An edible Haematococcus pluvialis residue preservation film and its preparation method

Abstract

This invention provides an edible Haematococcus pluvialis residue preservation film and its preparation method, relating to the field of food preservation technology. The film comprises 0.4%–1.6% (w / v) dried Haematococcus pluvialis residue, 1%–4% plasticizer, 0.2%–1% crosslinking agent, and a membrane matrix solution. The membrane matrix solution includes 1%–3% (w / v) chitosan and 1%–4% citric acid. A dense network structure is formed between the components, enhancing the adhesion between the Haematococcus pluvialis residue and chitosan, effectively loading the Haematococcus pluvialis residue particles. Under the flexible network structure formed by the membrane matrix and crosslinking agent, the Haematococcus pluvialis residue is protected from damage during the drying process of the membrane solution, preventing the film from becoming brittle and cracking, ultimately forming a soft and tough edible bio-based film. This invention solves the technical problem of the lack of preservation films prepared using Haematococcus pluvialis residue in the prior art.

Description

Technical Field

[0001] This invention relates to the field of food preservation technology, and in particular to an edible Haematococcus pluvialis residue preservation film and its preparation method. Background Technology

[0002] Current research on bioplastics and biodegradable food preservation films has attracted much attention. Biodegradable food preservation films not only achieve environmental safety but also provide greater security for food safety. Many researchers have developed various biodegradable packaging materials using bioactive materials such as polysaccharides and proteins. Adding antibacterial or antioxidant substances to traditional polysaccharide-based biodegradable films can enhance their antioxidant and antibacterial properties, thus delaying food spoilage. However, many antioxidant biodegradable food preservation films prepared by research institutes cannot preserve food color and are not edible. Therefore, exploring the preparation of edible biodegradable food preservation films is of great research significance.

[0003] Haematococcus pluvialis is a novel food resource, widely recognized as the best biological source of natural astaxanthin, and has attracted increasing attention. It can be directly added to ordinary and health foods, making it another important economical algae after spirulina and chlorella, and the richest source of natural astaxanthin discovered to date. Currently, most research focuses on the extraction and functional activity evaluation of astaxanthin from Haematococcus pluvialis. However, the extraction process still cannot completely extract astaxanthin and other active substances from the Haematococcus pluvialis residue. Therefore, the residue contains many byproducts, such as small amounts of astaxanthin, protein, and polysaccharides. These byproducts are generally used as animal feed or discarded directly, causing environmental pollution and resource waste. Therefore, using the Haematococcus pluvialis residue after extracting active substances to prepare edible food packaging films is a new direction for edible food packaging, with enormous development potential in new material preparation.

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

[0005] One of the objectives of this invention is to provide an edible Haematococcus pluvialis residue preservation film, so as to at least solve the technical problem of the lack of preservation films prepared using Haematococcus pluvialis residue in the prior art.

[0006] The second objective of this invention is to provide a method for preparing an edible Haematococcus pluvialis residue preservation film.

[0007] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted:

[0008] In a first aspect, the present invention provides an edible Haematococcus pluvialis residue preservation film, comprising 0.4% to 1.6% by weight / volume of dried Haematococcus pluvialis residue, 1% to 4% of plasticizer, 0.2% to 1% of crosslinking agent and film matrix solution;

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

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

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

[0012] Furthermore, the plasticizer includes glycerin, Tween 60 or Tween 80, preferably glycerin;

[0013] Preferably, the crosslinking agent includes calcium lactate or calcium chloride, preferably calcium chloride.

[0014] Secondly, the present invention provides a method for preparing the above-mentioned edible Haematococcus pluvialis residue preservation film, comprising adding dried Haematococcus pluvialis residue and plasticizer to a citric acid solution containing chitosan according to the formula amount, homogenizing, adding a crosslinking agent and stirring evenly, sonicating, and drying to obtain the preservation film.

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

[0016] Preferably, the temperature for stirring and dissolving is 50~100℃;

[0017] Preferably, the stirring speed for dissolving is 300~800 rpm;

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

[0019] Furthermore, the temperature at which the dried Haematococcus pluvialis residue is added is 25~45℃.

[0020] Furthermore, the homogenization conditions include homogenizing at 10,000 to 14,500 rpm for 1 to 5 minutes, preferably at 12,000 rpm for 2 minutes.

[0021] Furthermore, the temperature at which the stirring is homogenized is 25~45℃, preferably 40℃;

[0022] Preferably, the stirring speed is 200~800 rpm, and more preferably 400 rpm;

[0023] Preferably, the time for mixing is 20 to 60 minutes.

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

[0025] Preferably, the ultrasound duration is 30-60 minutes, and more preferably 30 minutes.

[0026] Furthermore, the drying temperature is 30~45℃, preferably 40℃;

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

[0028] This invention provides an edible Haematococcus pluvialis residue preservation film. The dried Haematococcus pluvialis residue does not affect the concentration of the membrane matrix solution during preparation and is tightly bound to other components. A suitable concentration of dried Haematococcus pluvialis residue (0.4%~1.6% by mass / volume) prevents agglomeration and cracking during film drying. In the membrane matrix solution, the amino groups of chitosan are protonated in citric acid solution. These protonated amino groups form strong non-covalent interactions (ionic bonds) with the carboxylic acid groups of citric acid. The combination of chitosan and citric acid results in abundant hydroxyl, carboxyl, and amino groups. The carboxyl groups exhibit a salt bridge effect with calcium ions, and the hydroxyl groups interact with the amino / carboxyl groups. Hydrogen bonds exist between the components, forming a dense network structure that enhances the adhesion between Haematococcus pluvialis residue and chitosan. This effectively loads the Haematococcus pluvialis residue particles, giving the food preservation film natural antioxidant capabilities and good antibacterial properties. The flexible network structure formed by the membrane matrix and cross-linking agent protects the Haematococcus pluvialis residue from damage during membrane drying, preventing the film from becoming brittle or cracking, ultimately forming a soft, tough, edible bio-based film. Combined with a membrane matrix comprising 1%–3% chitosan and 1%–4% citric acid by weight / volume, the dried Haematococcus pluvialis residue can be evenly dispersed, improving the mechanical properties of the film. This solves the technical problem of the lack of food preservation films prepared using Haematococcus pluvialis residue in existing technologies. Attached Figure Description

[0029] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0030] Figure 1 This is a comparison diagram of film formation of different dressings provided in Experiment 1 of the present invention. Detailed Implementation

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

[0032] Unless otherwise stated, the methods and techniques of the present invention are generally carried out according to conventional methods well known in the art and as described in various general and more specific references, which are cited and discussed throughout this specification.

[0033] The present invention provides an edible Haematococcus pluvialis residue preservation film, comprising 0.4% to 1.6% by weight / volume of dried Haematococcus pluvialis residue, 1% to 4% of plasticizer, 0.2% to 1% of crosslinking agent and film matrix solution;

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

[0035] The dried Haematococcus pluvialis residue does not affect the concentration of the membrane matrix solution during preparation and is tightly bound to other components. A suitable concentration of dried Haematococcus pluvialis residue (0.4%–1.6% by mass / volume) will not cause agglomeration or cracking during membrane drying. In the membrane matrix solution, the amino groups of chitosan are protonated in citric acid solution. The protonated amino groups form strong non-covalent interactions (ionic bonds) with the carboxylic acid groups of citric acid. Chitosan, combined with citric acid, possesses abundant hydroxyl, carboxyl, and amino groups. The carboxyl groups exhibit a salt-bridge effect with calcium ions, and hydrogen bonds exist between hydroxyl groups and amino / carboxyl groups. The components form a dense network structure, enhancing the adhesion between Haematococcus pluvialis residue and chitosan, effectively loading Haematococcus pluvialis residue particles, giving the cling film natural antioxidant capabilities while also providing excellent antibacterial properties. The flexible network structure formed by the membrane matrix and cross-linking agent protects the Haematococcus pluvialis residue from damage during membrane drying, preventing the film from becoming brittle and cracking, ultimately forming a soft, tough, edible bio-based film. Combined with a membrane matrix comprising 1%–3% chitosan and 1%–4% citric acid by weight / volume, the dried Haematococcus pluvialis residue can be uniformly dispersed, improving the mechanical properties of the film. This solves the technical problem of the lack of cling film prepared using Haematococcus pluvialis residue in existing technologies.

[0036] The mass-to-volume ratio of the dried Haematococcus pluvialis residue can be, but is 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-to-volume ratio of 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%, or any value between 1% and 4%.

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

[0039] The mass-to-volume ratio of chitosan can 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%, or any value between 1% and 3%.

[0040] The mass-to-volume ratio of citric acid 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%, or 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 degree of deacetylation of 80% exhibits higher compatibility with Haematococcus pluvialis and excellent film-forming ability. In some specific embodiments, the chitosan is chitosan with a degree of deacetylation of 80%.

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

[0044] Calcium ions react with the carboxyl groups in citric acid, forming a secondary physically cross-linked brittle network through the interaction of 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 preservation film is also provided, comprising adding dried Haematococcus pluvialis residue and plasticizer to a citric acid solution containing chitosan according to the formula amount, homogenizing, adding a crosslinking agent and stirring evenly, sonicating, and drying to obtain the preservation film.

[0046] The membrane matrix solution prepared using chitosan can effectively load Haematococcus pluvialis residue particles, allowing for full utilization of the Haematococcus pluvialis residue after solvent extraction of active substances such as astaxanthin. This gives the preservation film natural antioxidant capabilities while also providing good antibacterial properties. Furthermore, all components are classified as compound food additives, ensuring the safety and harmlessness of the prepared preservation film, which is also biodegradable. The edible Haematococcus pluvialis residue film has strong antioxidant properties and low light transmittance, effectively protecting color and preventing oxidation. It can be used for the preservation of meat, vegetables, fruits, seafood, and other foods.

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

[0048] To improve dissolution efficiency, in some specific embodiments, the temperature for stirring and dissolving is 50~100℃. In some specific embodiments, the stirring speed is 300~800 rpm. In some specific embodiments, the stirring and dissolving time is 30~60 min.

[0049] In some specific implementations, the temperature at which dried Haematococcus pluvialis residue is added is 25~45℃.

[0050] In some specific embodiments, the homogenization conditions include homogenizing at 10,000-14,500 rpm for 1-5 minutes. This ensures that the Haematococcus pluvialis residue is uniformly dispersed in the membrane matrix solution. Preferably, homogenization is performed at 12,000 rpm for 2 minutes.

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

[0052] The temperature at which the mixture is stirred evenly can 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, or any temperature between 25°C and 45°C, preferably 40°C.

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

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

[0055] In some specific embodiments, the ultrasonic power is 100~300W, preferably 300W. In some specific embodiments, the ultrasonic duration is 30~60min, preferably 30min. Defoaming is then performed.

[0056] To avoid damaging the activity of 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. This avoids over-drying of the film, which could lead to shrinkage, cracking, or reduced mechanical properties.

[0057] The drying temperature can 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, or any temperature between 30°C and 45°C, preferably 40°C.

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

[0059] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0060] Eutectic solvent: The eutectic solvent is composed of a hydrogen bond donor (HBA) and a hydrogen bond acceptor (HBD). The mixture is magnetically stirred at 60°C for 20 minutes until clear and transparent, and then cooled to room temperature to obtain the eutectic solvent. Lauric acid is used as the HBA, and decanoic acid is used as the HBD, with a molar ratio of 1:2.

[0061] Astaxanthin extraction: Haematococcus pluvialis was mixed with a eutectic solvent at a solid-liquid ratio of 1:20 (w / w). The mixture was stirred gently with a magnetic rod at 200 rpm for 2 hours in the dark at 40°C. The supernatant was then collected by centrifugation at 2800×g for 5 minutes.

[0062] Preparation of dried Haematococcus pluvialis residue: After extracting Haematococcus pluvialis, add water and centrifuge, remove the upper aqueous solution, repeat several times until the aqueous solution is clear, freeze-dry the lower precipitate to obtain dried Haematococcus pluvialis residue (moisture content ≤0.07%).

[0063] Freeze-drying conditions:

[0064] I. Edible Haematococcus pluvialis residue preservation film

[0065] The specific components of the edible Haematococcus pluvialis residue preservation 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] II. Preparation of Edible Haematococcus pluvialis Residue Preservative Film

[0073] Examples 5-8

[0074] Follow the steps below according to the formulation amounts of Examples 1-4 respectively:

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

[0076] (2) At 40°C, dry Haematococcus pluvialis residue and plasticizer were added together to the membrane matrix solution prepared in step (1) and homogenized at 12000 rpm for 2 min.

[0077] (3) Add crosslinking agent, stir at 400 rpm for 30 min at 40℃, and sonicate at 300W for 60 min to obtain plastic wrap liquid.

[0078] (4) Take 20g and place it upside down in a glass dish. Dry it at 40℃ for 10 hours to obtain a plastic wrap.

[0079] Example 9

[0080] According to the formula amount of Example 1, proceed as follows:

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

[0082] (2) At 25°C, dry Haematococcus pluvialis residue and plasticizer were added together to the membrane matrix solution prepared in step (1) and homogenized at 14500 rpm for 1 min.

[0083] (3) Add crosslinking agent, stir at 800 rpm for 20 min at 25℃, and sonicate at 100W for 30 min to obtain plastic wrap liquid.

[0084] (4) Take 30g and place it upside down in a glass dish. Dry it at 45℃ for 10 hours to obtain a plastic wrap.

[0085] Example 10

[0086] According to the formula amount of Example 1, proceed as follows:

[0087] (1) Preparation of membrane matrix solution: Add chitosan to citric acid solution, stir at 300 rpm for 40 min at 80℃, and then cool.

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

[0089] (3) Add crosslinking agent, stir at 200 rpm for 60 min at 40℃, and sonicate at 300 W for 30 min to obtain plastic wrap liquid.

[0090] (4) Take 10g and place it upside down in a glass dish. Dry it at 45℃ for 12 hours to obtain a plastic wrap.

[0091] Comparative Examples 9-16

[0092] Unlike Example 4, the plastic wrap was prepared according to the formulation amounts of Comparative Examples 1 to 8.

[0093] Comparative Example 17

[0094] Unlike Example 4, the homogenization conditions were 15,000 rpm for 2 minutes.

[0095] Comparative Example 18

[0096] Unlike Example 4, the homogenization conditions were 12,000 rpm for 6 minutes.

[0097] Comparative Example 19

[0098] Unlike Example 4, the stirring time was 15 minutes.

[0099] Comparative Example 20

[0100] Unlike Example 4, the stirring time was 65 minutes.

[0101] Experiment 1 Film-forming property observation

[0102] The membranes formed in Examples 5-10 were found to have smooth surfaces, uniform algal residue distribution, and were easily peeled off, exhibiting good physical properties. Comparative Example 9 failed to form a membrane. While Comparative Examples 10-12 had smooth surfaces and were easily peeled off, some exhibited slight uneven distribution of algal residue. In Comparative Example 13, the algal residue was incompatible with pullulan, resulting in a membrane that could not be peeled off after drying, exhibiting a rough surface and high hardness and brittleness. In Comparative Example 14, the addition of algal residue to highly viscoelastic triazine caused a large number of bubbles to form during preparation and drying, affecting membrane formation and making it impossible to peel off, resulting in a membrane surface with loose bubbles. In Comparative Example 15, algal residue agglomerated during drying, leading to uneven composition, but the membrane could be peeled off completely, exhibiting a smooth surface and agglomerated algal residue inside. Comparative Example 16 showed a uniformly distributed composition and could be peeled off completely, but its mechanical properties and antioxidant capacity were significantly lower than in Example 1. Comparative Examples 17-20 had similar surface morphology to Example 5 and could be peeled off completely. Figure 1 As shown, film formation photographs of Example 5 and Comparative Examples 13-15 are 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 Performance Testing

[0104] The mechanical properties of the plastic wraps prepared by the methods of Examples 5-10, Comparative Examples 10-12, and Comparative Examples 16-20 were tested. Specifically, the plastic wrap samples (2cm × 5cm) were fixed between the two metal handles of a tensile testing machine, the initial clamping distance was recorded, and the film was stretched at a uniform speed. Each type of film sample was tested three times. The tensile strength and elongation at break of the film samples were calculated using the following formulas:

[0105] Tensile strength = F / (W×x);

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

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

[0108] In the formula: L is the length of the membrane when it breaks (mm), and L0 is the original length of the membrane (clamp).

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

[0110] Experiment 3 Antioxidant Capacity Test

[0111] The antioxidant capacity of the plastic wraps prepared by the methods of Examples 5-10, Comparative Examples 10-12, and Comparative Examples 16-20 was determined. Specifically, 100 mg of the plastic wrap sample was weighed and added to 2 mL of deionized water. After reacting for 30 min, a membrane solution was obtained. 2 mL of DPPH ethanol solution (0.1 mmol / L) was added to 2 mL of the membrane solution, and the reaction was carried out at room temperature for 60 min. The absorbance of the reaction solution was measured at 517 nm. The scavenging rate of the membrane sample against DPPH free radicals was calculated according to Formula 6.

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

[0113] In the formula: A0 is the blank absorbance, and A is the sample absorbance.

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

[0115] Experiment 4: Determination of the antibacterial ability of plastic wrap

[0116] The antibacterial activity of the preservative films prepared by the methods of Examples 5-10, Comparative Examples 10-12, and Comparative Examples 16-20 was determined. Specifically, the antibacterial activity of the film samples was determined by the agar plate diffusion method. Escherichia coli and Staphylococcus aureus were cultured on LB liquid medium to OD=0.5 (1×10⁸ CFU / mL). After centrifugation, the bacterial solution was diluted to 1×10⁴ CFU / mL, and 100 μL was added to LB solid medium. Three different circular film pieces (1 cm) were attached to the surface of the medium. The medium plates were placed in an incubator at 37°C, and the size of the inhibition zone was observed and the diameter of the inhibition zone was measured. The measurement was repeated three times and the average value was taken.

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

[0118] Experiment 5 Transmittance Detection

[0119] The transmittance of the plastic wraps prepared by the methods of Examples 5-10, Comparative Examples 10-12, and Comparative Examples 16-20 was measured. Specifically, the absorbance of the plastic wraps at wavelengths of 200-800 nm was measured using a UV spectrophotometer. The conversion formula between absorbance and transmittance is A = -logT.

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

[0121]

[0122] As shown in Table 1, compared with Example 5, Comparative Example 10 showed a decrease in mechanical properties and antioxidant capacity, but an increase in light transmittance after reducing the content of dried Haematococcus pluvialis residue. This indicates that an appropriate amount of dried Haematococcus pluvialis residue plays a certain role in maintaining the mechanical properties and antioxidant capacity of the cling film. In Comparative Example 11, replacing citric acid with acetic acid significantly reduced both mechanical properties and antioxidant capacity, indicating that not all acid solutions have the same effect. In Comparative Example 12, although the elongation at break increased without the addition of a crosslinking agent, the tensile strength was the lowest. The crosslinking agent plays a certain role in balancing the elongation at break and tensile strength. In Comparative Example 16, the addition of wet Haematococcus pluvialis residue resulted in a higher water content, increasing the overall water content of the system and leading to a decrease in overall performance. The film-forming properties of Comparative Examples 17-20 were not significantly different from those of Example 5, but the mechanical properties decreased to varying degrees under these preparation conditions. This indicates that within a certain range of homogenization conditions and stirring time, the mechanical properties of the cling film can be improved.

[0123] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions 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 preservation film, characterized in that, It includes 0.4% to 1.6% by mass of dried Haematococcus pluvialis residue, 1% to 4% of plasticizer, 0.2% to 1% of crosslinking agent and membrane matrix solution; The membrane matrix solution comprises 1% to 3% chitosan and 1% to 4% citric acid by mass-volume ratio; The chitosan is chitosan with a degree of deacetylation of 80%; The crosslinking agent includes calcium lactate or calcium chloride; The preparation method of the edible Haematococcus pluvialis residue preservation film is as follows: add the dried Haematococcus pluvialis residue and plasticizer to the citric acid solution containing chitosan according to the formula amount, homogenize, add crosslinking agent and stir evenly, sonicate, and dry to obtain the preservation film. The temperature at which the mixture is stirred evenly is 25~45℃; the stirring speed is 200~800rpm; and the stirring time is 20~60min. The preparation method of the dried Haematococcus pluvialis residue is as follows: Astaxanthin extraction: Haematococcus pluvialis and eutectic solvent were mixed at a solid-liquid ratio of 1:20 w / w. The mixture was stirred gently with a magnetic rod at 200 rpm for 2 hours in the dark at 40°C. The mixture was then centrifuged at 2800×g for 5 minutes, and the supernatant was collected. Preparation of dried Haematococcus pluvialis residue: After extracting Haematococcus pluvialis, add water and centrifuge, remove the upper aqueous solution, repeat several times until the aqueous solution is clear, freeze-dry the lower precipitate to obtain dried Haematococcus pluvialis residue with a water content ≤0.07%.

2. The edible Haematococcus pluvialis residue preservation film according to claim 1, characterized in that, The plasticizers include glycerin, Tween 60, or Tween 80.

3. The edible Haematococcus pluvialis residue preservation film according to claim 2, characterized in that, The plasticizer is glycerin.

4. The edible Haematococcus pluvialis residue preservation film according to claim 1, characterized in that, The crosslinking agent is calcium chloride.

5. The method for preparing the edible Haematococcus pluvialis residue preservation film according to any one of claims 1 to 4, characterized in that, The process involves adding dried Haematococcus pluvialis residue and plasticizer to a citric acid solution containing chitosan according to the formula, homogenizing, adding a crosslinking agent and stirring evenly, ultrasonicating, and drying to obtain a plastic wrap.

6. The preparation method according to claim 5, characterized in that, The method for preparing the citric acid solution containing chitosan includes stirring and dissolving chitosan in the citric acid solution; The temperature for stirring and dissolving is 50~100℃; The stirring speed for dissolving is 300~800 rpm; The stirring and dissolving time is 30-60 minutes.

7. The preparation method according to claim 5, characterized in that, The temperature at which dried Haematococcus pluvialis residue is added is 25~45℃.

8. The preparation method according to claim 5, characterized in that, The homogenization conditions include homogenizing at 10000~14500 rpm for 1~5 min.

9. The preparation method according to claim 8, characterized in that, The homogenization conditions were: homogenization at 12000 rpm for 2 minutes.

10. The preparation method according to claim 5, characterized in that, The power of the ultrasound is 100~300W; The ultrasound session lasted 30 to 60 minutes.

11. The preparation method according to claim 5, characterized in that, The drying temperature is 30~45℃; The drying time is 8 to 24 hours.

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