Zein-based cinnamyl aldehyde-curcumin composite nanoparticles as well as preparation method and application thereof

Abstract

The invention relates to zein-based cinnamyl aldehyde-curcumin composite nanoparticles as well as a preparation method and application thereof, and belongs to the technical field of food preservation. The technical problems that bag expansion, browning and the like easily occur in the storage process of the pickled Chinese cabbages are solved. According to the zein-based cinnamyl aldehyde-curcumin composite nanoparticles disclosed by the invention, zein is taken as a nano carrier, cinnamyl aldehyde and curcumin are taken as loaded drugs, and sodium alginate is taken as a stabilizer. The zein-based cinnamyl aldehyde-curcumin composite nanoparticles can effectively inhibit the growth of aerogenic bacteria-Delftia acidovorans and Lactobacillus buchneri in the storage process of pickled Chinese cabbages, and can synchronously achieve the triple effects of enhancing the antioxidant activity of the pickled Chinese cabbages, improving the color and luster of the pickled Chinese cabbages and maintaining nutritional ingredients; the quality deterioration in the storage process is effectively delayed.

Description

Technical Field

[0001] The present invention belongs to the technical field of food preservation, and particularly relates to a zein-based cinnamaldehyde-curcumin composite nanoparticle, a preparation method thereof and an application thereof, and more particularly relates to the application of the zein-based cinnamaldehyde-curcumin composite nanoparticle in pickled Chinese cabbage preservation. Background Art

[0002] As a fermented vegetable product with a long history in Northeast China, pickled Chinese cabbage is deeply loved by the general public in China because of its delicious taste and rich nutrition. At present, most of the pickled Chinese cabbages sold on the market are whole pickled Chinese cabbages, shredded pickled Chinese cabbages, etc. packed in vacuum. However, during the storage of pickled Chinese cabbage in Northeast China, quality problems such as bloating, browning, softening, excessive acidification, and peculiar smell often occur. In particular, the problems of bloating and browning caused by microbial gas production and the oxidation of phenolic substances catalyzed by polyphenol oxidase are relatively common, seriously affecting the selling value of pickled Chinese cabbage. In recent years, the main method for most enterprises to prevent the spoilage of pickled Chinese cabbage is to add chemical preservatives to ensure its quality. However, long-term consumption of foods containing chemical preservatives does not meet the current consumers' pursuit of green and healthy products. Therefore, while ensuring the quality of pickled Chinese cabbage, how to use green and healthy preservatives to extend its storage period has become a research hotspot in the field of food safety at home and abroad.

[0003] Curcumin (CUR) is a lipophilic polyphenol extracted from the rhizomes of turmeric plants and has a variety of biological activities. However, the poor solubility and stability of curcumin have hindered its application in the food field.

[0004] Cinnamaldehyde (CIN) is a natural essential oil extracted from cinnamon and has biological properties such as anti-inflammatory, anti-tumor, and hypoglycemic effects. However, the characteristics of poor solubility in water and easy volatility of cinnamaldehyde limit its application.

[0005] In recent years, nanocarriers have shown broad application prospects in the field of food preservation. Zein, as a nanocarrier, has film-forming properties, self-assembly properties, gel properties, good biocompatibility and biodegradability, and has been widely used in the food industry. Summary of the Invention

[0006] In order to solve the technical problems such as easy bloating and browning during the storage of pickled Chinese cabbage, the present invention provides a zein-based cinnamaldehyde-curcumin composite nanoparticle, a preparation method thereof and an application thereof. The composite nanoparticle uses zein as a nanocarrier to carry curcumin and cinnamaldehyde, improving the solubility and stability of curcumin and cinnamaldehyde in the storage environment of pickled Chinese cabbage, and further enhancing the antibacterial and color protection effects of the composite nanoparticle. The test results show that the composite nanoparticle can effectively inhibit the growth of gas-producing bacteria Delftia acidovorans and Lactobacillus parabuchneri during the storage of pickled Chinese cabbage, and has good antioxidant effects, thereby improving the taste and commercial value of pickled Chinese cabbage.

[0007] To achieve the above object, the present invention provides the following technical solutions:

[0008] In a first aspect, the present invention provides a zein-based cinnamaldehyde-curcumin composite nanoparticle, using zein as a nanocarrier, cinnamaldehyde and curcumin as drug carriers, and sodium alginate (SA) as a stabilizer.

[0009] Preferably, the mass ratio of curcumin, cinnamaldehyde to zein is 1-8:1-8:15, and the mass ratio of zein to sodium alginate is 10:1-1:10;

[0010] More preferably, the mass ratio of curcumin to cinnamaldehyde is 1:1.

[0011] In a second aspect, the present invention provides a method for preparing a zein-based cinnamaldehyde-curcumin composite nanoparticle, comprising the following steps:

[0012] While dropping a zein solution, a cinnamaldehyde solution and a curcumin solution into an aqueous sodium alginate solution drop by drop, after mixing evenly, dialyzing to remove the organic solvent to obtain a zein-based cinnamaldehyde-curcumin composite nanoparticle;

[0013] The solvents of the zein solution, the cinnamaldehyde solution and the curcumin solution are ethanol aqueous solutions.

[0014] Preferably, the water in the aqueous sodium alginate solution is ultrapure water.

[0015] Preferably, the concentration of the aqueous sodium alginate solution is 1-5 mg / mL.

[0016] Preferably, the concentration of the zein solution is 1-5 mg / mL.

[0017] Preferably, the concentrations of the curcumin solution and the cinnamaldehyde solution are independently 200-500 μg / mL. More preferably, the concentrations of the curcumin solution and the cinnamaldehyde solution are both 400 μg / mL.

[0018] Preferably, the method of mixing evenly is magnetic stirring for 20-50 min. More preferably, the method of mixing evenly is magnetic stirring for 30 min.

[0019] Preferably, the dialysis is carried out with a dialysis bag of 3500 Da for 12-24 h.

[0020] Preferably, the concentration of the ethanol aqueous solution is 50%-95% (v / v). More preferably, the concentration of the ethanol aqueous solution is 90% (v / v).

[0021] Thirdly, the present invention also provides the application of the zein-based cinnamaldehyde-curcumin composite nanoparticles in pickled cabbage preservation.

[0022] Preferably, after the fermentation of pickled cabbage is completed, the pickled cabbage is washed in water for 4 - 5 minutes, the zein-based cinnamaldehyde-curcumin composite preservation nanoparticles are added, and then it is vacuum-packed and stored.

[0023] More preferably, the addition amount of the zein-based cinnamaldehyde-curcumin composite preservation nanoparticles is 0.01 - 0.04 g / kg.

[0024] More preferably, the fresh Chinese cabbage is washed, blanched and then sun-dried, put into a pickling container, brine with a concentration of 3.5 wt% is added, sealed and fermented. After the fermentation is completed, the pickled cabbage after fermentation is obtained.

[0025] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0026] 1. The present invention designs and develops for the first time a pickled cabbage preservative for the storage period of pickled cabbage, namely, zein-based cinnamaldehyde-curcumin composite nanoparticles;

[0027] 2. The zein-based cinnamaldehyde-curcumin composite nanoparticles provided by the present invention can effectively inhibit the growth of gas-producing bacteria, Delftia acidovorans and Lactobacillus parabuchneri, during the storage of pickled cabbage, and solve the problem of bag swelling during the storage of pickled cabbage;

[0028] 3. The zein-based cinnamaldehyde-curcumin composite nanoparticles provided by the present invention can simultaneously achieve three functions of enhancing the antioxidant activity of pickled cabbage, improving the color of pickled cabbage and maintaining nutritional components, and effectively delay the quality deterioration during storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0030] Figure 1 It is a differential scanning calorimetry analysis chart of the zein-based cinnamaldehyde-curcumin composite nanoparticles and various control samples provided in Example 2 of the present invention.

[0031] Figure 2 It is a comparison chart of the antioxidant activities of the zein-based cinnamaldehyde-curcumin composite nanoparticles and various control samples provided in Example 2 of the present invention. Among them, A is the scavenging ability of DPPH·, and B is the scavenging ability of ABTS· + scavenging ability.

[0032] Figure 3 X-ray diffraction analysis of zein-based cinnamaldehyde-curcumin composite nanoparticles and various control samples provided in Example 2 of the present invention; wherein, A is the X-ray diffraction analysis of Zein, SA and CUR, and B is the X-ray diffraction analysis of ZS@CIN NPs, ZS@CUR NPs, ZS@CIN-CUR NPs and the physical mixture of Zein / SA / CUR.

[0033] Figure 4 Ultraviolet absorption spectrum analysis of zein-based cinnamaldehyde-curcumin composite nanoparticles and various control samples provided in Example 2 of the present invention.

[0034] Figure 5 Fourier transform infrared spectroscopy analysis of zein-based cinnamaldehyde-curcumin composite nanoparticles and various control samples provided in Example 2 of the present invention.

[0035] Figure 6 Puffing situation of pickled Chinese cabbage under different treatments in Example 4 of the present invention; wherein, A is the blank control group, and B is the group added with zein-based cinnamaldehyde-curcumin composite nanoparticles.

[0036] Figure 7 Change of chromaticity value during the storage of pickled Chinese cabbage in Example 5 of the present invention; wherein, A is the change of chromaticity a* value of pickled Chinese cabbage leaves during storage; B is the change of chromaticity b* value of pickled Chinese cabbage leaves during storage; C is the change of chromaticity L* value of pickled Chinese cabbage leaves during storage; in the figure, a, b, c represent the significance marked by the letter method.

[0037] Figure 8 Quality of pickled Chinese cabbage under different treatments in Example 5 of the present invention; wherein, A is the blank control group, B is the group added with blank nanoparticles, and C is the group added with zein-based cinnamaldehyde-curcumin composite nanoparticles.

[0038] Figure 9 Change of total acid content during the storage of pickled Chinese cabbage provided in Example 5 of the present invention; in the figure, a, b, c represent the significance marked by the letter method.

[0039] Figure 10 Change of soluble protein content during the storage of pickled Chinese cabbage provided in Example 5 of the present invention; in the figure, a, b, c represent the significance marked by the letter method.

[0040] Figure 11 Change of amino acid nitrogen content during the storage of pickled Chinese cabbage provided in Example 5 of the present invention; in the figure, a, b, c represent the significance marked by the letter method.

[0041] Figure 12pH change during the storage of pickled cabbage provided in Example 5 of the present invention; in the figure, a, b, and c represent the significance marked by the letter method.

[0042] Figure 13 Change in ascorbic acid content during the storage of pickled cabbage provided in Example 5 of the present invention; in the figure, a, b, and c represent the significance marked by the letter method.

[0043] Figure 14 Change in nitrite content during the storage of pickled cabbage provided in Example 5 of the present invention; in the figure, a, b, and c represent the significance marked by the letter method. Detailed implementation manners

[0044] To further understand the present invention, the preferred implementation schemes of the present invention are described below. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, rather than limiting the claims of the present invention.

[0045] The zein-based cinnamaldehyde-curcumin composite nanoparticles of the present invention use zein as a nanocarrier, cinnamaldehyde and curcumin as drug carriers, and sodium alginate as a stabilizer.

[0046] For the zein-based cinnamaldehyde-curcumin composite nanoparticles of the present invention, zein and sodium alginate form nanoparticles, and curcumin and cinnamaldehyde are encapsulated in the nanoparticles. These nanoparticles can successfully embed water-insoluble substances (curcumin, cinnamaldehyde), improve the solubility of curcumin and cinnamaldehyde in water, and can also improve the antioxidant activity of free compounds or single components.

[0047] In some embodiments, preferably, the mass ratio of curcumin, cinnamaldehyde to zein is 1:15 - 8:15, and the mass ratio of zein to sodium alginate is 10:1 - 1:10.

[0048] The preparation method of the zein-based cinnamaldehyde-curcumin composite nanoparticles of the present invention includes the following steps:

[0049] S1. Prepare a zein solution

[0050] Dissolve zein in an ethanol aqueous solution to obtain a zein solution;

[0051] S2. Prepare a sodium alginate solution:

[0052] Dissolve sodium alginate in water to make an aqueous sodium alginate solution;

[0053] S3. Prepare a cinnamaldehyde and curcumin solution:

[0054] Dissolve cinnamaldehyde and curcumin in aqueous ethanol solutions respectively to obtain a cinnamaldehyde solution and a curcumin solution;

[0055] S4. Dropwise add the zein solution, cinnamaldehyde solution and curcumin solution into the sodium alginate aqueous solution simultaneously. After mixing evenly, dialyze to remove the organic solvent (i.e., ethanol) to obtain zein-based cinnamaldehyde-curcumin composite nanoparticles.

[0056] In some embodiments, in step S1, the concentration of the aqueous ethanol solution is 50% - 95%, such as 50%, 60%, 70%, 80%, 90% (v / v). And dissolve zein in the aqueous ethanol solution by magnetic stirring for 2 h. The concentration of the zein solution is 1 - 5 mg / mL.

[0057] In some embodiments, in step S2, the concentration of the sodium alginate aqueous solution is 1 - 5 mg / mL, such as 1 mg / mL, 2 mg / mL, 3 mg / mL, 4 mg / mL, 5 mg / mL. The water is ultrapure water. The greater the concentration of the sodium alginate aqueous solution, the smaller and more stable the particle size of the zein-based cinnamaldehyde-curcumin composite nanoparticles.

[0058] For example, when the mass ratio of Zein:SA is 5:1, the average particle size of the nanoparticles is 590.9 nm. When the mass ratio of Zein:SA is 1:5, the average particle size of the nanoparticles is about 134.8 nm. The average PDI of the nanoparticles is in the range of 0.241 - 0.316, that is, the particle size distribution is relatively narrow.

[0059] In some embodiments, in step S3, the concentration of the aqueous ethanol solution is 50% - 95%, such as 50%, 60%, 70%, 80%, 90% (v / v). The concentrations of both the curcumin solution and the cinnamaldehyde solution are 200 - 500 μg / mL, such as 200 μg / mL, 300 μg / mL, 400 μg / mL, 500 μg / mL. As the feeding concentrations of the curcumin solution and the cinnamaldehyde solution increase, the nanoparticle yield gradually decreases, the loading efficiency gradually decreases, and the polymer dispersity index increases. Preferably, the concentrations of both the curcumin solution and the cinnamaldehyde solution are 400 μg / mL.

[0060] In some embodiments, in step S4, the way of mixing evenly is magnetic stirring for 20 - 50 min, such as 20 min, 30 min, 40 min, 50 min. Dialysis is carried out with a dialysis bag of 3500 Da for 12 - 24 h.

[0061] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to examples.

[0062] The following examples are used to illustrate the present invention, but not to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. The equipment used in the examples mainly includes a high-speed centrifuge; an Alpha1-4LDplus freeze dryer; a Q2000 differential scanning calorimeter; a DZ400 / 2SB vacuum packaging machine; a DF-101S collecting type constant temperature heating magnetic stirrer.

[0063] Example 1 Preparation of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0064] Dissolve zein in an ethanol aqueous solution of 90% (v / v), and magnetically stir for 2 h to fully dissolve zein, obtaining a zein solution with a concentration of 2.5 mg / mL. Dissolve sodium alginate in ultrapure water, obtaining a sodium alginate aqueous solution with a concentration of 1.5 mg / mL. Dissolve cinnamaldehyde and curcumin in an ethanol aqueous solution of 90% (v / v) respectively, obtaining a cinnamaldehyde solution with a concentration of 400 μg / mL and a curcumin solution with a concentration of 400 μg / mL. According to the mass ratio of curcumin, cinnamaldehyde to zein being 2.5:2.5:15, and the mass ratio of zein to sodium alginate being 1:5, simultaneously dropwise add the zein solution, cinnamaldehyde solution and curcumin solution into the sodium alginate aqueous solution. After magnetically stirring for 30 min, dialyze through a dialysis bag with a molecular weight cut-off of 3500 Da for 24 h to remove the organic solvent, obtaining zein-based cinnamaldehyde-curcumin composite nanoparticles.

[0065] Example 2 Characterization of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0066] 1. Differential scanning calorimetry (DSC) analysis of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0067] Differential scanning calorimetry, as a thermal analysis technique, studies the melting point, boiling point, and thermal stability of a sample by measuring the difference in heat flow between the sample and various reference samples under the same heating or cooling conditions. The thermal properties of zein / sodium alginate / curcumin physical mixture (Zein / SA / CUR physical mixture), zein-based cinnamaldehyde-curcumin composite nanoparticles (ZS@CIN-CUR NPs), zein-curcumin composite nanoparticles (ZS@CUR NPs), zein-cinnamaldehyde composite nanoparticles (ZS@CIN NPs), blank nanoparticles (ZS NPs), curcumin (CUR), sodium alginate (SA), and zein were detected using DSC. The detection method was as follows: Approximately 5 mg of the sample was weighed and sealed in a standard aluminum pan. The lid was fixed with a syringe needle to exclude the interference of moisture. The sample was heated from 30 °C to 200 °C at a heating rate of 10 °C / min, while nitrogen gas was continuously blown at a rate of 20 mL / min for drying. The detection results are as Figure 1 shown.

[0068] As can be seen Figure 1 from the DSC curve of CUR, a sharp melting peak appeared at around 183.03 °C, which was attributed to the melting of CUR crystals. For the Zein / SA / CUR physical mixture, this endothermic peak was detected, and neither Zein nor SA showed any sharp melting peaks, indicating that their amorphous nature was very suitable as the wall material of nanoparticles. ZS NPs exhibited a broad endothermic peak near 117.87 °C. However, only the endothermic peak of ZS NPs was detected in ZS@CUR NPs and ZS@CIN-CUR NPs. Compared with free CUR, the melting points of ZS@CUR NPs and ZS@CIN-CUR NPs disappeared, indicating that CUR was completely embedded in the cavities of the nanoparticles, in an amorphous state and with improved thermal stability. Only the broad peak of ZS NPs was observed in ZS@CIN-CUR NPs and ZS@CIN NPs, indicating that CIN was completely embedded in the cavities of the nanoparticles.

[0069] 2. Determination of DPPH radical scavenging activity of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0070] The DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability is a commonly used method for evaluating antioxidant activity in vitro. The stronger the scavenging ability, the higher the antioxidant activity of the sample. Mix 2 mL of an ethanol solution containing 100 mM DPPH with an equal volume of ethanol solutions of ascorbic acid, cinnamaldehyde (CIN), curcumin (CUR), blank nanoparticles (ZS NPs), zein-cinnamaldehyde composite nanoparticles (ZS@CIN NPs), zein-based cinnamaldehyde-curcumin composite nanoparticles (ZS@CIN-CUR NPs), and zein-curcumin composite nanoparticles (ZS@CUR NPs) at different concentrations (5 - 50 μg / mL). After incubating for 30 min at room temperature in the dark, measure the absorbance of the reaction solution at 517 nm. The DPPH scavenging rate is calculated using the following formula:

[0071] ;

[0072] where, is the scavenging rate, is the absorbance of the control reaction, is the absorbance of the test sample. The results are shown in Figure 2 as shown in A.

[0073] From Figure 2 as shown in A, when the concentration is 50 μg / mL, the DPPH radical scavenging activity value of ZS@CIN-CUR NPs is 81.16%. Compared with ZS@CIN NPs and ZS@CUR NPs, ZS@CIN-CUR NPs have the best antioxidant activity and are significantly higher than ZS NPs.

[0074] 3. ABTS· + scavenging activity determination of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0075] The ABTS (2,2'-azino-bis-3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging ability is a widely used method for evaluating antioxidant activity in vitro, mainly used to evaluate the total antioxidant capacity of compounds, extracts, or biological samples. Mix equal volumes of 7 mmol / L ABTS solution and 4.9 mmol / L potassium persulfate solution, place in the dark for 12 - 16 h, and dilute with PBS (10 mM, pH 7.4) to an absorbance of 0.80 (±0.02) cm -1 at 734 nm and stabilize at room temperature to obtain ABTS· +Solutions. In the dark at room temperature, 1 mL of ethanol solutions of ascorbic acid (at different concentrations of 5 - 50 μg / mL), cinnamaldehyde (CIN), curcumin (CUR), blank nanoparticles (ZS NPs), zein-cinnamaldehyde composite nanoparticles (ZS@CIN NPs), zein-based cinnamaldehyde-curcumin composite nanoparticles (ZS@CIN-CUR NPs), and zein-curcumin composite nanoparticles (ZS@CUR NPs) were separately reacted with 4 mL of ABTS· + solution. The reaction time was 6 min, and the absorbance was measured at a wavelength of 734 nm using a UV-visible spectrophotometer. Phosphate buffer solution and absolute ethanol were used as blank control groups respectively. ABTS· + The ABTS·

[0076]

[0077] The scavenging rate formula is as follows: where is the scavenging rate, is the absorbance of the control reaction, and is the absorbance of the test sample. The results are shown in Figure 2 B as follows.

[0078] As can be seen from Figure 2 B, when the concentration is 50 μg / mL, compared with other test substances, the ABTS· + scavenging activity value of ZS@CIN-CUR NPs is the highest, reaching 90.19%. This indicates that compared with ZS@CIN NPs and ZS@CUR NPs, the antioxidant activity of ZS@CIN-CUR NPs is the best and significantly higher than that of ZS NPs (P < 0.05).

[0079] 4. X-ray diffraction analysis of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0080] X-ray diffraction analysis is used to analyze the crystal structure of nanoparticles, determine their phase composition, and help understand the properties and stability of nanoparticles. Using the CuKα radiation source (λ = 0.154 nm) of an X-ray diffractometer and a scanning rate of 10° / min from 10° to 60°, the X-ray diffraction patterns of ZS@CIN-CUR NPs, ZS@CIN NPs, ZS@CUR NPs, Zein / SA / CUR physical mixture, Zein, SA, and CUR were measured. The results are shown in Figure 3 A and B as follows.

[0081] As can be seen from Figure 3It can be seen that pure CUR has sharp diffraction peaks, indicating that free CUR exists in a highly crystalline form. Due to the relatively low content of curcumin in the Zein / SA / CUR physical mixture, the intensity of its characteristic peaks is weak. In contrast, no characteristic diffraction peaks of CUR are seen in the diffraction patterns of ZS@CURNPs and ZS@CIN-CUR NPs, indicating that it is in an amorphous state in the nanoparticles and has been successfully encapsulated in the nanoparticles. The diffraction peaks of ZS@CUR NPs and ZS@CIN-CUR NPs at the previous angles are further reduced or even disappear, indicating that the intermolecular interactions between the various components have changed the physical state during the formation of the composite nanoparticles.

[0082] 5. UV-Visible Absorption Spectroscopy Analysis of Zein-Based Cinnamaldehyde-Curcumin Composite Nanoparticles

[0083] Dissolve zein-curcumin composite nanoparticles (ZS@CUR NPs), curcumin (CUR), cinnamaldehyde (CIN), and zein in 85% ethanol respectively at room temperature. Using 85% (v / v) ethanol as the reference solution, scan the UV spectrum in the range of 200 - 800 nm.

[0084] The results are as Figure 4 shown. Curcumin shows a characteristic absorption peak at 425 nm, and cinnamaldehyde shows a characteristic absorption peak at 285 nm. In the UV absorption spectrum of ZS@CIN-CUR NPs, the absorption peaks at 285 nm and 425 nm are the characteristic peaks of cinnamaldehyde and curcumin, indicating that curcumin and cinnamaldehyde have been successfully loaded onto Zein.

[0085] 6. Fourier Transform Infrared Spectroscopy (FTIR) Analysis of Zein-Based Cinnamaldehyde-Curcumin Composite Nanoparticles

[0086] Use FTIR to measure the chemical structures of blank nanoparticles (ZS NPs), zein-based cinnamaldehyde-curcumin composite nanoparticles (ZS@CIN-CUR NPs), zein-curcumin composite nanoparticles (ZS@CUR NPs), zein-cinnamaldehyde composite nanoparticles (ZS@CIN NPs), curcumin (CUR), cinnamaldehyde (CIN), sodium alginate (SA), and zein (Zein). Method: Weigh 2 - 3 mg of the sample and mix it evenly with potassium bromide at a mass ratio of 1:100. Grind it evenly with an agate mortar under the irradiation of an infrared lamp. After sample preparation, detect it by FTIR.

[0087] As can be seen from Figure 5 it, Zein has two typical amide peaks, namely amide I (1655 cm -1 )(1651 cm -1) and amide II (1544 cm -1 ) representing N-H bending. However, after the formation of ZS NPs, amide I and amide II are shifted to 1614 cm -1 and 1542 cm -1 respectively, which may be caused by electrostatic interactions. In addition, the peak positions of hydrogen bonds in the spectra of Zein, SA, and ZS NPs are redshifted from 3435 cm -1 to 3421 cm -1 , which may be due to the hydrogen bond interaction between the amide group of zein and the hydroxyl group of sodium alginate. The zein peak at 2931 cm -1 represents the hydrophobic stretching vibration of –CH2, and this peak is shifted to 2958 cm -1 in the ZS@CUR NPs sample. This indicates the existence of hydrophobic interaction between zein and curcumin. Therefore, the hydrophobic properties of zein and curcumin make hydrophobic interaction another driving force for the formation of ZS@CUR NPs and ZS@CIN-CUR NPs. The infrared spectra of ZS@CIN-CUR NPs are generally consistent with those of ZS NPs. Special peaks such as the stretching vibrations of aromatic rings and inter-ring chains in the CUR spectrum (1449 cm -1 , 1126 cm -1 ), and the characteristic peak of the stretching vibration region of the carbonyl group in the CIN spectrum (1678 cm -1 ) are not observed in the spectrum of ZS@CIN NPs, indicating that these characteristic peaks are masked, and it is inferred that curcumin and cinnamaldehyde are encapsulated in the nanoparticles.

[0088] Example 3 Application of Zein-based Cinnamaldehyde-Curcumin Composite Nanoparticles

[0089] After washing, blanching, and drying fresh Chinese cabbages, they are put into a pickling container, and brine with a concentration of 3.5 wt% is added, and then sealed for fermentation. The pickled Chinese cabbages after fermentation are washed in water for 4 - 5 min, Zein-based cinnamaldehyde-curcumin composite nanoparticles (the addition amount is 0.04 g / kg) are added, and then vacuum-packed and stored.

[0090] Example 4 Antibacterial Effect of Zein-based Cinnamaldehyde-Curcumin Composite Nanoparticles on Pickled Chinese Cabbages during Storage

[0091] 1. Determination of the Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) of Aerogenic Bacteria in Pickled Chinese Cabbages

[0092] (1)Determination of the minimum inhibitory concentration (MIC) of gas-producing bacteria: ZS@CIN-CUR NPs, ZS@CIN NPs, ZS@CUR NPs, CUR solution (solvent 90% (v / v) ethanol), and CIN solution (solvent 90% (v / v) ethanol) were serially diluted two-fold with MRS liquid medium to the final concentrations of ZS@CIN-CUR NPs (calculated as curcumin) being 10.25 - 82.00 μg / mL, ZS@CIN NPs being 34 - 272 μg / mL, ZS@CUR NPs being 38.75 - 310.00 μg / mL, and the concentrations of CUR solution and CIN solution being 16.00 - 1024.00 μg / mL to obtain the assay media. 100 μL of the bacterial suspension and each of the above assay media were pipetted into a 24-well plate, with 6 replicates for each concentration, and covered. Pure MRS liquid medium was used as the blank control group, and MRS liquid medium with only the bacterial suspension added was used as the negative control. The cultures were shaken in an incubator at 37 °C and 200 r / min for 24 h. The turbidity of the liquid was observed, and the lowest material concentration at which the solution in the well did not become turbid compared to the blank control group was the MIC value.

[0093] (2)Determination of the minimum bactericidal concentration (MBC): 100 μL was taken from the solution for MIC value determination above and spread on MRS agar medium, and cultured at 37 °C for 36 h. The lowest concentration at which the colonies grown on the MRS agar medium were less than 5 μg / mL was the MBC value.

[0094] The results showed that the minimum inhibitory concentration (MIC) of ZS@CUR NPs against SK1 was 77.50 μg / mL, and the MIC against SK2 was 77.50 μg / mL. SK1 was treated with free CIN, free CUR, ZS@CIN NPs, ZS@CUR NPs, and ZS@CIN-CUR NPs. The minimum bactericidal concentration (MBC) value of ZS@CUR NPs was 82.00 μg / mL, and when treating SK2, the MBC value was 82.00 μg / mL. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of ZS@CIN-CUR NPs were significantly lower than those of other test substances, indicating that compared with ZS@CIN NPs and ZS@CUR NPs, ZS@CIN-CUR NPs had the best antibacterial effect.

[0095] Table 1 Determination of MIC and MBC values of different nanoparticles against gas-producing bacteria

[0096]

[0097] 2. Inhibitory effect of zein-based cinnamaldehyde-curcumin composite nanoparticles on gas-producing bacteria in pickled Chinese cabbage

[0098] The pickled Chinese cabbage after fermentation was sterilized, and the gas-producing bacteria were activated and inoculated into the pickled Chinese cabbage samples. The initial bacterial count of the gas-producing strains was 3.70 - 4.03 log CFU / g. The pickled Chinese cabbage samples after inoculation were divided into two groups: one group was added with zein-based cinnamaldehyde-curcumin composite nanoparticles to the minimum inhibitory concentration; the other group was placed naturally (blank control group). The above two groups of pickled Chinese cabbage were placed at a constant temperature of 37°C, and whether the pickled Chinese cabbage had the phenomenon of bulging bags was observed, and the experiment was repeated three times in parallel.

[0099] Inhibitory test results of zein-based cinnamaldehyde-curcumin composite nanoparticles on gas-producing bacteria in pickled Chinese cabbage: As Figure 6 shown in A and B, after the pickled Chinese cabbage was sterilized at high temperature, neither group of pickled Chinese cabbage had a bright color. There was no phenomenon of bulging bags in the zein-based cinnamaldehyde-curcumin composite nanoparticle group ( Figure 6 shown in B); there was a phenomenon of bulging bags in the blank control group ( Figure 6 shown in A). It can be concluded that zein-based cinnamaldehyde-curcumin composite nanoparticles have a good antibacterial effect on gas-producing bacteria in pickled Chinese cabbage.

[0100] Example 5 Preservation effect of zein-based cinnamaldehyde-curcumin composite nanoparticles

[0101] Sample treatment: The pickled Chinese cabbage after fermentation was put into water and washed for 4 - 5 min, and divided into three groups. Blank control group (Control): The pickled Chinese cabbage was not added with nanoparticles after washing and was placed naturally; ZS@CIN-CUR NPs group: The pickled Chinese cabbage was added with ZS@CIN-CUR NPs (minimum inhibitory concentration) after washing; ZS NPs group: The pickled Chinese cabbage was added with the same concentration of ZS NPs after washing. The above three groups were stored at 37°C for 35 d, and samples were randomly taken every 7 d to measure the quality indexes of the pickled Chinese cabbage during storage. The experiment was repeated 3 times in parallel, and the results were averaged.

[0102] 1. Change of chromaticity value of pickled Chinese cabbage during storage

[0103] The chromaticity value can reflect the freshness of pickled Chinese cabbage to a certain extent, and it is the main basis for consumers to choose products. As Figure 7As shown, during the entire storage period (0 d to 35 d) of pickled Chinese cabbage, the L* (brightness) values showed a decreasing trend. On the 35th day of storage, the L* values of the Chinese cabbage stalks and leaves in the ZS@CIN-CUR NPs group were 59.09 and 58.44 respectively, which were higher than those of the blank control group and the ZS NPs group (P<0.05). This indicates that the decrease in L* value during the storage period is a normal trend, and ZS@CIN-CUR NPs can delay the decrease of L* in pickled Chinese cabbage. During the entire storage period (0 d to 35 d), the b* values and a* values of pickled Chinese cabbage in each group showed an increasing trend. Among them, the b* value of pickled Chinese cabbage in the ZS@CIN-CUR NPs group was higher than that of the other two groups, and the a* value was lower than that of the other two groups. This indicates that ZS@CIN-CUR NPs have a positive effect on improving the color of pickled Chinese cabbage during storage and inhibiting the color change of pickled Chinese cabbage to red during storage, thus achieving the purpose of long-term storage.

[0104] 2. Sensory evaluation results during the storage of pickled Chinese cabbage

[0105] The sensory evaluation personnel were 20 food major students who were familiar with food description attributes and food judgment criteria. The scoring criteria were formulated according to the national standard GB / T10221-2021 as shown in Table 2, and the final score was the sum of all score values (100 points).

[0106] Table 2 Sensory scoring criteria for pickled Chinese cabbage

[0107]

[0108] The three groups of pickled Chinese cabbage were subjected to sensory evaluation in combination with the scoring table. As Figure 8 shown, the pickled Chinese cabbage in the ZS@CIN-CUR NPs group presented a bright color and did not show serious browning ( Figure 8 C in the figure), the pickled Chinese cabbage in the ZS NPs group was dull, and the blank control group had a dull color and serious browning ( Figure 8 B in the figure). On the 35th day of storage, in terms of flavor, taste and tissue state, the highest sensory evaluation score of the ZS@CIN-CUR NPs group reached 92 points, which was better than that of the blank control group ( Figure 8 A in the figure) and the ZS NPs group.

[0109] 3. Changes in total acid content during the storage of pickled Chinese cabbage

[0110] Organic acids in pickled Chinese cabbage are the main flavor substances, among which L-lactic acid is the most important organic acid. Organic acids with different sourness characteristics together form the flavor of pickled Chinese cabbage with fresh, fragrant and pure sour taste. As Figure 9As shown in the figure, with the extension of storage time, the total acid content of pickled Chinese cabbage showed an upward trend. Among them, the total acid content of pickled Chinese cabbage in the ZS@CIN-CUR NPs group increased to 9.02 g / kg. The reason is that the acid production activity of lactic acid bacteria continued during the initial stage of pickled Chinese cabbage storage. With the extension of storage time, the upward trend tended to level off. This was because with the increase in acidity of the storage environment, the nutrients in pickled Chinese cabbage were consumed, and microbial metabolites accumulated, which not only inhibited the growth, reproduction and physiological activities of lactic acid bacteria, but also the growth of a small amount of spoilage bacteria gradually consumed the organic acids in the environment. On the 35th day of storage, the ZS@CIN-CUR NPs group was significantly higher than the blank control group (P<0.05). There was no significant difference between the ZS NPs group and the blank control group (P>0.05), indicating that ZS@CIN-CUR NPs was beneficial to maintaining the acidity of pickled Chinese cabbage.

[0111] 4. Changes in Soluble Protein Content during the Storage of Pickled Chinese Cabbage

[0112] Soluble protein is one of the important indicators to measure the nutritional value of fruits and vegetables, and it is also an important basic substance for the Maillard reaction. As Figure 10 shown in the figure, during the storage period (0 d to 35 d), the soluble protein content of pickled Chinese cabbage showed a general downward trend, which was related to the protein hydrolysis in pickled Chinese cabbage. Among them, the soluble protein content of the ZS@CIN-CUR NPs group was higher than that of other groups. On the 35th day of storage, the soluble protein content of the blank control group was about 1.32 mg / g, and that of the ZS@CIN-CUR NPs group was about 1.64 mg / g. The results showed that ZS@CIN-CUR NPs delayed the degradation of soluble protein in pickled Chinese cabbage, curbed the browning of pickled Chinese cabbage, and maintained the quality of pickled Chinese cabbage.

[0113] 5. Changes in Amino Acid Nitrogen Content during the Storage of Pickled Chinese Cabbage

[0114] The content of amino acid nitrogen is an important indicator to measure the degree of protein decomposition and nutritional value in food. Insufficient content will lead to the lack of flavor hierarchy and the decline of nutritional value in pickled Chinese cabbage. As Figure 11 shown in the figure, the content of amino acid nitrogen showed a decreasing trend during the whole storage process. In the early stage of storage, the content of amino acid nitrogen in the ZS@CIN-CUR NPs group, ZS NPs group and blank control group increased briefly to reach the maximum value. In the later stage of storage, the content of amino acid nitrogen in the ZS@CIN-CUR NPs group, ZS NPs group and blank control group gradually decreased. On the 35th day of storage, the content of amino acid nitrogen in the ZS@CIN-CUR NPs group was 56 mg / kg and then tended to be stable. During the whole fermentation process, the content of amino acid nitrogen in the ZS@CIN-CUR NPs group was higher than that in the blank control group and ZS NPs group, indicating that zein-based cinnamaldehyde-curcumin composite nanoparticles were beneficial to increasing the amino acid content in pickled Chinese cabbage products and maintaining the umami flavor of pickled Chinese cabbage.

[0115] 6. Changes in pH during the storage of pickled Chinese cabbage

[0116] The pickled Chinese cabbage leaves and stalks of the ZS@CIN-CUR NPs group, ZS NPs group, and blank control group were taken respectively, mixed and pulped, and then filtered. The pH was measured using a PHs-3C precision pH meter.

[0117] The results are as Figure 12 shown. During the storage period, the pH of the ZS@CIN-CUR NPs group, ZS NPs group, and blank control group showed a downward trend as a whole. On the 35th day of storage, the pH of the ZS@CIN-CUR NPs group was 3.42, lower than the pH value of 3.54 in the blank control group, with significant difference (P<0.05), while there was no significant difference between the blank control group and the ZS NPs group (P>0.05). This may be due to the acid production and metabolism of lactic acid bacteria during the storage period, resulting in the accumulation of lactic acid in the environment and the decrease of pH value. At the same time, the growth and metabolite accumulation of spoilage bacteria during the storage process inhibited the growth of lactic acid bacteria and consumed the acid in the pickled Chinese cabbage. It shows that ZS@CIN-CUR NPs is beneficial to maintaining a lower pH value of pickled Chinese cabbage and inhibiting the growth of miscellaneous bacteria.

[0118] 7. Changes in ascorbic acid during the storage of pickled Chinese cabbage

[0119] 10 g of the ZS@CIN-CUR NPs group, ZS NPs group, and blank control group were taken respectively and placed in a mortar. A small amount of 20 g / L oxalic acid solution was added, and the mixture was ground into a slurry under ice bath conditions. The 2,6-dichlorophenol indophenol titration method was used for determination.

[0120] The results are as Figure 13 shown. During the 35-day storage period, the ascorbic acid content of the pickled Chinese cabbage decreased continuously with the extension of the storage time. The decline of the ascorbic acid content in the pickled Chinese cabbage was relatively fast in the early stage of storage, and the decline rate slowed down in the later stage of storage. On the 35th day, the ascorbic acid contents of the ZS@CIN-CUR NPs group, ZS NPs group, and blank control group were 6.78 mg / 100 g, 5.25 mg / 100 g, and 4.19 mg / 100 g respectively. On the 35th day of the storage period, the ascorbic acid content of the ZS@CIN-CUR NPs group was significantly higher than that of other groups (P<0.05). Therefore, ZS@CIN-CUR NPs is beneficial to inhibiting the oxidation of ascorbic acid.

[0121] 8. Changes in nitrite during the storage of pickled Chinese cabbage

[0122] The determination was carried out with reference to the method of GB 5009.33-2016.

[0123] The results are as Figure 14As shown, during the 35-day storage period, the nitrite content in pickled cabbages of each group showed a trend of first increasing and then decreasing. On the 35th day, the nitrite content in pickled cabbages of the ZS@CIN-CUR NPs group was only 0.400 mg / kg, while that in the blank control group was 0.917 mg / kg. The ZS@CIN-CUR NPs group was significantly lower than the control group (P<0.05), and there was no significant difference between the ZS NPs group and the control group (P>0.05). The test results indicate that ZS@CIN-CUR NPs have an inhibitory effect on the growth of nitrite in pickled cabbages.

[0124] Only some exemplary embodiments of the present invention have been described by way of illustration above. Without doubt, for those of ordinary skill in the art, the described embodiments can be modified in various different ways without departing from the spirit and scope of the present invention. Therefore, the above description is illustrative in nature and should not be construed as a limitation on the protection scope of the claims of the present invention.

Claims

1. Zein-based cinnamaldehyde-curcumin composite nanoparticles, characterized in that, Using zein as a nanocarrier, cinnamaldehyde and curcumin as drug carriers, and sodium alginate as a stabilizer.

2. The zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 1, wherein, The mass ratio of curcumin, cinnamaldehyde to zein is 1-8:1-8:15, and the mass ratio of zein to sodium alginate is 10:1-1:

10.

3. The preparation method of zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 1 or 2, characterized in that, It includes the following steps: Dropwise add zein solution, cinnamaldehyde solution and curcumin solution into the sodium alginate aqueous solution at the same time. After mixing evenly, dialyze to remove the organic solvent to obtain zein-based cinnamaldehyde-curcumin composite nanoparticles; The solvents of the zein solution, cinnamaldehyde solution and curcumin solution are ethanol aqueous solutions.

4. The preparation method of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 3, wherein, The water in the sodium alginate aqueous solution is ultrapure water; The volume concentration of the ethanol aqueous solution is 50%-95%.

5. The preparation method of zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 3, wherein, The concentration of the sodium alginate aqueous solution is 1-5 mg / mL; The concentration of the zein solution is 1-5 mg / mL; The concentrations of the curcumin solution and cinnamaldehyde solution are independently 200-500 μg / mL.

6. The preparation method of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 3, wherein, The way of mixing evenly is magnetic stirring for 20-50 min; The dialysis is carried out with a dialysis bag of 3500 Da for 12-24 h.

7. Application of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 1 or 2 in pickled cabbage preservation.

8. Use of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 7 in pickled cabbage preservation, characterized in that, Put the pickled cabbage after fermentation into water and wash for 4-5 min, add zein-based cinnamaldehyde-curcumin composite preservation nanoparticles, and store after vacuum packaging.

9. Use of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 8 in pickled cabbage preservation, characterized in that, The addition amount of the zein-based cinnamaldehyde-curcumin composite preservation nanoparticles is 0.01-0.04 g / kg.

10. Use of the zein-based cinnamaldehyde-curcumin composite nanoparticles according to claim 8 in pickled vegetable preservation, characterized in that, Wash and blanch the fresh Chinese cabbage and then dry it in the sun, put it into a pickling container, add brine with a concentration of 3.5 wt%, seal and ferment. After fermentation, the pickled cabbage after fermentation is obtained.

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