A method for directional regulation of fish-derived protein soft gel by electrostatic deposition of microcapsules

Abstract

This invention discloses a method for targeted regulation of fish-derived protein soft gel using electrostatic deposition microcapsules, belonging to the field of aquatic product processing technology. Multi-aggregated microcapsules are prepared by compounding pea protein isolate-β-glucan complex aggregates with vegetable oils. Under pH-induced conditions, the multi-aggregated microcapsules are coated with a carboxymethyl chitosan electrostatic deposition layer. These electrostatically deposited microcapsules are then added to surimi raw materials, utilizing their unique thickening properties and gel-forming ability to construct a soft surimi gel system based on fish-derived proteins. The microcapsules enable targeted regulation of the surimi texture, improving the texture of the surimi gel, making the product more delicate and soft, and better suited to the palatability needs of special populations such as the elderly and patients with swallowing difficulties. This invention can enhance the nutritional and health value of surimi soft gels by adding specific nutrients to the microcapsules, thereby enhancing the product's nutritional value and making it an ideal source of nutrition for these populations.

Description

Technical Field

[0001] This invention belongs to the field of aquatic product processing technology, specifically relating to a method for directional regulation of fish-derived protein soft gels using electrostatically deposited microcapsules. Background Technology

[0002] With the increasing global trend of population aging, the proportion of elderly people is constantly rising, and their bodily functions are gradually declining, especially dental health problems (such as loose teeth and tooth loss) and reduced saliva secretion, leading to decreased chewing and digestive abilities, affecting quality of life and potentially causing nutrient malabsorption. Therefore, effective measures are needed to maintain the health of the elderly and improve their quality of life. Currently, medical tube feeding, intravenous nutrition, and food texture modification are three approaches to addressing the diets of the elderly, especially those with swallowing disorders. Among these, food texture modification can not only improve dietary safety and nutrient intake for elderly patients with swallowing disorders but also enhance their eating experience and quality of life. Furthermore, this method is easy to implement in the living environment, has low cost, low risk, and high flexibility, and can be personalized according to the patient's swallowing ability and preferences. Therefore, food texture modification is considered an effective means to improve the quality of life and ensure swallowing safety for elderly people with swallowing disorders.

[0003] Marine foods, as a high-quality "food," provide nearly 20% of the animal protein consumed by humans. Aquatic proteins have advantages such as high bioavailability and high digestibility, making them a superior protein source for special diets. Surimi products are popular among consumers due to their rich content of high-quality aquatic protein and high viscoelasticity. However, surimi products with high gel strength are not suitable for elderly people with weak chewing abilities. With increasing health awareness, existing surimi products cannot meet consumers' higher demands for nutritional value, especially for the elderly and those with swallowing difficulties, requiring customized nutritional solutions. Therefore, the rational application of nutritional supplements, the exploration of appropriate texture control methods, and the development of high-quality functional gel foods based on easy swallowing are becoming increasingly important.

[0004] Currently, existing technologies primarily utilize physical methods (such as homogenization, freezing and thawing) and chemical methods (such as adding proteases, phosphates, and polysaccharides) to control the texture of surimi. However, these technologies suffer from increased energy consumption and limitations in dosage during actual production, making it difficult to simultaneously improve product texture and enhance nutrition. Therefore, overcoming the problems of existing surimi products' high hardness, elasticity, and chewiness, making them unsuitable for people with swallowing difficulties, and providing a surimi soft gel product suitable for industrial production, high in protein and nutrition, and easy to eat, is a technical challenge that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0005] [Technical Issues]

[0006] The technical problem to be solved by this invention is that existing surimi products are hard, elastic, and chewy, making them unsuitable for special groups such as those with difficulty swallowing.

[0007] [Technical Solution]

[0008] To address the aforementioned problems, this invention provides a method for directionally regulating the formation of soft fish protein gels using electrostatically deposited microcapsules. This invention prepares complex aggregate microcapsules by compounding pea protein isolate-β-glucan complex aggregates with vegetable oils. Using electrostatic attraction under pH-induced conditions, the complex aggregate microcapsules are coated with a carboxymethyl chitosan electrostatic deposition layer. These electrostatically deposited microcapsules are then added to surimi raw materials, utilizing their unique thickening properties and gel-forming ability to construct a soft surimi gel system based on fish protein. This method improves the texture properties of surimi gels by directionally regulating their gelation behavior. This method effectively reduces the hardness and chewiness of surimi gels while preparing easily edible soft surimi gels. Furthermore, the unique encapsulation properties of microcapsules can be used to load specific nutrients, enhancing the nutritional properties of surimi gels and further improving the nutritional value and functionality of surimi products.

[0009] This invention provides a method for preparing electrostatically deposited microcapsules, comprising the following steps:

[0010] (1) Mix pea protein isolate aqueous solution with β-glucan aqueous solution to form wall material solution, and at the same time dissolve nutrients into oil to obtain oil phase;

[0011] (2) Mix the wall material solution with the oil phase and emulsify it in a high-speed homogenizer. Then, while stirring, slowly add acetic acid solution to adjust the pH value to 3.5-4.5. After reacting for 25-35 minutes, add carboxymethyl chitosan aqueous solution and add sodium hydroxide solution to adjust the pH value to 5.0-6.0.

[0012] (3) Add glutamine transferase and stir the reaction at 20-25℃ to obtain a microcapsule suspension. Let it stand to separate into layers, remove the supernatant and filter to obtain electrostatically deposited microcapsules.

[0013] In one embodiment of the present invention, in step (1), the concentration of the wall material solution is 0.5 to 2 wt%, preferably 1 wt%.

[0014] In one embodiment of the present invention, in step (1), the concentration of the pea protein isolate aqueous solution is 0.5-2 wt%, preferably 1 wt%.

[0015] In one embodiment of the present invention, in step (1), the concentration of the β-glucan aqueous solution is 0.5 to 2 wt%, preferably 1 wt%.

[0016] In one embodiment of the present invention, in step (1), the wall material solution is hydrated at 0 to 5°C for 6 to 10 hours.

[0017] In one embodiment of the present invention, in step (1), the oil is at least one of perilla seed oil, soybean oil, walnut oil, flaxseed oil, rapeseed oil, peanut oil, and sunflower seed oil, preferably perilla seed oil.

[0018] In one embodiment of the present invention, in step (1), the nutrient is a fat-soluble nutrient, preferably vitamin D; the concentration of the nutrient in the oil phase is 0.5 to 1.5 mg / mL.

[0019] In one embodiment of the present invention, in step (2), the mass ratio of pea protein isolate, β-glucan, and carboxymethyl chitosan is 1 to 4:1:1, preferably 1:1:1.

[0020] In one embodiment of the present invention, in step (2), the mass ratio of the wall material solution to the oil phase is 2 to 4:1.

[0021] In one embodiment of the present invention, in step (2), the emulsification conditions are 8000-10000 rpm for 2-3 min, preferably 8000 rpm for 3 min.

[0022] In one embodiment of the present invention, in step (2), the concentrations of the acetic acid solution and the sodium hydroxide solution are 0.1 to 10 wt%, preferably 1 wt%.

[0023] In one embodiment of the present invention, in step (3), the amount of glutamine transferase added is 1 / 4 of the amount of pea protein isolate, and the enzyme activity of glutamine transferase is 100 U / g.

[0024] This invention provides electrostatically deposited microcapsules prepared by the method described above.

[0025] This invention provides the application of the electrostatically deposited microcapsules described above in the food industry.

[0026] This invention provides the application of the electrostatically deposited microcapsules described above in surimi products.

[0027] This invention provides the application of the electrostatically deposited microcapsules described above in regulating the textural properties of surimi products.

[0028] This invention provides a fish paste soft gel containing electrostatically deposited microcapsules, the preparation method of which includes the following steps:

[0029] After thawing the frozen fish paste, put it into a food processor and grind it. Add salt and grind it, then add water and continue grinding. Then add the electrostatically deposited microcapsules mentioned above and grind it for the last time. The fish paste is then gelled by a two-stage heating method. After heating is complete, it is placed in ice water to cool. After cooling, the soft fish paste gel is obtained.

[0030] In one embodiment of the present invention, the fish paste is one or more of cod fish paste, grass carp fish paste, silver carp fish paste, golden threadfin bream fish paste, tuna fish paste and ribbonfish fish paste, preferably cod fish paste.

[0031] In one embodiment of the present invention, the thawing is performed by placing the container at 0 to 4°C for 10 to 14 hours.

[0032] In one embodiment of the present invention, the pounding process is carried out in an ice box to prevent the surimi from overheating.

[0033] In one embodiment of the present invention, the crushing process lasts for 2 to 4 minutes, at a speed of 2000 to 3000 rpm, with a time interval of 20 to 30 seconds.

[0034] In one embodiment of the present invention, the amount of electrostatically deposited microcapsules added is 5 to 30% of the mass of the fish paste.

[0035] In one embodiment of the present invention, the amount of salt added is 2-3% of the mass of the fish paste, preferably 2%.

[0036] In one embodiment of the present invention, the water is one or any combination of mineral water, tap water, deionized water, and distilled water, preferably distilled water.

[0037] In one embodiment of the present invention, the two-stage heating is as follows: first heating at 40°C for 20 to 30 minutes, and then immediately transferring to 90°C for 30 minutes.

[0038] [Beneficial Effects]

[0039] (1) The vitamin D microcapsules prepared by the composite coagulation method effectively solved the problem that vitamin D is easily affected by factors such as temperature during food processing. The microcapsules not only improved the encapsulation rate of vitamin D, achieving an encapsulation efficiency of 92% and a loading efficiency of 70%, but also significantly enhanced its thermal stability and ultraviolet stability, providing a technical basis for the widespread application of vitamin D in the food industry.

[0040] (2) In this invention, the complex coagulated microcapsules are coated with a carboxymethyl chitosan electrostatic deposition layer. The electrostatic deposition layer can enhance the structural stability of the microcapsules and prevent the microcapsules from breaking or leaking during the processing.

[0041] (3) Cod protein soft gel prepared using microencapsulation technology meets the standards for easy-to-eat foods. This gel is particularly suitable for the elderly and people with difficulty swallowing, effectively solving their problems of nutrient deficiency and special taste requirements, and providing an ideal form of nutritional supplementation.

[0042] (4) The application of microencapsulation technology in food not only improves the stability and sustainable release of active ingredients, but also, through its unique thickening properties and gel-forming ability, constructs soft, easy-to-eat gel systems suitable for special populations such as the elderly. This research opens up new avenues for the application of microcapsules in the elderly food market and other functional food fields, meeting people's higher demands for health and nutrition. Attached Figure Description

[0043] Figure 1 The images show optical micrographs (A), inverted fluorescence micrographs (B), inverted fluorescence micrographs (C), and cold field scanning electron micrographs (D) of the microcapsules in Examples 1-4.

[0044] Figure 2 The UV stability diagram (A), differential scanning calorimetry (B), and thermogravimetric analysis (C) of the microcapsules in Examples 1-4 are shown.

[0045] Figure 3 This is an optical microscope image of Comparative Example 1;

[0046] Figure 4 Example 5 illustrates the effect of different pH values ​​on the turbidity (A) and speciation (B) of complex aggregates;

[0047] Figure 5 Example 6 illustrates the effect of different wall material blending ratios on the turbidity (A, B) and morphology (C) of complex aggregates.

[0048] Figure 6 Example 7 illustrates the effect of different wall material blending ratios on the circular dichroism (A) and secondary structure (B) of the composite aggregate;

[0049] Figure 7 Example 8 illustrates the effect of different wall material compounding ratios on the encapsulation efficiency and loading rate of vitamin D microcapsules;

[0050] Figure 8 IDSSI test results for the soft gels in Comparative Example 2 and Examples 9-14;

[0051] Figure 9 Gel strength graphs of the soft gels in Comparative Example 2 and Examples 9-14;

[0052] Figure 10The colorimetric diagram (A), whiteness diagram (B), and appearance diagram (C) of the soft gels prepared in Comparative Examples 2 and Examples 9-14 are shown. Detailed Implementation

[0053] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0054] Source of raw materials

[0055] Pea protein isolate (95% purity) was purchased from Beijing Baoxidi Co., Ltd.; oat-β-glucan (purity >90%) and carboxymethyl chitosan (purity 90%) were purchased from Dalian Bonuo Co., Ltd.; vitamin D (purity 98%) was purchased from Shanghai Aladdin Reagent Co., Ltd.; perilla seed oil (91.6% unsaturated fatty acid content, 15.4% oleic acid, 16% linoleic acid, and 60% linolenic acid) was purchased from Hebei Shanyifang Co., Ltd.; cod surimi was purchased from Qingdao Tengbenwei Co., Ltd.; and glutamine transferase was purchased from Beijing Solarbio Technology Co., Ltd., with an enzyme activity of 100 U / g.

[0056] Test methods

[0057] 1. Microcapsule optical microscopy testing method: Place the microcapsule suspension on a glass slide and observe the microcapsules using an optical microscope at a magnification of 200x.

[0058] 2. Microcapsule lipid-protein distribution test method: Take 200 μL of microcapsule sample, and stain the oil phase and protein with 20 μL of Nile red-acetone solution (0.1%, w / v, g / mL) and 20 μL of FITC-dimethyl sulfoxide solution (0.5%, w / v, g / mL). Shake the sample in the dark for 20 min, and drop it onto a glass slide with a dropper. After equilibration for 1 min, observe the embedding of the core material using a fluorescence inverted microscope.

[0059] 3. Microcapsule bilayer structure test method: Disperse 1g of microcapsules in 10mL of distilled water, stain the protein and polysaccharide with 20μL of acetone-Nile blue solution (0.1%, w / v, g / mL) and 20μL of fluorescent white dye, shake the sample in the dark for 20min, drop it onto a glass slide with a dropper, and collect the image using a fluorescence inverted microscope after equilibration for 1min.

[0060] 4. Microcapsule cold field scanning electron microscopy test method: The microstructure of the microcapsules is observed using a scanning electron microscope. The wet microcapsules are placed on the sample stage and observed under a voltage of 10 kV at a magnification of 1 k.

[0061] 5. Analysis method for the UV stability of microcapsules: 0.1 g of microcapsules were irradiated with a UV lamp (15 W) at a distance of 10 cm for 10 min, 20 min, 40 min, and 60 min, respectively, and then dispersed in 30 mL of n-hexane. The microcapsules were centrifuged at 3000 × g for 10 min to obtain free VD3. The absorbance of the supernatant was recorded at 264 nm using a UV-Vis spectrophotometer.

[0062] 6. Analytical methods for microcapsule thermogravimetric analysis and differential scanning calorimetry: The thermal stability of the microcapsules was tested using a thermogravimetric analyzer and a differential scanning calorimeter. 1 mg of vitamin D and the microcapsule sample were weighed and placed in a crucible, compressed, and sealed. These samples were then analyzed in TGA and DSC reaction cells, respectively, with a blank crucible serving as a control. Thermogravimetric parameters: heating rate 20℃ / min, nitrogen flow rate 60 mL / min, heating range 20–600℃; Differential scanning calorimetry parameters: heating rate 10℃ / min, nitrogen flow rate 30 mL / min, heating range 20–90℃.

[0063] 7. Soft Gel TPA Test Method: The textural properties of the samples were evaluated in the full texture analysis mode of the physical property tester. Test conditions: P / 100 probe, speed of 1 mm / s before, during and after the test, two consecutive compressions were performed on each sample, compression ratio of 30%, trigger force of 5 g.

[0064] 8. Soft Gels IDDSI Testing Method: Soft gels are classified using the fork pressure test, a testing method developed by the International Dysphagia Diet Standardization Initiative (IDDSI). Actual testing using a fork or spoon will classify the food as a transitional food at IDDSI levels 5-7. When the food (approximately 1.5cm x 1.5cm) is pressed down with the bottom of a fork, it will flatten (the thumb and forefinger nails will turn white when pressure is applied), and the food will not spring back to its original shape after the fork is removed.

[0065] 9. Soft Gel Strength Test Method: Cut the matured sample into cylinders with a diameter of 25 mm and a height of 30 mm. Measure the gel strength of the sample using the gel strength mode of a physical property testing instrument. Test conditions: P / 5S probe, pre-test and test speed 1 mm / s, post-test speed 10 mm / s, puncture ratio 50%, trigger force 5 g. The gel strength calculation formula is as follows:

[0066] Gel strength (g×mm) = breaking force (g) × breaking distance (mm).

[0067] 10. Soft gel colorimetric test method: Use a colorimeter to measure whiteness. After the temperature has equilibrated to room temperature, measure and record the color values ​​of L* (brightness), a* (red and blue), and b* (yellow and green). All measurements are taken at three random locations on the surface of each sample, and the average value is used to indicate the color change of the sample.

[0068]

[0069] 11. Circular dichroism spectroscopy analysis

[0070] The concentration of the complex aggregate was adjusted to 0.01 mg / mL, and 450 μL of the complex aggregate solution was accurately measured and added to a cuvette. The scanning wavelength range was set to 190–240 nm, the resolution to 0.2 nm, the scanning speed to 50 nm / min, and the bandwidth to 1 nm. The samples were detected at room temperature (25 °C) under nitrogen atmosphere. Circular dichroism was expressed as the average residue ellipticity value [θ], in deg·cm. 2 / dmol.

[0071] 12. Methods for determining microcapsule encapsulation efficiency and loading rate

[0072] Disperse 0.1 g of microcapsule sample in 30 mL of n-hexane and centrifuge at 3000 × g for 5 min to separate unencapsulated VD3. Record the absorbance of the supernatant at 264 nm using a UV / Vis spectrophotometer, and denote the concentration of unencapsulated VD3 as C1. Then, add another 30 mL of n-hexane to the precipitate and use a thermal ultrasonic cleaner to disrupt the microcapsules for 30 min. The ultrasonic power is 1200 W, the frequency is 24 Hz, and the heating temperature is set to 100 °C. After disruption, centrifuge at 3000 × g for 5 min and record the absorbance of the supernatant at 264 nm using a UV / Vis spectrophotometer, denoteing the concentration of encapsulated VD3 as C2.

[0073] The formulas for calculating EE (encapsulation efficiency) and LE (loading rate) are as follows, where WT is the total mass of the microcapsules.

[0074]

[0075] Example 1

[0076] A method for preparing electrostatically deposited microcapsules includes the following steps:

[0077] (1) Prepare 1 wt% pea protein isolate (PPI), oat-β-glucan aqueous solution (β-OG) and carboxymethyl chitosan aqueous solution (CMCS) respectively, and stir with a magnetic stirrer at 300 rpm for 6 h, with a hydration temperature of 0-5℃, until complete hydration;

[0078] (2) PPI and β-OG were mixed in a ratio of 1:1 (w / w) to form a wall material solution, and vitamin D was dissolved in perilla seed oil to obtain an oil phase (1 mg / mL);

[0079] (3) Mix the wall material solution and the oil phase at a ratio of 2:1 (w / w), emulsify at 10,000 rpm for 3 min using a high-speed homogenizer, stopping every 30 seconds, then stir at 350 rpm, slowly add acetic acid solution (1 wt%), adjust the pH to 4.0 to carry out the composite coagulation reaction, and continue stirring for 30 min after the reaction is completed.

[0080] (4) Slowly add CMCS to make the mass ratio of pea protein isolate, β-glucan and carboxymethyl chitosan 1:1:1, and adjust the pH of the system to 5.0 with sodium hydroxide solution (1wt%), and continue stirring for 30 min;

[0081] (5) Finally, 0.25 g / g pea protein isolate TG enzyme was added as a cross-linking agent, and the mixture was stirred at 300 rpm for 4 h at room temperature to obtain a double-layer microcapsule suspension.

[0082] Example 2

[0083] Adjust the ratio of PPI to β-OG in step (2) of Example 1 to 2:1; keep the other steps the same as in Example 1.

[0084] Example 3

[0085] Adjust the ratio of PPI to β-OG in step (2) of Example 1 to 3:1; keep the other steps the same as in Example 1.

[0086] Example 4

[0087] Adjust the ratio of PPI to β-OG in step (2) of Example 1 to 4:1; keep the other steps the same as in Example 1.

[0088] The electrostatically deposited microcapsules prepared in Examples 1-4 were subjected to performance testing, and the test results are as follows:

[0089] Figure 1 The following are microscopic images of the microcapsules: (A) Optical microscope image, (B) Inverted fluorescence microscope image, (C) Double-layer structure fluorescence microscope image, (D) Scanning electron microscope image. Figure 1 As shown in (A), at 200x magnification, all microcapsules exhibited a well-defined spherical structure, and the internal structure of all microcapsules was visible, confirming them as spherical multinucleated microcapsules. Furthermore, with increasing PPI ratio, the number of microcapsules within the field of view gradually increased, and the diameter of some microcapsules increased. Figure 1(B) The oil phase and PPI complex were stained with Nile Red and FITC, respectively, to observe the embedding of microcapsules in the oil phase. It can be seen that Examples 1-4 exhibited good spherical structures under a fluorescence inverted microscope. The distribution of protein (green) and lipid (red) indicates that the complex formed a relatively complete wall material, effectively encapsulating the core material. With increasing protein content, the microcapsules showed large-area aggregation and poor dispersibility. Furthermore, to further demonstrate the bilayer structure formed by the electrostatic interaction between CMCS and PPI / β-OG, CMCS and PPI / β-OG were stained simultaneously. Figure 1 (C) PPI was fluorescently labeled with Nile Blue, appearing red at an exciter wavelength of 633 nm; CMCS was fluorescently labeled with a fluorescent whitening agent, appearing green at an exciter wavelength of 402 nm. The figure shows that PPI and CMCS completely overlap. Under the influence of pH, CMCS formed a relatively complete wall material, effectively coating the monolayer microcapsules, further confirming the successful preparation of bilayer microcapsules. Furthermore, we can see that the CMCS shell surface formed in Example 1 is smooth, dense, and relatively uniform, while the CMCS shell surface formed in Examples 2-4 shows pores, with some areas showing uneven coating. This phenomenon may be due to raising the pH of the microcapsule suspension to 5.0 during CMCS coating, reducing the positive charge of the protein and preventing some CMCS from binding well to PPI / β-OG. Figure 1 (D) Further observation of the microcapsule ultrastructure using SEM. At 1000× magnification, the microcapsules exhibited a well-defined spherical structure with a slightly concave surface but no cracks. Furthermore, a network structure was observed between the spheres, maintaining a safe distance between the microcapsules and ensuring their stability. In Example 1, the microcapsules were relatively uniform in size and had a smooth surface. As the PPI ratio increased, the number of microcapsules increased, and the surface deposits also increased. In Examples 2–4, due to the imbalance of charge ratios in the solution, a large number of CMCSs adhered to the surface of the microcapsules and were superimposed, resulting in an increase in the overall size of the microcapsules; at this point, the network became disordered.

[0090] Figure 2 The images show the UV stability (A), differential scanning calorimetry (B), and thermogravimetric analysis (C) of the microcapsules in Examples 1-4. Vitamin D is a photosensitive substance, and it is prone to photo-oxidation or isomerization reactions when exposed to ultraviolet light, leading to degradation and inactivation of the active ingredients. To clarify the UV blocking efficiency of the microcapsules under different compounding ratios, the effect of the wall material ratio on the UV stability of vitamin D microcapsules was further investigated. The results are as follows: Figure 2As shown in (A), the protective effect of the microcapsules on vitamin D gradually diminishes with prolonged irradiation time. In Example 1, when the wall material ratio was 1:1:1, the EE of vitamin D in the microcapsules gradually decreased to 48.54% with prolonged UV irradiation time, but remained higher than in other groups. At 0 min, the vitamin D retention rate in the microcapsules gradually decreased with increasing PPI. Furthermore, during irradiation, the microcapsules ruptured with increasing PPI, exposing vitamin D and leading to a decrease in retention rate. After 20 min of irradiation, microcapsule rupture increased, and the vitamin D retention rate rapidly decreased. In summary, when the wall material ratio in Example 1 was 1:1:1, the composite agglomerated microcapsules exhibited the strongest UV resistance, the best vitamin D retention rate, and the best effect in delaying structural isomerization. In some food processing processes, heat treatment methods such as steaming, boiling, baking, and high-temperature sterilization can cause loss of active substances, making it essential to improve the thermal stability of active substances. To assess the thermal stability of the microcapsules, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to evaluate the thermal stability of the vitamin D microcapsules. DSC analysis measures the relationship between the heat flux difference between the microcapsules and vitamin D and temperature to assess stability. Figure 2 (B) shows the DSC curves of the microcapsules and vitamin D. As can be seen from the figure, the original vitamin D exhibits a large absorption peak near 65.29℃, which may be due to the thermal degradation of vitamin D, indicating that 65.29℃ is the melting temperature of vitamin D. The microcapsule curve, however, shows no absorption peak, indicating that the microcapsules have improved thermal stability and provide better protection for vitamin D. Thermogravimetric analysis can reflect the relationship between sample mass and temperature. Figure 2 (C) shows the TGA curve of the vitamin D microcapsules. As shown in the figure, there was a mass loss of the original vitamin D at 240.00℃. The degradation of the vitamin D-loaded complex aggregated microcapsules mainly occurred in two stages. The first stage was the heating stage from 20 to 124.81℃, during which the mass of the microcapsules decreased, mainly due to the loss of moisture in the sample. Before the temperature reached 342.34℃, the mass of the vitamin D-loaded complex aggregated microcapsules changed only slightly. Subsequently, as the temperature increased, the stability of the microcapsules deteriorated, and the mass decreased sharply. When the temperature reached 476.95℃, the microcapsules completely ruptured. The wall material ratio also had a significant impact on the thermal stability of the microcapsules. Compared with Example 4, the microcapsules prepared under the wall material compounding ratios of Examples 1-3 showed lower heat loss rates and better thermal stability as the temperature gradually increased.

[0091] Comparative Example 1

[0092] The preparation method is the same as in Example 1, except that carboxymethyl chitosan is omitted, that is, step (4) in Example 1 is omitted.

[0093] Microscopic observation was performed on Example 1, and the test results are as follows:

[0094] Figure 3 The image shown is an optical microscope image of Comparative Example 1. As can be seen from the image, the microcapsules of Comparative Example 1 exhibit a well-developed spherical structure with rounded edges, indicating that the complex aggregate formulation can form microcapsules. The outer walls of the microcapsules are relatively thin, and their sizes vary considerably, which may be due to uneven dispersion during the emulsification process. Furthermore, the image shows some obvious oil phase substances in the solution, indicating that the oil phase was not completely encapsulated. These oil phase substances may be due to a thin, discontinuous, or broken encapsulation film layer, or they may have ruptured during the preparation process. The aggregation of some oil phase substances further indicates poor encapsulation performance.

[0095] Example 5

[0096] Investigating the effects of different pH values ​​on the turbidity and speciation of complex aggregates

[0097] The turbidity and morphology of the complex aggregates affect the encapsulation efficiency, stability, and release performance of microcapsules. Therefore, the turbidity and morphology of the complex aggregates must meet the standards of uniformity, stability, and controllability. Furthermore, the optimal state of the complex aggregates during microcapsule encapsulation is a liquid phase with good water solubility.

[0098] A 0.1% binary complex condensate solution with a PPI:β-OG ratio of 1:1 was prepared. The pH of the mixture was adjusted to 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, and 6.5, respectively, using glacial acetic acid (10%, v / v) and NaOH (1 mol / L). The samples were visualized using a photographic box, and the turbidity of different complex condensates was measured using a UV-Vis spectrophotometer.

[0099] As the pH of the solution changes, the intensity of the complex coagulation reaction also changes, exhibiting different colloidal states. Macroscopically, this manifests as pH-driven aggregation of substances to form complex coagulates, making the solution more turbid. Within the pH range of 2.5–6.5, the turbidity of binary complex coagulates initially increases and then decreases with increasing pH. In the low pH range (2.5–3.5), the strongly acidic environment causes both PPI and OG to be in a highly protonated state, with intermolecular electrostatic repulsion dominating, making it difficult to form a stable complex coagulated phase. In the pH range of 4.0–5.0, PPI and OG form a dense network structure through electrostatic interaction, resulting in a sharp increase in turbidity, with the highest turbidity value at pH=4. In the high pH range (5.5–6.5), the increased deprotonation of OG leads to a reversal of the surface charge of the complex, reinvigorating electrostatic repulsion and causing dissociation or recombination of the complex particles. When encapsulating substances, the better complex coagulates are those with better water solubility. Figure 4As shown, visual analysis of the samples revealed that the solutions were relatively turbid but homogeneous at pH values ​​of 3.5, 4, and 4.5, with only a small amount of precipitation. The solution system was most homogeneous at pH value of 4, possibly due to the enhanced protonation of the amino side group of PPI, which triggered charge attraction with the negatively charged carboxyl group of β-OG. Therefore, pH value of 4 was selected as the pH for the reaction.

[0100] Example 6

[0101] Investigating the effects of different wall material blending ratios on the turbidity and morphology of composite aggregates

[0102] A 0.1% binary complex condensate solution was prepared with PPI:β-OG and β-OG:PPI ratios of 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, and 10.0, respectively. The pH of the mixture was adjusted to 4.0 using glacial acetic acid (10%, v / v) and NaOH (1 mol / L). The samples were visualized using a photographic box, and the turbidity of different complex condensates was measured using a UV-Vis spectrophotometer. The results are as follows: Figure 5 As shown. From Figure 5 As shown in (A), as the amount of PPI added gradually increases, the number of positively charged groups in the composite coagulant solution increases, and the turbidity value also increases accordingly. However, as the interaction between charges gradually reaches equilibrium, the overall change in turbidity is relatively small. Figure 5 (B) indicates that the turbidity of the solution gradually decreases with increasing polysaccharide content. When the ratio of PPI to polysaccharide is 1:1, the turbidity is highest and most uniformly distributed, indicating the most reasonable charge matching and a more stable complex structure. However, when polysaccharide is in excess, its steric hindrance effect on the molecular chains is enhanced, leading to a decrease in the efficiency of complex formation and a further decrease in turbidity. Complex coagulation is a process in which positively and negatively charged groups react through ionic interactions; the optimal ratio for complex coagulation is when the solution is electrically neutral.

[0103] Example 7

[0104] Investigating the effect of wall material blending ratio on the secondary structure of composite aggregates

[0105] Circular dichroism (CD) spectroscopy is a spectroscopic method that uses the differential absorption of left- and right-circularly polarized light by chromophores to deduce structural information about protein conformations. During the formation of complex condensates, the internal structure of protein polymers (PPIs) also changes. Figure 6As shown in (A), PPI exhibits a negative peak at 200 nm, attributed to the presence of secondary structures containing β-sheets and β-turns, indicating a high prevalence of β-configurations in the PPI structure. With the addition of OG, the peak value at 200 nm in the binary complex condensate gradually decreases. This may be due to the reduction of irregular coil structures, with more being converted to other configurations. In the ternary complex condensate with a PPI:OG:CMCS ratio of 1:1:1, a lower peak appears at 209 nm, and this peak gradually decreases and red-shifts with increasing PPI content, indicating that the addition of CMCS alters the conformation of PPI, gradually transforming the protein molecule from a disordered, irregular morphology to an ordered helical state. Further calculations using Young's equations were performed on the secondary structure information of PPI and the complex condensate, with results as follows: Figure 6 As shown in (B), the β-type of PPI accounts for 45%, and β-sheet accounts for 25%, indicating that the β configuration dominates the changes in the CD curve of PPI. The β-turn and random coil contents of binary complex aggregates decreased by 3.37% and 3.77%, respectively, which were converted into an increase in β-sheet (31.93%), indicating that the addition of OG gradually led to a more stable structure of PPI. After the addition of CMCS, the α-helix content of ternary complex aggregates increased, while the β-sheet and random coil contents decreased; the α-helix content in the 1:1:1 ratio was 14.43%, which is 2.38 times that of the binary complex aggregates, and the α-helix content gradually increased with the increase of the ratio, indicating that the ternary complex aggregates have a more stable and ordered structure.

[0106] Example 8

[0107] Effect of wall material compounding ratio on the encapsulation efficiency and loading rate of vitamin D microcapsules

[0108] To clarify the protective efficiency of the wall material for the active ingredients and the actual vitamin D loading capacity under different compounding ratios, the effect of the wall material ratio on the EE and LC of vitamin D microcapsules was further investigated. A series of vitamin D3 standard solutions (concentrations of 0.1, 10, 20, 50, 100, 150, 200, 250, and 300 μg / mL) were prepared using a gradient dilution method. Absorbance was measured at the characteristic absorption wavelength of 264 nm using a UV-Vis spectrophotometer, with each concentration measured in triplicate. A standard curve was constructed by linear fitting of concentration and absorbance, and the results are shown below. Figure 7 As shown in (A), its regression equation is y = 0.0048x + 0.0101, R0 2 =0.9992. This indicates a high linear correlation between the standard concentration and the absorbance value. For example... Figure 7As shown in (B), the EE of the complex aggregated microcapsules gradually decreased with increasing PPI in the wall material, but the total concentration of biopolymers remained at 1%. Comparing microcapsules prepared with different wall material ratios, it was found that the complex aggregated microcapsules had the highest EE for vitamin D at a ratio of 1:1:1, reaching 92.52%. This result indicates that the microcapsules with this wall material ratio can effectively encapsulate vitamin D. When the PPI content increased, the emulsifying properties and stability of the emulsion were poor due to the decrease in polysaccharide content in the solution, resulting in most of the vitamin being exposed in the free solution and leading to a lower encapsulation rate. LC represents the amount of vitamin D that can be carried in a fixed amount (0.01 g) of microcapsules, which depends on the concentration of the bioactive compounds used. As shown in the figure, the microcapsules had the highest LC (reaching 74.52%) when the wall material ratio was 2:1:1, indicating that this wall material could carry the highest amount of vitamin D. When the wall material ratio is 3:1:1 and 1:1:1, the LC decreases slightly but remains at a high level, with loading rates of 71.46% and 70.41%, respectively. When the wall material ratio is 4:1:1, the microcapsules have the lowest LC with a loading rate of 52.60%, indicating that the ratio of interacting charges in the solution is uneven under this wall material ratio, resulting in a relatively small volume of macromolecules that can react in the solution.

[0109] Example 9

[0110] A method for preparing a fish paste soft gel containing electrostatically deposited microcapsules includes the following steps:

[0111] (1) Thaw the frozen cod paste at 0-4℃ for 10-14 hours, put the paste into a food processor and grind for 3 minutes, add 2% of the mass of the paste with salt and grind for 3 minutes, then add the same mass of the paste with water and grind for 3 minutes at a speed of 2500 rpm and a time interval of 20 seconds.

[0112] (2) Add 5% of the fish paste by weight of microcapsules (Example 1) to the fish paste and continue to pound for 3 minutes. The fish paste is heated using a two-stage heating method, that is, heated at 40°C for 30 minutes, and then immediately transferred to 90°C for 30 minutes. After heating, the resulting fish paste gel is placed in ice water to cool for 30 minutes and stored at 4°C until the next step of analysis is performed.

[0113] Example 10

[0114] In step (2) of Example 9, 10% (w / w) of the microcapsules were added to the fish paste; the other steps remained the same as in Example 9.

[0115] Example 11

[0116] In step (2) of Example 9, 15% (w / w) of the microcapsules were added to the fish paste; the other steps remained the same as in Example 9.

[0117] Example 12

[0118] In step (2) of Example 9, 20% (w / w) of the microcapsules were added to the fish paste; the other steps remained the same as in Example 9.

[0119] Example 13

[0120] In step (2) of Example 9, 25% (w / w) of the microcapsules were added to the fish paste; the other steps remained the same as in Example 9.

[0121] Example 14

[0122] In step (2) of Example 9, 30% (w / w) of the microcapsules were added to the fish paste; the other steps remained the same as in Example 9.

[0123] Comparative Example 2

[0124] The amount of water added in step (1) of Example 9 was adjusted to 0%, and the microcapsules were added to the fish paste at 0% (w / w) in step (2); the other steps were the same as in Example 9.

[0125] The soft gels prepared in Examples 9-14 and Comparative Example 2 were subjected to performance tests, and the test results are as follows:

[0126] Table 1 shows the total texture properties (TPA) of the soft gels in Examples 9-14 and Comparative Example 2. As can be seen from the table, the addition of microcapsules significantly altered the hardness, chewiness, and resilience of the cod protein gel. Comparative Example 2 exhibited higher hardness and chewiness values ​​(2767.08 g and 1653.56 g, respectively), indicating a firmer gel texture. With increasing microcapsule addition, the hardness and chewiness of the gel significantly decreased, moving towards a softer texture. Compared to Comparative Example 2, the elasticity values ​​of Examples 9-14 showed no significant change, indicating that the addition of water and microcapsules did not reduce gel elasticity. Example 13 exhibited the lowest hardness and chewiness, demonstrating that the amount of microcapsules added in this example resulted in an optimally soft texture suitable for chewing.

[0127] Table 1. Texture properties of the soft gels in Examples 9-14 and Comparative Example 2

[0128]

[0129] The IDDSI framework provides internationally recognized assessment standards and testing methods for dietary design for patients with dysphagia. Through methods such as fork pressure tests, fork separation experiments, and spoon pressure tests, the suitability of gels as dysphagia-friendly foods can be scientifically evaluated and verified according to the IDDSI classification system, ensuring that the food meets IDDSI grade requirements. Figure 8 According to gel mapping analysis within the IDDSI framework, Comparative Example 2 (pure cod surimi) had a firm texture and was extremely difficult to press during the fork / spoon pressure test. A large area (approximately 1 / 3) of the thumb turned white, and the sample immediately returned to its original shape after being pressed, thus not belonging to any IDDSI category. With the increase in the proportion of microcapsules added (Examples 9-14), the texture of the surimi gradually softened, and the samples could be easily separated with a fork. In the fork and spoon pressure test, pressing the fork and spoon with the thumb resulted in slight whitening of the thumb tip. After pressing with the front of the fork and spoon, the sample's shape changed and broke, and it failed to return to its original shape after the fork / spoon was removed, still showing obvious dents and cracks. This change indicates that soft gels can belong to the "potential transitional food" category within the IDDSI framework. Soft gels can be classified as level 6, indicating that the gel can be easily broken down into a safe size through chewing and tongue pressure, reducing the risk of choking. In conclusion, the addition of microcapsules can effectively adjust the texture of fish paste to meet the needs of patients with dysphagia, providing an important practical reference for dietary design for patients with dysphagia.

[0130] Figure 9The graphs show the gel strength of the soft gels in Examples 9-14 and Comparative Example 2. As can be seen from the graphs, the gel strength initially increases and then decreases with increasing microcapsule content, trending towards a softer texture. Comparative Example 2 exhibits a higher gel strength of 1788.32 g·mm. Compared to Comparative Example 2, Examples 9-14 all show a significant decreasing trend. Between Example 9 (5% microcapsule addition) and Example 13 (25% microcapsule addition), the gel strength increases with increasing microcapsule content, indicating that an appropriate amount of microcapsules can effectively enhance the gel structure of the surimi. The wall material components in the microcapsules may interact with the proteins in the surimi during heating, promoting cross-linking between protein molecules, thereby forming a more stable three-dimensional network structure, stabilizing the moisture in the gel, and thus reducing the gel strength. However, when the microcapsule content is further increased to 30% (Example 14), the gel strength begins to increase. This may be attributed to the interference of excessive microcapsules on the intermolecular interactions of proteins. When the amount of microcapsules added exceeds an appropriate range, the released substances may form localized high-concentration regions in the surimi system, thereby hindering effective cross-linking and polymerization between protein molecules. In this case, the binding sites between protein molecules are occupied or shielded by the microcapsules, inhibiting the construction of the protein network structure. Consequently, water in the gel system cannot be effectively bound, resulting in dehydration and increased gel strength. In summary, adding an appropriate amount of microcapsules can significantly reduce gel strength, but excessive addition will have negative effects. Reduced gel strength means a softer, more delicate texture, suitable for those with chewing difficulties.

[0131] Figure 10 The images show the chromaticity (A), whiteness (B), and appearance (C) of the soft gels used in Examples 9-14 and Comparative Example 2. Good surimi products typically require a high-brightness, high-whiteness, and uniform color appearance. Figure 10 (A), L * a * b * These represent the gel's brightness, the red-green axis color component, and the yellow-blue axis color component, respectively. L * The higher the value, the brighter the sample; a * A positive value indicates a higher proportion of red, while a negative value indicates a higher proportion of green. * A positive value indicates a higher proportion of yellow components, while a negative value indicates a higher proportion of blue components. These parameters collectively determine the color characteristics of the surimi gel. The graph shows that the addition of microcapsules effectively improves the brightness of the soft gel; Comparative Example 2 has a lower brightness value, and as the amount of microcapsules added increases, the cod protein-based gel's brightness increases. *The increasing brightness indicates that the surimi is gradually becoming brighter. This phenomenon may be due to the interaction between the wall material in the microcapsules and the proteins in the surimi, altering the optical properties of the surimi and thus increasing its brightness. Whiteness is one of the important indicators for evaluating the appearance quality of surimi products, directly affecting consumers' visual perception and purchasing intentions. Figure 10 (B) As can be seen from the graph, compared with Comparative Example 2, the whiteness of the surimi gel generally increased with the increase of microcapsule addition. When the addition amount was 20% (Example 12), the overall whiteness value of the surimi was better. This may be related to the fact that the microcapsules filled the gaps in the cod protein-based gel structure as the addition level increased, making the gel network structure denser, enhancing light scattering, and improving whiteness. Figure 10 (C) It can be seen that the soft gel in Comparative Example 2 has a yellowish visual appearance, low whiteness, and no gloss; while the soft gels with added microcapsules (Examples 9-14) have a good gloss and white texture, making them more visually appealing and increasing consumers' willingness to purchase. In conclusion, the amount of microcapsules added has a significant impact on the appearance of surimi gel. An appropriate amount of microcapsules can effectively improve the whiteness of surimi. Therefore, in practical applications, it is necessary to design a scientific and reasonable formula according to specific circumstances to obtain the best color quality.

[0132] 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 process for the preparation of electrostatically deposited microcapsules for the preparation of soft surimi gels that are easy to eat, characterized in that, Includes the following steps: (1) A wall material solution is formed by mixing pea protein isolate aqueous solution and β-glucan aqueous solution, while simultaneously dissolving nutrients into the oil to obtain an oil phase; the concentration of nutrients in the oil phase is 0.5~1.5 mg / mL; the concentration of pea protein isolate aqueous solution is 0.5~2wt%; the concentration of β-glucan aqueous solution is 0.5~2wt%; (2) Mix and emulsify the wall material solution and oil phase, add acetic acid to adjust the pH to 3.5~4.5, and carry out a composite coagulation reaction; then add carboxymethyl chitosan aqueous solution, and add sodium hydroxide solution to adjust the pH to 5.0~6.0; finally add glutamine transferase to react, let stand to separate the layers, remove the supernatant to obtain electrostatically deposited microcapsules; The mass ratio of pea protein isolate, β-glucan, and carboxymethyl chitosan is 1-4:1:1; the mass ratio of wall material solution to oil phase is 2-4:1; and the amount of glutaminase added is 1 / 4 of the mass of pea protein isolate.

2. The method according to claim 1, characterized in that, In step (1), the oil is at least one of perilla seed oil, soybean oil, walnut oil, flaxseed oil, rapeseed oil, peanut oil, and sunflower seed oil; the nutrients are fat-soluble nutrients.

3. Electrostatically deposited microcapsules prepared by the method of claim 1 or 2.

4. The application of the electrostatically deposited microcapsules according to claim 3 in the food industry.

5. A fish paste soft gel, characterized in that, The electrostatically deposited microcapsules of claim 3 are added together with water to fish paste and pounded, then heated to gel, to obtain the fish paste soft gel.

6. The fish paste soft gel according to claim 5, characterized in that, The preparation method of the fish paste soft gel includes the following steps: after thawing frozen fish paste, it is pounded without water, salt is added and pounded, the amount of salt added is 2-3% of the mass of fish paste, water is added and pounding is continued, then the electrostatic deposition microcapsules as described in claim 3 are added and pounded for the last time, the amount of electrostatic deposition microcapsules added is 5-30% of the mass of fish paste; the fish paste is gelled by a two-stage heating method, first heated at 40 ℃ for 20-30 min, then immediately transferred to 90 ℃ for 30 min, after heating is completed, it is placed in ice water to cool, and the fish paste soft gel is obtained after cooling.

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