Heat-resistant lonicera caerulea pomace extract microcapsule, preparation method, application and biscuit

Abstract

The invention relates to the technical field of lonicera caerulea pomace, and particularly discloses heat-resistant lonicera caerulea pomace extract microcapsules, a preparation method, application and biscuits. According to the heat-resistant lonicera caerulea pomace extract microcapsule, the mass loss of the microcapsule does not exceed 20% at the temperature of 120-270 DEG C. The preparation method comprises the following steps: S1, adding a wall material into water, and uniformly stirring to obtain a microcapsule wall material solution; s2, slowly adding the core material into the wall material solution, uniformly stirring and mixing the wall material solution and the core material, and performing spray drying to obtain the lonicera caerulea pomace extract microcapsule. In addition, the invention also provides an application of the heat-resistant lonicera caerulea pomace extract microcapsule in baked products and a biscuit added with the lonicera caerulea pomace extract microcapsule. The heat-resistant lonicera caerulea pomace extract microcapsule prepared by the invention has the advantages of low water content and water activity, good color and storage stability and the like, and can keep bright color after being added into biscuits for baking.

Description

Technical Field

[0001] The present application relates to the technical field of blueberry fruit pomace, and particularly relates to a heat-resistant microcapsule of blueberry fruit pomace extract, a preparation method, an application and a biscuit. Background Art

[0002] The industrial production of blueberries mainly focuses on fruit juice. After the blueberry berries are juiced, about 30% of the fruit pomace by weight of the fresh fruit is produced. The blueberry fruit pomace contains bioactive components such as polyphenols, polysaccharides, anthocyanins, and flavonoids, and has various effects. If not effectively utilized, it will cause waste of biological resources. Studying the active components and processing applications of blueberry fruit pomace by-products and finding their potential application values are of great significance for the development of the blueberry industry and the comprehensive utilization of resources, improving the added value of agricultural and forestry products, and increasing the economic income of forestry resources. However, the texture of blueberry fruit pomace is rough and the aftertaste is bitter. Direct consumption has poor sensory quality and is not popular among consumers. Extracting bioactive components is one of the methods for the utilization of fruit pomace by-products.

[0003] Due to consumers' increasing preference for "healthy" foods, in the food industry, the development of functional and nutritious products has received more and more attention. Adding bioactive compounds as ingredients to functional foods has become a new trend in the food industry. However, the stability of the active components of blueberry fruit pomace extract is relatively low. During food processing and storage, adverse factors such as temperature, pH value, light, and oxygen will cause its degradation, which limits the application range of blueberry fruit pomace extract. Moreover, the high water content of blueberry fruit pomace extract also increases the transportation and storage costs. At the same time, due to the presence of low-molecular sugars in blueberry fruit pomace extract, direct spray drying will cause the problem of the feed liquid adhering to the drying chamber, resulting in difficult operation and reduced yield.

[0004] Therefore, how to improve the stability of blueberry fruit pomace extract, especially the thermal stability, and reduce the storage and transportation costs is of great significance for the comprehensive utilization of blueberry fruit pomace and its application in high-temperature foods. Summary of the Invention

[0005] In view of problems such as the instability of blueberry fruit pomace extract, the present application provides a heat-resistant microcapsule of blueberry fruit pomace extract, a preparation method, an application and a biscuit.

[0006] In the first aspect, the present application provides a heat-resistant microcapsule of blueberry fruit pomace extract, and the following technical solution is adopted.

[0007] A heat-resistant microcapsule of blueberry fruit pomace extract, between 120 - 270 °C, the mass loss of the microcapsule does not exceed 20%.

[0008] Preferably, the core material of the microcapsule is obtained by extracting blueberry fruit pomace with a citric acid solution.

[0009] Preferably, the extraction method of the microcapsule core material is as follows: using a citric acid solution with a pH of 2 as the extractant, with a solid-liquid ratio of 1:34 - 38, extracting for 3 - 5 h at 60 - 65 °C; rotating and evaporating the obtained blueberry fruit residue extract to 1 / 5 - 1 / 3 of the original volume to obtain the core material.

[0010] Preferably, the microcapsule wall material is one or more of maltodextrin, whey protein isolate, and soy protein isolate.

[0011] Preferably, the microcapsule wall material is a mixture of maltodextrin and soy protein isolate, and the mass ratio of the two is 1:2.

[0012] In a second aspect, the present application also proposes a method for preparing a heat-resistant microcapsule of blueberry fruit residue extract, and the following technical solution is adopted.

[0013] A method for preparing a heat-resistant microcapsule of blueberry fruit residue extract includes the following steps:

[0014] S1: Add 18 - 22 wt% of the wall material to water, stir evenly to obtain a microcapsule wall material solution;

[0015] S2: Slowly add the core material to the wall material solution, with a mass ratio of the wall material solution to the core material of 4 - 6:1, stir and mix evenly, and spray-dry at an injection rate of 140 - 160 mL / h and an inlet temperature of 150 ± 5 °C to obtain the microcapsule of blueberry fruit residue extract.

[0016] In a third aspect, the present application also proposes an application of the heat-resistant microcapsule of blueberry fruit residue extract in baked products.

[0017] Preferably, the baked products are bread, biscuits, cakes, mooncakes, or pastries.

[0018] In a fourth aspect, the present application also proposes a kind of biscuit, and the following technical solution is adopted.

[0019] A kind of biscuit, based on the mass of low-gluten flour, contains 45 - 55% of butter, 25 - 35% of powdered sugar, 30 - 40% of egg liquid, 10 - 12% of the above-mentioned microcapsule, and 1 - 2% of salt.

[0020] In summary, the present application has the following beneficial effects:

[0021] 1. The wall material adopted in the present application can achieve an encapsulation rate of more than 94% for both polyphenols and anthocyanins in the blueberry fruit residue extract, and the encapsulation effect is better.

[0022] 2. The microcapsules of blueberry fruit pomace extract prepared in this application have good color stability, and have a small mass loss during heating between 120 - 270 °C, not exceeding 20%, showing excellent thermal stability.

[0023] 3. The microcapsules of blueberry fruit pomace extract prepared in this application have a moisture content of less than 6% and a water activity of 0.25 - 0.30, and also have high stability during storage at 25 °C, enabling the microcapsules to have a long shelf life and reducing storage and transportation costs.

[0024] 4. After the microcapsules of blueberry fruit pomace extract prepared in this application are applied to baked foods, the retention rate of polyphenols reaches over 85%, and there are no obvious changes in color and taste, providing a specific direction for the application of blueberry fruit pomace. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Powder photos of microcapsules of blueberry fruit pomace extract prepared with different wall materials; among them, (A) the wall material is maltodextrin; (B) the wall material is soy protein isolate; (C) the wall material is a mixture of maltodextrin - soy protein isolate;

[0026] Figure 2 Particle size distribution diagrams of microcapsules of blueberry fruit pomace extract prepared with different wall materials; among them, (A) the wall material is maltodextrin; (B) the wall material is soy protein isolate; (C) the wall material is a mixture of maltodextrin - soy protein isolate;

[0027] Figure 3 Retention rates of polyphenols, anthocyanins, flavonoids, and antioxidant activity of the core material stored at 4 °C and 25 °C for 90 days;

[0028] Figure 4 Retention rates of polyphenols, anthocyanins, flavonoids, and antioxidant activity of microcapsules of blueberry fruit pomace extract prepared with different wall materials stored at 4 °C and 25 °C for 90 days;

[0029] Figure 5 Thermogravimetric analysis diagrams; among them, (A) the core material; (B) the wall material is maltodextrin; (C) the wall material is soy protein isolate; (D) the wall material is a mixture of maltodextrin - soy protein isolate;

[0030] Figure 6 Comparison photos of cookies before and after baking;

[0031] Figure 7 Electronic tongue radar diagrams of cookies. DETAILED DESCRIPTION OF THE INVENTION

[0032] The present application will be further described in detail below in conjunction with embodiments. It should be specifically noted that: for those conditions not specified in the following embodiments, they are carried out according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, the raw materials used in the following embodiments can all be obtained from ordinary commercial sources.

[0033] In the following content, MD refers to maltodextrin, SPI refers to soy protein isolate, and WPI refers to whey protein isolate.

[0034] Preparation Example 1 - Preparation of Extract from Blueberry Fruit Residue

[0035] Take 200 g of blueberry fruit residue, use a citric acid solution with pH = 2 as the extraction solution, set the solid-liquid ratio to 1:36, and extract at 63 °C for 4 h to obtain an extraction solution. Rotate and evaporate the obtained blueberry fruit residue extraction solution to 1 / 4 of the original extraction solution volume to obtain a concentrated blueberry fruit residue extraction solution, and use the concentrated solution as the microcapsule core material.

[0036] Example 1

[0037] Add 20% (w / w) of maltodextrin (MD) to pure water, and stir with a magnetic stirrer until homogeneous to obtain a microcapsule wall material solution.

[0038] Slowly add the concentrated blueberry fruit residue extraction solution to the wall material solution. The ratio of the wall material solution to the concentrated blueberry fruit residue extraction solution is 5:1 (w / w). Stir and mix evenly with a magnetic stirrer, and spray-dry at an injection rate of 150 mL / h and an inlet temperature of 150 °C to obtain microcapsules of blueberry fruit residue extract.

[0039] Examples 2 - 9

[0040] The difference from Example 1 lies in that the microcapsule wall material solution is different. For details, see Table 1.

[0041] Application Example 1

[0042] Based on the mass of low-gluten flour as 100%, the ratios of the remaining ingredients are 50% butter, 30% powdered sugar, 35% egg liquid, 11% microcapsules, and 1.5% salt.

[0043] The specific operation process is as follows: Weigh 100 g of low-gluten flour, 50 g of butter, 30 g of powdered sugar, 35 g of egg liquid, 11 g of microcapsules, and 1.5 g of salt. After softening the butter, beat it until it turns white, add the microcapsules, powdered sugar, and salt and continue to beat, then add the egg liquid, and finally add the low-gluten flour and mix evenly. After preheating the oven, bake at 170 °C for 15 min and cool to obtain microcapsule cookies.

[0044] The microcapsules are the microcapsules of blueberry fruit residue extract prepared in Example 1.

[0045] Application Example 2

[0046] The difference from Application Example 1 is only that the microcapsules are the blueberry fruit pomace extract microcapsules prepared in Example 3.

[0047] Application Example 3

[0048] The difference from Application Example 1 is only that the microcapsules are the blueberry fruit pomace extract microcapsules prepared in Example 7.

[0049] Comparative Application Example 1

[0050] Based on 100% of the mass of the cake flour, the ratios of the remaining ingredients are 50% butter, 30% powdered sugar, 35% egg liquid, and 1.5% salt.

[0051] The specific operation process is as follows: Weigh 100 g of cake flour, 50 g of butter, 30 g of powdered sugar, 35 g of egg liquid, and 1.5 g of salt. After softening the butter, whip it until it turns white, add the powdered sugar and salt and continue to whip, then add the egg liquid, and finally add the cake flour and mix evenly. After preheating the oven, bake at 170 °C for 15 min, and cool to obtain microcapsule cookies.

[0052] Comparative Application Example 2

[0053] Based on 100% of the mass of the cake flour, the ratios of the remaining ingredients are 50% butter, 30% powdered sugar, 35% egg liquid, 11% concentrated blueberry fruit pomace extract, and 1.5% salt.

[0054] The specific operation process is as follows: Weigh 100 g of cake flour, 50 g of butter, 30 g of powdered sugar, 35 g of egg liquid, 11 g of concentrated blueberry fruit pomace extract, and 1.5 g of salt. After softening the butter, whip it until it turns white, add the powdered sugar and salt and continue to whip, then add the egg liquid, and finally add the cake flour and mix evenly. After preheating the oven, bake at 170 °C for 15 min, and cool to obtain microcapsule cookies.

[0055] Performance Detection Test

[0056] Detection Method / Test Method

[0057] 1. Determination of Encapsulation Efficiency

[0058] Since part of the microcapsule wall material contains maltodextrin (MD), which will interfere with the determination of crude polysaccharides, the encapsulation efficiency of the active ingredients in the microcapsules in this application is measured by polyphenols and anthocyanins.

[0059] Determination of the content of surface-active components in microcapsules: Weigh 200 mg of microcapsules, add 2 mL of a mixture of ethanol:methanol (1:1, v / v), and vortex for 1 min. Determination of the total content of active components: Weigh 200 mg of microcapsules, add 2 mL of a mixture of methanol:acetic acid:water (50:8:42, v / v / v), vortex for 1 min, and sonicate for 20 min. The above samples were centrifuged at 7700×g for 5 min at 4 °C, and the supernatant was taken to measure the relevant content. The encapsulation efficiency of the microcapsules was calculated according to Equation (1).

[0060]

[0061] 2. Determination of polyphenol content

[0062] The determination of polyphenol content was carried out by the Folin-Ciocalteu method, and gallic acid was used as the standard to draw a standard curve. Use a pipette to transfer 1 mL from standard solutions or blueberry fruit pomace extracts of different concentrations, and add 5.0 mL of distilled water, 1 mL of Folin-Ciocalteu reagent, and 3 mL of 7.5% sodium carbonate solution respectively. After mixing, develop color in the dark for 2 h, and measure the absorbance at a wavelength of 765 nm. The polyphenol content was calculated according to the standard curve and formula, and the results were expressed as milligrams of gallic acid equivalents per gram of blueberry fruit pomace powder (mg GAE / g).

[0063]

[0064] In the formula, c is the mass concentration of the sample solution calculated from the standard curve, mg / mL; V is the volume of the blueberry polyphenol extract, mL; N is the dilution factor; m is the mass of the blueberry fruit pomace powder, g.

[0065] 3. Determination of anthocyanin content

[0066] The determination of anthocyanin content was carried out by the pH differential method. Prepare buffer solutions with pH 1.0 (potassium chloride, 0.025 M) and pH 4.5 (sodium acetate, 0.4 M). Dilute the part to be measured with the buffer solution of pH 1.0 to determine an appropriate dilution factor until the absorbance at 520 nm is within the linear range of the spectrophotometer. Using this dilution factor, prepare 2 diluted samples, one diluted with the buffer solution of pH 1.0 and the other diluted with the buffer solution of pH 4.5, and measure the absorbance at 520 nm and 700 nm respectively. The total anthocyanin content was expressed as milligrams of cyanidin-3-glucoside (C3G) equivalents per liter of extract, and the calculation formula was as follows:

[0067]

[0068] Where: A = (A520nm - A700nm) at pH 1.0 - (A520nm - A700nm) at pH 4.5; MW is the relative molecular mass of cyanidin-3-glucoside, 449.2 g / mL; DF is the dilution factor; ε is the extinction coefficient of cyanidin-3-glucoside, 29600; L is the cell path length (usually 1). The anthocyanin retention rate is calculated as the percentage of the existing anthocyanin content in the microcapsules to the initial content.

[0069] 4. Color difference analysis

[0070] The color of the microcapsules was measured using a color difference meter based on the CIELAB system. The total color difference (ΔE) was calculated according to the following formula:

[0071] ΔE = [(L sample * - L standard *) 2 + (a sample * - a standard *) 2 + (b sample * - b standard *) 2 0.5 (4)

[0072] Where, L* represents lightness, the larger L* is, the lighter the color; a* represents red-green degree, the larger a* is, the redder the color; b* represents yellow-blue degree, the larger b* is, the yellower the color; ΔE represents the total color difference. The white plate of the color difference meter was used as the standard.

[0073] 5. Determination of moisture content and water activity

[0074] The microcapsules were placed in an oven at 105 °C and dried to a constant weight. The moisture content of the microcapsule powder (1 g) was the percentage of its weight loss (%).

[0075]

[0076] The water activity was measured by a water activity meter.

[0077] 6. Hygroscopicity determination

[0078] A sample of the microcapsule powder (1 g) was placed in a desiccator containing saturated NaCl solution (75.29% RH) and weighed at intervals until equilibrium was reached. The hygroscopicity was expressed as the number of grams of water adsorbed per 100 g of microcapsules (g / 100 g).

[0079] 7. Particle size determination

[0080] The particle size and distribution of the microcapsules were measured using a laser particle size analyzer.

[0081] 8. Thermogravimetric analyzer determination ​

[0082] The core material (the concentrated extract of blueberry fruit pomace in Preparation Example 1) was dried in an oven for later use. A thermogravimetric analyzer was used to evaluate the thermal stability of each microcapsule sample and the core material. The specific operation was as follows: Weigh 3 - 5 mg of the sample to be measured. In a nitrogen atmosphere, the temperature was raised from 30 °C to 800 °C at a heating rate of 10 °C / min, and the change in the mass of the sample with temperature or time was measured.

[0083] 9. Storage stability of microcapsules

[0084] The core material (the concentrated extract of blueberry fruit pomace in Preparation Example 1) and the microcapsules of blueberry fruit pomace extract were filled into 50 mL amber glass bottles and sealed, and stored in the dark at 4 °C and 25 °C for 3 months. During this period, the retention rates of polyphenols, anthocyanins, flavonoids, and antioxidant activity were measured every 15 days to monitor the storage stability of the core material and the microcapsules.

[0085] 10. Determination of polyphenols in cookies

[0086] The cookies were crushed. 1 g of the crushed cookies was added to 10 mL of pure water, shaken at 150 rpm for 10 min, filtered, and the supernatant was taken. The polyphenol content was determined according to the method described in Part 2 of the performance detection method.

[0087] 11. Electronic nose analysis

[0088] Take 5 g of cookie samples in a 50 ml centrifuge tube, seal and let stand for 30 min, and perform headspace injection for detection. Detection conditions: Sampling time is 1 second / group; Sensor self-cleaning time is 60 seconds; Injection time is 5 seconds; Injection flow rate is 400 ml·min-1; Analysis sampling time is 80 seconds. The data from 69 - 71 seconds was taken as the result for summary and analysis.

[0089] 12. Electronic tongue analysis

[0090] Take 15 g of cookies and add 150 ml of water, break and stir evenly, then centrifuge and filter, and take the liquid for machine detection. The specific operation is as follows:

[0091] (1) Equilibration: The sensor was first cleaned in the cleaning solution for 90 s, then in the reference solution for 120 s, and then in another reference solution for 120 s. The sensor was zeroed at the equilibrium position for 30 s;

[0092] (2) Testing: The testing time was 30 s, and the first taste value was output;

[0093] (3) After that, clean with the reference solution for 3 s, insert the sensor into the new reference solution to test the aftertaste for 30 s. The food five-taste sensors C00 (corresponding to acidic bitterness), AE1 (corresponding to astringency), CA0 (corresponding to sourness), CT0 (corresponding to saltiness), and AAE (corresponding to umami) were tested 4 times. The first cycle was removed, and the average value of the remaining 3 times was taken as the test result.

[0094] Data analysis

[0095] 1. Encapsulation efficiency of microcapsules

[0096] Table 1 Influence of different wall materials on the encapsulation efficiency of microcapsules

[0097]

[0098] The main active components in blueberry fruit pomace are polyphenols and anthocyanins. Therefore, wall materials with good encapsulation effects on both of them need to be found. It can be seen from Table 1 that wall materials such as maltodextrin MD, whey protein isolate WPI, and soy protein isolate SPI have a certain degree of encapsulation effect on polyphenols and anthocyanins, but the best encapsulation effects are achieved with maltodextrin, soy protein isolate, and their mixtures as wall materials.

[0099] Therefore, all subsequent experiments were carried out with the blueberry fruit pomace microcapsules prepared in Example 1, Example 3, and Example 7.

[0100] 2. Color, particle size, and storage stability of microcapsules

[0101] Table 2 Various indexes of blueberry fruit pomace extract microcapsules

[0102]

[0103]

[0104] Table 3 Retention rates of polyphenols, anthocyanins, flavonoids, and antioxidant activity in microcapsules after storage for 90 days

[0105]

[0106] 2.1 Color of microcapsules

[0107] It can be seen from Table 2 that there are significant differences in a* and b* of the three kinds of microcapsules. The red and yellow tones of MD microcapsules are the most significant, with a* and b* being 37.76±0.41 and 11.34±0.10 respectively. However, in terms of the total color difference, there is no statistically significant difference between MD and SPI microcapsules, and between SPI and MD-SPI microcapsules.

[0108] At the same time, combined with Figure 1 it can be seen that the difference in the color of microcapsule powder mainly depends on the wall materials used. The microcapsules with MD as the wall material are the brightest, showing bright red characteristics; the microcapsules with MD-SPI as the wall material are the second, showing pink-purple characteristics; the microcapsules with SPI as the wall material are the darkest. This difference may be due to the fact that the amino acids contained in SPI are prone to Maillard reaction with the sugars in the blueberry fruit pomace extract, and the spray drying process promotes the Maillard reaction, thus making the powder darker.

[0109] 2.2 Particle size of microcapsules

[0110] The particle size distribution of the microcapsules of blueberry fruit pomace extract is as Figure 2 shown. All the particle size distributions of the microcapsules show an obvious unimodal distribution, indicating that the particle size distribution of the microcapsules is uniform. The type of wall material has a certain influence on the particle size distribution. Among them, the microcapsules with MD-SPI as the wall material have the lowest average particle size, which is 1.5 - 3 times lower than that of other microcapsules. At the same time, the particle size range of the microcapsules with this wall material is the widest (D10 = 3.16 μm, D90 = 24.50 μm). In theory, smaller particles can exist between larger particles, thus occupying less space and generating a higher packing density. However, in this study, the microcapsules with MD-SPI as the wall material have a larger particle size range but a smaller packing density. The smaller particles are not between the larger particles, and the space between them is empty, which means that the microcapsules with MD-SPI as the wall material have the characteristic of not easily forming aggregates, thus making them easier to mix evenly with other raw materials.

[0111] 2.3 Storage stability of microcapsules

[0112] Generally speaking, products with a lower moisture content and a water activity below 0.6 are considered physically and chemically stable. It can be seen from Table 2 that the moisture content range of the microcapsules prepared with 3 kinds of wall materials is between 5.13% - 5.92%, and there is no significant difference in the moisture content among the microcapsule samples; the water activity range is between 0.25 - 0.30. The lower moisture content and water activity make the blueberry fruit pomace microcapsules have a lower risk of microbial growth and spoilage, and theoretically the shelf life of the product will be longer.

[0113] Hygroscopicity, that is, the ability of the powder to absorb moisture from the surrounding environment, is a key parameter for evaluating the stability of the powder. The sample with MD as the wall material shows the highest hygroscopicity (10.75 g / 100 g), and the samples with SPI and MD-SPI as the wall materials show similar hygroscopicity (9.64 g / 100 g and 9.68 g / 100 g respectively). This difference may be due to the different moisture contents of the microcapsules. Generally speaking, the lower the moisture content, the higher the moisture concentration gradient between the microcapsules and the surrounding air, and the stronger the hygroscopicity. The MD microcapsules have the lowest moisture content, so they have the highest hygroscopicity.

[0114] Flavonoids (especially anthocyanins) are the main polyphenolic compounds in the extract of Lonicera caerulea fruit pomace. Therefore, it is more scientific to evaluate the storage stability using multiple active ingredient indexes such as polyphenol, anthocyanin, and flavonoid contents. Since the extract of Lonicera caerulea fruit pomace contains sugars, spray drying will cause serious wall sticking phenomenon, and it is difficult to directly spray dry to obtain a satisfactory extract powder. Therefore, in this application, the concentrated liquid of Lonicera caerulea fruit pomace (i.e., the core material of the microcapsule) was used as a control to study the effect of microencapsulation on improving the stability of the extract of Lonicera caerulea fruit pomace.

[0115] It can be seen from Figure 3 and Figure 4 that the contents of active ingredients and antioxidant activity of the microencapsulated extract of Lonicera caerulea fruit pomace show a non-linear decreasing trend; while the retention rates of the active ingredients and antioxidant activity of the core material show a linear trend. Temperature is the key factor affecting the stability of the microcapsule. When the core material is stored at 25 °C, the retention rates of polyphenol, anthocyanin, flavonoid, and antioxidant activity are significantly lower than those stored at 4 °C. At 25 °C, the final retention rates of polyphenol, anthocyanin, flavonoid, and antioxidant activity of the core material are 88.1 ± 0.54%, 72.43 ± 0.72%, 87.71 ± 1.01%, and 77.03 ± 0.88% respectively, among which the anthocyanin content and antioxidant activity have the largest losses. At 4 °C, the final retention rates of polyphenol, anthocyanin, flavonoid, and antioxidant activity of the core material are 94.93 ± 0.88%, 90.07 ± 0.36%, 92.82 ± 0.07%, and 86.61 ± 0.43% respectively. For the microcapsule, after 90 days of storage, at the storage temperature of 4 °C, the loss of active ingredients is 1.44% - 5.7%, and the antioxidant activity decreases by 6.7% - 8.7%; at the storage temperature of 25 °C, the losses of active ingredients and antioxidant activity are slightly higher, which are 2.76% - 7.41% and 9.75% - 10.2% respectively.

[0116] As shown in Table 3, until the end of the storage period, that is, the 90th day, at the two storage temperatures, there is no significant difference in the retention rates of polyphenol, anthocyanin, and flavonoid in the microcapsules with MD as the wall material, and there is also no significant difference in the retention rates of flavonoid and antioxidant activity in the microcapsules with SPI as the wall material.

[0117] The above results show that the difference in the preservation rates of the microcapsules of the extract of Lonicera caerulea fruit pomace prepared in this application at different temperatures is very small, or even not significantly different. The microencapsulated extract of Lonicera caerulea fruit pomace shows good storage stability. After storing for 90 days at 4 °C and 25 °C, the microcapsules of MD, SPI, and MD-SPI can all maintain the retention rates of polyphenol, anthocyanin, and flavonoid contents above 92%, and the retention rate of antioxidant activity above 89%. Microencapsulation at 25 °C can basically achieve the effect of low-temperature preservation at 4 °C.

[0118] In summary, although the unembedded concentrated blue honeysuckle fruit pomace liquid can achieve good storage effect at low temperature, the liquid state and refrigerated storage increase the transportation and storage costs. Therefore, the microencapsulated blue honeysuckle fruit pomace extract powder, due to its low moisture content, water activity and good storage stability at 25°C, is more conducive to industrial application.

[0119] 3. Heat resistance of microcapsules

[0120] Thermogravimetric analysis (TGA) is used to evaluate the thermal degradation of a sample due to mass loss within a certain temperature range, and can directly understand the influence of heating on the components of microcapsules.

[0121] From Figure 5 it can be seen that the thermogravimetric curves of all samples show three different stages. The thermogravimetric diagram of the core material shows 3 heat loss events: at 30 - 145°C, the mass loss is 4.3%; at 275 - 311°C, the mass loss is 61.38%; above 270°C, the mass loss is 17.05%. The increase in temperature will cause the active ingredients in the microcapsules to be released from the wall material matrix and lead to further degradation. The initial weight loss rate of the microcapsules with MD as the wall material at 30 - 130°C is 7.68%, and the initial weight loss rates of the microcapsules with SPI and MD - SPI as the wall materials at 30 - 123°C are 7.67% and 7.18% respectively. This initial loss may be caused by the evaporation of residual moisture after spray drying or moisture absorbed during storage. Between 130 - 272°C, 123 - 242°C and 123 - 252°C, the mass losses of MD, SPI and MD - SPI microcapsules are 17.44%, 9.8% and 14.15% respectively. Above 272°C, 242°C and 252°C, the mass of the microcapsules decreases rapidly, and the loss amounts are 58.88%, 55.23% and 56.16% respectively, which may be due to the decomposition of the wall material and the core material.

[0122] From Figure 5 the DTG curve in it can be seen that the thermal degradation rates of the core material and the microcapsules with MD, SPI and MD - SPI as the wall materials reach the maximum values at 192°C, 313.6°C, 306.6°C and 307.2°C respectively. The temperature corresponding to the maximum thermal degradation rate of the microcapsules is significantly higher than that of the core material. It can be seen that the encapsulated blue honeysuckle fruit pomace extract shows higher thermal stability, and the mass loss migrates to higher temperatures. This enhancement of thermal stability may be due to the thermal resistance of the microcapsule wall material slowing down the heat transfer to the inside and improving the protection of the core material.

[0123] After the blue honeysuckle fruit pomace extract is microencapsulated, its thermal stability increases, expanding the temperature range for the processing and application of the polyphenol - rich blue honeysuckle fruit pomace extract, enabling it to retain more active ingredients such as polyphenols and anthocyanins and antioxidant activity during high - temperature processing.

[0124] 4. Characteristics of Cookies

[0125] 4.1 Polyphenol Content of Cookies

[0126] Table 4 Polyphenol Content and Retention Rate of Cookies before and after Baking

[0127]

[0128] It can be seen from Table 4 that compared with Example 2 where the blueberry fruit pomace extract was added without microencapsulation, the polyphenol loss was significant after baking, and the polyphenol retention rate was only 30.39%. However, the blueberry fruit pomace extracts in Examples 1-3 were all microencapsulated, so the polyphenol retention rate could reach over 85%.

[0129] From Figure 6 it can be seen that before baking, the cookies in Comparative Example 1 showed a soft yellow hue, and the cookies in Comparative Example 2 showed a pink color. After baking, the color of the cookies in Example 2 changed significantly and basically showed a light brown color; while the cookies in Examples 1-3 still showed a relatively obvious purple or pink-purple color. This indicates that the microencapsulation maintains the color of the cookies well before and after baking.

[0130] 4.2 Taste Analysis of Cookies

[0131] The electronic tongue can simulate the taste perception mechanism of living organisms. By detecting the changes in membrane potential generated by the electrostatic or hydrophobic interactions between various taste substances and artificial lipid membranes, and detecting the taste characteristics through electronic sensors, it can evaluate the sourness, bitterness, astringency, aftertaste of bitterness, aftertaste of astringency, umami, richness, and saltiness, so as to evaluate the taste of food. The richness among them is the aftertaste of umami, reflecting the persistence of umami in the sample, also known as the umami persistence. The aftertaste of bitterness reflects the residual degree of bitterness, and the aftertaste of astringency reflects the residual degree of astringency.

[0132] The reference solution for this test consists of KCL and tartaric acid to form a taste value. The tasteless point of sourness is -13, and the tasteless point of saltiness is -6. The electronic tongue test results of cookies without and with SPI microcapsules are as Figure 7 shown. The sourness of both types of cookies is below the tasteless point, indicating that neither of the two types of cookies has a sour taste characteristic. Although the blueberry fruit pomace has a sour taste and a slightly bitter taste, it does not affect the normal taste of the cookies. There is no significant difference in the response values of other taste sensors for the two types of cookies, indicating that the addition of the blueberry fruit pomace extract microcapsule does not cause a significant change in the taste of the cookies and can be applied to the development of functional cookies.

[0133] The fruits of Lonicera caerulea contain rich natural purplish-red pigments and are good resources for extracting natural food pigments. However, the anthocyanins in Lonicera caerulea have unstable chemical properties and are easily affected by other chemical components in food. The microencapsulated extract of Lonicera caerulea pomace prepared in this application not only presents attractive colors such as red or purple, but also has low moisture content, water activity and hygroscopicity, and can be stored for a long time at 25°C. Therefore, it can be added to food as a natural pigment. More importantly, the thermal stability of the microencapsulated extract of Lonicera caerulea pomace prepared in this application has been greatly improved, and it can be applied to foods that require high temperature resistance such as baked products, further broadening the application scope of the extract of Lonicera caerulea pomace.

[0134] The above are only some embodiments of this application. The protection scope of this application is not limited to the above embodiments. For those of ordinary skill in the art, several improvements and refinements made without departing from the creative design of this application should also fall within the protection scope of this application.

Claims

1. A heat-resistant Lonicera caerulea fruit pomace extract microcapsule, characterized in that: At 120-270° C., the mass loss of the microcapsules does not exceed 20%.

2. The heat-resistant Lonicera caerulea fruit pomace extract microcapsules according to claim 1, characterized in that: The microcapsule core material is obtained by extracting blue lonicera edulis fruit pomace with citric acid solution.

3. The heat-resistant Lonicera caerulea fruit pomace extract microcapsules according to claim 2, characterized in that: The extraction method of the microcapsule core material is as follows: using a citric acid solution with a pH of 2 as an extractant, with a solid-liquid ratio of 1:34-38, and extracting at 60-65° C. for 3-5 hours; rotary evaporating the obtained blue indigo fruit pomace extract to 1 / 5-1 / 3 of the original volume to obtain a blue indigo fruit pomace extract concentrate as the microcapsule core material.

4. The heat-resistant Lonicera edulis pomace extract microcapsules according to any one of claims 1 to 3, characterized in that: The microcapsule wall material is one or more of maltodextrin, whey protein isolate and soy protein isolate.

5. The heat-resistant Lonicera caerulea fruit pomace extract microcapsules according to claim 5, characterized in that: The microcapsule wall material is a mixture of maltodextrin and soy protein isolate, and the mass ratio of the two is 1:

2.

6. The method for preparing the heat-resistant Lonicera caerulea fruit pomace extract microcapsules according to any one of claims 1 to 5, characterized in that: The preparation method comprises the following steps: S1: Add 18-22wt% of wall material into water and stir evenly to obtain microcapsule wall material solution; S2: slowly add the core material into the wall material solution, the mass ratio of the wall material solution to the core material is 4-6:1, stir and mix evenly, spray dry at an injection rate of 140-160 mL / h and an inlet temperature of 150±5° C. to obtain blue loquat fruit pomace extract microcapsules.

7. Use of the heat-resistant Lonicera caerulea pomace extract microcapsules according to any one of claims 1 to 5 in baked products.

8. The use of the heat-resistant blue lonicera edulis pomace extract microcapsules in baked products according to claim 7, characterized in that: The baked product is bread, biscuits, cakes, moon cakes or desserts.

9. A biscuit, characterized in that: The biscuits are based on the mass of low-gluten flour, and contain 45-55% butter, 25-35% powdered sugar, 30-40% egg liquid, 10-12% of the microcapsule described in any one of claims 1-5, and 1-2% salt.

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