Food-grade ice slurry nucleation-fresh-keeping reinforcing agent as well as preparation method and application thereof

Abstract

The invention discloses a food-grade ice slurry nucleation-fresh-keeping reinforcing agent as well as a preparation method and application of the food-grade ice slurry nucleation-fresh-keeping reinforcing agent. According to the preparation method disclosed by the invention, nano-particles for encapsulating the tea polyphenol are formed under the ultrasonic action by utilizing the electrostatic self-assembly action of the chitosan and the pectin, and the nano-particles are used as a nucleating agent of the ice slurry, so that the degree of supercooling can be reduced, and the fresh-keeping effect of the ice slurry can be enhanced by utilizing the antibacterial and antioxidant activity of the chitosan nano-particles and the slow-release tea polyphenol; in addition, ice melting water containing the nucleating agent can be used for circularly making ice, so that cold energy recovery is realized, and the energy consumption is further reduced.

Description

Technical Field

[0001] This invention relates to the fields of fluid ice nucleating agents and food preservation, specifically to a food-grade fluid ice nucleating-preservation enhancer, its preparation method, and its application. Background Technology

[0002] Flowing ice refers to a homogeneous two-phase mixture of granular ice particles and an aqueous solution. Due to its fine, soft ice crystals and ease of preparation, it is widely used for preserving aquatic products. In deep-sea fishing, seawater can be used to prepare flowing ice, eliminating the need for pre-departure ice preparation and the associated fuel consumption. However, the ice-making process involves supercooling, with seawater exhibiting even higher supercooling. Therefore, ice makers must operate at extremely low evaporation temperatures, resulting in high energy consumption. Adding nucleating agents to the ice-forming solution can effectively reduce supercooling, thereby reducing ice blockage and lowering energy consumption. Traditional nucleating agents are often metals (such as Cu, Al, etc.) or their oxides (CuO, Al2O3, and TiO2), SiO2, ethylene glycol, glycerol, and sodium sulfate. Some researchers have used fine bubbles from natural chitosan powder or chitosan-acetic acid solutions to promote nucleation and reduce supercooling.

[0003] Traditional nucleating agents cannot be used in the field of food preservation due to health risks; food-grade chitosan, when used as a nucleating agent in an insoluble powder state, has almost no preservation effect; and when using bubbles in chitosan solution as nucleation sites, the acetic acid used to dissolve chitosan may affect the quality of aquatic products, and the size and number of bubbles are difficult to control. Summary of the Invention

[0004] The purpose of this invention is to provide a food-grade fluid ice nucleating and preservative enhancer, its preparation method, and its application. This invention utilizes the electrostatic self-assembly of chitosan (CH) and pectin (PE) to form nanoparticles encapsulating tea polyphenols (TP) under ultrasonic treatment. These nanoparticles serve as nucleating agents for fluid ice, not only reducing supercooling but also enhancing the preservation effect of the fluid ice through the antibacterial and antioxidant activities of the chitosan nanoparticles and the slow-release tea polyphenols. Furthermore, by using melted ice water containing this nucleating agent for circulating ice production, cold energy recovery can be achieved, further reducing energy consumption.

[0005] The technical solution of the present invention is as follows:

[0006] A food-grade fluid ice nucleating and preservation enhancer was prepared by the following method:

[0007] Chitosan was dissolved in an acetic acid-water solution to obtain a chitosan solution; pectin was dissolved in pure water to obtain a pectin solution; tea polyphenols were then dissolved in the pectin solution to obtain a pectin-tea polyphenol mixed solution; under room temperature and stirring conditions, the chitosan solution was added dropwise to the pectin-tea polyphenol mixed solution, the pH was adjusted to 4.0-6.0 (preferably pH 5.0), and the mixture was stirred at 600-800 rpm (preferably 700 rpm) for 1-3 hours (preferably 2 hours), followed by ultrasonic treatment at 200-400W (preferably 300W) for 5-15 minutes (preferably 10 minutes) to obtain a suspension containing food-grade fluid ice nucleating-preservative enhancer (denoted as CH / PE-TP NPs);

[0008] Preferably, the volume fraction of acetic acid in the acetic acid-water solution is 1%.

[0009] The preferred concentration of the chitosan solution is 0.1 mg / mL;

[0010] The preferred concentration of the pectin solution is 0.1 mg / mL;

[0011] In the preferred pectin-tea polyphenol mixed solution, the concentration of tea polyphenols is 0.8 mg / mL;

[0012] The preferred volume ratio of chitosan solution to pectin-tea polyphenol mixed solution is 1:5.

[0013] The food-grade fluid ice nucleating-preservative enhancer described in this invention can be used to prepare fluid ice. Specifically, it involves mixing an aqueous solution of 3 wt% edible salt with the suspension containing the food-grade fluid ice nucleating-preservative enhancer obtained above at a volume ratio of 8:2 to 2:8 to prepare fluid ice.

[0014] The resulting liquid ice can be used for food preservation, and the melted ice water can be used for recycling ice making.

[0015] The technical principles of this invention include:

[0016] Nanoparticles prepared by encapsulating tea polyphenols using the electrostatic complexation of chitosan and pectin are used as nucleating agents for fluid ice, thereby reducing supercooling and ice-making energy consumption. The nucleating agent is recycled by refreezing melted ice water, further reducing production costs.

[0017] Chitosan is a natural cationic polysaccharide. Under acidic conditions, the amino groups on its molecular chain become positively charged due to protonation, while the carboxyl groups on the pectin molecular chain become negatively charged due to deprotonation. The two interact electrostatically to form a polyelectrolyte complex that encapsulates tea polyphenols. The complex is then ultrasonically broken down into nanoparticles (CH / PE-TPNPs). CH / PE-TPNPs exhibit good wetting properties with the matrix solution and possess a large specific surface area. During heterogeneous nucleation, they provide the necessary nucleus surface for crystal growth, lowering the nucleation energy barrier and thus promoting nucleation while reducing supercooling.

[0018] In addition to acting as a nucleating agent, chitosan nanoparticles also possess antibacterial properties. Tea polyphenols encapsulated within the nanoparticles can be slowly released during the preservation of aquatic products, continuously exerting antibacterial and antioxidant activities, thereby enhancing the preservation effect of fluid ice. Furthermore, using the melting water from CH / PE-TP NPs-based fluid ice for recycled ice production allows for the reuse of the nucleating agent and the recovery of cold energy.

[0019] The advantages of this invention are:

[0020] 1. Compared with other methods of preparing nanoparticles, the method of preparing nanoparticles by electrostatic self-assembly of chitosan and pectin is simpler, does not require the addition of other chemical cross-linking agents, and is safer for use in food.

[0021] 2. CH / PE-TP NPs, as nucleating agents for fluid ice, can effectively reduce supercooling, thereby reducing the energy consumption required for the ice-making process.

[0022] 3. Because nanoparticles encapsulate tea polyphenols and have a sustained-release effect, tea polyphenols can continue to exert their biological activity. Therefore, the refreezing of melted ice water for food preservation realizes the recycling of nucleating agents and reduces costs. Attached Figure Description

[0023] Figure 1 Flowchart of CH / PE-TP NPs preparation.

[0024] Figure 2 Standard curve of tea polyphenols.

[0025] Figure 3 : The ability to scavenge DPPH free radicals during storage.

[0026] Figure 4 Diagram of the experimental setup for measuring supercooling.

[0027] Figure 5 Effect of different amounts of CH / PE-TP NPs suspension added on subcooling.

[0028] Figure 6The effect of secondary freezing on supercooling. Detailed Implementation

[0029] The present invention is further described below through specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0030] In the following embodiments,

[0031] Chitosan, with a molecular weight of 153.12 kDa and a degree of deacetylation of 84.04%, is obtained through the resource recovery of waste shrimp and crab shells and can be replaced by commercially available chitosan with similar molecular weight and degree of deacetylation.

[0032] Pectin, purchased from Hangzhou Shuangmu Chemical Co., Ltd., with galacturonic acid (dry basis) ≥74%.

[0033] Tea polyphenols, purchased from Shanghai Titan Technology Co., Ltd., 98%.

[0034] Example 1: A method for preparing CH / PE-TP NPs

[0035] Preparation method as follows Figure 1 As shown, CH solution is added dropwise to a pectin solution containing TP, the pH of the mixed solution is adjusted, and then ultrasonic treatment is performed to obtain a nanoparticle suspension. Specifically:

[0036] 1) Preparation of CH / PE-TP NPs: CH was dissolved in 1% acetic acid solution, and PE was dissolved in pure water, both at a concentration of 0.1 mg / mL. TP was then dissolved in pectin solution at a concentration of 0.8 mg / mL, and stirred at 700 rpm for 30 min at room temperature. While stirring at 700 rpm, the CH solution was added dropwise to the PE-TP mixed solution, and V... CH :V PE =1:5, adjust the pH of the suspension to 5.0 with 0.1mol / L sodium hydroxide, and stir at 700rpm for 2h. Treat with ultrasound at 300W for 10min (ultrasound amplitude rod diameter 3mm, ultrasound on and off time 2s).

[0037] 2) Encapsulation efficiency (EE), particle size, and zeta potential determination: 5.0 mL of nanoparticle suspension was centrifuged at 8000 rpm for 5 min. 0.2 mL of the suspension was then taken, and the absorbance of free TP in the supernatant was determined using the Folin-Ciocalteu method. The result was compared with a standard curve (e.g., ...). Figure 2 The amount of free TP was calculated, and the encapsulation efficiency of the nanoparticles was obtained by calculation. The particle size and zeta potential were measured using a laser particle size analyzer. The encapsulation efficiency was 36.21±0.23%, the particle size was 543.93±9.22 nm, and the zeta potential was -21.20±0.37 mV.

[0038] 3) DPPH radical scavenging ability: Freshly prepared CH / PE-TP NPs suspension was stored in a refrigerator with a light source for 12 days, and the DPPH radical scavenging efficiency was measured every 3 days. The suspension was diluted 20 times and mixed with 0.4 mM DPPH solution, reacted at 25℃ for 30 min, and the absorbance was measured at 517 nm to calculate the DPPH radical scavenging ability. A TP solution of the same concentration was used as a control during the experiment. The results are as follows: Figure 3 As shown.

[0039] Example 2: Experiment on the reduction of undercooling in the production of fluid ice using CH / PE-TP NPs as nucleating agents

[0040] Experimental apparatus for measuring supercooling, such as Figure 4 As shown, it consists of a low-temperature constant temperature bath, a thermocouple, a data collector, and a laptop computer.

[0041] 1) Effect of CH / PE-TP NPs addition on supercooling: A solution containing 3% edible salt was mixed with CH / PE-TP NPs suspension at volume ratios (SW:NPs) of 8:2, 6:4, 4:6, and 2:8, respectively. 10 mL of each mixture was placed in a low-temperature constant-temperature bath (temperature maintained at -14±0.5℃), and a thermocouple was placed 4 cm below the liquid surface. Data were collected every 5 seconds. The results are shown below. Figure 5 .

[0042] 2) Effect of secondary freezing on supercooling: Flow ice was prepared by mixing SW:NPs at a volume ratio of 6:4, resulting in an ice-to-water ratio of 3:4. This was used for the preservation of large yellow croaker for 10 days, with the melted ice water replaced every 48 hours. Since TP was continuously released into the solution, the melted ice water was used for secondary freezing for preservation, and the supercooling was measured simultaneously. The results are as follows: Figure 6 As shown.

[0043] 3) Subcooling, freezing temperature, and total freezing time: such as Figure 5 , Figure 6 The theoretical time-temperature curves are shown in Table 1, where T0 is the initial temperature (25℃), T1 is the nucleation temperature, ΔT is the supercooling, and Δt is the total freezing time. Table 1 summarizes the T1, ΔT, and Δt values ​​for different NP addition ratios and secondary freezing.

[0044] Table 1 Summary of nucleation temperature, supercooling, and total freezing time

[0045]

Claims

1. A food-grade fluid ice nucleation-preservation enhancer, characterized in that: Prepared as follows: Dissolving chitosan in an acetic acid-water solution to obtain a chitosan solution; dissolving pectin in pure water to obtain a pectin solution; and dissolving tea polyphenols in the pectin solution to obtain a pectin-tea polyphenols mixed solution; At room temperature and under stirring conditions, the chitosan solution is added drop by drop into the pectin-tea polyphenol mixed solution, the pH is adjusted to 4.0-6.0, and stirred at 600-800 rpm for 1-3 hours, followed by ultrasonic treatment at 200-400 W for 5-15 minutes to obtain a suspension containing a food-grade fluidized ice nucleation-preservation enhancer.

2. The food-grade fluid ice nucleation-preservation enhancer according to claim 1, characterized in that: In the acetic acid-water solution, the volume fraction of acetic acid is 1%.

3. The food-grade fluid ice nucleation-preservation enhancer according to claim 1, characterized in that: The concentration of chitosan solution was 0.1 mg / mL.

4. The food-grade fluidized ice nucleation-preservation enhancer according to claim 1, characterized in that: The concentration of pectin solution was 0.1 mg / mL.

5. The food-grade fluid ice nucleation-preservation enhancer according to claim 1, characterized in that: In the pectin-tea polyphenols mixed solution, the concentration of tea polyphenols is 0.8 mg / mL.

6. The food-grade fluid ice nucleation-preservation enhancer according to claim 1, characterized in that: The volume ratio of chitosan solution to pectin-tea polyphenols mixed solution is 1:

5.

7. Use of the food-grade slurry ice nucleation-preservation enhancer according to claim 1 in the preparation of slurry ice.

8. The use according to claim 7, characterized in that The slurry ice is prepared by mixing a 3wt% edible salt aqueous solution and a suspension containing a food-grade slurry ice nucleation-preservation enhancer in a volume ratio of 8:2 to 2:

8.

9. The use according to claim 7, characterized in that The melted ice water after the slurry ice is used for food preservation is continuously used for circulating ice making.

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