Flax polyphenol microcapsules, and preparation method and application thereof

Abstract

The application discloses flax polyphenol microcapsules, a preparation method and application thereof; the preparation method of the flax polyphenol microcapsules comprises the following steps: mixing flax polyphenol, wall material and an additive to obtain flax polyphenol microcapsules; wherein the mass ratio of the flax polyphenol to the wall material is 2-10:1; and the wall material comprises flaxseed protein-isolated flaxseed gum Maillard copolymer. The flax polyphenol microcapsules prepared by the application can be directly added into flaxseed oil, has a good inhibiting effect on the formation of primary oxidation products and secondary oxidation products of the flaxseed oil, can protect polyunsaturated fatty acids (oleic acid and linolenic acid) from being oxidized, and shows good antioxidant activity.

Description

Technical Field

[0001] This invention belongs to the field of biomaterials technology, specifically relating to a flax polyphenol microcapsule, its preparation method, and its application. Background Technology

[0002] Flaxseed oil, also known as linseed oil or sesame oil, is a dried oil extracted from flaxseeds. It is mainly composed of alpha-linolenic acid (ALA), linoleic acid, oleic acid, and 9%–11% saturated fatty acids, with ALA (C18:3) accounting for 50%–60%. ALA plays an important role in brain development, cardiovascular health prevention, anti-inflammation, and anti-cancer effects. However, the high content of unsaturated fatty acids in flaxseed oil is susceptible to lipid oxidation due to environmental factors, reducing its nutritional value; therefore, antioxidants are usually added to flaxseed oil.

[0003] Tert-butylhydroquinone (TBHQ) is a highly effective antioxidant. In food, it is used as an antioxidant in vegetable oils and various edible animal fats. It does not change color or alter the taste or odor of food when exposed to iron. It can also be used in conjunction with other preservatives such as butylated hydroxyanisole (BHA). The European Food Safety Authority (EFSA) and the U.S. Food and Drug Administration (FDA) have determined that TBHQ is safe for human use within certain concentrations, with the FDA limiting its addition to edible oils to 0.02%. However, in experiments, higher concentrations of TBHQ have shown signs of gastric tumors and DNA damage in experimental animals.

[0004] Therefore, there is an urgent need to find a natural oxidant to improve the antioxidant safety of flaxseed oil. Summary of the Invention

[0005] The purpose of this invention is to address the safety of flaxseed oil during the antioxidant process. This invention provides a flaxseed polyphenol microcapsule, the preparation materials of which are all derived from flaxseed. It not only effectively utilizes the seed cake after flaxseed oil extraction, but also effectively prevents the oxidation of unsaturated fatty acids in flaxseed oil by adding flaxseed polyphenol microcapsules, thus ensuring high safety.

[0006] In a first aspect, the present invention provides a method for preparing flax polyphenol microcapsules, comprising the following steps: mixing flax polyphenols, wall material, and additives to obtain flax polyphenol microcapsules; wherein the mass ratio of flax polyphenols to wall material is 2 to 10:1; and the wall material comprises flaxseed protein isolate-flaxseed gum Maillard copolymer.

[0007] In some specific embodiments of the present invention, the mass ratio of the flax polyphenols to the wall material is 4:1.

[0008] In this invention, the adjuvants include, but are not limited to, sodium carboxymethyl cellulose and monoglycerides; further, the adjuvant is a monoglyceride.

[0009] In this invention, the order of adding flax polyphenols, wall materials, and auxiliaries is not limited. Two of the flax polyphenols, wall materials, and auxiliaries can be mixed first, and then the other one can be added. Alternatively, flax polyphenols, wall materials, and auxiliaries can be added and mixed at the same time. Preferably, flax polyphenols and wall materials are mixed first, and then the auxiliaries are added.

[0010] In some specific embodiments of the present invention, the amount of the additive is 0.05% to 0.15%.

[0011] In some specific embodiments of the present invention, the amount of the additive is 0.1%.

[0012] Secondly, the present invention provides flax polyphenol microcapsules prepared by the aforementioned preparation method.

[0013] In some specific embodiments of the present invention, the average particle size of the flax polyphenol microcapsules is 70.96 μm.

[0014] Thirdly, the present invention provides an application of the aforementioned flax polyphenol microcapsules in the antioxidant properties of plant oils.

[0015] In this invention, the vegetable oils include, but are not limited to, flaxseed oil, olive oil, peanut oil, soybean oil, rapeseed oil, sunflower seed oil, corn oil, camellia seed oil, sesame oil, and palm oil.

[0016] In some specific embodiments of the present invention, the vegetable oil is flaxseed oil.

[0017] In some specific embodiments of the present invention, the flax polyphenol microcapsules are directly added to the vegetable oil and thoroughly stirred and mixed.

[0018] In some specific embodiments of the present invention, the amount of flax polyphenol microcapsules added is 0.01% to 0.02% of the weight of the vegetable oil.

[0019] Fourthly, the present invention provides an antioxidant comprising the flax polyphenol microcapsules.

[0020] Fifthly, the present invention provides a flaxseed oil microcapsule, comprising flaxseed oil, an antioxidant, and a wall material; wherein the antioxidant is the aforementioned flaxseed polyphenol microcapsule.

[0021] The present invention has the following beneficial effects:

[0022] This invention provides a flaxseed microcapsule, which, when added to flaxseed oil, effectively inhibits the formation of primary and secondary oxidation products and protects polyunsaturated fatty acids (oleic acid and linolenic acid) from oxidation, demonstrating good antioxidant activity. Attached Figure Description

[0023] Figure 1 Particle size distribution of flax polyphenol microcapsules;

[0024] Figure 2 Scanning electron microscope images (a: linseed polyphenols; b: wall material; c: microcapsules);

[0025] Figure 3 Fourier transform infrared spectra of flax polyphenols, wall materials, and microcapsules;

[0026] Figure 4 Thermogravimetric analysis diagrams of flax polyphenols, wall materials, and microcapsules;

[0027] Figure 5 The effect of different antioxidants on the peroxide value of flaxseed oil;

[0028] Figure 6 The effect of different antioxidants on the conjugated diene value of linseed oil;

[0029] Figure 7 The effect of different antioxidants on the acid value of flaxseed oil;

[0030] Figure 8 The effect of different antioxidants on the thiobarbituric acid value of flaxseed oil;

[0031] Figure 9 The effect of different antioxidants on conjugated trienes in linseed oil;

[0032] Figure 10 The effects of different antioxidants on saturated and unsaturated fatty acids in flaxseed oil. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Example 1: Preparation of flax polyphenol microcapsule wall material

[0035] Weigh 0.6 g of flaxseed protein isolate and dissolve it in 100 mL of 10 mmol / L phosphate buffer (pH = 7.5). Add 0.2 g of flaxseed gum and stir thoroughly to dissolve. After standing at 4°C overnight to ensure complete hydration, freeze-dry, grind, and then sieve (60 mesh) to obtain a uniform powder. Place the powder in a petri dish covered with aluminum foil, and poke a certain number of small holes in the foil. Place it in a desiccator (with saturated KBr solution at the bottom) and react at 79% relative humidity and 60°C for 48 h.

[0036] Example 2: Extraction of linseed polyphenols

[0037] (1) Extraction: Defatted flaxseed powder with a particle size of 60 mesh was used as raw material, and 60% ethanol was used as the extraction solvent. The ultrasonic power was 400W, the material-to-liquid ratio was 1:10, the ultrasonic temperature was 40℃, and the ultrasonic time was 15min. The mixture was shaken once every 5min to ensure uniform ultrasonication. After ultrasonication, the mixture was centrifuged for 10min to separate the residue and supernatant. The residue was subjected to a second extraction, and the supernatants from the two extractions were combined. The solvent was then evaporated using a rotary vacuum evaporator, and the concentrated extract was freeze-dried at -40℃.

[0038] (2) Purification: The pretreated AB-8 macroporous resin was packed into a column using a wet method. The loading concentration was 2.5 mg / mL, the loading volume was 2 BV, and the loading flow rate was 1 mL / min. Elution was performed with 60% ethanol solution at a flow rate of 5 mL / min and a volume of 5 BV. The eluent was collected, the solvent was removed by rotary evaporation, and the eluent was lyophilized to obtain linseed polyphenols.

[0039] Example 3: Flaxseed Polyphenol Microcapsules

[0040] Flax polyphenols were mixed with wall material at a mass ratio of 4:1 at a mass concentration of 2%. After stirring evenly, 0.1% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 92.42%.

[0041] Example 4

[0042] Flax polyphenols were mixed with wall material at a mass ratio of 2:1 at a mass concentration of 2%. After stirring evenly, 0.15% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 90.51%.

[0043] Example 5

[0044] Flax polyphenols were mixed with wall material at a mass ratio of 6:1 at a mass concentration of 1%. After stirring evenly, 0.1% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 87.59%.

[0045] Example 6

[0046] Flax polyphenols were mixed with wall material at a mass ratio of 4:1 at a mass concentration of 1%. After stirring evenly, 0.15% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 89.49%.

[0047] Example 7

[0048] Flax polyphenols were mixed with wall material at a mass ratio of 2:1 at a mass concentration of 1%. After stirring evenly, 0.05% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 87.14%.

[0049] Example 8

[0050] Flax polyphenols were mixed with wall material at a mass ratio of 6:1 at a mass concentration of 2%. After stirring evenly, 0.05% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 87.95%.

[0051] Example 9

[0052] Flax polyphenols were mixed with wall material at a mass ratio of 2:1 at a mass concentration of 2%. After stirring evenly, 0.1% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 88.81%.

[0053] Example 10

[0054] Flax polyphenols were mixed with wall material at a mass ratio of 4:1 at a mass concentration of 3%. After stirring evenly, 0.05% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 89.02%.

[0055] Example 11

[0056] Flax polyphenols were mixed with wall material at a mass ratio of 6:1 at a mass concentration of 3%. After stirring evenly, 0.15% monoglyceride was added. The mixture was magnetically stirred for 20 minutes, then sheared and homogenized at 10,000 r / min for 10 minutes. The mixture was then freeze-dried. The freeze-dried microcapsules were then ground and passed through a 60-mesh sieve to obtain flax polyphenol microcapsules with an encapsulation rate of 88.38%.

[0057] Example 12: Testing of Flaxseed Polyphenol Capsules

[0058] The flax polyphenol capsules prepared in Example 3 were tested for the following indicators.

[0059] 1 Method

[0060] 1.1 Determination of Physicochemical Indicators of Flaxseed Polyphenol Microcapsules

[0061] (1) Moisture content

[0062] Accurately weigh 2.0g of the microcapsule product (mass m1), place it in an oven at 105℃ for 4 hours to dry, remove it and cool it in a desiccator, then weigh it again (mass m2). Calculate using the following formula:

[0063]

[0064] (2)Water activity

[0065] Water activity was measured using a water activity meter; the measurement conditions were: temperature 20℃ and time 10 min.

[0066] (3) Liquidity

[0067] The flowability of microcapsule products was evaluated using the angle of repose method: The bottom of a funnel with its lower end flush with the paper was blocked, and 5g of microcapsule polyphenol powder was added to the funnel, maintaining a gap of approximately 2cm between the bottom of the funnel and the paper. The powder was allowed to flow freely onto the smooth surface below. The height H of the microcapsule stack and the radius R of the stack coverage were measured, and the angle of repose θ of the microcapsules was calculated using the following formula.

[0068]

[0069] Where: H - height of the cone formed by the sample / cm; R - radius of the cone formed by the sample / cm.

[0070] (4) Bulk density

[0071] Pour the microcapsule product into a 10mL graduated cylinder, shake well and compact, until the microcapsules fill to the graduation mark on the graduated cylinder. Record the mass m of the filled microcapsules and the filling volume v of the graduated cylinder. Calculate the packing density of the microcapsules using the following formula.

[0072]

[0073] Where: d - microcapsule bulk density, g / cm³ 3 m - sample mass, g; v - graduated cylinder filling volume, cm³ 3 .

[0074] (5) Particle size

[0075] A suitable amount of microcapsules was placed in a beaker, and anhydrous ethanol was used as the dispersant. 5.0 mL of the 0.1 g / mL microcapsule solution was pipetted into the laser particle size analyzer measuring chamber. The sample refractive index was 1.5, the rotation speed was 2500 r / min, and the average particle size of the microcapsules was determined using the laser particle size analyzer.

[0076] (6) Color

[0077] The colorimetry of the microcapsules was measured using a colorimeter, and the measured L*, a*, and b* values ​​were recorded.

[0078] 1.2 Characterization of the structure of linseed polyphenol microcapsules

[0079] 1.2.1 Scanning Electron Microscope

[0080] The surface morphology was observed using a scanning electron microscope. The sample preparation method was as follows: a layer of double-sided tape was attached to the sample stage, the microcapsule powder was gently sprinkled on it and the excess powder was blown away, and then gold was sprayed onto the sample for observation. The accelerating voltage was 15kV.

[0081] 1.2.2 Fourier Transform Infrared Spectroscopy

[0082] Take 1 mg of sample, add 100 mg of potassium bromide, grind into powder, manually compress into tablets, remove the sample and place in the sample chamber at 4000 cm⁻¹ -1 -400cm -1 Wavenumber scanning, 32 scans, resolution 4cm -1 .

[0083] 1.2.3 Thermogravimetric analysis determination

[0084] Thermogravimetric analysis (TGA) was used to analyze the thermal stability of the samples. The samples were accurately weighed and placed in a sample cell for thermogravimetric analysis. Detection conditions: high-purity nitrogen was used as the protective gas, with a nitrogen flow rate of 20 mL / min and a heating rate of 10 °C / min, from 30 °C to 700 °C.

[0085] 2 Results

[0086] 2.1 Physicochemical analysis of flaxseed polyphenol microcapsules

[0087] As shown in Table 1, the flax polyphenol microcapsules have a moisture content of 2.94%, which is low and beneficial for product preservation, maintaining good quality during storage. Generally, foods with a water activity below 0.6 are considered microbially stable; the flax polyphenol microcapsules have a water activity of 0.21, indicating that the flax polyphenol microcapsules prepared by freeze-drying are relatively stable. The angle of repose of the flax polyphenol microcapsule product is 37.95°, falling between 30° and 45°, indicating good flowability. The bulk density of the flax polyphenol microcapsules is 0.31 g / cm³. 3 This indicates that the microcapsule product has relatively large internal voids. The average volumetric particle size of the linseed polyphenol microcapsules is 70.96 μm, and the particle size of the microcapsules exhibits a normal distribution and is relatively narrow. Figure 1 ).

[0088] Table 1. Results of physicochemical properties of microcapsules

[0089]

[0090] 2.2 Structural Analysis of Flaxseed Polyphenol Microcapsules

[0091] 2.2.1 Scanning electron microscopy analysis

[0092] like Figure 2 As shown, the flax polyphenol microcapsules of the present invention are multinucleated microcapsules. The flax polyphenols are mainly spherical and accompanied by flocculent material. The wall material has a sheet-like structure. The microencapsulated polyphenols are uniformly dispersed in the wall material, and the dispersion is relatively sufficient and the encapsulation is relatively complete.

[0093] 2.2.2 Fourier Transform Infrared Spectroscopy Analysis

[0094] like Figure 3 As shown, in the range of 800-1500cm -1 (Fingerprint area), 1500-2000cm -1 (CH stretching zone) and 2500-3500cm -1 Peaks were observed in all (OH stretching regions); among them, the peak at 3425 cm⁻¹ was the highest in the OH stretching region. -1 3302cm -1 3419cm-1 The absorption peak at 2926 cm⁻¹ represents the OH stretching vibration. The broadest absorption peak is found in polyphenols, indicating that polyphenols contain the most abundant free hydroxyl groups. -1 2922cm -1 2921cm -1 The stretching vibration peak is represented as CH.

[0095] In the infrared spectrum of polyphenols, 1723 cm⁻¹ -1 The absorption peak at 1634 cm⁻¹ is caused by the vibration of the benzopyran ring (C=O). -1 The absorption peak at 1513 cm⁻¹ corresponds to the stretching vibration of the benzene ring (C=C). -1 The peak at 1373 cm⁻¹ is likely caused by the deformation vibrations of the two benzene rings in the polyphenol. -1 This is caused by the in-plane bending vibration of the OH group, and is the absorption peak of phenols, occurring in the range of 1000-1300 cm⁻¹. -1 There is a range of 1074cm -1 1163cm -1 1268cm -1 The absorption peak is the absorption peak of the COC or hydroxyl stretching vibration of phenols, indicating the presence of aromatic compounds derived from phenolic compounds. Additionally, there is an absorption peak at 817 cm⁻¹. -1 The absorption peak at that point is also a characteristic absorption peak of flax polyphenols.

[0096] The absorption peak intensity of linolenic acid in the infrared spectrum of the linolenic acid microcapsules was significantly weakened. This is because a small amount of linolenic acid that was not completely encapsulated was embedded on the surface of the wall material, which weakened the absorption of the characteristic peak, indicating that the linolenic acid had entered the inner cavity of the microcapsule. The Fourier transform infrared spectrum of the microcapsule was similar to that of the wall material, proving that the encapsulation was successful.

[0097] 2.2.3 Thermogravimetric Analysis

[0098] like Figure 4 As shown, the thermogravimetric curves of the three samples are similar, with a total of three weight losses occurring between 30 and 900℃. The first weight loss occurs between 30 and 200℃, mainly due to the evaporation of free and bound water. The second weight loss occurs between 200 and 500℃, and the third weight loss occurs between 500 and 900℃, eventually forming a dense, solid black charred substance with a porous interior.

[0099] The weight loss rate of linseed polyphenols was 4.78% in the first weight loss test, 72.13% in the second, and 10.7% in the third. The weight loss rate of linseed polyphenol microcapsules was 3.34% in the first test, 65.05% in the second, and 7.25% in the third. The weight loss rate of the wall material was not significantly different from that of the linseed polyphenol microcapsules, with first, second, and third weight losses of 2.178%, 63.67%, and 8.33%, respectively, indicating that the linseed polyphenols, after encapsulation, acquired the thermogravimetric properties of the wall material. However, compared to linseed polyphenols, the weight loss rate of the linseed polyphenol microcapsules increased by 11.95 percentage points, indicating that an inclusion reaction occurred between the wall material and the linseed polyphenols, improving the thermal stability of the linseed polyphenol microcapsules.

[0100] Experimental Example 1: Effect of Flaxseed Polyphenol Microcapsules on Enhancing the Oxidative Stability of Flaxseed Oil

[0101] 1 Method

[0102] 1.1 Preparation of Flaxseed Oil

[0103] Flaxseeds were placed in the pressing chamber of a hydraulic press and automatically pressed for 20 minutes at a temperature of 80℃ and a pressure of 55MPa. After standing and filtering, flaxseed oil was obtained and stored in a refrigerator at 4℃ away from light.

[0104] 1.2 Preparation of Flaxseed Oil Fortified with Flax Polyphenol Microcapsules

[0105] According to the maximum usage limits for various antioxidants specified in GB 2760-2014, the selected addition amount of natural antioxidant was 0.02% of the weight of flaxseed oil. The mixture was thoroughly stirred and placed in an oven at (60±1)℃ to accelerate oxidation. The mixture was stirred once every 12 hours, and its position in the oven was changed. Flaxseed oils with added 0.02% TBHQ, 0.02% flaxseed polyphenols (FREE), and 0.02% flaxseed polyphenol microcapsules (MICR) were prepared separately. A blank test (CNTL) was performed using flaxseed oil without any added antioxidants.

[0106] 1.3 Determination of primary oxidation indicators during accelerated oxidation of fortified flaxseed oil

[0107] The peroxide value was determined by titration according to the national standard (GB 5009.227-2016), and the conjugated diene value was determined according to the national standard (GB / T 22500-2008).

[0108] 1.4 Determination of secondary oxidation indicators during accelerated oxidation of fortified flaxseed oil

[0109] Acid value was determined by hot ethanol indicator titration according to national standard (GB 5009.229-2016); thiobarbituric acid value was determined according to national standard (GB / T 35252-2017); conjugated triene was determined according to national standard (GB / T22500-2008).

[0110] 1.5 Determination of fatty acids during accelerated oxidation of fortified flaxseed oil

[0111] The fatty acid determination of flaxseed oil was performed according to the method established in our laboratory. The esterification time of flaxseed oil was 60 min, the esterification temperature was 50℃, and the catalyst addition was 1 mL. GC-FID analysis: chromatographic column (Wonda Cap WAX, 60 m × 0.25 mm × 0.25 μm); injection port temperature: 250℃; detector temperature: 250℃; split ratio: 46:1; column flow rate: 1 mL / min; injection volume: 1 μL; temperature program: first, hold at 100℃ for 13 min, then increase to 180℃ at a rate of 10℃ / min and hold for 6 min, then increase to 200℃ at a rate of 1℃ / min and hold for 20 min, then increase to 230℃ at a rate of 4℃ / min and hold for 10.5 min. Qualitative analysis was performed using fatty acid methyl ester standards, and quantification was performed using the internal standard method.

[0112] 2 Results

[0113] 2.1 Analysis of primary oxidation products during the accelerated oxidation process of enhanced flaxseed oil

[0114] (1) Peroxide value

[0115] like Figure 5As shown, with the continuous extension of oxidation time, the peroxide value of both flaxseed oil with added three antioxidants and blank flaxseed oil showed a continuous upward trend. This is because the high temperature caused the free radical chain reaction in flaxseed oil to continuously produce peroxides. The peroxide value of flaxseed oil without added antioxidants increased the fastest, reaching as high as 32.34 g / 100g after 15 days of oxidation. Flaxseed oil with added monomeric flaxseed polyphenols had a strong antioxidant effect in the early stage of oxidation, but after 6 days, the antioxidant effect weakened, and the peroxide value increased significantly, reaching 23.41 g / 100g after 15 days of oxidation. In the first few days, the peroxide value of the sample with added flaxseed polyphenol microcapsules was higher than that of monomeric flaxseed polyphenols. However, after 6 days, the peroxide value was significantly lower than that of the sample with added monomeric flaxseed polyphenols, indicating that the flaxseed polyphenol microcapsules have a certain sustained-release capacity in flaxseed oil. The release of flaxseed polyphenols requires a certain amount of time, so before the release equilibrium is reached, its antioxidant effect is not as good as that of the unencapsulated flaxseed polyphenols. After the release equilibrium is reached, its antioxidant effect gradually emerges. After 15 days of oxidation, its peroxide value was 16.41 g / 100 g, which was 49.25% lower than that of the blank control.

[0116] (2) Conjugated diene

[0117] like Figure 6 As shown, the conjugated diene values ​​of all flaxseed oils gradually increased with the extension of accelerated oxidation time. When the reaction time was 12 days, the flaxseed polyphenol microcapsules had a stronger conjugated diene inhibition effect than the monomeric polyphenols. When the reaction time was 15 days, the blank flaxseed oil had the highest conjugated diene value of 8.21. The flaxseed polyphenol microcapsules could significantly inhibit the production of olefins. The conjugated diene value of flaxseed oil at the reaction time of 12 days was 6.87, which was 16.32% lower than that of the blank flaxseed oil.

[0118] 2.2 Analysis of secondary oxidation products during the accelerated oxidation process of enhanced flaxseed oil

[0119] (1) Acid value

[0120] Fatty acid hydrolysis produces a large amount of free fatty acids; the higher the acid value, the higher the content of free fatty acids produced by the oxidation of vegetable oils. For example... Figure 7 As shown, the acid value of all flaxseed oils increased with prolonged accelerated oxidation time, with the acid value of the blank flaxseed oil reaching 1.33 mg / g after 15 days of accelerated oxidation. There was no significant difference in the antioxidant effect of encapsulated and unencapsulated flaxseed polyphenols on flaxseed oil in the first 12 days. After 15 days of accelerated oxidation, the flaxseed polyphenol microcapsules showed better antioxidant effect than the monomeric flaxseed polyphenols, with an acid value of 0.78 mg / g, which was 0.15 mg / g lower than that of the monomeric flaxseed oil.

[0121] (2) Thiobarbituric acid value

[0122] Thiobarbituric acid value indicates the content of aldehydes, secondary oxidation products, during the oxidation of vegetable oils. For example... Figure 8 As shown, the thiobarbituric acid value gradually increased with the accelerated oxidation process of flaxseed oil, indicating that the primary oxidation product of flaxseed oil, hydroperoxide, continuously decomposed into secondary oxidation products such as malondialdehyde. The thiobarbituric acid value of flaxseed oil with added flaxseed polyphenol microcapsules and TBHQ showed a fluctuating trend on day 9 of accelerated oxidation. This is because the hydroperoxide decomposition was slow in the early stages of oxidation, resulting in a slower increase in thiobarbituric acid value. As the amount of hydroperoxide decomposition products increased, specifically the secondary oxidation product malondialdehyde, it formed complexes with amino acids and proteins present in flaxseed oil, causing malondialdehyde to exist in a bound state and resulting in a temporary decrease in thiobarbituric acid value. On day 15 of accelerated oxidation, the thiobarbituric acid value of flaxseed oil with added flaxseed polyphenol microcapsules decreased by 0.23 compared to the blank flaxseed oil, demonstrating a good ability to inhibit thiobarbituric acid value.

[0123] (3) Conjugated trienes

[0124] The conjugated triene value indicates the content of ketones during the later stages of oxidation in flaxseed oil; for example... Figure 9 As shown, on day 15 of accelerated oxidation of flaxseed oil, the inhibitory capacity for ketone formation was as follows: TBHQ > flaxseed polyphenol microcapsules > monomeric flaxseed polyphenols. This indicates that flaxseed polyphenol microcapsules can continuously inhibit the production of ketones, and the inhibitory effect is better than that of monomeric flaxseed polyphenols. Compared with the blank group, the inhibitory capacity of flaxseed polyphenol microcapsules on ketones in flaxseed oil was increased by 43.61%.

[0125] 2.3 Fatty acid analysis during the accelerated oxidation process of fortified flaxseed oil

[0126] As shown in Table 2, flaxseed oil mainly contains five fatty acids, with the following content from highest to lowest: linolenic acid (52.49g / 100g) > oleic acid (21.54g / 100g) > linoleic acid (15.30g / 100g) > palmitic acid (4.47g / 100g) > stearic acid (3.71g / 100g), of which the content of unsaturated fatty acids reaches 91.66%. After accelerated oxidation for 15 days, the order of linolenic acid content in different flaxseed oils was: TBHQ > flaxseed polyphenol microcapsules > monomeric flaxseed polyphenols, and the order of oleic acid content was: flaxseed polyphenol microcapsules > TBHQ > monomeric flaxseed polyphenols. This indicates that flaxseed polyphenol microcapsules showed a good protective effect on linolenic acid and oleic acid.

[0127] like Figure 10As shown, before accelerated oxidation, the content of saturated fatty acids in the blank flaxseed oil was 8.17 g / 100g, and the content of unsaturated fatty acids was 89.34 g / 100g. After accelerated oxidation, the content of saturated fatty acids in the blank flaxseed oil was 8.91 g / 100g, and the content of unsaturated fatty acids was 75.87 g / 100g. This indicates that during the oxidation process of flaxseed oil, unsaturated fatty acids gradually shift towards a higher degree of saturation, thus increasing the content of saturated fatty acids. After 15 days of accelerated oxidation, the content of unsaturated fatty acids was in the following order: TBHQ > flaxseed polyphenol microcapsules > monomeric flaxseed polyphenols. Flaxseed polyphenol microcapsules have good antioxidant activity and can be a good substitute for the synthetic antioxidant TBHQ.

[0128] Table 2. Effects of different antioxidants on the fatty acid composition of flaxseed oil

[0129]

[0130]

[0131] Note: C 16:0 - Palmitic acid; C 18:0 - Stearic acid; C 18:1 -Oleic acid; C 18:2 -Linoleic acid; C 18:3 -Linolenic acid

[0132] Accelerated oxidation experiments were conducted after adding flaxseed polyphenol microcapsules to flaxseed oil. The results showed that the flaxseed polyphenol microcapsules had a good inhibitory effect on the formation of primary and secondary oxidation products, and at the same time, they could protect polyunsaturated fatty acids (oleic acid and linolenic acid) from oxidation, showing good antioxidant activity.

[0133] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing flax polyphenol microcapsules, characterized in that, The process includes the following steps: mixing flax polyphenols, wall material, and additives to finally prepare flax polyphenol microcapsules; wherein the mass ratio of flax polyphenols to wall material is 2 to 10:1; the wall material includes flaxseed protein isolate-flaxseed gum Maillard copolymer; and the additives include at least one of sodium carboxymethyl cellulose and monoglycerides.

2. The preparation method according to claim 1, characterized in that, The mass ratio of flax polyphenols to wall material is 4:

1.

3. Flax polyphenol microcapsules prepared by the preparation method according to claim 1 or 2.

4. The application of the flax polyphenol microcapsules according to claim 3 in the antioxidant properties of vegetable oils.

5. The application according to claim 4, characterized in that, The vegetable oils are selected from flaxseed oil, olive oil, peanut oil, soybean oil, rapeseed oil, sunflower seed oil, corn oil, camellia seed oil, sesame oil, and palm oil.

6. The application according to claim 4, characterized in that, The flax polyphenol microcapsules were added directly to the vegetable oil and thoroughly mixed.

7. The application according to claim 6, characterized in that, The amount of flaxseed polyphenol microcapsules added is 0.01% to 0.02% of the weight of the vegetable oil.

8. An antioxidant, characterized in that, Including the flax polyphenol microcapsules as described in claim 3.

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