Method for improving the special fishy smell of frozen duck meat

Abstract

This invention discloses a method for improving the distinctive fishy odor of frozen duck meat, belonging to the field of food processing technology. The method involves dissolving NY50C protease in water to form an enzyme treatment solution, uniformly injecting it into the duck meat, allowing it to stand at 4°C for 12-24 hours, and then freezing it. This method effectively reduces the content of typical fishy odor substances such as 1-octen-3-ol, 1-octen-3-one, and octanoic acid produced during the freezing process of duck meat without damaging the integrity of the myofibrillar protein gel network. It also shows a good inhibitory effect on rancid substances such as (E,E)-2,4-decadienal, and moderately retains oily aroma substances such as heptanal and octanal, thereby significantly optimizing the flavor profile of frozen duck meat. Furthermore, it improves the textural properties of frozen duck meat, maintaining suitable elasticity and chewiness, and preserving good color stability.

Description

Technical Field

[0001] This invention relates to a method for improving the distinctive fishy smell of frozen duck meat, belonging to the field of food processing technology. Background Technology

[0002] Frozen duck meat, due to its long storage period, convenient transportation, and ease of consumption, is widely used in ready-to-cook meals, catering processing, and home consumption, and is currently one of the important products in the poultry processing industry. However, frozen duck meat is prone to developing a distinctive fishy odor during freezing, thawing, and subsequent processing, which seriously affects product flavor, eating experience, and market acceptance, becoming a key technological bottleneck restricting the high-quality development of the frozen duck meat industry.

[0003] The inherent characteristics of frozen duck meat make its gamey odor persistent and difficult to remove. On one hand, duck meat has a high subcutaneous fat content, and a large proportion of this fat is unsaturated fatty acids. While freezing at 18°C ​​can slow down the rate of fat oxidation, unsaturated fatty acids will continue to oxidize during long-term freezing and repeated freeze-thaw cycles, producing aldehydes and alcohols such as hexanal, nonanal, and 1-octen-3-ol, resulting in a pungent rancid smell. Furthermore, ice crystals formed during freezing damage the muscle fiber structure of duck meat, leading to coarsening, decreased density, and poor water retention. After thawing, a large amount of juice is lost, and the odorous substances carried within diffuse and remain in the intermuscular spaces, making them difficult to remove with simple treatment. In addition, freezing causes hemoglobin and myoglobin in the duck blood to coagulate and bind tightly to the muscle tissue, making them difficult to extract using conventional soaking methods. Simultaneously, the endogenous reservoirs of odor, such as the preen gland, lymphatic tissue, and hair follicles in the duck tail, are even more difficult to completely remove after freezing, continuously releasing odorous substances and further exacerbating the problem. Studies have shown that duck meat frozen for 7 days and then reheated has a significantly stronger odor than fresh duck meat, and the more freeze-thaw cycles, the stronger the odor.

[0004] The distinctive fishy smell of frozen duck meat is primarily caused by 13 characteristic substances, with aldehydes (nonanal, octanal, heptanal, octanoic acid, etc.) being the core source. These substances are fat oxidation products, characterized by strong irritation and a low odor threshold, requiring only μg / kg levels to be perceived by the human body. These odor-causing substances are characterized by both volatility and fat solubility. Low-molecular-weight aldehydes are easily volatile, while high-molecular-weight aldehydes and alcohols are easily soluble in duck fat. During freezing, the fat solidifies, "locking" these odor-causing substances in, releasing them in large quantities only during heating. Furthermore, these substances have extremely low odor thresholds, and the synergistic effect of multiple substances further intensifies the odor. Moreover, fat oxidation and protein degradation continue during freezing, leading to the continuous generation of odor-causing substances that are difficult to remove completely in a single treatment. In addition, some odor-causing substances (such as nitrogen-containing heterocyclic compounds) form stable bonds with proteins and amino acids in duck meat, which are difficult to dissociate using conventional methods, further increasing the difficulty of removing the odor.

[0005] In existing technologies, methods for removing the gamey smell from frozen duck meat mainly fall into the following categories: (1) Physical masking method: For example, Chinese patent CN103393061B discloses a process for removing the fishy smell from duck meat seasoning. It uses cooking wine, edible organic acids (acetic acid, citric acid), ginger, onion, Sichuan pepper and other raw materials as masking agents, and masks or dissolves the fishy smell substances through soaking treatment. Although this method can reduce the fishy smell to a certain extent, it is essentially a "masking" method of removing the fishy smell. It fails to fundamentally degrade or transform the fishy smell substances. Moreover, the fishy smell substances will continue to be generated and accumulated during the frozen storage of the treated duck meat, and the fishy smell removal effect is difficult to last.

[0006] (2) Traditional enzymatic hydrolysis method: For example, Chinese patent CN111493288A discloses a processing method for removing the fishy smell of salted duck, which uses papain and fat flavor enzymes for enzymatic hydrolysis before braising. However, this technology has obvious limitations: First, it is aimed at the pre-braising process of salted duck and is not suitable for maintaining the quality of frozen duck meat during long-term storage; Second, fat flavor enzymes mainly focus on catalyzing the formation of aroma substances from fats, and lack the ability to specifically degrade or transform the characteristic fishy smell substances (such as 1-octen-3-ol, 1-octen-3-one, octanoic acid, etc.) produced by lipid oxidation during frozen storage; Third, papain has strong activity and violent enzymatic hydrolysis, which can easily lead to excessive hydrolysis of myofibril protein, causing meat rot and gel network collapse, which can exacerbate juice loss and flavor deterioration during frozen storage.

[0007] (3) Other protease treatments: Existing technologies also disclose technical solutions for treating meat with kiwi protease, trypsin, etc. to improve tenderness or remove fishy smell. However, these technologies generally have problems such as difficulty in accurately controlling the degree of enzymatic hydrolysis, excessive damage to the protein network structure, and limited functionality. They often only produce effects on a single dimension of tenderness or flavor, and it is difficult to optimize the flavor profile while taking into account the stability of texture and color retention, resulting in an incomplete improvement in product quality.

[0008] Therefore, developing a method that can efficiently and thoroughly remove the fishy smell from frozen duck meat while preserving its texture, flavor, and nutrients, and is suitable for industrial production, has become a pressing technical problem in this field. Summary of the Invention

[0009] To address the shortcomings of existing technologies, the present invention aims to provide a method for improving the distinctive fishy odor of frozen duck meat. This method involves treating duck meat with NY50C protease. Without disrupting the integrity of the myofibrillar protein gel network, it effectively reduces the content of typical fishy odor substances such as 1-octen-3-ol, 1-octen-3-one, and octanoic acid produced during the freezing process. Simultaneously, it exhibits a good inhibitory effect on rancid substances such as (E,E)-2,4-decadienal, and moderately retains oily aroma substances such as heptanal and octanal, thereby significantly optimizing the flavor profile of frozen duck meat. Furthermore, the treatment of this invention also improves the textural properties of frozen duck meat, maintaining suitable elasticity and chewiness, and preserving good color stability.

[0010] To achieve the above objectives, the following technical solution is provided: This invention provides a method for improving the distinctive fishy smell of frozen duck meat, the method comprising the following: Dissolve NY50C protease in water to form an enzyme treatment solution, inject it evenly into the duck meat, let it stand at 4℃ for 12-24 hours, and then freeze it for preservation.

[0011] In one embodiment, the enzyme treatment solution also contains salt, with the amount of salt added being 0.8% to 1.2% based on the weight of the duck meat.

[0012] In one embodiment, the amount of NY50C protease used is 0.005% to 0.02% based on the weight of duck meat; more preferably, it is 0.01% to 0.10%.

[0013] In one embodiment, the NY50C protease is derived from Bacillus and has an enzyme activity of 50,000~100,000 U / g.

[0014] In one embodiment, the amount of enzyme treatment solution injected is 10% to 20% of the weight of the duck meat.

[0015] In one embodiment, the duck meat is turned over every 4 to 6 hours during the resting period.

[0016] In one embodiment, the cryopreservation temperature is -18 to -40°C.

[0017] In one embodiment, the special odor substance includes trans-2-octenal, (E,E)-2,4-decadienal, 1-octen-3-one, 1-octen-3-ol, and octanoic acid.

[0018] In one embodiment, the enzyme treatment solution further includes L-arginine, and the amount of L-arginine added is 0.4% to 0.8% based on the weight of duck meat.

[0019] In one embodiment, the mass ratio of L-arginine to NY50C protease in the enzyme treatment solution is 30:1 to 160:1; preferably 60:1.

[0020] The present invention also provides a method for improving the quality of frozen duck meat, the method comprising the following: Dissolve NY50C protease, L-arginine, and salt in water to form an enzyme treatment solution, inject it evenly into the duck meat, let it stand at 4°C for 12-24 hours, and then freeze it for preservation.

[0021] The present invention also provides the application of the above-described method in processed duck meat products.

[0022] Beneficial effects: Compared with the prior art, the present invention has the following advantages: (1) This invention is the first to apply NY50C protease to the special odor treatment of frozen duck meat; compared with the papain, fat flavor enzyme, kiwi protease or trypsin commonly used in the prior art, NY50C protease has a more significant degradation effect on the characteristic odor substances of frozen duck meat (1-octen-3-ol, 1-octen-3-one, octanoic acid, etc.), and is less likely to cause excessive protein hydrolysis and meat rot. (2) Based on the single enzyme treatment, the present invention combines L-arginine with NY50C protease in a specific ratio (preferably 60:1), which produces a significant synergistic effect: the inhibitory effect on typical fishy substances (1-octen-3-one, 1-octen-3-ol, octanoic acid) and rancid substances ((E,E)-2,4-decadienal, trans-2-octenal) is the most prominent, among which the octanoic acid content is reduced to 0.16 μg / kg; at the same time, the regulation of oil aroma substances is more balanced, which avoids the accumulation of off-odors caused by excessive oxidation and retains a moderate oil aroma. (3) In addition, the treatment of the present invention also significantly improves the quality of frozen duck meat, such as significantly reducing the loss of frozen duck meat during cooking and thawing, and significantly improving the textural properties of frozen duck meat. Detailed Implementation

[0023] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. The specific embodiments described below further illustrate the present invention.

[0024] The source of raw materials involved in this invention: NY50C protease, derived from Bacillus, has an enzyme activity of 50,000~100,000 U / g and was purchased from Amano Enzyme Products Co., Ltd., Japan. L-arginine, salt, etc., are all food-grade reagents.

[0025] The testing method involved in this invention: 1. Characteristic flavor compounds (GC-MS) The content of characteristic flavor compounds was analyzed using headspace solid-phase microextraction-gas chromatography-mass spectrometry.

[0026] 2. Texture and Shear Force Texture properties were determined using the TA-XT plus physical property tester. 3. pH value and color Measurements were taken using a precision pH meter and colorimeter. 4. Fatty acid oxidation (TBARS) TBARS values ​​were determined using the thiobarbituric acid method and expressed as mg MDA / kg. 5. Weight gain during pickling, thawing loss, and cooking loss After injection, the surface moisture of the duck breast meat is dried, weighed, and recorded as M1 (g). After 24 hours of static curing, it is taken out, the surface residual curing liquid is wiped dry again, and it is weighed and recorded as M2 (g). The formula for the curing weight gain rate is shown in 4-1: , .

[0027] (1) After the duck breast meat was left to marinate, the surface moisture was wiped dry and the weight was recorded as M3 (g). The duck breast meat was then frozen at -20℃. After one month, the sample was removed and thawed at 4℃ for 24 hours. After complete thawing, the surface exudate was wiped off, and the weight was recorded as M4 (g). Subsequently, a portion of the sample (M5, g) was weighed, placed in a retort bag, sealed, and heated in a 95℃ constant temperature water bath for 15 minutes. After heat treatment, the sample was allowed to cool to room temperature, the surface moisture was wiped dry, and the final weight was recorded as M6 (g). Thawing loss and cooking loss were calculated using the following formula: (2) (3) Example 1 A method for improving the distinctive gamey odor of frozen duck meat includes the following: (1) Add 0.01% NY50C protease (based on duck meat weight) and 1.00% salt (based on duck meat weight) to deionized water, stir thoroughly to dissolve, and prepare an enzyme treatment solution; (2) Select duck breast meat, thaw it naturally at 4℃ for 24 hours, soak it for 2 hours to remove blood, take it out and use filter paper to dry the surface moisture, and carefully remove the surface fascia, connective tissue and visible fat. (3) The enzyme treatment solution from step (1) was uniformly injected into the duck breast meat using a syringe. The injection rate was 20% (w / w) of the duck meat weight. The injected sample was placed in a 4°C environment for 24 h of static marinating. During this period, the sample was turned over once every 6 h to ensure uniform marinating. (4) After the marinating is completed, the duck breast is stored in a sealed bag and frozen at -20℃ for 30 days. After that, it is taken out and thawed at 4℃ for 24 hours. Various indicators are measured.

[0028] Example 2 The only difference from Example 1 is that the amount of NY50C protease added in step (1) is adjusted to 0.10%, while other parameters and conditions are the same as in Example 1.

[0029] Example 3 The only difference from Example 1 is that the amount of NY50C protease added in step (1) is adjusted to 0.02%, while other parameters and conditions are the same as in Example 1.

[0030] Example 4 A method for improving the distinctive gamey odor of frozen duck meat includes the following: (1) Add 0.02% NY50C protease (based on duck meat weight), 0.60% L-arginine (based on duck meat weight) and 1.00% salt (based on duck meat weight) to deionized water, stir thoroughly to dissolve, and prepare an enzyme treatment solution; (2) Select duck breast meat, thaw it naturally at 4℃ for 24 hours, soak it for 2 hours to remove blood, take it out and use filter paper to dry the surface moisture, and carefully remove the surface fascia, connective tissue and visible fat. (3) The enzyme treatment solution from step (1) was uniformly injected into the duck breast meat using a syringe. The injection rate was 20% (w / w) of the duck meat weight. The injected sample was placed in a 4°C environment for 24 h of static marinating. During this period, the sample was turned over once every 6 h to ensure uniform marinating. (4) After the marinating is completed, the duck breast is stored in a sealed bag and frozen at -20℃ for 30 days. After that, it is taken out and thawed at 4℃ for 24 hours. Various indicators are measured.

[0031] Comparative Example 1 The only difference from Example 1 is that only 1.00% saline is used to form the injection solution; all other parameters and conditions are the same as in Example 1.

[0032] Comparative Example 2 The only difference from Example 1 is that the injection solution is made with 0.60% L-arginine and 1.00% saline and does not contain NY50C protease. All other parameters and conditions are the same as in Example 1.

[0033] Comparative Example 3 The only difference from Example 1 is that 0.20% ascorbic acid oxidase and 1.00% saline are used to form the injection solution, while all other parameters and conditions are the same as in Example 1.

[0034] Comparative Example 4 The only difference from Example 1 is that 0.10% kiwifruit protease and 1.00% saline are used to form the injection solution, while all other parameters and conditions are the same as in Example 1.

[0035] Comparative Example 5 The only difference from Example 1 is that 0.10% sodium carbonate and 1.00% salt are used to form the injection solution, while all other parameters and conditions are the same as in Example 1.

[0036] Comparative Example 6 The only difference from Example 1 is that 0.40% L-lysine and 1.00% saline are used to form the injection solution, while all other parameters and conditions are the same as in Example 1.

[0037] Results Analysis 1. Determination of characteristic flavor compounds The characteristic flavor compounds of each group of frozen duck meat were analyzed by GC-MS, and the results are shown in Table 1. Table 1. Content of characteristic flavor compounds in frozen duck meat from different treatment groups (μg / kg)

[0038] Note: The rate of change refers to the rate of change of flavor compounds in Example 4 compared to Comparative Example 1; different letters in the same column indicate significant differences. p <0.05).

[0039] The results in the table show that treatment with NY50C protease alone (Example 1) significantly reduced the content of typical odorous substances in frozen duck meat: 1-octen-3-one decreased by 31.00%, 1-octen-3-ol decreased by 45.98%, and octanoic acid decreased by 57.29% (compared to Comparative Example 1), with significantly better results than the blank group. The synergistic treatment group (Example 4) showed a more prominent inhibitory effect on negative flavor substances: 1-octen-3-one decreased by 84.85%, 1-octen-3-ol decreased by 71.82%, and octanoic acid decreased by 96.71%, the lowest among all treatment groups; it also had a significant inhibitory effect on rancid substances such as (E, E)-2,4-decadienal and trans-2-octenal.

[0040] Regarding the aroma compounds in the oils, the synergistic treatment group showed the most balanced regulation of heptaldehyde, octanaldehyde, decanaldehyde, and 2,3-octanedione, which not only avoided the accumulation of off-odors caused by excessive oxidation but also preserved a moderate oil aroma, resulting in the best flavor profile.

[0041] 2. Texture properties Using TA The textural properties were determined using the XT plus physical property tester, and the results are shown in Table 2. Table 2. Texture and shear force of frozen duck meat in different treatment groups

[0042] Note: Different letters in the same column indicate significant differences. p <0.05).

[0043] The results in the table show that the co-treatment group (Example 4) had a hardness of 2279.76 g, which was 31.61% lower than the blank group, and an elasticity of 0.68, which was 11.48% higher than the blank group, effectively improving the hardening of meat caused by freezing. Compared with the single NY50C protease group (Example 1) (hardness 1864.06 g, elasticity 0.56), the co-treatment group had higher hardness and better elasticity, proving that L-arginine effectively alleviated the excessive hydrolysis of protease, maintained the integrity of the protein network structure, and achieved the texture improvement effect of "tender but not mushy".

[0044] It is worth noting that although the kiwi protease group of the prior art (Comparative Example 4) has a lower hardness, its elasticity is significantly reduced (0.51) and its cohesion is also significantly reduced, indicating that its protein network has been excessively hydrolyzed and destroyed, resulting in the flesh tending to rot. Compared with the NY50C protease treatment group (elasticity 0.56) and the synergistic group (elasticity 0.68) of the present invention, its texture balance is significantly worse.

[0045] 3. pH value and color Table 3. pH and color parameters of frozen duck meat in different treatment groups

[0046] Note: Different letters in the same column indicate significant differences. p <0.05).

[0047] The results in the table show that the pH of the synergistic treatment group (Example 4) was 6.39, which was 12.11% higher than that of the blank group, effectively deviating from the isoelectric point of myofibrillar protein, which is beneficial to improving water retention; the L value was 40.52, indicating that the muscle structure was dense and the water was firmly bound; the a value was 10.08, which was higher than that of the blank group (Comparative Example 1), indicating that the reduced state of myoglobin was protected; the b* value was 8.85, which was at a low level, indicating that the degree of lipid oxidation was mild.

[0048] 4. Determination of lipid oxidation performance (TBARS) Table 4. TBARS values ​​of frozen duck meat in different treatment groups

[0049] Note: Different letters in the same column indicate significant differences. p <0.05).

[0050] The results in the table show that the synergistic treatment group (Example 4) is significantly better than the blank group (Comparative Example 1), indicating that the composition of the present invention has significant antioxidant activity. Although the TBARS value of the prior art kiwifruit protease group (Comparative Example 1) is lower than that of the blank group (Comparative Example 1), it is significantly higher than that of the synergistic treatment group (Example 4), and its antioxidant effect is significantly worse than that of the present invention.

[0051] 5. Weight gain during pickling, loss during cooking and thawing Table 5. Weight gain and cooking loss of frozen duck meat in different treatment groups after curing

[0052] Note: Different letters in the same column indicate significant differences. p <0.05).

[0053] Based on the weight gain during curing and cooking loss of frozen duck meat in different treatment groups, the thawing loss of frozen duck meat in different treatment groups was measured as follows: Table 6. Thawing losses of frozen duck meat in different treatment groups

[0054] Note: Different letters in the same column indicate significant differences. p <0.05).

[0055] As can be seen from Tables 5 and 6: The cooking loss of the NY50C protease-treated group (Example 1) (31.52%) was significantly lower than that of the blank group (41.90%), indicating that the NY50C protease itself has a certain water retention improvement ability.

[0056] The cooking loss of the synergistic treatment group (Example 4) was reduced to 21.68%, which was 48.26% lower than that of the blank group and significantly lower than that of the L-arginine alone group (27.64%) and the NY50C protease alone group (31.52%), demonstrating that L-arginine and NY50C protease have a synergistic effect.

[0057] The cooking and thawing losses of commonly used ascorbic acid oxidase (Comparative Example 3) and kiwi protease (Comparative Example 4) were significantly worse than those of the NY50C protease alone and in combination treatment groups of the present invention, indicating that the enzymes in the prior art are not suitable for maintaining the quality of frozen duck meat during long-term storage.

[0058] The embodiments provided above are not intended to limit the scope of the invention, nor are the described steps intended to limit the order of execution. Any obvious modifications made to the invention by those skilled in the art based on existing common knowledge also fall within the scope of protection defined by the claims.

Claims

1. A method for improving the distinctive fishy smell of frozen duck meat, characterized in that, The method includes the following: Dissolve NY50C protease in water to form an enzyme treatment solution, inject it evenly into the duck meat, let it stand at 4℃ for 12-24 hours, and then freeze it for preservation.

2. The method according to claim 1, characterized in that, The enzyme treatment solution also contains salt, with the amount of salt added being 0.8% to 1.2% based on the weight of the duck meat.

3. The method according to claim 1, characterized in that, The amount of NY50C protease used is 0.005%~0.02%, based on the weight of duck meat.

4. The method according to claim 1, characterized in that, The NY50C protease is derived from Bacillus and has an enzyme activity of 50,000~100,000 U / g.

5. The method according to claim 1, characterized in that, The amount of enzyme treatment solution injected is 10% to 20% of the weight of the duck meat.

6. The method according to claim 1, characterized in that, The special fishy-smelling substances include trans-2-octenal, (E,E)-2,4-decadienal, 1-octen-3-one, 1-octen-3-ol, and octanoic acid.

7. The method according to claim 1, characterized in that, The enzyme treatment solution also includes L-arginine, with the amount of L-arginine added being 0.4% to 0.8% based on the weight of duck meat.

8. The method according to claim 7, characterized in that, The mass ratio of L-arginine to NY50C protease in the enzyme treatment solution is 30:1 to 160:

1.

9. A method for improving the quality of frozen duck meat, characterized in that, The method includes the following: Dissolve NY50C protease, L-arginine, and salt in water to form an enzyme treatment solution, inject it evenly into the duck meat, let it stand at 4°C for 12-24 hours, and then freeze it for preservation.

10. The application of the method according to any one of claims 1 to 9 in processed duck meat products.

Images