Edible haematococcus pluvialis residue preservative film and preparation method thereof

Abstract

The invention provides an edible haematococcus pluvialis residue preservative film and a preparation method thereof, and relates to the technical field of food preservation, the edible haematococcus pluvialis residue preservative film comprises 0.4%-1.6% of dry haematococcus pluvialis residue, 1%-4% of a plasticizer, 0.2%-1% of a cross-linking agent and a film matrix solution according to a mass-volume ratio; the membrane matrix solution comprises chitosan with the mass-volume ratio of 1%-3% and citric acid with the mass-volume ratio of 1%-4%. A compact network structure is formed among the components, so that the adhesion between the haematococcus pluvialis residues and the chitosan is enhanced, and haematococcus pluvialis residue particles can be effectively loaded; under the flexible network structure formed by the film matrix and the cross-linking agent, the red pluvialis ball residues are protected from being damaged in the film liquid drying process, the film is not easy to become dry and crisp and crack, and finally the soft and tough edible bio-based film is formed; the technical problem that the preservative film prepared from the haematococcus pluvialis residues is lacked in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of food preservation, in particular to an edible Haematococcus pluvialis residue fresh-keeping film and a preparation method thereof. Background Art

[0002] At present, the research on bioplastics and biodegradable food cling film has attracted much attention. Biodegradable bio cling film not only achieves green safety for the environment, but also provides greater security for food safety. Many researchers have developed a variety of biodegradable packaging materials using bioactive materials such as polysaccharides and proteins. Adding antibacterial or antioxidant substances to traditional polysaccharide-based biodegradable films can enhance the antioxidant and antibacterial properties of the film and achieve the effect of delaying food spoilage. However, the antioxidant biodegradable cling film prepared by many research institutes cannot protect the color of food and is not edible. Therefore, it is of great research significance to explore the preparation of edible biodegradable cling film.

[0003] Haematococcus pluvialis is a new resource food, which is recognized as the best biological source of natural astaxanthin. It has attracted more and more attention. It can be directly added to ordinary food and health food as a raw material. It is another important economic algae after Spirulina and Chlorella, and it is also the richest natural astaxanthin source found so far. At present, most studies focus on the extraction and functional activity evaluation of astaxanthin in Haematococcus pluvialis. However, the astaxanthin and other active substances in the Haematococcus pluvialis residue cannot be completely extracted during the extraction process. Therefore, there are many by-products in the Haematococcus pluvialis residue after extraction, such as a small amount of astaxanthin, protein, and polysaccharide. These by-products are generally used as animal feed or directly discarded, causing environmental pollution and waste of resources. Therefore, the use of Haematococcus pluvialis residue after the extraction of active substances to prepare edible food packaging film is a new direction for edible food packaging, and has great development potential in the preparation of new materials.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] One of the purposes of the present invention is to provide an edible preservative film made of Haematococcus pluvialis residue, so as to at least solve the technical problem that there is a lack of preservative film prepared by using the residue of Haematococcus pluvialis in the prior art.

[0006] The second object of the present invention is to provide a method for preparing an edible Haematococcus pluvialis residue fresh-keeping film.

[0007] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0008] In a first aspect, the present invention provides an edible Haematococcus pluvialis residue fresh-keeping film, comprising 0.4% to 1.6% by mass volume of dry Haematococcus pluvialis residue, 1% to 4% of a plasticizer, 0.2% to 1% of a cross-linking agent, and a film matrix solution;

[0009] The membrane matrix solution comprises chitosan in a mass volume ratio of 1% to 3% and citric acid in a mass volume ratio of 1% to 4%.

[0010] Furthermore, the water content of the dried Haematococcus pluvialis residue is ≤0.07%;

[0011] Preferably, the chitosan is chitosan with a deacetylation degree of 80%.

[0012] Further, the plasticizer includes glycerol, Tween 60 or Tween 80, preferably glycerol;

[0013] Preferably, the cross-linking agent comprises calcium lactate or calcium chloride, preferably calcium chloride.

[0014] In a second aspect, the present invention provides a method for preparing the above-mentioned edible Haematococcus pluvialis residue cling film, comprising adding dry Haematococcus pluvialis residue and a plasticizer to a citric acid solution containing chitosan according to a formula amount, adding a cross-linking agent after homogenization, stirring evenly, ultrasonicating, and drying to obtain a cling film.

[0015] Furthermore, the method for preparing the citric acid solution containing chitosan comprises stirring and dissolving chitosan in the citric acid solution;

[0016] Preferably, the stirring and dissolving temperature is 50 to 100°C;

[0017] Preferably, the stirring and dissolving speed is 300 to 800 rpm;

[0018] Preferably, the stirring and dissolving time is 30 to 60 minutes.

[0019] Furthermore, the temperature of adding the dried Haematococcus pluvialis residue is 25-45°C.

[0020] Furthermore, the homogenization conditions include homogenization at 10000-14500 rpm for 1-5 min, preferably homogenization at 12000 rpm for 2 min.

[0021] Furthermore, the temperature of the uniform stirring is 25 to 45°C, preferably 40°C;

[0022] Preferably, the stirring speed is 200 to 800 rpm, preferably 400 rpm;

[0023] Preferably, the uniform stirring time is 20 to 60 minutes.

[0024] Furthermore, the power of the ultrasound is 100-300W, preferably 300W;

[0025] Preferably, the ultrasonication time is 30 to 60 min, preferably 30 min.

[0026] Furthermore, the drying temperature is 30-45°C, preferably 40°C;

[0027] Preferably, the drying time is 8 to 24 hours, preferably 10 hours.

[0028] The invention provides an edible Haematococcus pluvialis residue fresh-keeping film. The dried Haematococcus pluvialis residue will not affect the concentration of the film matrix solution during the preparation process and is tightly combined with other components. The dried Haematococcus pluvialis residue with a mass volume ratio of 0.4% to 1.6% has an appropriate concentration and will not cause agglomeration, caking and cracking during the film drying process. The amino groups of chitosan in the film matrix solution are protonated in a citric acid solution, and the protonated amino groups form a strong non-covalent bond interaction (ionic bond) with the carboxylic acid group of citric acid. The chitosan is combined with citric acid to have abundant hydroxyl groups, carboxyl groups and amino groups. The carboxyl groups and calcium ions will have a salt bridge effect, and the hydroxyl groups and amino groups / carboxyl groups will have a strong non-covalent bond interaction (ionic bond). There is a hydrogen bond between the components, so a dense network structure is formed between the components, which enhances the adhesion between the Haematococcus pluvialis residue and chitosan, and can effectively load the Haematococcus pluvialis residue particles, so that the cling film has natural antioxidant capacity and good antibacterial properties; under the flexible network structure formed by the membrane matrix and the cross-linking agent, the Haematococcus pluvialis residue is protected from being destroyed during the drying process of the film liquid, and the film is not easy to become brittle and cracked, and finally a soft, tough edible bio-based film is formed; combined with the membrane matrix including chitosan with a mass volume ratio of 1% to 3% and citric acid with a mass volume ratio of 1% to 4%, the dry Haematococcus pluvialis residue can be evenly dispersed, and the mechanical properties of the film are improved. The technical problem of the lack of cling film prepared using the residue of Haematococcus pluvialis in the prior art is solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0030] Figure 1 This is a comparison chart of the film formation of different dressings provided in Experiment 1 of the present invention. DETAILED DESCRIPTION

[0031] Unless otherwise defined herein, scientific and technical terms used in conjunction with the present invention shall have the meanings commonly understood by those of ordinary skill in the art. The meaning and scope of the terms should be clear, however, in the case of any potential ambiguity, the definitions provided herein take precedence over any dictionary or external definitions. In this application, unless otherwise stated, the use of "or" means "and / or". In addition, the use of the term "including" and other forms is non-limiting.

[0032] The methods and techniques of the present invention are generally performed according to conventional methods well known in the art and as described in various general and more specific references that are cited and discussed throughout the present specification unless otherwise indicated.

[0033] On one hand, the present invention provides an edible Haematococcus pluvialis residue fresh-keeping film, comprising 0.4% to 1.6% of dry Haematococcus pluvialis residue by mass volume ratio, 1% to 4% of plasticizer, 0.2% to 1% of cross-linking agent and film matrix solution;

[0034] The membrane matrix solution comprises chitosan in a mass volume ratio of 1% to 3% and citric acid in a mass volume ratio of 1% to 4%.

[0035] The dry Haematococcus pluvialis residue will not affect the concentration of the membrane matrix solution during the preparation process, and is tightly combined with other components; the dry Haematococcus pluvialis residue with a mass volume ratio of 0.4% to 1.6% is an appropriate concentration and will not cause agglomeration and rupture during the film drying process; the amino groups of chitosan in the membrane matrix solution are protonated in the citric acid solution, and the protonated amino groups form a strong non-covalent bond interaction (ionic bond) with the carboxylic acid group of citric acid. The chitosan combined with citric acid has abundant hydroxyl, carboxyl and amino groups, and the carboxyl groups will have a salt bridge effect with calcium ions. There is a hydrogen bond between the hydroxyl and amino / carboxyl groups, so The components form a dense network structure, which enhances the adhesion between the Haematococcus pluvialis residue and chitosan, and can effectively load the Haematococcus pluvialis residue particles, so that the cling film has natural antioxidant capacity and good antibacterial properties; under the flexible network structure formed by the film matrix and the cross-linking agent, the Haematococcus pluvialis residue is protected from being destroyed during the film liquid drying process, and the film is not easy to become brittle and cracked, and finally forms a soft, tough edible bio-based film; combined with the film matrix including chitosan with a mass volume ratio of 1% to 3% and citric acid with a mass volume ratio of 1% to 4%, the dry Haematococcus pluvialis residue can be evenly dispersed, and the mechanical properties of the film are improved. The technical problem of the lack of cling film prepared using the residue of Haematococcus pluvialis in the prior art is solved.

[0036] The mass volume ratio of the dried Haematococcus pluvialis residue can be but not limited to 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, 1.0%, 1.1%, 1.2%, 1.3%, 1.4%, 1.5%, or 1.6%, or any value between 0.4% and 1.6%.

[0037] The mass volume ratio of the plasticizer can be but is not limited to 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8% or 4.0%, and can also be any value between 1% and 4%.

[0038] The mass volume ratio of the cross-linking agent may be, but is not limited to, 0.2%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1.0%, and may also be any value between 0.2% and 1%.

[0039] The mass volume ratio of chitosan may be, but is not limited to, 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8% or 3.0%, and may be any value between 1% and 3%.

[0040] The mass volume ratio of citric acid can be but not limited to 1.0%, 1.2%, 1.5%, 1.8%, 2.0%, 2.2%, 2.5%, 2.8%, 3.0%, 3.2%, 3.5%, 3.8% or 4%, and can also be any value between 1% and 4%.

[0041] In some specific embodiments, the moisture content of the dried Haematococcus pluvialis residue is ≤ 0.07%.

[0042] Chitosan with a deacetylation degree of 80% has higher compatibility with Haematococcus pluvialis and has excellent film-forming ability. In some specific embodiments, the chitosan is chitosan with a deacetylation degree of 80%.

[0043] In some specific embodiments, the plasticizer includes glycerol, Tween 60 or Tween 80, preferably glycerol.

[0044] Calcium ions react with carboxyl groups in citric acid, and a secondary physical cross-linked brittle network is formed through the interaction between carboxylic acid anions and calcium ions, resulting in a synergistic cross-linking effect. In some specific embodiments, the cross-linking agent includes calcium lactate or calcium chloride, preferably calcium chloride.

[0045] According to another aspect of the present invention, a method for preparing the above-mentioned edible Haematococcus pluvialis residue cling film is also provided, comprising adding dry Haematococcus pluvialis residue and a plasticizer to a citric acid solution containing chitosan according to the formula amount, adding a cross-linking agent after homogenization, stirring evenly, ultrasonicating, and drying to obtain the cling film.

[0046] The membrane matrix solution prepared with chitosan can effectively load the particles of Haematococcus pluvialis residue, so that the Haematococcus pluvialis residue after the solvent extraction of active substances such as astaxanthin can be fully utilized; the cling film has natural antioxidant ability and good antibacterial properties, and the components are all composite regulated food additives. The safe and harmless cling film is biodegradable; the edible Haematococcus pluvialis residue film has strong antioxidant properties and low light transmittance, can effectively protect color and prevent oxidation, and can be used to preserve meat, vegetables, fruits, seafood and other foods.

[0047] In some specific embodiments, the method for preparing the citric acid solution containing chitosan comprises stirring and dissolving chitosan in the citric acid solution.

[0048] In order to improve the dissolution efficiency, in some specific embodiments, the temperature of the stirring and dissolving is 50-100° C. In some specific embodiments, the speed of the stirring and dissolving is 300-800 rpm. In some specific embodiments, the time of the stirring and dissolving is 30-60 min.

[0049] In some specific embodiments, the temperature of adding the dried Haematococcus pluvialis residue is 25-45°C.

[0050] In some specific embodiments, the homogenization conditions include homogenization at 10000-14500 rpm for 1-5 min, which can make the Haematococcus pluvialis residue evenly dispersed in the membrane matrix solution, preferably at 12000 rpm for 2 min.

[0051] In order to allow the added crosslinking agent to have sufficient reaction time with the homogenized solution, in some specific embodiments, the stirring temperature is 25 to 45° C. In some specific embodiments, the stirring speed is 200 to 800 rpm, preferably 400 rpm.

[0052] The temperature for uniform stirring may be, but is not limited to, 25°C, 28°C, 30°C, 33°C, 35°C, 38°C, 40°C, 43°C or 45°C, and may be any temperature between 25 and 45°C, preferably 40°C.

[0053] The rotation speed for uniform stirring may be, but is not limited to, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm or 800 rpm, and may be any rotation speed between 200 and 800 rpm, preferably 400 rpm.

[0054] In some specific embodiments, the uniform stirring time is 20 to 60 minutes.

[0055] In some specific embodiments, the power of the ultrasound is 100-300 W, preferably 300 W. In some specific embodiments, the time of the ultrasound is 30-60 min, preferably 30 min. Defoaming is performed.

[0056] In order to avoid destroying the activity of the Haematococcus pluvialis residue, in some specific embodiments, the drying temperature is 30-45° C. In some specific embodiments, the drying time is 8-24 hours, which can avoid over-drying of the film, resulting in shrinkage, rupture or reduction of the mechanical properties of the film.

[0057] The drying temperature may be, but is not limited to, 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C or 45°C, and may be any temperature between 30 and 45°C, preferably 40°C.

[0058] The drying time may be, but is not limited to, 8 h, 10 h, 12 h, 14 h, 16 h, 18 h, 20 h, 22 h or 24 h, and may be any time between 8 and 24 h, preferably 10 h.

[0059] The technical solution of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are part of the embodiments of the present invention, rather than 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.

[0060] Low eutectic solvent: The low eutectic solvent is composed of a hydrogen bond donor (HBA) and a hydrogen bond acceptor (HBD), and is magnetically stirred at 60°C for 20 minutes until it becomes clear and transparent, and then cooled to room temperature to obtain a low eutectic solvent. Among them, HBA is lauric acid, HBD is n-decanoic acid, and the molar ratio of HBA to HBD is 1:2.

[0061] Astaxanthin extraction: The solid-liquid ratio of Haematococcus pluvialis to the low eutectic solvent was 1:20 (w / w), and the mixture was gently stirred at 200 rpm with a magnetic bar at 40°C in the dark for 2 hours. The mixture was centrifuged at 2800×g for 5 minutes, and the supernatant was recovered.

[0062] Preparation of dried Haematococcus pluvialis residue: After the extracted Haematococcus pluvialis is added with water and centrifuged, the upper aqueous solution is removed, and the process is repeated several times until the aqueous solution is clarified, and the lower precipitate is freeze-dried to obtain dried Haematococcus pluvialis residue (water content ≤ 0.07%).

[0063] Freeze drying conditions:

[0064] 1. Edible Haematococcus pluvialis residue plastic wrap

[0065] The specific components of the edible Haematococcus pluvialis residue fresh-keeping film of each embodiment and comparative example are shown in Tables 1 to 3.

[0066] Table 1

[0067]

[0068] Table 2

[0069]

[0070] Table 3

[0071]

[0072] 2. Preparation of edible Haematococcus pluvialis residue cling film

[0073] Embodiments 5 to 8

[0074] According to the formulations of Examples 1 to 4, respectively, the following steps are performed:

[0075] (1) Preparation of membrane matrix solution: chitosan was added to citric acid solution, stirred at 600 rpm for 30 min at 100°C, and cooled.

[0076] (2) At 40° C., add dried Haematococcus pluvialis residue and a plasticizer to the membrane matrix solution prepared in step (1), and homogenize at 12,000 rpm for 2 min.

[0077] (3) adding a cross-linking agent, stirring at 400 rpm for 30 min at 40° C., and ultrasonicating at 300 W for 60 min to obtain a plastic wrap liquid.

[0078] (4) Take 20 g of the mixture and place it upside down in a glass dish. Dry it at 40°C for 10 h to obtain a plastic wrap.

[0079] Example 9

[0080] According to the formula of Example 1, follow the steps below:

[0081] (1) Preparation of membrane matrix solution: chitosan was added to citric acid solution, stirred at 800 rpm for 60 min at 50°C, and cooled.

[0082] (2) At 25° C., add dried Haematococcus pluvialis residue and a plasticizer to the membrane matrix solution prepared in step (1), and homogenize at 14,500 rpm for 1 min.

[0083] (3) adding a cross-linking agent, stirring at 800 rpm for 20 min at 25° C., and ultrasonicating at 100 W for 30 min to obtain a plastic wrap liquid.

[0084] (4) Take 30 g of the mixture and place it upside down in a glass dish. Dry it at 45°C for 10 h to obtain a plastic wrap.

[0085] Example 10

[0086] According to the formula of Example 1, follow the steps below:

[0087] (1) Preparation of membrane matrix solution: chitosan was added to citric acid solution, stirred at 300 rpm for 40 min at 80°C, and cooled.

[0088] (2) At 45° C., add the dried Haematococcus pluvialis residue and the plasticizer to the membrane matrix solution prepared in step (1), and homogenize at 10,000 rpm for 5 min.

[0089] (3) adding a cross-linking agent, stirring at 200 rpm for 60 min at 40° C., and ultrasonicating at 300 W for 30 min to obtain a plastic wrap liquid.

[0090] (4) Take 10 g of the mixture and place it upside down in a glass dish. Dry it at 45°C for 12 h to obtain a plastic wrap.

[0091] Comparative Examples 9 to 16

[0092] The difference from Example 4 is that the fresh-keeping films were prepared according to the formulations of Comparative Examples 1 to 8 respectively.

[0093] Comparative Example 17

[0094] The difference from Example 4 is that the homogenization condition is 15000 rpm for 2 min.

[0095] Comparative Example 18

[0096] The difference from Example 4 is that the homogenization condition is 12000 rpm for 6 min.

[0097] Comparative Example 19

[0098] The difference from Example 4 is that the stirring time is 15 min.

[0099] Comparative Example 20

[0100] The difference from Example 4 is that the stirring time is 65 min.

[0101] Test 1: Observation of film-forming properties

[0102] It was found that the membranes formed in Examples 5 to 10 had a smooth surface, uniform distribution of algae residue, and could be completely peeled off, with good physical properties; Comparative Example 9 could not form a membrane; although Comparative Examples 10 to 12 had a smooth surface and could be completely peeled off, some of them had slightly uneven distribution of algae residue, and the algae residue in Comparative Example 13 was incompatible with pullulan, and the membrane could not be peeled off after drying, and had a rough surface, high hardness and brittleness. In Comparative Example 14, the algae residue was added to the highly viscoelastic trisaccharide, resulting in a large number of bubbles during the preparation and drying process, affecting film formation and making it impossible to peel off the membrane, showing a membrane surface with loose bubbles. In Comparative Example 15, the algae residue agglomerated during the drying process, resulting in uneven composition, and the membrane could be completely peeled off, with a membrane showing a smooth surface and internal algae residue agglomerated. Comparative Example 16 showed a morphology with uniform distribution of components, and could be completely peeled off, but the mechanical properties and antioxidant properties of the membrane were significantly lower than those of Example 1. Comparative Examples 17 to 20 had similar surface morphologies to Example 5 and could be completely peeled off. Figure 1 As shown, the film formation photos of Example 5 and Comparative Examples 13 to 15 were selected, where A is Example 5, B is Comparative Example 13, C is Comparative Example 14, and D is Comparative Example 15.

[0103] Test 2 Mechanical properties test

[0104] Mechanical properties of the cling film prepared by the methods of Examples 5 to 10, Comparative Examples 10 to 12, and Comparative Examples 16 to 20 were measured. Specifically, the cling film sample (2 cm × 5 cm) was fixed between two metal handles of a tensile machine, the initial clamping distance was recorded, and the film sample was stretched at a constant speed. Each film sample was measured three times. The tensile strength and elongation at break of the film sample were calculated according to the following formulas:

[0105] Tensile strength = F / (W×x);

[0106] Where: F is the tensile strength (N), W is the film width (20mm), and x is the film thickness (mm).

[0107] Elongation at break (%) = L / L0 × 100;

[0108] Where: L is the elongated length of the film when it breaks (mm), and L0 is the original length of the film (clamp distance).

[0109] The specific results are shown in Table 1.

[0110] Test 3 Antioxidant capacity test

[0111] The antioxidant capacity of the cling film prepared by the methods of Examples 5 to 10, Comparative Examples 10 to 12 and Comparative Examples 16 to 20 was measured. Specifically, 100 mg of the cling film sample was weighed and added to 2 ml of deionized water, and the film solution was obtained after reacting for 30 minutes. 2 mL of the film solution was added with 2 mL of DPPH ethanol solution (0.1 mmol / L), and the absorbance of the reaction solution was measured at 517 nm after reacting at room temperature for 60 minutes. The scavenging rate of the film sample for DPPH free radicals was calculated according to Publication 6:

[0112] DPPH clearance rate (%) = (A0-A) / A0×100;

[0113] Where: A0 is the blank absorbance, A is the sample absorbance.

[0114] The specific results are shown in Table 1.

[0115] Test 4 Determination of antibacterial ability of cling film

[0116] The antibacterial ability of the cling film prepared by the methods of Examples 5 to 10, Comparative Examples 10 to 12 and Comparative Examples 16 to 20 was determined. Specifically, the antibacterial activity of the film sample was determined by the agar plate diffusion method, Escherichia coli and Staphylococcus aureus were cultured in LB liquid culture medium to OD = 0.5 (1×108 CFU / mL), centrifuged, the bacterial solution was diluted to 1×104 CFU / mL, 100 μL was added to LB solid culture medium, three groups of different circular membranes (1 cm) were attached to the surface of the culture medium, the culture medium plate was placed in a 37°C incubator, the size of the inhibition zone was observed, the diameter of the inhibition zone was measured, and the determination was repeated three times to obtain the average value.

[0117] The specific results are shown in Table 1.

[0118] Test 5: Light transmittance test

[0119] The light transmittance of the cling film prepared by the methods of Examples 5 to 10, Comparative Examples 10 to 12 and Comparative Examples 16 to 20 was measured, specifically including: using an ultraviolet spectrophotometer to measure the absorbance of the cling film at a wavelength of 200 to 800 nm, and the conversion formula of absorbance and transmittance is A=-logT.

[0120] The specific results are shown in Table 1.

[0121]

[0122]

[0123] As can be seen from Table 1, compared with Example 5, after reducing the content of dry Haematococcus pluvialis residue in Comparative Example 10, the mechanical properties decreased, the antioxidant capacity decreased, and the transmittance increased. It can be seen that an appropriate amount of dry Haematococcus pluvialis residue has a certain effect on maintaining the mechanical properties and antioxidant capacity of the cling film; in Comparative Example 11, after replacing citric acid with acetic acid, the mechanical properties and antioxidant capacity were greatly reduced, and it can be seen that not any acid solution has the same effect; in Comparative Example 12, no cross-linking agent was added, although the elongation at break was increased, the tensile strength was the lowest, and the cross-linking agent had a certain effect on balancing the elongation at break and the tensile strength; Comparative Example 16 had a high water content due to the addition of wet Haematococcus pluvialis residue, which increased the overall water content of the system, resulting in a decrease in overall performance; the film-forming properties of Comparative Examples 17 to 20 were not much different from those of Example 5, but the mechanical properties decreased to varying degrees under the preparation conditions. It can be seen that the homogenization conditions and stirring time within a certain range can improve the mechanical properties of the cling film.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. An edible Haematococcus pluvialis residue fresh-keeping film, characterized in that: The method comprises 0.4% to 1.6% of dry Haematococcus pluvialis residue, 1% to 4% of a plasticizer, 0.2% to 1% of a cross-linking agent and a membrane matrix solution in a mass volume ratio; The membrane matrix solution comprises chitosan in a mass volume ratio of 1% to 3% and citric acid in a mass volume ratio of 1% to 4%.

2. The edible Haematococcus pluvialis residue fresh-keeping film according to claim 1, characterized in that The water content of the dried Haematococcus pluvialis residue is ≤0.07%; Preferably, the chitosan is chitosan with a deacetylation degree of 80%.

3. The edible Haematococcus pluvialis residue fresh-keeping film according to claim 1, characterized in that The plasticizer includes glycerol, Tween 60 or Tween 80, preferably glycerol; Preferably, the cross-linking agent comprises calcium lactate or calcium chloride, preferably calcium chloride.

4. The method for preparing the edible Haematococcus pluvialis residue fresh-keeping film according to any one of claims 1 to 3, characterized in that: The method comprises adding dried Haematococcus pluvialis residue and a plasticizer into a citric acid solution containing chitosan according to a formula amount, adding a cross-linking agent after homogenization, stirring evenly, ultrasonicating, and drying to obtain a fresh-keeping film.

5. The preparation method according to claim 4, characterized in that: The method for preparing the citric acid solution containing chitosan comprises stirring and dissolving chitosan in the citric acid solution; Preferably, the stirring and dissolving temperature is 50 to 100°C; Preferably, the stirring and dissolving speed is 300 to 800 rpm; Preferably, the stirring and dissolving time is 30 to 60 minutes.

6. The preparation method according to claim 4, characterized in that: The temperature of adding the dried Haematococcus pluvialis residue is 25-45°C.

7. The preparation method according to claim 4, characterized in that: The homogenization conditions include homogenization at 10000-14500 rpm for 1-5 min, preferably homogenization at 12000 rpm for 2 min.

8. The preparation method according to claim 4, characterized in that: The stirring temperature is 25-45°C, preferably 40°C; Preferably, the stirring speed is 200 to 800 rpm, preferably 400 rpm; Preferably, the uniform stirring time is 20 to 60 minutes.

9. The preparation method according to claim 4, characterized in that: The power of the ultrasound is 100-300W, preferably 300W; Preferably, the ultrasonication time is 30 to 60 min, preferably 30 min.

10. The preparation method according to claim 4, characterized in that: The drying temperature is 30-45°C, preferably 40°C; Preferably, the drying time is 8 to 24 hours, preferably 10 hours.

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