Freeze-drying method for black-boned chicken

Abstract

This invention provides a freeze-drying method for black-boned chicken, relating to the field of freeze-drying technology. The freeze-drying method includes the following steps: (1) Pretreatment: After slaughtering the black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into pieces; (2) Mix the pretreated black-boned chicken with rice wine, steam it over water, and drain the water; (3) Freeze-drying: Pre-freeze the drained black-boned chicken, and then perform a first stage of heating, a second stage of heating, a third stage of cooling, and a fourth stage of heating to obtain the final product. The freeze-dried black-boned chicken obtained by the freeze-drying method of this invention has a low water activity, which can effectively extend the shelf life. At the same time, it has good rehydration properties and has better hardness and adhesiveness after rehydration.

Description

Technical Field

[0001] This invention relates to the field of freeze-drying technology, specifically to a method for freeze-drying black-boned chicken. Background Technology

[0002] Currently, there are various drying technologies for fresh chicken, such as hot air drying, microwave drying, and vacuum freeze drying. Related research includes: Wu Mangang, Wang Junshan, Duan Likun, et al. Drying effect of different drying methods on chicken cubes [J]. Food and Fermentation Industries, 2019, 45(7):7. After thawing the chicken in a 4℃ refrigerator, wash it, remove excess bones, skin and fat, cut the chicken into cubes, and discard irregular samples. After the water boils, put the chicken cubes in and cook for 3 minutes. After draining, take 10g of the more regular-shaped samples and put them into the drying oven for drying. The study further investigated the effects of three drying conditions on the drying effect of diced chicken: ① hot air drying at 80℃, wind speed of 0.8m / s, and drying time of 0-5h; ② microwave-hot air drying at 80℃, wind speed of 0.8m / s, microwave power of 400-500W, microwave frequency of 2450MHz, and drying time of 0-48min; ③ vacuum freeze-drying at -75℃ and drying time of 24h. The results showed that vacuum freeze-drying better preserves the chicken's tissue structure and provides good rehydration, making it suitable for producing products with high quality requirements, although it has a longer drying time.

[0003] Freeze-drying, also known as lyophilization, is carried out at low temperatures, making it particularly suitable for many heat-sensitive substances, such as proteins and microorganisms, which do not denature or lose their biological activity after freeze-drying. During the freeze-drying process, microbial growth and enzymatic activity are inhibited, thus preserving the original properties. At low temperatures, the loss of volatile components and heat-denatured nutrients is minimal, making it suitable for drying some pharmaceuticals and foods. Because drying occurs in a frozen state, the volume and shape of the product remain almost unchanged, maintaining its original structure and preventing concentration. The dried material is loose and porous, spongy in nature, and dissolves rapidly and completely upon rehydration, almost immediately restoring its original properties. Furthermore, drying under vacuum creates a highly oxygen-deficient environment, protecting easily oxidized substances. Vacuum-freeze-dried products have extremely low moisture content, generally below 5%, which is beneficial for storage; they can be stored at room temperature for up to 10 years under vacuum packaging.

[0004] Related research, such as patent CN1478419A, discloses the freeze-drying of chicken and chicken broth. Specifically, frozen chicken meat or broth is placed between two heating plates in a freeze dryer; the temperature of the water vapor condenser is -50℃ to -30℃; the vacuum degree of the drying chamber is 100Pa-130Pa; the heating plate temperature is 30℃-100℃; this is maintained for 6-25 hours; the pressure inside the drying chamber (box) is gradually reduced to a vacuum degree of 10Pa-30Pa; the temperature of the chicken meat and broth is close to the heating plate temperature of 30℃-60℃; after maintaining this temperature for 1-5 hours, freeze-dried chicken broth and chicken meat are obtained. However, the freeze-drying process described above has poor results and is difficult to completely achieve freeze-drying, leading to a decrease in the yield rate.

[0005] For example, patent CN113598328A discloses a freeze-dried chicken product and its preparation method, including the following steps: S1, mixing and chopping the raw materials to obtain chicken paste; S2, pre-steaming, extruding and puffing the chicken paste, and cutting it to obtain chicken cubes; S3, adding vegetable oil to the chicken cubes, stirring evenly, and then steaming to obtain cooked chicken cubes; S4, microwaving and vacuum freeze-drying the cooked chicken cubes to obtain freeze-dried chicken products. The vacuum freeze-drying process includes the following steps: ① pre-freezing the microwave-dried chicken cubes at -30 to -35°C for 2-3 hours; ② raising the temperature to -20 to -25°C and maintaining it for 1-2 hours; ③ then raising the temperature to 25-30°C, drawing a vacuum to 3-5 Pa, and maintaining it for 1-2 hours. However, the steps in the above invention involve one or two freeze-drying processes. If the endpoint of the freeze-drying is not reasonably estimated, the drying process may collapse, leading to a decline in quality.

[0006] Given the problems of long processing time, easy collapse of frozen blocks, and low pass rate in existing chicken freeze-drying processes, it is essential to find a freeze-drying method for black-boned chicken that is short in processing time, has a high pass rate, and produces high-quality freeze-dried chicken. Summary of the Invention

[0007] This invention addresses the problems existing in the prior art by providing a freeze-drying method for black-boned chicken. The black-boned chicken prepared by this freeze-drying method has a low water activity, which can effectively extend its shelf life. At the same time, it has good rehydration properties and exhibits superior hardness and adhesiveness after rehydration.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This invention provides a freeze-drying method for black-boned chicken, comprising the following steps:

[0010] (1) Pre-treatment: After slaughtering the black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into pieces;

[0011] (2) Mix the pre-treated black-boned chicken with rice wine, steam it over water, and drain the water.

[0012] (3) Freeze-drying: After draining the water, the black-boned chicken is pre-frozen, and then subjected to the first stage of heating, the second stage of heating, the third stage of cooling and the fourth stage of heating to obtain the product.

[0013] Furthermore, the steaming time in step (2) is 1.4-1.7 hours.

[0014] Preferably, the steaming time in step (2) is 1.5 hours.

[0015] Furthermore, the weight ratio of black-boned chicken and rice wine in step (2) is (2-8):1.

[0016] Preferably, the weight ratio of black-boned chicken and rice wine in step (2) is 5:1.

[0017] Furthermore, in step (3), the pre-freezing temperature is -50 to -40℃, the cooling rate is -40 to 50℃ / h, and the temperature is maintained for 1-3 hours.

[0018] Preferably, in step (3), the pre-freezing temperature is -45℃, the cooling rate is -45℃ / h, and the temperature is maintained for 2h.

[0019] Further, in step (3), the temperature of the first stage of heating is -40 to -35℃ and is kept constant for 1-2 hours; the temperature of the second stage of heating is -25 to -20℃ and is kept constant for 1-2 hours; the temperature of the third stage of cooling is -28 to -25℃ and is kept constant for 0.5 hours; and the temperature of the fourth stage of heating is 20-25℃ and is kept constant for 1-2 hours.

[0020] Preferably, in step (3), the temperature of the first stage of heating is -37 to -35°C and is kept constant for 1 to 1.5 hours; the temperature of the second stage of heating is -24 to -21°C and is kept constant for 1 to 1.5 hours; the temperature of the third stage of cooling is -26 to -25°C and is kept constant for 0.5 hours; and the temperature of the fourth stage of heating is 22 to 25°C and is kept constant for 1.5 to 2 hours.

[0021] More preferably, in step (3), the temperature of the first stage of heating is -36℃ and held constant for 1 hour, the temperature of the second stage of heating is -22℃ and held constant for 1 hour, the temperature of the third stage of cooling is -25℃ and held constant for 0.5 hours, and the temperature of the fourth stage of heating is 25℃ and held constant for 2 hours.

[0022] Furthermore, in step (3), the heating rate of the first stage is 20-25℃ / h, the heating rate of the second stage is 10-15℃ / h, the cooling rate of the third stage is -2 to -4℃ / h, and the heating rate of the fourth stage is 20-25℃ / h; the vacuum degree during the first stage heating, the second stage heating, the third stage cooling, and the fourth stage heating is 30-50Pa.

[0023] Preferably, in step (3), the heating rate of the first stage is 22-25℃ / h, the heating rate of the second stage is 10-14℃ / h, the cooling rate of the third stage is -2 to -3℃ / h, and the heating rate of the fourth stage is 20-24℃ / h; the vacuum degree during the first stage heating, the second stage heating, the third stage cooling, and the fourth stage heating is 30-40Pa.

[0024] More preferably, in step (3), the heating rate of the first stage is 25℃ / h, the heating rate of the second stage is 12℃ / h, the cooling rate of the third stage is -2℃ / h, and the heating rate of the fourth stage is 22℃ / h; the vacuum degree during the first stage heating, the second stage heating, the third stage cooling and the fourth stage heating is 35Pa.

[0025] Furthermore, the present invention also provides freeze-dried black-boned chicken prepared by the above-described freeze-drying method.

[0026] The technical effects achieved by this invention are:

[0027] 1. Because rapid cooling results in smaller ice crystals and less structural damage, the rehydration ability of the obtained freeze-dried product will be significantly reduced. Therefore, this invention adopts a staged vacuum drying method, which controls the gradient heating and cooling process, and is used in conjunction with rice wine to prepare freeze-dried black-boned chicken. This freeze-drying method can maintain good rehydration while ensuring the formation of smaller ice crystals. The resulting sample has good hardness and chewiness after rehydration.

[0028] 2. The freeze-drying process of the present invention reduces the time consumption of freeze-drying and has a lower water activity through the implementation of a gradient process. At the same time, the freeze-dried black-boned chicken has a high qualification rate, less loss of nutrients, and excellent quality, and has a long storage time under normal temperature conditions. Detailed Implementation

[0029] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention.

[0030] Before further describing specific embodiments of the present invention, it should be understood that the scope of protection of the present invention is not limited to the specific embodiments described below; it should also be understood that the terminology used in the embodiments of the present invention is for describing specific embodiments and not for limiting the scope of protection of the present invention.

[0031] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the invention, both endpoints of each numerical range and any value between the two endpoints may be selected. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0032] It is worth noting that the black-boned chicken used in this invention was purchased from Hongrenju Trading Co., Ltd. in Ji'an City, Jiangxi Province; the yellow rice wine was purchased from Shanghai Shengjie Industrial Co., Ltd. (14% vol); the white wine was purchased from Anhui Chizhong Winery Co., Ltd. (52% vol); and the remaining raw materials were all ordinary commercially available products, so their sources are not specifically limited.

[0033] Example 1

[0034] A freeze-drying method for black-boned chicken, comprising the following steps:

[0035] (1) Pre-treatment: After slaughtering the live black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into one-inch square pieces;

[0036] (2) Place chicken pieces in a jar, add an appropriate amount of rice wine, seal, and steam thoroughly over water (time is 1.5h). Use 20kg of rice wine for every 100kg of black-boned chicken.

[0037] (3) Freeze-drying: Drain the wine-processed black-boned chicken and place it in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for pre-freezing at -45℃ (cooling rate -45℃ / h). After reaching -45℃, maintain the temperature for 2 hours. Turn on the vacuum pump, adjust the vacuum degree to 35Pa, and then carry out the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating to obtain the wine-processed black-boned chicken freeze-dried product.

[0038] First stage of heating: heating rate is 25℃ / h, heating to -36℃, and holding the temperature for 1h;

[0039] The second stage of heating: the heating rate is 12℃ / h, the temperature is raised to -22℃, and then held at a constant temperature for 1h;

[0040] The third stage of cooling: the cooling rate is -2℃ / h, the temperature is lowered to -25℃, and then held at a constant temperature for 0.5h;

[0041] The fourth stage of heating: the heating rate is 22℃ / h, the temperature is raised to 25℃, and then kept constant for 2h.

[0042] Example 2

[0043] A freeze-drying method for black-boned chicken, comprising the following steps:

[0044] (1) Pre-treatment: After slaughtering the live black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into one-inch square pieces;

[0045] (2) Place chicken pieces in a jar, add an appropriate amount of rice wine, seal, and steam thoroughly over water (time is 1.4h). Use 12.5kg of rice wine for every 100kg of black-boned chicken.

[0046] (3) Freeze-drying: Drain the water from the wine-processed black-boned chicken and place it in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for freeze-drying. Pre-freeze at -50℃ (cooling rate -50℃ / h), and maintain the temperature at -50℃ for 1 hour. Turn on the vacuum pump, adjust the vacuum degree to 30Pa, and then perform the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating to obtain the wine-processed black-boned chicken freeze-dried product.

[0047] First stage of heating: heating rate is 20℃ / h, heating to -40℃, and holding the temperature for 1h;

[0048] The second stage of heating: the heating rate is 10℃ / h, the temperature is raised to -25℃, and the temperature is held constant for 1h;

[0049] The third stage of cooling: the cooling rate is -2℃ / h, the temperature is lowered to -28℃, and then held at a constant temperature for 0.5h;

[0050] The fourth stage of heating: the heating rate is 20℃ / h, the temperature is raised to 20℃, and then held at a constant temperature for 1 hour.

[0051] Example 3

[0052] A freeze-drying method for black-boned chicken, comprising the following steps:

[0053] (1) Pre-treatment: After slaughtering the live black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into one-inch square pieces;

[0054] (2) Place chicken pieces in a jar, add an appropriate amount of rice wine, seal, and steam thoroughly over water (time is 1.7h). Use 50kg of rice wine for every 100kg of black-boned chicken.

[0055] (3) Freeze-drying: Drain the water from the wine-processed black-boned chicken and place it in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for freeze-drying. Pre-freeze at -40℃ (cooling rate -40℃ / h), and maintain the temperature at -40℃ for 3 hours. Turn on the vacuum pump, adjust the vacuum degree to 50Pa, and then carry out the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating to obtain the wine-processed black-boned chicken freeze-dried product.

[0056] First stage of heating: The heating rate is 25℃ / h, the temperature is raised to -35℃, and then held at a constant temperature for 1.5h;

[0057] The second stage of heating: the heating rate is 15℃ / h, the temperature is raised to -20℃, and then held at a constant temperature for 2h;

[0058] The third stage of cooling: the cooling rate is -4℃ / h, the temperature is lowered to -25℃, and then held at a constant temperature for 0.5h;

[0059] The fourth stage of heating: the heating rate is 25℃ / h, the temperature is raised to 25℃, and then kept constant for 2 hours.

[0060] Example 4

[0061] A freeze-drying method for black-boned chicken, comprising the following steps:

[0062] (1) Pre-treatment: After slaughtering the live black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into one-inch square pieces;

[0063] (2) Place chicken pieces in a jar, add an appropriate amount of rice wine, seal, and steam thoroughly over water (time is 1.5h). Use 15kg of rice wine for every 100kg of black-boned chicken.

[0064] (3) Freeze-drying: Drain the water from the wine-processed black-boned chicken and place it in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for freeze-drying. Pre-freeze at -50℃ (cooling rate -40℃ / h), and maintain the temperature at -50℃ for 1 hour. Turn on the vacuum pump, adjust the vacuum degree to 30Pa, and then perform the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating to obtain the wine-processed black-boned chicken freeze-dried product.

[0065] First stage of heating: heating rate is 22℃ / h, heating to -37℃, and holding at constant temperature for 1h;

[0066] The second stage of heating: the heating rate is 10℃ / h, the temperature is raised to -24℃, and the temperature is held constant for 1h;

[0067] The third stage of cooling: the cooling rate is -2℃ / h, the temperature is lowered to -26℃, and then held at a constant temperature for 0.5h;

[0068] The fourth stage of heating: the heating rate is 20℃ / h, the temperature is raised to 22℃, and then held at a constant temperature for 1 hour.

[0069] Example 5

[0070] A freeze-drying method for black-boned chicken, comprising the following steps:

[0071] (1) Pre-treatment: After slaughtering the live black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into one-inch square pieces;

[0072] (2) Place chicken pieces in a jar, add an appropriate amount of rice wine, seal, and steam thoroughly over water (time is 1.5h). Use 40kg of rice wine for every 100kg of black-boned chicken.

[0073] (3) Freeze-drying: Drain the water from the wine-processed black-boned chicken and place it in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for freeze-drying. Pre-freeze at -40℃ (cooling rate -50℃ / h), and maintain the temperature at -40℃ for 3 hours. Turn on the vacuum pump, adjust the vacuum degree to 40Pa, and then carry out the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating to obtain the wine-processed black-boned chicken freeze-dried product.

[0074] First stage of heating: The heating rate is 25℃ / h, the temperature is raised to -35℃, and then held at a constant temperature for 1.5h;

[0075] The second stage of heating: the heating rate is 14℃ / h, the temperature is raised to -21℃, and then held at a constant temperature for 2h;

[0076] The third stage of cooling: the cooling rate is -3℃ / h, cooling down to -25℃, and maintaining the temperature for 0.5h;

[0077] The fourth stage of heating: the heating rate is 24℃ / h, the temperature is raised to 25℃, and then held at a constant temperature for 2h.

[0078] Comparative Example 1

[0079] The only difference from Example 1 is that the rice wine in step (2) is replaced with an equal amount of white wine.

[0080] Comparative Example 2

[0081] The difference from Example 1 lies only in the freeze-drying step: the wine-processed black-boned chicken is drained and placed in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for pre-freezing at -45℃ (cooling rate -45℃ / h), and then held at -45℃ for 2 hours. The vacuum pump is then turned on, the vacuum degree is adjusted to 35Pa, and then the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating are performed to obtain the wine-processed black-boned chicken freeze-dried product.

[0082] First stage of heating: heating rate is 18℃ / h, heating to -34℃, and holding the temperature for 1h;

[0083] The second stage of heating: the heating rate is 8℃ / h, the temperature is raised to -18℃, and then held at a constant temperature for 1h;

[0084] The third stage of cooling: the cooling rate is -1℃ / h, cooling down to -24℃, and maintaining the temperature for 0.5h;

[0085] The fourth stage of heating: the heating rate is 18℃ / h, the temperature is raised to 27℃, and then held at a constant temperature for 2h.

[0086] Comparative Example 3

[0087] The only difference from Example 1 is that the freeze-drying step is as follows: The wine-processed black-boned chicken is drained and placed in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for pre-freezing at -45℃ (cooling rate -45℃ / h). After reaching -45℃, the temperature is maintained for 2 hours. The vacuum pump is then turned on, and the vacuum degree is adjusted to 35Pa. Then, the first stage of heating, the second stage of heating, the third stage of cooling, and the fourth stage of heating are performed to obtain the wine-processed black-boned chicken freeze-dried product.

[0088] First stage of heating: heating rate is 26℃ / h, heating to -42℃, and holding at constant temperature for 1h;

[0089] The second stage of heating: the heating rate is 16℃ / h, the temperature is raised to -26℃, and then held at a constant temperature for 1h;

[0090] The third stage of cooling: the cooling rate is -5℃ / h, the temperature is lowered to -30℃, and then kept constant for 0.5h;

[0091] The fourth stage of heating: the heating rate is 27℃ / h, the temperature is raised to 18℃, and then held at a constant temperature for 2 hours.

[0092] Comparative Example 4

[0093] The difference from Example 1 lies only in the freeze-drying step: the wine-processed black-boned chicken is drained and placed in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for pre-freezing at -45℃ (cooling rate of -45℃ / h), and then held at -45℃ for 2 hours. The vacuum pump is then turned on, the vacuum degree is adjusted to 35Pa, and the temperature is directly raised to 25℃ and held at this temperature for 4.5 hours, with a heating rate of 22℃ / h, thus obtaining the wine-processed black-boned chicken freeze-dried product.

[0094] Comparative Example 5

[0095] The difference from Example 1 lies only in the freeze-drying step, which is as follows: The wine-processed black-boned chicken is drained and placed in a vacuum freeze dryer (Guangdong Lingjing Technology Co., Ltd., model 1.2-04, voltage 220V±10% 50HZ, power 1550W) for pre-freezing at -45℃ (cooling rate -45℃ / h). After reaching -45℃, the temperature is maintained for 2 hours. The vacuum pump is then turned on, and the vacuum degree is adjusted to 35Pa. The first, second, third, and fourth stages of heating are then performed to obtain the wine-processed black-boned chicken freeze-dried product.

[0096] First stage of heating: heating rate is 25℃ / h, heating to -36℃, and holding the temperature for 1h;

[0097] The second stage of heating: the heating rate is 2℃ / h, the temperature is raised to -25℃, and then held at a constant temperature for 0.5h;

[0098] The third stage of heating: the heating rate is 12℃ / h, the temperature is raised to -22℃, and then held at a constant temperature for 1h;

[0099] The fourth stage of heating: the heating rate is 22℃ / h, the temperature is raised to 25℃, and then kept constant for 2h.

[0100] I. Water activity of the freeze-dried black-boned chicken product in this invention

[0101] Test method:

[0102] The samples obtained from each example were cut into particles of 0.5cm×0.5cm×0.5cm. 2g of each particle was taken and the water activity was measured by a water activity meter. Each sample was measured three times. The results are summarized in the table below.

[0103] Table 1. Water activity of freeze-dried black-boned chicken in each example.

[0104] Example water activity Example 1 0.305 Example 2 0.342 Example 3 0.345 Example 4 0.336 Example 5 0.319 Comparative Example 1 0.410 Comparative Example 2 0.725 Comparative Example 3 0.836 Comparative Example 4 0.898 Comparative Example 5 0.677

[0105] Low water activity effectively inhibits the growth and reproduction of microorganisms. Typically, the optimal water activity for microbial growth is 0.7-0.75. In the embodiments of this invention, the freeze-dried black-boned chicken has a low water activity, effectively inhibiting microbial growth and reproduction, thereby extending the shelf life of the chicken. Simultaneously, the water activity of the freeze-dried black-boned chicken in this invention is between 0.3 and 0.35, effectively preventing an increase in hardness or viscosity after rehydration. In contrast, freeze-dried black-boned chicken obtained using non-gradient or non-specific parameter freeze-drying methods has a relatively high water activity, some even exceeding 0.75, indicating that it is not suitable for long-term storage.

[0106] II. Rehydration properties of the freeze-dried black-boned chicken product in this invention

[0107] Test method: The samples obtained from each example were placed in a 70℃ hot water bath and heated. They were removed every 30 seconds, the surface moisture was absorbed, and the mass was measured until the sample mass no longer changed. The rehydration time was recorded, and the rehydration ratio was calculated. The calculation method for the rehydration ratio is as follows:

[0108]

[0109] In the formula, R is the rehydration ratio;

[0110] m1 is the mass of the sample before rehydration, in grams;

[0111] m2 represents the mass of the sample after rehydration, in grams.

[0112] Each sample was tested three times, and the results are summarized in the table below.

[0113] Table 2 shows the rehydration time and rehydration ratio of freeze-dried black-boned chicken in each example.

[0114] Example Rehydration time (min) Rehydration ratio Example 1 <![CDATA[17.52±0.7 a ]]> <![CDATA[2.85±0.03 a ]]> Example 2 <![CDATA[22.13±0.8 a ]]> <![CDATA[2.49±0.05 a ]]> Example 3 <![CDATA[22.26±1.1 a ]]> <![CDATA[2.54±0.01 a ]]> Example 4 <![CDATA[19.77±0.5 a ]]> <![CDATA[2.73±0.06 a ]]> Example 5 <![CDATA[19.85±0.7 a ]]> <![CDATA[2.79±0.09 a ]]> Comparative Example 1 <![CDATA[40.61±1.2 b ]]> <![CDATA[2.35±0.02 b ]]> Comparative Example 2 <![CDATA[77.13±3.0 d ]]> <![CDATA[2.02±0.04 d ]]> Comparative Example 3 <![CDATA[70.69±3.5 d ]]> <![CDATA[1.94±0.06 d ]]> Comparative Example 4 <![CDATA[90.50±4.4 e ]]> <![CDATA[1.73±0.08 e ]]> Comparative Example 5 <![CDATA[50.32±1.9 c ]]> <![CDATA[2.11±0.03 c ]]>

[0115] (Note: Different letters in the table indicate significant differences between groups.)

[0116] III. Rehydration Texture of Freeze-Dried Black-Boned Chicken in this Invention

[0117] Experimental Method: Freeze-dried black-boned chicken from each example group was cut into 1cm×1cm×1cm particles. The hardness and adhesiveness of the chicken along the muscle fiber direction were measured using a food texture analyzer (25.4mm cylindrical probe, test force of 1400g, test speed of 1mm / s, two cycles of compression). Each sample was tested three times, and the results are summarized in the table below.

[0118] Table 3 shows the texture of the freeze-dried black-boned chicken after rehydration in each example.

[0119] Example Hardness (N) Adhesiveness (N) Example 1 <![CDATA[30.57±1.98 a ]]> <![CDATA[26.13±1.32 a ]]> Example 2 <![CDATA[35.43±2.11 a ]]> <![CDATA[29.69±1.24 a ]]> Example 3 <![CDATA[34.59±2.34 a ]]> <![CDATA[29.04±1.57 a ]]> Example 4 <![CDATA[33.62±2.63 a ]]> <![CDATA[27.52±1.59 a ]]> Example 5 <![CDATA[33.80±2.25 a ]]> <![CDATA[27.11±1.34 a ]]> Comparative Example 1 <![CDATA[41.36±3.63 b ]]> <![CDATA[37.51±2.36 b ]]> Comparative Example 2 <![CDATA[57.25±5.31 c ]]> <![CDATA[50.82±3.58 c ]]> Comparative Example 3 <![CDATA[68.37±5.25 d ]]> <![CDATA[62.94±6.59 d ]]> Comparative Example 4 <![CDATA[80.64±6.97 d ]]> <![CDATA[73.63±8.41 d ]]> Comparative Example 5 <![CDATA[70.59±4.89 d ]]> <![CDATA[65.30±6.36 d ]]>

[0120] (Note: Different letters in the table indicate significant differences between groups.)

[0121] As shown in Tables 2-3, the freeze-dried black-boned chicken of this invention has a short rehydration time and a high rehydration ratio, resulting in lower hardness and adhesiveness after rehydration. In contrast, the freeze-dried black-boned chicken of the comparative groups has a longer rehydration time, increasing the time required for use. Furthermore, the rehydrated products have higher hardness and adhesiveness, which will cause inconvenience during consumption and make it difficult to maintain a good taste.

[0122] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A freeze-drying method for black-boned chicken, characterized in that: Includes the following steps: (1) Pre-treatment: After slaughtering the black-boned chicken, remove the feathers, claws, internal organs and impurities, and cut it into pieces; (2) After mixing the pre-treated black-boned chicken with rice wine, steam it over water and drain the water; (3) Freeze-drying: After draining the water, the black-boned chicken is pre-frozen, and then the first stage of heating, the second stage of heating, the third stage of cooling and the fourth stage of heating are carried out to obtain the product. In step (3), the temperature of the first stage of heating is -40~-35℃ and is kept constant for 1-2 hours; the temperature of the second stage of heating is -25~-20℃ and is kept constant for 1-2 hours; the temperature of the third stage of cooling is -28~-25℃ and is kept constant for 0.5 hours; and the temperature of the fourth stage of heating is 20-25℃ and is kept constant for 1-2 hours. In step (3), the heating rate of the first stage is 20-25℃ / h, the heating rate of the second stage is 10-15℃ / h, the cooling rate of the third stage is -2 to -4℃ / h, and the heating rate of the fourth stage is 20-25℃ / h; the vacuum degree during the first stage heating, the second stage heating, the third stage cooling and the fourth stage heating is 30-50Pa.

2. The freeze-drying method according to claim 1, characterized in that: The steaming time in step (2) is 1.4-1.7 hours.

3. The freeze-drying method according to claim 2, characterized in that: The steaming time in step (2) is 1.5 hours.

4. The freeze-drying method according to claim 1, characterized in that: The weight ratio of black-boned chicken and rice wine in step (2) is (2-8):

1.

5. The freeze-drying method according to claim 4, characterized in that: The weight ratio of black-boned chicken and rice wine in step (2) is 5:

1.

6. The freeze-drying method according to claim 1, characterized in that: In step (3), the pre-freezing temperature is -50~-40℃, the cooling rate is -40~50℃ / h, and the constant temperature is maintained for 1-3h.

7. The freeze-drying method according to claim 1, characterized in that: In step (3), the temperature of the first stage of heating is -37~-35℃ and is kept constant for 1-1.5h; the temperature of the second stage of heating is -24~-21℃ and is kept constant for 1-1.5h; the temperature of the third stage of cooling is -26~-25℃ and is kept constant for 0.5h; and the temperature of the fourth stage of heating is 22-25℃ and is kept constant for 1.5-2h.

8. Freeze-dried black-boned chicken prepared by the freeze-drying method according to any one of claims 1-7.

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