Quark-flavor active probiotic ice cream and preparation method thereof

Abstract

The preparation method comprises the following steps: performing filtration, milk standardization, sterilization, fermentation and whey removal on raw milk to obtain quark curds and whey; preparing the quark curds into quark freeze-dried powder; mixing whey with activated carbon and a sweetening agent to obtain mixed slurry; mixing the quark freeze-dried powder, the mixed slurry, prebiotics and emulsifying salt, and then adding skimmed milk powder, white granulated sugar, malt syrup, anhydrous cream, a compound stabilizer and single cream to obtain mixed feed liquid; the mixed material liquid is subjected to primary sterilization, homogenization, secondary fermentation, demulsification, secondary sterilization, aging, low-temperature plasma treatment, congelation and freezing treatment, and the feed additive is obtained. The ice cream prepared by the preparation method disclosed by the invention has the advantages of being soft, soft and cream-like in mouth feel, and also retains beneficial metabolites of the probiotics and high viable count.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and particularly relates to quark-flavored active probiotic ice cream and a preparation method thereof. Background Art

[0002] Ice cream is a frozen dessert, which is a volume-expanded frozen food made from drinking water, milk, milk powder, cream (or vegetable oil), sugar and other ingredients, with appropriate amounts of food additives, and through mixing, sterilization, homogenization, aging, freezing, hardening and other processes. Ice cream has a delicate and smooth taste and a variety of flavors, and is deeply loved by consumers. However, the flavors of ice cream on the market are relatively single, and there are few innovative flavors. I have never seen cheese-flavored ice cream.

[0003] Cheese, also known as cottage cheese, is a fermented milk product with a unique flavor. It basically eliminates a large amount of water in milk and retains the essence of it with extremely high nutritional value. There are many types of cheese, and the cheese made according to different production processes and additives has different tastes and flavors. Quark cheese, as a typical cheese in Central Europe, is not only high in protein, but also low in fat, sugar, and salt, with a delicate texture and a creamy taste. Quark cheese has a strong aroma and tastes slightly sourer than cream cheese, but is more refreshing. Quark cheese is made from high-quality fresh milk. It is fermented and coagulated under the action of lactic acid bacteria and probiotic strains, and the whey is discharged by physical methods to obtain unripe fresh cheese. This cheese is rich in protein, calcium, and multiple vitamins, especially vitamin A and carotene. In addition, quark cheese is also rich in nutrients such as probiotics and immunoglobulins, which are beneficial to human health.

[0004] Therefore, by combining ice cream and cheese, a unique and delicious food experience is created. The best production method and process are explored to achieve a combination of the cool and dense taste of ice cream and the rich and mellow flavor of cheese, bringing a rich layered taste to the taste buds. Summary of the invention

[0005] The main technical problem solved by the present invention is to provide a quark-flavored active probiotic ice cream and a preparation method thereof. The ice cream prepared by the present invention has a dense, soft and creamy mouthfeel, retains the advantages of beneficial metabolites and a high number of viable bacteria of probiotics, is cold-resistant, and can still maintain good resistance to harmful microorganisms such as yeast, mold and coliform group when stored at low temperatures, thereby improving product safety and / or extending its shelf life.

[0006] The present invention is implemented by the following technical solutions:

[0007] A method for preparing quark-flavored active probiotic ice cream comprises the following steps:

[0008] (1) filtering, milk standardization, sterilization, fermentation, and whey removal of raw milk to obtain quark curd and whey;

[0009] (2) subjecting the quark curd to a vacuum freeze-drying treatment, and then to a powdering and sieving treatment to obtain quark freeze-dried powder; mixing the whey with activated carbon and a sweetener, stirring them evenly, and then boiling and filtering the mixture to obtain a mixed slurry;

[0010] (3) Mix the quark freeze-dried powder, mixed slurry, prebiotics, and emulsified salt, stir evenly, heat to 50-60° C., then add skim milk powder, white sugar, maltose syrup, anhydrous butter, compound stabilizer, and cream, stir while adding, and obtain a mixed liquid after the raw materials are mixed;

[0011] (4) The mixed liquid is subjected to primary sterilization, homogenization, secondary fermentation, demulsification, secondary sterilization, aging, low-temperature plasma treatment, freezing, and freezing treatment to obtain the product.

[0012] Furthermore, in step (1), the raw milk is filtered, milk standardized, sterilized, fermented, and whey removed in the following steps:

[0013] Filtration: Raw milk is filtered through a 100-mesh single or double filter after passing the test;

[0014] Milk standardization: Standardization of cow milk by using a centrifugal separator to remove fat from the milk and adjust it to skim milk with a fat content of less than 0.5%;

[0015] Sterilization: Sterilize skim milk at 80°C for 25 seconds;

[0016] Fermentation: Cool the sterilized skim milk to 27°C, add the composite starter and rennet, the addition amount of the composite starter is 1-1.2g / 50L skim milk, and the addition amount of rennet is 15-20g / 1000L skim milk; keep warm and ferment for 12-14h at 27°C;

[0017] Whey removal: The fermented base material is dehumidified using a whey separator. The feed rate is controlled to 800L / h, the feed pressure is controlled to 3.5bar, and the centrifuge speed is 8500rpm. The base material is concentrated 3 times to significantly increase the protein content; quark curd and whey are obtained.

[0018] Furthermore, the composite fermentation agent is composed of Lactococcus cremoris, Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. mesenteroides and Lactococcus lactis subsp. lactis (diacetyl type) in a ratio of 2:3:2:1 in terms of viable cell count.

[0019] Furthermore, in step (2), the freeze-drying treatment is performed by placing the freeze-drying plate into a vacuum freeze-drying machine, wherein the freezing temperature is -40°C, the vacuum degree is 100-200 Pa, the partition temperature is 45°C, and the freeze-drying is stopped when the moisture content is lower than 5%.

[0020] The vacuum freeze-drying process further includes: applying microwave technology to perform auxiliary heating treatment on the quark curd;

[0021] Monitoring the moisture content of the quark curd, and stopping the vacuum freeze drying process when the moisture content is less than 5%;

[0022] Among them, microwave technology is used to perform auxiliary heating treatment on quark curd, including:

[0023] A microwave generator is arranged in the drying chamber of the vacuum freeze dryer, and the microwave generator periodically emits microwaves during the drying process to accelerate the vibration and migration of water molecules;

[0024] Controlling the frequency and power of the microwaves to ensure uniform heating of the quark curd;

[0025] Optimize the energy efficiency and time of vacuum freeze drying by adjusting the cycle and duration of microwave emission;

[0026] Based on the effect of microwave-assisted heating treatment, the operating parameters of the vacuum freeze dryer are dynamically adjusted to further shorten the drying time;

[0027] During the microwave-assisted heating process, the temperature distribution of quark curd is monitored in real time to ensure temperature uniformity;

[0028] When uneven temperature distribution is detected, the emission angle and position of the microwave generator are adjusted to improve heating uniformity;

[0029] By combining auxiliary heating with microwave technology, the vacuum freeze-drying time can be significantly shortened.

[0030] Furthermore, in step (2), the slurry cooking temperature is 103-115° C. and the cooking time is 3-10 min.

[0031] Furthermore, in step (2), 100-200 g of activated carbon and 50-100 g of sweetener are added per liter of whey;

[0032] The sweetener is selected from at least one of white sugar, sucrose, fructose, fructose syrup, maltose, maltose syrup, glucose, glucose syrup, lactose, honey, sugar alcohol, sodium cyclamate, aspartame, sucralose, acesulfame potassium and neotame.

[0033] Furthermore, in parts by weight, the raw milk in step (1) is 680-800 parts, the prebiotics in step (3) are 8-18 parts, the emulsifying salt is 0.5-1.5 parts, the skimmed milk powder is 20-50 parts, the white sugar is 60-100 parts, the maltose syrup is 30-50 parts, the anhydrous butter is 20-50 parts, the compound stabilizer is 5-10 parts, and the light cream is 80-120 parts.

[0034] Furthermore, the composite stabilizer in step (3) is composed of the following raw materials in parts by weight: 15-20 parts of mono- and di-glycerol fatty acid esters, 10-20 parts of guar gum, 18-24 parts of tara gum, 22-28 parts of sodium carboxymethyl cellulose, 2-4 parts of sodium polyacrylate and 10-15 parts of pullulan.

[0035] In compound stabilizers, mono- and di-glycerol fatty acid esters can work synergistically with other thickeners to reduce the aggregation of fat particles, enhance the emulsification effect of the formula, and ensure that the product maintains a uniform taste during freezing and storage. The combination of taro gum with guar gum and sodium carboxymethyl cellulose can form a complementary effect, further enhancing the freezing stability, and it has good ductility, can maintain the softness and toughness of the formula at low temperatures, and effectively prevent ice crystals from damaging the texture and probiotics. Although the amount of sodium polyacrylate is small, it plays an important auxiliary role in compounding. It can work synergistically with guar gum, taro gum and CMC to form a more solid network structure, further reduce the formation of ice crystals, and ensure the texture stability of the product. The film-forming properties of pullulan can form a more effective protective layer together with mono- and di-glycerol fatty acid esters, especially for the protection of probiotics. This protective film can effectively prevent mechanical damage during freezing and storage and improve the survival rate of probiotics.

[0036] Furthermore, the specific operations of primary sterilization, homogenization, secondary fermentation, demulsification, secondary sterilization, aging, low-temperature plasma treatment, freezing, and freezing treatment in step (4) are as follows:

[0037] The first sterilization is ultra-high temperature instantaneous sterilization, and the sterilization temperature is 119-123℃;

[0038] Homogenization: Two-stage homogenization is adopted. The mixed liquid after the primary sterilization is cooled to 65℃~70℃ for two-stage high-pressure homogenization. The homogenization pressure of the first stage is 12MPa~20MPa, and the second stage is 2MPa~6MPa.

[0039] The secondary fermentation is specifically as follows: the mixed liquid after homogenization is cooled to 43° C., lactic acid bacteria are inoculated into the liquid, added into the base material at an addition amount of 0.005%, and stirred sufficiently to make the lactic acid bacteria evenly dispersed, the fermentation temperature is 43° C., the fermentation is kept warm for 5 hours, and the fermentation is terminated after the pH drops to 4.50 to obtain the fermented liquid;

[0040] Demulsification: After 12-14 hours of fermentation, when the pH is 4.5-4.6, the acidity value is 90-100, stir the mixture from top to bottom and then from bottom to top to break the emulsion; stir and break the emulsion, and at the same time raise the temperature to 43°C and keep it for 120 seconds;

[0041] Secondary sterilization is pasteurization, the sterilization temperature is 70-80℃, and the time is 20-30s;

[0042] Aging: cool the secondary sterilized mixed liquid to 0℃~4℃ and age it for 4h~10h;

[0043] The low temperature plasma treatment voltage is 20-60V and the time is 3-8h;

[0044] Freezing: The material liquid treated with low-temperature plasma is continuously stirred to fill air into the material to increase its expansion rate. The expansion rate is controlled at 10% during freezing. The temperature of the refrigerant during freezing is -18°C to -23°C. 1g to 4g of micronized lactose powder is added to each kilogram of the material before freezing. During the freezing process, the material liquid is filled with air and micronized lactose powder is added to make the ice cream have an expansion rate of 10%, avoiding the loose feeling caused by excessive expansion and ensuring a solid and full taste.

[0045] Freezing treatment: The frozen ice cream is put into a mold to form a specific shape and then placed in a -30°C quick-freezing process. The quick-frozen liquid is frozen at a low temperature of -25 to -18°C for 12 to 24 hours.

[0046] Step (4) further includes: acquiring pH values ​​of the fermentation liquid at a plurality of sampling points to obtain real-time pH data during the fermentation process;

[0047] Determine the confidence distance matrix of each sampling point according to the distance between each sampling point, and then determine the standard detection data corresponding to the pH data in the fermentation process from all the confidence distance matrices;

[0048] The measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined through all the confidence distance matrices and standard detection data, and the primary fusion pH value in the fermentation process is determined according to all the measurement deviation coefficients and the pH data in the fermentation process;

[0049] Acquire temperature data of the fermentation liquid, extract characteristic quantities of the fermentation temperature according to the distribution characteristics of the temperature data, and determine the secondary fusion pH value in the fermentation process through the temperature characteristic quantities and the primary fusion pH value;

[0050] Real-time monitoring and adjustment of pH stability during fermentation based on secondary fusion pH value;

[0051] Among them, the measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined by all the confidence distance matrices and standard detection data, specifically including:

[0052] Convert standard test data into a standard initial matrix;

[0053] The adaptive support of the pH sensor corresponding to each sampling point is determined according to all the confidence distance matrices and the standard initial matrix. The adaptive support represents the average degree of correlation between the specified sensor and other sensors. The average degree of correlation is dynamically adjusted according to the actual situation of the detection data.

[0054] Determine the measurement deviation coefficient of the pH sensor corresponding to each sampling point through all the adaptive support and the pH data collected by the pH sensor at each sampling point. Determine the measurement deviation coefficient of the pH sensor corresponding to each sampling point through all the adaptive support and the pH data collected by the pH sensor at each sampling point. Specifically, the method includes:

[0055] Obtain the pH data collected by the pH sensor at each sampling point;

[0056] Determine the fluctuation value of the pH sensor corresponding to each sampling point at each sampling through all historical pH data;

[0057] Arrange the fluctuation values ​​at each sampling into a sequence according to the order of sampling time to obtain a fluctuation sequence;

[0058] Calculate the variance of the volatility series;

[0059] The measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined according to the variance of the fluctuation sequence and all the adaptive supports;

[0060] Among them, determining the secondary fusion pH value in the fermentation process by the temperature characteristic quantity and the primary fusion pH value specifically includes:

[0061] Determine the temperature compensation coefficient of the external environment;

[0062] Determine the maximum pH characteristic value and the minimum pH characteristic value in the fermentation process according to the temperature characteristic quantity and the primary fusion pH value;

[0063] The secondary fusion pH value during the fermentation process is determined by the temperature compensation coefficient, the maximum pH characteristic value and the minimum pH characteristic value.

[0064] The invention also provides quark flavored active probiotic ice cream prepared by the method.

[0065] Beneficial effects of the present invention:

[0066] 1. The ice cream prepared by the present invention has a dense, soft, and creamy mouthfeel, and also retains the advantages of beneficial metabolites and high viable count of probiotics. It is cold-resistant and can still maintain good resistance to harmful microorganisms such as yeast, mold and coliform group when stored at low temperatures, thereby improving product safety and / or extending its shelf life.

[0067] 2. The present invention adopts a variety of lactic acid bacteria fermentation, such as Lactococcus lactis, Leuconostoc mesenteroides, etc., and their different combinations can produce unique flavors of milk fragrance, fruity fragrance and diacetyl, giving the ice cream a rich fermented flavor. At the same time, the fermentation of lactic acid bacteria makes the ice cream have a natural sweet and sour taste, increasing the diversity of flavor. Through the addition of composite fermentation agents and secondary fermentation, the ice cream is rich in active probiotics, which can promote intestinal health, enhance immunity and help digestion.

[0068] 3. The scientific ratio of the composite stabilizer in the present invention, the combination of multiple ingredients such as mono- and diglycerol fatty acid esters, guar gum, taro gum and sodium carboxymethyl cellulose, can not only delay the formation of ice crystals and ensure the stability of the structure during freezing, but also provide an ideal viscosity, making the texture of ice cream more durable and stable. The composite stabilizer can not only improve the taste of ice cream, but also form a protective environment, effectively wrap and protect probiotics, prevent mechanical damage and activity loss during freezing and storage, and improve the survival rate of probiotics. The present invention also uses low-temperature plasma treatment, and the voltage is controlled between 20-60V. The low-temperature plasma treatment technology helps to improve the microbial safety of the product, extend the shelf life, and may have a beneficial effect on the texture and flavor of the ice cream. This technology reduces the oxidation reaction in the product and improves the taste and stability of the ice cream.

[0069] 4. The present invention combines advanced processes such as quark curd, active probiotics, and low-temperature plasma treatment to form a high-protein, low-fat ice cream with unique flavor and taste, filling the gap in functional and healthy ice cream on the market, and meeting the needs of modern consumers for high-end healthy food. The technical solution of the present invention has strong scalability, and its product line can be extended. By combining different flavors and prebiotics, more diversified healthy ice cream products can be developed, such as low-sugar, low-calorie, high-fiber and other special varieties, to cater to the tastes and health needs of different consumers. DETAILED DESCRIPTION

[0071] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments, but the protection scope of the present invention is not limited to the following embodiments.

[0072] The experimental methods described in the following examples are conventional methods unless otherwise specified; the reagents and materials described are commercially available unless otherwise specified.

[0073] Example 1

[0074] A method for preparing quark flavored active probiotic ice cream, comprising the following steps:

[0075] (1) Prepare materials: 750 kg of raw milk, 12 kg of inulin, 1 kg of sodium hexametaphosphate, 80 kg of white sugar, 30 kg of skim milk powder, 100 kg of cream, 40 kg of maltose syrup, 30 kg of anhydrous butter, 7 kg of compound stabilizer, and 150 U of lactic acid bacteria; wherein the compound stabilizer is composed of the following raw materials in parts by weight: 16 parts of mono- and di-glycerol fatty acid esters, 12 parts of guar gum, 20 parts of taro gum, 24 parts of sodium carboxymethyl cellulose, 3 parts of sodium polyacrylate, and 12 parts of pullulan;

[0076] (2) Filtration: After the raw milk passes the test, it is filtered using a 100-mesh single or double filter;

[0077] (3) Milk standardization: Standardize milk by using a centrifuge to remove fat from the milk and adjust it to skim milk with a fat content of less than 0.5%;

[0078] (4) Sterilization: Sterilize skim milk at 80°C for 25 seconds;

[0079] (5) Fermentation: The sterilized skim milk is cooled to 27° C., and a composite fermentation agent and rennet are added, wherein the amount of the composite fermentation agent added is 1.2 g / 50 L skim milk, and the amount of rennet added is 18 g / 1000 L skim milk; the fermentation is kept warm for 12 h at 27° C.; wherein the composite fermentation agent is composed of Lactococcus cremoris, Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. mesenteroides, and Lactococcus lactis subsp. lactis (diacetyl type) in a ratio of 2:3:2:1 in terms of viable cell count;

[0080] (6) whey removal: the fermented base material is subjected to whey removal using a whey separator, the feed rate is controlled to 800 L / h, the feed pressure is controlled to 3.5 bar, the centrifuge speed is 8500 rpm, the base material is concentrated 3 times, and the protein content is significantly increased; quark curd and whey are obtained;

[0081] (7) The quark curd is first subjected to vacuum freeze drying treatment, and then subjected to powdering and sieving treatment to obtain quark freeze-dried powder; the whey is mixed with activated carbon and a sweetener, stirred evenly, and then subjected to slurry boiling and filtering treatment to obtain a mixed slurry; wherein, the vacuum freeze drying treatment is as follows: the freeze drying tray is placed in a vacuum freeze dryer, the freezing temperature is -40°C, the vacuum degree is 100 Pa, the partition temperature is 45°C, and the freeze drying is stopped when the moisture content is less than 5%; the slurry boiling temperature is 110°C, and the time is 5 minutes;

[0082] (8) Mix the quark freeze-dried powder, mixed slurry, prebiotics, and emulsified salt, stir evenly, heat to 50-60° C., then add skim milk powder, white sugar, maltose syrup, anhydrous butter, compound stabilizer, and cream, stir while adding, and obtain a mixed liquid after the raw materials are mixed;

[0083] (9) Primary sterilization: sterilize the mixed liquid in step (8) once, wherein the primary sterilization is high temperature instantaneous sterilization at a sterilization temperature of 119° C.

[0084] (10) Homogenization: A two-stage homogenization is used to cool the sterilized mixed liquid to 65°C for secondary high-pressure homogenization. The homogenization pressure of the first stage is 15 MPa and the second stage is 4 MPa.

[0085] (11) Secondary fermentation: The mixed liquid after homogenization is cooled to 43° C., lactic acid bacteria are inoculated into the liquid, and added to the base material at an addition amount of 0.005%, and stirred sufficiently to make the lactic acid bacteria evenly dispersed. The fermentation temperature is 43° C. and the fermentation is kept warm for 5 hours. When the pH drops to 4.50, the fermentation is terminated to obtain the fermented liquid;

[0086] (12) Demulsification: After 12 hours of fermentation, when the pH is 4.5, the acidity is 90-100, and the stirring rod is stirred from top to bottom and then from bottom to top to break the emulsion; stirring to break the emulsion, and at the same time raising the temperature to 43°C and maintaining it for 120 seconds;

[0087] (13) Secondary sterilization: the demulsified feed liquid is subjected to secondary sterilization, the secondary sterilization is pasteurization, the sterilization temperature is 80° C., and the time is 20;

[0088] (14) Aging: Cool the secondary sterilized liquid to 0°C and age it for 10 hours;

[0089] (15) Low-temperature plasma treatment: The aged liquid was treated with low-temperature plasma at a voltage of 30 V for 5 h;

[0090] (16) Freezing: The material liquid treated with low-temperature plasma is continuously stirred to fill the material with air to increase its expansion rate. The expansion rate is controlled at 10% during freezing. The temperature of the refrigerant during freezing is -23°C. Before freezing, 2 g of micronized lactose powder is added to each kilogram of the material.

[0091] (17) Freezing treatment: The frozen ice cream is placed in a mold to form a specific shape and then placed in a -30°C quick-freezing process. The quick-frozen liquid is then frozen at -25°C for 12 hours.

[0092] Example 2

[0093] The difference between this embodiment and embodiment 1 is that, in step (1), the materials are prepared as follows: 650 kg of raw milk, 10 g of inulin, 0.8 kg of sodium hexametaphosphate, 70 kg of white sugar, 25 kg of skim milk powder, 90 kg of cream, 35 kg of maltose syrup, 30 kg of anhydrous butter, 6 kg of compound stabilizer, and 150 U of lactic acid bacteria; wherein the compound stabilizer is composed of the following raw materials in parts by weight: 18 parts of mono- and di-glycerol fatty acid esters, 15 parts of guar gum, 22 parts of taro gum, 26 parts of sodium carboxymethyl cellulose, 3 parts of sodium polyacrylate, and 13 parts of pullulan; and the remaining steps are the same as those in embodiment 1.

[0094] Comparative Example 1

[0095] The difference between this comparative example and Example 1 is that, in step (1), the following materials are prepared: 750 kg of raw milk, 12 kg of inulin, 1 kg of sodium hexametaphosphate, 80 kg of white sugar, 30 kg of skimmed milk powder, 100 kg of cream, 40 kg of maltose syrup, 30 kg of anhydrous butter, 7 kg of compound stabilizer, and 150 U of lactic acid bacteria; wherein the compound stabilizer is composed of the following raw materials in parts by weight: 16 parts of mono- and di-glycerol fatty acid esters, 12 parts of guar gum, 24 parts of sodium carboxymethyl cellulose, 3 parts of sodium polyacrylate, and 12 parts of pullulan; and the remaining steps are the same as those in Example 1.

[0096] Comparative Example 2

[0097] The difference between this comparative example and Example 1 is that, in step (1), the following materials are prepared: 750 kg of raw milk, 12 kg of inulin, 1 kg of sodium hexametaphosphate, 80 kg of white sugar, 30 kg of skimmed milk powder, 100 kg of cream, 40 kg of maltose syrup, 30 kg of anhydrous butter, 7 kg of compound stabilizer, and 150 U of lactic acid bacteria; wherein the compound stabilizer is composed of the following raw materials in parts by weight: 16 parts of mono- and di-glycerol fatty acid esters, 12 parts of guar gum, 20 parts of taro gum, 24 parts of sodium carboxymethyl cellulose, and 3 parts of sodium polyacrylate; and the remaining steps are the same as those in Example 1.

[0098] Comparative Example 3

[0099] The difference between this comparative example and Example 1 is that step (1) prepares the following materials: 750 kg of raw milk, 12 kg of inulin, 1 kg of sodium hexametaphosphate, 80 kg of white sugar, 30 kg of skimmed milk powder, 100 kg of light cream, 40 kg of maltose syrup, 30 kg of anhydrous butter, 7 kg of stabilizer mono- and di-glycerol fatty acid esters, and 150 U of lactic acid bacteria; the remaining steps are the same as those in Example 1.

[0100] Comparative Example 4

[0101] The difference between this comparative example and Example 1 is that the composite starter in step (5) is composed of Lactococcus cremoris, Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. mesenteroides and Lactococcus lactis subsp. lactis (diacetyl type) in a ratio of 1:1:1:1 in terms of viable cell count; and the remaining steps are the same as in Example 1.

[0102] Comparative Example 5

[0103] The difference between this comparative example and Example 1 is that the composite starter culture in step (5) is composed of Lactococcus cremoris, Lactococcus lactis subsp. lactis, and Leuconostoc mesenteroides subsp. mesenteroides in a ratio of 2:3:2 in terms of viable bacteria count; the remaining steps are the same as in Example 1.

[0104] Comparative Example 6

[0105] The difference between this comparative example and Example 1 is that step (15) of low-temperature plasma treatment is not included; the remaining steps are the same as those in Example 1.

[0106] Example 3

[0107] The vacuum freeze drying process also includes: applying microwave technology to assist heating of the quark curd;

[0108] Monitoring the moisture content of the quark curd, and stopping the vacuum freeze drying process when the moisture content is less than 5%;

[0109] Among them, microwave technology is used to assist heating of quark curd, including:

[0110] A microwave generator is arranged in the drying chamber of the vacuum freeze dryer, and the microwave generator periodically emits microwaves during the drying process to accelerate the vibration and migration of water molecules;

[0111] Controlling the frequency and power of the microwaves to ensure uniform heating of the quark curd;

[0112] Optimize the energy efficiency and time of vacuum freeze drying by adjusting the cycle and duration of microwave emission;

[0113] Based on the effect of microwave-assisted heating treatment, the operating parameters of the vacuum freeze dryer are dynamically adjusted to further shorten the drying time;

[0114] During the microwave-assisted heating process, the temperature distribution of quark curd is monitored in real time to ensure temperature uniformity;

[0115] When uneven temperature distribution is detected, the emission angle and position of the microwave generator are adjusted to improve heating uniformity;

[0116] By combining auxiliary heating with microwave technology, the vacuum freeze-drying time can be significantly shortened.

[0117] The principle and beneficial effects of the above scheme are as follows: the dryer is set to a vacuum environment of 0.05mbar, the initial temperature is maintained at -40°C, and the freeze-drying mode is turned on to gradually increase the temperature; the temperature is raised to -20°C to start sublimation of water to avoid excessive temperature rise on the surface of the quark curd and cause structural deformation; microwave parameter setting: the microwave frequency is set to 2450MHz in the drying chamber, the initial power is set to 200W, and the microwave emission cycle is set to be turned on for 3 minutes every 10 minutes, so as to control the gradual entry of heat into the quark curd; heating adjustment: by adjusting the microwave emission cycle and power, the temperature of the quark curd is maintained between -10°C and 0°C during the drying process to accelerate the vibration and migration of water molecules and increase the drying rate; real-time monitoring: the moisture content of the quark curd is monitored by a moisture sensor, and the moisture data is recorded every 15 minutes to observe its decrease. speed; when the moisture content of quark curd drops to about 10%, increase the microwave power to 300W and shorten the emission cycle to accelerate the drying process. At this stage, the duration of microwave-assisted heating is adjusted to 5 minutes, and the interval time is reduced to 5 minutes; temperature monitoring: during the drying process, the temperature of different parts of the quark curd is recorded by a temperature sensor every 10 minutes to ensure uniform heating; when uneven temperature distribution is detected, adjust the emission angle of the microwave generator by 10 degrees to optimize the heating area coverage, and make the temperature distribution of the quark curd tend to be uniform by gradually changing the microwave emission angle; stop drying: when the moisture content of the quark curd drops below 5%, stop microwave-assisted heating and vacuum freeze drying; record and analyze: record the temperature and moisture content of the final quark curd, and analyze the drying time compared with the efficiency of the traditional freeze-drying method.

[0118] Example 4

[0119] Step (4) further includes: acquiring pH values ​​of the fermentation liquid at a plurality of sampling points to obtain real-time pH data during the fermentation process;

[0120] Determine the confidence distance matrix of each sampling point according to the distance between each sampling point, and then determine the standard detection data corresponding to the pH data in the fermentation process from all the confidence distance matrices;

[0121] The measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined through all the confidence distance matrices and standard detection data, and the primary fusion pH value in the fermentation process is determined according to all the measurement deviation coefficients and the pH data in the fermentation process;

[0122] Acquire temperature data of the fermentation liquid, extract characteristic quantities of the fermentation temperature according to the distribution characteristics of the temperature data, and determine the secondary fusion pH value in the fermentation process through the temperature characteristic quantities and the primary fusion pH value;

[0123] Real-time monitoring and adjustment of pH stability during fermentation based on secondary fusion pH value;

[0124] Among them, the measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined by all the confidence distance matrices and standard detection data, specifically including:

[0125] Convert standard test data into a standard initial matrix;

[0126] The adaptive support of the pH sensor corresponding to each sampling point is determined according to all the confidence distance matrices and the standard initial matrix. The adaptive support represents the average degree of correlation between the specified sensor and other sensors. The average degree of correlation is dynamically adjusted according to the actual situation of the detection data.

[0127] Determine the measurement deviation coefficient of the pH sensor corresponding to each sampling point through all the adaptive support and the pH data collected by the pH sensor at each sampling point. Determine the measurement deviation coefficient of the pH sensor corresponding to each sampling point through all the adaptive support and the pH data collected by the pH sensor at each sampling point. Specifically, the method includes:

[0128] Obtain the pH data collected by the pH sensor at each sampling point;

[0129] Determine the fluctuation value of the pH sensor corresponding to each sampling point at each sampling through all historical pH data;

[0130] Arrange the fluctuation values ​​at each sampling into a sequence according to the order of sampling time to obtain a fluctuation sequence;

[0131] Calculate the variance of the volatility series;

[0132] The measurement deviation coefficient of the pH sensor corresponding to each sampling point is determined according to the variance of the fluctuation sequence and all the adaptive supports;

[0133] Among them, determining the secondary fusion pH value in the fermentation process by the temperature characteristic quantity and the primary fusion pH value specifically includes:

[0134] Determine the temperature compensation coefficient of the external environment;

[0135] Determine the maximum pH characteristic value and the minimum pH characteristic value in the fermentation process according to the temperature characteristic quantity and the primary fusion pH value;

[0136] The secondary fusion pH value during the fermentation process is determined by the temperature compensation coefficient, the maximum pH characteristic value and the minimum pH characteristic value.

[0137] The principle and beneficial effects of the above scheme: During the fermentation process, multiple sampling points are set, and the pH data of each point is collected regularly through the pH sensor to form a real-time pH value data stream. For example, suppose that there are 5 sampling points evenly distributed in the fermentation tank, and the pH value of each sampling point is collected once a minute to obtain a pH value data table that changes over time. According to the physical position of the sampling point, the distance between every two sampling points is calculated, and this distance is used to establish a confidence distance matrix. The mean pH value at a specific moment is used as the standard detection data to generate a standard initial matrix, and then the adaptive support and measurement deviation coefficient of each pH sensor are calculated based on the confidence distance of each sampling point. The specific operations are:

[0138] The historical pH value data of each sampling point is obtained to obtain the fluctuation value sequence at each sampling; the variance of the sequence is calculated, and the measurement deviation coefficient is determined in combination with the adaptive support. For example, if the variance of the fluctuation sequence of a sampling point is 0.03 and the adaptive support is 0.85, the measurement deviation coefficient is 0.025.

[0139] The pH value of each sampling point is corrected by the above-mentioned deviation coefficient to calculate a more accurate first-level fusion pH value. Assuming that at a certain moment, the corrected pH values ​​of sampling points 1 to 5 are 5.9, 6.0, 5.8, 5.9 and 6.1, the first-level fusion pH value is the mean:

[0140]

[0141] Obtain the temperature data of the fermentation liquid and extract temperature characteristics, such as the temperature mean and fluctuation range.

[0142] Assuming that the average temperature in the same time period is 35°C and the fluctuation range is ±2°C, calculate the maximum and minimum pH characteristic values ​​and apply them.

[0143] Test example

[0144] Determination of the survival rate of probiotics: Take a part of the finished ice cream and melt it to determine the number of probiotics in the ice cream. After culturing on MRS solid culture medium for 36 hours, the colonies are counted by the coating method and the total number of colonies in the ice cream (unit: cfu / g) is calculated. The total number of colonies in the liquid after secondary fermentation is calculated by the same method (unit: cfu / g). The total number of colonies in the ice cream is divided by the total number of colonies in the liquid after secondary fermentation and multiplied by 100% to obtain the survival rate of the probiotics (unit: %).

[0145] Sensory evaluation of ice cream: 10 tasters (5 males, 5 females, aged 20-30 years old) conducted sensory evaluation on the color, taste, aroma, texture and other aspects of ice cream. The evaluation criteria are shown in Table 1.

[0146] Table 1 Sensory evaluation criteria for ice cream

[0147]

[0148] The probiotic survival rate and sensory score results of ice cream are shown in Table 2.

[0149] Table 2 Probiotic survival rate and sensory score results of ice cream

[0150] Group Probiotic survival rate / % Sensory Rating Example 1 86.5 45 Example 2 88.1 46 Comparative Example 1 74.6 38 Comparative Example 2 76.5 39 Comparative Example 3 60.5 33 Comparative Example 4 83.1 30 Comparative Example 5 84.6 34 Comparative Example 6 78.9 38

[0151] It can be seen from the probiotic survival rate results that the probiotic survival rate of the quark flavored active probiotic ice cream prepared by the present invention is higher than that of the comparative example group, especially comparative examples 1-3 and comparative example 6. In comparative example 1, no thorny taro gum was added to the composite stabilizer, resulting in a decrease in the survival rate of probiotics, because the unique viscosity and film-forming ability of thorny taro gum help maintain the stability of probiotics, and its absence will lead to an increase in the loss of probiotics during processing. In comparative example 2, pullulan was not added to the composite stabilizer, so that the probiotic survival rate was lower than that of comparative example 1; pullulan has the ability to form a protective film, which can form a barrier around probiotics to resist adverse factors in the environment; therefore, the protective effect of the formula lacking pullulan on the survival of probiotics is weakened. In comparative example 3, only a single stabilizer (mono- and diglycerol fatty acid esters) was used, and a plurality of synergistic stabilizer components were lacking, so the probiotic survival rate would be significantly reduced. A single stabilizer cannot provide comprehensive physical and chemical protection, which will cause greater losses to probiotics during processing. In Comparative Example 6, low-temperature plasma treatment was not performed, which would reduce the survival rate of the probiotics; low-temperature plasma treatment can effectively protect the probiotics from heat, mechanical stress and oxidative damage during processing, and the lack of this treatment will reduce the survival rate of the probiotics.

[0152] It can be seen from the sensory evaluation test results that the sensory scores of the quark flavored active probiotic ice cream prepared by the present invention are significantly higher than those of the comparative group. In comparative example 1, due to the removal of the thorny taro gum, the texture of the ice cream is slightly granular, and the ice crystal feeling is more obvious, so the granularity and ice crystal feeling scores are low. Comparative example 2 removes sodium polyacrylate. Although other composite stabilizers remain unchanged, its influence is reflected in the stability of the texture: the granularity of the ice cream is slightly heavy; due to the slightly unstable composite stabilizer, the mouthfeel is slightly hard. Comparative example 3 only uses a single stabilizer (mono- and diglycerol fatty acid esters), and the single stabilizer cannot fully play its role. The ice crystal feeling and granularity are significantly enhanced, affecting the overall taste; and the texture of the ice cream is not good and is relatively rough overall. Comparative examples 4 and 5 have made adjustments to the proportion of composite leavening agents, resulting in differences in fermentation effects, the sourness of the ice cream is heavier, and the astringency is slightly enhanced. Due to the lack of low-temperature plasma treatment, comparative example 6 has a relatively rough texture, a heavy ice crystal feeling, obvious granularity, and a poor taste.

[0153] Finally, it should be noted that the above-mentioned embodiments only express several implementation methods of the present invention and are not intended to limit the invention. For ordinary technicians in this field, any modifications, equivalent substitutions, improvements, etc. made without departing from the concept of the present invention should be included in the protection scope of the invention. Therefore, the protection scope of the patent of the present invention shall be based on the attached claims.

Claims

1. A method for preparing quark flavored active probiotic ice cream, characterized in that: The following steps are involved: (1) filtering, milk standardization, sterilization, fermentation, and whey removal of raw milk to obtain quark curd and whey; (2) subjecting the quark curd to a vacuum freeze-drying treatment, and then to a powdering and sieving treatment to obtain quark freeze-dried powder; mixing the whey with activated carbon and a sweetener, stirring them evenly, and then boiling and filtering the mixture to obtain a mixed slurry; (3) Mix the quark freeze-dried powder, mixed slurry, prebiotics, and emulsified salt, stir evenly, heat to 50-60° C., then add skim milk powder, white sugar, maltose syrup, anhydrous butter, compound stabilizer, and cream, stir while adding, and obtain a mixed liquid after the raw materials are mixed; (4) The mixed liquid is subjected to primary sterilization, homogenization, secondary fermentation, demulsification, secondary sterilization, aging, low-temperature plasma treatment, freezing, and freezing treatment to obtain the product.

2. The preparation method according to claim 1, characterized in that: In step (1), the raw milk is filtered, milk standardized, sterilized, fermented, and whey removed in the following steps: Filtration: Raw milk is filtered through a 100-mesh single or double filter after passing the test; Milk standardization: Standardization of cow milk by using a centrifugal separator to remove fat from the milk and adjust it to skim milk with a fat content of less than 0.5%; Sterilization: Sterilize skim milk at 80°C for 25 seconds; Fermentation: Cool the sterilized skim milk to 27°C, add the composite starter and rennet, the addition amount of the composite starter is 1-1.2g / 50L skim milk, and the addition amount of rennet is 15-20g / 1000L skim milk; keep warm and ferment for 12-14h at 27°C; Whey removal: The fermented base material is dehumidified using a whey separator. The feed rate is controlled to 800L / h, the feed pressure is controlled to 3.5bar, and the centrifuge speed is 8500rpm. The base material is concentrated 3 times to significantly increase the protein content; quark curd and whey are obtained.

3. The preparation method according to claim 2, characterized in that: The composite fermentation agent is composed of Lactococcus cremoris, Lactococcus lactis subsp. lactis, Leuconostoc mesenteroides subsp. mesenteroides and Lactococcus lactis subsp. lactis (diacetyl type) in a ratio of 2:3:2:1 of live bacteria count.

4. The preparation method according to claim 1, characterized in that: In step (2), the freeze-drying treatment is performed by placing the freeze-drying plate in a vacuum freeze-drying machine, wherein the freezing temperature is -40°C, the vacuum degree is 100-200 Pa, the partition temperature is 45°C, and freeze-drying is stopped when the moisture content is less than 5%.

5. The preparation method according to claim 1, characterized in that: In step (2), the slurry boiling temperature is 103-115° C. and the boiling time is 3-10 min.

6. The preparation method according to claim 1, characterized in that: In step (2), 100-200 g of activated carbon and 50-100 g of sweetener are added per liter of whey; The sweetener is selected from at least one of white sugar, sucrose, fructose, fructose syrup, maltose, maltose syrup, glucose, glucose syrup, lactose, honey, sugar alcohol, sodium cyclamate, aspartame, sucralose, acesulfame potassium and neotame.

7. The preparation method according to claim 1, characterized in that: In parts by weight, the raw milk in step (1) is 680-800 parts, the prebiotics in step (3) are 8-18 parts, the emulsifying salt is 0.5-1.5 parts, the skimmed milk powder is 20-50 parts, the white sugar is 60-100 parts, the maltose syrup is 30-50 parts, the anhydrous butter is 20-50 parts, the compound stabilizer is 5-10 parts, and the light cream is 80-120 parts.

8. The preparation method according to claim 1, characterized in that: The composite stabilizer in step (3) is composed of the following raw materials in parts by weight: 15-20 parts of mono- and di-glycerol fatty acid esters, 10-20 parts of guar gum, 18-24 parts of tara gum, 22-28 parts of sodium carboxymethyl cellulose, 2-4 parts of sodium polyacrylate and 10-15 parts of pullulan.

9. The preparation method according to claim 1, characterized in that: The specific operations of primary sterilization, homogenization, secondary fermentation, demulsification, secondary sterilization, aging, low-temperature plasma treatment, freezing, and freezing treatment in step (4) are as follows: The first sterilization is ultra-high temperature instantaneous sterilization, and the sterilization temperature is 119-123℃; Homogenization: Two-stage homogenization is adopted. The mixed liquid after the primary sterilization is cooled to 65℃~70℃ for two-stage high-pressure homogenization. The homogenization pressure of the first stage is 12MPa~20MPa, and the second stage is 2MPa~6MPa. The secondary fermentation is specifically as follows: the mixed liquid after homogenization is cooled to 43° C., lactic acid bacteria are inoculated into the liquid, added into the base material at an addition amount of 0.005%, and stirred sufficiently to make the lactic acid bacteria evenly dispersed, the fermentation temperature is 43° C., the fermentation is kept warm for 5 hours, and the fermentation is terminated after the pH drops to 4.50 to obtain the fermented liquid; Demulsification: After 12-14 hours of fermentation, when the pH is 4.5-4.6, the acidity value is 90-100, stir the mixture from top to bottom and then from bottom to top to break the emulsion; stir and break the emulsion, and at the same time raise the temperature to 43°C and keep it for 120 seconds; Secondary sterilization is pasteurization, the sterilization temperature is 70-80℃, and the time is 20-30s; Aging: cool the secondary sterilized mixed liquid to 0℃~4℃ and age it for 4h~10h; The low temperature plasma treatment voltage is 20-60V and the time is 3-8h; Freezing: The material liquid treated with low-temperature plasma is continuously stirred to fill the material with air to increase its expansion rate. The expansion rate is controlled at 10% during freezing. The temperature of the refrigerant during freezing is -18°C to -23°C. Before freezing, 1g to 4g of micronized lactose powder is added to each kilogram of the material. Freezing treatment: The frozen ice cream is put into a mold to form a specific shape and then placed in a -30°C quick-freezing process. The quick-frozen liquid is frozen at a low temperature of -25 to -18°C for 12 to 24 hours.

10. Cheese ice cream prepared by the preparation method according to any one of claims 1 to 9.

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