Double-gel, preparation method and application thereof and crisp biscuit thereof

Abstract

The invention relates to the field of food processing, and discloses double gel, a preparation method and application thereof and crisp biscuits thereof. The double-gel component provided by the invention comprises a solution-state oil gel and a hydrogel, the solution-state oleogel component comprises soybean oil, beef tallow, ethyl cellulose and an emulsifier; the hydrogel component is prepared from konjac glucomannan. The preparation method comprises the following steps: adding ethyl cellulose and an emulsifier into soybean oil and beef tallow, heating and dissolving to obtain solution-state oleogel; after the konjac glucomannan is swelled in water, heating is carried out, and hydrogel is formed; and mixing the hydrogel with the solution-state oil gel, stirring, homogenizing, cooling and standing to obtain the double gel. Crisp biscuits prepared from the double-gel are closer to crisp biscuits prepared from margarine butter, the hardness, the brittleness and the fatty acid content are remarkably reduced, and the crisp biscuits have the advantages of being uniform in color and luster, regular in shape and layered in section.

Description

Technical Field

[0001] The present invention relates to the field of food processing, and more specifically, to a double gel and a method for preparing the same, and its application to shortcrust biscuits. Background Art

[0002] With the improvement of people's living standards and the acceleration of the pace of life, biscuits have become part of the staple food for most people during snacks or meals. Shortcrust biscuits are a type of biscuit with a crispy texture and are deeply loved by consumers for their unique taste. Solid fat is a key component that imparts functionality to fat-rich baked foods (including shortcrust dough products and puff pastries). In shortcrust biscuits, fat accounts for 35% (w / w) of the product and provides the product with palatability, porosity, and a brittle texture. These properties are determined by the solid fat content, melting behavior, and crystal structure of the fat used, which largely depend on their fatty acid and triglyceride (TAG) composition as well as processing conditions. However, conventional plastic fats have a relatively high content of saturated fatty acids and may contain a certain amount of trans fatty acids. Excessive intake of saturated fatty acids and trans fatty acids increases the risk of chronic diseases such as coronary heart disease, cardiovascular diseases, and obesity. Therefore, it is particularly important to construct healthy plastic fats with low saturated fatty acid content for application in shortcrust biscuits.

[0003] Double gels exhibit solid-like characteristics comparable to commercial solid fats. In a recent study, rice bran wax (RBW) / soybean oil OG with different concentrations of monoglyceride (MG) (0 - 2 wt%) and double gels prepared based on alginate / κ-carrageenan showed rheological properties comparable to baking fats, indicating their potential to be viable alternatives in fat-rich food applications. In the food industry, monoglycerides and their derivatives are some of the most important food emulsifiers because they account for the majority of emulsifier production. They are widely used in foods such as bread, cakes, spreads, ice cream, etc. The HLB value usually exhibits more lipophilic behavior between 3 and 6 and is thus more effective in stabilizing water-in-oil (W / O) double gels. Lecithin is an amphiphilic substance with good emulsifying properties and is commonly used as an emulsifier. Based on the affinity of phospholipids for oil, it can form a protective layer on the surface of the oleogel. However, the effect of double gels with added emulsifiers on the physical properties of shortcrust biscuits is not yet clear.

[0004] The prior art CN117322476A adds a crystalline emulsifier and natural wax to vegetable oil to form an oleogel, mixes it with a polysaccharide-based hydrogel, and forms an emulsion gel through high-speed shear emulsification, and then whips and aerates it to obtain a double gel foam with foaming properties. This method prepares different types of emulsion foams by adjusting the oil-water ratio and is applied to food 3D printing and low-fat non-dairy cream products. However, this solution uses a crystalline emulsifier or natural wax to stabilize the oleogel, but it is prone to losing plasticity during the baking process, affecting the taste of the food. This technology does not cover aspects such as the application of baked foods, the selection of formula ingredients, and the fat substitution method. Summary of the Invention

[0005] The present invention aims to overcome the defects of the above-mentioned prior art, such as not covering the application of baked foods, the selection of formula ingredients, and fat substitution, and provides a double gel;

[0006] Another object of the present invention is to provide a preparation method of the double gel;

[0007] Another object of the present invention is to provide an application of the double gel;

[0008] Another object of the present invention is to provide a shortcrust biscuit.

[0009] To solve the above technical problems, the technical solution of the present invention is as follows:

[0010] A double gel, the components of which include a solution-state oleogel and a hydrogel; the components of the solution-state oleogel include soybean oil, beef tallow, ethyl cellulose, and an emulsifier; the components of the hydrogel include konjac glucomannan.

[0011] Further, the purity of the konjac glucomannan is not less than 86%, and the degree of deacetylation is 40% - 60%. After partial removal of the acetyl groups of konjac glucomannan, its hydrophilicity is improved, water solubility is enhanced, dispersibility is better, and it is easier to form a uniform sol. The intermolecular hydrogen bond interaction is also enhanced, and the formed hydrogel is stronger and has stronger thermal irreversibility, and can still maintain a stable gel state after heating. The moderate degree of deacetylation reduces the viscosity of the system, making it easier to control the rheological properties in the food system, while still maintaining good thickening and stabilizing effects.

[0012] Preferably, the intrinsic viscosity value of the ethyl cellulose is 18 - 22 mPa·s.

[0013] Preferably, the mass fraction of ethyl cellulose in the solution-state oleogel is 10%.

[0014] Further, the emulsifier is a surface-active emulsifier.

[0015] Preferably, the surface-active emulsifier includes glycerol monooleate and lecithin.

[0016] Preferably, the purity of the monoolein is not less than 50%, and the purity of the lecithin is greater than 70%.

[0017] Furthermore, the mass ratio of the soybean oil to the beef tallow is 6 - 9:3.

[0018] Preferably, the mass ratio of the soybean oil to the beef tallow is 7:3. Changing the mass ratio of the soybean oil and the beef tallow will cause an increase in the solid fat content and cannot reflect the advantages of the double gel replacing margarine. An appropriate ratio can maintain good physical and chemical properties.

[0019] Furthermore, the mass ratio of the solution - state oleogel to the hydrogel is greater than 1.5.

[0020] Preferably, the mass ratio of the solution - state oleogel to the hydrogel is 7:3. Changing the ratio of the hydrogel and the solution - state oleogel will cause changes in the hardness and visco - elasticity of the gel, affecting the hardness, moisture content, and taste of the biscuits.

[0021] Furthermore, the mass fraction of the emulsifier in the oleogel is 0.5% - 1.5%.

[0022] Preferably, the mass fraction of the emulsifier in the oleogel is 1%. Changing the ratio of the emulsifier will affect the hardness and rheological properties of the gel, ultimately resulting in changes in the hardness and taste of the biscuits.

[0023] A preparation method of the double gel includes the following steps:

[0024] S1. Add ethyl cellulose and an emulsifier to the soybean oil and the beef tallow, heat and dissolve to obtain a solution - state oleogel;

[0025] S2. After konjac glucomannan swells in water, heat it to form a hydrogel;

[0026] S3. Mix the hydrogel and the solution - state oleogel, stir and homogenize, and after cooling and standing, obtain the double gel.

[0027] Furthermore, the heating temperature in S1 is 120 - 140 °C, and stir and dissolve at 100 - 300 r / min.

[0028] Preferably, the heating process is always carried out in a nitrogen environment to prevent the oxidation of the oil or the degradation of the components.

[0029] An application of the double gel is used for preparing shortbread biscuits.

[0030] Preferably, it is used to replace margarine.

[0031] A shortbread biscuit is prepared by using the double gel.

[0032] The present invention innovatively adopts glyceryl monooleate (GM) or lecithin (PC) to emulsify the double-gel structure and applies it to shortbread cookies, successfully replacing margarine, reducing the content of saturated fatty acids, and maintaining good baking performance at the same time. Compared with the crystalline emulsifiers in the prior art, the present invention provides better surface activity, effectively stabilizes the oil gel-hydrogel interface, and improves the uniformity and processability of the double-gel system. The interfacial activity of GM and PC reduces the oil-water interfacial tension, enabling the oil gel and water gel to form a stable bicontinuous phase structure, enhancing the emulsion stability, and enabling the double-gel to maintain good plasticity during baking. The double-gel system of the present invention breaks through the fat crystallization-dependent plasticity system and provides physical properties similar to those of margarine without relying on high saturated fatty acids, significantly improving the health value of food, and providing a feasible low-saturated-fatty-acid alternative for the baking food industry.

[0033] Compared with the prior art, the beneficial effects of the technical solution of the present invention are as follows:

[0034] The saturated fatty acid content (28.02%) of the double-gel of the present invention is significantly lower than that of commercially available margarine (51.58%). Compared with the double-gel without adding emulsifier, the number of air bubbles in the shortbread cookie dough made with the double-gel of the present invention is more, the air bubbles are more evenly dispersed, the shortbread cookies made have lower hardness and crispness, are closer to the shortbread cookies made with margarine, and have the advantages of uniform color, regular shape, and layered cross-section. The shortbread cookies made with the double-gel of the present invention have a moisture content of less than 4% during storage and can still maintain appropriate hardness and crispness after 14 days of storage, proving its good shelf stability. Therefore, the double-gel of the present invention has the potential to replace commercially available margarine in shortbread cookies. Description of the Drawings

[0035] Figure 1 is the determination result of the saturated fatty acid content;

[0036] Figure 2 are the appearance and color difference of different shortbread cookie doughs. A is the actual photo of the shortbread cookie, and B is the color parameter;

[0037] Figure 3 are the shortbread cookie doughs made with different oils under bright field and polarized light;

[0038] Figure 4 is the viscosity of the shortbread cookie doughs made with different oils;

[0039] Figure 5 are the appearance and color difference of the shortbread cookies made with different oils. A is the actual photo of the shortbread cookie, and B is the color parameter;

[0040] Figure 6The moisture content of shortbread cookies made with different oils during storage;

[0041] Figure 7 The sensory evaluation chart of shortbread cookies made with different oils. Detailed implementation method

[0042] The present invention will be further described below in conjunction with the accompanying drawings of the specification and specific embodiments. However, the embodiments do not limit the present invention in any form. Unless otherwise specified, the reagents, methods, and equipment used in the present invention are conventional reagents, methods, and equipment in the technical field.

[0043] Unless otherwise specified, the reagents and materials used in the following examples are all commercially available.

[0044] Soybean oil (SO) was purchased from Yihai Kerry Arawana Grain and Oil Food Co., Ltd. (Shanghai, China); ethyl cellulose (EC, food grade, intrinsic viscosity value 18 - 22 mPa·s) from Shanghai Aladdin Biochemical Technology Co., Ltd.; konjac glucomannan (KGM, purity ≥ 86%) from Huaxia Flower Fairy Co., Ltd. in Shiyan, Hubei; beef tallow was provided by Chongqing Muge Food Co., Ltd.; glyceryl monooleate (GM, ≥ 50%, chromatographically pure) and lecithin (PC, from soybean, > 70%) were purchased from Shanghai Merck Chemical Technology Co., Ltd.; Zhanyi salt-free vegetable butter, cake flour, baking soda, table salt, and icing sugar are all commercially available food grades.

[0045] Example 1 (1GM)

[0046] 1. Preparation of solution-state oleogel

[0047] Put soybean oil and beef tallow in a 250 mL three-necked flask according to a mass ratio of 7:3, and add 10% (by mass) of EC and 1% (by mass) of GM. Place the flask in an oil bath, stir at 300 r / min for 20 min, and continuously heat to 140 °C to make the system temperature higher than the glass transition temperature of EC, so as to ensure that EC is completely dissolved and forms a homogeneous solution. The whole heating process is carried out under a nitrogen atmosphere to prevent oil oxidation or component degradation. After stirring, the obtained system is the solution-state GM oleogel.

[0048] 2. Preparation of hydrogel

[0049] Add medium-degree deacetylated konjac glucomannan with a mass concentration of 1% (w / w) to pure water, stir at 200 r / min for 30 min at 45 °C to make it fully swell and form a homogeneous sol. Then place the obtained sol in a 90 °C water bath and heat for 1 h, and cool it at room temperature to form a thermally irreversible hydrogel.

[0050] 3. Preparation of Double Gel

[0051] Mix the prepared solution-state oleogel and hydrogel in a mass ratio of 7:3, place it at 50 °C and stir at 500 r / min for 5 min, then use a homogenizer to homogenize at 10000 rpm for 3 min. Immediately after homogenization, cool the sample in an ice-water bath for 10 min to promote gelation, then transfer it to a 4 °C refrigerator and let it stand for 12 h, and finally store it in a 25 °C incubator for 24 h to form a double gel.

[0052] 4. Making of Shortbread

[0053] After stirring and mixing 40 g of double gel and 40 g of sugar for 5 min, add 100 g of cake flour, 1 g of salt, and 3 g of baking soda, add 25 g of water, and mix evenly for 5 min. Seal the mixed dough with plastic wrap and refrigerate it at 4 °C in the refrigerator for 1 h. Roll the refrigerated dough with a rolling pin to a thickness of 3 mm, use a round mold with a diameter of 45 mm to cut out round biscuits, and remove the excess dough. Put the shaped biscuit dough into the oven. After preheating the oven at 150 °C for 5 min, bake for 30 min. After the shortbread is baked, let it cool at room temperature and store it in a sealed bag. In addition, replace the double gel with margarine as a control (CM).

[0054] Example 2 (1PC)

[0055] The preparation scheme of Example 2 is similar to that of Example 1, the difference is that the preparation of the solution-state oleogel is as follows: Place soybean oil and beef tallow in a 250 mL three-necked flask in a mass ratio of 7:3, and add EC with a mass fraction of 10%. Place the flask in an oil bath and continuously heat it to 140 °C under stirring at 300 r / min. Lower the system temperature to 120 °C, add PC with a mass fraction of 1% to effectively reduce the discoloration caused by too high heating temperature of lecithin, and continue to stir at a speed of 100 r / min until PC is completely dissolved. The obtained system is a solution-state PC oleogel.

[0056] Comparative Example 1 (7:3)

[0057] The preparation scheme of Comparative Example 1 is similar to that of Example 1, the difference is that the emulsifier GM is not added.

[0058] Comparative Example 2 (6:4)

[0059] The preparation scheme of Comparative Example 2 is similar to that of Comparative Example 1, the difference is that the solution-state oleogel and hydrogel are mixed in a mass ratio of 6:4.

[0060] Detection Method

[0061] 1. Determination of Saturated Fatty Acid Content in Oil

[0062] Take 60 mg of the oil sample and dissolve it in 4 mL of isooctane. Add 200 μL of potassium hydroxide - methanol solution (2 mol / L), vortex - mix for 30 s, and then carry out the methylation reaction for 15 min. After the reaction is completed, add 1 g of sodium bisulfate and shake vigorously to neutralize potassium hydroxide. Let it stand for 40 min, take the supernatant (1 mL) and analyze the composition of fatty acid methyl esters using a gas chromatograph. Inject manually, and the injection volume is 1 μL.

[0063] Chromatographic conditions: HP - 88 capillary column; injection port temperature 240 °C, split ratio 30:1. Initial column temperature 100 °C, hold for 4 min; increase the temperature to 175 °C at a rate of 10 °C / min and hold for 6 min; then increase the temperature to 210 °C at a rate of 4 °C / min and hold for 12 min, and then increase the temperature to 230 °C at a rate of 5 °C / min and hold for 2 min; the detector is a flame ionization detector, hydrogen flow rate 40 mL / min, air flow rate 400 mL / min, tail - blow flow rate 30 mL / min.

[0064] 2. Determination of the viscosity sweep of short - dough

[0065] The viscosity sweep of the dough was measured using a PP25 parallel plate configured with a rotational rheometer (Anton Paar MCR302, Austria). The test temperature was 25 °C, the geometric gap was 500 μm, and the shear rate was 0.1 - 1000 s -1 。

[0066] 3. Observation of the microstructure of short - dough

[0067] Spread the dough evenly on a glass slide after refrigerating for 1 h, cover the glass slide, and place it on the stage. Take pictures of the microstructure of the dough at room temperature with a magnification of 10× in bright - field and polarized - light modes respectively.

[0068] 4. Determination of the baking loss rate and moisture content of short - dough

[0069] Determine the moisture loss of the short - dough before and after baking. The specific method is as follows: Before baking, weigh the weight of the weighing paper, denoted as M 0 , weigh the short - dough on the weighing paper, and record the mass of the short - dough and the weighing paper as M 1 ; after baking, weigh the total mass of the baked short - dough and the weighing paper, denoted as M 2 . The baking loss rate is calculated using equation (1):

[0070] Baking loss rate (%)=(1 - (M 2 - M 0 ) / M 1 - M 0 )×100% (1)

[0071] The moisture content of shortbread cookies during storage was determined by the direct method with reference to GB 5009.4-2016 "National Food Safety Standard - Determination of Moisture in Foods".

[0072] 5. Fluffiness and extensibility of shortbread cookies

[0073] The fluffiness of shortbread cookies was calculated using Equation (2):

[0074] Fluffiness = Thickness (cm) / Mass (g) (2)

[0075] The extensibility of shortbread cookies was calculated using Equation (3):

[0076] Extensibility = Diameter (cm) / Thickness (cm) (3)

[0077] 6. Chromaticity of shortbread cookies

[0078] The color of shortbread cookies and dough was measured using a CM-5 colorimeter (KONICA MINOLTA, Japan). The color parameters were L* (brightness from 0 to 100, representing black to white), a* (+ red, - green), and b* (+ yellow, - blue). The total color difference (ΔE) between shortbread cookie samples made with different oils was calculated according to Equation (4):

[0079]

[0080] 7. Texture determination of shortbread cookies

[0081] The shortbread cookies were placed on the test platform of the texture analyzer to determine their texture properties. The determination conditions were: TPA mode, P / 0.5 cylindrical probe, test speed 1.0 mm / s, compression degree 50%, and trigger point load 10.0 g. All measurements were carried out at 25°C. The values of texture parameters such as hardness, crispness, elasticity, cohesiveness, adhesiveness, chewiness, and resilience of the shortbread cookies were provided by the equipment software

[0082] 8. Sensory evaluation of shortbread cookies

[0083] The sensory evaluation of shortbread cookies was carried out by 10 male and 10 female assessors aged 20 - 30 years old. The specific scoring criteria are shown in Table 1 below. All assessors were given a simple training before the test, and they evaluated the color, shape, taste, texture, and overall acceptance of the shortbread cookies respectively.

[0084] Table 1 Reference table for sensory scoring criteria of shortbread cookies

[0085]

[0086]

[0087] 9. Statistical Analysis

[0088] All detections were determined in parallel three times, and the data were reported as mean ± standard deviation. Statistical analysis of the data was performed using SPSS software (trial version 18.0, SPSS Inc., Chicago, Illinois, USA). One-way analysis of variance was used to evaluate the significance of the differences between the observed means, and then Duncan's test was performed at a significance level of 5%.

[0089] Analysis Instructions

[0090] 1. Analysis of Saturated Fatty Acid Content

[0091] As Figure 1 shown, soybean oil has the lowest saturated fatty acid content (15.40%), and beef tallow has the highest saturated fatty acid content (64.56%). When soybean oil and beef tallow are mixed in a ratio of 7:3, the saturated fatty acid content of the mixed oil (28.02%) is significantly lower than that of margarine (51.58%). In the formula of shortbread cookies, about 19.14 g of oil is added to every 100 g of shortbread cookies made with CM, while about 13.40 g of oil is added to every 100 g of shortbread cookies made with 7:3, 1GM, and 1PC. Therefore, using the double gel prepared with soybean oil mixed with beef tallow as the base oil as a substitute for commercially available margarine can significantly reduce consumers' saturated fatty acid intake.

[0092] 2. Appearance of Different Shortbread Cookie Doughs

[0093] As Figure 2 shown in Figure B, except for the shortbread cookie dough made with CM, the L values of the shortbread cookie doughs of the other oil types are all greater than 50, the a* value is negative, and the b* value is positive, indicating that the shortbread cookie doughs appear bright, slightly green and yellow. Among them, the a* value of CM is positive, indicating that the dough is slightly red because the commercially available margarine ingredients contain β-carotene and the color itself is relatively yellow. The b* value (21.46 - 23.85) of the dough prepared with the double gel as the oil raw material is significantly smaller than the b* value (31.19) of the CM shortbread cookie dough, indicating that the double gel dough is less yellow. Therefore, the shortbread cookies baked from the shortbread cookie dough with the double gel as the oil raw material are brighter ( Figure 2 Figure A).

[0094] 3. Microscopic Observation of Shortbread Cookie Doughs Made with Different Oils

[0095] From Figure 3It can be seen that there are a large number of air bubbles in the double-gel shortbread cookie dough. Among them, the number of air bubbles in the 1GM and 1PC shortbread cookie dough is large and uniform in size, while the air bubbles in the shortbread cookie dough made of CM are relatively large. The number of air bubbles in the 1GM, 1PC, and CM shortbread cookie dough is significantly more than that in the shortbread cookie dough with a ratio of 7:3 or 6:4. Moreover, the greater the viscosity of the dough, the more air bubbles. The above results indicate that the double-gel containing emulsifier has the ability to incorporate air bubbles during the whipping process and the dough has a certain air bubble stability.

[0096] 4. Viscosity Scanning of Different Shortbread Cookie Doughs

[0097] According to Figure 4 the viscosity scanning curves, as the shear rate increases, the apparent viscosity of each shortbread cookie dough shows a downward trend, exhibiting shear-thinning behavior, which may be due to the alignment of particles in the dough along the shear direction and the disruption of the internal interactions in the dough. At low shear rates of 0.1 - 0.2 s -1 −1, the apparent viscosity of the 6:4 cookie dough is significantly less than that of the 7:3 group and the CM group, indicating that as the proportion of the solution-state oil gel and hydrogel in the double-gel decreases, the apparent viscosity of the cookie dough decreases. The apparent viscosity of the 1PC and 1GM shortbread cookie doughs is significantly greater than that of the 7:3 group, which indicates that the double-gel containing emulsifier effectively reduces the apparent viscosity of the shortbread cookie dough when replacing margarine. At high shear rates, the viscosity of the CM shortbread cookie dough drops rapidly and is less than that of the double-gel cookie dough, which shows that the double-gel cookie dough containing emulsifier has strong internal interactions and good stability at high shear rates.

[0098] 5. Appearance of Shortbread Cookies Made with Different Oils

[0099] As Figure 5 shown in B, the L values of all shortbread cookies are greater than 50, and the a* and b* values are positive, indicating that the shortbread cookies appear bright, slightly red, and yellow. The L value of 1PC (55.40) is similar to that of CM (56.51), while the shortbread cookies prepared with 7:3 (61.55) and 1GM (63.77) as oil raw materials are brighter. The total color difference values of 7:3 and 1GM (68.80 and 71.38 respectively) are greater than those of 1PC and CM (63.18 and 62.79 respectively), which may be because the yellow color of PC and CM itself reduces the color difference value of the shortbread cookies. Therefore, the shortbread cookies baked with 1PC have a similar color to those baked with CM. In addition, the air holes at the bottom of the shortbread cookies made of CM are larger ( Figure 5 A), which is related to the fact that the viscosity of the CM dough is the largest ( Figure 4 ) resulting in larger air bubbles in the microstructure ( Figure 3 ) observed.

[0100] 6. Basic Properties of Different Shortbread Cookies

[0101] Table 2 shows the baking loss rate, diameter, thickness, puffiness, and extensibility of shortbread cookies made with different oils. The baking loss rate represents the loss of moisture in shortbread cookies during baking. As can be seen from the table, there is no significant difference in the baking loss rate of all shortbread cookies. Therefore, it can be excluded that the difference in the moisture content of shortbread cookies is caused by the loss of moisture during baking. Among them, the thickness of CM shortbread cookies is significantly smaller than that of shortbread cookies made with other oil types. This may be because the fat content in margarine is relatively high, weakening the network structure of gluten proteins in the dough, thereby inhibiting the expansion volume of cookies during baking and reducing the height of shortbread cookies. The higher the puffiness value and extensibility, the more crumbly the shortbread cookies are. Generally, when the extensibility is large, the cookies are crisper. There is no significant difference in the puffiness of shortbread cookies made with different oils. The extensibility of CM shortbread cookies is significantly greater than that of shortbread cookies made with double gel as the oil raw material. This is because the thickness of shortbread cookies decreases and the diameter does not change significantly, thus increasing the extensibility of shortbread cookies. The extensibility of 6:4 cookies is significantly smaller than that of CM cookies.

[0102] Table 2 Basic Properties of Shortbread Cookies Made with Different Oils

[0103]

[0104] * Different capital letters in the same column indicate significant differences between different oil gel and hydrogel ratios and the CM sample. Different lowercase letters in the same column indicate significant differences between different emulsifiers and the CM sample (p < 0.05).

[0105] 7. Moisture Content of Different Shortbread Cookies

[0106] From Figure 6 it can be seen that during the entire storage period, the moisture content of shortbread cookies is lower than 4%, meeting the moisture content standard for shortbread cookies. As the storage time increases, the moisture content of shortbread cookies generally shows an upward trend. Since CM itself does not contain water, its hygroscopicity is relatively low during storage. Due to the increased water absorption of cookies after adding emulsifiers, the moisture content of 1GM and 1PC shortbread cookies is slightly higher than that of 7:3 shortbread cookies ( Figure 6 B), while the 6:4 double gel increases the water absorption of shortbread cookies ( Figure 6 A).

[0107] 8. Texture Characteristics of Different Shortbread Cookies

[0108] Table 3 shows the changes in the texture properties of shortbread cookies during storage. As the number of storage days increases, the hardness of shortbread cookies generally shows a downward trend. On the 14th day, the hardness of each shortbread cookie decreased by 16.40%, 23.12%, 23.02%, and 14.30% compared to the first day of storage. The gradual decrease in the hardness of shortbread cookies may be due to the increase in the moisture content of shortbread cookies. In addition, the greater the hardness of the cookies, the smaller the crispness, and the lower the crispness of shortbread cookies. The hardness of the 6:4 shortbread cookies is significantly greater than that of the 7:3 and CM shortbread cookies, indicating that the preparation scheme without adding emulsifiers and with a double gel ratio of 6:4 is not conducive to improving the crispness of shortbread cookies. The hardness of the 1GM and 1PC shortbread cookies is significantly less than that of the 7:3 shortbread cookies and is closer to the hardness of commercially available margarine shortbread cookies, indicating that the double gel with added emulsifiers is more conducive to improving the crispness of shortbread cookies.

[0109] Table 3 Texture properties of shortbread cookies made with different oils during storage

[0110]

[0111]

[0112] * Different capital letters in the same column indicate significant differences between different oil gel and hydrogel ratios and the CM sample. Different lowercase letters in the same column indicate significant differences between different emulsifiers and the CM sample (p < 0.05).

[0113] 9. Sensory evaluation of shortbread cookies made with different oils

[0114] According to Figure 7For the results of sensory evaluation, there was no significant difference in the color scores of shortcrust biscuits made with double gel and margarine. The shape score of the shortcrust biscuits made with margarine (6.65) was significantly lower than that of the shortcrust biscuits made with 6:4, 7:3, 1GM, and 1PC (6.85, 7.35, 7.20, and 7.30 respectively), indicating that the shortcrust biscuits made with double gel had regular shapes and uniform thicknesses. The texture score of the shortcrust biscuits made with double gel was slightly lower than that of the shortcrust biscuits made with margarine, indicating that the shortcrust biscuits made with double gel were less delicate and crispy. In addition, the structure score of the shortcrust biscuits made with 1PC double gel was the highest (7.35), followed by those made with 1GM and 7:3 double gels (7.05 and 6.95 respectively), and the lowest for those made with 6:4 and CM (6.70 and 6.80). This shows that 1GM and 1PC double gels have the potential to make shortcrust biscuits with layered cross-sections and fine and uniform pores. The shortcrust biscuits made with the double gel of the present invention have the advantages of uniform color, regular shape, and layered cross-sections. Therefore, the double gel of the present invention can be used as a substitute for margarine in shortcrust biscuits.

[0115] The apparent viscosity of the biscuit dough with a solution-state oil gel and hydrogel ratio of 6:4 was smaller. The biscuits made had high moisture content and hardness, weak crispiness, and low scores for biscuit structure and shape. Adding GM and PC to the double gel with a solution-state oil gel and hydrogel ratio of 7:3 could improve the quality of the shortcrust biscuits made by substituting double gel for margarine. Compared with the shortcrust biscuits in the 7:3 group, adding emulsifiers helped reduce the hardness and moisture content of the biscuits during storage, enhance the crispiness of the biscuits, increase the structure score of the biscuits, and thus improve the sensory quality of the biscuits.

[0116] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, rather than limitations on the implementation manners of the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. Any modifications, equivalent replacements, and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the claims of the present invention.

Claims

1. A double gel, characterized in that: The components include liquid oil gel and hydrogel; the liquid oil gel component includes soybean oil, beef tallow, ethyl cellulose and emulsifier; the hydrogel component includes konjac glucomannan.

2. The double gel according to claim 1, characterized in that: The purity of the konjac glucomannan is not less than 86%, and the deacetylation degree is 40% to 60%.

3. The double gel according to claim 1, characterized in that: The emulsifier is a surface active emulsifier.

4. The double gel according to claim 1, characterized in that: The mass ratio of the soybean oil to the beef tallow is 6 to 9:

3.

5. The double gel according to claim 1, characterized in that: The mass ratio of the solution oil gel to the hydrogel is greater than 1.

5.

6. The double gel according to claim 1, characterized in that: The mass fraction of the emulsifier in the oil gel is 0.5% to 1.5%.

7. A method for preparing the double gel according to any one of claims 1 to 6, characterized in that: The following steps are involved: S1. Adding ethyl cellulose and an emulsifier to soybean oil and butter, heating and dissolving, and obtaining a solution oil gel; S2, konjac glucomannan is swollen in water and then heated to form a hydrogel; S3, the hydrogel and the solution-state oil gel are mixed, stirred and homogenized, cooled and allowed to stand, and a double gel is obtained.

8. The method for preparing the double gel according to claim 7, characterized in that: The heating temperature of S1 is 120-140°C, and the stirring is carried out at 100-300 r / min to dissolve.

9. An application of the double gel according to any one of claims 1 to 6, characterized in that: Used to prepare crispy biscuits.

10. A crisp biscuit, characterized in that: The method is prepared by using the double gel described in any one of claims 1 to 6.

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