SBP-PC covalent complex stable Pickering emulsion as well as preparation method and application thereof

Abstract

The invention discloses a Pickering emulsion with a stable SBP-PC covalent complex as well as a preparation method and application of the Pickering emulsion, and belongs to the technical field of functional foods and food processing. According to the invention, the SBP and the PC are used as raw materials, and the Pickering emulsion with stable SBP-PC covalent complex, which is prepared without adding any inorganic material, is high in biological safety; the Pickering emulsion prepared by the method can effectively realize embedding of DHA and EPA in algae oil; the Pickering emulsion disclosed by the invention has relatively high stability and rheological property; the Pickering emulsion is smeared on the surface of the prefabricated dish, and the content of nitrite in the prefabricated dish can be effectively reduced.

Description

Technical Field

[0001] This invention belongs to the field of functional food and food processing technology, and in particular relates to a Pickering emulsion stabilized by an SBP-PC covalent complex, its preparation method and application. Background Technology

[0002] In recent years, the emerging market for prepared meals has been rapidly expanding due to the growing consumer demand for convenient, nutritious, and ready-to-eat products. Prepared meals refer to semi-finished or finished products made from poultry, livestock, agricultural products, and aquatic products with various auxiliary ingredients through pre-processing, requiring only simple heating before consumption. However, food safety remains a pressing challenge during the production, transportation, and storage of prepared meals. Although refrigeration can inhibit the growth of most pathogens and spoilage bacteria, some psychrophilic bacteria can still survive and slowly multiply in refrigerated environments. During their reproduction, these microorganisms promote the production of nitrites from nitrates by nitrate reductase in prepared meals, posing a potential health risk to consumers. Under the acidic conditions of the human stomach, nitrites can react with amines present in food to form nitrosamines, which are considered carcinogenic. With the improvement of living standards, people's requirements for the freshness, safety, and quality of food are gradually increasing; therefore, it is necessary to develop a safe method to reduce the nitrite content of prepared meals.

[0003] Coating corrosion protection, with its outstanding advantages of safety, non-toxicity, ease of operation, and controllable cost, has become a widely used new corrosion protection technology. In recent years, emulsion-based delivery systems for encapsulating and delivering bioactive substances into food matrices have received considerable attention, with many bioactive substances showing improved utilization rates in such systems. Emulsifiers are key components in emulsion formation and stabilization, and are generally classified into exogenous emulsifiers and natural emulsifiers. In food-grade emulsions, natural emulsifiers have greater application potential due to their higher safety profile.

[0004] Pickering emulsions are emulsions stabilized by solid particles. Unlike traditional emulsions, the solid particles in a Pickering emulsion can spontaneously aggregate at the oil-water interface. These solid particles act as a special stabilizer, helping to stabilize the emulsion. However, Pickering emulsion systems are generally unstable and prone to oxidation, stratification, and other phenomena during storage, transportation, and processing, leading to a decline in emulsion quality.

[0005] Therefore, there is an urgent need in the field for a Pickering emulsion that is of stable quality and can solve the problem of high nitrite content in pre-cooked dishes. Summary of the Invention

[0006] To address the above problems, this invention provides a Pickering emulsion stabilized by an SBP-PC covalent complex, its preparation method, and its application.

[0007] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a Pickering emulsion stabilized by an SBP-PC covalent complex, comprising the following steps: adding PC (proanthocyanidins) to an aqueous solution of SBP (sea bass protein), adjusting the pH of the solution and stirring at room temperature, then dialyzing to obtain an aqueous solution of the SBP-PC covalent complex, freeze-drying to obtain the SBP-PC covalent complex, mixing the aqueous solution of the SBP-PC covalent complex with edible oil and then shearing and emulsifying to obtain the Pickering emulsion stabilized by the SBP-PC covalent complex.

[0008] Protein-polyphenol complexes not only offer an effective means of protein functional extension through modification but also serve as a pathway to protect or deliver bioactive polyphenols from degradation. Proanthocyanidins (PCs) are naturally occurring polyphenols widely found in plant sources such as grape seeds, cocoa, and blueberries, exhibiting excellent antioxidant and free radical scavenging capabilities. SBP-PC covalent complexes can be formed through non-covalent and covalent interactions. Alkali treatment is a highly efficient method for forming covalent complexes, and compared to free radical grafting and enzymatic techniques, this method requires no large amounts of chemical reagents or expensive enzyme preparations.

[0009] This invention prepares an SBP-PC covalent complex via an alkali treatment method, and uses this SBP-PC covalent complex as a stabilizer to prepare a Pickering emulsion. The Pickering emulsion exhibits strong stability, effectively protects DHA and EPA in algal oil, and also possesses excellent rheological properties.

[0010] Furthermore, the mass ratio of SBP to PC in the SBP aqueous solution is (5-20):1; the concentration of the SBP aqueous solution is 10 mg / mL.

[0011] Furthermore, the mass ratio of SBP to PC in the SBP aqueous solution is 10:1.

[0012] Furthermore, the pH value is 9.

[0013] Furthermore, the specific procedure for dialysis is as follows: dialysis is performed for 48 hours using an 8000-Da dialysis bag.

[0014] Furthermore, the concentration of the aqueous solution of the SBP-PC covalent complex is 10 mg / mL; the volume ratio of the aqueous solution of the SBP-PC covalent complex to the edible oil is 7:3.

[0015] Furthermore, the shear emulsification speed is 10,000 rpm and the time is 2 min.

[0016] Furthermore, the edible oil is selected from algal oil.

[0017] Docosahexaenoic acid (DHA) is an omega-3 long-chain polyunsaturated fatty acid with numerous health benefits, including reducing the risk of cancer, heart disease, and other chronic illnesses, while promoting neural, visual, and brain development. Eicosapentaenoic acid (EPA) is a 20-carbon carboxylic acid with five cis double bonds, playing a crucial role in neural development and the prevention of chronic diseases. Algal oil, as a natural source of DHA and EPA, possesses unique properties compared to traditional fish oil, such as higher DHA and EPA content, lower heavy metal contamination, and less odor. However, the low water solubility and oxidative stability of algal oil hinder its bioavailability. Emulsions are an important method for encapsulating bioactive compounds, improving their stability and bioavailability.

[0018] Secondly, the present invention provides a Pickering emulsion stabilized by the SBP-PC covalent complex prepared by the above preparation method.

[0019] Thirdly, the present invention provides the application of the Pickering emulsion stabilized by the SBP-PC covalent complex in reducing nitrite in prepared dishes.

[0020] Applying the Pickering emulsion stabilized by the SBP-PC covalent complex prepared in this invention to the surface of pre-cooked vegetables can reduce the nitrite content in the pre-cooked vegetables.

[0021] Compared with the prior art, the present invention has the following advantages and technical effects: This invention uses SBP and PC as raw materials, and the SBP-PC covalent complex prepared without the addition of any inorganic materials produces a stable Pickering emulsion with high biosafety. The Pickering emulsion prepared by this method can effectively encapsulate DHA and EPA in algal oil. The Pickering emulsion has high stability and rheological properties. When the Pickering emulsion is applied to the surface of pre-cooked food, it can effectively reduce the nitrite content in the pre-cooked food. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The results of the determination of total phenol content in SBP and SBP are shown for the SBP-PC covalent complexes prepared in Example 1 and Comparative Example 1. Figure 2 Infrared spectra of the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1; Figure 3 The microstructure diagrams show the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1, respectively. Figure 4 The results of the three-phase contact angle measurement of the SBP-PC covalent composite and SBP prepared in Example 1 and Comparative Example 1 are shown. Figure 5 The results of emulsifying activity and emulsifying stability determination of the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 are shown. Figure 6 CLSM diagrams of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3; Figure 7 The storage modulus and loss modulus of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 are shown as a function of frequency. Figure 8 The viscosity of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 as a function of shear rate is shown in the graph. Figure 9 The results show the encapsulation efficiency of DHA and EPA in the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3. Figure 10 The total nitrite content in the treated *Durvillaea antarctica* (DA) samples was defined as follows: Control was the blank control group; Oil was the surface-coated algal oil; SBP-PC 10∶1 was the surface-coated SBP-PC 10∶1 covalent complex aqueous solution (10 mg / mL); and PE-SBP-PC 10∶1 was the surface-coated SBP-PC 10∶1 covalent complex stabilized Pickering emulsion. Detailed Implementation

[0024] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0025] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0026] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0027] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be obvious to those skilled in the art. This specification and embodiments are merely exemplary.

[0028] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0029] The room temperature in this invention refers to 25±2℃.

[0030] Unless otherwise specified, all materials used in this invention are commercially available products.

[0031] Example 1: Preparation method of SBP-PC covalent complex S1. Dissolve 1g of SBP (sea bass protein) in 100 mL of deionized water, stir at room temperature for 4 h, and then store at 4 ℃ for 12 h to ensure complete hydration of protein molecules, to obtain a 1wt.% SBP solution. S2. PC (proanthocyanidins) was added to four portions of the SBP solution prepared in S1, with the mass ratio of SBP to PC being 20:1, 15:1, 10:1, and 5:1, respectively. The pH of the solution was then adjusted to 9 using NaOH solution (1 mol / L). After stirring at 25 °C for 24 h, the solution was dialyzed for 48 h using an 8000-Da dialysis bag to ensure that the unreacted free PC was completely dialyzed out. The SBP-PC covalent complexes were then obtained by freeze drying and were designated as SBP-PC 5:1, SBP-PC 10:1, SBP-PC 15:1, and SBP-PC 20:1, respectively. Comparative Example 1 PC was added to the SBP solution prepared in S1 in Example 1, wherein the mass ratio of SBP to PC was 10:1 (w / w). After stirring at room temperature for 24 h, the solution was dialyzed with an 8000-Da dialysis bag for 48 h and then freeze-dried to obtain an untreated SBP-PC covalent complex, denoted as SBP-PC 10+1.

[0032] Performance testing (1) Determination of total phenol content 2.5 mL of Folin-Ciocalteu reagent was added to 0.5 mL of SBP solution (1 mg / mL), the aqueous solution of the SBP-PC covalent complex prepared in Example 1 (1 mg / mL), and the aqueous solution of the SBP-PC 10+1 complex prepared in Comparative Example 1 (1 mg / mL), respectively, and reacted in the dark for 5 min. Then, 2 mL of Na2CO3 solution (7.5 wt%) was added to the mixture, and the mixture was reacted in the dark at 25 °C for 2 h. The absorbance at 760 nm was measured using a Synergy H1 multi-functional microplate reader, and the total phenol content in the samples was calculated according to the PC standard curve. The total phenol content in the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 is as follows. Figure 1 As shown.

[0033] from Figure 1As can be seen, the degree of binding between SBP and PC was studied by measuring the total phenol content of all SBP-PC covalent complexes. The total phenol content represents the amount of PC grafted onto SBP; the higher the total phenol content, the higher the grafting amount of SBP and PC. Therefore, the degree of binding between polyphenols and proteins can be directly determined by the increase in the total phenol content in the protein. The total phenol contents of the SBP-PC covalent complexes prepared in Example 1 and Comparative Example 1 were 13.40 μg / mL (SBP-PC 10+1), 20.38 μg / mL (SBP-PC 20∶1), 27.80 μg / mL (SBP-PC 15∶1), 58.59 μg / mL (SBP-PC 10∶1), and 51.24 μg / mL (SBP-PC 5∶1), respectively. Compared with other groups, SBP-PC 10∶1 had the highest total phenol content.

[0034] (2) Fourier transform infrared spectroscopy (FTIR) determination SBP, the SBP-PC covalent complexes prepared in Example 1 and Comparative Example 1 were respectively mixed with KBr at a mass ratio of 1:100, ground uniformly, and the mixtures were compressed into tablets. Fourier transform infrared spectroscopy (FTIR) was used from 500 to 4000 cm⁻¹. -1 FTIR spectra were collected. The infrared spectra of the SBP-PC covalent complexes prepared in Example 1 and Comparative Example 1, and SBP are as follows: Figure 2 As shown. From Figure 2 As can be seen from this, the FTIR spectrum of SBP is in the amide I band (1654.69 cm⁻¹). -1 ), Amide II band (1536.33 cm) -1 ) and amide A band (3292.68 cm) -1 The SBP-PC covalent complex exhibits characteristic peaks. The characteristic peaks of amide I and amide A bands shift to higher wavenumbers, while the characteristic peak of amide II band shifts to lower wavenumbers, indicating that C=O, CN, and NH of SBP participate in the reaction between SBP and PC, confirming the reaction between SBP and PC. Simultaneously, in the SBP-PC 10:1 covalent complex, the shifts of all characteristic peaks change, indicating that the SBP-PC 10:1 covalent complex has the highest PC grafting amount. Furthermore, amide I and amide II bands are characteristic of secondary structure elements. Therefore, compared to SBP, the changes in amide I and amide II bands in the SBP-PC covalent complex indicate a change in the secondary structure after the covalent bonding of SBP and PC.

[0035] (3) Microstructure examination The microstructures of the SBP-PC covalent composites and SBP prepared in Example 1 and Comparative Example 1 were obtained by scanning electron microscopy (SEM). The samples were uniformly spread on a sample stage of double-sided conductive tape, sputtered with gold, and the microstructures were observed using an SEM, with images captured by a computer. The microstructures of the SBP-PC covalent composites and SBP prepared in Example 1 and Comparative Example 1 are shown below. Figure 3 As shown.

[0036] from Figure 3 As can be seen, SBP exhibits smooth, spherical particles, while after binding with polyphenols, it displays a rough, cross-linked structure, possibly due to the network structure formed by molecular interactions between adjacent particles. At low PC concentrations, the covalent complex surface is relatively smooth. As the PC content gradually increases, the covalent complex exhibits a more aggregated, larger network structure with a rougher surface, which is more conducive to stabilizing the Pickering emulsion.

[0037] (4) Three-phase contact angle ( θ ) Measurement The three-phase contact angles of the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 were measured using a droplet shape analyzer. The SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 were each pressed into 2 mm thick tablets, immersed in algal oil for wetting, and then removed. 5 μL of deionized water was squeezed out from a syringe and dropped onto the tablets. The shape of the droplets was recorded using a high-speed camera. The three-phase contact angles of the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 are shown below. Figure 4 As shown.

[0038] pass Figure 4 It can be seen that, compared with SBP alone, the SBP-PC covalent complex improves the wettability of SBP. The three-phase contact angle of the SBP-PC 10:1 covalent complex is close to 90°, which can make the prepared Pickering emulsion more stable.

[0039] (5) Evaluation of emulsifying activity (EAI) and emulsifying stability (ESI) 10.5 mL of SBP solution (10 mg / mL) and the SBP-PC covalent complex (10 mg / mL) prepared in Example 1 and Comparative Example 1 were thoroughly mixed with 4.5 mL of algal oil and homogenized at 10000 rpm for 2 min to obtain an emulsion sample. 50 μL of the emulsion sample was taken. The sample was diluted 200-fold with sodium dodecyl sulfate solution (0.1%, w / v), and the absorbance at 500 nm was measured after 0 min and 30 min. The emulsifying activity and emulsifying stability of the SBP-PC covalent complex and SBP prepared in Example 1 and Comparative Example 1 are as follows: Figure 5As shown.

[0040] pass Figure 5 It can be seen that all SBP-PC covalent complexes exhibit varying degrees of emulsifying properties. With increasing PC content, the EAI and ESI of the covalent complexes initially increase and then decrease. Among them, the SBP-PC 10:1 covalent complex exhibits the highest EAI (40.94 m). 2 The results (g / g) and ESI (422.38 min) indicate that the SBP-PC 10:1 covalent complex has the strongest emulsifying properties.

[0041] Example 2: A method for preparing a Pickering emulsion stabilized by an SBP-PC covalent complex. The SBP-PC covalent complexes (SBP-PC 5∶1, SBP-PC 10∶1, SBP-PC 15∶1, SBP-PC 20∶1, and SBP-PC 10+1) prepared in Example 1 were mixed with deionized water to obtain aqueous phases with a concentration of 10 mg / mL. Algal oil was selected as the oil phase. The aqueous and oil phases were mixed at a volume ratio of 7∶3 and subjected to high-speed shearing (10,000 rpm for 2 min) to obtain a Pickering emulsion stable with the SBP-PC covalent complex.

[0042] Comparative Example 2 The untreated SBP-PC covalent complex (SBP-PC 10+1) prepared in Comparative Example 1 was mixed with deionized water to obtain an aqueous phase with a concentration of 10 mg / mL. Algal oil was selected as the oil phase. The aqueous phase and oil phase were mixed at a volume ratio of 7:3 and subjected to high-speed shearing (10,000 rpm for 2 min) to obtain a stable Pickering emulsion of SBP-PC 10+1.

[0043] Comparative Example 3 SBP was used as an experimental control and mixed with deionized water to obtain an aqueous phase with a concentration of 10 mg / mL. Algal oil was selected as the oil phase. The aqueous and oil phases were mixed at a volume ratio of 7:3 and subjected to high-speed shearing (10,000 rpm for 2 min) to obtain a SBP-stable Pickering emulsion.

[0044] Performance testing (1) Microstructure investigation The microstructure of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 was investigated using laser confocal scanning microscopy (CLSM). After staining the Pickering emulsions with Nile Red (1 mg / mL) and Nile Blue (1 mg / mL), their morphology and structure were observed at excitation wavelengths of 488 nm and 633 nm, respectively. The CLSM results of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 are shown below. Figure 6 As shown.

[0045] pass Figure 6 It can be seen that, due to the uniform spherical shape of all samples, SBP may be firmly adsorbed at the oil-water interface to stabilize droplets. Compared with the SBP-stabilized Pickering emulsion, the particle size of the SBP-PC 10+1 stabilized Pickering emulsion is smaller. Furthermore, with increasing PC content, the particle size of the Pickering emulsion stabilized by the SBP-PC covalent complex bound by the alkali treatment method shows a trend of first decreasing and then increasing, with the smallest and most uniform particle size distribution observed at the SBP-PC 10:1 ratio.

[0046] (2) Investigation of rheological properties The rheological properties of the Pickering emulsions were measured using a rheometer. The Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 were uniformly coated onto 40 mm parallel plates (avoiding air bubbles). The storage modulus (G′) and loss modulus (G″) of the Pickering emulsions were measured at a defined strain using an oscillating frequency scan (0.1 Hz–10 Hz). The changes in storage modulus and loss modulus of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 with frequency are shown below. Figure 7 As shown.

[0047] The Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 all had a greater Gʹ than G′′, which is attributed to the elastic gelation behavior of the emulsions. Specifically, the Pickering emulsions stabilized by SBP-PC 10+1 and those stabilized by the SBP-PC covalent complex had higher Gʹ and G′′ than the SBP-stabilized Pickering emulsion, indicating that the addition of PC improved the rheological properties of the emulsions.

[0048] The Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 were uniformly coated on 40 mm parallel plates (to avoid air bubbles), and the shear rate was set to 0 s. −1 -100 s −1 The viscosity of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 as a function of shear rate is as follows: Figure 8 As shown.

[0049] pass Figure 8 It can be seen that: as the shear rate increases across the entire shear rate range (0-100 s⁻¹), -1 With the increase of [amount], the viscosity of all samples decreased. This indicates that both the SBP-PC covalently modified Pickering emulsion and the SBP-stabilized Pickering emulsion exhibit shear-thinning behavior, classifying them as pseudoplastic fluids. Compared to the SBP-stabilized Pickering emulsion, the viscosity of the SBP-PC covalently modified Pickering emulsion increased. This may be because the PC covalently modified protein particles improve the toughness of the interfacial barrier, thereby weakening oil droplet aggregation and ultimately improving stability.

[0050] (3) Determination of encapsulation efficiency of DHA and EPA Take 1 mL of each of the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3, mix with 1 mL of anhydrous ethanol for demulsification, then add 5 mL of n-hexane, shake for 3 min to extract algal oil, centrifuge at 9000 rpm and 4 °C for 5 min, and transfer 8 mL of the supernatant to a centrifuge tube and dry under a nitrogen stream. After methylation, the DHA and EPA contents in the above Pickering emulsions are determined by gas chromatography-mass spectrometry. The encapsulation rates of DHA and EPA in the Pickering emulsions prepared in Example 2 and Comparative Examples 2-3 are as follows: Figure 9 As shown.

[0051] from Figure 9 As can be seen, compared with the Pickering emulsion stabilized by SBP-PC 10+1, all Pickering emulsions stabilized by the SBP-PC covalent complex exhibit higher DHA and EPA encapsulation efficiencies, and the Pickering emulsion stabilized at the SBP-PC 10:1 ratio shows the highest algal oil encapsulation rate. This indicates that after SBP and an appropriate amount of PC are covalently bound through an alkaline treatment method, more soluble proteins migrate to the surface, resulting in a thicker interfacial film on the droplets, which can effectively stabilize the oil-containing emulsion.

[0052] Application examples The specific steps for preparing pre-cooked meals are as follows: Since the covalent complex-stabilized Pickering emulsion (SBP-PC 10:1) prepared in Example 2 has higher stability and loading capacity for DHA and EPA, this invention prepares the SBP-PC 10:1 covalent complex in Example 1 into an aqueous solution (10 mg / mL). Using this as the aqueous phase and algal oil as the oil phase, the aqueous and oil phases are mixed at a volume ratio of 7:3 and then subjected to high-speed shearing (10,000 rpm, shearing time 2 min) to obtain the SBP-PC 10:1 covalent complex-stabilized Pickering emulsion.

[0053] Seaweed (Durvillaea antarctica, DA) samples were soaked in cold water, blanched for 2 min, and then cooled. Algal oil, an aqueous solution of the SBP-PC 10:1 covalent complex (10 mg / mL), and a Pickering emulsion stabilized with the SBP-PC 10:1 covalent complex were then applied to the surface of the DA samples, respectively. The samples were stored at 4 ℃ for 10 days, and the total nitrite content was measured at 0, 2, 4, 6, 8, and 10 days.

[0054] The specific test procedure is as follows: 10 g of nitrite in the above sample was extracted with saturated borax solution (25 mL, 50 g / L). The mixture was placed in a water bath at 70 ℃ for 15 min. Then, the cooled mixture was mixed with 10 mL of potassium hexacyanoferrate solution (106 g / L) and 10 mL of zinc acetate solution (220 g / L), and the volume was adjusted to 500 mL. After standing for 1 h, the supernatant was filtered through filter paper. The filtrate was mixed with N-1-naphthylethylenediamine hydrochloride solution (0.3%, w / v) and sulfanilamide solution (0.6%, w / v), and the volume was adjusted to 50 mL, wherein the volume ratio of filtrate, N-1-naphthylethylenediamine hydrochloride solution, and sulfanilamide solution was 20:1:1. The absorbance of the mixed solution at 540 nm was measured. Figure 10 The total nitrite content in the DA sample after treatment is given. Control is the blank control group (i.e., no treatment is given to the DA sample), Oil is the surface-coated algal oil, SBP-PC 10∶1 is the surface-coated SBP-PC 10∶1 covalent complex aqueous solution (10 mg / mL), and PE-SBP-PC 10∶1 is the surface-coated SBP-PC 10∶1 covalent complex stabilized Pickering emulsion.

[0055] from Figure 10The results show that the total nitrite content of all samples increased over ten days. DA itself contains nitrate, which is gradually converted to nitrite under bacterial action; the longer the storage time, the higher the conversion rate, and the higher the nitrite content. At 10 days, compared with the blank control group, the nitrite content in the Oil group, SBP-PC 10:1 group, and PE-SBP-PC 10:1 group decreased by 1.1 mg / kg, 3.13 mg / kg, and 4.11 mg / kg, respectively. This may be due to the natural antioxidant capacity of PC, which inhibits bacterial growth and reduces the conversion rate of nitrate to nitrite, thereby lowering the nitrite content.

[0056] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a Pickering emulsion stabilized by an SBP-PC covalent complex, characterized in that, Includes the following steps: Proanthocyanidins were added to an aqueous solution of sea bass protein, the pH of the solution was adjusted, and the solution was stirred at room temperature. Then, the solution was dialyzed to obtain an aqueous solution of sea bass protein-proanthocyanidin covalent complex. After freeze-drying, the sea bass protein-proanthocyanidin covalent complex was obtained. The aqueous solution of the sea bass protein-proanthocyanidin covalent complex was mixed with edible oil and then sheared and emulsified to obtain a Pickering emulsion stable with the SBP-PC covalent complex.

2. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 1, characterized in that, The mass ratio of sea bass protein to proanthocyanidins in the sea bass protein aqueous solution is (5-20):1; the concentration of the sea bass protein aqueous solution is 10 mg / mL.

3. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 2, characterized in that, The mass ratio of sea bass protein to proanthocyanidins in the sea bass protein aqueous solution is 10:

1.

4. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 1, wherein the pH value is 9.

5. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 1, wherein the dialysis operation is as follows: dialysis is performed for 48 h using an 8000-Da dialysis bag.

6. The method for preparing the Pickering emulsion stabilized by the SBP-PC covalent complex according to claim 1, wherein the concentration of the aqueous solution of the sea bass protein-proanthocyanidin covalent complex is 10 mg / mL; and the volume ratio of the aqueous solution of the sea bass protein-proanthocyanidin covalent complex to the edible oil is 7:

3.

7. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 1, wherein the shear emulsification speed is 10000 rpm and the time is 2 min.

8. The method for preparing the SBP-PC covalent complex-stabilized Pickering emulsion according to claim 1, wherein the edible oil is selected from algal oil.

9. A Pickering emulsion stabilized with an SBP-PC covalent complex prepared by the preparation method according to any one of claims 1-8.

10. The application of the SBP-PC covalent complex-stabilized Pickering emulsion of claim 9 in reducing nitrite in prepared dishes.

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