Preparation method of lotus root residue cellulose fresh-keeping coating

Abstract

The invention discloses a preparation method of a lotus root residue cellulose fresh-keeping coating, and relates to the technical field of fresh-keeping coatings, and the preparation method comprises the following preparation steps: S1, extracting lotus root residue cellulose; s2, dissolving lotus root residue cellulose in the homogeneous solution; and S3, preparing the quaternized cellulose. According to the preparation method of the lotus root residue cellulose fresh-keeping coating, quaternized cellulose is prepared through a two-step method, firstly, cellulose is fully dissolved in a lithium hydroxide / urea system, so that the quaternization reaction is more sufficient and efficient; then, 3-chloro-2-hydroxypropyl trimethyl ammonium amide is slowly dropwise added into the cellulose dissolving solution under the condition of ice-water bath for quaternization reaction, the operation is simple, and finally, acetic acid is added into a reaction product for neutralization and dialysis treatment is performed, so that solvent residues in the reaction process are effectively removed, and the yield is high. The cellulose with excellent antibacterial property is efficiently produced with low toxicity.

Description

Technical Field

[0001] The invention relates to the technical field of fresh-keeping coatings, in particular to a method for preparing a lotus root residue cellulose fresh-keeping coating. Background Art

[0002] At present, the commonly used fruit and vegetable preservation technology mainly increases the shelf life of perishable fruits and vegetables by controlling factors such as microbial growth, dehydration and temperature. Commercially, a common fruit preservation method is waxing, which extends the shelf life of fruits by applying preservatives on fruits using weak organic acids and their derivatives. When they enter the human body, they will have adverse effects on human health; there are also some methods such as refrigeration, modified atmosphere packaging and paraffin-based active coatings, which are costly and time-consuming, and even directly change the appearance of fruits, affecting the flavor and quality of fruits. Traditional plastic food packaging provides effective protection for food, but its non-degradable problem needs to be solved urgently, and the white pollution problem caused by petroleum-based materials is becoming increasingly serious; therefore, in the concept of green packaging, it is particularly important to study new fresh-keeping packaging materials. The present invention uses biomass raw material lotus root residue, which is green and sustainable, and can solve the problems of non-renewable raw materials and difficult degradation of existing fresh-keeping materials. Summary of the invention

[0003] In view of the deficiencies in the prior art, the present invention provides a method for preparing a lotus root residue cellulose preservative coating, which solves the problems mentioned in the above background technology.

[0004] To achieve the above objectives, the present invention is implemented through the following technical scheme: a method for preparing a lotus root residue cellulose fresh-keeping coating, comprising the following preparation steps:

[0005] S1. Extraction of cellulose from lotus root residue:

[0006] S11, pre-treating lotus root residue;

[0007] S12, take 10-15g of the pretreated lotus root residue, pour it into 300-340mL of 5% sodium hydroxide solution, then add 37-38.5g of sodium sulfite, heat to 75-80℃ and stir for 100-120min;

[0008] S13, filtering and washing in sequence until neutral;

[0009] S14, using 4% hydrogen peroxide until the filter residue is bleached, then filtering and washing to neutrality in sequence, and then vacuum freeze-drying;

[0010] S2. Dissolving lotus root residue cellulose in a homogeneous solution:

[0011] S21, quickly adding lotus root residue cellulose into the solid-liquid mixing system and stirring evenly;

[0012] S22, after cooling, centrifuging to obtain a cellulose solution;

[0013] S3, preparing quaternized cellulose:

[0014] S31, under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution and react for 20-24 hours;

[0015] S32, neutralizing the product with dilute hydrochloric acid or acetic acid aqueous solution to a weak alkaline state;

[0016] S33, put the solution into a dialysis bag and dialyze it for 3-5 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0017] Preferably, in S11, the specific pretreatment method for the lotus root residue is: place the lotus root residue in a drying box at 55-65°C to dry, then use a grinder to crush it, add distilled water, and then add 0.2% amylase, react for 3.5-4h in a water bath at 50-60°C, test with iodine solution, and after no blue change, heat the water bath to 80-90°C and react for 1.5-2h, centrifuge at a speed of 3500-4500r / min, and dry and store the precipitate at a temperature of 45-55°C.

[0018] Preferably, the mass ratio of the lotus root residue powder to distilled water is 1:(10-12).

[0019] Preferably, in S21, the solid-liquid mixed system is prepared by mixing LiOH, urea and deionized water, and the mass ratio thereof is 7:12:81.

[0020] Preferably, in S21, the stirring speed is 800-1200 r / min, and the stirring time is 3-5 min.

[0021] Preferably, in S21, the temperature is lowered to 0-5°C, the centrifugal speed is 6000-8000r / min, and the centrifugal time is 8-10min.

[0022] Preferably, in S33, the molecular weight cutoff of the dialysis bag is 7000-8000D.

[0023] Preferably, in S31, the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to anhydrous glucose units of lotus root residue cellulose is 3, 6, 9, 12, or 15.

[0024] Beneficial Effects

[0025] The present invention provides a method for preparing a lotus root residue cellulose fresh-keeping coating. Compared with the prior art, the method has the following beneficial effects: the method for preparing the lotus root residue cellulose fresh-keeping coating prepares quaternized cellulose by a two-step method, firstly, cellulose is fully dissolved in a lithium hydroxide / urea system, so that the quaternization reaction is more sufficient and efficient, and then 3-chloro-2-hydroxypropyltrimethylammonium amide is slowly added to the cellulose dissolving solution under the condition of an ice water bath to carry out a quaternization reaction, which is simple to operate, and finally, acetic acid is added to the reaction product for neutralization and then dialyzed, which also effectively removes the solvent residue in the reaction process, and produces cellulose with excellent antibacterial properties with high efficiency and low toxicity; and in the present invention, the lotus root residue cellulose is a natural polymer, which itself has excellent biocompatibility, so the quaternized lotus root residue cellulose of the present invention has good biocompatibility while having antibacterial properties, which can be of practical significance for the application in the field of food packaging. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Pictures of lotus root residue cellulose and quaternized lotus root residue cellulose provided for the preparation method of lotus root residue cellulose fresh-keeping coating of the present invention;

[0027] Figure 2 Live-dead staining diagram of mouse osteoblasts co-cultured with quaternary ammonium cellulose provided in the preparation method of the lotus root residue cellulose preservative coating of the present invention;

[0028] Figure 3 A diagram showing the antibacterial effect of quaternized cellulose on Escherichia coli provided by a method for preparing a lotus root residue cellulose preservative coating of the present invention;

[0029] Figure 4 Fourier infrared image of quaternized cellulose provided for the preparation method of lotus root residue cellulose preservative coating of the present invention;

[0030] Figure 5 A strawberry preservation effect diagram of a quaternary ammonium cellulose coating provided for the preparation method of a lotus root residue cellulose preservation coating of the present invention. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] Example 1

[0033] A method for preparing a lotus root residue cellulose fresh-keeping coating comprises the following steps:

[0034] S1. Extraction of cellulose from lotus root residue: dry the lotus root residue in a drying oven at 55°C, then grind it with a mill, add distilled water at a mass ratio of 1:10, then add 0.2% amylase, react in a 50°C water bath for 3.5 hours, test with iodine solution, and after no blueing, heat the water bath to 80°C for 1.5 hours, centrifuge at 3500r / min, and dry the precipitate at 45°C for storage; take 10g of the treated lotus root residue, pour it into 300mL of 5% sodium hydroxide solution by mass, add 37g of sodium sulfite, heat to 75°C and stir for 100min; filter and wash to neutrality in turn; use 4% hydrogen peroxide until the filter residue is bleached, filter and wash to neutrality in turn, and then freeze-dry in vacuum;

[0035] S2. Dissolving lotus root residue cellulose in a homogeneous solution: quickly putting lotus root residue cellulose into a system prepared by mixing LiOH, urea and deionized water in a mass ratio of 7:12:81, and then stirring at a speed of 800 r / min for 3 minutes; cooling to 0°C, and centrifuging at a speed of 6000 r / min for 8 minutes to obtain a cellulose solution;

[0036] S3. Preparation of quaternized cellulose: Under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution, wherein the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 3, and react for 20 hours; neutralize the product with dilute hydrochloric acid or acetic acid aqueous solution to weak alkalinity; put the solution into a dialysis bag with a molecular weight cutoff of 7000D and dialyze the solution for 3 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0037] Example 2

[0038] A method for preparing a lotus root residue cellulose fresh-keeping coating comprises the following steps:

[0039] S1. Extraction of cellulose from lotus root residue: dry the lotus root residue in a drying oven at 57°C, then grind it with a mill, add distilled water at a mass ratio of 1:11, then add 0.2% amylase, react in a 52°C water bath for 3.6 hours, test with iodine solution, and after no blueing, heat the water bath to 82°C for 1.6 hours, centrifuge at 3800r / min, and dry the precipitate at 47°C for storage; take 11g of the treated lotus root residue, pour it into 310mL of 5% sodium hydroxide solution by mass, add 37.5g of sodium sulfite, heat to 76°C and stir for 105min; filter and wash to neutrality in turn; use 4% hydrogen peroxide until the filter residue is bleached, filter and wash to neutrality in turn, and then freeze-dry in vacuum;

[0040] S2. Dissolving lotus root residue cellulose in a homogeneous solution: quickly putting lotus root residue cellulose into a system prepared by mixing LiOH, urea and deionized water in a mass ratio of 7:12:81, and then stirring at a speed of 900 r / min for 4 minutes; cooling to 1°C, and centrifuging at a speed of 6500 r / min for 9 minutes to obtain a cellulose solution;

[0041] S3. Preparation of quaternized cellulose: Under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution, wherein the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 6, and react for 21 hours; neutralize the product with dilute hydrochloric acid or acetic acid aqueous solution to weak alkalinity; put the solution into a dialysis bag with a molecular weight cutoff of 7200D and dialyze the solution for 4 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0042] Example 3

[0043] A method for preparing a lotus root residue cellulose fresh-keeping coating comprises the following steps:

[0044] S1. Extraction of cellulose from lotus root residue: dry the lotus root residue in a drying oven at 60°C, then crush it with a mill, add distilled water at a mass ratio of 1:10, then add 0.2% amylase, react in a 55°C water bath for 3.7 hours, test with iodine solution, and after no blueing, heat the water bath to 85°C for 1.7 hours, centrifuge at 3700r / min, and dry the precipitate at 50°C for storage; take 12g of the treated lotus root residue, pour it into 320mL of 5% sodium hydroxide solution by mass, add 38g of sodium sulfite, heat to 77°C and stir for 110min; filter and wash to neutrality in turn; use 4% hydrogen peroxide until the filter residue is bleached, filter and wash to neutrality in turn, and then freeze-dry in vacuum;

[0045] S2. Dissolving lotus root residue cellulose in a homogeneous solution: quickly putting lotus root residue cellulose into a system prepared by mixing LiOH, urea and deionized water in a mass ratio of 7:12:81, and then stirring at a speed of 900 r / min for 5 minutes; cooling to 3°C, and centrifuging at a speed of 7000 r / min for 10 minutes to obtain a cellulose solution;

[0046] S3. Preparation of quaternized cellulose: Under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution, wherein the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 9, and react for 22 hours; neutralize the product with dilute hydrochloric acid or acetic acid aqueous solution to a weak alkalinity; put the solution into a dialysis bag with a molecular weight cutoff of 7400D and dialyze the solution for 5 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0047] Example 4

[0048] A method for preparing a lotus root residue cellulose fresh-keeping coating comprises the following steps:

[0049] S1. Extraction of cellulose from lotus root residue: dry the lotus root residue in a drying oven at 62°C, then grind it with a mill, add distilled water at a mass ratio of 1:11, then add 0.2% amylase, react in a 58°C water bath for 3.8h, test with iodine solution, and after no blueing, heat the water bath to 86°C for 1.8h, centrifuge at 4000r / min, and dry the precipitate at 52°C for storage; take 13g of the treated lotus root residue, pour it into 330mL of 5% sodium hydroxide solution by mass, add 38.5g of sodium sulfite, heat to 78°C and stir for 115min; filter and wash to neutrality in turn; use 4% hydrogen peroxide until the filter residue is bleached, filter and wash to neutrality in turn, and then freeze-dry in vacuum;

[0050] S2. Dissolving lotus root residue cellulose in a homogeneous solution: quickly putting the lotus root residue cellulose into a system prepared by mixing LiOH, urea and deionized water in a mass ratio of 7:12:81, and then stirring at a speed of 1000 r / min for 4 minutes; cooling to 4°C, and centrifuging at a speed of 7200 r / min for 10 minutes to obtain a cellulose solution;

[0051] S3. Preparation of quaternized cellulose: Under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution, wherein the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 12, and react for 23 hours; neutralize the product with dilute hydrochloric acid or acetic acid aqueous solution to weak alkalinity; put the solution into a dialysis bag with a molecular weight cutoff of 7800D and dialyze the solution for 3 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0052] Example 5

[0053] A method for preparing a lotus root residue cellulose fresh-keeping coating comprises the following steps:

[0054] S1. Extraction of cellulose from lotus root residue: dry the lotus root residue in a drying oven at 65°C, then crush it with a mill, add distilled water at a mass ratio of 1:12, then add 0.2% amylase, react in a 60°C water bath for 4 hours, test with iodine solution, and after no blueing, heat the water bath to 90°C for 2 hours, centrifuge at 4500r / min, and dry the precipitate at 55°C for storage; take 15g of the treated lotus root residue, pour it into 340mL of 5% sodium hydroxide solution by mass, add 38.5g of sodium sulfite, heat to 80°C and stir for 120min; filter and wash to neutrality in turn; use 4% hydrogen peroxide until the filter residue is bleached, filter and wash to neutrality in turn, and then freeze-dry in vacuum;

[0055] S2. Dissolving lotus root residue cellulose in a homogeneous solution: quickly putting lotus root residue cellulose into a system prepared by mixing LiOH, urea and deionized water in a mass ratio of 7:12:81, and then stirring at a speed of 1200 r / min for 5 minutes; cooling to 5°C, and centrifuging at a speed of 8000 r / min for 10 minutes to obtain a cellulose solution;

[0056] S3. Preparation of quaternized cellulose: Under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution, wherein the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 15, and react for 24 hours; neutralize the product with dilute hydrochloric acid or acetic acid aqueous solution to a weak alkalinity; put the solution into a dialysis bag with a molecular weight cutoff of 8000D and dialyze the solution for 5 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

[0057] Comparative Example 1

[0058] Compared with Example 1, the difference is that no quaternary ammonium cellulose is added.

[0059] Safety evaluation experiment of ammonium cellulose: Mouse osteoblasts were seeded at a concentration of 20,000 cells / well in a 96-well plate, cultured in 200 μL of DMEM containing 10% fetal bovine serum for 1 day, and quaternary ammonium cellulose was added for 2 days. After the quaternary ammonium cellulose was washed away with PBS, the living cells were stained with live and dead cell dyes calcein and propidium iodide, and analyzed and observed by fluorescence microscopy; the excitation light was set to 495 nm, and the fluorescence emission between 510-530 nm was recorded.

[0060] Antibacterial experiment of quaternary ammonium cellulose: Escherichia coli was inoculated in Luria-Bertani broth and amplified in a bacterial shaker for 12 hours. The bacterial solution was gradiently diluted and 10 mg / ml of quaternary ammonium cellulose with different degrees of substitution was added thereto. After thorough mixing, the solution was cultured in a bacterial shaker for 3 hours. The bacterial solution that was not co-cultured with quaternary ammonium cellulose with different degrees of substitution was used as the control group. The bacteria were then diluted to 108 CFU / mL, and 3 μL of the diluted bacterial solution was taken for coating and cultured for 24 hours to observe the antibacterial effect of quaternary ammonium cellulose.

[0061] Strawberry preservation experiment with quaternary ammonium cellulose coating: Rinse fresh strawberries and dry the surface moisture in a natural environment, then evenly apply the dissolved quaternary ammonium cellulose solution with different substitution degrees on the surface of the strawberries, then put each group of fruits in an artificial climate box at a temperature of 26°C and a humidity of 80%, and regularly observe the corruption of each group of fruits.

[0062] like Figure 2 As shown, the survival rate of cells co-cultured with quaternary ammonium cellulose was not inhibited, and compared with the cells in the control group, the cells in the experimental group were more extended, which also showed that the growth state of the cells was better at this time, thus indicating that the quaternary ammonium cellulose of the present invention has excellent biocompatibility.

[0063] like Figure 3 As shown, the control group had no obvious antibacterial effect, while in the experimental group, as the degree of quaternization increased, the antibacterial effect gradually increased, and the group with the highest degree of quaternization substitution was basically able to completely inhibit the growth of Escherichia coli, which proved that the quaternized cellulose of the present invention has an excellent antibacterial effect.

[0064] like Figure 4 As shown in Figure 2, the characteristic peaks in the infrared spectrum of quaternary ammonium salts are in the range of 1450-1600 cm -1 interval, respectively 1450cm -1 and 1565cm -1 The corresponding ones are CH bending vibration and CN stretching vibration in the quaternary ammonium salt molecule. As shown in the figure, the peaks at the two positions increase with the proportion of CHPTAC in the feed, and the diffraction peak intensity increases, indicating that the corresponding degree of quaternization is higher. Therefore, it can be proved that the preparation method of quaternization modification of the present invention is stable and effective.

[0065] like Figure 5 As shown, with the increase of quaternary ammonium substitution degree, the preservation effect on strawberries gradually increases. The strawberries of Comparative Example 1 went corrupt on the third day, while the best performing groups were Example 4 and Example 5. The strawberries remained in good condition after being stored for 6 days. Therefore, the quaternary ammonium cellulose preservative material of the present invention effectively prolongs the storage period of strawberries.

[0066] Meanwhile, the contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0067] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device.

[0068] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a lotus root residue cellulose fresh-keeping coating, characterized in that: The method comprises the following preparation steps: S1. Extraction of cellulose from lotus root residue: S11, pre-treating lotus root residue; S12, take 10-15g of the pretreated lotus root residue, pour it into 300-340mL of 5% sodium hydroxide solution, then add 37-38.5g of sodium sulfite, heat to 75-80℃ and stir for 100-120min; S13, filtering and washing in sequence until neutral; S14, using 4% hydrogen peroxide until the filter residue is bleached, then filtering and washing to neutrality in sequence, and then vacuum freeze-drying; S2. Dissolving lotus root residue cellulose in a homogeneous solution: S21, quickly adding lotus root residue cellulose into the solid-liquid mixing system and stirring evenly; S22, after cooling, centrifuging to obtain a cellulose solution; S3, preparing quaternized cellulose: S31, under ice bath conditions, slowly add 3-chloro-2-hydroxypropyltrimethylammonium amide to the cellulose solution and react for 20-24 hours; S32, neutralizing the product with dilute hydrochloric acid or acetic acid aqueous solution to a weak alkaline state; S33, put the solution into a dialysis bag and dialyze it for 3-5 days, then freeze-dry it with a freeze dryer, and then pour it into deionized water to dissolve it, so as to obtain the lotus root residue cellulose preservative coating.

2. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In the S11, the specific pretreatment method for the lotus root residue is: place the lotus root residue in a drying box at 55-65°C to dry, then use a grinder to crush it, add distilled water, and then add 0.2% amylase, react for 3.5-4 hours in a water bath at 50-60°C, use iodine solution to test, if there is no blue change, heat the water bath to 80-90°C to react for 1.5-2 hours, centrifuge at a speed of 3500-4500r / min, and dry the precipitate at a temperature of 45-55°C for storage.

3. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 2, characterized in that: The mass ratio of the lotus root residue powder to distilled water is 1:(10-12).

4. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In S21, the solid-liquid mixed system is prepared by mixing LiOH, urea and deionized water, and the mass ratio thereof is 7:12:

81.

5. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In S21, the stirring speed is 800-1200 r / min, and the stirring time is 3-5 min.

6. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In S22, the temperature is lowered to 0-5°C, the centrifugal speed is 6000-8000 r / min, and the centrifugal time is 8-10 min.

7. The method for preparing a lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In the S33, the molecular weight cut-off of the dialysis bag is 7000-8000D.

8. The method for preparing the lotus root residue cellulose fresh-keeping coating according to claim 1, characterized in that: In S31, the feed ratio of 3-chloro-2-hydroxypropyltrimethylammonium amide to the anhydrous glucose unit of lotus root residue cellulose is 3, 6, 9, 12, and 15.

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