Modified starch applied to microencapsulation of wheat germ oil and wheat germ oil thereof

Abstract

The invention discloses modified starch applied to microencapsulated wheat germ oil and the wheat germ oil thereof, and belongs to the technical field of brewing cereal products. The modified starch is phosphoric acid and acetic acid esterified starch, 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 microencapsulated wheat germ oil is of a double-layer embedding structure; the core material comprises wheat germ oil, lactobacillus plantarum, lactobacillus acidophilus and wheat germ polypeptide, the inner-layer wall material comprises lecithin, and the outer-layer wall material comprises modified starch. Modified starch with high light transmittance, high freeze-thaw stability and low gelatinization temperature is prepared and applied to preparation of the microencapsulated wheat germ oil, the wheat germ oil is treated through a lactobacillus biological fermentation method, and then the wheat germ oil, lecithin and the modified starch are prepared into the microcapsule wheat germ oil of a double-layer embedding structure. Therefore, the nutritional value and the storage quality guarantee period of the wheat germ oil are effectively improved.

Description

Technical Field

[0001] The present invention relates to the technical field of instant cereal products, and particularly to a modified starch applied to microencapsulated wheat germ oil and wheat germ oil. Background Art

[0002] Starch is a natural polymer, which has the advantages of easy regeneration, low price, good biocompatibility, etc., and is suitable as a carrier material for the delivery of bioactive substances. Natural starch has many advantages as a microcapsule wall material, such as low cost and good biocompatibility, but at the same time, it has defects such as low transparency and poor freeze-thaw stability, which to a certain extent limit its application in the field of microcapsule technology.

[0003] Wheat is the main food crop of humans and is widely planted all over the world. Wheat germ is a by-product generated during wheat processing, and its content accounts for about 3% of wheat grains. Wheat germ is rich in carbohydrates (accounting for 42% - 47%), the main components are sucrose and pentosan, with less starch content, and is more nutritious than other carbohydrates. The protein content is about 30%, and among them, wheat germ protein is a high-quality complete protein nutrient source; the content of unsaturated fatty acids is about 84%, and the content of linoleic acid is about 52.31%. Linoleic acid is an essential fatty acid that the human body cannot synthesize by itself and can only be ingested through food. Wheat germ is widely used in health foods due to its nutritional characteristics and has the laudatory name of "the natural nutritional treasure house of humans". Wheat germ oil is obtained from wheat germ and contains rich nutrients such as polyunsaturated fatty acids, tocopherols, and phytosterols, and has functions such as antioxidation and anti-fatigue, and is widely used in the field of medical and health care as a high-end edible oil.

[0004] The quality indicators of wheat germ oil, such as acid value and peroxide value, are greatly affected by extraction technology, refining process, and storage conditions. The free fatty acid content of fresh germ oil is 6.0% - 7.5%. Some studies have found that the acid value of wheat germ oil rises from 14.88 mg / g to 23.46 mg / g during periodic storage, and at 70 °C, the lipase activity is inhibited, and the acid value drops from 14.88 mg / g to 12.02 mg / g, indicating that the acid value can reach an appropriate value by controlling the temperature to inhibit lipase activity. Another study shows that lipase can be inactivated by radiation to reduce the acid value and achieve the purpose of extending the shelf life of wheat germ oil. In addition, during the refining process of wheat germ oil, the alkali refining and deacidification process can reduce the acid value of the oil by combining caustic soda solution with free fatty acids in crude oil. However, the lipase in wheat germ has strong stability. Even when heat-treated at 60 - 90 °C for 1 h, it can still maintain more than 20% of the residual activity. Therefore, it is still necessary to develop a modified starch applicable to microencapsulated wheat germ oil and a deep processing method for wheat germ. Summary of the Invention

[0005] In order to overcome the deficiencies of the above-mentioned existing technologies, the object of the present invention is to provide a modified starch applied to microencapsulated wheat germ oil and the wheat germ oil.

[0006] The technical solution for achieving the object of the present invention is as follows:

[0007] A modified starch applied to microencapsulated wheat germ oil, wherein the modified starch is a phosphoric acid and acetic acid esterified starch, the degree of substitution of phosphonyl groups of the modified starch is 0.03-0.07, and the degree of substitution of acetyl groups is 0.1-0.5.

[0008] Preferably, the preparation method of the modified starch includes the following steps:

[0009] S1. Corn starch is mixed with an ethanol solution to obtain a starch milk, ultrasonically treated, phosphate, urea and sodium hydroxide are added to adjust the pH to 9-11, stirred and reacted for a period of time, washed with water and dried to a water content of 10-20%, crushed and sieved, and microwave-treated for 3-8 minutes to obtain phosphate ester starch;

[0010] S2. The phosphate ester starch is mixed with deionized water to obtain a starch milk, the pH of the starch milk is adjusted to 8-8.5 by adding a sodium hydroxide solution under stirring conditions at 25-40 °C, acetic anhydride is added dropwise, balanced for a period of time, and then a sodium hydroxide solution is added dropwise to adjust the pH to 8-8.5. Repeat the above steps to keep the pH value of the starch milk alkaline until the reaction ends when the pH value remains unchanged. The solution is neutralized with dilute acid, the pH is adjusted to 5.5-6.5, washed with water and dried to a water content of 10-20%, crushed and sieved to obtain the 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 degree of substitution of phosphonyl groups of the modified starch is 0.05-0.07, and the degree of substitution of acetyl groups is 0.18-0.32.

[0014] In a specific application example, the preparation method of the core material is as follows: Wheat germ oil and wheat germ residue are separated by supercritical CO2 extraction technology, the wheat germ residue is enzymatically hydrolyzed with protease to obtain wheat germ polypeptide, after mixing and homogenizing and emulsifying wheat germ oil, wheat germ polypeptide and distilled water, pre-activated Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion and fermented for 20-40 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 0.5~3 v / v%, and the mass ratio of Lactobacillus plantarum to Lactobacillus acidophilus is (1~3):1.

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

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

[0018] The extraction of wheat germ oil by supercritical CO2 extraction technology not only avoids the solvent residue problem in traditional methods, but also significantly improves the extraction efficiency, and at the same time better retains the nutritional components in wheat germ oil. However, a large amount of protein (30%~35%) remains in the wheat germ residue after extraction. Among them, wheat germ protein has high antioxidant activity and can be used as a bioactive ingredient in healthy foods. If it is directly discarded as waste residue, it will cause great waste of resources. Therefore, in the present invention, protease is used to further enzymatically hydrolyze the wheat germ residue to extract water-soluble wheat germ polypeptide, and it is used as an emulsifier for wheat germ oil, so that wheat germ oil can form a homogeneous emulsion, which is convenient for the subsequent fermentation step, thereby replacing the synthetic emulsifier (such as Tween) required for the original wheat germ oil emulsification and ensuring food safety.

[0019] During the fermentation of wheat germ oil, the fermentation and the low pH environment generated by fermentation can greatly reduce the activities of lipase and lipoxygenase, thereby reducing the speed of sensory quality deterioration such as rancidity caused by free fatty acids generated by the enzymatic hydrolysis of lipase in wheat germ oil, and greatly improving its storage characteristics. However, lactic acid bacteria produce lactic acid during fermentation, resulting in a low pH environment, which is not conducive to the maintenance of the vitality of lactic acid bacteria. Therefore, in the present invention, Lactobacillus acidophilus and Lactobacillus plantarum are selected to jointly ferment wheat germ oil, so as to ensure the vitality of lactic acid bacteria.

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

[0021] Lecithin is a natural substance extracted from plants and animals such as soybeans or egg yolks, mainly composed of phosphatidylcholine. The lecithin molecule contains both a lipophilic part in the form of a fatty acid group and a hydrophilic group in the form of a phosphoester group. It can be used in industries such as food, nanomedicine, and cosmetics to encapsulate various hydrophilic / lipophilic substances. At the same time, lecithin also has important physiological and active functions, such as removing cholesterol from blood vessels, assisting in reducing blood lipids, protecting the liver, and enhancing brain vitality. In the present invention, lecithin is used as the first coating layer of wheat germ oil. The hydrophobic tail of lecithin inserts into the wheat germ oil, and the hydrophilic head tightly binds in the aqueous phase to form a stable microemulsion. However, the microcapsule with only lecithin as the coating layer is not stable enough, and lecithin itself is prone to oxidation, adhesion, and is not easily soluble in water. Therefore, the present invention adopts a double-layer embedding structure of lecithin and modified starch, and a wall composed of modified starch is coated outside the lecithin layer. The anionic phosphate and carboxylic acid groups on the surface of the modified starch can form electrostatic binding with the hydrophilic head (phosphocholine group) of lecithin through charge complementarity to form 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 encapsulate and dry hydrophilic wheat germ polypeptides, probiotics such as Lactobacillus plantarum and Lactobacillus acidophilus.

[0023] In the present invention, by subjecting natural starch to phosphatization and acetylation modification, the light transmittance and freeze-thaw stability of the starch are greatly improved, and the gelatinization temperature is reduced, making it more suitable as the wall material of instant cereals. Moreover, the binding force and storage stability between the modified starch wall material and the hydrophilic head of lecithin 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 preparation method of microencapsulated wheat germ oil, comprising the following steps:

[0026] S1. Clean, dry, grind, and sieve wheat germ, and use supercritical CO2 extraction technology to separate wheat germ oil and wheat germ residue. Use protease to enzymatically hydrolyze the wheat germ residue to obtain wheat germ polypeptides. Pre-activate and wash Lactobacillus plantarum and Lactobacillus acidophilus. After mixing and homogenizing wheat germ oil, wheat germ polypeptides, and distilled water, inoculate Lactobacillus plantarum and Lactobacillus acidophilus into the wheat germ oil emulsion and ferment for 20 - 40 hours;

[0027] S2. Mix the fermented wheat germ oil emulsion with lecithin and homogenize to obtain a lecithin-coated wheat germ oil emulsion;

[0028] S3. Disperse the modified starch in water, add the lecithin-coated wheat germ oil emulsion, homogenize and emulsify, and then dry 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 - 35 m 3 / h.

[0031] Beneficial effects

[0032] The present invention provides a modified starch and its wheat germ oil applied to microencapsulated wheat germ oil, having the following beneficial effects:

[0033] (1) The light transmittance and freeze-thaw stability of the modified starch are significantly improved, and the gelatinization temperature is significantly decreased, improving the appearance of the wheat germ oil microcapsules, and is particularly suitable as an additive for instant cereals.

[0034] (2) The wheat germ oil and the wheat germ residue containing wheat germ protein are separated by using the supercritical CO2 extraction technology, and the wheat germ protein is hydrolyzed by protease to obtain water-soluble wheat germ polypeptides, realizing the high-value utilization of wheat germ.

[0035] (3) Using wheat germ polypeptides as emulsifiers to emulsify wheat germ oil and then fermenting, replacing the use of traditional synthetic emulsifiers, ensuring food safety and improving nutritional value.

[0036] (4) Using Lactobacillus plantarum and Lactobacillus acidophilus to ferment wheat germ oil, the fermentation process and the low pH environment generated by fermentation effectively reduce and inhibit the activities of lipase and lipoxygenase, slowing down its oxidation and rancidity rate, thereby significantly improving the storage characteristics of wheat germ oil.

[0037] (5) Using lecithin for the first layer coating on the outer surface of the fermented wheat germ oil, and using modified starch as the second layer coating, the double-layer embedding structure enhances the stability of the microcapsule structure. Compared with single-layer coating, the oxidation and rancidity rate of wheat germ is further decreased, thereby effectively extending the storage characteristics of wheat germ.

[0038] (6) The microencapsulated wheat germ oil also contains various nutritional components such as wheat germ oil, wheat germ polypeptides, lecithin, probiotics, etc., greatly improving the nutritional value of wheat germ oil for instant cereals. Description of the drawings

[0039] Figure 1 It is the infrared spectrogram of corn starch, phosphate starch and modified starch. Detailed implementation mode

[0040] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work belong to the scope of protection of the present invention.

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

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

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

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

[0045] Papain: 2,000,000 U / g, purchased from Sigma Company, USA;

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

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

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

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

[0050] Preparation Example 1

[0051] A modified starch 1 (hereinafter referred to as modified starch 1) applied to microencapsulated wheat germ oil, the preparation method is as follows:

[0052] Weigh 100 g of corn starch and mix it evenly with 200 ml of 20% ethanol solution to obtain a starch milk. Ultrasonically treat the starch milk at 25 °C for 15 minutes with an ultrasonic power of 100 W. Dissolve 6 g of sodium trimetaphosphate and 3 g of urea in 50 ml of 20% ethanol solution, then add it to the ultrasonically treated starch milk. Add 0.5% sodium hydroxide to adjust the pH to 9.5, stir for 30 min, wash with water, filter by suction, vacuum dry until the water content is 20%, crush and sieve, and react in a microwave oven at a power of 400 W for 5 min to obtain phosphate starch; the degree of substitution of phosphoryl groups is measured by spectrophotometry to be 0.065.

[0053] Prepare a starch milk with a concentration of 40% from the phosphate starch. Add 3% sodium hydroxide solution at 30 °C to adjust the pH of the starch milk to 8. While stirring, dropwise add acetic anhydride, balance for a period of time, then add 3% sodium hydroxide solution to adjust the pH to 8. Repeat the above steps to keep the pH value of the starch milk alkaline until the reaction ends when the pH value remains unchanged. The total amount of acetic anhydride added is 20 g. Neutralize the solution with 0.5% dilute hydrochloric acid, adjust the pH to 5.5 - 6.5, wash three times with water, filter by suction, vacuum dry, and then crush and sieve through a 100-mesh sieve to obtain modified starch. The degree of substitution of acetyl groups is measured by titration to be 0.31.

[0054] Use a NEXUS-470 infrared spectrometer to measure the absorption spectra of corn starch, phosphate starch, and modified starch 1. Add a small amount of corn starch, phosphate starch, and modified starch 1 to a certain amount of thoroughly dried KBr powder respectively, and grind them thoroughly in an agate mortar under continuous irradiation of an infrared lamp to make them evenly mixed. Take an appropriate amount of the thoroughly ground mixture powder, after manual tabletting, place it in the infrared spectrometer, and scan in the scanning range of 4000 - 500 cm -1 for scanning to obtain the infrared spectrogram of the sample, as Figure 1 shown. It can be seen from the figure that the peak intensity and width of the phosphate starch and modified starch at 996 cm -1 are significantly enhanced compared with those of corn starch, proving the successful incorporation of phosphate groups. At the same time, compared with the infrared spectrum of corn starch, the infrared spectrum of modified starch 1 shows a blue shift towards the short-wave direction, presumably due to the influence of acetyl groups.

[0055] Preparation Example 2

[0056] A modified starch 2 applied to microencapsulated wheat germ oil. The preparation method is different from that of modified starch 1 in that the addition amount of sodium trimetaphosphate is 2 g and the addition amount of urea is 1 g; the degree of substitution of phosphoryl groups is measured by spectrophotometry to be 0.031;

[0057] Preparation Example 3

[0058] A modified starch 3 applied to microencapsulated wheat germ oil. Compared with the preparation method of modified starch 1, the difference is that the addition amount of sodium trimetaphosphate is 4 g and the addition amount of urea is 2 g; the degree of substitution of phosphoryl groups is measured by spectrophotometry to be 0.053;

[0059] Preparation Example 4

[0060] A modified starch 4 applied to microencapsulated wheat germ oil. Compared with the preparation method of modified starch 1, the difference is that the total addition amount of acetic anhydride is controlled at 5 g; the degree of substitution of acetyl groups is measured by titration to be 0.15.

[0061] Preparation Example 5

[0062] A modified starch 5 applied to microencapsulated wheat germ oil. Compared with the preparation method of modified starch 1, the difference is that the total addition amount of acetic anhydride is controlled at 10 g; the degree of substitution of acetyl groups is measured by titration to be 0.22.

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

[0064] (1) Transmittance: Weigh accurately a certain amount of corn starch, phosphate starch and modified starch, and 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 min, and keep the total volume of the starch milk unchanged. After heating, cool the starch milk to 25°C. Using distilled water as a blank reference, use a 1 cm glass cuvette to measure the transmittance of corn starch, phosphate starch and modified starch at a wavelength of 620 nm with a spectrophotometer;

[0065] (2) Freeze - thaw stability: Weigh accurately 3 g (dry basis) of the starch sample, prepare a 3% starch milk, heat it in a boiling water bath for 20 min, keep the volume unchanged, and after full gelatinization, cool it to 25°C. Take 30 mL of the above - mentioned starch paste and add it to a plastic cup with a lid, place it in a refrigerator at - 18°C, freeze for 24 h and then take it out, thaw naturally at room temperature, observe the thawing condition of the starch paste, measure the weight of the clear water separated out from the starch gel, and then place the sample after removing the upper - layer clear water in a refrigerator at - 18°C, repeat the above operation 5 times, and calculate the ratio of the total weight of the separated clear water to the total starch paste;

[0066] (3) Gelatinization temperature: Carefully place 15 mg of the sample in an aluminum box, add a few microliters of water with a syringe. Make the mass ratio of starch to water about 1:3, place the prepared sample at room temperature for 2 h, and then put the sample into a differential scanning calorimeter for analysis. Scanning range: 40 - 100°C, scanning rate: 5°C / min, atmosphere: high - purity nitrogen, flow rate: 30 mL / min.

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

[0068]

[0069] It can be seen that after double esterification modification with phosphate and acetic acid, the light transmittance and freeze-thaw stability of the starch are significantly improved, while the gelatinization temperature is reduced, which is particularly suitable as the wall material for wheat germ oil. And the substitution degrees of phosphoric acid and acetic acid have a direct impact on its light transmittance, water separation rate and gelatinization temperature. When the substitution degree of phosphoric acid or acetic acid is too small, its light transmittance is low, and the water absorption rate and gelatinization temperature are high.

[0070] Application Example 1

[0071] A microencapsulated wheat germ oil, and its preparation method is as follows:

[0072] S1. After cleaning and removing impurities from wheat germ, it is dried in a bench drying oven at 65 °C for 24 h under the condition of a material layer thickness of 2 - 3 cm. After taking it out, it is pulverized with a disk mill and the too fine powder is removed with a 20-mesh standard sieve. The wheat germ is extracted with a HA121-50-01(02) type supercritical CO2 extraction equipment. The specific operation parameters are: supercritical pressure 30 Mpa, furnace temperature 35 °C, output valve temperature 100 °C. After extraction for 3.5 h, wheat germ oil and wheat germ residue are separated;

[0073] Lactobacillus plantarum and Lactobacillus acidophilus with a mass ratio of 1:1 are activated and cultured in broth at 37 °C for 24 h until the cell concentration is above 1×10 9 cfu / ml. It is centrifuged at 4 °C for 15 min using a bench top refrigerated centrifuge, the supernatant is removed, and the microbial precipitate is washed with a sterile saline solution in a sterile bottle, and then centrifuged again. Washing and centrifuging are repeated 3 times to remove the broth;

[0074] The wheat germ residue is taken and dispersed in distilled water to prepare a wheat germ residue suspension with a substrate concentration of 2%. Alkaline protease and papain with a concentration of 4000 U / g substrate are added, the temperature is adjusted to 50 °C, and the pH is adjusted to 8 by adding 3% NaOH solution. The mixture is enzymatically hydrolyzed evenly for 3 h, inactivated by boiling water bath for 10 min, cooled, and the pH is adjusted to 4.0 by adding 0.5% dilute hydrochloric acid. It is centrifuged at 5000 r / min for 15 min, the supernatant is taken and adjusted to pH 7.0, and then freeze-dried to obtain wheat germ polypeptide;

[0075] Take 20 g of wheat germ oil, 2 g of wheat germ polypeptide and 1 L of distilled water, and use a high-pressure homogenizer (pilot-scale high-pressure homogenizer PHA-0601, Ningbo Xinzhi Technology Co., Ltd.) to homogenize and emulsify at a speed of 6000 r / min to obtain a wheat germ oil emulsion. Inoculate Lactobacillus plantarum and Lactobacillus acidophilus with a volume ratio of 1% v / v in the wheat germ oil emulsion, shake well and incubate at 37 °C for 24 hours;

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

[0077] S3. Dissolve 480 g of modified starch 1 in 4.8 L of distilled water, mix the two, add the lecithin-wheat germ oil emulsion obtained in step S2, homogenize at 8000 r / min for 5 min, and use a spray dryer (B290, Buchi Laboratoriums-Technik) for spray drying. The inlet and outlet temperatures are 180 °C and 100 °C respectively, and the air flow rate is 35 m 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 for standby under the conditions of -10 °C to 4 °C, and the water used in this scheme is all distilled water or ultrapure water.

[0079] Application Example 2

[0080] Compared with Application Example 1, the difference is that the mass ratio of Lactobacillus plantarum and 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 2-5.

[0083] Comparative Example 1

[0084] Compared with Application Example 1, the difference is that the wheat germ oil is not fermented.

[0085] Comparative Example 2

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

[0087] Comparative Example 3

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

[0089] Comparative Example 4

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

[0091] Performance test

[0092] The wheat germ oil prepared in the application example and the comparative example was subjected to the following detections and tests, and the results are shown in Table 2 respectively:

[0093] 1. Lipase activity: After weighing a certain weight of the prepared microcapsules, sodium acetate buffer solution, magnesium chloride, p-nitrophenyl phosphate and distilled water were added in sequence, and placed in a constant temperature water bath at 37 °C for incubation for 5 minutes. Subsequently, potassium hydroxide was added to terminate the reaction, and the absorbance was measured at a wavelength of 405 nm using a spectrophotometer (model T80, PG Instruments, UK). The enzyme activity can be calculated according to the following formula:

[0094] Enzyme activity (U / g) = [(A sample - A blank) × V × D] / (ε × t × m), where: A sample is the absorbance of the sample, A blank is the absorbance of the blank sample, 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 sample was stored in an oven at 60 °C for a storage period of 60 days. Samples were taken every 3 days, and the fatty acid value of the sample was determined according to GB / T 15684-2015.

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

[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 example and the comparative example that the oxidative rancidity rate of the wheat germ microcapsules with fermentation and double-layer embedding structure has decreased significantly, thus improving its storage performance.

[0099] The preferred application examples of the present invention disclosed above are only used to help illustrate the present invention. The preferred application examples do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. Obviously, many modifications and changes can be made according to the content of this specification. These application examples are selected and specifically described to better explain the principle and practical application of the present invention, so that those skilled in the art in the relevant technical field can understand and utilize the present invention well. The present invention is only limited by the claims and their full scope and equivalents.

Claims

1. A modified starch for use in microencapsulating wheat germ oil, characterized in that: 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.

2. The modified starch according to claim 1, 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 milk, which is ultrasonically treated, phosphate, urea and sodium hydroxide are added to adjust the pH to 9-11, stirred for a period of time, washed with water and dried to a moisture content of 10-20%, crushed and sieved, and microwaved for 3-8 minutes to obtain phosphate starch; S2. Mix phosphate starch with deionized water to obtain starch milk, add sodium hydroxide solution under stirring at 25-40° C. to adjust the pH value of the starch milk to 8-8.5, add acetic anhydride dropwise, balance for a period of time, then add sodium hydroxide solution dropwise to adjust the pH value to 8-8.5, repeat the above steps to keep the pH value of the starch milk alkaline, and terminate the reaction when the pH value remains unchanged, neutralize the solution with dilute acid, adjust the pH value to 5.5-6.5, wash with water and dry to a water content of 10-20%, grind and sieve to obtain modified starch.

3. The modified starch according to claim 2, characterized in that The phosphate is at least one of sodium tripolyphosphate, sodium trimetaphosphate and sodium pyrophosphate.

4. A microencapsulated wheat germ oil, characterized in that 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, and the modified starch is the modified starch described in any one of claims 1 to 3.

5. Microencapsulated wheat germ oil as claimed in claim 4, characterized in that, 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 hydrolyzed by protease to obtain wheat germ polypeptide, the wheat germ oil, wheat germ polypeptide and distilled water are mixed and emulsified, and pre-activated Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion for fermentation for 20 to 40 hours.

6. Microencapsulated wheat germ oil as claimed in claim 5, 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.

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

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

9. Microencapsulated wheat germ oil as claimed in claim 5, characterized in that, 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 mass ratio of the outer wall material is 1:(2-6).

10. A method for preparing microencapsulated wheat germ oil, characterized in that: 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 hydrolyzed by protease to obtain wheat germ polypeptides, Lactobacillus plantarum and Lactobacillus acidophilus are pre-activated and washed, the wheat germ oil, wheat germ polypeptides and distilled water are mixed and homogenized and emulsified, and Lactobacillus plantarum and Lactobacillus acidophilus are inoculated into the wheat germ oil emulsion for fermentation 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. Disperse the modified starch in water, add the lecithin-coated wheat germ oil emulsion, homogenize and emulsify, and then dry to obtain microencapsulated wheat germ oil.

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