Preparation method of quaternized chitosan-succinic acid-based hollow salt and its application in air-dried duck meat

Abstract

The present invention discloses a preparation method of quaternized chitosan-succinic acid-based hollow salt and its application in air-dried duck meat. The characteristics include the following steps: Quaternized chitosan, succinic acid, NaCl and deionized water are mixed and stirred evenly according to the mass ratio of 1:2.36:15:81.64, and then dissolved. After that, it is treated under ultrasonic conditions of 100W - 500W for 20 - 40 min. After the ultrasonic treatment, spray drying is carried out to obtain quaternized chitosan-succinic acid-based hollow salt embedded with NaCl. The added mass of the hollow salt used for further marinating duck meat is 6%, the air-drying time is 3 days, and the air-drying temperature is 16°C. The advantages are that it can improve the embedding amount of NaCl and the stability of the hollow structure, reduce the particle size of the hollow salt and make the size distribution uniform, increase the salinity of the hollow salt, and using the hollow salt to prepare air-dried duck meat can reduce the TVB-N and TBARS values of the duck meat and improve the sensory quality of the product.

Description

Technical Field

[0001] The present invention relates to the field of manufacturing food functional ingredients, and particularly to a method for preparing quaternized chitosan-succinic acid-based hollow salt and its application in air-dried duck meat. Background Art

[0002] Sodium chloride (NaCl) is a commonly used additive in food processing. During the processing of air-dried meat products such as dry-cured ham, air-dried duck, etc., a large amount of NaCl is required to ensure the texture, color, and prevent spoilage of the meat products. Long-term intake of high-salt foods can cause diseases such as hypertension, blood vessel blockage, chronic kidney disease, osteoporosis, etc. in the body, increasing health risks. Therefore, there is an urgent need to develop salt-reducing and salt-increasing ingredients to replace NaCl in food processing, especially for the production of air-dried meat products. Currently, common methods for reducing salt in foods include vacuum curing, high-pressure curing, pulsed curing, gamma irradiation, potassium salt substitution, calcium salt substitution, plant salt substitution, etc. Due to the problem of equipment and raw material matching, the actual use of methods such as vacuum curing is difficult; potassium salt substitution has a metallic bitterness, calcium salt substitution makes the food astringent, while plant salts may affect color, flavor, and their composition is complex, and the food safety is questionable. Therefore, it is urgent to develop a new processing method for reducing salt and increasing saltiness in foods.

[0003] In view of the limitations of traditional salt-reducing technologies, hollow salt has attracted attention as an emerging technology. This technology mixes NaCl with polysaccharide shell materials and prepares salt particles with a hollow structure through processes such as spray drying. This hollow structure can encapsulate and control the release of salt physically and chemically, achieving the purposes of enhancing the perception of saltiness, reducing the salt dosage, and improving the texture and flavor of foods. The development of hollow salt meets the demand for low-salt healthy foods in the modern food industry while maintaining a good saltiness and flavor experience. The raw materials for preparing hollow salt are usually polysaccharide substances, such as chitosan, arabic gum, carrageenan, etc. The important mechanism for polysaccharides as raw materials to increase saltiness in hollow salt can be explained from three aspects. First, polysaccharides can increase the local concentration of salty substances through their colloidal action, increasing the stimulation of taste receptors, thereby enhancing the perception of saltiness. Second, the viscosity and solubility of foods affect the diffusion and perception speed of salty substances in the mouth. By increasing the viscosity of foods, polysaccharides can slow down the release of saltiness in the mouth, prolong the perception time of saltiness, and polysaccharides can act as a physical barrier for salty substances, making them slowly release during chewing and preventing the rapid dissipation of saltiness. Third, some polysaccharides can directly interact with taste receptors, changing the taste receptors' response to Na +Sensitivity. For example, the positive charge of chitosan can interact with the negative charge on the salt taste receptor, change its sensitivity to sodium ions, and thus enhance the perception of saltiness. Preparing hollow salts using polysaccharides as raw materials through spray drying has multiple practical advantages. For example, the hollow particles formed by spray drying can effectively encapsulate NaCl, protecting it from environmental factors such as deliquescence or oxidation, and extending the shelf life of the salt. Secondly, the hollow structure can regulate the release rate of saltiness, reduce the abruptness of saltiness, making it more mild and persistent, which is particularly suitable for foods that require slow release of saltiness. And spray drying is a common industrial production technology, with simple operation and easy control, suitable for large-scale production. Moreover, the polysaccharide-salt solution can be used to prepare hollow salt particles by spray drying at one time, and the process is efficient. As a natural biopolymer, polysaccharides have the advantages of being non-toxic, biodegradable, and edible. However, there are also some problems in the preparation of hollow salts. For example, the spray drying process is greatly affected by environmental conditions (such as temperature, humidity). Too high a temperature may cause polysaccharide degradation or structural changes of the salt, and too low a temperature may affect the efficiency of spray drying and the quality stability of the product. There is also the issue of the uniformity of hollow salts: if not properly controlled during the spray drying process, it may lead to uneven distribution of polysaccharides and salts, and inconsistent saltiness performance of hollow salt particles, affecting the quality and consistency of the product. Therefore, it is particularly important to develop a preparation process for hollow salts with high stability, significant salt-enhancing effect, and uniform particles. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a method for preparing quaternized chitosan-succinic acid-based hollow salts with high stability, significant salt-enhancing effect, and uniform particles and its application in air-dried duck meat, which inhibits the lipid oxidation of air-dried duck meat and improves the sensory quality of the product.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows: A method for preparing quaternized chitosan-succinic acid-based hollow salts, comprising the following steps: After mixing and stirring evenly and dissolving quaternized chitosan, succinic acid, NaCl, and deionized water in a mass ratio of 1:2.36:15:81.64, it is treated under ultrasonic conditions of 100 - 500 W for 20 - 40 min. After the ultrasonic treatment, spray drying is carried out to obtain quaternized chitosan-succinic acid-based hollow salts encapsulating NaCl.

[0006] Preferably, during the spray drying process, the inlet air temperature of the spray dryer is set to 140 °C, the fan frequency is 10 rpm, and the solution injection speed is 20 mL / min.

[0007] Preferably, the water bath temperature is set to 60 °C during ultrasonic treatment.

[0008] Preferably, the ultrasonic power is 400 W or 500 W.

[0009] The present invention also provides the application of the quaternized chitosan-succinic acid-based hollow salt obtained by the above preparation method in air-dried duck meat.

[0010] Furthermore, the added mass percentage of the hollow salt used for marinating duck meat is 6%, the air-drying time is 3 days, and the air-drying temperature is 16 °C.

[0011] Compared with the prior art, the advantages of the present invention are as follows: for the preparation method of a quaternized chitosan-succinic acid-based hollow salt and its application in air-dried duck meat of the present invention, the crosslinking degree between quaternized chitosan and succinic acid is relatively high, making the shell layer of the hollow salt more solid. Ultrasonic treatment can make the morphology of the hollow salt smoother and fuller, reduce the breakage rate, and stabilize the crystal structure, making the particle size distribution of the hollow salt more uniform and smaller, reaching below 10 μm, which is beneficial to increasing the embedding amount of NaCl in the hollow structure, such that the Na + loading amount of the hollow salt is up to more than 300 mg / kg at most, and the dissolution temperature of the hollow salt after ultrasonic treatment increases, improving its thermal stability and being beneficial to its storage stability. The results of electronic tongue and sensory evaluation show that ultrasonic treatment at 400W and 500W can significantly increase the salinity of the hollow salt, and only 45.36 - 53.71% of the weight of pure NaCl of the hollow salt is required to achieve the salinity of pure NaCl. Further, marinating duck meat with the hollow salt inhibits the lipid oxidation of air-dried duck meat, and the overall sensory score of air-dried duck meat is higher than that marinated only with NaCl, indicating that the hollow salt also has a sensory improvement effect in practical applications. The hollow salt prepared by this method can be further expanded to the application scope of food production such as cheese and pickles in the future, and has broad application prospects in the food processing industry. Description of the Drawings

[0012] Figure 1 Shows the effects of different treatment methods on the hollow salt, where A is the crosslinking degree of the hollow salt, B is the NaCl embedding amount of the hollow salt, C is the infrared spectrum of the hollow salt, D is the X-ray diffraction pattern of the hollow salt, E is the differential scanning calorimetry (DSC) result of the hollow salt, and F is the rheological property experimental result of the hollow salt; Qac: quaternized chitosan, WB: only water bath heating treatment, without salt, WB-NaCl: only water bath heating treatment with embedded salt, US100W: ultrasonic treatment at 100W for 30 min with embedded salt, US200W: ultrasonic treatment at 200W for 30 min with embedded salt, US300W: ultrasonic treatment at 300W for 30 min with embedded salt, US400W: ultrasonic treatment at 400W for 30 min with embedded salt, US500W: ultrasonic treatment at 500W for 30 min with embedded salt;

[0013] Figure 2Taste detection of hollow salts obtained by different treatment methods using an electronic tongue and the results of actual human sensory evaluation. Among them, A is the determination of the saltiness intensity of the hollow salt solution, B is the determination of the taste richness of the hollow salt solution, C is the determination of the sourness intensity of the hollow salt solution, D is the determination of the umami intensity of the hollow salt solution, and E is the result of the actual human sensory evaluation of the hollow salt;

[0014] Figure 3 Particle size distribution of hollow salts spray-dried after different pretreatment methods. Among them, A is the particle size of the quaternized chitosan raw material, B is the particle size of the salt-free sample after water bath heating treatment, C is the particle size of the salt-containing sample after water bath heating treatment, D is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 100W, E is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 200W, F is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 300W, G is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 400W, and H is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 500W;

[0015] Figure 4 Observation results of the microstructure of hollow salts obtained by different treatment methods. Among them, A is the hollow salt obtained by water bath heating treatment, B is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 100W, C is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 200W, D is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 300W, E is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 400W, and F is the particle size of the hollow salt spray-dried after ultrasonic pretreatment at 500W;

[0016] Figure 5 Results of the effect of hollow salt pickling on air-dried duck meat obtained by different treatment methods. Among them, A is the result of the effect of hollow salt on the pH of air-dried duck meat, B is the result of the effect of hollow salt on the TVB-N of air-dried duck meat, C is the result of the effect of hollow salt on the TBARS of air-dried duck meat. The NaCl group is air-dried duck meat pickled only with 6% normal salt, the 100W group is air-dried duck meat pickled with hollow salt spray-dried after 100W ultrasonic treatment, the 200W group is air-dried duck meat pickled with hollow salt spray-dried after 200W ultrasonic treatment, the 300W group is air-dried duck meat pickled with hollow salt spray-dried after 300W ultrasonic treatment, the 400W group is air-dried duck meat pickled with hollow salt spray-dried after 400W ultrasonic treatment, and the 500W group is air-dried duck meat pickled with hollow salt spray-dried after 500W ultrasonic treatment. Specific Embodiments

[0017] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0018] Example 1. A method for preparing a quaternized chitosan-succinic acid-based hollow salt, comprising the following steps:

[0019] Dissolve 1 g of quaternized chitosan and 2.36 g of succinic acid in 81.64 mL of ultrapure water, and stir magnetically for 30 min to fully dissolve the two. Then add 15 g of NaCl and stir evenly, and place it in an ultrasonic processor. The water temperature is 60 °C, and different ultrasonic powers of 100W, 200W, 300W, 400W, and 500W are set to process for 30 min (), and then the solution is placed in a spray dryer. Set its inlet air temperature to 140 °C, the fan frequency to 10 rpm, and the solution injection speed to 20 mL / min to obtain quaternized chitosan-succinic acid-based hollow salt encapsulating NaCl.

[0020] Replace the ultrasonic treatment time in the above production process with water bath heating, and the prepared hollow salt is denoted as WB-NaCl. Replace the ultrasonic treatment time in the above production process with water bath heating and do not add NaCl, and the prepared hollow salt is denoted as WB.

[0021] Example 2, crosslinking degree of the hollow salt prepared in Example 1, Na + content determination and sensory evaluation results.

[0022] Take 5 mL of a 1wt% concentration of hollow salt solution, add 10 μL of a 1wt% toluidine blue solution to it, mix evenly, and titrate the solution with 0.1 mol / L polyvinylsulfate potassium (abbreviated as PVSK) to make the solution color change from blue to purple and not fade within 30 s. The calculation steps of the crosslinking degree are divided into two steps: First, titrate the NH2 content in the solution, NH2 (%) = (C pvsk *ΔV*161.15*100) / (5*c)*100%, C pvsk is the concentration of the PVSK reagent used, ΔV is the volume of the PVSK reagent consumed, 161.15 is the average molecular weight of quaternized chitosan, and c is the concentration of the hollow salt solution. Then further calculate the crosslinking degree Y (%) = 1 -

NH2% (b) / NH2% (a)

[0023] Take 0.2 g of hollow salt powder, dissolve it in 5 mL of nitric acid solution and let it stand for 12 h, then transfer the solution to a microwave digestion system for digestion for 20 min, and then dilute the digestion solution to 100 mL with deionized water, and use an atomic flame absorption spectrometer to measure the Na + ion content.

[0024] Dissolve the hollow salt powder in deionized water to prepare a 1% mass concentration solution. Use a pure NaCl solution with the same concentration as a control. Recruit 9 professional food sensory testers (5 males and 4 females) to measure the salinity of the samples. Before the test, use mouthwash to clean the mouth to remove odors, and then evaluate the salinity of the samples. Rinse the mouth again between the tests of each sample to remove the taste of the previous sample. Use the pure NaCl solution as 1 point. Samples with a salinity higher than the control group are scored 1 - 3 points, and samples with a salinity lower than the control group are scored -1—-3 points.

[0025] The amino groups and carboxyl groups in quaternized chitosan and succinic acid will undergo a cross-linking reaction to form a cross-linked network. When spray-drying, the cross-linked network wraps NaCl in the solution through the spray-drying nozzle to form hollow salts. The higher the degree of cross-linking, the higher the salt embedding amount. Therefore, we measured the degree of cross-linking of the hollow salt samples obtained after ultrasonic and water bath treatments. The results are as Figure 1 shown in A. Compared with the water bath treatment, ultrasonic treatment can improve the cross-linking degree of quaternized chitosan and succinic acid. Among them, the hollow salts prepared by ultrasonic treatments at 200W, 400W, and 500W have the highest degree of cross-linking. As Figure 1 shown in B is the detection result of the Na + content embedded in the hollow salt. Compared with the water bath treatment, ultrasonic treatment at 500W can increase the embedding amount of NaCl in the hollow structure. This may be because the sample treated with ultrasonic at 500W has a higher degree of cross-linking, forming a dense network structure that can firmly lock NaCl in the hollow structure.

[0026] Study on the infrared spectrum, crystal structure, and thermodynamic stability of the hollow salts prepared in Example 3 and Example 1.

[0027] Use an FTIR infrared spectrometer to analyze the chemical bonds and chemical forces in the hollow salts. Specifically, mix the hollow salts and KBr at a ratio of 1∶100 (g / g) and press them into tablets to obtain the chemical bond composition information of the hollow salts within the scanning range of 500–4000 cm -1 . Use an X-ray diffractometer to study the crystalline state of the hollow salts. Take 0.1 g of the sample and put it into the instrument, and then use 40 kV and 30 mA Cu kα radiation to measure the X-ray diffraction pattern of the sample within the diffraction angle (2θ) range from 5° to 90°. Use a differential scanning calorimeter to evaluate the thermal properties of the hollow salt samples and the changes in their internal structures. Put 3 mg of the hollow salt samples into an aluminum tray and seal it, and perform the scan within the temperature range of 25 - 250 °C at a heating rate of 20 °C / min.

[0028] As Figure 1 shown in C, water bath and ultrasonic treatments can cause covalent cross-linking of quaternized chitosan and succinic acid. At 1222 cm -1A C-N bond is formed, and sonication enhances the strength of the C-N bond, indicating that sonication promotes the crosslinking of quaternized chitosan and succinic acid. On the other hand, sonication disrupts the hydrogen bonds of the hollow salt, causing the O-H bond to shift from 3416 cm -1 to 3446 cm -1 ; the disruption of hydrogen bonds also weakens the stretching vibration intensity of the C-H bond at 2951 cm -1 . The sample heated in a water bath has an absorption peak at 1668 cm -1 , corresponding to the C=O bond, which is not present in other samples. This may be because sonication may change the morphology or crystallinity of the sample, affecting the intermolecular interactions and causing the carbonyl vibration not to exhibit an obvious absorption peak. The hollow salt has an absorption peak at 1564 cm -1 , corresponding to the C=O bond, and sonication enhances the peak absorption intensity. This may indicate that the intermolecular or intramolecular hydrogen bond interactions in the sample are weakened, placing the C=O bond in a more uniform environment, resulting in a more concentrated vibration frequency of the absorption peak and an increase in intensity. 1437 cm -1 corresponds to the bending vibration of the C-H bond, and sonication increases the peak intensity and narrows the peak shape. This may be because the molecular arrangement becomes more ordered, and the environment of the C-H bond will be more consistent, which can lead to the narrowing of the absorption peak.

[0029] As Figure 1 shown in D, the raw material of quaternized chitosan has only one diffraction peak at 20.3°, which belongs to the partial crystal characteristic structure peak of chitosan. After the crosslinking reaction of quaternized chitosan and succinic acid, this peak disappears, indicating that the reaction of quaternized chitosan and succinic acid destroys this part of the crystal structure and transforms it into an amorphous structure. The diffraction peaks at 27.4°, 31.7°, 45.5°, 56.5°, 66.2°, 75.3° and 84° all correspond to the characteristic diffraction peaks of the face-centered cubic crystal structure of NaCl, which are the 111 crystal plane, 200 crystal plane, 220 crystal plane, 222 crystal plane, 400 crystal plane, 420 crystal plane and 422 crystal plane of NaCl respectively. This shows that the hollow salt contains NaCl. Secondly, the diffraction peak intensities of the 500W group at 31.7° and 45.4° are higher than those of other groups, indicating that this group has a higher crystallinity and a higher content of embedded sodium chloride, which is consistent with the crosslinking degree measurement results and the sodium chloride measurement results.

[0030] As Figure 1As shown in Figure E, compared with the hollow salt without salt in water bath heating, embedding sodium chloride reduces the dissolution temperature of the hollow salt. This may be because sodium chloride (NaCl) dissociates into sodium ions (Na⁺) and chloride ions (Cl⁻) in quaternized chitosan. These ions interact with the quaternary ammonium cations in the quaternized chitosan molecules, weakening the electrostatic attraction between the quaternary ammonium salt molecules. This interaction reduces the binding force between molecules, resulting in a decrease in the overall stability of the system and thus a decrease in the melting point. The addition of sodium chloride may also disrupt the hydrogen bonds between molecules: the hydrogen bonds in quaternized chitosan may be disrupted or weakened in the presence of NaCl. Na⁺ and Cl⁻ ions can interact with the polar groups (such as hydroxyl and amino groups) in the chitosan molecules, disrupting the hydrogen bond network between molecules, thereby reducing the melting point. This speculation can be proven by the results of infrared spectroscopy. The dissolution temperature of the hollow salt obtained after ultrasonic pretreatment is lower than that of the sample heated in a water bath. This may be because ultrasonic treatment can make the sodium chloride particles disperse more uniformly in the quaternized chitosan matrix. This uniform distribution can lead to more interfacial regions, and the interfacial effect may reduce the thermal stability of the material, resulting in a decrease in the melting point. It may also be because ultrasonic treatment can cause partial fracture or degradation of the quaternized chitosan molecular chains, resulting in a decrease in molecular weight. This decrease in molecular weight usually leads to a decrease in the melting point of the material because the molecular chains become shorter and have higher degrees of freedom, reducing the energy required for melting. On the other hand, a lower melting point temperature can enable the hollow salt to dissolve and disperse quickly in the mouth, facilitating the diffusion of sodium chloride. However, an overly low melting point temperature will cause the hollow salt to be unstable during storage. Therefore, in summary, the hollow salts obtained under the ultrasonic treatment conditions of 100W, 200W, and 500W have better effects.

[0031] Example 4. Determination of the rheological properties of the hollow salt solution prepared in Example 1.

[0032] Dissolve the hollow salt powder in water to prepare a solution with a mass concentration of 1%. Use a rheometer to test it. Place the sample on a parallel plate (diameter 40 mm; gap 1 mm). The apparent viscosity of the hollow salt solution is evaluated at a shear rate of 0.1 to 100 s -1 at 25°C. Silicone oil is coated on the edge of the parallel plate to prevent water evaporation.

[0033] As Figure 1As shown in F, the viscosity change trend of the solution after the hollow salt is dissolved in water is presented. As the shear force increases, the viscosity of the sample gradually decreases, showing shear thinning behavior, which is a typical behavior of non-Newtonian fluids. The reason for this phenomenon is attributed to the shear-induced particle / molecular bond breakage or the non-destructive arrangement of the spatial structure of the sample in the flow direction. At high shear rates, the sample particles change from an amorphous state to an ordered state, resulting in a decrease in viscosity. The raw material of chitosan quaternary ammonium salt has a relatively high viscosity, while after cross-linking with succinic acid and spray drying, the viscosity decreases. Excessive viscosity will lead to uneven distribution after the hollow salt is dissolved, inhibiting the diffusion of salt taste. The viscosity of the sample treated with ultrasound at 100 W is higher than that of other groups, which may be because the sample obtained by the 100 W treatment has a larger particle size, resulting in stronger interactions between particles in the solution and an increase in viscosity. At higher powers, ultrasound may cause particle depolymerization or a decrease in particle size, reducing the interaction force between particles and lowering the viscosity.

[0034] Determination of the taste of the hollow salts prepared in Example 5 and Example 1 using an electronic tongue.

[0035] Weigh 0.2 g of hollow salt powder and dissolve it in 19.8 mL of deionized water to prepare a 1% concentration solution. Then, place the electronic tongue taste sensor into the solution for taste detection, using quaternized chitosan solution and pure NaCl solution at the same concentration as controls.

[0036] Figure 2 The electronic tongue evaluation results for the hollow salts are as follows, where Figure 2 A in it is the determination result of the salinity of the hollow salt. Blank is a 1% NaCl solution as the control group. Compared with the control group, the salinity of the hollow salts obtained after water bath heating treatment and ultrasonic treatment at 100 W and 300 W slightly decreases, while the salinity of the hollow salts treated with ultrasonic at 200 W and 400 W is the same as that of the control group, and the salinity of the hollow salt treated with ultrasonic at 500 W significantly increases. This is consistent with the sensory evaluation results, indicating that ultrasonic treatment can improve the salinity of the hollow salt. The reason for the increase in salinity may be that the hollow salt obtained by the 500 W ultrasonic treatment has a small particle size, can contact the tongue more fully, and the salt diffusion speed is fast. As Figure 2 shown in B in it, the richness of the hollow salts treated with ultrasonic at 300 W, 400 W, and 500 W decreases. This may be because the salty taste, as the main taste, masks other tastes, resulting in a decrease in the taste richness. As Figure 2 shown in C in it, since the hollow salt contains succinic acid, some uncross-linked succinic acid will diffuse out, leading to an increase in acidity. As Figure 2 shown in D in it, the umami intensity of the water bath-heated encapsulated salt and the hollow salt after ultrasonic treatment is lower than that of the water bath-heated non-encapsulated salt. This may be because the presence of salt interferes with the umami perception. As Figure 2As shown in E, the sensory evaluation results indicate that compared with the normal 1% NaCl salt solution, ultrasonic treatment at 200 W and 500 W can significantly increase the salinity of the hollow salt, which is related to its higher degree of crosslinking and NaCl embedding amount. Secondly, it is also related to its smaller particle size and uniform distribution, which can be proved by the subsequent scanning electron microscope results and particle size analysis results. It can be analyzed from the sensory evaluation results that only 45.36% - 53.71% of the hollow salt by weight of pure NaCl is required to achieve the salinity of pure NaCl.

[0037] Example 6. Influence of ultrasonic treatment on the particle size distribution and microstructure of hollow salt.

[0038] The particle size and Zeta potential of the hollow salt were measured by a Zetasizer analyzer. The hollow salt prepared in Example 1 was dissolved in water to prepare a 0.1 mg / mL solution, and then ultrasonic treatment was carried out at 300 W for 5 min to make the sample evenly distributed, and then the test was carried out. The microstructure of the hollow salt was observed by scanning electron microscopy at 15 kV and a magnification of 1500×.

[0039] Table 1 Measurement results of the average particle size and potential of hollow salt obtained by different treatment methods

[0040]

[0041] As Figure 3 shown in A, the particle size of the quaternized chitosan raw material is relatively large, 94.96.64 μm, and the surface has abundant amino groups, making the surface of the raw material carry more positive charges and showing a relatively high positive potential. After cross-linking reaction with succinic acid and then spray drying, since the free amino groups on the surface of quaternized chitosan react with the carboxyl groups of succinic acid, the potential of the resulting hollow salt is significantly lower than that of the raw material. The hollow salt prepared by ultrasonic treatment at 200 W has the lowest potential, which is related to its highest degree of crosslinking. The higher the degree of crosslinking, the more stable the network structure formed, and it will embed NaCl more stably and effectively during spray drying, and the free amino groups with positive charges decrease, resulting in a decrease in potential. As Figure 3 shown in B, Figure 3 shown in C, the particle size of the water bath non-salt-loading group decreased to 7.61 μm, while the particle size after salt loading increased to 10.39 μm. This may be because NaCl fills into the core of the sphere, making the particle size increase, and the particle size of the hollow salt obtained by water bath treatment is uneven, with samples exceeding 100 μm. This may be because during the water bath heating process, the matrix material will spontaneously agglomerate together to form large particles due to thermodynamic driving. As Figure 3 shown in D, the influence of 100 W ultrasonic treatment on the particle size of the hollow salt is relatively small, and the particle size is 10.13 μm, while as Figure 3 shown in E, Figure 3 shown in F,Figure 3 In G, Figure 3 As shown in H, the particle size is further reduced by the treatment of 200 - 500 W. The hollow salts prepared by the treatments of 200 W and 500 W have the smallest particle sizes, which are 7.63 μm and 7.27 μm respectively. The smaller particle size is beneficial to the rapid diffusion of the hollow salt. Although the particle size of the hollow salt treated at 300 W is also small, there are particles with a size exceeding 100 μm in the 300 W treatment group, which may be because the ultrasonic wave affects the aggregation distribution of the hollow salt. The reasons for the ultrasonic wave to change the particle size distribution of the hollow salt may be as follows: First, the cavitation effect will be generated during the ultrasonic treatment. The cavitation effect generated by the ultrasonic wave will cause the formation and rapid collapse of bubbles in the liquid. The released local high-temperature and high-pressure environment can break the particle clusters, making their particle sizes smaller and more uniform. Second is the micro-mixing effect exerted by the ultrasonic treatment. The mechanical vibration of the ultrasonic wave will cause violent mixing in the liquid, promoting the uniform dispersion of the materials. This uniform stirring and dispersion effect can prevent the excessive aggregation of particles and form a more consistent particle size distribution. Moreover, the ultrasonic treatment will also produce a shear force effect: the high shear force generated by the ultrasonic wave helps to break large particles or agglomerates, gradually refining the particles, thereby improving the particle size distribution.

[0042] Figure 4 The scanning electron microscope (SEM) images of the hollow salts of different groups are shown as follows. Figure 4 As shown in A, the microscopic morphology of the hollow salt prepared by spray drying after water bath heating treatment is presented. It can be seen that its size is relatively large, the size distribution is uneven, and there are many broken hollow salts. Figure 4 In B, Figure 4 In C, Figure 4 In D, Figure 4 In E, Figure 4 In F, the microscopic morphology of the hollow salts obtained by spray drying after ultrasonic treatment at 100 W - 500 W is shown. The particle sizes of the hollow salts after ultrasonic treatment are all lower than those after water bath heating treatment, and this result is consistent with the particle size analysis result. The size of the hollow salt after 100 W ultrasonic treatment is larger than that of other ultrasonic treatment groups, and its surface is relatively shriveled and not smooth enough. The particle sizes of the hollow salts in the 300 W treatment group show a typical state of uneven size, with some particles being larger, which is consistent with the particle size analysis result because some individual larger particles are captured. The size distributions of the hollow salts in the three groups treated at 200 W, 400 W, and 500 W are relatively uniform and small. The smaller size distribution is beneficial for the dissolution and release of the hollow salt, enabling people to quickly perceive the salty taste, thereby reducing the salt intake.

[0043] The effects of pickling with the hollow salts prepared in Example 7 and Example 1 on air-dried duck meat.

[0044] 1. Effect of hollow salt curing on the pH of air-dried duck meat: The quaternized chitosan-succinic acid-based hollow salt powder encapsulating NaCl prepared in Example 1 was evenly smeared on duck meat at 6 wt%, and vacuum-cured for 24 h. Then, the meat samples were taken out and air-dried at 16 °C and 65% humidity for 3 days. 2 g of air-dried duck meat was added to 18 mL of deionized water, homogenized twice at 8000 r / min for 30 s each time, and then the pH value of each group of duck meat samples was measured with a pH meter. Each group of samples was measured three times repeatedly.

[0045] As Figure 5 Shown in A is the effect of curing with pure NaCl and different groups of hollow salts with the same amount on the pH of air-dried duck. The results show that compared with curing only with NaCl, curing with hollow salts has no significant effect on the pH of air-dried duck. pH can reflect the freshness of meat. The pH of fresh meat is between 5.8 - 6.2. When there are more microorganisms in meat, under the catabolism of these microorganisms, they consume the protein and carbohydrate substances in the meat to produce acidic substances, causing the pH to drop. If the pH drops too much, it will have an adverse effect on the quality of meat products. NaCl has the effect of inhibiting the growth of spoilage microorganisms, and curing with hollow salts does not cause an increase in the degree of spoilage of meat products, indicating that it achieves the effect of reducing salt and preventing spoilage.

[0046] 2. Effect of hollow salt curing on the TVB-N of air-dried duck meat: For the determination of total volatile basic nitrogen (TVB-N), 4 g of air-dried duck meat was mixed with 26 mL of pure water, and homogenized at 10000 rpm / min for 1 min to fully break the meat samples. Then, it was centrifuged at 8000 rpm for 10 min. 10 mL of the supernatant was mixed with 5 mL of magnesium oxide solution (10 g / L), then transferred to a digestion tube, distilled with an automatic Kjeldahl distiller for 5 min, and the distillate was collected. 2 - 3 drops of mixed indicator (methyl red - methylene blue, 0.05 mol / L) were added to it, and then titrated with 0.01 mol / L hydrochloric acid until the color of the distillate changed from colorless to pink, then the titration was terminated.

[0047] As Figure 5 Shown in B is the effect of curing with pure NaCl and different groups of hollow salts with the same amount on the TVB-N of air-dried duck. Compared with curing only with NaCl, curing with hollow salts can reduce the TVB-N value of air-dried duck. Among them, curing with 100W, 300W, 400W, and 500W hollow salts has a better effect on the decomposition of protein by spoilage. This may be because the hollow salt has a special hollow structure and a larger specific surface area than ordinary salt, which enables the hollow salt to penetrate more effectively into the interior of meat products during the curing process, thereby improving the curing efficiency. The uniform distribution of NaCl reduces the degree of protein decomposition by spoilage.

[0048] 3. Effect of hollow salt curing on TBARS of air-dried duck meat: For the determination of the degree of lipid oxidation (TBARS), briefly, accurately weigh 4 g of air-dried duck meat sample, add 36 mL of 10% (v / v) trichloroacetic acid. Homogenize at 8000 rpm / min for 1 min, then centrifuge at 8000 rpm for 10 min. Take 2 mL of the supernatant and mix it with 2 mL of a 0.02 mol / L thiobarbituric acid solution, heat-treat at 90 °C for 40 min, then cool to room temperature, and take 200 μL of the supernatant to measure the absorbance value at 532 nm.

[0049] As Figure 5 Shown in C is the effect of curing with pure NaCl and different groups of hollow salts with the same amount on TBARS of air-dried duck. The results show that curing with hollow salts can reduce the degree of lipid oxidation of air-dried duck meat, and the curing effect of the hollow salt groups of 200W - 500W is better. The structure of the hollow salt may help reduce the contact area between oxidants such as oxygen and lipids in meat products, thus reducing the chance of oxidation reactions; metal ions can promote the formation of free radicals in meat products. For example, iron ions and copper ions can accelerate lipid oxidation, while hollow salts may slow down the lipid oxidation process by reducing the catalytic effects of metal ions such as iron and copper.

[0050] 4. Effect of hollow salt curing on the sensory quality of air-dried duck meat: Recruit 10 professionally trained personnel to conduct sensory evaluation on air-dried duck meat, evaluate the samples from color, texture, flavor, taste, and overall acceptability respectively, using a 10-point scale, and the better the color, texture, flavor, and taste, the higher the score. Each reviewer scores independently without interference, and gargle between tasting each group of samples to prevent cross-contamination of samples from affecting the evaluation results. Table 2 shows the effect of curing with pure NaCl and different groups of hollow salts with the same amount on the sensory quality of air-dried duck.

[0051] Table 2 Effect of hollow salts obtained by different treatments on the sensory quality of air-dried duck

[0052]

[0053] As can be seen from Table 2, curing with hollow salts can improve the sensory quality of dry-cured meat products. In particular, the sensory quality improvement degree is higher when using the hollow salts obtained by ultrasonic pretreatment - spray drying at 400W and 500W. This is related to its smaller particle size, which can improve the perception of saltiness, penetrate more fully into the meat tissue, and improve the flavor uniformity and overall flavor balance. The improvement of color is related to the reduction of the degree of lipid oxidation by hollow salts. When the oxidation degree is low, the color will be more red and bright. The main reason for the improvement of texture is that the polysaccharides contained in the hollow salts penetrate into the meat tissue, increasing the water retention of the meat and making the texture of air-dried duck meat softer.

[0054] The above description is not a limitation of the present invention, nor is the present invention limited to the above examples. Changes, modifications, additions or substitutions made by those of ordinary skill in the art within the scope of the essence of the present invention shall also fall within the protection scope of the present invention.

Claims

1. Application of quaternized chitosan-succinic acid-based hollow salt in air-dried duck meat, characterized in that The preparation method of the quaternized chitosan-succinic acid-based hollow salt comprises the following steps: Mix quaternized chitosan, succinic acid, NaCl and deionized water in a mass ratio of 1:2.36:15:81.64 and stir evenly until dissolved, then treat under ultrasonic conditions of 400-500 W for 20-40 min. After the ultrasonic treatment, perform spray drying to obtain the quaternized chitosan-succinic acid-based hollow salt embedded with NaCl. Using the quaternized chitosan-succinic acid-based hollow salt to marinate air-dried duck meat can significantly reduce the TVB-N and TBARS values of air-dried duck meat and improve the taste of air-dried duck meat.

2. Use of a quaternized chitosan-succinic acid-based hollow salt according to claim 1 in air-dried duck meat, characterized in that: During the spray drying process, set the inlet air temperature of the spray dryer to 140 °C, the fan frequency to 10 rpm, and the solution injection speed to 20 mL / min.

3. Use of a quaternized chitosan-succinic acid-based hollow salt according to claim 1 in air-dried duck meat, characterized in that: Set the water bath temperature to 60 °C during ultrasonic treatment.

4. Use of a quaternized chitosan-succinic acid-based hollow salt according to claim 1 in air-dried duck meat, characterized in that: The ultrasonic power is 400 W or 500 W.

5. Use of a quaternized chitosan-succinic acid-based hollow salt according to claim 1 in air-dried duck meat, characterized in that: The added mass percentage of the hollow salt used for marinating duck meat is 6%, the air-drying time is 3 days, and the air-drying temperature is 16 °C.

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