A modified starch for use in microencapsulated wheat germ oil and a wheat germ oil

Abstract

The application discloses modified starch applied to microencapsulated wheat germ oil and the wheat germ oil, and belongs to the technical field of instant cereal products. The modified starch is phosphate and acetic acid esterified starch, the phosphoryl substitution degree of the modified starch is 0.03-0.07, and the acetyl substitution degree is 0.1-0.5. The microencapsulated wheat germ oil has a double-layer embedding structure. The core material comprises wheat germ oil, lactobacillus plantarum, lactobacillus acidophilus and wheat germ polypeptide. The inner wall material comprises lecithin, and the outer wall material comprises modified starch. The application prepares modified starch with high light transmission, high freeze-thaw stability and low gelatinization temperature, and applies the modified starch to the preparation of microencapsulated wheat germ oil. The wheat germ oil is treated by a lactobacillus biofermentation method, and then is prepared into microcapsule wheat germ oil with a double-layer embedding structure together with lecithin and modified starch, so that the nutritional value and storage shelf life of the wheat germ oil are effectively improved.

Description

Technical Field

[0001] The invention relates to the technical field of instant cereal products, in particular to modified starch used for microencapsulating wheat germ oil and the wheat germ oil. Background Art

[0002] Starch is a natural polymer with advantages such as easy regeneration, low cost, and good biocompatibility, making it suitable as a carrier material for the delivery of bioactive substances. Natural starch offers many advantages as a microcapsule wall material, including low cost and good biocompatibility. However, it also suffers from drawbacks such as low transparency and poor freeze-thaw stability, which to some extent limit its application in microencapsulation technology.

[0003] Wheat is a staple food crop, cultivated worldwide. Wheat germ is a byproduct of wheat processing, comprising approximately 3% of the wheat kernel. Wheat germ is rich in carbohydrates (42%-47%), primarily sucrose and pentosans. It contains less starch, making it more nutritious than other carbohydrates. It also contains approximately 30% protein, of which wheat germ protein is a high-quality, complete protein source. Unsaturated fatty acids account for approximately 84%, with linoleic acid accounting for approximately 52.31%. Linoleic acid is an essential fatty acid that cannot be synthesized by the human body and must be obtained through food. Due to its nutritional properties, wheat germ is widely used in health foods and is known as a "natural treasure trove of human nutrition." Wheat germ oil, derived from wheat germ, is rich in polyunsaturated fatty acids, tocopherols, phytosterols, and other nutrients. It has antioxidant and anti-fatigue properties, making it a high-end edible oil widely used in healthcare.

[0004] Wheat germ oil quality indicators, such as acid value and peroxide value, are significantly affected by extraction technology, refining process, and storage conditions. The free fatty acid content of fresh wheat germ oil ranges from 6.0% to 7.5%. One study found that during periodic storage, the acid value of wheat germ oil increased from 14.88 mg / g to 23.46 mg / g. However, at 70°C, lipase activity was inhibited, reducing the acid value from 14.88 mg / g to 12.02 mg / g. This suggests that temperature control can be used to inhibit lipase activity and achieve an optimal acid value. Another study suggests that irradiation can inactivate lipase, thereby reducing the acid value and extending the shelf life of wheat germ oil. Furthermore, during the refining process of wheat germ oil, the alkali refining and deacidification step reduces the acid value of the oil by binding the free fatty acids in the crude oil with caustic soda solution. However, the lipase in wheat germ is highly stable, retaining over 20% residual activity even after heat treatment at 60-90°C for 1 hour. Therefore, it is still necessary to develop a modified starch suitable for microencapsulated wheat germ oil and a wheat germ deep processing method. Summary of the Invention

[0005] In order to overcome the deficiencies of the prior art, the present invention aims to provide a modified starch for use in microencapsulating wheat germ oil and wheat germ oil thereof.

[0006] The technical solutions for achieving the purpose of the present invention are as follows:

[0007] The invention discloses a modified starch used for microencapsulating wheat germ oil. The modified starch is starch esterified with phosphoric acid and acetate. The phosphoryl substitution degree of the modified starch is 0.03-0.07, and the acetyl substitution degree is 0.1-0.5.

[0008] Preferably, the method for preparing the modified starch comprises the following steps:

[0009] S1. Corn starch and ethanol solution are mixed to obtain starch emulsion, which is ultrasonically treated. Phosphate, urea, and sodium hydroxide are added to adjust the pH to 9-11. The mixture is stirred for a period of time, washed with water, dried to a moisture content of 10-20%, crushed and sieved, and microwaved for 3-8 minutes to obtain phosphate starch.

[0010] S2. Phosphate starch is mixed with deionized water to obtain starch milk, sodium hydroxide solution is added under stirring at 25-40°C to adjust the pH of the starch milk to 8-8.5, acetic anhydride is added dropwise, and the mixture is equilibrated for a period of time. Then, sodium hydroxide solution is added dropwise to adjust the pH to 8-8.5. The above steps are repeated to maintain the pH of the starch milk at an alkaline level until the pH value remains unchanged, and the reaction is terminated. The solution is neutralized with dilute acid to adjust the pH to 5.5-6.5, washed with water, dried to a water content of 10-20%, and crushed and sieved to obtain modified starch.

[0011] Preferably, the phosphate is at least one of sodium tripolyphosphate, sodium trimetaphosphate, and sodium pyrophosphate.

[0012] The present invention also protects a microencapsulated wheat germ oil, which has a double-layer embedding structure; the core material includes wheat germ oil, Lactobacillus plantarum, Lactobacillus acidophilus and wheat germ polypeptide, the inner wall material includes lecithin, and the outer wall material includes the above-mentioned modified starch.

[0013] Preferably, the modified starch has a phosphoryl substitution degree of 0.05 to 0.07 and an acetyl substitution degree of 0.18 to 0.32.

[0014] In a specific application example, the preparation method of the core material is: using supercritical CO2 extraction technology to separate wheat germ oil and wheat germ residue, using protease to hydrolyze the wheat germ residue to obtain wheat germ polypeptide, mixing the wheat germ oil, wheat germ polypeptide and distilled water for homogenization and emulsification, and then inoculating pre-activated Lactobacillus plantarum and Lactobacillus acidophilus into the wheat germ oil emulsion for fermentation for 20 to 40 hours.

[0015] Preferably, the bacterial concentration of the pre-activated Lactobacillus plantarum and Lactobacillus acidophilus is 1×10 9 ~9×10 9 cfu / ml, the inoculation amount is 0.5-3v / v%, and the mass ratio of Lactobacillus plantarum to Lactobacillus acidophilus is (1-3):1.

[0016] Preferably, the protease is alkaline protease and papain in a mass ratio of (1-3): (1-3).

[0017] Preferably, the mass ratio of the wheat germ oil to the wheat germ polypeptide is 100:(2-5).

[0018] Supercritical CO2 extraction technology is used to extract wheat germ oil, which not only avoids the problem of residual solvents that occur in traditional methods, but also significantly improves extraction efficiency and better retains the nutritional ingredients in the wheat germ oil. However, a large amount of protein (30% to 35%) is also retained in the wheat germ residue after the extraction. Among them, wheat germ protein has higher antioxidant activity and can be used as a biologically active ingredient in health foods. If it is directly discarded as waste residue, it will cause a huge waste of resources. Therefore, the present invention utilizes protease to further enzymolyze the wheat germ residue, extracts water-soluble wheat germ polypeptides, and uses them as an emulsifier for wheat germ oil, so that wheat germ oil can form a homogeneous emulsion, facilitates the carrying out of the subsequent fermentation step, thereby replacing the synthetic emulsifier (such as Tween) required for the emulsification of original wheat germ oil, and ensures food safety.

[0019] During the fermentation process of wheat germ oil, the low pH environment produced by fermentation and fermentation can significantly reduce the activities of lipase and lipoxygenase, thereby reducing the speed at which the wheat germ oil becomes rancid due to the free fatty acids produced by lipase hydrolysis, which affects the organoleptic quality, and greatly improves its storage characteristics. However, lactic acid bacteria produce lactic acid during the fermentation process, resulting in a low pH environment, which is unfavorable for the lactic acid bacteria to maintain their own vitality. Therefore, the present invention selects Lactobacillus acidophilus and Lactobacillus plantarum to ferment wheat germ oil together, thereby ensuring the vitality of the lactic acid bacteria.

[0020] Preferably, lecithin is used as the first coating layer after wheat germ oil is fermented, and the lecithin is at least one of soybean lecithin or egg yolk lecithin.

[0021] Lecithin is a natural substance extracted from plants and animals such as soybeans or egg yolks. It is mainly composed of phosphatidylcholine. The lecithin molecule contains both lipophilic parts in the form of fatty acid groups and hydrophilic groups in the form of phosphoesters. It can be used in industries such as food, nanomedicine and cosmetics to encapsulate various hydrophilic / hydrophobic substances. At the same time, lecithin also has important physiologically active functions, such as clearing blood vessel cholesterol, assisting in lowering blood lipids, protecting the liver and enhancing brain vitality. The present invention uses lecithin as the first coating layer of wheat germ oil, wherein the hydrophobic tail of the lecithin is inserted into the wheat germ oil, and the hydrophilic head is tightly combined in the aqueous phase to form a stable microemulsion. However, microcapsules using lecithin alone as the coating layer are not stable enough, and lecithin itself is easily oxidized, sticky, and not easily soluble in water. Therefore, the present invention adopts a double-layer embedding structure of lecithin and modified starch, and further coats the lecithin layer with a wall composed of modified starch. The anionic phosphate and carboxylic acid groups on the surface of the modified starch can form electrostatic bonds with the hydrophilic head (phosphocholine group) of the lecithin through charge complementarity, forming a stable outer capsule wall layer.

[0022] Preferably, modified starch is selected as the second coating layer. In this coating layer, the modified starch will simultaneously embed and dry the hydrophilic wheat germ polypeptide, Lactobacillus plantarum, Lactobacillus acidophilus and other probiotics.

[0023] The present invention greatly improves the light transmittance and freeze-thaw stability of starch and reduces the gelatinization temperature by modifying natural starch through phospholipidation and acetate esterification, making it more suitable as a capsule wall material for instant cereals. In addition, the binding force between the modified starch wall material and the hydrophilic head of lecithin and the storage stability are greatly improved.

[0024] In a specific application example, the mass ratio of the core material to the inner wall material is 1:(4-8), and the mass ratio of the total mass of the core material and the inner wall material to the outer wall material is 1:(2-6).

[0025] The present invention also protects a method for preparing microencapsulated wheat germ oil, comprising the following steps:

[0026] S1. The wheat germ is cleaned, dried, ground and sieved, and separated by supercritical CO2 extraction technology to obtain wheat germ oil and wheat germ residue. The wheat germ residue is enzymatically hydrolyzed with protease to obtain wheat germ peptides. Lactobacillus plantarum and Lactobacillus acidophilus are pre-activated and washed. The wheat germ oil, wheat germ peptides and distilled water are mixed and emulsified, and Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion and fermented for 20 to 40 hours.

[0027] S2. The fermented wheat germ oil emulsion was mixed with lecithin and homogenized to obtain a lecithin-coated wheat germ oil emulsion;

[0028] S3. Dispersing the modified starch in water, adding the lecithin-coated wheat germ oil emulsion, homogenizing and emulsifying, and then drying to obtain microencapsulated wheat germ oil.

[0029] Preferably, the drying is freeze-drying or spray-drying, and further preferably, the drying is spray-drying.

[0030] Preferably, the inlet and outlet temperatures of the spray drying are 150-180°C and 80-100°C respectively, and the air flow rate is 30-35m 3 / h.

[0031] Beneficial effects

[0032] The present invention provides modified starch for use in microencapsulating wheat germ oil and wheat germ oil thereof, which have the following beneficial effects:

[0033] (1) The light transmittance and freeze-thaw stability of the modified starch were significantly improved, and the gelatinization temperature was significantly reduced, which improved the appearance of the wheat germ oil microcapsules and made them particularly suitable as additives for preparing cereals.

[0034] (2) Supercritical CO2 extraction technology was used to separate wheat germ oil and wheat germ residue containing wheat germ protein, and protease was used to hydrolyze wheat germ protein to obtain water-soluble wheat germ polypeptides, thus realizing high-value processing of wheat germ.

[0035] (3) Wheat germ polypeptide is used as an emulsifier to emulsify wheat germ oil and then ferment it, replacing the use of traditional synthetic emulsifiers, ensuring food safety and improving nutritional value.

[0036] (4) Wheat germ oil was fermented using Lactobacillus plantarum and Lactobacillus acidophilus. The fermentation process and the low pH environment produced by the fermentation effectively reduced and inhibited the activity of lipase and lipoxygenase, slowed down the rate of oxidative rancidity, and thus significantly improved the storage characteristics of wheat germ oil.

[0037] (5) Lecithin was used as the first layer coating on the outer surface of the fermented wheat germ oil, and modified starch was used as the second layer coating. The double-layer encapsulation structure enhanced the stability of the microcapsule structure. Compared with the single-layer coating, the rate of oxidation and rancidity of the wheat germ was further reduced, thereby effectively extending the storage characteristics of the wheat germ.

[0038] (6) Microencapsulated wheat germ oil also contains a variety of nutrients such as wheat germ oil, wheat germ peptides, lecithin, and probiotics, which greatly enhances the nutritional value of wheat germ oil mixed with cereals. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 These are the infrared spectra of corn starch, phosphate starch and modified starch. DETAILED DESCRIPTION

[0040] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0041] Wheat germ: purchased from Shandong Qingdao Jiahexing Flour Milling Co., Ltd.

[0042] Lactobacillus plantarum: GDMCC NO.1.140, purchased from Guangdong Provincial Microbiological Culture Collection Center;

[0043] Lactobacillus acidophilus: GDMCC NO.1.1807, purchased from Guangdong Provincial Microbiological Culture Collection Center;

[0044] Alkaline protease: 200,000 U / g, purchased from Hongrun Baoshun Co., Ltd.

[0045] Papain: 2 million U / g, purchased from Sigma, USA;

[0046] Soybean lecithin: A510030, purchased from Sangon Biotechnology (Shanghai) Co., Ltd.;

[0047] Phosphate: sodium trimetaphosphate, 95%, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0048] Phosphate buffer: 5 mM, pH = 7.2, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.

[0049] Corn starch: Honghu Starch Factory, moisture 13.1%, 100 mesh;

[0050] Preparation Example 1

[0051] A modified starch 1 for use in microencapsulating wheat germ oil (hereinafter referred to as modified starch 1) is prepared as follows:

[0052] 100 g of corn starch was weighed and mixed with 200 ml of a 20% ethanol solution, and stirred uniformly to obtain a starch emulsion. The starch emulsion was ultrasonically treated at 25° C. for 15 minutes at an ultrasonic power of 100 W. 6 g of sodium trimetaphosphate and 3 g of urea were dissolved in 50 ml of a 20% ethanol solution and then added to the ultrasonically treated starch emulsion. 0.5% sodium hydroxide was added to adjust the pH to 9.5, and the mixture was stirred for 30 minutes. The mixture was washed with water, filtered, and vacuum dried to a water content of 20%. The mixture was crushed and sieved, and reacted in a microwave oven at a power of 400 W for 5 minutes to obtain a phosphate starch. The degree of substitution of the phosphoryl group was 0.065 as determined by spectrophotometry.

[0053] Phosphate starch was prepared into a starch milk with a concentration of 40%. A 3% sodium hydroxide solution was added at 30°C to adjust the pH of the starch milk to 8. Acetic anhydride was added dropwise while stirring, and the mixture was balanced for a period of time. A 3% sodium hydroxide solution was then added dropwise to adjust the pH to 8. The above steps were repeated to maintain the pH of the starch milk at an alkaline level until the pH value remained unchanged, and the reaction was terminated. The total amount of acetic anhydride added was 20 g. The solution was neutralized with 0.5% dilute hydrochloric acid to adjust the pH to 5.5-6.5. The mixture was washed three times with water, filtered, vacuum dried, and then crushed through a 100-mesh sieve to obtain a modified starch. The degree of substitution of acetyl groups was determined to be 0.31 by titration.

[0054] The absorption spectra of corn starch, phosphate starch, and modified starch 1 were measured using a NEXUS-470 infrared spectrometer. A small amount of corn starch, phosphate starch, and modified starch 1 were added to a certain amount of fully dried KBr powder and ground thoroughly in an agate mortar under continuous infrared light to mix. An appropriate amount of the fully ground mixture powder was manually pressed into a tablet and placed in an infrared spectrometer. The results were scanned over a range of 4000-500 cm. -1 Scan and obtain the infrared spectrum of the sample, such as Figure 1 As shown in the figure, it can be seen that phosphate starch and modified starch have a higher relative density at 996 cm -1 The peak intensity and width at 470 nm were significantly enhanced, proving the successful insertion of the phosphate group. At the same time, compared with the infrared spectrum of corn starch, the modified starch 1 had a blue shift toward the short-wave direction, which was inferred to be the effect of the acetyl group.

[0055] Preparation Example 2

[0056] A modified starch 2 for microencapsulating wheat germ oil. The preparation method is similar to that of modified starch 1, except that the amount of sodium trimetaphosphate added is 2 g and the amount of urea added is 1 g. The degree of substitution of the phosphoryl group is 0.031 as determined by spectrophotometry.

[0057] Preparation Example 3

[0058] A modified starch 3 for microencapsulating wheat germ oil. The preparation method is similar to that of modified starch 1, except that the amount of sodium trimetaphosphate added is 4 g and the amount of urea added is 2 g. The degree of substitution of the phosphoryl group is 0.053 as determined by spectrophotometry.

[0059] Preparation Example 4

[0060] A modified starch 4 for microencapsulating wheat germ oil is prepared in a method similar to that of modified starch 1, with the difference that the total amount of acetic anhydride added is controlled at 5 g; and the degree of substitution of acetyl groups is determined to be 0.15 by titration.

[0061] Preparation Example 5

[0062] A modified starch 5 for microencapsulating wheat germ oil is prepared in a method similar to that of the modified starch 1, with the difference that the total amount of acetic anhydride added is controlled at 10 g; and the degree of substitution of acetyl groups is determined to be 0.22 by titration.

[0063] The corn starch, phosphate starch and modified starch 1 to 5 of Preparation Examples 1 to 5 were subjected to the following tests, respectively. The results are shown in Table 1:

[0064] (1) Light transmittance: Accurately weigh a certain amount of corn starch, phosphate starch, and modified starch to prepare a 1% starch milk. Measure 50 mL of the 1% starch milk, add it to a 100 mL beaker, place it in a water bath, stir, and heat for 15 minutes, while keeping the total volume of the starch milk unchanged. After heating, cool the starch milk to 25°C, use distilled water as a blank reference, and use a 1 cm glass cuvette to measure the light transmittance of corn starch, phosphate starch, and modified starch with a spectrophotometer at a wavelength of 620 nm;

[0065] (2) Freeze-thaw stability: 3 g (dry basis) of starch sample was accurately weighed and prepared into a 3% starch milk. The mixture was heated in a boiling water bath for 20 min while maintaining the volume. After sufficient gelatinization, the mixture was cooled to 25°C. 30 mL of the starch paste was added to a plastic cup with a lid and placed in a refrigerator at -18°C. After freezing for 24 h, the mixture was taken out and thawed naturally at room temperature. The thawing status of the starch paste was observed and the weight of the clear water precipitated from the starch gel was measured. The sample with the upper layer of clear water removed was then placed in a refrigerator at -18°C. The above operation was repeated 5 times. The ratio of the weight of the total precipitated clear water to the total starch paste was calculated.

[0066] (3) Gelatinization temperature: Carefully place 15 mg of sample in an aluminum box and add a few microliters of water using a needle. The starch:water ratio is approximately 1:3. The prepared sample is allowed to stand at room temperature for 2 h. The sample is then analyzed in a differential scanning calorimeter. The scanning range is 40–100°C, the scanning rate is 5°C / min, the atmosphere is high-purity nitrogen, and the flow rate is 30 mL / min.

[0067] Table 1 Physicochemical properties of corn starch, phosphate starch and modified starch

[0068]

[0069] This indicates that starch modified with dual phosphate and acetic acid exhibits significantly improved light transmittance and freeze-thaw stability, while simultaneously reducing its gelatinization temperature, making it particularly suitable for use as a capsule wall material for wheat germ oil. Furthermore, the degree of substitution with phosphoric acid and acetic acid directly impacts its light transmittance, water absorption rate, and gelatinization temperature. When the degree of substitution with either phosphoric acid or acetic acid is too low, light transmittance is low, while water absorption and gelatinization temperature are high.

[0070] Application Example 1

[0071] A microencapsulated wheat germ oil, the preparation method of which is as follows:

[0072] S1. After cleaning and removing impurities from the wheat germ, the wheat germ was dried in a desktop drying oven at 65°C with a layer thickness of 2-3 cm for 24 h. After removal, the wheat germ was crushed with a disc mill and sieved with a 20-mesh standard sieve to remove the fine powder. The wheat germ was extracted using a HA121-50-01 (02) supercritical CO2 extraction device. The specific operating parameters were: supercritical pressure 30 MPa, furnace temperature 35°C, output valve temperature 100°C, and extraction for 3.5 h to separate wheat germ oil and wheat germ residue.

[0073] Lactobacillus plantarum and Lactobacillus acidophilus were activated and cultured in a broth at 37°C for 24 h until the cell concentration reached 1×10 9 cfu / ml or more, centrifuge at 4°C for 15 min using a tabletop refrigerated centrifuge, remove the supernatant, wash the microbial pellet with sterile saline solution in a sterile bottle, centrifuge again, and repeat the washing and centrifugation three times to remove the broth;

[0074] Wheat germ residue is dispersed in distilled water to prepare a wheat germ residue suspension with a substrate concentration of 2%, alkaline protease and papain are added at a concentration of 4000 U / g substrate, the temperature is adjusted to 50°C, a 3% NaOH solution is added to adjust the pH to 8, the mixture is mixed and enzymatically hydrolyzed for 3 hours, the enzyme is inactivated in a boiling water bath for 10 minutes, and after cooling, 0.5% dilute hydrochloric acid is added to adjust the pH to 4.0, the mixture is centrifuged at 5000 r / min for 15 minutes, the supernatant is adjusted to a pH of 7.0, and the mixture is freeze-dried to obtain wheat germ polypeptides;

[0075] 20 g of wheat germ oil, 2 g of wheat germ polypeptide and 1 L of distilled water were homogenized and emulsified at 6000 rpm using a high-pressure homogenizer (pilot-scale high-pressure homogenizer PHA-0601, Ningbo Xinzhi Technology Co., Ltd.) to obtain a wheat germ oil emulsion. The wheat germ oil emulsion was inoculated with 1% v / v of Lactobacillus plantarum and Lactobacillus acidophilus, shaken thoroughly and incubated at 37°C for 24 hours.

[0076] S2. 140 g of soy lecithin powder was homogenized with 1 L of distilled water at a speed of 6000 r / min for 2 min, mixed with the fermented wheat germ emulsion obtained in step S1, and homogenized using a high-pressure homogenizer at 6000 r / min for 1 min to obtain a lecithin - wheat germ oil emulsion;

[0077] S3. 480 g of modified starch 1 was dissolved in 4.8 L of distilled water. The mixture was then added to the lecithin-wheat germ oil emulsion obtained in step S2 and homogenized at 8000 rpm for 5 min. The mixture was then spray-dried using a spray dryer (B290, Buchi Laboratoriums-Technik) with inlet and outlet temperatures of 180°C and 100°C, respectively, and an air flow rate of 35 m / s. 3 / h, collect the dried sample to obtain microencapsulated wheat germ oil.

[0078] It should be noted that, unless otherwise specified, semi-finished products such as wheat germ oil and wheat germ polypeptide need to be stored at -10°C to 4°C for future use. The water used in this plan is distilled water or ultrapure water.

[0079] Application Example 2

[0080] Compared with Application Example 1, the difference lies in that the mass ratio of Lactobacillus plantarum to Lactobacillus acidophilus is 3:1.

[0081] Application Examples 3-6

[0082] Compared with Application Example 1, the difference is that in step S3, modified starch 1 is replaced by modified starches 2 to 5.

[0083] Comparative Example 1

[0084] Compared with Application Example 1, the difference is that the wheat germ oil is not subjected to fermentation treatment.

[0085] Comparative Example 2

[0086] Compared with Application Example 1, the difference is that step S2 is not performed.

[0087] Comparative Example 3

[0088] Compared with Application Example 1, the difference is that step S3 is not performed.

[0089] Comparative Example 4

[0090] Compared with Application Example 1, the difference is that in step S3, the modified starch 1 is replaced by corn starch.

[0091] Performance Testing

[0092] The wheat germ oils prepared in the application examples and comparative examples were subjected to the following tests and the results are shown in Table 2:

[0093] 1. Lipase Activity: After weighing a certain amount of the prepared microcapsules, sodium acetate buffer, magnesium chloride, p-nitrophenyl phosphate, and distilled water were added in sequence. The mixture was placed in a constant temperature water bath and incubated at 37°C for 5 minutes. Potassium hydroxide was then added to terminate the reaction, and the absorbance was measured at a wavelength of 405 nm using a spectrophotometer (Model T80, PG Instruments, UK). Enzyme activity was calculated according to the following formula:

[0094] Enzyme activity (U / g) = [(Asample - Ablank) × V × D] / (ε × t × m), where: Asample is the absorbance of the sample, Ablank is the absorbance of the blank, V is the total volume of the reaction system, D is the dilution factor, ε is the molar extinction coefficient of p-nitrophenol, t is the reaction time (minutes), and m is the sample mass (g);

[0095] 2. Determination of fatty acid value under accelerated storage conditions: The microcapsule samples were stored in an oven at 60°C for 60 days. Samples were taken every 3 days and the fatty acid value of the samples was determined according to GB / T 15684-2015.

[0096] Table 2 Performance test results of application examples and comparative examples

[0097] Lipase activity (U / g) Fatty acid value (mgKOH / 100g) Application Example 1 0.15 52.11 Application Example 2 0.43 68.61 Application Example 3 0.36 72.95 Application Example 4 0.23 64.15 Application Example 5 0.31 71.02 Application Example 6 0.18 61.88 Comparative Example 1 1.25 112.63 Comparative Example 2 0.56 84.21 Comparative Example 3 0.84 102.15 Comparative Example 4 0.59 96.24

[0098] It can be seen from the data of the application examples and comparative examples that the oxidative rancidity rate of the wheat germ microcapsules after fermentation and double-layer embedding structure is significantly reduced, thereby improving its storage performance.

[0099] The preferred application examples disclosed above are intended only to help illustrate the present invention. These preferred application examples do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and variations are possible based on the contents of this specification. These application examples are selected and specifically described in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention. The present invention is limited only by the claims and their full scope and equivalents.

Claims

1. A microencapsulated wheat germ oil, characterized in that The microencapsulated wheat germ oil has a double-layer embedding structure; the core material includes wheat germ oil, Lactobacillus plantarum, Lactobacillus acidophilus and wheat germ polypeptides; the inner wall material includes lecithin; the outer wall material includes modified starch, wherein the modified starch is starch esterified with phosphoric acid and acetate, and the phosphoryl substitution degree of the modified starch is 0.03-0.07, and the acetyl substitution degree of the modified starch is 0.1-0.5; the preparation method of the core material is as follows: wheat germ is separated by supercritical CO2 extraction technology to obtain wheat germ oil and wheat germ residue, the wheat germ residue is enzymatically hydrolyzed by using protease to obtain wheat germ polypeptides, the wheat germ oil, wheat germ polypeptides and distilled water are mixed and emulsified homogeneously, and then pre-activated Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion and fermented for 20-40 hours.

2. Microencapsulated wheat germ oil as claimed in claim 1, is characterized in that, The preparation method of the modified starch comprises the following steps: S1. Corn starch and ethanol solution are mixed to obtain starch emulsion, which is ultrasonically treated. Phosphate, urea, and sodium hydroxide are added to adjust the pH to 9-11. The mixture is stirred for a period of time, washed with water, dried to a moisture content of 10-20%, crushed and sieved, and microwaved for 3-8 minutes to obtain phosphate starch. S2. Phosphate starch is mixed with deionized water to obtain starch milk, sodium hydroxide solution is added under stirring at 25-40°C to adjust the pH of the starch milk to 8-8.5, acetic anhydride is added dropwise, and the mixture is equilibrated for a period of time. Then, sodium hydroxide solution is added dropwise to adjust the pH to 8-8.

5. The above steps are repeated to maintain the pH of the starch milk at an alkaline level until the pH value remains unchanged, and the reaction is terminated. The solution is neutralized with dilute acid to adjust the pH to 5.5-6.5, washed with water, dried to a water content of 10-20%, and crushed and sieved to obtain modified starch.

3. Microencapsulated wheat germ oil as claimed in claim 2, is characterized in that, The phosphate is at least one of sodium tripolyphosphate, sodium trimetaphosphate, and sodium pyrophosphate.

4. Microencapsulated wheat germ oil as claimed in claim 1, is characterized in that, The bacterial concentration of the plant lactobacillus and the acidophilus lactobacillus after pre-activation is 1×10 9 ~9×10 9 cfu / ml, the inoculation amount is 0.5-3v / v%, and the mass ratio of Lactobacillus plantarum to Lactobacillus acidophilus is (1-3):

1.

5. Microencapsulated wheat germ oil as claimed in claim 1, is characterized in that, The protease is alkaline protease and papain in a mass ratio of (1-3): (1-3).

6. Microencapsulated wheat germ oil as claimed in claim 1, characterized in that, The mass ratio of the wheat germ oil to the wheat germ polypeptide is 100:(2-5).

7. The microencapsulated wheat germ oil according to claim 1, wherein The mass ratio of the core material to the inner wall material is 1:(4-8), and the mass ratio of the total mass of the core material and the inner wall material to the outer wall material is 1:(2-6).

8. The method for preparing microencapsulated wheat germ oil according to any one of claims 1 to 7, wherein: The following steps are involved: S1. The wheat germ is cleaned, dried, ground and sieved, and separated by supercritical CO2 extraction technology to obtain wheat germ oil and wheat germ residue. The wheat germ residue is enzymatically hydrolyzed with protease to obtain wheat germ peptides. Lactobacillus plantarum and Lactobacillus acidophilus are pre-activated and washed. The wheat germ oil, wheat germ peptides and distilled water are mixed and emulsified, and Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion and fermented for 20 to 40 hours. S2. The fermented wheat germ oil emulsion was mixed with lecithin and homogenized to obtain a lecithin-coated wheat germ oil emulsion; S3. Dispersing the modified starch in water, adding the lecithin-coated wheat germ oil emulsion, homogenizing and emulsifying, and then drying to obtain microencapsulated wheat germ oil.

Images