Convenient instant northeast sauerkraut freeze-dried product and preparation method thereof

Abstract

The application discloses a kind of convenient instant northeast sauerkraut freeze-dried products and preparation method thereof, it relates to agricultural product processing technical field.The purpose of the present application is to solve the problems that traditional sauerkraut products must be transported at low temperature, are easy to smell, cannot extend the shelf life of product and the application scene is limited.The application combines vacuum freeze-drying technology with traditional fermentation technology, increases the product form of northeast sauerkraut, and greatly extends the shelf life of product, can directly enter catering industry as instant product, the product breaks the primary processing industry status of sauerkraut production, can greatly reduce the transportation cost and preservation cost of product, solves the problems that traditional sauerkraut products must be transported at low temperature, are easy to smell, cannot extend the shelf life of product and the application scene is limited.The sauerkraut freeze-dried product prepared by the application has sour flavor, crisp and tender taste, color is bright yellow and can be preserved for a long time.

Description

Technical Field

[0001] This invention relates to the field of agricultural product processing technology, specifically to a convenient ready-to-eat freeze-dried sauerkraut product from Northeast China and its preparation method. Background Technology

[0002] Northeastern sauerkraut is a processed vegetable product made from Chinese cabbage grown in Northeast China through low-temperature anaerobic fermentation. It is characterized by its tangy flavor, crisp texture, bright yellow color, and long shelf life. As a traditional fermented product, Northeastern sauerkraut is processed in large quantities in Northeast my country, serving as a crucial means of solving the winter vegetable storage problem. It has gradually transitioned from family production to industrialization. With the popularity of traditional foods and market expansion, processing enterprises mainly achieve the target shelf life of Northeastern sauerkraut through methods such as adding preservatives, pasteurization, or cold chain transportation. However, problems such as high water content, low temperatures throughout the process, and browning color prevent the sauerkraut processing industry from achieving breakthrough and rapid development.

[0003] Northeastern sauerkraut is an important form of autumn vegetable storage for people in Northeast my country and a vital means of consuming vegetables during the long winter. It boasts a long history and is one of the region's important traditional fermented foods. Northeastern sauerkraut is characterized by its tangy, crisp, and tender taste, unique flavor, rich nutrition, and health benefits, making it widely popular. For many years, sauerkraut products based on primary fermentation technology and simple packaging have been the mainstream products in the sauerkraut processing industry. However, the limited product variety, significant flavor differences, and low profit margins have been major factors hindering its slow development. Currently, with the development of the food market, population migration, and logistics, sauerkraut products based on primary processing are gaining an increasing market share in southern my country and globally, placing higher demands on the sauerkraut industry in terms of flavor, safety, and product variety.

[0004] Therefore, for the traditional fermented product Northeast sauerkraut, there is an urgent need to further extend the sauerkraut processing industry chain through technological innovation and product development, and enhance the market attributes of my country's distinctive traditional fermented sauerkraut products. Summary of the Invention

[0005] The purpose of this invention is to solve the problems of traditional sauerkraut products, such as the need for low-temperature transportation, easy spoilage, inability to extend shelf life, and limited application scenarios. The invention provides a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China that is easy to transport and store while retaining its flavor, as well as its preparation method.

[0006] This invention combines vacuum freeze-drying technology with traditional fermentation technology, increasing the product forms of Northeast sauerkraut and greatly extending its shelf life. It can be directly used as a fast food product in the catering industry. The product breaks the current industrial status quo of sauerkraut production, which is mainly based on primary processing. It can greatly reduce the transportation and storage costs of the product and solve the problems of traditional sauerkraut products, such as the need for low-temperature transportation, easy spoilage, inability to extend the shelf life, and limited application scenarios.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] A convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China is prepared by following these steps:

[0009] 1. Remove any incomplete outer leaves from the freshly prepared Northeastern sauerkraut, then wash and shred it to obtain sauerkraut shreds;

[0010] 2. Soak the shredded pickled cabbage, then drain it to obtain pre-treated shredded pickled cabbage;

[0011] 3. Blanch the pre-treated sauerkraut shreds to obtain cooked sauerkraut shreds;

[0012] 4. Freeze-dry the cooked sauerkraut shreds and package them to obtain ready-to-eat freeze-dried sauerkraut from Northeast China.

[0013] Effects of the invention:

[0014] I. This invention provides a convenient method for preparing ready-to-eat freeze-dried Northeastern sauerkraut, comprising the following steps: removing incomplete outer leaves from freshly prepared Northeastern sauerkraut, then washing and shredding it to obtain sauerkraut shreds; soaking the sauerkraut shreds, then draining them to obtain pre-treated sauerkraut shreds; blanching the pre-treated sauerkraut shreds to obtain cooked sauerkraut shreds; freeze-drying the cooked sauerkraut shreds, and packaging them to obtain the ready-to-eat freeze-dried sauerkraut product. The ready-to-eat freeze-dried sauerkraut product prepared by this invention has strong rehydration ability, can preserve the unique flavor and color of Northeastern sauerkraut, and has a long shelf life.

[0015] II. The ready-to-eat freeze-dried sauerkraut product prepared by the present invention has a sour and refreshing flavor, a crisp and tender texture, a bright yellow color, and can be stored for a long time. Attached Figure Description

[0016] Figure 1 Test report for the convenient ready-to-eat freeze-dried sauerkraut product prepared in Example 1;

[0017] Figure 2 The image shows the appearance of the convenient ready-to-eat freeze-dried sauerkraut product prepared in Example 1.

[0018] Figure 3 The first appearance of the convenient ready-to-eat freeze-dried sauerkraut product prepared in Example 1 after rehydration;

[0019] Figure 4 The image shows the second appearance of the freeze-dried, ready-to-eat Northeastern sauerkraut product prepared in Example 1 after rehydration. Detailed Implementation

[0020] Specific Implementation Method 1: This implementation method is a convenient and ready-to-eat freeze-dried sauerkraut product from Northeast China, specifically completed according to the following steps:

[0021] 1. Remove any incomplete outer leaves from the freshly prepared Northeastern sauerkraut, then wash and shred it to obtain sauerkraut shreds;

[0022] 2. Soak the shredded pickled cabbage, then drain it to obtain pre-treated shredded pickled cabbage;

[0023] 3. Blanch the pre-treated sauerkraut shreds to obtain cooked sauerkraut shreds;

[0024] 4. Freeze-dry the cooked sauerkraut shreds and package them to obtain ready-to-eat freeze-dried sauerkraut from Northeast China.

[0025] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: in step one, the freshly prepared Northeast sauerkraut is processed by removing all dark outer leaves, retaining the tender yellow inner core, and then washed 1-2 times before being shredded to obtain sauerkraut shreds; the washing method is rinsing to reduce the loss of sauerkraut components; the shredding is done in a shredder to obtain shreds with a width of 0.5cm-1cm. Other steps are the same as in Specific Implementation Method One.

[0026] In this embodiment, the cleaning of Northeastern sauerkraut mainly involves removing impurities from the surface of the sauerkraut and the original fermentation liquid.

[0027] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that: this implementation method does not specifically limit the source of the Northeastern sauerkraut; the Northeastern sauerkraut mentioned in step one is freshly prepared Northeastern sauerkraut produced solely through fermentation technology without the addition of any food additives; furthermore, the Northeastern sauerkraut is freshly prepared cellar-pickled or vat-pickled Northeastern sauerkraut; preferably, the Northeastern sauerkraut is sauerkraut obtained by fermentation using Northeastern Chinese cabbage as raw material; the fermentation is carried out using pure lactic acid bacteria. Other steps are the same as in Specific Implementation Method One or Two.

[0028] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that: the embrittlement agent in step two is calcium chloride; the color-protecting agent in step two is sodium isoascorbate; the amount of embrittlement agent added in step two is 0.1% to 0.9% of the water mass, preferably 0.3% to 0.7%, more preferably 0.5%; the amount of color-protecting agent added in step two is 0.01% to 0.05% of the water mass, preferably 0.02% to 0.04%, more preferably 0.04%. Other steps are the same as in Specific Implementation Methods One to Three.

[0029] In this embodiment, calcium chloride is added to the water used for soaking sauerkraut. The calcium chloride causes the soluble pectin in the sauerkraut to coagulate into a gel-like insoluble calcium pectate, thus maintaining the original crispness of the sauerkraut product. The addition of sodium isoascorbate to the water used for soaking sauerkraut in this invention inhibits the activity of polyphenol oxidase in the sauerkraut, blocking the oxidative browning pathway of pigment precursors in the sauerkraut and effectively preventing color deterioration during the sauerkraut processing.

[0030] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in that: the soaking method described in step two is as follows: soak the pickled cabbage shreds in water, then add a crisping agent and a color-protecting agent to the water, and soak for 0.5h to 2h, preferably 0.5h to 1.5h, more preferably 0.5h; the mass ratio of pickled cabbage shreds to water in step two is 1:(1~3). Other steps are the same as in Specific Implementation Methods One to Four.

[0031] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in that: the blanching in step three is carried out in a blanching machine, and the blanching time is preferably 1 min to 5 min, more preferably 1 min to 3 min; the mass ratio of water added during blanching in step three to the mass ratio of pickled cabbage shreds in step one is 1:(1~3), preferably 1:(1.5~2.5), more preferably 1:2. Other steps are the same as in Specific Implementation Methods One to Five.

[0032] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One through Six in that: during the blanching process in step three, the seasoning substances are first dissolved in water, and then the pre-treated pickled cabbage shreds are added to the water; the seasoning substances include one or more of the following: bone broth seasoning, five-spice powder, soy sauce, salt, and monosodium glutamate. The other steps are the same as in Specific Implementation Methods One through Six.

[0033] Specific Implementation Method Eight: This implementation method differs from Specific Implementation Methods One to Seven in that: the seasoning substances include pork bone broth seasoning, five-spice powder, and salt; the amount of pork bone broth seasoning added is 0.4% to 1.2% of the mass of water used for blanching, more preferably 0.8% to 1.2%, and even more preferably 1.0%; the five-spice powder is water-soluble, and the amount added is 0.5% to 2.5% of the mass of water used for blanching, more preferably 0.5% to 1.5%, and even more preferably 1.5%; the amount of salt added is 0.2% to 1.0% of the mass of water used for blanching, more preferably 0.6% to 1.0%, and even more preferably 0.6%. Other steps are the same as in Specific Implementation Methods One to Seven.

[0034] The bone broth seasoning described in this embodiment is bone broth seasoning powder, purchased from Quanzhou Anji Food Co., Ltd.

[0035] This embodiment does not have any special limitations on the source of the five-spice powder and salt;

[0036] The blanching described in this embodiment is mainly to cook the sauerkraut, stabilize its acidic substances, increase the solubility of its fibrous components, and enhance its rehydration ability.

[0037] In this embodiment, seasoning substances are added during the blanching process, which allows the seasoning substances to penetrate into the shredded sauerkraut, enhancing the flavor of the sauerkraut and making the prepared ready-to-eat freeze-dried sauerkraut product conform to the flavor characteristics of freeze-dried sauerkraut products from Northeast China after restoration.

[0038] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: during the freeze-drying process described in step four, lard curd is added to the cooked sauerkraut shreds. The amount of lard curd added is preferably 0.1% to 0.5% of the mass of the cooked sauerkraut shreds, more preferably 0.2% to 0.4%, and most preferably 0.3%; the freeze-drying time described in step four is 17 to 22 hours; the freeze-drying process described in step four preferably includes a pre-freezing stage, a sublimation stage, and a desorption stage performed sequentially; the pre-freezing temperature is preferably -35 to -40°C; the pre-freezing stage time is preferably 3 to 4 hours, more preferably 4 hours; The invention takes 2 hours to reach the pre-freezing temperature from room temperature; the vacuum degree of the sublimation drying stage is 10~30 Pa, more preferably 20 Pa, the shelf temperature is -15℃~0℃, more preferably -10℃, and the sublimation drying time is preferably 8~10 hours, more preferably 10 hours; the vacuum degree of the desorption drying stage is 5~15 Pa, more preferably 10 Pa, the shelf temperature is 20℃~30℃, more preferably 25℃, and the desorption drying time is preferably 4 hours~6 hours, more preferably 5 hours; the humidity in the packaging workshop in step four is 25%~45%, more preferably 35%; the workshop temperature is preferably 20℃~30℃, more preferably 25℃. Other steps are the same as in specific embodiments one to eight.

[0039] In this embodiment, the lard curds are preferably packaged quantitatively into freeze-drying molds; this embodiment does not have any special restrictions on the source of the lard curds, and conventional commercially available products in this field can be used.

[0040] The pre-freezing described in this embodiment prevents large ice crystals from piercing the cell walls of the sauerkraut, thus preventing it from becoming soft and mushy after rehydration. The pre-freezing stage of this invention is carried out under normal pressure.

[0041] The sublimation stage described in this embodiment can remove 70% of the moisture from the cooked pickled cabbage shreds;

[0042] The analytical drying stage described in this embodiment can control the final moisture content of the cooked sauerkraut shreds to 3%~5%;

[0043] This embodiment of the method can prevent the sauerkraut shreds from absorbing moisture and softening after freeze-drying by controlling the environment. This embodiment preferably involves weighing, bagging, adding an oxygen absorber, and then packaging. This embodiment does not have a specific limitation on the weighing weight; conventional packaging weights in the art are acceptable. This embodiment also does not have a specific limitation on the bagging method; conventional methods are acceptable. This embodiment does not have a specific limitation on the type and source of the oxygen absorber; commercially available oxygen absorber products are acceptable.

[0044] Specific Implementation Method 10: This embodiment of a convenient ready-to-eat freeze-dried sauerkraut product is prepared according to any one of the preparation methods described in Specific Implementation Methods 1 to 9.

[0045] This embodiment provides a ready-to-eat freeze-dried sauerkraut product from Northeast China. The freeze-dried sauerkraut product can be quickly rehydrated, and after rehydration, it has a sour and fresh taste, a crisp texture, and the unique flavor of Northeast China sauerkraut.

[0046] To further illustrate the present invention, the ready-to-eat freeze-dried sauerkraut product and its preparation method provided by the present invention will be described in detail below with reference to the accompanying drawings and embodiments, but these should not be construed as limiting the scope of protection of the present invention.

[0047] Example 1: A method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China, specifically comprising the following steps:

[0048] 1. Remove any incomplete outer leaves from the freshly prepared Northeastern sauerkraut, rinse twice, and cut into uniform shreds of 0.5cm to 1cm to obtain sauerkraut shreds;

[0049] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.01 kg of calcium chloride (0.5% of the water mass) and 0.0008 kg of sodium isoascorbate (0.04% of the water mass) to the water. Soak for 0.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0050] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.02kg of pork bone broth seasoning powder (1.0% of the water weight), 0.03kg of water-soluble five-spice powder (1.5% of the water weight), and 0.012kg of salt (0.06% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 2 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0051] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2kg of cooked sauerkraut shreds in each packaging tray of the freeze-drying equipment. 0.006kg of lard curd is added to the packaging tray. The tray is placed in a -40℃ refrigerator for 2 hours to obtain pre-frozen sauerkraut shreds.

[0052] V. Freeze-drying: The pre-frozen sauerkraut shreds are placed in a vacuum freeze dryer for drying. First, they are pre-frozen at a pre-freezing temperature of -40℃ for 24 hours; then, they are sublimated and dried at a vacuum of 20Pa and a shelf temperature of -10℃ for 10 hours; finally, they are desorption and dried at a vacuum of 10Pa and a shelf temperature of 25℃ for 5 hours to obtain vacuum freeze-dried sauerkraut shreds.

[0053] VI. Packaging: Vacuum freeze-dried sauerkraut shreds are weighed, bagged, and packaged after adding oxygen absorbers under workshop humidity of 25%~45% and workshop temperature of 20℃~30℃.

[0054] Example 2: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0055] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.006 kg of calcium chloride (0.3% of the water mass) and 0.0004 kg of sodium isoascorbate (0.02% of the water mass) to the water. Soak for 0.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0056] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.016kg of pork bone broth seasoning powder (0.8% of the water weight), 0.01kg of water-soluble five-spice powder (0.5% of the water weight), and 0.012kg of salt (0.06% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 1 minute. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0057] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.004 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0058] Example 3: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0059] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.006 kg of calcium chloride (0.3% of the water mass) and 0.0006 kg of sodium isoascorbate (0.03% of the water mass) to the water. Soak for 1 hour, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0060] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.016kg of pork bone broth seasoning powder (0.8% of the water weight), 0.02kg of water-soluble five-spice powder (1.0% of the water weight), and 0.016kg of salt (0.08% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 2 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0061] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.006 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0062] Example 4: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0063] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.006 kg of calcium chloride (0.3% of the water mass) and 0.0008 kg of sodium isoascorbate (0.04% of the water mass) to the water. Soak for 1.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0064] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.016kg of pork bone broth seasoning powder (0.8% of the water weight), 0.03kg of water-soluble five-spice powder (1.5% of the water weight), and 0.02kg of salt (1.0% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 3 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0065] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.008 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0066] Example 5: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0067] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.001 kg of calcium chloride (0.5% of the water mass) and 0.0004 kg of sodium isoascorbate (0.02% of the water mass) to the water. Soak for 1 hour, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0068] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.02kg of pork bone broth seasoning powder (1.0% of the water weight), 0.01kg of water-soluble five-spice powder (0.5% of the water weight), and 0.016kg of salt (0.8% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 3 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0069] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.008 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0070] Example 6: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0071] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.001 kg of calcium chloride (0.5% of the water mass) and 0.0006 kg of sodium isoascorbate (0.03% of the water mass) to the water. Soak for 1.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0072] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.02kg of pork bone broth seasoning powder (1.0% of the water weight), 0.02kg of water-soluble five-spice powder (1.0% of the water weight), and 0.02kg of salt (1.0% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 3 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0073] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.004 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0074] Example 7: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0075] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.014 kg of calcium chloride (0.7% of the water mass) and 0.0004 kg of sodium isoascorbate (0.02% of the water mass) to the water. Soak for 1.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0076] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.024kg of pork bone broth seasoning powder (1.2% of the water weight), 0.01kg of water-soluble five-spice powder (0.5% of the water weight), and 0.02kg of salt (1.0% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 2 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0077] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.006 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0078] Example 8: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0079] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.014 kg of calcium chloride (0.7% of the water mass) and 0.0006 kg of sodium isoascorbate (0.03% of the water mass) to the water. Soak for 0.5 hours, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0080] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.024kg of pork bone broth seasoning powder (1.2% of the water weight), 0.02kg of water-soluble five-spice powder (1.0% of the water weight), and 0.012kg of salt (0.6% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 3 minutes. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0081] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.008 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0082] Example 9: The difference between this example and Example 1 is the pre-treatment method for the pickled cabbage, as detailed below:

[0083] 2. Soak 1 kg of pickled cabbage shreds in 2 kg of water (the mass ratio of pickled cabbage shreds to water is 1:2). Add 0.014 kg of calcium chloride (0.7% of the water mass) and 0.0008 kg of sodium isoascorbate (0.04% of the water mass) to the water. Soak for 1 hour, then remove and drain to obtain pre-treated pickled cabbage shreds.

[0084] 3. Add 2kg of water (the ratio of pickled cabbage shreds to water is 1:2) to the blanching machine. Add 0.024kg of pork bone broth seasoning powder (1.2% of the water weight), 0.03kg of water-soluble five-spice powder (1.5% of the water weight), and 0.016kg of salt (0.8% of the water weight) to the water. After all the seasonings are dissolved and mixed evenly, add the pre-treated pickled cabbage shreds and blanch for 1 minute. Remove and drain, then cool to room temperature to obtain cooked pickled cabbage shreds.

[0085] IV. Preparation before drying: The cooked sauerkraut shreds are divided into 2 kg of shredded sauerkraut in each freeze-drying equipment tray. 0.004 kg of lard curd is added to each tray. The trays are then placed in a -40°C freezer for 2 hours to obtain pre-frozen sauerkraut shreds. Other steps and methods are the same as in Example 1.

[0086] Example 10: The difference between this example and Example 1 is that 0.004 kg of lard curd is added to the dispensing tray in step four. All other steps and methods are the same as in Example 1.

[0087] Example 11: The difference between this example and Example 1 is that 0.008 kg of lard curd is added to the dispensing tray in step four. All other steps and methods are the same as in Example 1.

[0088] Comparative Example 1: The difference between this example and Example 1 is that 0 kg of lard curd is added to the dispensing tray in step four. All other steps and methods are the same as in Example 1.

[0089] Comparative Example 2: The difference between this example and Example 1 is that 0 kg of calcium chloride was added in step two. All other steps and methods are the same as in Example 1.

[0090] Comparative Example 3: The difference between this example and Example 1 is that 0 kg of sodium isoascorbate was added in step two. All other steps and methods are the same as in Example 1.

[0091] Comparative Example 4: The difference between this example and Example 1 is that in step three, 0 kg of concentrated bone broth seasoning powder, 0 kg of water-soluble five-spice powder, and 0 kg of salt are added to the water. All other steps and methods are the same as in Example 1.

[0092] Application Example 1:

[0093] Sensory evaluation test:

[0094] A sensory evaluation team was organized to prepare and evaluate the freeze-dried sauerkraut products obtained in Examples 1-11 and Comparative Examples 1-4. The method for preparing sensory evaluation samples was as follows: 10g of freeze-dried sauerkraut product was added to 100mL of boiling water and allowed to stand for 3 minutes to obtain the sample to be tested. The specific method of sensory evaluation was as follows: The evaluation was conducted in a food sensory evaluation laboratory. The sensory evaluation team consisted of 20 people (male:female ratio 1:1, age 22-55), and the sensory evaluators had to undergo systematic training. Samples were randomly assigned after being coded. Sample scoring was based on a 100-point scale, with rehydrated form accounting for 40 points, color for 10 points, integrity for 10 points, taste and aroma for 20 points, and crispness for 20 points. A higher overall score indicated better product quality.

[0095] The sensory evaluation criteria are shown in Table 1.

[0096] Table 1 Sensory Evaluation Criteria

[0097]

[0098] The sensory evaluation results are shown in Table 2.

[0099] Table 2 Sensory Evaluation Scoring Table

[0100]

[0101] Table 2 shows that the evaluation results of Examples 1-9 indicate that different amounts of calcium chloride, sodium isoascorbate, soaking time, and blanching time directly affect the rehydration state, color, taste, aroma, crispness, and chewiness of ready-to-eat freeze-dried sauerkraut. Under the optimized conditions of Example 1, the comprehensive score reached 92 points. The evaluation results of Examples 10-11 show that reducing lard curds significantly reduces the release of taste and aroma from ready-to-eat freeze-dried sauerkraut. The evaluation results of Examples 1-9 and Comparative Example 2 show that the addition of calcium chloride significantly improves the crispness of ready-to-eat freeze-dried sauerkraut. The evaluation results of Examples 1-9 and Comparative Example 3 show that the addition of sodium isoascorbate significantly improves the color of ready-to-eat freeze-dried sauerkraut. The evaluation results of Examples 1-9 and Comparative Example 4 show that the addition of flavoring substances significantly improves the taste and aroma of ready-to-eat freeze-dried sauerkraut.

[0102] Application Example 2:

[0103] Quality index determination during shelf life:

[0104] All ready-to-eat freeze-dried sauerkraut products prepared in the examples and comparative examples were sealed and packaged using the same packaging method and stored in a dry and cool place. The moisture content and rehydration rate of the ready-to-eat freeze-dried sauerkraut products prepared in Example 1 and Comparative Example 1 were tested on days 0, 60, 180, and 270, respectively. Moisture content was determined using the method in GB5009.3-2016 and expressed as a percentage (%). The rehydration rate was tested as follows: 5g of freeze-dried sauerkraut was weighed and placed in 500g of distilled water at 40℃, sealed and soaked for 20 minutes, gently shaken 2-3 times during this period, filtered through an 80-mesh sieve, drained vertically for 2 minutes, and the surface water was gently absorbed with filter paper. The product was then quickly weighed, and the rehydration rate (times) was calculated according to the formula.

[0105] Wherein: Rehydration rate (times) = Weight after rehydration and draining / Weight of dry sample;

[0106] Table 3 Results of quality index measurements during the shelf life.

[0107]

[0108] As shown in Table 3, the ready-to-eat freeze-dried sauerkraut prepared by this invention has a shelf life of up to 9 months. Its moisture content meets the requirements for moisture content within the shelf life of freeze-dried products, and the rehydration rate is greater than 8 times. This indicates that the ready-to-eat freeze-dried sauerkraut prepared by this method has excellent rehydration performance within a 9-month shelf life.

[0109] Figure 1Test report for the convenient ready-to-eat freeze-dried sauerkraut product prepared in Example 1;

[0110] from Figure 1 It can be seen that no nitrite was detected in the convenient ready-to-eat freeze-dried sauerkraut product prepared in Example 1.

Claims

1. A method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China, characterized in that... The preparation method is specifically carried out according to the following steps:

1. Remove any incomplete outer leaves from the freshly prepared Northeastern sauerkraut, then wash and shred it to obtain sauerkraut shreds; 2. Soak the shredded pickled cabbage, then drain it to obtain pre-treated shredded pickled cabbage; 3. Blanch the pre-treated sauerkraut shreds to obtain cooked sauerkraut shreds; 4. Freeze-dry the cooked sauerkraut shreds and package them to obtain ready-to-eat freeze-dried sauerkraut from Northeast China.

2. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China according to claim 1, characterized in that... In step one, the freshly prepared Northeast sauerkraut is sorted by removing all the dark outer leaves and keeping the tender yellow sauerkraut core. It is then washed 1 to 2 times and shredded to obtain sauerkraut shreds. The washing method is rinsing to reduce the loss of the sauerkraut's internal components. The shredding is done in a shredder to obtain shreds with a width of 0.5cm to 1cm.

3. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product according to claim 1, characterized in that... The Northeastern sauerkraut mentioned in step one is freshly prepared Northeastern sauerkraut produced solely through fermentation technology without the addition of any food additives.

4. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China according to claim 1, characterized in that... The embrittlement agent mentioned in step two is calcium chloride; the color-protecting agent mentioned in step two is sodium isoascorbate; the amount of embrittlement agent added in step two is 0.1%~0.9% of the water mass; the amount of color-protecting agent added in step two is 0.01%~0.05% of the water mass.

5. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product according to claim 1, characterized in that... The soaking method described in step two is as follows: soak the pickled cabbage shreds in water, then add a crisping agent and a color-protecting agent to the water, and soak for 0.5h~2h; the mass ratio of the pickled cabbage shreds to the water in step two is 1:(1~3).

6. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China according to claim 1, characterized in that... The blanching in step three is carried out in a blanching machine, and the blanching time is preferably 1 min to 5 min; the mass ratio of water added during blanching in step three to the mass ratio of shredded pickled cabbage in step one is 1:(1~3).

7. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China according to claim 1, characterized in that... In step three, when blanching the vegetables, add seasonings. First, dissolve the seasonings in water, and then add the pre-treated pickled cabbage shreds to the water. The seasonings include one or more of the following: bone broth seasoning, five-spice powder, soy sauce, salt, and monosodium glutamate.

8. The method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product according to claim 7, characterized in that... The seasoning substances include pork bone broth seasoning, five-spice powder, and salt; the amount of pork bone broth seasoning added is 0.4% to 1.2% of the water used for blanching; the five-spice powder is water-soluble and is added at a rate of 0.5% to 2.5% of the water used for blanching; the amount of salt added is 0.2% to 1.0% of the water used for blanching.

9. A method for preparing a convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China according to claim 1, characterized in that... In step four, during freeze-drying, lard curd is added to the cooked sauerkraut shreds, preferably at a rate of 0.1% to 0.5% of the mass of the cooked sauerkraut shreds; the freeze-drying time in step four is 17 to 22 hours; the freeze-drying in step four preferably includes a pre-freezing stage, a sublimation stage, and a desorption stage performed sequentially; the pre-freezing temperature is preferably -35 to -40°C; the shelf temperature in the sublimation drying stage is -15°C to 0°C; the shelf temperature in the desorption drying stage is 20°C to 30°C; the humidity in the packaging workshop in step four is 25% to 45%, and the temperature in the workshop is 20°C to 30°C.

10. A convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China, characterized in that... A convenient, ready-to-eat freeze-dried sauerkraut product from Northeast China is prepared according to the preparation method described in any one of claims 1 to 9.

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