Preparation method of polyelectrolyte type nanoemulsion for frozen meat preservation and ice-coating method thereof

Abstract

The application discloses a preparation method of polyelectrolyte nanoemulsion for frozen meat preservation and an ice-coating method of the polyelectrolyte nanoemulsion, and has the characteristics that the method comprises the following steps: 1) filtering the thawing juice of collected frozen meat, and then performing ultrafiltration centrifugation by using a 8-10 kDa filter membrane; taking the filtrate, and obtaining an antifreeze peptide powder through freeze-drying; 2) slowly adding water-soluble sodium carboxymethyl cellulose into a chitosan solution to make the final mass concentration of the sodium carboxymethyl cellulose be 0.6-1%, and simultaneously adding the antifreeze peptide powder to make the final mass concentration of the antifreeze peptide powder be 6-10%, and then magnetically stirring to obtain a matrix aqueous solution; and 3) adding soybean oil containing essential oil drop by drop into the matrix aqueous solution with a volume of 8-12 times of the soybean oil, homogenizing by using a high-speed homogenizer, and then performing homogenization treatment by using a high-pressure homogenizer, and repeating the homogenization and the homogenization treatment for 3-8 times, so as to obtain the polyelectrolyte nanoemulsion, and the polyelectrolyte nanoemulsion has the advantages of good adhesion, good preservation effect, the ability to improve the quality of the frozen meat and the ability to prolong the shelf life of products.

Description

Technical Field

[0001] The present invention relates to the technical field of antifreeze and fresh-keeping of frozen meat, in particular to a preparation method of a polyelectrolyte nanoemulsion for preserving frozen meat and an ice coating method thereof. Background Art

[0002] Frozen storage, the most common method of preserving meat, significantly extends shelf life by inhibiting the growth of putrefactive microorganisms and inactivating enzyme activity. Currently, frozen meat in my country is primarily used as a raw material for deep processing into minced meat products. However, during the frozen storage of fresh meat, ice crystal recrystallization and solute concentration induce oxidative denaturation of muscle protein, fat oxidation, and severe damage to the tissue structure. Simultaneously, ice crystal sublimation causes a decrease in moisture content and can even cause desiccation of the muscle surface. Thawed meat often exhibits quality deterioration, including severe juice loss, dull color, and decreased protein gel properties, severely impacting the quality of processed meat products.

[0003] An emulsion is a colloidal dispersion system formed by mixing two immiscible solutions. Based on their structure, emulsions are generally classified into two main categories: water-in-oil (W / O) and oil-in-water (O / W). However, emulsions are non-equilibrium systems and are prone to instability such as sedimentation, stratification, and flocculation during long-term storage. Nanoemulsions are emulsions with particle sizes ranging from 1 to 100 nm. Due to their small size and surface effects, nanoemulsions exhibit increased stability and improved controlled and targeted release of bioactive ingredients. Plant essential oils possess excellent antioxidant and antimicrobial properties and are currently used as natural additives in food preservation. However, their poor water solubility, volatility, and strong odor significantly limit their application in muscle foods. Chitosan is a natural cationic polysaccharide composed of (1,4)-linked 2-amino-deoxy-bD-glucans, produced by the deacetylation of chitin. Given its non-toxic, antioxidant and antibacterial properties, chitosan is widely used in the food industry as a preservative.

[0004] Glazing involves quickly placing frozen fresh meat in a glazing solution for tens of seconds, then quickly removing it. This method protects the meat from surface drying out, fat freezer burn, and other quality degradation during low-temperature storage. Currently, traditional tap water or drinking water glazing has weak adhesion and is prone to cracking during frozen storage. This makes it less effective in slowing down surface moisture evaporation, protein denaturation, and fat oxidation. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a polyelectrolyte nanoemulsion with good adhesion and preservation effect for preserving frozen meat and a method for coating the ice layer thereof, which can improve the quality of frozen meat and extend the shelf life of the product.

[0006] The technical solution adopted by the present invention to solve the above technical problems is: a method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat, comprising the following steps:

[0007] (1) collecting the juice lost during the thawing process of frozen meat, filtering the collected thawing juice through a 200-mesh sieve, ultrafiltration using an 8-12 kDa filter membrane, centrifuging at 2500-3500 r / min for 10-20 minutes, and freeze-drying the filtrate to obtain antifreeze peptide powder;

[0008] (2) chitosan is added to a glacial acetic acid solution with a volume concentration of 0.5-1.5%, and the solution is placed in a water bath at 45-55°C and magnetically stirred at a speed of 400-600 r / min for 1-3 hours to obtain a 4-6 g / L chitosan solution. Water-soluble sodium carboxymethyl cellulose is slowly added to the chitosan solution to make its final mass concentration 0.6-1%. At the same time, antifreeze peptide powder is added to make its final mass concentration 6-10%, and magnetic stirring is carried out at a speed of 400-600 r / min for 10-20 minutes to obtain a matrix aqueous phase solution;

[0009] (3) Soybean oil containing essential oil is added dropwise to a matrix aqueous phase solution with a volume of 5 to 15 times that of soybean oil, homogenized for 1 to 5 minutes at a speed of 10,000 to 14,000 r / min using a high-speed homogenizer, and then homogenized by a high-pressure homogenizer at a pressure of 15 to 20 MPa. After repeating the homogenization and homogenization treatment 3 to 8 times, a polyelectrolyte nanoemulsion is obtained.

[0010] Preferably, the method comprises the following steps:

[0011] (1) collecting the juice lost during the thawing process of frozen meat, filtering the collected thawing juice through a 200-mesh sieve, ultrafiltration using a 10 kDa filter membrane, centrifuging at 3000 r / min for 150 min, and freeze-drying the filtrate to obtain antifreeze peptide powder;

[0012] (2) Chitosan was added to a 1% glacial acetic acid solution by volume, and the solution was placed in a 50°C water bath and magnetically stirred at 400-600 r / min for 2 h to obtain a 5 g / L chitosan solution. Water-soluble sodium carboxymethyl cellulose was slowly added to the chitosan solution to a final mass concentration of 0.8%. Antifreeze peptide powder was also added to a final mass concentration of 6-10%, and magnetically stirred at 500 r / min for 15 min to obtain a matrix aqueous solution.

[0013] (3) Soybean oil containing essential oil is added dropwise to a matrix aqueous solution with a volume 10 times that of soybean oil, homogenized for 3 min at a speed of 12000 r / min using a high-speed homogenizer, and then homogenized using a high-pressure homogenizer at a pressure of 20 MPa. After repeating the homogenization and homogenization treatment 3 to 8 times, a polyelectrolyte nanoemulsion is obtained.

[0014] Preferably, the preparation method of the soybean oil containing essential oil in step (3) is as follows: 5-10 mL of thyme essential oil and 5-10 mL of oregano essential oil are fully dissolved in 100 mL of soybean oil, and magnetically stirred at a speed of 600-1000 r / min for 10-20 min until uniformly dispersed, thereby obtaining soybean oil containing essential oil.

[0015] A method for coating frozen meat with an ice glaze using the polyelectrolyte nanoemulsion prepared by the above method, comprising the following steps: taking 2 to 4 kg of fresh meat, removing the tendons and fat on the surface, freezing the meat in a -80 to -60°C cold storage for 24 hours, immediately placing the meat in a polyelectrolyte nanoemulsion after taking it out, and soaking it in a -4 to 0°C cold storage for 25 seconds, thereby coating the meat surface with an ice glaze, wherein the amount of the ice glaze is controlled to be 10 to 14% of the weight of the meat block, and freezing the meat in a -18°C cold storage after the ice glaze is completed.

[0016] Furthermore, the meat includes pork, beef and mutton.

[0017] Compared with the prior art, the advantages of the present invention are as follows: a method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat and an ice coating method thereof, wherein the low-cost and high-solubility frozen meat thawing loss juice is subjected to ultrafiltration technology to intercept small-molecule protein peptides, thereby forming an antifreeze polypeptide rich in α-helical structure and hydrophilic amino acids, which can provide a certain number of sites capable of binding to water molecules, enhance the stability of muscle water molecules during the freezing process, and prevent the growth of ice crystals during the frozen storage of frozen meat; the chitosan used as a polyelectrolyte positively charged polysaccharide has the effects of preventing the rapid sublimation and loss of ice crystals, inhibiting lipid and protein oxidation, and slowing down the fading of meat products; thyme essential oil and oregano essential oil have antibacterial and antioxidant functions, and cooperate with soybean oil and the aqueous component sodium carboxymethyl cellulose as a thickener to achieve a good adhesion effect on frozen meat; oil-in-water (O / W) type nanoemulsion can be used as an effective carrier for encapsulating hydrophobic essential oils, improving their solubility and stability, reducing the volatilization of the effective ingredients of the essential oils and the sensory stimulation to the food; in addition, the prepared polyelectrolyte nanoemulsion has the advantages of good dispersibility, high stability, and convenient spraying. The nanoemulsion is further used as an ice coating liquid to adhere to the surface of frozen meat. The nanoemulsion particles have a large specific surface area, making it easier to contact other surfaces or substances, increasing the interaction between the particles and other substances; in addition, the nanoemulsion ion surface energy is high. Since the particles tend to interact with the surrounding environment to reduce their surface energy, it means stronger adsorption and adhesion, with the advantages of strong adhesion and not easy to crack and fall off, thereby better improving the quality deterioration problems of frozen meat such as surface moisture evaporation, protein denaturation, and fat oxidation during long-term storage.

[0018] In summary, the present invention provides a method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat and a method for coating the glaze thereon. The nanoemulsion is used as the glazing liquid for frozen meat. Due to the small diameter and large total surface area of ​​the nanoparticles, the contact area between the nanoparticles and the frozen meat is increased, the effect of the small molecule antifreeze peptides in the thawing juice in delaying the growth of ice crystals and the antioxidant effect of the plant essential oil are improved, and better efficacy is shown in terms of dispersibility and stability, which can effectively improve the preservation effect of frozen meat during long-term frozen storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 The relative content of amino acids in the hydrolysis of small molecule antifreeze peptides in thawed juice;

[0020] Figure 2 The relative content results of the secondary structure of small molecule antifreeze peptides in thawed juice. DETAILED DESCRIPTION

[0021] The present invention will be described in further detail below with reference to the accompanying drawings and embodiments.

[0022] I. Experimental Methods

[0023] 1. Anti-freeze peptide structural property analysis index

[0024] Amino acid content determination: Amino acid analyzer was used, and the reference was GB5009.124-2016 “National Food Safety Standard Determination of Amino Acids in Food”.

[0025] Secondary structure analysis: Protein secondary structure was determined by Raman spectrometer, the scanning range was 500-2000 cm-1, the excitation wavelength was set to 785 nm, the acquisition time was 5 s, and the scanning number was 40 times.

[0026] 2. Basic quality index

[0027] Thawing loss determination: The mass change of the meat sample before freezing and after thawing was recorded, and the mass loss ratio was calculated.

[0028] Dry loss determination: The mass of the meat sample before freezing and the mass of the frozen meat after removing the surface ice were recorded, and the mass loss ratio was calculated.

[0029] Cooking loss determination: The thawed meat was cut into pieces of about 10 cm x 6 cm x 6 cm, heated in a 75°C water bath for 30 min, and the mass loss ratio before and after cooking was recorded.

[0030] Water holding capacity determination: About 5g of thawed meat was wrapped with filter paper and placed in a centrifuge tube, and centrifuged at 5000 r / min for 10 min at 4°C, and the mass ratio before and after centrifugation was recorded.

[0031] Color determination: Colorimeter was used to detect the brightness L * value, a * value and b * value of the meat sample. After the instrument was calibrated with a white board, the sample was placed flat on the stage for measurement.

[0032] Shear force determination: According to NY / T1180-2006 “Determination of Meat Tenderness Shear Force Determination Method”, tenderness instrument was used for determination.

[0033] Texture determination: The cooked meat pieces were cut along the muscle fiber direction into uniform meat samples of about 15 mm x 15 mm x 15 mm, P / 36R probe was used for determination, TPA mode was selected, deformation was set to 50%, pre-measurement speed was set to 5 mm / s, and post-measurement speed was 1 mm / s.

[0034] 3. Myofibrillar protein denaturation index

[0035] Extraction of myofibrillar proteins: 5 g of thawed meat was weighed and added to 20 mL of extraction buffer (0.1 mol / L KCl, 10 mmol / L KH2PO4 / K2HPO4, 2 mM MgCl2, 2 mM EGTA, pH 7.0). The sample was homogenized in a high-speed homogenizer for 1 min and then centrifuged at 10,000 g for 15 min. The precipitate was re-suspended in extraction buffer and the procedure was repeated twice more. The myofibrillar protein precipitate was stored in crushed ice and the protein concentration was determined using a BCA kit. The protein concentration was adjusted using PBS buffer (0.6 M NaCl, 50 mM NaH2PO4 / Na2HPO4, pH 7.0, 4°C).

[0036] Surface hydrophobicity determination: Bromophenol blue (BPB) was used as a probe. One mL of myofibrillar protein solution (2 mg / mL) was added to 80 μL of BPB solution (1 mg / mL). After 10 min of incubation at room temperature, the supernatant was collected by centrifugation at 10,000 g for 3 min. The supernatant was diluted 10-fold and the absorbance of the protein sample was measured at 595 nm. The results were expressed as μg BPB / mg protein.

[0037] Free thiol determination: The DTNB probe was used to characterize the free thiol groups. The protein sample was diluted to 1 mg / mL. Accurately 0.5 mL of the protein sample was added to 4.5 mL of phosphate buffer containing 8 M urea (0.1 mol / L K2HPO4, 0.01 mol / L EDTA, pH 6.0). Then, 100 μL of buffer containing 0.01 mol / L DTNB (0.01 mol / L KH2PO4, pH 6.0) was added. After mixing, the sample was incubated for 30 min. The absorbance was measured at 412 nm. Each gradient was repeated three times. The concentration of the thiol groups was calculated based on the absorption coefficient of 13600 mol -1 cm -1 , expressed as nmol / mg protein.

[0038] Carbonyl determination: 2 mg / mL of myofibrillar protein solution was added to an equal volume of 10 mM DNPH-hydrochloric acid solution. After 1 h of incubation in the dark, the reaction was stopped by adding trichloroacetic acid solution (10%, w / v). The precipitate was collected by centrifugation at 10,000 g for 5 min. The precipitate was washed three times with ethanol / ethyl acetate (1 : 1, v / v) by centrifugation at 10,000 g for 5 min. The precipitate was dissolved in 6 M guanidine hydrochloride-hydrochloric acid and incubated at 37°C for 15 min. The absorbance of the solution was measured at 370 nm. The carbonyl content was expressed as nmol / mg protein.

[0039] 4. Lipid oxidation index

[0040] Determination of thiobarbituric acid reaction value (TBARS): According to GB5009.181-2016 "National Food Safety Standard Determination of Malondialdehyde in Food", the spectrophotometric method is used and the results are expressed as mg / kg.

[0041] Determination of peroxide value (POV): The POV in the sample was determined by the colorimetric method in accordance with GB / T5009.37-2003 "Analytical method for hygienic standard of edible vegetable oils", and the result was expressed as mmol / kg. 2. Specific embodiments

[0043] Example 1

[0044] A method for preparing a polyelectrolyte nanoemulsion for preserving frozen pork and coating the same comprises the following steps: 1. directly collecting waste juice lost during thawing of industrial frozen meat from a meat product slaughterhouse, placing a tray wrapped in plastic film under a shelf containing frozen meat, collecting the juice lost during the thawing process of the frozen meat, and continuously collecting the juice for 18-24 hours; first filtering the collected thawed juice through a 200-mesh sieve, then ultrafiltering it through a 10 kDa filter membrane, and centrifuging it at 3000 rpm for 15 minutes to obtain an antifreeze peptide solution with a molecular weight of less than or equal to 10 kDa; freeze-drying the solution to obtain an antifreeze peptide powder, which is then frozen and stored at -20°C for later use;

[0045] 2. Take 0.5 g of chitosan and add it to 100 mL of 1% glacial acetic acid solution, heat it in a water bath at 50°C and stir it magnetically at 500 r / min for 2 h to obtain a chitosan solution. Slowly add water-soluble sodium carboxymethyl cellulose to the chitosan solution to make its final mass concentration 0.8%. At the same time, add antifreeze peptide powder to make its final mass concentration 8%. Stir it magnetically at 500 r / min for 15 min to obtain a matrix aqueous solution.

[0046] 3. 8 mL of thyme essential oil and 7 mL of oregano essential oil were fully dissolved in 100 mL of soybean oil, magnetically stirred at 800 r / min for 15 min until uniformly dispersed, and then added dropwise to a matrix aqueous phase solution 10 times the volume of soybean oil. After homogenization at a speed of 12000 r / min for 3 min using a high-speed homogenizer, homogenization was performed by a high-pressure homogenizer at a pressure of 20 MPa. After 5 homogenization and homogenization cycles, a polyelectrolyte nanoemulsion was obtained, which was pre-cooled in a -2 ° C cold storage for standby use;

[0047] 4. Take about 3 kg of fresh pork, remove the tendons and fat on the surface, freeze it in a -80 ° C cold storage for 24 hours, and immediately place it in the polyelectrolyte nanoemulsion prepared in step 3 after taking it out. Soak it in a -2 ° C cold storage for 25 seconds to coat the surface of the meat with a layer of ice coating. The amount of ice coating is controlled at 12% of the weight of the meat. After the ice coating is completed, it is placed in a -18 ° C cold storage for 12 months.

[0048] Example 2

[0049] A method for preparing a polyelectrolyte nanoemulsion for preserving frozen beef and coating the same comprises the following steps: 1. directly collecting waste juice lost during thawing of industrial frozen meat from a meat product slaughterhouse, placing a tray wrapped in plastic film under a shelf containing frozen meat, collecting the juice lost during the thawing process of the frozen meat, and continuously collecting the juice for 18-24 hours; first filtering the collected thawed juice through a 200-mesh sieve, then ultrafiltering it through a 10 kDa filter membrane, and centrifuging it at 3000 rpm for 15 minutes to obtain an antifreeze peptide solution with a molecular weight of less than or equal to 10 kDa; freeze-drying the solution to obtain an antifreeze peptide powder, and freezing and storing the powder at -20°C for later use;

[0050] 2. Take 0.5 g of chitosan and add it to 100 mL of 1% glacial acetic acid solution, heat it in a water bath at 50°C and stir it magnetically at 500 r / min for 2 h to obtain a chitosan solution. Slowly add water-soluble sodium carboxymethyl cellulose to the chitosan solution to make its final mass concentration 0.6%. At the same time, add antifreeze peptide powder to make its final mass concentration 6%. Stir it magnetically at 500 r / min for 15 min to obtain a matrix aqueous solution.

[0051] 3. 5 mL of thyme essential oil and 10 mL of oregano essential oil were fully dissolved in 100 mL of soybean oil, magnetically stirred at 800 r / min for 15 min until uniformly dispersed, and then added dropwise to a matrix aqueous phase solution 10 times the volume of soybean oil. After homogenization at a speed of 12000 r / min for 3 min using a high-speed homogenizer, homogenization was performed by a high-pressure homogenizer at a pressure of 20 MPa. After 5 homogenization and homogenization cycles, a polyelectrolyte nanoemulsion was obtained, which was pre-cooled in a -2 ° C cold storage for standby use;

[0052] 4. Take about 4 kg of fresh beef, remove the surface tendons and fat, freeze it in a -80°C cold storage for 24 hours, and immediately place it in the polyelectrolyte nanoemulsion prepared in step 3 after taking it out. Soak it in a -2°C cold storage for 30 seconds to coat the meat with a layer of ice coating. The amount of ice coating is controlled at 10% of the weight of the meat. After the ice coating is completed, place it in a -18°C cold storage for 12 months.

[0053] Example 3

[0054] A method for preparing a polyelectrolyte nanoemulsion for preserving frozen mutton and coating the same comprises the following steps: 1. directly collecting waste juice lost during thawing of industrial frozen meat from a meat product slaughterhouse, placing a tray wrapped in plastic film under a shelf containing frozen meat, collecting the juice lost during the thawing process of the frozen meat, and continuously collecting the juice for 18-24 hours; first filtering the collected thawed juice through a 200-mesh sieve, then ultrafiltering it through a 10 kDa filter membrane, and centrifuging it at 3000 rpm for 15 minutes to obtain an antifreeze peptide solution with a molecular weight of less than or equal to 10 kDa; freeze-drying the solution to obtain an antifreeze peptide powder, which is then frozen and stored at -20°C for later use;

[0055] 2. Take 0.5 g of chitosan and add it to 100 mL of 1% glacial acetic acid solution, heat it in a water bath at 50°C and stir it magnetically at 500 r / min for 2 h to obtain a chitosan solution. Slowly add water-soluble sodium carboxymethyl cellulose to the chitosan solution to make the final mass concentration of 1%. At the same time, add antifreeze peptide powder to make the final mass concentration of 10%. Stir it magnetically at 500 r / min for 15 min to obtain a matrix aqueous solution.

[0056] 3. Dissolve 10 mL of thyme essential oil and 5 mL of oregano essential oil in 100 mL of soybean oil, stir magnetically at 800 r / min for 15 min until uniformly dispersed, and then add dropwise to a matrix aqueous phase solution 10 times the volume of soybean oil. Use a high-speed homogenizer to homogenize at a speed of 12000 r / min for 3 min, and then use a high-pressure homogenizer to homogenize at a pressure of 20 MPa. After 5 homogenization and homogenization cycles, a polyelectrolyte nanoemulsion is obtained, which is placed in a -2 ° C cold storage for precooling.

[0057] 4. Take about 2 kg of fresh mutton, remove the surface tendons and fat, freeze it in a -80 ° C cold storage for 24 hours, and immediately place it in the polyelectrolyte nanoemulsion prepared in step 3 after taking it out. Soak it in a -2 ° C cold storage for 20 seconds to coat the surface of the meat with a layer of ice coating. The amount of ice coating is controlled at 14% by mass of the meat. After the ice coating is completed, it is placed in a -18 ° C cold storage for 12 months.

[0058] In addition to the above embodiments, the centrifugal speed in step (1) can also be 2500r / min, 3500r / min and any value within 2500-3500r / min, and the time is 10min, 20min and any value within 10-20min; the mass concentration of the glacial acetic acid solution in step (2) is 0.5%, 1.5% and any value within 0.5-1.5%, the water bath temperature is 45°C, 55°C and any value within 45-55°C, and the magnetic stirring speed is 400r / min, 600r / min and any value within 400-600r / min. value, the time is 1h, 3h and any value within 1 to 3h, the concentration of the chitosan solution is 4g / L, 6g / L and any value within 4 to 6g / L; the volume of the matrix aqueous phase solution in step (3) is 5 times, 15 times and any value within 5 to 15 times that of soybean oil, the speed of the homogenizer is 10000r / min, 14000r / min and any value within 10000 to 14000r / min, the homogenization time is 1min, 5min and any value within 1 to 5min, and the homogenization pressure is 15MPa, 20MPa and any value within 15 to 20MPa.

[0059] 3. Analysis of experimental results

[0060] 1. Analysis of the identification results of small molecule antifreeze peptides in thawed juice

[0061] like Figure 1 As shown in the figure, the obtained thawed juice small molecule antifreeze peptides are rich in hydrophilic amino acids, including aspartic acid, threonine, serine, glutamic acid, tyrosine, histidine, and lysine; hydrophobic amino acids include glycine, alanine, valine, methionine, isoleucine, leucine, and phenylalanine, accounting for 68.42% of the total amino acid content, among which histidine has the highest content, accounting for 42.10% of the total amino acid content; as shown in the figure. Figure 2 As shown, the small molecule antifreeze peptides in the thawed juice are rich in α-helical structure, with a relative content of 22.68%.

[0062] 2. Analysis of product results of the embodiment

[0063] Taking the longissimus dorsi muscle of different livestock meat as an example, the quality indicators of the longissimus dorsi muscle of the frozen meat in Examples 1 to 3 were measured after thawing in a 4°C cold storage for 12 hours, and the frozen meat without glaze treatment and the frozen meat treated with sterile water glaze in each example were used as controls.

[0064] 2.1 Example 1 The changes in quality indicators of nanoemulsion-glazed frozen pork during frozen storage are shown in Table 1.

[0065] Table 1 Quality changes of nanoemulsion-glazed frozen pork during frozen storage

[0066]

[0067]

[0068]

[0069] As shown in Table 1, compared with the blank control without glaze and sterile water glaze, the nanoemulsion glaze treatment significantly improved the problems of frozen pork in the process of 12 months of frozen storage, such as decreased water retention, deterioration of color and texture, protein denaturation, and fat oxidation.

[0070] Indicators such as thawing loss, drying loss, cooking loss, and centrifugal water retention are often used to assess the water retention of frozen meat. Compared to the unglazed control group, the frozen pork in Example 1 showed a 33.6% decrease in thawing loss, a 42.6% decrease in drying loss, a 12.2% decrease in cooking loss, and a 32.2% increase in muscle water retention after the frozen storage period. Compared to the sterile water glaze control group, the thawing loss of Example 1 decreased by 26.8%, a 34.0% decrease in drying loss, a 6.9% decrease in cooking loss, and a 22.3% increase in muscle water retention.

[0071] Meat color is a key indicator of muscle sensory quality. During 12 months of storage, the L* and a* values ​​of frozen pork decreased, while the b* value increased, indicating that freezing significantly reduced the brightness and redness of the pork and increased its yellowness. Analysis of the L*, a*, and b* values ​​showed that compared to the unglazed control sample, Example 1 had an L* value increase of 12.7%, an a* value increase of 49.9%, and a b* value decrease of 26.8%. Compared to the sterile water-glazed sample, Example 1 had an L* value increase of 7.6%, an a* value increase of 24.9%, and a b* value decrease of 19.6%.

[0072] Shear force, along with hardness, elasticity, cohesion, and chewiness, are important indicators for evaluating the tenderness and texture of frozen meat after thawing. The shear force results in Table 1 show that muscle shear force increases significantly during frozen storage. Compared to the unglazed blank control group and the sterile water-glazed control group, the shear force values ​​in Example 1 decreased by 12.3% and 9.0%, respectively, demonstrating that nano-glazing treatment significantly improves the loss of muscle tenderness caused by frozen storage.

[0073] From the texture index results, it can be seen that compared with the blank control group without ice coating and the sterile water-plated ice coating control group, Example 1 exhibits better texture properties, with the hardness values ​​reduced by 9.6% and 5.5% respectively, and the elasticity values ​​increased by 29.1% and 18.3% respectively.

[0074] Based on myofibrillar protein denaturation indicators, compared with other control examples, nanoemulsion glazing treatment significantly inhibited the increase in myofibrillar protein surface hydrophobicity and carbonyl groups, and the decrease in free sulfhydryl groups during 12 months of frozen storage in frozen pork. Compared with the blank control group without glaze, after 12 months of frozen storage, the surface hydrophobicity value of the protein in Example 1 decreased by 14.7%, the free sulfhydryl group value increased by 44.2%, and the carbonyl group value decreased by 33.2%. Compared with the sterile water glaze control group, the surface hydrophobicity value of the protein in Example 1 decreased by 11.1%, the free sulfhydryl group value increased by 20.1%, and the carbonyl group value decreased by 23.1%.

[0075] As shown by fat oxidation indicators, nanoemulsion glazing significantly inhibited the increase in TBARS and POV values ​​of frozen pork during 12 months of frozen storage compared to other control examples. After the end of the frozen storage period, TBARS and POV values ​​of Example 1 decreased by 33.2% and 34.8%, respectively, compared to the no-glaze group; and by 24.9% and 30.1%, respectively, compared to the sterile water glaze group.

[0076] 2.2 Example 2 The changes in quality indicators of nanoemulsion-glazed frozen beef during storage are shown in Table 2.

[0077] Table 2 Quality changes of nanoemulsion-coated frozen beef during storage

[0078]

[0079]

[0080] As shown in Table 2, compared with the unglazed control and sterile water glazing, nanoemulsion glazing significantly improved frozen beef's water retention, color and texture deterioration, protein denaturation, and fat oxidation during 12 months of frozen storage. Analysis of muscle water retention indicators showed that compared with the unglazed control, thawing loss decreased by 26.4%, drying loss decreased by 36.9%, and cooking loss decreased by 13.7%, while muscle water holding capacity increased by 18.1%. Compared with the sterile water glazing control, thawing loss decreased by 19.6%, drying loss decreased by 24.0%, and cooking loss decreased by 9.9%, while muscle water holding capacity increased by 10.9%. Color difference analysis revealed that the L*, a*, and b* values ​​of the frozen beef showed a significant downward trend during the 12-month frozen storage period. Compared to the unglazed blank control sample, the L*, a*, and b* values ​​of Example 2 increased by 16.8%, 30.8%, and 24.9%, respectively. Compared to the sterile water-glazed sample, the L*, a*, and b* values ​​of Example 2 increased by 11.2%, 16.5%, and 11.9%, respectively. Analysis of tenderness and texture indices showed that compared to the unglazed blank control and the sterile water-glazed control, the shear force values ​​of Example 2 decreased by 19.1% and 13.2%, respectively, the hardness values ​​decreased by 6.8% and 4.8%, respectively, and the elasticity values ​​increased by 45.2% and 18.4%, respectively. This indicates that the nanoemulsion-glazed frozen beef can maintain good textural properties even during extended frozen storage. According to myofibrillar protein denaturation indicators, after 12 months of frozen storage, compared with the blank control group without glaze, the surface hydrophobicity of the protein in Example 2 decreased by 22.6%, the free sulfhydryl group increased by 29.8%, and the carbonyl group decreased by 30.9%. Compared with the sterile water glaze control group, the surface hydrophobicity of the protein in Example 2 decreased by 16.5%, the free sulfhydryl group increased by 17.7%, and the carbonyl value decreased by 23.4%. Analysis of fat oxidation indicators showed that compared with the non-glaze group, the TBARS and POV values ​​of Example 2 decreased by 38.6% and 44.9%, respectively, after 12 months of frozen storage; compared with the sterile water glaze group, the TBARS and POV values ​​of Example 2 decreased by 27.6% and 36.1%, respectively.

[0081] 2.3 Example 3 The changes in quality indicators of nanoemulsion-glazed frozen mutton during frozen storage are shown in Table 3.

[0082] Table 3 Quality changes of nanoemulsion-coated frozen mutton during frozen storage

[0083]

[0084]

[0085] As shown in Table 3, compared with the blank control without glaze and the sterile water glaze, the nanoemulsion glaze treatment significantly improved the problems of decreased water retention, color and texture deterioration, protein denaturation, and fat oxidation in frozen mutton during 12 months of frozen storage. According to the results of muscle water retention index analysis, compared with the blank control without glaze, the thawing loss of Example 3 after 12 months of frozen storage decreased by 34.0%, the drying loss decreased by 36.4%, and the cooking loss decreased by 12.7%, while the muscle water holding capacity increased by 21.2%. Compared with the sterile water glaze control, the thawing loss of Example 3 decreased by 23.3%, the drying loss decreased by 26.4%, and the cooking loss decreased by 7.9%, while the muscle water holding capacity increased by 13.7%. Color difference analysis revealed a significant decrease in the L*, a*, and b* values ​​of frozen mutton during 12 months of frozen storage. Compared to the unglazed control sample, the L*, a*, and b* values ​​of Example 3 increased by 21.4%, 27.5%, and 29.5%, respectively. Compared to the sterile water-glazed sample, the L*, a*, and b* values ​​of Example 3 increased by 15.2%, 14.8%, and 14.3%, respectively. Tenderness and texture analysis revealed that nanoemulsion glazing effectively maintained the textural properties of frozen beef during 12 months of frozen storage. Compared to the unglazed control and sterile water-glazed controls, the shear force of Example 3 decreased by 15.5% and 9.4%, the hardness decreased by 7.2% and 5.3%, and the springiness increased by 44.0% and 24.1%, respectively. Analysis of myofibrillar protein denaturation showed that at the end of the 12-month frozen storage period, the surface hydrophobicity of the protein in Example 3 decreased by 20.2% and 15.2%, respectively, compared to the no-glaze blank control group and the sterile water-glazed control group. Free sulfhydryl groups increased by 16.9% and 10.0%, respectively, and carbonyl groups decreased by 33.0% and 23.7%, respectively. Analysis of fat oxidation showed that the TBARS and POV values ​​of the frozen lamb in Example 3 decreased by 38.5% and 37.6%, respectively, compared to the no-glaze blank control group. Compared to the sterile water-glazed control group, the TBARS and POV values ​​of Example 3 decreased by 25.9% and 28.0%, respectively.

[0086] The above description is not intended to limit the present invention, and the present invention is not limited to the above examples. Any changes, modifications, additions or substitutions made by persons of ordinary skill in the art within the spirit and scope of the present invention shall also fall within the scope of protection of the present invention.

Claims

1. A method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat, characterized in that The following steps are involved: (1) Collect the juice lost during the thawing process of frozen meat, filter the collected thawed juice, and then ultrafilter it using an 8-12 kDa filter membrane. Centrifuge it at 2500-3500 r / min for 10-20 min, and freeze-dry the filtrate to obtain antifreeze peptide powder. (2) Chitosan was added to a 0.5-1.5% volume concentration of glacial acetic acid solution, and the solution was placed in a 45-55°C water bath and magnetically stirred at 400-600 r / min for 1-3 h to obtain a 4-6 g / L chitosan solution. Water-soluble sodium carboxymethyl cellulose was slowly added to the chitosan solution to make its final mass concentration 0.6-1%. Antifreeze peptide powder was also added to make its final mass concentration 6-10%. The solution was magnetically stirred at 400-600 r / min for 10-20 min to obtain a matrix aqueous phase solution. (3) Add soybean oil containing essential oil dropwise into a matrix aqueous solution with a volume of 5 to 15 times that of soybean oil, homogenize it with a high-speed homogenizer at a speed of 10,000 to 14,000 r / min for 1 to 5 minutes, and then homogenize it with a high-pressure homogenizer at a pressure of 15 to 20 MPa. Repeat the homogenization and homogenization treatment 3 to 8 times to obtain a polyelectrolyte nanoemulsion.

2. The method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat according to claim 1, characterized in that The following steps are involved: (1) The juice lost during the thawing process of frozen meat was collected, the collected thawed juice was filtered through a 200-mesh sieve, ultrafiltered using a 10 kDa filter membrane, centrifuged at 3000 r / min for 15 min, and the filtrate was freeze-dried to obtain antifreeze peptide powder; (2) Chitosan was added to a 1% glacial acetic acid solution, and the solution was placed in a 50°C water bath and magnetically stirred at 400-600 r / min for 2 h to obtain a 5 g / L chitosan solution. Water-soluble sodium carboxymethyl cellulose was slowly added to the chitosan solution to make the final mass concentration of 0.8%. Antifreeze peptide powder was also added to make the final mass concentration of 6-10%. The solution was magnetically stirred at 500 r / min for 15 min to obtain a matrix aqueous phase solution. (3) Soybean oil containing essential oil was added dropwise to a matrix aqueous solution 10 times the volume of soybean oil. The solution was homogenized at 12,000 r / min for 3 min using a high-speed homogenizer. The solution was then homogenized at 20 MPa using a high-pressure homogenizer. The homogenization and homogenization were repeated 3 to 8 times to obtain a polyelectrolyte nanoemulsion.

3. The method for preparing a polyelectrolyte nanoemulsion for preserving frozen meat according to claim 2, characterized in that The preparation method of the soybean oil containing essential oil in step (3) is as follows: 5-10 mL of thyme essential oil and 5-10 mL of oregano essential oil are fully dissolved in 100 mL of soybean oil, and magnetically stirred at a speed of 600-1000 r / min for 10-20 min until the mixture is evenly dispersed, thereby obtaining the soybean oil containing essential oil.

4. A method for coating frozen meat with a polyelectrolyte nanoemulsion prepared by the method of claim 1, characterized in that The method comprises the following steps: taking 2 to 4 kg of fresh meat, removing the tendons and fat on the surface, freezing the meat in a -80 to -60 ℃ cold storage for 24 hours, immediately placing the meat in a polyelectrolyte nanoemulsion and soaking it in a -4 to 0 ℃ cold storage for 25 seconds to form a layer of ice coating on the surface of the meat. The amount of ice coating is controlled at 10 to 14% of the weight of the meat, and the meat is then frozen in a -18 ℃ cold storage.

5. The method for coating glaze using a polyelectrolyte nanoemulsion for preserving frozen meat according to claim 4, characterized in that: The meat includes pork, beef and mutton.

Images