Preparation and evaluation of tara gum-based antibacterial color-sensitive film

Abstract

The invention relates to the technical field of food packaging films, and particularly discloses preparation and evaluation of a tara gum-based antibacterial color-sensitive film. The preparation method comprises the following steps: carrying out water-soluble alcohol precipitation on refined tara gum, dissolving the refined tara gum, acidified chitosan, polyvinyl alcohol, sodium carboxymethyl cellulose and blueberry anthocyanin into distilled water to obtain a TPCC-A solution, mixing and stirring the obtained TPCC-A solution and rosemary essential oil to obtain a final film-forming solution, and drying the film-forming solution by adopting a tape casting method to obtain the TPCC-AR packaging film. The packaging film prepared by the invention has excellent ultraviolet barrier property, mechanical property, oxidation resistance, antibacterial property and biodegradability, and can be applied to preservation and decay monitoring of fruits.

Description

Technical Field

[0001] The present invention relates to the technical field of food fresh-keeping packaging materials, and particularly relates to the preparation and evaluation of a tara gum-based antibacterial color-sensitive film. Background Art

[0002] Synthetic plastics are widely used in various industries. Due to their non-biodegradability, environmental pollution has been caused. Therefore, biodegradability and renewability are the main considerations for the environmental-friendly use of polymers. The biodegradability, availability, and biocompatibility of natural polymers have attracted the attention of the scientific community in various research fields. These green packaging materials based on natural polysaccharides have made great contributions to environmental protection. In particular, polysaccharides have been used in various fields, including drug delivery, removal of dyes and toxic heavy metals, and food packaging.

[0003] Food packaging films based on a single biopolymer component often have some disadvantages, which limit their practical applications in the food industry. For example, chitosan-based films have poor water resistance, while polyvinyl alcohol-based films have poor mechanical properties and thermal stability. Blending them together to form a blend film can effectively solve these problems. Essential oils in plants and spices have received extensive attention due to their excellent antioxidant and antibacterial activities, as well as their safety as food additives. Rosemary essential oil has effective antibacterial activity against Escherichia coli and Klebsiella pneumoniae, and can delay the spoilage of food caused by oxidation reactions in the air; and the antibacterial property can inhibit the speed of the decomposition of food by bacteria. Based on the electrostatic interaction between sodium carboxymethyl cellulose and natural colorants, sodium carboxymethyl cellulose is used to prepare a freshness indicator based on water-soluble natural colorants to reduce the migration of colorants and improve the sensitivity of the freshness indicator. Summary of the Invention

[0004] In order to solve the problems of non-biodegradability of food packaging and its lack of functions in antibacterial and monitoring food spoilage, a food packaging film with the functions of detecting the spoilage of protein foods, antibacterial, fresh-keeping, and being safe, non-toxic, and biodegradable is obtained by using four polysaccharide substances, namely tara gum, chitosan, polyvinyl alcohol, and sodium carboxymethyl cellulose, as the matrix and combining two active substances, namely blueberry anthocyanin and rosemary essential oil. To achieve the above purpose, the specific solutions provided by the present invention are as follows:

[0005] The preparation and evaluation of a tara gum-based antibacterial color-sensitive film includes the following steps:

[0006] (1) Refine tara gum by the water-soluble alcohol precipitation method to obtain refined tara gum; mix the refined tara gum, acidified chitosan powder, polyvinyl alcohol, sodium carboxymethyl cellulose, plasticizer, blueberry anthocyanin, and rosemary essential oil evenly, and centrifuge to remove impurities and bubbles to obtain a mixed solution; prepare a food packaging film from the mixed solution by the solution casting method.

[0007] (2) Further, the mass proportion of the tara gum in the mixed solution is 1.2wt% - 1.8wt%, the mass proportion of the acidified chitosan in the mixed solution is 0.1wt% - 1.4wt%, the mass proportion of the polyvinyl alcohol in the mixed solution is 0.1wt% - 1.0wt%, the mass proportion of the sodium carboxymethyl cellulose in the mixed solution is 0.01wt% - 0.1wt%, the mass proportion of the plasticizer in the mixed solution is 0.5wt% - 1.5wt%, the mass proportion of the blueberry anthocyanin in the mixed solution is 0.01wt% - 0.1wt%, and the mass proportion of the rosemary essential oil in the mixed solution is 0.1wt% - 1.0wt%.

[0008] (3) Further, the plasticizer is an aqueous glycerol solution, and the mass concentration in the aqueous glycerol solution is 45% - 55%.

[0009] (4) Further, the impurity removal and defoaming treatment is centrifugation treatment, the centrifugation speed of the centrifugation treatment is 3000r / min - 4000r / min, and the time of the centrifugation treatment is 10min - 20min.

[0010] (5) Further, the tara gum is refined by the water-soluble alcohol precipitation method. The tara gum powder is dissolved into a viscous gum solution. After precipitation treatment, the precipitate is washed with ketones and ethers and then freeze-dried and ground into powder to obtain refined tara gum.

[0011] (6) Further, for the preparation of the acidified chitosan powder, chitosan powder, water and glacial acetic acid are mixed and dissolved to obtain a chitosan solution. After alcohol precipitation treatment, filtration, washing of the precipitate, and cold drying and grinding treatment, the acidified chitosan powder is obtained.

[0012] The present invention has the following advantageous aspects:

[0013] The present invention uses four polysaccharides, namely tara gum, chitosan, polyvinyl alcohol, and sodium carboxymethyl cellulose, as the matrix, and combines two active substances, namely blueberry anthocyanin and rosemary essential oil, to prepare the TPCC-AR film. The TPCC-AR film has the functions of detecting the spoilage of protein foods, antibacterial, fresh-keeping, and being safe, non-toxic, and biodegradable. The TPCC-AR film makes up for the disadvantages of the old-fashioned packaging film with low fresh-keeping performance and poor antibacterial function, further optimizes the function of the packaging film, and extends the fresh-keeping time of food. Description of the Drawings Figure 1 It is the tensile stress-strain curve graph of the antibacterial color-sensitive film. Figure 2 It is the transmittance measurement curve graph of the antibacterial color-sensitive film. Figure 3 It is the FT-IR measurement curve graph of the antibacterial color-sensitive film. Figure 4 XRD measurement curve of antibacterial color-sensitive film. Figure 5 Absorbance and free radical scavenging rate measurement curves of antibacterial color-sensitive film. Figure 6 Antibacterial property comparison chart of antibacterial color-sensitive film. Figure 7 Trend change curves of I: L value, II: a value, III: b value of antibacterial color-sensitive film and IV: comparison chart of initial and final states. Figure 8 Phenomenon diagram of adding different pH values to antibacterial color-sensitive film. Figure 9 Fresh-keeping performance comparison chart of antibacterial color-sensitive film. Figure 10 Comparison of degradation conditions of I: unwrapped and II: wrapped antibacterial color-sensitive film and comparison chart of initial and final states of degradation. Detailed implementation mode

[0014] The following further illustrates the technical process of the present invention in combination with specific implementation examples:

[0015] Example 1

[0016] A preparation method of tara gum-based film specifically includes the following steps:

[0017] (1) Refined tara gum: Take tara gum powder, dissolve it in water to prepare a viscous gum solution, add ethanol for precipitation, stir with a glass rod to make it fully precipitate, filter to remove the filtrate, wash the precipitate twice with acetone and ether respectively, and grind it into powder after freeze-drying;

[0018] (2) Preparation of acidified chitosan: Place chitosan powder in pure water, stir magnetically, add glacial acetic acid to dissolve it, after complete dissolution, add ethanol with a ten-fold volume, then filter, wash the precipitate, and the precipitate is freeze-dried and ground into powder to obtain water-soluble acidified chitosan.

[0019] (3) Preparation of the film: Dissolve 1.4 wt% of refined tara gum, 0.4 wt% of acidified chitosan powder, 0.2 wt% of polyvinyl alcohol, 0.08 wt% of sodium carboxymethyl cellulose, 0.04 wt% of blueberry anthocyanin, and 0.16 wt% of rosemary essential oil in pure water, and stir magnetically to make it fully dissolve. Further add 0.1 wt% of glycerol aqueous solution as a plasticizer to the above solution, continue to stir for 2 h to make it evenly mixed, and then centrifuge to remove air bubbles. Pour the mixed solution into a polyethylene culture dish (10 cm × 10 cm), and obtain a tara gum-based antibacterial color-sensitive film after drying, and obtain a TPCC-AR film after drying.

[0020] Example 2

[0021] The difference from Example 1 is that in step (3), 0.08 wt% of sodium carboxymethylcellulose, 0.04 wt% of blueberry anthocyanin, and 0.16 wt% of rosemary essential oil are not added, and the remaining steps and parameters are the same. The obtained film is named TPC.

[0022] Example 3

[0023] The difference from Example 1 is that in step (3), 0.04 wt% of blueberry anthocyanin and 0.16 wt% of rosemary essential oil are not added, and the remaining steps and parameters are the same. The obtained film is named TPCC.

[0024] Example 4

[0025] The difference from Example 1 is that in step (3), 0.16 wt% of rosemary essential oil is not added, and the remaining steps and parameters are the same. The obtained film is named TPCC-A.

[0026] Perform relevant performance tests on the antibacterial color-sensitive films prepared in Examples 1 to 4. The raw materials and instruments used in the tests are as follows:

[0027] Tara gum is from Benzhen Import and Export Co., Ltd., chitosan is from Tianjin Damao Chemical Reagent Factory, polyvinyl alcohol and blueberry anthocyanin are from Shanghai Macklin Biochemical Co., Ltd., sodium carboxymethylcellulose is from Sinopharm Chemical Reagent Co., Ltd., rosemary essential oil is from Huashuo Spice Co., Ltd., and grapes are from Nanning Luowen Market.

[0028] D8A-A25 polycrystalline X-ray diffractometer, Bruker Corporation, Germany; UV-5500PC UV-visible spectrophotometer, Shanghai Yuanxi Instrument Co., Ltd.; Nicolet-6700 Thermoelectron Corp infrared spectrometer, USA; LS173B color difference meter; IKA RW20 cantilever stirrer; DHG-9053A electrothermal constant temperature forced air drying oven, Shanghai Qixin Scientific Instrument Co., Ltd.; combined shaking incubator (superimposed shaker), Tianjin Laibot Rui Instrument and Equipment Co., Ltd.; electronic digital micrometer.

[0029] The relevant detections and characterizations are as follows:

[0030] (1) Mechanical property test: Cut the TPCC-AR film into rectangular strips with a length of 70 mm and a width of 20 mm, and use a universal testing machine to test its tensile properties. The stress length of the film is 50 mm for tensile measurement. The tensile strength calculation formula is:

[0031]

[0032] Among them, F: tensile force, N; S: cross-sectional area, mm2; σ: tensile strength, MPa. The calculation formula for Young's modulus is:

[0033]

[0034] Among them, E: Young's modulus, MPa; σ: tensile strength, MPa; ε: tensile length, mm.

[0035] (2) Water vapor barrier property test: Take a glass bottle with a bottle mouth diameter of 2.7 cm, add 3.0 g of anhydrous calcium chloride as a desiccant, cut the TPCC-AR film into small squares of 4×4 cm, fix it on the glass bottle, and measure the water vapor transmission rate. Record the time interval and record the weight, and calculate the data from the formula. The calculation formula for the water vapor transmission rate is:

[0036]

[0037] Among them, G: increased weight, g; x: thickness of the test sample, m; t: time interval, s; A: test area, m2 (in this experiment: A = πR2); ΔP: at 25°C, the saturated vapor pressure of water vapor is 3169 Pa.

[0038] (3) Light barrier property test: Cut the TPC film, TPCC film, TPCC-R film, and TPCC-AR film into rectangular strips of 3 cm×1 cm in length respectively, put them into a cuvette, and use an ultraviolet spectrophotometer to perform a full-wavelength scan on the 4 groups of samples at a wavelength of 200 - 800 nm to measure the light transmittance of the film.

[0039] (4) FTIR determination: Take 2×2 cm TPC film, TPCC film, TPCC-A film, and TPCC-AR film as samples respectively for FTIR determination.

[0040] (5) XRD determination: Take samples of appropriate size from the TPC film, TPCC film, TPCC-A film, and TPCC-AR film, and measure them using an X-ray diffractometer. The data collection range is 5° - 60°, the voltage is 40 KV, and the current is 40 mA.

[0041] (6) pH sensitivity test: Drop buffer solutions with pH values of 1, 3, 7, 9, 11, and 12 on the surface of the TPCC-AR film in sequence, and observe the color change of the TPCC-AR film after placing it for 5 min.

[0042] (7) Ammonia sensitivity test: Two samples of the same size were taken from the TPCC-AR membrane and placed on the top of centrifuge tubes containing 0.1 mol / L ammonia water. Measurements were taken every 3 minutes within 0 - 30 minutes, and after 30 minutes, the color of the samples was measured using a color difference meter at 40 minutes, 55 minutes, 85 minutes, 145 minutes, 205 minutes, and 265 minutes.

[0043] (8) Antioxidant property test: Weigh 0.03 g of TPC membrane, TPCC membrane, TPCC-A membrane, and TPCC-AR membrane respectively, and place them into centrifuge tubes containing 3 mL of deionized water. Dissolve for 24 hours. Pipette 0.6 mL of TPC solution, TPCC solution, TPCC-A solution, and TPCC-AR solution respectively, and add them into centrifuge tubes containing 3.4 mL of DPPH solution. Soak for 30 minutes, then measure the absorbance of the samples using a UV spectrophotometer and calculate the scavenging rate of the samples. The formula for calculating the scavenging rate is:

[0044]

[0045] Among them, Abs(sample): absorbance of the sample; Abs(control): absorbance of the blank group

[0046] (9) Antibacterial property test: Under the condition of 90% relative air humidity, place the TPC membrane, TPCC membrane, TPCC-R membrane, and TPCC-AR membrane for 1 month, and observe the growth of mold on different sample membranes.

[0047] (10) Fresh-keeping property test: Take 6 plastic molds of the same size, fill them with a sufficient number of grapes, and cover the control group with ordinary food preservative film on the market. For the remaining four groups, cover them with TPCC membrane, TPCC-A membrane, TPCC-R membrane, and TPCC-AR membrane respectively, compare the fresh-keeping performance of the polysaccharide membrane and the preservative film, and take pictures to record the fresh-keeping situation.

[0048] (11) Degradability test: Cut 5 samples of 2×2 cm in size from the TPCC-AR membrane, bury them in compost soil, take them out after ten days, and take pictures to record the degradation situation of the samples.

[0049] The antibacterial color-sensitive membrane not only has good tensile properties but also has good anti-deformation properties. As Figure 1 can be seen, the tensile strength of the TPCC-AR membrane is 27.13 MPa, and the Young's modulus is 119.37 MPa. For the measured stress-strain curve, the stress range is 0 - 10 MPa, and the strain range is 0% - 31%.

[0050] The antibacterial color-sensitive film has good light impermeability. At 279 nm, the transmittance of ultraviolet light is 1.19%; at 565 nm, the transmittance of visible light is 36.58%. From Figure 2 It can be seen that at 279 nm, the ultraviolet light transmittance of the TPCC-AR film is the lowest, which is due to the strong absorption of ultraviolet light by the anthocyanins present in the TPCC-AR film. At 565 nm, the transmittances of the TPCC film, TPCC-R film, and TPCC-AR film are all greater than that of the TPC film. This is because the addition of carboxymethyl cellulose increases the porosity of the packaging film, making it easier for light to pass through and increasing the transmittance. Among the TPCC film, TPCC-R film, and TPCC-AR film, the TPCC-AR film has the lowest transmittance. This is because the visible light is absorbed by the anthocyanins in the TPCC-R film, reducing the visible light transmittance.

[0051] The antibacterial color-sensitive film is mainly bound by hydrogen bond interactions, and the addition of rosemary essential oil and anthocyanins does not affect the molecular structure of the antibacterial color-sensitive film. As Figure 3 shown, the intermolecular hydrogen bond stretching vibration of the -OH group occurs at 3500 cm-1 to 3200 cm-1, because the polyvinyl alcohol and chitosan contained in the TPC film, TPCC film, TPCC-A film, and TPCC-AR film have -OH groups. The stretching vibration of C-H occurs at 2890 cm-1, which is due to the presence of saturated C-H in the polyvinyl alcohol contained in the TPC film, TPCC film, TPCC-A film, and TPCC-AR film. The stretching vibration of C-O-C occurs at 1210 cm-1 to 1163 cm-1, which is because the chitosan contained in the TPC film, TPCC film, TPCC-A film, and TPCC-AR film has C-O-C.

[0052] The addition of carboxymethyl cellulose, anthocyanins, and rosemary essential oil in the antibacterial color-sensitive film does not cause the molecular bonds to break and no structural changes occur. As Figure 4 shown, the TPC film has an obvious diffraction peak at 19.72°, the TPCC film has an obvious diffraction peak at 19.64°, the TPCC-A film has an obvious diffraction peak at 19.68°, and the TPCC-AR film has an obvious diffraction peak at 19.45°. With the addition of sodium carboxymethyl cellulose, the TPCC film moves towards 19.64°, and the intensity of the crystallization peak increases. The addition of anthocyanins causes the TPCC-A film to move towards 19.68°, and the intensity of the crystallization peak decreases. The addition of rosemary essential oil causes the TPCC-AR film to move towards 19.45°, and the intensity of the crystallization peak increases.

[0053] The antibacterial color-sensitive film has excellent antioxidant activity. At 517 nm, the absorbance is 0.41, and the free radical scavenging rate is 66.2%. From Figure 5It can be seen that the TPCC-AR film has the lowest absorbance and the highest free radical scavenging rate, which proves that it has the best antioxidant activity. This is because VSA and REO are added, both of which have antioxidant properties. The absorbance of the TPCC-AR film is lower than that of the TPCC-A film, and the free radical scavenging rate is higher than that of the TPCC-A film, which proves that the antioxidant property of the TPCC-AR film is better than that of the TPCC-A film; this is because two antioxidant substances are added to the TPCC-AR film, while only one antioxidant substance is added to the TPCC-A film. The antioxidant properties of the TPC film and the TPCC film are worse than those of the TPCC-A film and the TPCC-AR film, which is because no antioxidant substances are added to the TPC film and the TPCC film.

[0054] The antibacterial color-sensitive film has good antibacterial properties. When placed in the air at a humidity of 90% for one month, no mold will be produced. Figure 6 It can be seen that TPC film and TPCC film grew large patches of mold, while TPCC-R film and TPCC-AR film did not grow mold. It can be inferred from the antibacterial experimental phenomenon that rosemary essential oil itself not only has strong antibacterial activity, but also interacts with chitosan when added to TPCC-AR film, further enhancing the antibacterial property of the film. Chitosan has limited antibacterial activity, so after one month of placement, TPC film and TPCC film grew large patches of mold; the addition of rosemary essential oil interacted with chitosan, making up for the limited antibacterial property of chitosan, further inhibiting the growth of mold, and after one month of placement, TPCC-R film and TPCC-AR film did not grow mold.

[0055] The antibacterial color-sensitive film has good ammonia sensitivity and can be used to monitor the spoilage of protein foods. Figure 7 The sample's initial state was 61.06% brightness, tending toward red and yellow, and the complete color change time was 265 minutes. The data obtained after the TPCC-AR film completely changed color in 265 minutes was consistent with the color observed by the naked eye. The TPCC-AR film was yellow after it completely changed color. Microorganisms decompose meat food and release a large amount of ammonia. The higher the concentration of ammonia vapor, the yellower the color of the TPCC-AR film. The ammonia sensitivity of the TPCC-AR film can be used to monitor the spoilage of protein foods.

[0056] The antibacterial color-sensitive membrane has good pH responsiveness and is used to monitor food spoilage. Figure 8It can be observed that in the pH range of 1 to 3, the color of the TPCC-AR film changes from red to pink. At pH 7, the TPCC-AR film does not change color. In the pH range of 9 to 13, the TPCC-AR film changes from green to yellow. These color changes are caused by the anthocyanins added to the TPCC-AR film. In a strong acid environment, the main molecular structure exists in the form of flavylium ions, and the solution appears red. As the pH value continuously increases, the flavylium cations gradually transform into colorless pseudobases through hydration equilibrium, resulting in a gradual lightening of the red color in the solution. Anthocyanins can be used as pH indicators, endowing the film with a monitoring function for facilitating the visual monitoring of food spoilage.

[0057] The antibacterial color-sensitive film has the function of extending the shelf life of food. As Figure 9 shown, in the initial state, the grapes in the mold are all in a fresh state with good color and saturation. On the 21st day, mold appears on the grapes covered with plastic wrap and TPCC film. Ordinary plastic wrap has no antibacterial effect, and its function is limited to preserving food; while the chitosan contained in the TPCC film has limited antibacterial properties, so the grapes get moldy. There is no water loss in the grapes covered with TPCC-A film, TPCC-R film and TPCC-AR film, which is related to the barrier property of the film due to the addition of sodium carboxymethylcellulose. On the 31st day, the mold area of the grapes covered with plastic wrap and TPCC film expands, water loss occurs in the grapes covered with TPCC-A film and TPCC-R film, and the TPCC-AR film has the best preservation effect, with a preservation time 10 days longer than that of ordinary plastic wrap on the market. The TPCC-AR film contains anthocyanins and rosemary essential oil. The rosemary essential oil interacts with chitosan to enhance the antibacterial property of the film; the addition of sodium carboxymethylcellulose exerts its biocompatibility and better integrates with anthocyanins with antioxidant properties.

[0058] The antibacterial color-sensitive film has good biodegradability. As Figure 10 shown in II, the complete degradation time of the TPCC-AR film is 10 days under the condition of being wrapped by foreign objects. Since the TPCC-AR film will integrate into the soil after complete degradation, to observe its complete degradation, a non-rotting net fabric is wrapped around the outer layer of the TPCC-AR film. After the TPCC-AR film is completely degraded, although there is no residue, there will be a trace left on the fabric. From Figure 10 I and II, it can be seen that the TPCC-AR film has good degradability. Without wrapping, the TPCC-AR film has significantly decomposed in nature after 4 days. Wrapping a fabric around its outer layer delays the degradation time of the TPCC-AR film to a certain extent, but there is no hindrance to the degradation of the TPCC-AR film. The good degradability of the TPCC-AR film is related to its composition. The matrix of the TPCC-AR film is a natural polysaccharide substance, and the added active substances anthocyanins and rosemary essential oil are also natural polymer substances, all of which can be decomposed under natural conditions.

[0059] The above-described are only the preferred embodiments of the present invention, and the above specific embodiments do not limit the present invention. Within the scope of the technical idea of the present invention, various deformations and modifications can occur. Any embellishment, modification, or equivalent replacement made by those of ordinary skill in the art according to the above description shall fall within the scope protected by the present invention.

Claims

1. A tara gum-based antibacterial color-sensitive film, characterized in that, Using four polysaccharide substances, namely tara gum, chitosan, polyvinyl alcohol, and sodium carboxymethyl cellulose as the matrix, and combining two active substances, namely blueberry anthocyanin and rosemary essential oil, a food packaging film with the functions of detecting protein food spoilage, antibacterial, fresh-keeping, and being safe, non-toxic, and biodegradable is obtained.

2. A method for preparing a food packaging film as described in claim 1, characterized in that, The specific steps are as follows: (1) Refine tara gum by the water-soluble alcohol precipitation method to obtain refined tara gum. (2) Mix refined tara gum, acidified chitosan powder, polyvinyl alcohol, sodium carboxymethyl cellulose, blueberry anthocyanin, and rosemary essential oil evenly, and centrifuge to remove impurities and bubbles to obtain a mixed solution. (3) Prepare a food packaging film from the mixed solution by the solution casting method.

3. The preparation method of the food packaging film according to claim 2, wherein The mass ratio of the tara gum in the mixed solution is 1.2 wt% - 1.8 wt%, the mass ratio of the acidified chitosan in the mixed solution is 0.1 wt% - 1.4 wt%, the mass ratio of the polyvinyl alcohol in the mixed solution is 0.1 wt% - 1.0 wt%, the mass ratio of the sodium carboxymethyl cellulose in the mixed solution is 0.01 wt% - 0.1 wt%, the mass ratio of the plasticizer in the mixed solution is 0.5 wt% - 1.5 wt%, the mass ratio of the blueberry anthocyanin in the mixed solution is 0.01 wt% - 0.1 wt%, and the mass ratio of the rosemary essential oil in the mixed solution is 0.1 wt% - 1.0 wt%.

4. The preparation method of the food packaging film according to claim 3, characterized in that, The plasticizer is an aqueous glycerol solution, and the mass concentration in the aqueous glycerol solution is 45% - 55%.

5. The preparation method of the food packaging film according to claim 3, wherein, The impurity and bubble removal treatment is centrifugation. The centrifugation speed of the centrifugation treatment is 3000 r / min - 4000 r / min, and the time of the centrifugation treatment is 10 min - 20 min.

6. The preparation method of the food packaging film according to claim 2, characterized in that, The water-soluble alcohol precipitation method for refining tara gum includes the following steps: Dissolve tara gum powder into a viscous gum solution. After precipitation treatment, wash the precipitate with ketones and ethers, then freeze-dry and grind it into powder to obtain refined tara gum.

7. The preparation method of the food packaging film according to claim 2, characterized in that, The preparation of the acidified chitosan powder includes the following steps: Mix chitosan powder, water, and glacial acetic acid and dissolve them to obtain a chitosan solution. After alcohol precipitation treatment, filtration, washing the precipitate, and cold-drying and grinding treatment, acidified chitosan powder is obtained.

8. Preparation and evaluation of a tara gum-based antibacterial color-sensitive film as described in claim 1.

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