Phosphorus-free green composite water-holding agent for improving quality of chicken feet and application method of phosphorus-free green composite water-holding agent

Abstract

The invention discloses a non-phosphorus green composite water holding agent for improving the quality of chicken feet and an application method of the non-phosphorus green composite water holding agent, and belongs to the technical field of food processing. The raw materials of the non-phosphorus green composite water-holding agent comprise a dissociation water-holding agent and a crosslinking water-holding agent, and sodium bicarbonate provides an alkaline environment, so that protein is negatively charged, and electrostatic repulsion among carboxyl groups is increased. And collagen can be dissociated, the water binding capacity of meat is increased, the tenderness of the meat is improved, the bulkiness of the meat is increased, the protein network structure of the treated chicken feet is looser, and the water binding capacity is remarkably enhanced. Transglutaminase can catalyze cross-linking of glutamine and lysine in protein to form a tight three-dimensional network to physically wrap moisture; the protein structure can be stretched, hydrophilic groups are exposed, and the binding force with water is enhanced; meanwhile, combination of muscle fibers and collagen is strengthened, and the structure is stabilized. In addition, water loss caused by high temperature, freezing and the like in processing can be resisted, the succulent property and elasticity of meat are improved, and therefore the water-retaining property is improved.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a phosphorus-free green composite water-retaining agent for improving the quality of chicken feet and its application method. Background Technology

[0002] In Chinese cuisine, poultry is the second most consumed type of meat. Chicken meat is the most important component of poultry, and chicken feet are a byproduct of chicken processing, containing skin, bones, muscle, and collagen. Therefore, processing low-cost chicken byproducts into high-value chicken feet products can significantly improve economic efficiency. However, during cooking (such as braising, frying, or steaming), chicken feet lose water due to high temperatures, leading to muscle tissue contraction and protein denaturation, damaging cell structure, and accelerating water loss. Dehydrated chicken feet become dry, hard, and difficult to chew, lacking elasticity and juiciness, with a significantly reduced texture, and may even be "dry, hard, and difficult to swallow," affecting the consumer experience.

[0003] Traditional methods for improving the tenderness and water retention of chicken feet involve using phosphorus-containing water-retaining agents. While these agents, such as sodium tripolyphosphate, can improve food texture, excessive use can hinder the absorption of minerals like calcium and iron, increase the metabolic burden on the kidneys, and cause eutrophication of water bodies due to industrial wastewater discharge, exacerbating ecological problems such as algal blooms. Furthermore, the misuse of phosphorus-containing water-retaining agents by some companies has led to excessive food residues, resulting in domestic and international regulatory restrictions and trade barriers. Against this backdrop, consumer demand for "clean label" foods has surged, prompting the industry to shift towards the research and development of green additives. Phosphorus-free water-retaining agents, primarily composed of green and healthy materials such as sodium bicarbonate and TG enzymes, combine water retention with environmentally friendly properties. They can meet the needs of food processing while reducing ecological pollution. Technological breakthroughs in this area have become an urgent need for the sustainable development of the food industry and a key direction for addressing consumption upgrades and international competition.

[0004] The patent "A Composite Water-Retaining Agent for Improving Bullfrog Quality and Its Application" (Application No.: 2019100482026) uses a compound of polyphosphate and sodium bicarbonate, employing a phosphorus-containing water-retaining agent and only considering the dissociation effect of sodium bicarbonate. This not only fails to meet the requirements of green and healthy practices but also neglects the use of cross-linking methods. The article "Research on the Influence Mechanism of Carrageenan on the Texture and Water Retention of Meat Products" (Lin Ruijun, 2025) studies the mechanism of carrageenan on the water retention of meat products, but only investigates the effect of carrageenan cross-linking on water retention. The water retention method is relatively simple and has certain limitations. The patent "A Water Retention Process for Fresh Meat" (Application No.: 2017107256667) uses a method of simultaneously compounding and soaking multiple different dissociation water-retaining agents and multiple different cross-linking water-retaining agents. Although a variety of water-retaining agents are used, the order of dissociation followed by cross-linking is not considered, nor is the optimal timing of adding the cross-linking agent considered, thus exhibiting limitations.

[0005] This patent not only employs a method of first dissociating and then crosslinking, but also identifies the optimal concentration of the dissociating agent and the optimal time for crosslinking. For the first time, pH is used to determine the degree of dissociation of chicken foot collagen before crosslinking, achieving a synergistic effect of "dissociating agent + crosslinking agent" ("1+1>2"), thus obtaining the optimal solution for water retention in chicken feet.

[0006] By improving water retention through acid-base dissociation and further chemical cross-linking, moisture loss during cooking can be reduced, muscle fiber expansion can be maintained, and the meat can be made more tender, juicy and elastic. While retaining the original flavor, tenderness is enhanced, making braised chicken feet soft and flavorful, and pickled chicken feet crisp and juicy, fundamentally optimizing the texture after cooking. Summary of the Invention

[0007] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, to avoid obscuring the purpose of these documents; however, such simplifications or omissions should not be construed as limiting the scope of the invention.

[0008] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0009] Therefore, the purpose of this invention is to overcome the shortcomings of the prior art and provide a phosphorus-free green composite water-retaining agent to improve the quality of chicken feet.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solutions, including:

[0011] By mass fraction, the phosphorus-free green composite water-holding agent comprises 0.05% to 2.5% of a dissociative water-holding agent, 0.5% to 4.0% of a cross-linking water-holding agent, and the remainder being water.

[0012] As a preferred embodiment of the phosphorus-free green composite water-holding agent for improving chicken feet quality according to the present invention, the dissociative water-holding agent includes one or more of sodium bicarbonate, sodium citrate, bromelain, papain, citric acid, and lactic acid bacteria metabolites.

[0013] As a preferred embodiment of the phosphorus-free green composite water-holding agent for improving chicken feet quality according to the present invention, the lactic acid bacteria metabolite is a liquid metabolite obtained by inoculating 0.5% to 2.5% (w / w) of Lactobacillus plantarum into a simple culture medium and fermenting it at 40°C for 18 hours; wherein the simple culture medium is formulated with 1% glucose (w / w), 1% beef peptone (w / w), and the remainder being purified water.

[0014] As a preferred embodiment of the phosphorus-free green composite water-holding agent for improving chicken feet quality according to the present invention, the cross-linking water-holding agent includes one or more of transglutaminase, laccase, carrageenan, L-arginine, and tea polyphenols.

[0015] The purpose of this invention is to overcome the shortcomings of the prior art and provide an application of a phosphorus-free green composite water-retaining agent for improving the quality of chicken feet in chicken foot treatment.

[0016] As a preferred embodiment of the application of the phosphorus-free green composite water-retaining agent for improving chicken feet quality described in this invention in chicken feet treatment, it includes:

[0017] Pre-treatment: Wash the chicken feet and trim the nails;

[0018] Phosphorus-free green composite water-retaining agent treatment: Soak chicken feet in a solution of dissociative water-retaining agent, wipe them dry, and then soak them in a solution of cross-linking water-retaining agent.

[0019] Post-processing: Place the processed chicken feet in boiling water, steam, and then remove.

[0020] As a preferred embodiment of the application of the phosphorus-free green composite water-holding agent for improving chicken feet quality described in this invention in chicken feet treatment, the lactic acid bacteria metabolite refers to the liquid metabolite of 0.5% to 2.5% Lactobacillus plantarum fermented at 40°C for 18 hours. The chicken feet are soaked in this metabolite without adding water. The concentration of the aqueous solution of the dissociative water-holding agent is 0.05% to 2.5%.

[0021] As a preferred embodiment of the application of the phosphorus-free green composite water-retaining agent for improving chicken feet quality described in this invention in chicken feet treatment, wherein the concentration of the cross-linked water-retaining agent aqueous solution is 0.5% to 4.0%.

[0022] As a preferred embodiment of the application of the phosphorus-free green composite water-retaining agent for improving chicken feet quality described in this invention in chicken feet treatment, the soaking time of the dissociative water-retaining agent is 0.5 to 5 hours; and the soaking time of the crosslinking water-retaining agent is 0.5 to 3 hours.

[0023] As a preferred embodiment of the application of the phosphorus-free green composite water-retaining agent for improving chicken feet quality described in this invention in the treatment of chicken feet, wherein the soaking temperature is 25℃~50℃.

[0024] As a preferred embodiment of the application of the phosphorus-free green composite water-retaining agent for improving chicken feet quality described in this invention in the treatment of chicken feet, wherein the cooking time is 8 to 10 minutes.

[0025] Beneficial effects of this invention:

[0026] This invention targets the structural characteristics of chicken feet's own muscle tissue and studies the effective components that have the best water-holding effect on chicken feet. Further experiments were conducted on these effective components to obtain the optimal formula. Through a treatment method of first dissociation and then cross-linking, the final chicken feet obtained are of excellent quality and have significantly improved water-holding capacity. The cooking loss rate of chicken feet treated with this composite water-holding agent is significantly reduced during the cooking process.

[0027] Chicken feet treated with the water-holding agent of this invention show a significant improvement in taste and quality. On the one hand, dissociative water-holding agents (such as sodium bicarbonate) disrupt the tight structure of collagen and myofibrils, making the meat more fluffy, increasing water retention and improving tenderness. On the other hand, cross-linking water-holding agents (such as transglutaminase) form a three-dimensional network structure, fixing free water and enhancing structural stability, making the chicken feet juicier and more elastic after treatment. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein:

[0029] Figure 1 A schematic diagram showing the cooking loss rate after soaking in 1.0% sodium bicarbonate (dissociation agent) for 2.5 h and then soaking in different concentrations of TG enzyme (crosslinking agent) for 60 min.

[0030] Figure 2 A schematic diagram showing the cooking loss rate after soaking in sodium bicarbonate (dissociation agent) of different concentrations for 60 minutes;

[0031] Figure 3 A schematic diagram showing the pH values ​​of sodium bicarbonate (dissociation agent) at different concentrations;

[0032] Figure 4 A schematic diagram showing the cooking loss rate after soaking in sodium citrate (dissociation agent) of different concentrations for 60 minutes;

[0033] Figure 5 A schematic diagram showing the pH values ​​of sodium citrate (dissociation agent) at different concentrations;

[0034] Figure 6 A schematic diagram showing the cooking loss rate after soaking in different concentrations of papain (dissociation agent) for 60 minutes;

[0035] Figure 7 A schematic diagram showing the cooking loss rate after soaking in different concentrations of bromelain (dissociation agent) for 60 minutes;

[0036] Figure 8 A schematic diagram showing the cooking loss rate after soaking in different concentrations of citric acid (dissociation agent) for 60 minutes;

[0037] Figure 9 A schematic diagram showing the pH values ​​of different concentrations of citric acid (dissociation agent);

[0038] Figure 10 A schematic diagram showing the cooking loss rate after soaking in different concentrations of lactic acid bacteria metabolites (dissociation agents) for 60 minutes;

[0039] Figure 11 A schematic diagram showing the pH values ​​of different concentrations of lactic acid bacteria metabolites (dissociation agents) after fermentation at 40℃ for 18 hours;

[0040] Figure 12 A schematic diagram showing the cooking loss rate results of soaking in 1% sodium bicarbonate (dissociation agent) for different times.

[0041] Figure 13 A schematic diagram showing the cooking loss rate after soaking in 1.0% sodium bicarbonate (dissociation agent) for 2.5 h and then soaking in laccase (crosslinking agent) of different concentrations for 60 min.

[0042] Figure 14 A schematic diagram showing the cooking loss rate of carrageenan (crosslinking agent) at different concentrations after soaking in 1.0% sodium bicarbonate (dissociation agent) for 2.5 h for 60 min;

[0043] Figure 15 A schematic diagram showing the cooking loss rate after soaking in 1.0% sodium bicarbonate (dissociation agent) for 2.5 h and then soaking in L-arginine (crosslinking agent) of different concentrations for 60 min.

[0044] Figure 16 A schematic diagram showing the cooking loss rate of tea polyphenols (crosslinking agents) at different concentrations after soaking in 1.0% sodium bicarbonate (dissociation agent) for 2.5 h for 60 min;

[0045] Figure 17 A schematic diagram showing the cooking loss rate after soaking in 2.5% Lactobacillus plantarum metabolites (dissociation agent) for 2.5 h and then soaking in different concentrations of TG enzyme (crosslinking agent) for 60 min. Detailed Implementation

[0046] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the examples in the specification.

[0047] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0048] Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that is mutually exclusive with other embodiments.

[0049] Unless otherwise specified, all raw materials used in this invention are commercially available.

[0050] Example 1

[0051] This embodiment provides a phosphorus-free, green composite water-retaining agent for improving chicken feet quality and its application, specifically:

[0052] Formula: 1% dissociative water-holding agent (sodium bicarbonate) and 0.5-4% cross-linking water-holding agent (transglutaminase).

[0053] Application method:

[0054] (1) Pre-treatment of chicken feet: Wash the chicken feet and cut off the nails;

[0055] (2) Treatment with phosphorus-free green composite water-holding agent: First, soak in 1% sodium bicarbonate aqueous solution at room temperature for 2.5h, take it out and wipe off the water, then soak in 0.5%, 1.0%, 1.5%, 2.0%, 2.5%, 3.0%, 3.5%, and 4.0% TG enzyme aqueous solution at 50℃ for 1h.

[0056] (3) Post-processing of chicken feet: After processing, place the chicken feet in boiling water and steam for 8-10 minutes before taking them out.

[0057] The chicken feet obtained above were subjected to a cooking loss test, and the results are as follows: Figure 1 As shown, chicken feet treated with this phosphorus-free green composite water-holding agent formula at a transglutaminase concentration of 2.5% showed the lowest cooking loss, significantly lower than the control group.

[0058] Comparative Example 1

[0059] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is 0, and the amount of dissociative water-holding agent (sodium bicarbonate) added is 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, respectively. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0060] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 2 As shown, chicken feet treated with this dissociation water-holding agent formulation at a concentration of 1.0% showed the lowest cooking loss, significantly lower than the control group.

[0061] Comparative Example 2

[0062] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is adjusted to 0, and the amount of dissociative water-holding agent added is sodium citrate, which is 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, respectively. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0063] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 4 As shown, chicken feet treated with this dissociation water-holding agent formulation at a concentration of 0.5% showed the lowest cooking loss, significantly lower than the control group.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is adjusted to 0, and the amount of dissociation water-holding agent added is papain, which is 0.05%, 0.10%, 0.15%, 0.20%, and 0.25%, respectively. The mixture is soaked at 55°C, and the rest of the preparation process is the same as in Example 1, thus producing chicken feet.

[0066] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 6 As shown, chicken feet treated with this dissociation water-holding agent formulation at a concentration of 0.25% showed the lowest cooking loss, which was lower than that of the control group.

[0067] Comparative Example 4

[0068] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is adjusted to 0, and the amount of dissociative water-holding agent is bromelain, with addition amounts of 0.05%, 0.10%, 0.15%, 0.20%, and 0.25%, respectively. The mixture is soaked at 55°C, and the rest of the preparation process is the same as in Example 1, resulting in chicken feet.

[0069] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 7 As shown, the cooking loss of chicken feet treated with this dissociation water-holding agent formulation was higher than that of the control group at all concentrations.

[0070] Comparative Example 5

[0071] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is adjusted to 0, and the amount of dissociative water-holding agent is citric acid, with addition amounts of 0.1%, 0.2%, 0.3%, 0.4%, and 0.5%, respectively. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0072] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 8 As shown, chicken feet treated with this dissociation water-holding agent formulation had the lowest cooking loss at 0.2%, which was lower than that of the control group.

[0073] Comparative Example 6

[0074] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added is adjusted to 0, and the amount of dissociation water-holding agent is a lactic acid bacteria metabolite added at 0.5%, 1.0%, 1.5%, 2.0%, and 2.5%, respectively. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0075] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 10 As shown, chicken feet treated with this dissociation water-holding agent formulation had the lowest cooking loss at 2.5%, which was lower than that of the control group.

[0076] Comparative Example 7

[0077] The difference between this comparative example and Example 1 is that the amount of cross-linking water-holding agent added was adjusted to 0, and the amount of dissociative water-holding agent (sodium bicarbonate) added was 1.0%, with treatment times of 0.5h, 1h, 1.5h, 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, and 5h, respectively. All other preparation processes were the same as in Example 1, yielding chicken feet.

[0078] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 12 As shown, chicken feet treated with this dissociation water-holding agent formulation showed the lowest cooking loss at a concentration of 1% and a soaking time of 2.5 hours, which was significantly lower than that of the control group.

[0079] Example 2

[0080] The difference between this embodiment and Example 1 is that the type of cross-linking water-holding agent is changed to laccase, while the rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0081] The obtained chicken feet were subjected to a cooking loss test, and the results are as follows: Figure 13 As shown, chicken feet treated with this phosphorus-free green composite water-retaining agent formula at a concentration of 0.5% showed the lowest cooking loss, significantly lower than the control group.

[0082] Example 3

[0083] The difference between this embodiment and Example 1 is that the type of cross-linking water-holding agent is changed to carrageenan, while the rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0084] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 14 As shown, chicken feet treated with this phosphorus-free green composite water-retaining agent formula at a concentration of 0.5% showed the lowest cooking loss, significantly lower than the control group.

[0085] Example 4

[0086] The difference between this embodiment and Example 1 is that the type of cross-linking water-holding agent is changed to L-arginine, and the chicken feet are soaked at room temperature. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0087] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 15 As shown, chicken feet treated with this phosphorus-free green composite water-retaining agent formula at a concentration of 0.5% showed the lowest cooking loss, significantly lower than the control group.

[0088] Example 5

[0089] The difference between this embodiment and Example 1 is that the type of cross-linking water-holding agent is adjusted to tea polyphenols, with concentrations of 0.2%, 0.5%, 0.8%, 1.0%, and 1.2%, respectively. The rest of the preparation process is the same as in Example 1, and chicken feet are obtained.

[0090] The obtained chicken feet were subjected to a cooking loss test, and the results were as follows: Figure 16 As shown, chicken feet treated with this phosphorus-free green composite water-retaining agent formula at a concentration of 0.8% showed the lowest cooking loss, significantly lower than the control group.

[0091] Example 6

[0092] The liquid metabolites were obtained by inoculating 2.5% (w / w) of Lactobacilus plantarum into a simple culture medium (1% glucose (w / w), 1% beef peptone (w / w), and the remainder being purified water) and fermenting at 40°C for 18 hours.

[0093] The difference between this embodiment and Example 1 is that the dissociative water-holding agent is changed to *Lactobacillus plantarum* metabolite (no dilution required, direct soaking); the cross-linking water-holding agent is TG enzyme. The remaining preparation process is the same as in Example 1, yielding chicken feet.

[0094] The obtained chicken feet were subjected to a cooking loss test, and the specific results are as follows: Figure 17 As shown, chicken feet treated with this phosphorus-free green composite water-holding agent formula had the lowest cooking loss at a TG enzyme concentration of 1.5%, which was significantly lower than that of the control group.

[0095] This invention targets the structural characteristics of chicken feet's own muscle tissue and studies the effective components that have the best water-holding effect on chicken feet. Further experiments on these effective components have yielded the optimal formula, resulting in chicken feet of excellent quality. On the one hand, it improves the solubility of myofibril proteins and increases the solubility of actomyosin; on the other hand, it increases the tenderness of the meat, making the collagen network structure of the chicken feet more porous after processing, significantly enhancing water-holding capacity, and also improving the tenderness of the meat.

[0096] The phosphorus-free green composite water-holding agent prepared in this invention comprises dissociative water-holding agents and cross-linking water-holding agents. The dissociative water-holding agent improves meat quality primarily by disrupting the tight structure of collagen and myofibrils, exposing hydrophilic groups (such as amino and carboxyl groups), and enhancing hydration capacity. Sodium bicarbonate is optimal, as it provides an alkaline environment, giving proteins a negative charge and increasing electrostatic repulsion between carboxyl groups. It also dissociates collagen, increasing meat water-holding capacity, improving tenderness, and increasing meat bulkiness, resulting in a more porous protein network structure and significantly enhanced water-holding capacity in chicken feet after treatment. The cross-linking water-holding agent improves meat quality primarily by forming a three-dimensional network structure through chemical or enzymatic cross-linking, fixing free water, and enhancing structural stability. Transglutaminase is optimal, as it catalyzes the cross-linking of glutamine and lysine in proteins, forming a tight three-dimensional network that physically encapsulates water; it also allows the protein structure to expand, exposing hydrophilic groups and enhancing water binding; simultaneously, it strengthens the binding of muscle fibers and collagen, stabilizing the structure. In addition, it can resist moisture loss caused by high temperature and freezing during processing, improve the juiciness and elasticity of meat, and thus enhance water retention.

[0097] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A phosphorus-free, green, composite water-retaining agent for improving the quality of chicken feet, characterized in that: By mass fraction, the phosphorus-free green composite water-holding agent comprises 0.05% to 2.5% of a dissociative water-holding agent, 0.5% to 4.0% of a cross-linking water-holding agent, and the remainder being water.

2. The phosphorus-free green composite water-retaining agent for improving chicken feet quality as described in claim 1, characterized in that: The dissociative water-holding agents include one or more of sodium bicarbonate, sodium citrate, bromelain, papain, citric acid, and lactic acid bacteria metabolites.

3. The phosphorus-free green composite water-retaining agent for improving chicken feet quality as described in claim 2, characterized in that: The lactic acid bacteria metabolite is a liquid metabolite produced by inoculating 0.5% to 2.5% (w / w) of Lactobacillus plantarum into a simple culture medium and fermenting it at 40°C for 18 hours; wherein the simple culture medium is formulated with 1% glucose (w / w), 1% beef peptone (w / w), and the remainder being purified water.

4. The phosphorus-free green composite water-retaining agent for improving chicken feet quality as described in claim 1, characterized in that: The cross-linking water-holding agent includes one or more of transglutaminase, laccase, carrageenan, L-arginine, and tea polyphenols.

5. The application of the phosphorus-free green composite water-retaining agent as described in any one of claims 1 to 4 in the treatment of chicken feet.

6. The application of the phosphorus-free green composite water-retaining agent as described in claim 5 in the treatment of chicken feet, characterized in that: include, Pre-treatment: Wash the chicken feet and trim the nails; Phosphorus-free green composite water-retaining agent treatment: Soak chicken feet in a solution of dissociative water-retaining agent, wipe them dry, and then soak them in a solution of cross-linking water-retaining agent. Post-processing: Place the processed chicken feet in boiling water, steam, and then remove.

7. The application of the phosphorus-free green composite water-retaining agent as described in claim 6 in the treatment of chicken feet, characterized in that: The concentration of the aqueous solution of the dissociative water-holding agent is 0.05% to 2.5%; the concentration of the aqueous solution of the crosslinking water-holding agent is 0.5% to 4.0%.

8. The application of the phosphorus-free green composite water-retaining agent as described in claim 6 in the treatment of chicken feet, characterized in that: The soaking time for the dissociative water-holding agent is 0.5 to 5 hours; the soaking time for the crosslinking water-holding agent is 0.5 to 3 hours.

9. The application of the phosphorus-free green composite water-retaining agent as described in claim 6 in the treatment of chicken feet, characterized in that: The soaking temperature is 25℃~50℃.

10. The application of the phosphorus-free green composite water-retaining agent as described in claim 6 in the treatment of chicken feet, characterized in that: The steaming time is 8 to 10 minutes.

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