator throughout the entire period of low-temperature storage did not exceed the norms regulated by regulatory documentation.

A slight change in the “Humidity” indicator was noted, this is due to the fact that as a result of rapid freezing, smaller ice crystals are formed, the structure of casein is not disturbed, and the process of syneresis is slowed down.

When freezing cottage cheese in a combined way (as in the closest analogue), the duration of its storage is reduced by 1.5-2 times in comparison with cottage cheese frozen with cryogen liquid nitrogen. Already at the 12th month of storage, a decrease in its quality is observed. The organoleptic characteristics of the product worsen, the process of syneresis is observed. For further implementation, the product requires refinement. Defrosting the cottage cheese frozen in a combined way before the packing operation can lead to repeated microbiological seeding of the product and shorten the time for its sale in retail chains.

Table 2 shows the microbiological indicators of cottage cheese.

table 2 Continue
storage capacity, months BGKP (coliforms), g are not allowed in 0.01 g Pathogenic, including Salmonella, not allowed in 25.0 g Staphylococci S.aureus, 0.1 g Mold, cfu / g not more than 50 Yeast, CFU / g not more than 100 Curd fat content 0% 6 Not found Less than 50 Less than 100 10 fourteen eighteen 22 Curd fat content 9% 6 Not found Less than 50 Less than 100 10 fourteen eighteen 22 Curd fat content 18% 6 Not found Less than 50 Less than 100 9 fourteen eighteen Curd fat content 23% 6 Not found Less than 50 Less than 100 9 fourteen

Microbiological studies have confirmed the safety of frozen cottage cheese for consumption. Throughout the entire shelf life, microbiological indicators did not exceed the norms established by regulatory documents.

Claims (3)

1. A method of freezing cottage cheese, including the use of liquid nitrogen, characterized in that the freshly prepared cottage cheese is pre-packaged in a portioned consumer container, the cottage cheese layer height in the container being not more than 40 mm, liquid nitrogen is added in an amount of 30.0-60.0% by weight of the product, taking into account the fat content of cottage cheese, the container is sealed and stored. 2. The method of freezing cottage cheese according to claim 1, characterized in that the amount of liquid nitrogen is selected as maximum for low-fat cottage cheese, and the minimum for fatty. 3. The method of freezing cottage cheese according to claim 1, characterized in that the storage of frozen cottage cheese is carried out at a temperature of -18 ° C.