A quality improver, improver solution, and improver method for frozen chicken feet.

Abstract

This invention discloses a quality improver, an improving solution, and an improving method for frozen chicken feet. The improver comprises the following components in parts by weight: 20-100 parts sodium carbonate, 20-100 parts sodium citrate, and 16-80 parts soy protein isolate. This invention also provides an improving solution containing the improver. The improver and improving solution of this invention can effectively inhibit the mechanical damage of ice crystals to the myofibril network and the denaturation of proteins during freezing, thereby maximizing the retention of bound water and reducing juice loss during the freezing-thawing process. Therefore, it can endow chicken feet with both high soaking weight gain and low thawing loss rate, synergistically demonstrating excellent water absorption and retention capacity and resistance to freezing denaturation. The improver and improving solution of this invention can significantly improve the processing yield of frozen chicken feet and improve their juiciness and tenderness, and are particularly suitable for the processing of frozen raw chicken feet and frozen cooked chicken feet, possessing good industrial application value.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and specifically relates to a quality improver, a improver solution, and a improver method for frozen chicken feet. Background Technology

[0002] Cooked chicken feet are a typical deep-processed product in the leisure braised food and pickled chicken feet industry. Currently, the mainstream production and distribution model in the industry is to freeze and store them after cooking to achieve long-distance transportation and cross-seasonal sales. However, this model has a prominent problem of quality deterioration: chicken feet have fine muscle fibers and relatively high content of connective tissue and fat. During freezing, the water inside the muscle forms ice crystals in situ. The continuous growth and secondary crystallization of ice crystals cause irreversible mechanical damage to the myofibril network, leading to muscle fiber contraction, protein denaturation and aggregation, and a series of problems such as a large loss of juice, dry and hardened meat, and a significant decrease in elasticity and crispness. This not only directly reduces the product yield and the economic benefits of enterprises, but also seriously restricts the quality stability of the product during its shelf life and consumers' willingness to repurchase.

[0003] Water retention is a core indicator for evaluating the quality of frozen meat products, and it directly determines the juiciness and texture of the product. From the perspective of meat science mechanisms, muscle water exists in three states: bound water, fixed water, and free water. Among them, fixed water, which accounts for up to 85%, is bound by the capillary forces and electrostatic interactions of the myofibril network and is the key component determining the juiciness of the product. The ice crystal compression, protein oxidation, and structural deterioration caused by freezing disrupt the integrity of the myofibril protein network, causing fixed water to convert into easily lost free water. Modern research has clarified that the water-holding capacity of meat products is synergistically regulated by three core factors: ① Net charge of protein—the isoelectric point of myofibrillar protein is pH 5.0–5.5. A pH deviation from the isoelectric point can increase the negative charge density on the protein surface, increase the electrostatic repulsion between molecules, and expand the water-holding space of the protein network; ② Ionic strength of the system—different ions follow the Hofmeister sequence to affect protein solubility and hydration capacity. Specific carbonate and citrate anions can stabilize protein conformation and enhance water-holding effect; ③ Structural integrity of myofibrillar protein—the fibrous network composed of myosin and actin relies on intermolecular forces such as hydrogen bonds and hydrophobic interactions to retain water. Once the protein is oxidized or denatured, the exposure of hydrophilic groups decreases, and the water-holding capacity is greatly reduced.

[0004] Currently, mainstream industrial water-retaining agents still primarily utilize phosphates such as sodium tripolyphosphate and sodium hexametaphosphate. These agents achieve good short-term water retention by chelating metal ions and dissociating the dense protein network of actomyosin. However, excessive intake can disrupt calcium and phosphorus metabolism in the human body. Furthermore, GB 2760 continues to tighten regulations on the amount of phosphate added to meat products (maximum usage ≤ 5.0 g / kg, calculated as phosphate). Against this backdrop, the development of phosphate-free water-retaining agents has become an urgent need and an inevitable direction for the transformation and upgrading of the meat processing industry.

[0005] Existing phosphate-free water-retaining agents are divided into three categories: alkaline salts, natural polysaccharides, and plant proteins. Among them, carbonates and sodium citrate can adjust pH and improve protein hydration, but when used alone, they cause severe water loss during frozen storage; polysaccharides such as carrageenan and xanthan gum have large molecular weights and are difficult to penetrate deep into the tissues of chicken feet; soy protein isolate is hydrophilic and can lock in water and reduce ice crystal damage, but it has no ability to chelate metal ions, so its weight gain effect is limited when used alone.

[0006] Although existing literature reports on the compounding of the above-mentioned components, such as CN106819898A which discloses a barbecue meat product and its preparation method, the barbecue meat product is composed of livestock and poultry meat, edible salt, white sugar, sodium tripolyphosphate, citric acid, sodium citrate, xanthan gum, carrageenan, soy protein, prickly ash gum, β-cyclodextrin, sodium carbonate, sodium bicarbonate, sodium D-isoascorbate, spices, smoking materials, and water. Another example is CN104187791A which discloses a phosphate-free water-retaining agent to improve the texture and juiciness of processed meat products, including sodium bicarbonate, potassium carbonate, sodium citrate, cyclodextrin, sodium alginate, carrageenan, and xanthan gum. However, existing solutions mainly target minced meat products or processed steaks, and their target components differ fundamentally from the high collagen matrix, dense connective tissue barrier, and low-permeability fiber structure of cooked chicken feet. Therefore, they cannot achieve simultaneous multi-dimensional intervention from water distribution regulation to protein conformation stabilization to ice crystal growth inhibition.

[0007] Therefore, there is currently a lack of a compound phosphate-free water-retaining formula and supporting processing technology for frozen cooked chicken feet that can completely replace phosphates, avoid food safety and regulatory risks, and simultaneously inhibit the deterioration of frozen storage quality from three levels: moisture state, protein physicochemical properties, and microstructure, so as to achieve a balance between high yield and long-term storage taste stability. This is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0008] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a quality improver, a improver solution, and a improver method for frozen chicken feet, in order to solve the problems existing in the prior art.

[0009] To achieve the above objectives, the present invention specifically adopts the following technical solution.

[0010] The first aspect of this invention protects a quality improver for frozen chicken feet, comprising the following components in parts by weight:

[0011] Sodium carbonate 20-100 parts

[0012] Sodium citrate 20-100 parts

[0013] 16-80 servings of soy protein isolate.

[0014] Another aspect of the present invention protects a quality-improving solution for frozen chicken feet, comprising the improver and solvent as described above.

[0015] Another aspect of the present invention protects the use of the improver or the improver solution described above in improving the quality of frozen chicken feet or in preparing products with improved quality of frozen chicken feet.

[0016] Another aspect of the present invention protects a method for improving the quality of frozen chicken feet, comprising the following steps:

[0017] Chicken feet are mixed with the improver or the improver solution described above and then frozen for preservation.

[0018] Another aspect of the present invention protects the improved chicken feet obtained by the improved method described above.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] 1) The modifier and modified solution of this invention are a ternary phosphorus-free compound system formed by sodium carbonate, sodium citrate, and soy protein isolate. The three components work synergistically to retain water. Sodium carbonate increases the negative charge on the surface of muscle protein, loosening the myofibril network and thus expanding the water storage space; sodium citrate reduces oxidation by chelating metal ions; and soy protein isolate adsorbs and fixes water using its hydrophilic groups. After treatment with the modifier, modified solution, and modified method of this invention, the weight gain of the modified chicken feet after soaking is no less than 25%, significantly improving the product yield compared to the water control group. Simultaneously, the thawing loss rate after 30 days of frozen storage is no more than 8.5%, indicating that the modifier, modified solution, and modified method of this invention can effectively alleviate the problem of juice loss caused by ice crystal formation during frozen storage of chicken feet, significantly improving the frozen storage stability of chicken feet.

[0021] 2) The modifier, modified solution, and modified method of this invention can effectively delay the lipid oxidation and protein degradation of chicken feet during frozen storage, maintaining their crisp and elastic texture for a long time. Chicken feet treated with the modifier and modified solution of this invention showed significantly lower TBARS content at the end of frozen storage compared to the water control group, indicating a significant reduction in lipid oxidation. The decrease in myofibril protein solubility was effectively alleviated, and thiol oxidation loss was significantly inhibited, thus protecting protein function. At the protein secondary structure level, the proportion of stable β-sheet structures increased in chicken feet treated with the modifier and modified solution of this invention, indicating its ability to maintain the integrity of protein conformation. Histological observation further confirmed that muscle fibers and connective tissue were more regularly arranged and less damaged, indicating protection of muscle microstructure. The synergistic effect of anti-oxidation, anti-degradation, and structural protection ensures that the elasticity of chicken feet remains high at the end of frozen storage, maximizing the preservation of the product's original juicy taste and crisp texture.

[0022] 3) The modifier and modified solution of this invention do not contain any phosphates, which meets the development requirements of clean label food; the chicken feet are soaked in a constant temperature process without the need for special large equipment, and the operation is simple and easy to implement, making it suitable for large-scale production line processing of frozen raw chicken feet and frozen cooked chicken feet. Attached Figure Description

[0023] Figure 1 The figure shows the effect of 2.0, 4.0, 6.0, 8.0, and 10.0 g / L sodium carbonate aqueous solutions on the soaking weight gain and thawing loss rate of chicken feet in Example 1 of the present invention.

[0024] Figure 2 The figure shows the effect of 2.0, 4.0, 6.0, 8.0, and 10.0 g / L sodium citrate aqueous solutions on the soaking weight gain and thawing loss rate of chicken feet in Example 1 of the present invention.

[0025] Figure 3 The figure shows the effect of 1.6, 3.2, 4.8, 6.4, and 8.0 g / L soy protein isolate aqueous solutions on the soaking weight gain and thawing loss rate of chicken feet in Example 1 of the present invention.

[0026] Figure 4 The graph shows the changes in the soaking weight gain rate of chicken feet in the SC treatment group and SCP treatment group in Example 2 of the present invention.

[0027] Figure 5 The graph shows the changes in the thawing loss rate of chicken feet in the SC treatment group and SCP treatment group during frozen storage in Example 2 of the present invention.

[0028] Figure 6 The image shows the T2 relaxation spectra of chicken feet from the SC treatment group and SCP treatment group during frozen storage in Example 2 of the present invention.

[0029] Figure 7 The diagram shows the moisture distribution of chicken feet in the SC treatment group and SCP treatment group during frozen storage in Example 2 of the present invention.

[0030] Figure 8 The diagram shows the change in elasticity of chicken feet in the SC treatment group and SCP treatment group during frozen storage in Embodiment 2 of the present invention.

[0031] Figure 9 The graph shows the changes in TBARS content in chicken feet from the SC and SCP treatment groups during frozen storage in Example 2 of this invention.

[0032] Figure 10 The graph shows the changes in myofibrillar protein solubility in chicken feet from the SC and SCP treatment groups during frozen storage, as shown in Example 2 of this invention.

[0033] Figure 11 The graph shows the changes in myofibrillar protein thiol content in chicken feet from the SC and SCP treatment groups during frozen storage in Example 2 of this invention.

[0034] Figure 12 The image shown is an infrared spectrum of myofibrillar protein in chicken feet from the SC and SCP treatment groups during frozen storage, as shown in Example 2 of this invention.

[0035] Figure 13 The diagram shows the changes in the secondary structure of myofibril proteins in chicken feet from the SC and SCP treatment groups during frozen storage, as shown in Example 2 of this invention.

[0036] Figure 14 The image shown is an HE staining image of the control group in Example 2 of the present invention before freezing.

[0037] Figure 15 The images shown are HE staining images of chicken feet samples with different treatments after being frozen for 30 days in Example 2 of this invention. In the images, a represents the control group, b represents the SC group, and c represents the SCP group. Detailed Implementation

[0038] Existing technologies record that the thawing loss rate of fresh pork and beef is only 3%~7%, and that of cooked poached chicken pieces is about 3-5%, while the thawing loss rate of cooked chicken feet can reach 13%~18%. Chicken feet are mainly composed of loose collagen connective tissue with a very low proportion of muscle fibers. Ice crystals during freezing easily tear the collagen network, resulting in water loss far exceeding that of pork, beef, and other livestock and poultry meat. The processing significantly damages the epidermis and tendons, creating numerous channels for water leakage. During processing, chicken feet need to be soaked for a long time to absorb water, resulting in a high free water content in the tissue, which is more easily converted into lost water during long-term freezing. Ordinary meat products have a dense protein structure and do not undergo deep water absorption processes, thus having a lower risk of water loss. After the collagen in chicken feet oxidizes, it becomes soft and sticky, and water loss simultaneously destroys the crisp and chewy core texture. High thawing losses significantly reduce product yield and lead to significant economic losses. Therefore, compared to other meat products, chicken feet have a more urgent need for water retention treatment.

[0039] To address the aforementioned problems, the inventors conducted preliminary screening and evaluation of 10 substances, including sodium bicarbonate, sodium carbonate, sodium citrate, sodium chloride, carrageenan, guar gum, xanthan gum, curdlan gum, sodium alginate, and soy protein isolate. Using chicken feet as the treatment target, the water retention effects of each substance were compared using soaking weight gain and thawing loss rates as evaluation indicators. The results showed that sodium carbonate, sodium citrate, and soy protein isolate, while imparting a higher soaking weight gain rate, exhibited a lower thawing loss rate, and their overall water retention performance was significantly better than the other seven substances; therefore, they were identified as candidate target improvers.

[0040] Based on this, the inventors further conducted single-factor optimization experiments on the addition concentrations of sodium carbonate, sodium citrate, and soy protein isolate, and determined the appropriate addition amounts of the three substances respectively.

[0041] Subsequently, to explore the synergistic effect of the three, the inventors adopted L9(3 3 An orthogonal experimental design was used to investigate the three substances, optimizing their compounding at three levels of appropriate addition. Through range analysis and variance analysis, the optimal ratio of sodium carbonate, sodium citrate, and soy protein isolate was finally selected.

[0042] Furthermore, to further elucidate the mechanism of action of the modifier and modified solution of this invention, the inventors systematically investigated their effects on the moisture distribution of chicken feet, the textural properties (elasticity), the degree of lipid oxidation (TBARS value), myofibril protein solubility, and the content of active thiol groups. Simultaneously, Fourier transform infrared spectroscopy (FTIR) analysis was used to explore changes in protein secondary structure, supplemented by HE staining of muscle tissue sections to observe microstructural changes.

[0043] Based on the above physicochemical indicators and microstructure characterization results, it is fully confirmed that the modifier and modified solution of this invention have significant quality improvement (water retention and elasticity maintenance) and antioxidant protection effects on chicken feet. Based on this, this invention was completed.

[0044] The first aspect of this invention protects a quality improver for frozen chicken feet, comprising the following components in parts by weight:

[0045] Sodium carbonate 20-100 parts

[0046] Sodium citrate 20-100 parts

[0047] 16-80 servings of soy protein isolate.

[0048] In the modifier of this invention, sodium carbonate and sodium citrate are alkaline substances. After dissolving in water, they can increase the negative charge on the surface of chicken feet proteins, enhance the electrostatic repulsion between molecules, and increase the water-retaining space. At the same time, they enhance the ionic strength in the solution, allowing water to enter the protein network through osmosis, thereby increasing the weight gain rate of chicken feet after soaking. In addition, treatment with the modifier of this invention can reduce the degree of freedom of bound water and fixed water in chicken feet during frozen storage, reduce water migration, increase the ratio of free water to fixed water, and form a network structure that can capture more water; improve the solubility of myofibrillar protein, delay protein denaturation; inhibit the reduction of sulfhydryl content in myofibrillar protein, reduce changes in protein conformation, and slow down protein degradation; increase the β-sheet structure of myofibrillar protein, promote more orderly cross-linking between proteins, reduce β-turns and unstable structures with random coils, maintain the stability of myofibrillar protein, thereby delaying water loss and quality deterioration of chicken feet during frozen storage. The improved chicken feet obtained after treatment with the modifier of the present invention have a thawing loss rate of no more than 8.5% after 30 days of frozen storage, which is far lower than the 13-18% reported in the prior art; and the soaking weight gain rate is no less than 25%.

[0049] In some embodiments, the sodium carbonate may be present in parts by weight of 20-60, 50-80, 70-100, or 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 parts. The sodium carbonate of this invention refers to a food additive produced using the soda ash process, ammonia-soda process, or natural alkali processing method. It is white or colorless and meets the requirements specified in GB 1886.1-2021 "National Food Safety Standard for Food Additives: Sodium Carbonate".

[0050] In some embodiments, the total alkali content of the sodium carbonate is ≥99.2 wt% on a dry basis.

[0051] In some embodiments, the sodium citrate can be in the following weight proportions: 20-60 parts, 50-80 parts, 70-100 parts, or 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, or 100 parts. The sodium citrate of this invention refers to sodium citrate obtained from starchy or sugary raw materials through fermentation and purification. It is white or colorless and meets the requirements specified in GB 1886.25-2016 "National Food Safety Standard for Food Additives: Sodium Citrate".

[0052] In some embodiments, the sodium citrate has a moisture content of 10-13 wt%.

[0053] In some embodiments, the soy protein isolate can be in the following weight proportions: 16-80 parts, 16-42 parts, 30-65 parts, 55-80 parts, or 16, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, or 80 parts. The soy protein isolate of this invention refers to a product obtained by extraction, concentration, separation, and refining processes to remove or partially remove non-protein components from soybean raw materials, and conforms to the provisions of GB20371-2016 "National Food Safety Standard for Plant Protein for Food Processing".

[0054] In some embodiments, the soy protein isolate contains ≥90g / 100g on a dry basis.

[0055] In some embodiments, the moisture content of the soy protein isolate is ≤10g / 100g.

[0056] Another aspect of the present invention protects a quality-improving solution for frozen chicken feet, comprising the improver and solvent as described above.

[0057] In some embodiments, the solvent is selected from water.

[0058] In some embodiments, the sodium carbonate content in the modifier is 2.0-10.0 g / L based on the total mass of the modified solution, and can also be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, or 10 g / L. Preferably, it is 4 g / L to 8 g / L.

[0059] In some embodiments, the sodium citrate content in the modifier is 2.0-10.0 g / L based on the total mass of the modified solution, and can also be 2 g / L, 3 g / L, 4 g / L, 5 g / L, 6 g / L, 7 g / L, 8 g / L, 9 g / L, or 10 g / L. Preferably, it is 4 g / L to 8 g / L.

[0060] In some embodiments, the content of soy protein isolate in the improver is 1.6-8.0 g / L based on the total mass of the improved solution, and can also be 1.6 g / L, 2.4 g / L, 3.2 g / L, 3.4 g / L, 4.8 g / L, 5.2 g / L, 6.4 g / L, 7.2 g / L, or 8.0 g / L. Preferably, it is 3.2 g / L to 6.4 g / L.

[0061] In one specific embodiment, the composition is 6 g / L sodium carbonate, 8 g / L sodium citrate, and 3.2 g / L soy protein isolate.

[0062] The modifier and solvent of this invention can be individually packaged and mixed in proportion before use, or they can be pre-prepared into a homogeneous and stable solution for direct use. Both application methods achieve the synergistic water-retention and antioxidant effects of the three components of sodium carbonate, sodium citrate, and soy protein isolate as described above, without affecting their modifying performance due to changes in the mixing sequence. This invention does not impose any particular limitations; in practical applications, the choice can be flexibly made based on production scale, storage conditions, and process duration. Another aspect of this invention protects the use of the modifier or the modified solution described above in improving the quality of frozen chicken feet or in preparing products with improved frozen chicken feet quality.

[0063] The modifier or modified solution of this invention can be used to prepare modified or cooked meat products. Modified meat products refer to non-ready-to-eat chicken feet made primarily from fresh (frozen) livestock and poultry products, which are cooled or frozen and packaged, requiring refrigeration or freezing for storage and transportation. Cooked meat products refer to products processed primarily from fresh (frozen) livestock and poultry products, which are cooled or frozen for transportation purposes. The fresh (frozen) livestock and poultry products are fresh (frozen) chicken feet (a poultry by-product).

[0064] Another aspect of the present invention protects a method for improving the quality of frozen chicken feet, comprising the following steps:

[0065] Chicken feet are mixed with the improver or the improver solution described above and then frozen for preservation.

[0066] In some embodiments, the chicken feet are selected from one or both of raw and cooked chicken feet.

[0067] In some embodiments, the chicken feet are cooked chicken feet.

[0068] In some embodiments, the mass ratio of the chicken feet to the modified solution is 1:(1-6), but it can also be 1:1, 1:2, 1:3, 1:4, 1:5, or 1:6. In one specific embodiment, it is 1:2.5.

[0069] In some embodiments, the mixing temperature is 14-18°C, or it can be 14°C, 15°C, 16°C, 17°C, or 18°C.

[0070] In some implementations, the mixing time is 14-18 hours, or it can be 14 hours, 15 hours, 16 hours, 17 hours, or 18 hours.

[0071] In some embodiments, the freezing temperature is not higher than 15°C, but can also be -15°C, -16°C, -17°C, -18°C, -23°C, or -25°C.

[0072] In some embodiments, the cryopreservation time is not less than 15 days, but can also be 15 days, 18 days, 20 days, 22 days, 24 days, 26 days, 28 days, or 30 days.

[0073] Another aspect of the present invention protects the improved chicken feet obtained by the improved method described above.

[0074] In some embodiments, the thawing loss rate of the improved chicken feet is no higher than 8.5%, and can also be 8.5%, 8.0%, 7.5%, 7%, 6.5%, 6%, 5.5%, 5.0%, 4.5%, or 4.2%. Thawing loss rate refers to the ratio of the mass difference of a frozen product before and after thawing to its mass before thawing. After treatment with the improver or improver solution of this invention, the thawing loss rate of chicken feet is reduced from 13%~18% to less than 8.5%.

[0075] In some embodiments, the weight gain rate of the improved chicken feet after soaking is not less than 25%, and can also be 25%, 26%, 28%, 30%, 32%, 34%, 35%, 36%, 37%, or 38%. The weight gain rate after soaking refers to the ratio of the difference in mass of the chicken feet before and after soaking in the solution described above to the mass of the chicken feet before soaking.

[0076] In some implementations, the elasticity value of the improved chicken feet is not less than 0.9.

[0077] In some implementations, the elasticity value of the improved chicken feet is not less than 0.063 mg / kg.

[0078] The following specific embodiments 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.

[0079] 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. Test methods in the following embodiments that do not specify specific conditions are generally performed under conventional conditions or as recommended by the respective manufacturers.

[0080] When numerical ranges are given in the embodiments, it should be understood that, unless otherwise stated in the present 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 in this invention have the same meaning as commonly understood by one of ordinary skill in the art. In addition to the specific methods, apparatus, and materials used in the embodiments, based on the knowledge of the prior art possessed by one of ordinary skill in the art and the description of this invention, any prior art methods, apparatus, and materials similar to or equivalent to those described, apparatus, and materials in the embodiments of this invention may be used to implement the present invention.

[0081] In the embodiments described below in this application, the fresh boneless chicken feet were supplied by Sunner Group (Jiangxi, China).

[0082] Soy protein isolate was purchased from Zhongchen Biotechnology Co., Ltd. (Henan, China). The molecular weight of the soy protein isolate was 220 kDa. On a dry basis, the protein content of the soy protein isolate was 94.5 g / 100 g, and the moisture content was 7.8 g / 100 g. On a dry basis, the total alkali content of sodium carbonate was 99.4 wt%. The moisture content of sodium citrate was 11 wt%.

[0083] The preparation method of cooked chicken feet in the following embodiment of this application is as follows: after cleaning the boneless chicken feet, boil them in boiling water for 6 minutes, rinse them, and then soak them in water at 4 ℃ for 1 hour to obtain the product.

[0084] Example 1: Screening of water-retaining substances and their concentrations

[0085] In this Example 1, the optimal concentrations of sodium carbonate, sodium citrate, and soy protein isolate were determined using soaking weight gain and thawing loss rates as indicators. These included the following:

[0086] 1.1 Screening of the optimal concentration using single-factor experiments

[0087] 1.1.1 Group Design

[0088] A total of 16 groups were designed, with 3 replicates in each group and 3 chicken feet in each replicate, as detailed in Table 1.

[0089] Sodium carbonate and distilled water were mixed to prepare solutions with final concentrations of 2.0, 4.0, 6.0, 8.0, and 10.0 g / L.

[0090] Sodium citrate and distilled water were mixed to prepare solutions with final concentrations of 2.0, 4.0, 6.0, 8.0, and 10.0 g / L.

[0091] Soy protein isolate was mixed with distilled water to prepare solutions with final concentrations of 1.6, 3.2, 4.8, 6.4, and 8.0 g / L. Details are as follows:

[0092] Table 1

[0093]

[0094] Chicken feet and the aqueous solutions from each group were mixed and soaked at a mass ratio of 1 kg: 2.5 kg at 15℃ for 16 hours. After soaking, on day 0, the surface moisture was wiped off, and the soaked chicken feet were placed in sealed bags and frozen at -15℃ for 30 days.

[0095] The immersion weight gain rate was determined as follows:

[0096] Accurately measure the weight of chicken feet before and after soaking, and calculate the soaking weight gain rate according to the formula:

[0097]

[0098] Where: M1 - mass of the chicken feet sample before soaking, g;

[0099] M2 - Mass of chicken feet sample after soaking, g.

[0100] The thawing loss rate was determined as follows:

[0101] After soaking, remove the chicken feet sample from the freezer and thaw overnight at 4°C. Wipe off surface moisture with filter paper and weigh the sample. Calculate the thawing loss rate using the formula:

[0102]

[0103] Where: L1 - mass of the chicken feet sample before thawing, g;

[0104] L2 - Mass of the chicken feet sample after thawing, in g.

[0105] 1.1.2 Results

[0106] Soaking weight gain reflects the sample's ability to absorb water. A higher weight gain results in fuller, more flavorful chicken feet. Furthermore, increased weight gain improves product yield and economic value. Thawing loss reflects the sample's ability to retain moisture during frozen storage. A low thawing loss reduces juice loss from chicken feet, maintaining a juicy texture. Soaking weight gain and thawing loss are key indicators for evaluating the water retention of meat products during processing; therefore, these two indicators were selected for single-factor screening of water-retaining agents.

[0107] See results Figure 1-3 .

[0108] from Figure 1 It can be seen that the amount of sodium carbonate added has a significant impact on the soaking weight gain and thawing loss rate of chicken feet. Sodium carbonate dissolves in water, and HCO3-2- Ions penetrate deep into muscle and interact with protein side chains, effectively increasing the electrostatic repulsion between muscle proteins, thereby relaxing the peptide chain structure and increasing water storage space. When sodium carbonate concentrations were 4 g / L–10 g / L, there was no significant difference in soaking weight gain (p>0.05), while the highest soaking weight gain (24.09%) was observed at a concentration of 8 g / L. When sodium carbonate concentrations were 2 g / L–6 g / L, the thawing loss rate of chicken feet was lower than other groups, with the lowest thawing loss rate (8.65%) at a concentration of 6 g / L, which was not significantly different from 8 g / L. Considering both soaking weight gain and thawing loss rate, sodium carbonate concentrations of 4 g / L–8 g / L showed the best effect.

[0109] from Figure 2 It can be seen that with the increase of sodium citrate concentration, the soaking weight gain rate shows an upward trend, while the thawing loss rate shows a trend of first decreasing and then increasing. Sodium citrate, after dissolving in water, ionizes to release citrate ions, which have a strong chelating ability and can bind with calcium in meat products. 2+ Mg 2+ This combination prevents these ions from cross-linking with proteins, thereby improving water retention. When the sodium citrate concentration is between 0 g / L and 10 g / L, the weight gain of chicken feet after soaking increases from 7.70% to 27.25%. However, when the concentration exceeds 8 g / L, the weight gain does not change significantly (p>0.05). At sodium citrate concentrations of 4 g / L and 6 g / L, the thawing loss rate of chicken feet is significantly lower than in other groups (p<0.05). Based on the results of both soaking weight gain and thawing loss, sodium citrate concentrations of 4 g / L to 8 g / L show the best effect.

[0110] from Figure 3 It was found that with the increase of soy protein isolate concentration, the soaking weight gain of chicken feet showed a trend of first increasing and then leveling off, while the thawing loss rate showed a trend of first decreasing and then increasing. Soy protein isolate can rely on the hydrophilic groups in its molecular structure to achieve water adsorption and fixation through hydrogen bonding and steric hindrance. The soaking weight gain of chicken feet reached its highest value (12.96%) when the soy protein isolate concentration was 6.4 g / L. With increasing soy protein isolate concentration, the trend of change in soaking weight gain was not significant (p>0.05). Compared with chicken feet soaked in distilled water, the thawing loss rate was significantly reduced when the soy protein isolate concentration was between 1.6 g / L and 6.4 g / L (p<0.05). Combining the results of both soaking weight gain and thawing loss rate, a soy protein isolate concentration of 3.2 g / L to 6.4 g / L showed the best effect.

[0111] 1.2 Orthogonal Experimental Design

[0112] Based on the results of single-factor experiments, sodium carbonate, sodium citrate, and soy protein isolate, three water-retaining substances, were combined and formulated with L9(3) 3 Orthogonal optimization experiments were conducted, with immersion weight gain rate and thawing loss rate as evaluation indicators. See Table 2 for details.

[0113] Table 2

[0114]

[0115] The processing method is the same as step 1.1.

[0116] The soaking weight gain rate and thawing loss rate were tested using the same method as step 1.1.1, and the results are shown in Table 3.

[0117] Table 3

[0118]

[0119] As shown in Table 3, in terms of the effect on the weight gain rate of soaked chicken feet, sodium carbonate > soy protein isolate > sodium citrate. The optimal compound ratio is 8 g / L sodium carbonate, 8 g / L sodium citrate, and 3.2 g / L soy protein isolate.

[0120] As shown in Table 3, in terms of the impact on the thawing loss rate of chicken feet, sodium citrate > soy protein isolate > sodium carbonate, and the optimal compounding ratio is 6 g / L sodium carbonate, 8 g / L sodium citrate, and 3.2 g / L soy protein isolate.

[0121] Considering that freezing has a significant impact on the water retention of chicken feet, the thawing loss rate was chosen as the final evaluation index. The optimal combination was 6 g / L sodium carbonate, 8 g / L sodium citrate, and 3.2 g / L soy protein isolate.

[0122] Since the optimal combination was not included in the orthogonal experiment, a verification experiment was conducted using immersion weight gain rate and thawing loss rate as evaluation indicators. The verification experiment results showed that the optimal combination had an immersion weight gain rate of 37.09% and a thawing loss rate of 4.12%, which was better than the other combinations in the orthogonal experiment.

[0123] Example 2: Validation of the Modifier

[0124] 2.1 Group Design

[0125] Based on the results of the orthogonal experiment, two treatment groups and one control group were set up, as follows:

[0126] SC treatment group: 6 g / L sodium carbonate, 8 g / L sodium citrate.

[0127] SCP treatment kit: 6 g / L sodium carbonate, 8 g / L sodium citrate, 3.2 g / L soy protein isolate.

[0128] Control group: Soaked in distilled water.

[0129] Chicken feet and the aqueous solutions from each group were mixed and soaked at a mass ratio of 1 kg:2.5 kg at 15℃ for 16 hours. After soaking, the surface moisture was wiped off, and the soaked chicken feet were placed in sealed bags and frozen at -15℃ for 30 days. The weight gain after 16 hours of soaking was calculated; the thawing loss rate was calculated after 15 and 30 days of frozen storage. (Same as step 1.1.1).

[0130] 2.2 Effect on the weight gain rate of soaked chicken feet

[0131] See results Figure 4 .

[0132] from Figure 4 It was found that the weight gain rate of chicken feet after water retention treatment (i.e., SC treatment and SCP treatment) was significantly higher than that of the control group (p < 0.05). The weight gain rate of chicken feet in the SC group was 31.27%, significantly higher than that of the control group (11.01%). The weight gain rate of the SCP group was 37.09%, an increase of 18.61% compared with the SC group. This may be because soy protein isolate enters the chicken foot tissue and uses its water-absorbing properties to bring more water into the muscle tissue.

[0133] 2.3 Effect on the thawing loss rate of chicken feet

[0134] See results Figure 5 .

[0135] from Figure 5 It was found that the thawing loss rate of all three groups of samples increased with the extension of frozen storage time. This may be because the free water in the chicken feet continuously transforms into ice crystals during frozen storage. The growth of ice crystals damages the tissue structure, expands the gaps between muscle fibers, and leads to increased water loss after thawing. After 30 days of freezing, the thawing loss rate of chicken feet in the SC group was 10.79%, significantly lower than that in the control group (14.61%), indicating that the water retention treatment in the SC group delayed water loss during frozen storage. This may be because sodium carbonate and sodium citrate can promote the formation of myosin gel, thereby improving the water retention of the meat. The thawing loss rate of the SCP group was 8.45%, significantly lower than the other two groups (p < 0.05). This is because soy protein isolate penetrates into the chicken foot tissue, further hindering the migration of water in the meat, reducing the damage of ice crystals to muscle cells, and thus improving water retention.

[0136] 2.4 Effect on moisture distribution in chicken feet

[0137] The distribution trend and migration rate of moisture in chicken feet samples were determined using low-field nuclear magnetic resonance (NMR). The specific steps are as follows:

[0138] Approximately 9 g of whole chicken feet samples were placed in a sample tube and then subjected to CPMG testing to measure the transverse relaxation time (T2). The Birt inversion algorithm was then used to perform multi-exponential fitting on the decay curve to obtain relaxation information for moisture at different states. The test parameters were: SF=12, SW=200, TW=4000, NS=8, RFD=0.02, RG1=20, DRG1=3.

[0139] Based on the different relaxation times, water can be divided into three phases: T 2b (0.1–10 ms, binding to macromolecules) represents the relaxation time of bound water; T 21 (10-100 ms, located within the myofibril network) represents the water-fixed relaxation time; T 22 (More than 100 ms, located outside the myofibril network) represents the relaxation time of free water. Within each relaxation time, the shorter the time, the lower the degree of freedom and the higher the water retention.

[0140] With relaxation time T 2b T 21 T 22 The x-axis represents relaxation time distribution of the chicken feet samples, and the y-axis represents signal amplitude. Origin 2022 was used to plot these distributions. Results are shown below. Figure 6 Based on the relaxation time range and signal amplitude peak area of ​​water in different phases, the results are shown in [Figure number missing]. Figure 7 The test was conducted by a third-party company, the Scientific Compass Testing Platform.

[0141] Figure 6 This represents the water state and degrees of freedom for the sample at different transverse relaxation times in three phase states. From T... 2b The relaxation time of each group during frozen storage showed a trend of first decreasing and then increasing. The T0 of the control group was... 2b Consistently higher than the SCP group. Combined with the water relaxation time T... 2b The shorter the length, the lower the degree of freedom, indicating better water retention. Therefore, the SCP treatment team was able to reduce the degree of freedom of bound water and improve the water retention of the chicken feet. From day 0 to day 30 of frozen storage, the SCP treatment team T... 21 The peak of the wave segment shifted significantly to the left compared to the control group, indicating a shift towards shorter relaxation times. This demonstrates that SCP treatment can significantly reduce the relaxation time T of the fixed water. 21 This reduces the degree of freedom of water molecules in chicken feet, thereby retaining moisture. No T was detected in the control group on days 0 and 30 of frozen storage. 22 On day 15, the T value of the control group was... 22 The results were significantly higher than those of the SCP treatment group, indicating that the SCP treatment can reduce the degree of freedom of free water in chicken feet.

[0142] Figure 7 The relaxation peak ratios P2b, P21, and P22 represent the percentages of bound water, fixed water, and free water in the total moisture content of meat products, respectively.

[0143] From the perspective of the proportion of bound water (P21), the proportion of fixed water (P21) in each group of chicken feet samples showed a decreasing trend with the extension of frozen storage time, while the proportion of fixed water (P21) showed an increasing trend. This may be because some of the bound water in the chicken feet was converted into fixed water during frozen storage. It is noteworthy that the order of the proportion of fixed water (P21) in chicken feet during frozen storage was SCP group > SC group > control group, indicating that the SCP group consistently had the highest content of fixed water. This may be due to the formation of hydrogen bonds, van der Waals forces, and other non-covalent interactions between water molecules in the chicken feet samples and water-retaining components such as sodium carbonate and soy protein isolate, enhancing the water molecule retention capacity. On day 0, the proportion of free water (P22) in the SCP group chicken feet was the highest, reaching 2.62%. This may be due to the increased electrostatic repulsion caused by water-retaining components, leading to the dissociation of protein structures in the chicken feet, providing space and more binding sites for external free water. The increase in the proportion of free water (P22) in chicken feet may be an important reason for the increased weight gain rate of chicken feet after soaking. During frozen storage, the proportion of free water, P22, decreased with the extension of freezing time. After 30 days of storage, the proportion of free water, P22, in the three groups of samples approached 0%, which may be because free water is more likely to reach the muscle surface and be excreted from the muscle.

[0144] 2.5 Effect on the elasticity of chicken feet

[0145] The elasticity test was conducted as follows: Chicken foot samples were cut into approximately 2 cm × 2 cm pieces and placed in the center of a tray. The test mode was TPA deformation, the test speed was 2 mm / s, and the test time was 5 s. The sample was compressed to 50% using a cylindrical probe (P / 36R) of a texture analyzer. Measurement parameter: elasticity. Elasticity reflects the texture and integrity of the internal network structure of the chicken foot. Results are shown below. Figure 8 .

[0146] from Figure 8 It can be seen that the elasticity of each sample decreased with the extension of storage time. This may be due to the moisture loss and changes in muscle tissue structure during freezing, which affected the texture properties of the samples. On day 0, the chicken feet in the SCP group had the highest elasticity (0.98), and it remained at a high level (0.92) after 30 days of freezing, higher than the control group (0.84) and the SC group (0.89). This indicates that the water retention treatment in the SCP group was more effective than that in the SC group in delaying the decrease in chicken feet elasticity, thus reducing the quality damage caused by freezing.

[0147] 2.6 Effect on TBARS content in chicken feet

[0148] The TBARS value reflects the degree of lipid oxidation. Lipid oxidation further induces protein oxidation, especially structural proteins such as myofibrillar proteins, affecting muscle water retention and functional properties. Therefore, studying the effect of lipid oxidation on water retention in chicken feet is crucial.

[0149] Determination of Thiobarbituric Acid Reactive Substances (TBARS): 5.00 g of the minced chicken feet sample was placed in a centrifuge tube, along with 10 mL of distilled water and 12.5 mL of 20% TCA solution. The mixture was homogenized at high speed and centrifuged (6000 r / min, 15 min, 4°C). 2.00 mL of the supernatant was collected in a colorimetric tube, and 2 mL of 0.02 mol / L TBA solution was added. The tube was incubated in boiling water for 20 min, cooled to room temperature, and the absorbance was measured at 532 nm and 600 nm using a spectrophotometer. A blank was prepared using 2 mL of TCA / H₂O (1:1, v / v) + 2 mL of TBA solution. Results are shown below. Figure 9 .

[0150] from Figure 9 The results showed that the TBARS value increased with prolonged freezing time, possibly due to lipid release caused by freezing damage and juice loss, which increased the contact area between fat and air, thus accelerating fat oxidation. The TBARS values ​​of the control group were significantly higher than those of the SCP and SC treatment groups at 15 and 30 days of freezing (p < 0.05). The TBARS levels of the SCP group at 15 and 30 days of freezing were 0.035 and 0.063 mg / kg, respectively, which were 57.32% and 42.73% lower than those of the SC group. This indicates that the combined water retention treatment of the SCP group can more effectively retain the moisture in chicken feet during freezing, thereby slowing down fat oxidation.

[0151] 2.7 Effect on the solubility of myofibrillar protein in chicken feet

[0152] The solubility of myofibrillar proteins reflects the degree of protein denaturation; the lower the solubility, the more severe the protein denaturation and the worse the stability of the protein structure. Freezing and storage disrupts protein structure, promoting the formation of disulfide bonds, hydrogen bonds, and hydrophobic bonds, enhancing protein-protein interactions and leading to aggregation, thus reducing protein solubility.

[0153] Myofibrillar protein assay: 2 g of minced chicken feet sample was homogenized in 20 mL of pre-cooled buffer (containing 0.1 mol / L NaCl and 20 mmol / L Tris-HCl (pH 7.5)) at 500 r / min for 2 min. The homogenate was then centrifuged at 10,000×g for 10 min, and the precipitate was washed twice with the same buffer under the same centrifugation conditions. Next, 20 mL of buffer (0.6 mol / L NaCl and 20 mmol / L Tris-HCl, pH 7.5) was added to the precipitate and mixed thoroughly. After standing in a refrigerator for 1 h, the mixture was embedded at 10,000×g for 10 min, and the resulting supernatant was the myofibrillar protein. Protein concentration was determined by the biuret method. Results are shown below. Figure 10 .

[0154] from Figure 10 It was found that the solubility of myofibrillar protein decreased with storage time, indicating that the chicken feet samples underwent varying degrees of protein denaturation during frozen storage. After 30 days of freezing, the protein solubility of chicken feet in the SC group was 2.20 mg / mL, higher than that of the control group (2.05 mg / mL). The solubility of myofibrillar protein is affected by salt ion concentration; the Na+ in the SC fraction... + Increasing the ion concentration of the solution promotes protein solubility. The SCP group showed the best effect in inhibiting the freeze-denaturation of chicken feet during frozen storage, with the highest protein solubility of 2.68 mg / mL. This is likely due to the interaction between soy protein isolate and myofibrillar protein, which enhances the solubility of myofibrillar protein.

[0155] 2.8 Effect on the sulfhydryl content of myofibrillar proteins in chicken feet

[0156] The thiol groups of myofibrillar proteins are easily affected by reactive oxygen species, transforming into products such as disulfide bonds, sulfonic acids, and sulfinic acids. The content of thiol groups can reflect the level of protein oxidation.

[0157] The determination of thiol groups was performed as follows: 0.5 mL of the myofibrillar protein obtained in step 2.7 was mixed with 4.5 mL of 0.2 mol / L Tris-HCl (pH=6.8, containing 2% SDS and 10 mmol / L EDTA) and 0.5 mL of 0.2 mol / L Tris-HCl (pH=8.0, containing 0.1% DTNB). The mixture was incubated at 40 ℃ for 25 min, and the absorbance at 412 nm was measured (with a 0.6 mol / L KCl buffer solution as a blank). The absorbance was calculated using the following formula. The results are shown below. Figure 11 .

[0158]

[0159] Where A is the measured absorbance, B is the protein concentration (2 mg / mL), C is the molar extinction coefficient at 13600 M, and D is the dilution volume.

[0160] from Figure 11 It was observed that the thiol content decreased during frozen storage. This is because the formation of ice crystals in the chicken feet leads to changes in protein structure, resulting in the aggregation of thiol groups and strong protein molecules, thus reducing the thiol content. Compared to day 0, the thiol content in the control group decreased by 62.82% on day 30, while the SC and SCP groups decreased by 36.03% and 34.62%, respectively. This demonstrates that SC and SCP treatments can effectively delay the decrease in thiol content in chicken feet, inhibit changes in protein conformation, and maintain the stability of myofibril proteins.

[0161] 2.9 Effects on the structure of myofibril proteins in chicken feet

[0162] Fourier transform infrared spectroscopy is an absorption spectrum of molecular vibrations that reflects conformational changes in protein molecules.

[0163] Fourier transform infrared spectroscopy determination: After freeze-drying the myofibrillar protein obtained in step 2.7 for 24 h, take 1-2 mg of powder and 200 mg of KBr, grind them evenly, place them in a mold, press them into transparent thin sheets on a hydraulic press, and then place them in an infrared spectrometer for testing in the wavelength range of 4000-400 cm⁻¹. -1 32 scans, 4 cm resolution -1 Peakfit software was used for baseline correction, deconvolution, and calculation of protein secondary structure content. Results are shown below. Figure 12 , Figure 13 .

[0164] from Figure 12 It can be seen that the spectra of the three groups of samples show similar patterns. The samples at 3432 cm⁻¹... -1 3200 cm -1 Two main peaks are visible at this location, 3000-3500 cm. -1 The region between these bands is called the "water region," containing information about the amide A band, amide B band, and the stretching vibrations of the water molecule's OH group, which can be used to assess the protein's hydration properties. 1630 cm⁻¹ -1 The peak at 1550 cm⁻¹ is attributed to the characteristic peaks of the C=O and CN stretching vibrations of amide I, and is closely related to hydrogen bonding forces. -1 This is mainly related to the NH bending vibration and OH stretching vibration of the amide II band. 1038 cm⁻¹ -1 It mainly contains information on the stretching vibrations of CO and CNC bonds. Amide I band (1600-1700 cm⁻¹) -1Hydrogen bonds are widely used for protein secondary structure analysis. The secondary structure of myofibrillar proteins is mainly maintained by hydrogen bonds between amino acids and is related to emulsifying properties, gel-forming ability, and water-holding capacity. α-helices and β-sheets are generally considered important structures for maintaining the stability of protein secondary structure, while random coils and β-turns represent the looseness of the secondary structure.

[0165] like Figure 13 As shown, the α-helix structure of each group of samples did not change significantly during frozen storage. The β-sheet ratio of the SCP group on day 0 of frozen storage was 56.61%, lower than that of the control group (63.67%) and the SC group (67.42%), indicating that the SCP treatment promoted protein unfolding. This can increase the number of binding sites for the interaction between myofibrillar proteins and water-retaining molecules, further enhancing the chelating effect of water-retaining components on metal ions such as calcium ions within the protein, thereby enhancing the water-retaining capacity of the chicken feet. After 30 days of frozen storage, the β-sheet content of the control group and the SC group decreased to 57.45% and 63.98%, respectively, while that of the SCP group increased to 70.51%. This may be because the addition of soy protein isolate enhanced the interaction between protein molecules, forming a more stable protein structure. Generally, an increase in the β-sheet structure of myofibrillar proteins indicates that internal residues are exposed on the surface, thereby promoting more orderly cross-linking of the protein and improving water-retaining capacity. The proportion of random coils in myofibrillar proteins increased from 12.56% and 11.93% in the control and SC groups on day 0 to 19.60% and 14.91% on day 30, respectively, while it decreased from 21.99% to 14.32% in the SCP group. This indicates that the SCP treatment effectively reduced the content of random coils in myofibrillar proteins. Furthermore, during cryopreservation, the proportion of β-turn structures in the SCP group decreased from 11.03% to 7.28%.

[0166] The increased proportion of β-sheets and the decreased proportion of β-turns and random coils in myofibrillar proteins indicate that the SCP group composite water-retention treatment can more effectively maintain the stability of chicken foot protein structure, thereby improving water retention capacity.

[0167] 2.10 Effects on the tissue structure of chicken feet

[0168] The composition and morphology of muscle tissue significantly affect the quality of meat products, especially texture and water-holding capacity.

[0169] Tissue sections: The tissue structure of meat samples was observed using HE (hematoxylin-eosin) staining. Chicken foot tissue of 1 cm × 1 cm size was soaked in 4% paraformaldehyde for 6-8 h, dehydrated, embedded in paraffin, dewaxed again to water, stained with hematoxylin and eosin in sequence, dehydrated and mounted, examined under a microscope, and images were acquired and analyzed.

[0170] Figure 14 , Figure 15 The stained area represents connective tissue within the muscle structure, which is a supporting matrix composed of various fibrous proteins (mainly myofibrils).

[0171] like Figure 14 As shown, the connective tissue structure of fresh chicken feet is intact and arranged very tightly.

[0172] like Figure 15 As shown, after 30 days of frozen storage, the connective tissue of chicken feet samples in each group underwent varying degrees of damage. In the control group, the connective tissue connections were severely disordered, the muscle surface was blurred and chaotic, and obvious cavities appeared. This may be due to the formation of ice crystals during frozen storage, which damaged the cell structure. The ice crystals, during their growth, compressed the muscle fibers, resulting in larger pores. The SC group showed partial cavities in its connective tissue, with less structural damage. This may be because the water-retaining components in the SC group increased the content of soluble proteins, inhibiting the degree of protein denaturation during freezing. The SCP group showed the least degree of connective tissue damage, with relatively tight adhesion between myofibrils. SCP treatment effectively maintained the integrity of the connective tissue. This may be because soy protein isolate can inhibit the growth of ice crystals during frozen storage. Furthermore, protein solubility results showed that the SCP group significantly enhanced the stability of myofibril proteins and delayed protein denaturation.

[0173] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A quality improver for frozen chicken feet, characterized in that, It contains the following components in parts by weight: Sodium carbonate 20-100 parts Sodium citrate 20-100 parts 16-80 servings of soy protein isolate.

2. The modifier as described in claim 1, characterized in that, The molecular weight of the soy protein isolate is 10-320 kDa; And / or, on a dry basis, the protein content in the soy protein isolate is ≥90g / 100g; And / or, the moisture content in the soy protein isolate is ≤10g / 100g; And / or, on a dry basis, the total alkali content of the sodium carbonate is ≥99.2 wt%; And / or, the water content in the sodium citrate is 10-13 wt%.

3. A quality improvement solution for frozen chicken feet, characterized in that, It contains the modifier and solvent as described in claim 1 or 2.

4. The improved solution as described in claim 3, characterized in that, The solvent is selected from water; And / or, based on the total mass of the modified solution, the sodium carbonate content in the modifier is 2.0-10.0 g / L; And / or, based on the total mass of the modified solution, the content of sodium citrate in the modifier is 2.0-10.0 g / L; And / or, based on the total mass of the modified solution, the content of soy protein isolate in the improver is 1.6-8.0 g / L.

5. The use of the improver as described in claim 1 or 2 or the improver solution as described in claim 3 or 4 in improving the quality of frozen chicken feet or in preparing products with improved quality of frozen chicken feet.

6. A method for improving the quality of frozen chicken feet, characterized in that, Includes the following steps: Chicken feet are mixed with the improver as described in claim 1 or 2 or the improver solution as described in claim 3 or 4, and then frozen for preservation.

7. The improved method as described in claim 6, characterized in that, The chicken feet are selected from one or both of raw and cooked chicken feet; And / or, the mass ratio of the chicken feet to the modified solution is 1:(1-6).

8. The improved method as described in claim 6, characterized in that, The mixing temperature is 14-18℃; And / or, the mixing time is 14-18 hours; And / or, the temperature for freezing and preservation is not higher than -15°C; And / or, the freezing and preservation time is not less than 15 days.

9. The improved chicken feet obtained by the improved method according to any one of claims 6-8.

10. The improved chicken feet as described in claim 9, characterized in that, The thawing loss rate of the improved chicken feet is no higher than 8.5%, and / or the soaking weight gain rate of the improved chicken feet is no less than 25%.

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