Preparation method and application of edible skin protective agent for frozen green dough

Abstract

The invention discloses a preparation method and application of an edible skin protective agent for frozen green dough, and belongs to the technical field of food. The edible epidermis protective agent comprises the following components: acetylated distarch adipate, carboxymethyl cellulose, ascorbic acid, glycerol and water. The invention further discloses application of the skin protective agent in frozen green bodies, namely, the skin protective agent is prepared into a coating to be applied to frozen green body dough, and the frozen green body dough coated with the protective agent can keep good specific volume, height-diameter ratio, apparent color and texture quality after being subjected to freezing and thawing cycles. Meanwhile, the protective agent can also relieve dough skin damage caused by recrystallization and moisture migration of ice crystals and damage of a gluten protein network and starch particles in the freezing and thawing cycle process. The method is beneficial to improving the quality of the frozen green flour product, prolonging the preservation time and promoting the standardized and industrial production of the frozen green flour product.

Description

Technical Field

[0001] The invention belongs to the technical field of food, and in particular relates to a preparation method and application of an edible surface protective agent for frozen raw dough. Background Art

[0002] Frozen raw dough technology refers to a technology that uses a quick freezing method to mass-produce frozen raw dough in a centralized facility, and then transports it to local retail stores or chain markets to complete the remaining processing procedures. Compared with frozen cooked dough, the two high-energy-consuming processes of steaming and cooling are omitted, and the dough is directly quick-frozen. It does not need to be thawed or only thawed and proofed for a short time before it can be directly processed. It is a convenient, fast, energy-saving and environmentally friendly processing method. Frozen raw dough technology can ensure product safety, meet the needs of industrial production scale and product quality standardization, and is conducive to the business model of chain operation. It has the advantages of saving time, labor, materials, land, and ready-to-use. It has broad application prospects and great potential in fermented noodle staples. However, frozen raw dough products deteriorate in quality due to temperature fluctuations during storage and transportation, such as reduced specific volume, dark color, hard taste, damaged and cracked skin, etc., which ultimately affects the sales of frozen raw dough products. Therefore, it is of far-reaching significance to seek a method for targeted regulation of dough quality deterioration. In the prior art, the quality deterioration of frozen raw dough is mainly improved by adding improvers. Commonly used improvers include antifreeze polysaccharides, antifreeze proteins, hydrophilic colloids, modified starch, enzyme preparations and emulsifiers. Improvers can protect the network structure of gluten, reduce the growth and recrystallization of ice crystals in the dough, and thus improve the freeze-thaw stability of frozen dough. However, the effect of improvers on the surface protection of frozen dough dough is still unclear in current research, and the protection mechanism of the surface has not been fully studied; and because different improvers have different effects on frozen dough, in order to achieve the best effect, it is usually necessary to use a combination of multiple improvers. The increase in the amount of addition causes the content of each component in the frozen dough to change, which weakens the original structural characteristics of the dough, thereby affecting the quality of the frozen dough.

[0003] Edible coatings are mostly composed of natural polysaccharides, proteins, lipids and other edible substances. They can be covered on the surface of food by wrapping, coating and other methods to form a protective layer, which can effectively prevent the penetration of moisture, oxygen or other substances, and have good food preservation, anti-oxidation, water retention and other functions; and it is easy to compound various macromolecular functional components, can retain moisture and flavor substances, and show a wide range of applicability. Current edible coatings are mainly used for the refrigeration and preservation of fruits, vegetables and meats, but edible coatings have not been widely used in staple food products, especially frozen raw dough products. Although patent CN116135023B discloses the application of edible coatings to the water preservation and freshness of frozen raw dough dough, it does not mention how to use edible coatings to improve the quality deterioration of frozen raw dough dough after freezing and thawing, especially the problem of epidermal damage. Therefore, it is very necessary to find a suitable antifreeze modifier to prepare an edible coating to improve the freeze-thaw stability of frozen raw dough products, which is very necessary for improving the quality and epidermal deterioration of frozen raw dough products and expanding the consumer market. Summary of the invention

[0004] In view of the above-mentioned problems, the object of the present invention is to provide a method for improving the quality deterioration of frozen raw dough during the freeze-thaw cycle, namely, preparing an edible surface protective agent with acetylated distarch adipate and sodium carboxymethyl cellulose as main raw materials, and improving the quality of the dough after the freeze-thaw cycle by coating the surface of the frozen raw dough.

[0005] To achieve the above-mentioned purpose, the present invention first provides a method for preparing an edible surface protective agent for frozen raw dough, comprising the following steps:

[0006] (1) adding acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water and dissolving them to obtain a mixed solution;

[0007] (2) placing the mixed solution obtained in step (1) in a water bath and heating it while stirring it with a stirrer;

[0008] (3) adding glycerol to the mixture obtained in step (2) at room temperature and stirring with a stirrer;

[0009] (4) homogenizing the mixed solution obtained in step (3) using a homogenizer and cooling it to room temperature to obtain an edible epidermal protective agent.

[0010] In one embodiment of the present invention, the mass ratio of acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid in the mixed solution is (25-50):(25-50):1.

[0011] In one embodiment of the present invention, the degree of substitution of the acetylated distarch adipate is 0.03-0.04.

[0012] In one embodiment of the present invention, in step (2), the temperature of the water bath is controlled at 80-90° C., the speed of the stirrer is 250-400 rpm, and the heating time is 25-35 min.

[0013] In one embodiment of the present invention, in step (3), the amount of glycerol added is 1.5-3% of the total mass of the coating liquid.

[0014] In one embodiment of the present invention, in step (3), the speed of the stirrer is 250-400 rpm, and the stirring time is 3-5 min.

[0015] In one embodiment of the present invention, in step (4), the speed of the homogenizer during homogenization is 10000-12000 rpm, and the homogenization time is 2-4 min.

[0016] The invention also discloses an edible surface protective agent for frozen raw dough prepared by the preparation method.

[0017] In one embodiment of the present invention, the mass fractions of the components in the edible epidermal protective agent are: 1.5-3% acetylated distarch adipate, 1.5-3% carboxymethyl cellulose, 0.06% ascorbic acid, 2% glycerol, and the balance is water.

[0018] The invention also discloses an application of the frozen raw dough edible surface protective agent in preparing the frozen raw dough.

[0019] In one embodiment of the present invention, the application includes soaking the frozen raw dough in a frozen raw dough edible skin protective agent, suspending the dough in the air to remove excess protective agent solution, and then freezing the treated dough for storage and performing freeze-thaw cycles.

[0020] In one embodiment of the present invention, the immersion time is 1 to 3 minutes, and the suspended standing time is 1 to 3 minutes.

[0021] In one embodiment of the present invention, the freezing is performed at -40°C for 2 to 3 hours.

[0022] In one embodiment of the present invention, the storage is performed by freezing at -18 to -20°C for 23 hours.

[0023] In one embodiment of the present invention, one cycle of the freeze-thaw cycle is freezing and preserving at -18 to -20°C for 23 hours and thawing at 30 to 35°C for 1 hour.

[0024] In one embodiment of the present invention, the formula of the frozen raw dough is flour: water: leavening agent: yeast: sugar: lard = 100: (40-60): (1-1.5): (1-1.5): 1:1.

[0025] Beneficial effects:

[0026] (1) The present invention utilizes an edible surface protective agent to improve the quality deterioration of frozen raw dough during the freeze-thaw cycle, wherein the main raw materials of the edible surface protective agent are acetylated distarch adipate and sodium carboxymethyl cellulose. Acetylated distarch adipate is a modified starch obtained by esterification reaction of acetic anhydride and adipic anhydride with starch. Compared with native starch, it has good freeze-thaw resistance, stability and texture improvement effect, and is widely used as a stabilizer, thickener and texture protective agent. Sodium carboxymethyl cellulose is a water-soluble polysaccharide obtained by chemical modification of natural cellulose. Due to its good water retention and film-forming properties, it is used for food preservation and anti-oxidation. Both of them will not affect human health. According to the provisions of the national standard GB 2760-2014, there is no rigid regulation on the dosage of the two, and they can be used in appropriate amounts according to production needs. Therefore, the edible surface protective agent in the present invention is highly safe and can be widely used in frozen raw products.

[0027] (2) In the present invention, the frozen raw dough is coated with an edible surface protective agent, which can maintain good specific volume, height-to-diameter ratio, apparent color and texture quality of the frozen raw dough; at the same time, the surface protective agent can also alleviate the damage to the dough surface caused by the recrystallization of ice crystals of precipitated water, the destruction of gluten protein network and starch granules during the freeze-thaw cycle. Compared with the traditional method of directly adding a improver to the dough, the edible surface protective agent has less impact on the dough and will not weaken the structural characteristics of the dough itself, so it has high practicality.

[0028] (3) The preparation method of the present invention is relatively simple, easy to operate, low in cost, does not require special equipment, and can be implemented in ordinary households, factories or laboratories. It can be prepared in smaller containers, with less waste, higher safety, reduced pollution, and higher market and application value; and the cost is low, with broad economic benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 The photos are the appearance photos of steamed bread after the frozen raw dough of each embodiment (AC) and comparative example (DG) was steamed through freeze-thaw cycle;

[0030] Figure 2 The SEM images of the outer skin of the steamed buns of Comparative Example 1 (A) and Example 1 (B) after the frozen raw dough was steamed in a freeze-thaw cycle. DETAILED DESCRIPTION

[0031] After long-term research and extensive practice, the inventor of this case was able to propose the technical solution of the present invention. The following will further explain the technical solution, its implementation process and the results of its action.

[0032] The technical scheme of the present invention is further described in detail by several examples below. However, the selected examples are only used to illustrate the present invention, and do not limit the scope of the present invention. The following test methods are used in the examples and comparative examples of the present invention:

[0033] Preparation of frozen dough

[0034] Put flour, water, leavening agent, yeast, sugar and lard into a dough mixer in the ratio of 100:50:1:1:1:1, mix and knead for 10 minutes to obtain a smooth dough. Manually divide the dough into 50 g pieces, knead it into round shapes, and obtain frozen raw dough.

[0035] Freeze-thaw cycle experiment

[0036] The freeze-thaw cycle experiment was used to simulate the temperature fluctuations that occur during actual transportation. The frozen raw dough was frozen at -18°C for 23 hours and thawed at 35°C for 1 hour, which was considered as one freeze-thaw cycle (1F / T).

[0037] Preparation of frozen raw steamed bread

[0038] The frozen dough that has undergone a freeze-thaw cycle was placed in a preheated steamer and steamed for 20 minutes, followed by cooling for 10 minutes.

[0039] Method for determination of specific volume

[0040] The steamed frozen raw steamed buns were cooled at room temperature for 10 min, and their volumes were measured by millet displacement method to calculate the specific volume (v / m).

[0041] Method for determining aspect ratio

[0042] The height (H) and diameter (D) of the steamed frozen raw dough were measured using a vernier caliper, and the height-to-diameter ratio (H / D) was calculated.

[0043] Determination of apparent color

[0044] After the steamed frozen raw dough was cooled at room temperature for 10 minutes, the apparent color of the sample was measured with a spectrophotometer. L* represents brightness (0 white ~ 100 black), a* represents red-green value (+ direction represents an increase in red value, - direction represents an increase in green value), and b* represents yellow-blue value (+ direction represents an increase in yellow value, - direction represents an increase in blue value). ΔE is calculated as follows:

[0045]

[0046] Wherein ΔL, Δa, Δb are the differences in L*, a*, b* values ​​at 0F / T between each embodiment and comparative example and comparative example 1.

[0047] Methods for determination of texture quality

[0048] After the steamed frozen dough was cooled at room temperature for 10 min, the steamed dough was cut into slices with a thickness of 15 mm and the sample texture was measured using a physical property analyzer equipped with a diameter of 25 mm (TA / 25) in (TPA) mode. The speed before the test was 2.00 mm / s; the speed during the test was 1.00 mm / s; the test speed was 1.00 mm / s; the trigger force was 5 g; the strain was 50%; and the pause time between each compression cycle was 5 s.

[0049] SEM images

[0050] The steamed frozen raw dough was cooled at room temperature for 10 min, and then the skin was removed for freeze-drying. The freeze-dried skin was cut into small square cubes with a side length of about 5 mm, attached to the stage with conductive adhesive, sprayed with gold, and the microstructure of the outer skin was observed at a magnification of 5000 times at an accelerating voltage of 3 KV.

[0051] Example 1

[0052] The mass fractions of the components of an edible epidermal protective agent are as follows: 3% acetylated distarch adipate, 3% carboxymethyl cellulose, 0.06% ascorbic acid, 2% glycerol and 91.94% water.

[0053] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0054] S1, adding weighed acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water to dissolve to obtain a mixed solution;

[0055] S2. Place the mixed solution in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0056] S3, adding glycerol to the mixture obtained in step S2 at room temperature, and stirring with a stirrer for 3 minutes at a stirring speed of 300 rpm;

[0057] S4. Use a homogenizer to homogenize the mixed solution obtained in step S3. The speed of the homogenizer is 10000 rpm. The homogenization is performed for 3 minutes. After homogenization, the mixture is cooled to room temperature to obtain an edible epidermal protective agent.

[0058] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0059] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0060] (2) The prepared frozen raw dough was placed in an edible skin protective agent, soaked for 1 minute, taken out and suspended in the air for 1 minute to remove excess protective agent solution, and frozen at -40°C for 2 hours before a freeze-thaw cycle.

[0061] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0062] Example 2

[0063] The mass fractions of the components of an edible epidermal protective agent are as follows: 1.5% of acetylated distarch adipate, 3% of carboxymethyl cellulose, 0.06% of ascorbic acid, 2% of glycerol and 93.44% of water.

[0064] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0065] S1, adding weighed acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water to dissolve to obtain a mixed solution;

[0066] S2. Place the mixed solution in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0067] S3, adding glycerol to the mixture obtained in step S2 at room temperature, and stirring with a stirrer for 3 minutes at a stirring speed of 300 rpm;

[0068] S4. Use a homogenizer to homogenize the mixed solution obtained in step S3. The speed of the homogenizer is 10000 rpm. The homogenization is performed for 3 minutes. After homogenization, the mixture is cooled to room temperature to obtain an edible epidermal protective agent.

[0069] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0070] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0071] (2) The prepared frozen raw dough was placed in an edible skin protective agent and soaked for 1 minute. The dough was taken out and suspended in the air for 1 minute to remove excess protective agent solution. The dough was frozen at -40°C for 2 hours and then subjected to a freeze-thaw cycle.

[0072] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0073] Example 3

[0074] The mass fractions of the components of an edible epidermal protective agent are as follows: 3% acetylated distarch adipate, 1.5% carboxymethyl cellulose, 0.06% ascorbic acid, 2% glycerol and 93.44% water.

[0075] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0076] S1, adding weighed acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water to dissolve to obtain a mixed solution;

[0077] S2. Place the mixed solution in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0078] S3, adding glycerol to the mixture obtained in step S2 at room temperature, and stirring with a stirrer for 3 minutes at a stirring speed of 300 rpm;

[0079] S4. Use a homogenizer to homogenize the mixed solution obtained in step S3. The speed of the homogenizer is 10000 rpm. The homogenization is performed for 3 minutes. After homogenization, the mixture is cooled to room temperature to obtain an edible epidermal protective agent.

[0080] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0081] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0082] (2) The prepared frozen raw dough was placed in an edible skin protective agent, soaked for 1 minute, taken out and suspended in the air for 1 minute to remove excess protective agent solution, and frozen at -40°C for 2 hours before a freeze-thaw cycle.

[0083] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0084] Comparative Example 1

[0085] The difference between Comparative Example 1 and Example 1 is that the frozen raw dough is not immersed in the edible skin protective agent.

[0086] Put flour, water, leavening agent, yeast, sugar and lard into a dough mixer in the ratio of 100:50:1:1:1:1, mix and knead for 10 minutes to obtain a smooth dough. Divide the dough into 50 g pieces manually and shape them into round shapes to obtain frozen green dough. Freeze at -40°C for 2 hours and then perform a freeze-thaw cycle.

[0087] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0088] Comparative Example 2

[0089] The difference between Comparative Example 2 and Example 1 is that the mass fractions of the components of the edible epidermal protective agent are: 3% acetylated distarch adipate, 0.06% ascorbic acid, 2% glycerol, and 94.94% water.

[0090] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0091] S1. Add weighed acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water and dissolve;

[0092] S2. Place the sample in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0093] S3, adding glycerol to the sample at room temperature, stirring with a stirrer for 3 minutes at a speed of 300 rpm;

[0094] S4. Use a homogenizer to homogenize the sample at a speed of 10,000 rpm for 3 minutes. After homogenization, cool to room temperature to obtain an edible epidermal protective agent.

[0095] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0096] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0097] (2) The prepared frozen raw dough was placed in an edible skin protective agent, soaked for 1 minute, taken out and suspended in the air for 1 minute to remove excess protective agent solution, and frozen at -40°C for 2 hours before a freeze-thaw cycle.

[0098] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0099] Comparative Example 3

[0100] The difference between Comparative Example 3 and Example 1 is that the mass fractions of the components of the edible epidermal protective agent are: 3% sodium carboxymethyl cellulose, 0.06% ascorbic acid, 2% glycerol, and 94.94% water.

[0101] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0102] S1. Add weighed acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water and dissolve;

[0103] S2. Place the sample in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0104] S3, adding glycerol to the sample at room temperature, stirring with a stirrer for 3 minutes at a speed of 300 rpm;

[0105] S4. Use a homogenizer to homogenize the sample at a speed of 10,000 rpm for 3 minutes. After homogenization, cool to room temperature to obtain an edible epidermal protective agent.

[0106] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0107] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0108] (2) The prepared frozen raw dough was placed in an edible skin protective agent, soaked for 1 minute, taken out and suspended in the air for 1 minute to remove excess protective agent solution, and frozen at -40°C for 2 hours before a freeze-thaw cycle.

[0109] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0110] Comparative Example 4

[0111] The difference between Comparative Example 4 and Example 1 is that the mass fractions of the components of the edible epidermal protective agent are: 3% hydroxypropyl distarch phosphate, 3% carboxymethyl cellulose, 0.06% ascorbic acid, 2% glycerol, and 91.94% water.

[0112] A method for preparing an edible surface protective agent for frozen raw dough comprises the following steps:

[0113] S1. Add weighed hydroxypropyl distarch phosphate, carboxymethyl cellulose and ascorbic acid into water and dissolve them;

[0114] S2. Place the sample in a water bath and heat at 80°C for 30 min while stirring with a stirrer at a speed of 300 rpm;

[0115] S3, adding glycerol to the sample at room temperature, stirring with a stirrer for 3 minutes at a speed of 300 rpm;

[0116] S4. Use a homogenizer to homogenize the sample at a speed of 10,000 rpm for 3 minutes. After homogenization, cool to room temperature to obtain an edible epidermal protective agent.

[0117] Application of an edible surface protective agent for frozen raw dough in frozen raw dough, the application comprising the following steps:

[0118] (1) putting flour, water, leavening agent, yeast, sugar, and lard in a dough mixer in a ratio of 100:50:1:1:1:1 and mixing for 10 minutes to obtain a smooth dough, manually dividing the dough into 50 g pieces, kneading the pieces into round shapes, and obtaining a frozen green dough;

[0119] (2) The prepared frozen raw dough was placed in an edible skin protective agent, soaked for 1 minute, taken out and suspended in the air for 1 minute to remove excess protective agent solution, and frozen at -40°C for 2 hours before a freeze-thaw cycle.

[0120] Frozen raw dough with 0, 3, and 5 freeze-thaw cycles was selected and steamed in a preheated steamer for 20 min. After cooling at room temperature for 10 min, its specific volume, aspect ratio, apparent color, texture quality and SEM image were measured.

[0121] Experimental results:

[0122] The specific measurement results of each embodiment and comparative example are shown in Tables 1-4.

[0123] Table 1 Specific volume change of the frozen raw dough prepared in each embodiment and comparative example during the freeze-thaw cycle (unit: mL / g)

[0124]

[0125] Note: The values ​​in the table are expressed as mean ± standard deviation; different lowercase letters indicate significant differences in the same column (p<0.05).

[0126] Table 2 Changes in height-to-diameter ratio of the frozen raw dough prepared in each embodiment and comparative example during freeze-thaw cycle

[0127]

[0128] Note: The values ​​in the table are expressed as mean ± standard deviation; different lowercase letters indicate significant differences in the same column (p<0.05).

[0129] As can be seen from Tables 1 and 2, after multiple freeze-thaw cycles, the specific volume and height-to-diameter ratio of the frozen raw dough in Comparative Example 1 that was not coated with an edible epidermal protective agent both decreased. Compared with 0F / T, the specific volume of the dough decreased by 29% and the height-to-diameter ratio decreased by 40% at 5F / T, which indicates that the freeze-thaw cycle destroyed the structure of the dough and reduced the extensibility of the dough. The specific volume of the dough in Examples 1-3 decreased by 21%, 26% and 25% at 5F / T, respectively, and the height-to-diameter ratio decreased by 36%, 27% and 35%, respectively, which was less than that in Comparative Example 1. This is because the addition of the edible coating reduces the loss of yeast in the freeze-thaw cycle, which increases the yeast gas production; and due to the formation of the coating, the gluten network and starch granules are protected from damage during frozen storage, thereby reducing the loss of water to the external medium. At 5F / T, the specific volume of Examples 1-3 is increased by 6-15% and the aspect ratio is increased by 7-12% compared with Comparative Example 1, which is also higher than the improvement of the specific volume and aspect ratio of the frozen raw dough in Comparative Examples 2-4. This shows that the edible epidermal protective agent prepared by acetylated distarch adipate and carboxymethyl cellulose has a stronger effect on improving the freeze-thaw damage of frozen raw dough than a single modified starch or polysaccharide coating liquid, and the effect of acetylated distarch adipate is stronger than hydroxypropyl distarch phosphate.

[0130] Table 3 Apparent color changes of the frozen raw dough prepared in each embodiment and comparative example during the freeze-thaw cycle

[0131]

[0132]

[0133] Note: The values ​​in the table are expressed as mean ± standard deviation; different letters indicate that there are significant differences among different treatments under the same number of freeze-thaw cycles (p<0.05).

[0134] As shown in Table 3, as the number of freeze-thaw cycles increases, the brightness of the frozen raw dough gradually decreases, the dough color becomes darker and yellower, and the color difference gradually increases. This is because the enzymatic browning of the dough surface during the frozen storage and freeze-thaw process causes the apparent color of the dough to darken and the color difference to increase. Compared with the frozen raw dough of Comparative Example 1, the dough coated with a surface coating protective agent composed of modified starch and polysaccharides increases in brightness and reduces the color difference after experiencing freeze-thaw cycles. This is because the coating liquid forms a protective layer on the dough surface, reducing the enzymatic browning reaction on the dough surface; and the raw materials such as modified starch in the coating liquid have high brightness, which can enhance the apparent color of the dough. At the same time, under the same number of freeze-thaw cycles, the brightness of Examples 1-3 increased and the color difference decreased compared with Comparative Examples 2-4, which indicates that the edible epidermal protective agent prepared by acetylated distarch adipate and carboxymethyl cellulose has a stronger effect on improving the apparent color of frozen raw dough than a single modified starch or polysaccharide coating liquid, and the effect of acetylated distarch adipate is stronger than that of hydroxypropyl distarch phosphate.

[0135] Table 4 Texture changes of the frozen raw dough prepared in each embodiment and comparative example during the freeze-thaw cycle

[0136]

[0137]

[0138] Note: The values ​​in the table are expressed as mean ± standard deviation; different letters indicate that there are significant differences among different treatments under the same number of freeze-thaw cycles (p<0.05).

[0139] Table 4 shows the changes in the hardness, elasticity and chewiness of the frozen dough during the freeze-thaw cycle. As the number of freeze-thaw cycles increases, the hardness, elasticity and chewiness of the frozen dough increase. This is because the freeze-thaw cycle causes the formation and recrystallization of ice crystals, destroying the internal structure of the dough. After multiple freeze-thaw cycles, the hardness, elasticity and chewiness of the frozen dough coated with the epidermal coating protective agent in Examples 1-3 are significantly lower than those of Comparative Example 1, and are also lower than those of Comparative Examples 2 and 3 coated with a single acetylated distarch adipate or carboxymethyl cellulose. At the same time, compared with Comparative Example 4, the coating liquid with acetylated distarch adipate as the raw material has a better effect than the coating liquid with hydroxypropyl distarch phosphate added. The above results show that the edible epidermal protective agent prepared by modified starch and polysaccharide has a stronger effect on the improvement of the texture deterioration of frozen dough than the single modified starch or polysaccharide coating liquid, and the effect of acetylated distarch adipate is stronger than that of hydroxypropyl distarch phosphate.

[0140] Figure 1 The following are photos of the appearance of the frozen raw dough of each embodiment and comparative example after freeze-thaw cycle steaming. As can be seen from the figure, the frozen raw dough of comparative example 1, which does not use a surface coating protective agent, has a darker surface color after undergoing a freeze-thaw cycle, and has large cracks and bubbles, and the surface becomes rough. This is because the water in the dough is separated and gathered near the surface during the freeze-thaw process, and the formation and recrystallization of ice crystals cause mechanical damage to the gluten protein and starch granules on the surface. Compared with comparative examples 1-4, after experiencing the same number of freeze-thaw cycles, the surface of the dough of Examples 1-3 is more delicate and smooth, with higher brightness, and no obvious cracks and bubbles appear. This is because the edible surface protective agent prepared from modified starch and polysaccharides forms a protective film on the surface of the dough, which reduces the formation of ice crystals on the surface of the dough, thereby protecting the gluten protein structure and starch granules. The above results show that the edible surface protective agent prepared by modified starch and polysaccharide has a stronger effect on improving the surface of frozen raw dough than single modified starch or polysaccharide coating liquid, and the effect of acetylated distarch adipate is stronger than hydroxypropyl distarch phosphate.

[0141] Figure 2The microstructure of the outer skin of the steamed buns after the frozen raw dough of Example 1 and Comparative Example 1 was steamed through a freeze-thaw cycle is shown. As can be seen from the figure, the frozen raw dough in Comparative Example 1 has a generally fine and uniform skin before being frozen and thawed, with occasional exposed starch granules, but the granules are relatively round and complete. With the increase in the number of freeze-thaw cycles, the starch granules in the skin gradually emerge from the gluten protein, and are damaged and twisted, which indicates that the freeze-thaw cycle destroys the structure of the gluten protein and starch granules in the skin, causing damage to the skin of the dough. After the skin of the frozen raw dough in Example 1 is coated with an edible skin protective agent, the modified starch and polysaccharide in the coating liquid combine with the gluten protein and starch granules to form a protective film on the surface of the dough, so that the starch granules will not be exposed due to the damage of the gluten protein after the dough undergoes a freeze-thaw cycle, thereby reducing the damage to the skin of the dough.

[0142] The embodiments provided above are not intended to limit the scope of the present invention, and the steps described are not intended to limit the execution order thereof. Those skilled in the art may make obvious improvements to the present invention in combination with existing common knowledge, which also fall within the scope of protection defined by the claims of the present invention.

Claims

1. A frozen raw dough edible skin protective agent, characterized in that: The mass fractions of the components in the edible epidermal protective agent are: 1.5-3% of acetylated distarch adipate, 1.5-3% of carboxymethyl cellulose, 0.06% of ascorbic acid, 2% of glycerol, and the balance of water.

2. A method for preparing an epidermal protective agent according to claim 1, characterized in that: The steps include: (1) adding acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid into water and dissolving them to obtain a mixed solution; (2) placing the mixed solution obtained in step (1) in a water bath and heating it while stirring it with a stirrer; (3) adding glycerol to the mixture obtained in step (2) at room temperature and stirring with a stirrer; (4) homogenizing the mixed solution obtained in step (3) using a homogenizer and cooling it to room temperature to obtain an edible epidermal protective agent.

3. The preparation method according to claim 2, characterized in that: The mass ratio of acetylated distarch adipate, carboxymethyl cellulose and ascorbic acid in the mixed solution of step (1) is 25-50:25-50:1, and the degree of substitution of the acetylated distarch adipate is 0.03-0.

04.

4. The preparation method according to claim 2, characterized in that: In step (2), the temperature of the water bath is controlled at 80-90° C., the speed of the stirrer is 250-400 rpm, and the heating time is 25-35 min.

5. The preparation method according to claim 2, characterized in that: In step (3), the amount of glycerol added is 1.5-3% of the total mass of the coating liquid, the speed of the stirrer is 250-400 rpm, and the stirring time is 3-5 minutes.

6. The preparation method according to claim 2, characterized in that: In step (4), the speed of the homogenizer during homogenization is 10000-12000 rpm, and the homogenization time is 2-4 min.

7. Use of the edible epidermal protective agent according to claim 1 in preparing frozen raw dough.

8. The use according to claim 7, characterized in that: The application comprises soaking the frozen raw dough in an edible surface protective agent of the frozen raw dough, leaving it in suspension to remove excess protective agent solution, freezing and preserving the processed dough, and performing freeze-thaw cycles, wherein the soaking time is 1 to 3 minutes and the suspension time is 1 to 3 minutes.

9. The use according to claim 8, characterized in that: The freezing is performed at -40°C for 2 to 3 hours and then stored at -18 to -20°C for 23 hours. One cycle of the freeze-thaw cycle is performed at -18 to -20°C for 23 hours and then thawed at 30 to 35°C for 1 hour.

10. The use according to claim 8, characterized in that: The formula of the frozen raw dough is flour: water: leavening agent: yeast: white sugar: lard = 100:40-60:1-1.5:1-1.5:1:1.

Images