Starch-chlorogenic acid-xanthan gum composite fresh-keeping coating solution, preparation method and application thereof

Abstract

This invention relates to the field of food preservation technology, specifically to a starch-chlorogenic acid-xanthan gum composite preservative coating liquid, its preparation method, and its application. The starch-chlorogenic acid-xanthan gum composite preservative coating liquid comprises the following components by mass percentage: high amylose; chlorogenic acid; xanthan gum; glycerol; and the balance being water. The beneficial effects of this invention are: the coating liquid of this invention specifically uses lotus seed starch with high amylose content as a matrix, chlorogenic acid as a functional active molecule, and xanthan gum as a freeze-thaw stabilizer, and is prepared through a multi-stage pressure-progressive high-pressure homogenization technology, effectively overcoming technical difficulties such as the easy aging and retrogradation of high amylose, the easy deactivation of polyphenolic active substances during processing, and the poor freeze-thaw stability of the composite system. It is particularly suitable for the preservation of perishable foods such as seafood, and can effectively extend shelf life.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food preservation technology, in particular to a starch-chlorogenic acid-xanthan gum composite preservation coating solution and its preparation method and application. BACKGROUND

[0002] As a new food preservation technology, composite edible film has advantages of biodegradability, environmental friendliness and functional design, and has attracted extensive attention in the field of food packaging. Starch is often used as one of the main matrix materials of edible film due to its wide source and low cost. However, the research on the preparation of composite edible film using high amylose starch (such as lotus seed starch) as the matrix is still limited, especially the systematic exploration of efficient compounding of high amylose starch and polyphenols such as chlorogenic acid.

[0003] High amylose starch is beneficial to form a dense film structure and provides binding sites for functional factors, but it is more prone to aging and retrogradation after gelatinization, which increases the brittleness of the film and reduces the freeze-thaw stability, limiting its application in the field of frozen food packaging. On the other hand, polyphenols have excellent antioxidant and antibacterial activities, which can enhance the active preservation performance of edible film and effectively delay food oxidation and inhibit microbial growth. However, polyphenols are easily inactivated during the heat treatment process of film preparation, which affects their biological activity and the preservation effect of the film. Therefore, while taking advantage of the excellent film-forming properties of high amylose starch, how to effectively maintain the biological activity of polyphenols and inhibit starch aging has become a key technical difficulty in improving the performance of such functional edible film.

[0004] In summary, there is an urgent need to develop a film-forming technology that can efficiently compound starch and polyphenols, inhibit starch aging, and improve the freeze-thaw stability of the film. Related research is expected to fill the gap in the research on high amylose starch (such as lotus seed starch) based edible film and provide an active packaging solution with application potential for high-end frozen food. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a starch-chlorogenic acid-xanthan gum composite preservation coating solution and its preparation method and application. The technical problems of unstable active ingredients, poor freeze-thaw stability and easy aging of high amylose starch-based active ingredients are solved.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is to provide a starch-chlorogenic acid-xanthan gum composite preservation coating solution, which comprises the following components in mass percentage: High amylose starch: 1.0-6.0%; Chlorogenic acid: 0.1-0.6%; Xanthan gum: 0.1-0.6%; Glycerol: 0.1-0.6%; The remainder is water.

[0007] The beneficial effects of the starch-chlorogenic acid-xanthan gum composite preservative coating liquid of the present invention are as follows: It specifically uses starch with high amylose content as the matrix and chlorogenic acid as the functional active molecule, which not only enhances the antibacterial and antioxidant properties of the coating but also prevents its deactivation during processing through its inclusion structure. Xanthan gum acts as a freeze-thaw stabilizer, inhibiting starch retrogradation and improving freeze-thaw stability through hydrogen bonding with starch molecules. This effectively overcomes the technical difficulties such as the easy retrogradation of high amylose starch, the easy deactivation of polyphenolic active substances during processing, and the poor freeze-thaw stability of the composite system.

[0008] Preferably, the above-mentioned starch-chlorogenic acid-xanthan gum composite preservative coating liquid comprises the following components by mass percentage: High amylose content: 3.0%; Chlorogenic acid: 0.4%; Xanthan gum: 0.5%; Glycerin: 0.4%; The remainder is water.

[0009] Preferably, in the above-mentioned starch-chlorogenic acid-xanthan gum composite preservative coating liquid, the high amylose is lotus seed starch.

[0010] Another technical solution provided by the present invention is: a method for preparing the above-mentioned starch-chlorogenic acid-xanthan gum composite preservative coating liquid, comprising the following steps: Lotus seed starch is dispersed in water to prepare a starch milk, which is then gelatinized. Chlorogenic acid was added to the gelatinized starch milk for pre-assembly. Add xanthan gum and stir to dissolve to obtain a mixture; The resulting mixture was subjected to high-pressure homogenization. Glycerin was added and defoaming was performed to obtain the starch-chlorogenic acid-xanthan gum composite preservative coating solution.

[0011] Preferably, in the above preparation method, the gelatinization temperature is 85°C and the gelatinization time is 30 min.

[0012] As described above, the parameters specify the gelatinization conditions, ensuring that the starch is fully gelatinized without damaging its structure.

[0013] Preferably, in the above preparation method, the chlorogenic acid is added and then stirred at 45°C in the dark for 1 h.

[0014] As described above, these parameters protect the activity of chlorogenic acid and prevent photothermal degradation.

[0015] Preferably, in the above preparation method, the high-pressure homogenization treatment adopts a stepped pressure control, and is subjected to multi-stage homogenization treatment at 20 MPa, 40 MPa and 60 MPa in sequence.

[0016] As described above, further limiting the homogenization process parameters ensures structural formation and performance optimization.

[0017] Another technical solution of the present invention is to provide an application of the coating liquid prepared by the above preparation method in the preservation of seafood products.

[0018] Preferably, the application is to spray or soak the surface of seafood products using the coating liquid.

[0019] Preferably, in the above applications, the seafood product is shrimp.

[0020] The beneficial effects of the preparation method of the starch-chlorogenic acid-xanthan gum composite preservative coating liquid of the present invention are as follows: The method of the present invention drives chlorogenic acid to embed into the helical cavity of amylose to form an inclusion structure through stepwise pressure control, and utilizes xanthan gum to construct a stable three-dimensional network. The resulting coating liquid has high inclusion rate (up to 48.23%), low water separation rate (≤15% after 5 freeze-thaw cycles), significant antibacterial properties, and excellent spraying adaptability (viscosity 50-100 MPa•s, D90 particle size ≤15 μm), making it particularly suitable for the preservation of perishable foods such as seafood, and can effectively extend shelf life. Specifically: 1) High inclusion rate and structural stability: Through multi-stage pressure progressive homogenization technology, chlorogenic acid is guided to undergo directional inclusion with amylose, transforming it from a "network interference factor" into an "ordering promotion factor", increasing the inclusion rate from 29.64% in traditional single-stage homogenization to 48.23%, thus enhancing functionality while ensuring structural stability.

[0021] 2) Excellent freeze-thaw stability: By activating the hydrogen bond crosslinking of xanthan gum through multi-stage pressure progressive homogenization technology, a stable three-dimensional network is constructed in the lotus seed starch-chlorogenic acid composite system, which reduces the water separation rate of the coating liquid to 15% after 5 freeze-thaw cycles and solves the problem that the anti-aging effect of xanthan gum is easily interfered with in complex systems.

[0022] 3) Good spraying adaptability: By controlling the process, the adverse effects of high viscosity of xanthan gum on spraying performance are overcome, so that the viscosity of the coating liquid is maintained at 50-100 MPa·s and the D90 particle size is ≤15 μm. It takes into account both freeze-thaw stability and atomization effect, and is suitable for industrial spraying operations.

[0023] 4) Green and environmentally friendly: The entire preparation process of this invention does not use chemical modifiers, and the multi-stage homogenization is a non-thermal physical treatment, which maintains the functional integrity of the active ingredients to the greatest extent and is in line with the development direction of green processing. Attached Figure Description

[0024] Figure 1 a , 1b 1c, 1d, and 1e are graphs showing the relationship between the amount of lotus seed starch added and the inclusion rate, opacity, water separation rate, viscosity, and maximum particle size of the lotus seed starch-chlorogenic acid-xanthan gum composite preservative coating liquid in Example 2 of the present invention. Figure 2a , 2b 2c, 2d, and 2e are graphs showing the relationship between the amount of chlorogenic acid added and the inclusion rate, opacity, viscosity, and maximum particle size of the lotus seed starch-chlorogenic acid inclusion composite preservative coating liquid in Example 2 of the present invention. Figure 3a , 3b 3c, 3d, and 3e are graphs showing the relationship between the amount of xanthan gum added and the inclusion rate, opacity, water separation rate, viscosity, and maximum particle size of the lotus seed starch-chlorogenic acid-xanthan gum composite preservative coating liquid in Example 2 of the present invention. Figure 4a , 4b 4c, 4d, and 4e are graphs showing the relationship between homogenization pressure and the inclusion rate, opacity, water separation rate, viscosity, and maximum particle size of the lotus seed starch-chlorogenic acid-xanthan gum composite preservative coating liquid in Example 2 of the present invention. Figure 5a , 5b 5c, 5d, and 5e are graphs showing the relationship between the amount of glycerol added and the inclusion rate, opacity, water separation rate, viscosity, and maximum particle size of the lotus seed starch-chlorogenic acid-xanthan gum composite preservative coating liquid in Example 2 of the present invention. Figure 6 The sensory score change curves of shrimp in the membrane-free group, PE film group, blank coating group and composite coating group in Example 3 of the present invention during storage; Figure 7 The pH change curves of shrimp in the membrane-free group, PE membrane group, blank coating group and composite coating group in Example 3 of the present invention during storage; Figure 8 The curves showing the changes in volatile basic nitrogen in shrimp during storage in Example 3 of this invention, including the membrane-free group, the PE film group, the blank coating group, and the composite coating group. Figure 9 The curves showing the changes in total bacterial count of shrimp in the membrane-free group, PE film group, blank coating group and composite coating group during storage in Example 3 of the present invention are shown. Figure 10 The curves showing the change in moisture content of shrimp in the membrane-free group, PE film group, blank coating group and composite coating group during storage are shown in Example 3 of the present invention. Detailed Implementation

[0025] To explain in detail the technical content, objectives, and effects of the present invention, the following description is provided in conjunction with the embodiments and accompanying drawings.

[0026] Example 1 A method for preparing a starch-chlorogenic acid-xanthan gum composite preservative coating liquid includes the following steps: 1) Lotus seed starch extraction Thawed frozen fresh lotus seeds were mixed with distilled water in a 2:3 ratio in a high-speed blender and thoroughly blended to obtain a lotus seed homogenate. The homogenate was filtered through a 100-mesh filter cloth, and the initial filtrate was collected and allowed to stand at 4°C for 6 hours. The supernatant was then carefully discarded, and the yellow impurities on the surface of the precipitate were removed. The retained precipitate was washed with four times its volume of distilled water, thoroughly stirred to disperse, and allowed to stand again for 6 hours. This water washing-precipitation process was repeated three times. Then, two times the volume of 95% ethanol was added to the precipitate, stirred at 100 rpm for 3 hours, and allowed to stand for another 6 hours, completing two alcohol washings. Finally, the ethanol-washed precipitate was removed, dried at 50°C, pulverized, and passed through a 200-mesh sieve to obtain lotus seed starch.

[0027] 2) Starch gelatinization Lotus seed starch was prepared into a 3.0 wt% starch milk and gelatinized by stirring in an 85℃ water bath for 30 min.

[0028] 3) Addition of chlorogenic acid Add 0.4 wt% chlorogenic acid solution and stir at 45°C in the dark for 1 h; 4) Xanthan gum addition Add 0.5 wt% xanthan gum and stir to dissolve; 5) High-pressure homogenization treatment After xanthan gum was dissolved, it was homogenized using a stepped pressure control method: sequentially homogenized at 20 MPa (3 min), 40 MPa (3 min), and 60 MPa (2 min).

[0029] 6) Add plasticizer Add 0.4 wt% glycerol, stir and then degas under vacuum to obtain a uniform sprayable film solution, which is the starch-chlorogenic acid-xanthan gum composite preservative coating solution.

[0030] Example 2 Performance determination of the starch-chlorogenic acid-xanthan gum composite preservative coating liquid obtained in Example 1 1. Performance testing methods 1) Measurement of opacity Take 2.0 mL of the film coating solution and place it in a cuvette. Using distilled water as a baseline, measure the transmittance of the coating solution at different starch concentrations within a wavelength range of 600 nm. Calculate the opacity value of the coating solution using the following formula: In the formula, T 600 d represents the light transmittance at a wavelength of 600 nm, and d represents the thickness (mm) of the internal cavity of the cuvette through which the X-ray passes.

[0031] 2) Determination of starch granule size The particle size distribution was determined using a Mastersizer 3000 laser diffractometer. An appropriate amount of coating solution was diluted to an opacity of 10%–15%. The mixture was analyzed at 25°C using deionized water as the dispersant in polydisperse mode. The refractive index of the dispersant was set to 1.33, and the refractive index of the starch was set to 1.53. Three measurements were taken, and the average value was recorded.

[0032] 3) Determination of chlorogenic acid inclusion rate The absorbance was measured using a Synergy H1 microplate reader. A mixture of 3.00 mL of the coating solution and 2.00 mL of iodine solution was taken, and the absorbance was measured at 675 nm. The percentage of inclusion complexes in the coating solution system was then calculated using the following formula. The blank control sample was natural lotus seed starch with added chlorogenic acid under the same treatment conditions.

[0033] A blank The absorbance value (λmax) at the maximum absorption wavelength after the reaction of natural lotus seed starch with iodine reagent was used as a blank control group. max The absorbance value (λ) at the maximum absorption wavelength after the coating solution reacts with the iodine reagent. max ).

[0034] 4) Viscosity measurement The viscosity of the coating solution was determined using an RVA-Techmaster rapid viscometer. 30.0 mL of the coating solution was placed in the reaction chamber of the rapid viscometer and mixed thoroughly. The rotation speed was 60 r / min, and the viscosity (MPa·s) was recorded after the reading stabilized.

[0035] 5) Freeze-thaw stability test Take 10 mL of the coating solution and freeze it at -18 ℃ for 24 hours. Then thaw it at room temperature (20 ℃) ​​for 12 hours. This constitutes one freeze-thaw cycle; repeat 5 times. After thawing at room temperature, centrifuge at 3000 r / min for 15 minutes, discard the supernatant, and weigh the precipitate. Calculate the water separation rate (WD): In the formula, m1(g) is the mass of the coating solution before centrifugation; m2(g) is the mass of the precipitate after centrifugation.

[0036] 2. Performance test results 1) Effect of starch concentration on coating liquid properties Please see Figures 1 a-1 e Following step 2) of Example 1, lotus seed starch was added. The effect of the amount of lotus seed starch added (1.0, 2.0, 3.0, 4.0, 5.0, 6.0 wt%) on the performance of the coating solution was systematically investigated, based on the total mass of the coating solution. The results are as follows: Figures 1 a-1 e As shown, the coating solution exhibits the best overall performance when the starch addition is 3.0 wt%, specifically characterized by good light transmittance (low opacity), concentrated particle size distribution, high chlorogenic acid inclusion rate, and a system viscosity within a suitable spraying range. Therefore, 3.0 wt% is determined to be the optimal addition amount of lotus seed starch.

[0037] 2) Effect of chlorogenic acid addition on coating liquid performance Please see Figures 2a-2e Following step 3) of Example 1, the addition of chlorogenic acid was carried out, and the effect of the amount of chlorogenic acid added (0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 wt%) on the performance of the composite system was systematically evaluated based on the total mass of the coating liquid. Figures 2a-2e The results showed that when the chlorogenic acid content was 0.4 wt%, the inclusion rate between chlorogenic acid and lotus seed starch reached a relatively high value of 48.23%, while the coating solution exhibited good transparency, suitable particle size distribution, and viscosity. Based on these results, 0.4 wt% was selected as the optimal addition amount of chlorogenic acid.

[0038] 3) Effect of xanthan gum addition on coating liquid properties Please see Figures 3a-3e Following step 4) of Example 1, the addition of xanthan gum, calculated based on the total mass of the coating solution, systematically investigated the effect of xanthan gum addition amounts (0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 wt%) on the performance of the coating solution. Figures 3a-3e It can be seen that when the xanthan gum content is 0.5 wt%, the coating solution exhibits excellent freeze-thaw stability (low water separation rate), good optical properties, and a reasonable particle size distribution. Furthermore, the inclusion rate of chlorogenic acid remains at a high level, and the system viscosity is suitable for film formation and spraying. Therefore, 0.5 wt% is selected as the optimal addition amount of xanthan gum.

[0039] 4) The effect of high-pressure homogenization pressure on the properties of coating liquid Please see Figures 4a-4d Following step 5) of Example 1, high-pressure homogenization treatment was performed, and the effects of different homogenization pressure conditions (single-stage treatment at 20 MPa, 40 MPa, and 60 MPa, and step treatment at 20→40→60 MPa) on the structure and properties of the coating liquid were compared. Figures 4a-4dThe results show that the three-stage progressive homogenization process (20→40→60 MPa) yields the best results, with the resulting coating liquid having a D90 particle size ≤15 μm, facilitating atomization and spraying, and exhibiting high encapsulation rate, good light transmittance, and moderate viscosity. Therefore, the stepped homogenization process is preferred as the final treatment condition.

[0040] 5) Effect of glycerin addition amount on the properties of coating solution Please see Figures 5a-5d Following step 6) of Example 1, a plasticizer was added, and the effect of the amount of glycerol added (0.1 / 0.2 / 0.3 / 0.4 / 0.5 / 0.6 wt%) on the structure and properties of the coating liquid was systematically evaluated based on the total mass of the coating liquid. Figures 5a-5d The results showed that when the glycerol content was 0.4 wt%, the coating solution viscosity was 96 MPa·s, exhibiting suitable flowability and spreadability. The coating film was flexible, and its optical properties, particle size distribution, and inclusion ratio remained good. Therefore, 0.4 wt% was determined to be the optimal addition amount of glycerol.

[0041] Example 3 Preservation determination of starch-chlorogenic acid-xanthan gum composite preservative coating solution 1. Preservation Measurement Method 1) Sample processing Fresh, intact prawns of similar size and weight were used for the evaluation experiment. Before coating, the prawns were rinsed three times with distilled water, and then crushed ice was added to induce sudden death.

[0042] Preparation of blank coating: The process is the same as in Example 1, except that the amount of chlorogenic acid and xanthan gum added to the coating solution is 0.

[0043] Preparation of composite coating: The preparation method is the same as described in Example 1.

[0044] The experimental grouping and sample processing were as follows: Pre-treated shrimp (intact, suddenly mortified shrimp) were randomly divided into 4 groups, with 3 shrimp per tray. The groups were: Uncoated group: Shrimp samples were placed in trays without any coating or covering; PE film group: Shrimp samples were directly covered with polyethylene (PE) cling film; Blank coated group: Shrimp samples were uniformly sprayed with a blank coating solution without chlorogenic acid, allowed to air dry briefly, and then placed in trays; Composite coated group: Shrimp samples were uniformly sprayed with the prepared composite edible coating solution, allowed to air dry briefly, and then placed in trays.

[0045] All shrimp samples from each group were placed in sterile trays after processing and stored in a cold storage at 4 ± 1℃ for preservation effect evaluation. 2) Sensory evaluation Sensory evaluation was conducted by an evaluation team of six trained assessors. Referring to the sensory evaluation standards for shrimp freshness, the samples were scored on their aroma, color, shape, muscle tissue, and the clarity of the blanching broth. The core dimensions and standards of sensory evaluation mainly include the following aspects: Color: Excellent quality shrimp (score 1.6-2.0) should have the inherent bright color and luster of their species (e.g., prawns are translucent bluish-gray), and the shell should be clear and bright; good quality (1.0-1.5) shrimp have acceptable color but slightly darker luster; average quality (0.5-0.9) shrimp have dull color, and slight blackening may occur on the head or abdomen; poor quality (0-0.4) shrimp are reddish, black, or severely lose their luster. Body surface and morphology: Excellent quality (1.6-2.0 points): The shrimp body is intact, the carapace is tightly connected to the body, there is no detachment, and it is clean and free of dirt; Good quality (1.0-1.5 points): Basically intact, a small number of broken carapace segments are allowed but they have not fallen off; Average quality (0.5-0.9 points): The body surface is not intact, and the membrane connecting the cephalothorax and abdomen may be ruptured; Deteriorated quality (0-0.4 points): The head and body are separated, the carapace is detached, and the body surface is dirty; Muscle tissue: Excellent (1.6-2.0 points) The muscle is firm and elastic, and the indentation recovers immediately after being pressed with a finger; Good (1.0-1.5 points) The elasticity is slightly poor, and the recovery after pressing is slightly slower; Average (0.5-0.9 points) The muscle is loose, has poor elasticity, and leaves an indentation; Deteriorated (0-0.4 points) The muscle is soft, inelastic, or dry and dehydrated. Odor: Excellent (1.6-2.0 points) has the inherent fresh seaweed or savory aroma of fresh shrimp, with no off-odors; Good (1.0-1.5 points) the savory aroma is slightly weakened, but there are no unpleasant off-odors; Average (0.5-0.9 points) the savory aroma is weakened, with a slight ammonia or fishy smell; Deteriorated (0-0.4 points) has a strong putrid, ammonia, or rancid smell.

[0046] Clarity of broth after blanching (if applicable): Excellent (1.6-2.0 points): The broth is clear and transparent, with a fresh and rich aroma; Good (1.0-1.5 points): The broth is slightly cloudy; Average (0.5-0.9 points): The broth is obviously cloudy; Deteriorated (0-0.4 points): The broth is extremely cloudy or has flocculent sediment and an off-flavor.

[0047] The final sensory evaluation result is based on the average total score. The quality grades are as follows: 9.0-10.0 points: excellent quality (fully acceptable to consumers), 7.0-8.9 points: good quality (acceptable to consumers), 5.0-6.9 points: average quality (barely acceptable to consumers), and 0-4.9 points: deteriorated quality (unacceptable to consumers).

[0048] 3) pH value measurement Refer to GB 5009.237 The 2016 National Food Safety Standard, "Determination of pH Value in Food," specifies the determination of the pH value of shrimp meat.

[0049] 4) Determination of volatile basic nitrogen content Refer to "GB 5009.228" 2016 National Food Safety Standard: Determination of Volatile Basic Nitrogen in Food, determined by micro-diffusion method.

[0050] 5) Determination of total bacterial count Refer to "GB 4789.2 The 2016 National Food Safety Standard for Microbiological Examination of Food: Determination of Total Colony Count was used to determine the total colony count for each test group using the plate count method.

[0051] 6) Determination of moisture distribution According to GB 5009.3-2016 National Food Safety Standard - Determination of Moisture in Food, the moisture content was determined by the 105℃ drying-to-constant-weight method. 2 g of minced shrimp meat was placed in a pre-weighed clean aluminum box and dried in a 105℃ drying oven until constant weight. The moisture content was calculated based on the weight of the aluminum box and the sample weight before and after drying. Three replicates were performed for each sample group.

[0052] 7) Data Processing Data processing and correlation analysis were performed using DPS 9.01 and Origin Pro 2024 software. Each group underwent three parallel tests. Experimental results are expressed as mean ± SD (n = 3), with significance levels... p <0.05.

[0053] 2. Preservation test results 1) The effect of edible preservative coatings on the sensory quality of shrimp In a 7-day cold storage experiment, the sensory scores of shrimp in all experimental groups gradually decreased with prolonged storage time. The sensory quality deterioration was most significant in the untreated group (no film), with its score dropping to the consumer-acceptable threshold (5.0 points) by day 3 and completely losing its edible value (0 points) by day 6. The sensory score decline trend of the PE film group (covered with polyethylene plastic wrap) and the blank coated group (coating solution without chlorogenic acid and xanthan gum) was slower than that of the untreated group, indicating that both physical barriers and basic coatings provided some protection for the shrimp. However, the sensory score of the composite coated group (composite coating solution containing chlorogenic acid and xanthan gum) remained significantly higher than that of the other groups throughout the entire storage period. p<0.05). Especially in the later stages of storage (days 5-7), the shrimp in this group were still able to maintain their inherent bluish-gray luster, muscle elasticity, and fresh aroma. The broth after blanching was also relatively clear, indicating that the antibacterial and antioxidant activities of chlorogenic acid in the composite coating effectively inhibited the blackening of the shrimp, fat oxidation, and the formation of off-odor substances.

[0054] 2) The effect of edible preservative coating on the pH value of shrimp The pH value of shrimp exhibited a typical "decline followed by increase" pattern during storage. In the initial storage period (days 1-2), the pH value of all groups decreased slightly, which is related to the production of acidic substances such as lactic acid from glycogenolysis after shrimp death. From day 3 onwards, with the intensification of microbial reproduction and enzymatic hydrolysis, alkaline substances such as ammonia and trimethylamine produced by protein decomposition accumulated, leading to a continuous increase in pH value. The pH value of the uncoated group increased the fastest, exceeding 7.7 (one of the critical points for shrimp spoilage) on day 4, indicating a rapid deterioration in quality. The pH control effect of the PE film group and the blank coated group was successively better than that of the uncoated group, but both exceeded the acceptable range on days 5-6. The pH value of the composite coated group increased the slowest throughout the storage period, remaining significantly lower than other groups until day 7. p < The concentration of chlorogenic acid (0.05) indicates that chlorogenic acid effectively delays the decomposition and putrefaction of proteins by inhibiting microbial growth and enzyme activity.

[0055] 3) Effects of edible preservative coatings on the volatile basic nitrogen content of shrimp TVB-N is a key indicator for evaluating the degree of protein degradation in aquatic products, and its content gradually increases with prolonged storage time. Figure 8 As shown, the TVB-N value of the uncoated group exceeded 30 mg / 100g (the spoilage limit for aquatic products) on day 4 and reached as high as 60.75 mg / 100g on day 7, indicating severe spoilage of the shrimp. The TVB-N value increase trend of the PE film group and the blank coated group was slower than that of the uncoated group, but their values ​​still exceeded the acceptable limit in the middle and late stages of storage. The TVB-N value of the composite coated group was the lowest throughout the storage period, reaching 29.58 mg / 100g on day 6, which was close to but did not exceed the spoilage threshold of 30 mg / 100g, and was significantly different from other groups. p< 0.05). This indicates that chlorogenic acid in the composite coating can effectively inhibit protein decomposition and delay the volatilization of nitrogenous substances, thereby significantly extending the shelf life of shrimp.

[0056] 4) The effect of edible preservative coatings on total bacterial count in shrimp The total bacterial count directly reflects the degree of microbial contamination in shrimp (shrimp freshness: Grade 1 ≤ 5.0 lg(CFU / g); Grade 2 ≈ 5.0-5.7 lg(CFU / g); spoilage ≥ 6.0 lg(CFU / g)). For example...Figure 9 As shown, the total bacterial count in the membrane-free group increased rapidly, reaching 5.48 lg (CFU / g) on ​​day 3 and as high as 8.72 lg (CFU / g) on ​​day 7, indicating a large-scale proliferation of microorganisms. The PE membrane group, due to its physical barrier effect, had a significantly lower total bacterial count than the membrane-free group. p< The concentration of CFU / g in the control group was 0.05 g, but the antibacterial effect was limited. The blank coating group further reduced the microbial growth rate, but its total colony count still showed a steady upward trend. The total colony count in the inclusion composite coating group remained the lowest throughout the storage period, reaching 6.38 lg (CFU / g) on ​​day 7, which was significantly lower than that in the other groups. p< 0.05). This indicates that chlorogenic acid, as a natural antibacterial agent, can effectively inhibit bacterial growth, and the dense coating structure synergistically constructed with xanthan gum further blocks microbial infection.

[0057] 5) The effect of edible preservative coatings on shrimp moisture content Moisture content is an important indicator for evaluating the water retention capacity and freshness of shrimp. For example... Figure 10 As shown, the moisture content of shrimp in all experimental groups decreased with prolonged storage time, but the decrease was smallest in the composite coating group, and its moisture content was significantly higher than that of the other groups throughout the entire storage period. p <0.05). The group without a membrane experienced the fastest water evaporation due to direct exposure to the refrigerated environment; the PE membrane group slowed water loss through physical barriers; the blank coated group, due to the basic coating structure's water-retention capacity, performed better than the PE membrane group. The composite coating group, benefiting from the three-dimensional network structure formed by xanthan gum and starch molecules and the antioxidant properties of chlorogenic acid, more effectively maintained muscle tissue integrity and reduced juice loss, thus exhibiting the best water-retention performance.

[0058] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent modifications made based on the content of the present invention specification and drawings, or direct or indirect applications in related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A starch-chlorogenic acid-xanthan gum composite preservative coating liquid, characterized in that, Components including the following mass percentages composition: High amylose content: 1.0-6.0%; Chlorogenic acid: 0.1-0.6%; Xanthan gum: 0.1-0.6%; Glycerin: 0.1-0.6%; The remainder is water.

2. The starch-chlorogenic acid-xanthan gum composite preservative coating liquid according to claim 1, characterized in that, Components including the following mass percentages composition: High amylose content: 3.0%; Chlorogenic acid: 0.4%; Xanthan gum: 0.5%; Glycerin: 0.4%; The remainder is water.

3. The starch-chlorogenic acid-xanthan gum composite preservative coating liquid according to claim 1, characterized in that, The high amylose content is lotus seed starch.

4. A method for preparing the starch-chlorogenic acid-xanthan gum composite preservative coating liquid according to claim 3, characterized in that, Includes the following steps: Lotus seed starch is dispersed in water to prepare a starch milk, which is then gelatinized. Chlorogenic acid was added to the gelatinized starch milk for pre-assembly. Add xanthan gum and stir to dissolve to obtain a mixture; The resulting mixture was subjected to high-pressure homogenization. Glycerin was added and defoaming was performed to obtain the starch-chlorogenic acid-xanthan gum composite preservative coating solution.

5. The preparation method according to claim 4, characterized in that, The gelatinization temperature is 85℃ and the gelatinization time is 30 min.

6. The preparation method according to claim 4, characterized in that, After the chlorogenic acid was added, the mixture was stirred at 45°C in the dark for 1 h.

7. The preparation method according to claim 4, characterized in that, The high-pressure homogenization process employs stepped pressure control, sequentially undergoing multi-stage homogenization processes at 20 MPa, 40 MPa, and 60 MPa.

8. The application of a coating liquid prepared by the preparation method according to any one of claims 4-7 in the preservation of seafood products.

9. The application according to claim 8, characterized in that, The application involves spraying or soaking the surface of seafood products with the coating liquid.

10. The application according to claim 8, characterized in that, The seafood product in question is shrimp.

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