Frozen dough with high yeast activity and preparation method thereof

Abstract

The invention provides frozen dough with high yeast activity and a preparation method thereof, and the preparation method comprises the following steps: S1, respectively weighing flour, table salt and trehalose according to a formula to prepare a mixed material; s2, adding water and a yeast microsphere emulsion into the mixed material, and stirring to obtain fresh dough; and S3, carrying out heat-moisture treatment on the fresh dough, cutting into small pieces of dough, putting into a preservative film, sealing, quickly freezing in a refrigerator at the temperature of-40 DEG C for 90 minutes until the central temperature of the dough reaches-18 DEG C, and freezing to obtain the frozen dough with high yeast activity. Emulsion prepared from carboxymethyl apple pectin and peanut protein enzymatic hydrolysate is adopted to coat yeast cells, the yeast microsphere emulsion is prepared, the gluten network structure is enhanced, the crystallization and growth rate of ice are controlled, the yeast cells are protected, and the fermentation performance of the yeast cells is improved; meanwhile, the dough is subjected to heat-moisture treatment, so that the stability and the gas holding capacity of a gluten network of the dough can be enhanced, and the quality of the frozen dough is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to frozen dough with high yeast activity and a preparation method thereof. Background Art

[0002] Frozen dough is made by using freezing and refrigeration technology. It uses flour as the main raw material, adds yeast, salt, sucrose, eggs, milk powder and other auxiliary materials, adds water and stirs to form dough after fermentation, then freezes and refrigerates. When it is used, it only needs to be thawed, put into the oven and baked to get fresh baked food. Due to its convenience and large-scale production, it has gradually been accepted by the baking industry. However, there are still some difficult problems in frozen dough: ice crystals formed during the freezing process of frozen dough will destroy the gluten network structure, reduce the dough's gas holding capacity and reduce the specific volume of bread; freezing will also cause the water in the yeast cells to form ice crystals. These ice crystals destroy the organizational structure of the yeast cells, causing the yeast cytoplasmic components to leak and release the reducing substance glutathione, thereby weakening the gluten structure. Frozen dough has many advantages such as saving processing time, space, equipment and labor costs. Despite years of research on frozen dough, the problem of maintaining yeast activity during frozen storage still exists. Yeast activity is a key factor affecting the quality of frozen dough, and yeast protection is also a hot spot and difficulty in the field of frozen dough research. The antifreeze property of yeast is directly related to the content of protective metabolites such as trehalose, glycerol and proline in its cells. Conventional single gene knockout or overexpression methods are usually ineffective in improving yeast freezing tolerance. The methods reported in literature and patents that directly add hydrophilic colloids (such as xanthan gum, polyglutamic acid) and additives such as trehalose to improve the activity of yeast in frozen dough only involve physical protection, and do not fundamentally change the growth characteristics of yeast cells to adapt them to the freezing environment, so they are often ineffective. Summary of the invention

[0003] Technical problems to be solved: In view of the above technical problems, the purpose of the present invention is to provide a frozen dough with high yeast activity and a preparation method thereof, using an emulsion prepared from carboxymethyl apple pectin and peanut protein hydrolysate to coat yeast cells. First, after the apple pectin is modified by carboxymethylation, the cross-linking between the gluten network can be enhanced and the gluten strength can be improved; more carboxymethyl groups can form hydrogen bonds with water molecules and bind more water, thereby better controlling the crystallization and growth rate of ice; the enzymatic hydrolysate obtained by enzymatic hydrolysis of peanut protein can form an emulsion with carboxymethyl apple pectin, thereby embedding yeast and reducing the damage of ice crystals to yeast; the peanut protein hydrolysate can also promote yeast growth and improve its fermentation performance; finally, the dough is subjected to wet heat treatment, which can also enhance the stability and gas holding capacity of the dough gluten network.

[0004] Technical solution: A frozen dough with high yeast activity comprises the following components: 70-80 parts of flour, 50-55 parts of water, 0.5-1 part of salt, 5-8 parts of yeast microsphere emulsion and 0.5-0.8 part of trehalose. Furthermore, the yeast microsphere emulsion is prepared by coating yeast cells with an emulsion prepared from carboxymethyl apple pectin and peanut proteinase hydrolysate. Furthermore, the preparation steps of the yeast microsphere emulsion are: (1) dispersing apple pectin in 80% ethanol solution, adding 38% NaOH, and then adding 8.5% chloroacetic acid, stirring evenly to obtain an apple pectin solution; (2) heating the apple pectin solution to 60-80° C., stirring continuously for 1 hour, cooling, centrifuging at 6000-8000 r / min for 5-8 minutes, washing the obtained particles with ethanol, and drying at 80° C. to obtain carboxymethyl apple pectin for later use; (3) preparing a solution with peanut protein and water in a ratio of 1:(13-15), and mixing the mixture to obtain a mixed solution; (4) heating the mixed solution at 80° C. for 10 min, cooling it to 60-65° C., adding papain for enzymolysis for 6-9 h, boiling it for 10 min to inactivate the enzyme, centrifuging it at 6000-8000 r / min for 8-10 min, and taking the supernatant to obtain a peanut protein hydrolysate; (5) Dissolve carboxymethyl apple pectin in water, add peanut protein hydrolysate, stir evenly, add activated yeast, and homogenize to obtain yeast microsphere emulsion. Furthermore, in the step (1), the mass volume ratio of apple pectin to ethanol solution is 1:(10-11); and the mass volume ratio of apple pectin to NaOH is 1:(8-10). Furthermore, the amount of papain added in step (4) is 0.5-0.8%. Furthermore, in the step (5), the mass volume ratio of carboxymethyl apple pectin to peanut protein hydrolysate is (1-2):1; and the amount of activated yeast added is 10-30%. Furthermore, in step (5), the homogenization speed is 3000-5000 r / min, and the homogenization time is 3-6 min. Furthermore, the method for preparing the frozen dough with high yeast activity comprises the following steps: S1. Weigh flour, salt and trehalose according to the recipe and mix them evenly to obtain a mixture; S2. Add water and yeast microsphere emulsion to the mixture, stir at a low speed for 2-3 minutes, and then stir at a high speed for 2-4 minutes to obtain fresh dough; S3. Place the fresh dough under 20-25% RH and 140-145°C conditions for wet heat treatment for 5-10 minutes, cut it into small pieces of dough of 60-80g, put it in plastic wrap, seal it, and quickly freeze it in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and freeze it to obtain frozen dough with high yeast activity. Beneficial effects: 1. The yeast microsphere emulsion prepared by the present invention is specifically prepared by coating yeast cells with an emulsion prepared from carboxymethyl apple pectin and peanut protein hydrolysate. Firstly, the apple pectin itself, as a hydrophilic colloid, can enhance the cross-linking between gluten networks and improve the gluten strength; it can also reduce the migration of water and inhibit the growth of ice crystals, thereby reducing the damage to the gluten structure and yeast; secondly, the apple pectin is modified by carboxymethylation, and the carboxymethyl group is more conducive to combining excess water, controlling the ice crystallization and growth rate, and making the dough more stable after long-term frozen storage. 2. The peanut protein hydrolysate prepared by the present invention can form an emulsion with carboxymethyl apple pectin, which plays a role in embedding yeast cells, protecting yeast cells from damage by ice crystals, and reducing yeast mortality; at the same time, the enzymatic hydrolysate also has the effect of promoting yeast growth and improving yeast fermentation performance. Therefore, carboxymethyl apple pectin and peanut protein hydrolysate synergistically enhance the effect, maintain and improve the activity and fermentation ability of yeast. 3. The present invention performs wet heat treatment on the dough. Appropriate wet heat treatment can enhance the strength and stability of the gluten network, protect the structure of the dough during the freezing process, and thus improve the quality of the frozen dough. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 This is a graph showing the survival rate of yeast in frozen dough prepared in Example 9 and Comparative Examples 2-5. DETAILED DESCRIPTION The present invention is further described below in conjunction with the accompanying drawings and embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments: Example 1 The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 20 L of 80% ethanol solution, add 16 L of 38% NaOH, and then add 3.06 L of chloroacetic acid, stir evenly, and obtain an apple pectin solution; (2) heating the apple pectin solution to 60° C., stirring continuously for 1 h, cooling, and centrifuging at 6000 r / min for 8 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 13 L of water to prepare a solution, and the mixture was mixed to obtain a mixed solution; (4) heating the mixed solution at 80° C. for 10 min and then cooling it to 60° C., adding 0.5% papain for enzymatic hydrolysis for 6 h, boiling it for 10 min to inactivate the enzyme, centrifuging it at 6000 r / min for 10 min, and collecting the supernatant to obtain peanut protein hydrolysate; (5) Dissolve 1 kg of carboxymethyl apple pectin in water, add 1 L of peanut protein hydrolysate, stir evenly, add 10% activated yeast, and homogenize at 3000 r / min for 6 min to obtain yeast microsphere emulsion. Example 2 The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 20 L of 80% ethanol solution, add 16 L of 38% NaOH, and then add 3.06 L of chloroacetic acid, stir evenly, and obtain an apple pectin solution; (2) heating the apple pectin solution to 65° C., stirring continuously for 1 h, cooling, and centrifuging at 6000 r / min for 7 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 13 L of water to prepare a solution, and the mixture was mixed to obtain a mixed solution; (4)7 The mixed solution was heated at 80°C for 10 min and then cooled to 60°C, 0.6% papain was added for enzymatic hydrolysis for 7 h, the enzyme was inactivated by boiling for 10 min, and the mixture was centrifuged at 6000 r / min for 9 min. The supernatant was collected to obtain peanut protein hydrolysate; (5) Dissolve 1 kg of carboxymethyl apple pectin in water, add 1 L of peanut protein hydrolysate, stir evenly, add 10% activated yeast, and homogenize at 4000 r / min for 5 min to obtain yeast microsphere emulsion. Example 3 The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 22 L of 80% ethanol solution, add 18 L of 38% NaOH, and then add 3.4 L of chloroacetic acid, stir evenly, and obtain an apple pectin solution; (2) heating the apple pectin solution to 70° C., stirring continuously for 1 h, cooling, and centrifuging at 7000 r / min for 6 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 14 L of water to prepare a solution, and the mixture was mixed to obtain a mixed solution; (4) The mixed solution was heated at 80° C. for 10 min and then cooled to 65° C., 0.7% papain was added for enzymatic hydrolysis for 8 h, the mixture was boiled for 10 min to inactivate the enzyme, and the mixture was centrifuged at 7000 r / min for 9 min. The supernatant was collected to obtain peanut protein hydrolysate; (5) Dissolve 1 kg of carboxymethyl apple pectin in water, add 0.67 L of peanut protein hydrolysate, stir evenly, add 20% activated yeast, and homogenize at 4000 r / min for 4 min to obtain yeast microsphere emulsion. Example 4 The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 22 L of 80% ethanol solution, add 20 L of 38% NaOH, and then add 3.58 L of chloroacetic acid, stir evenly to obtain an apple pectin solution; (2) heating the apple pectin solution to 80° C., stirring continuously for 1 h, cooling, and centrifuging at 8000 r / min for 5 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 15 L of water to prepare a solution, and the mixture was mixed to obtain a mixed solution; (4) heating the mixed solution at 80° C. for 10 min and then cooling it to 65° C., adding 0.8% papain for enzymatic hydrolysis for 9 h, boiling it for 10 min to inactivate the enzyme, centrifuging it at 8000 rpm for 8 min, and collecting the supernatant to obtain peanut protein hydrolysate; (5) Dissolve 1 kg of carboxymethyl apple pectin in water, add 0.5 L of peanut protein hydrolysate, stir evenly, add 25% activated yeast, and homogenize at 5000 r / min for 3 min to obtain yeast microsphere emulsion. Example 5 The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 20 L of 80% ethanol solution, add 20 L of 38% NaOH, and then add 3.4 L of chloroacetic acid, stir evenly to obtain an apple pectin solution; (2) heating the apple pectin solution to 80° C., stirring continuously for 1 h, cooling, and centrifuging at 8000 r / min for 5 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 15 L of water to prepare a solution, and the mixture was mixed to obtain a mixed solution; (4) heating the mixed solution at 80° C. for 10 min and then cooling it to 65° C., adding 0.8% papain for enzymatic hydrolysis for 9 h, boiling it for 10 min to inactivate the enzyme, centrifuging it at 8000 rpm for 8 min, and collecting the supernatant to obtain peanut protein hydrolysate; (5) Dissolve 1 kg of carboxymethyl apple pectin in water, add 0.5 L of peanut protein hydrolysate, stir evenly, add 30% activated yeast, and homogenize at 5000 r / min for 3 min to obtain yeast microsphere emulsion. Comparative Example 1 The difference between this comparative example and Example 3 is that peanut protein is used to prepare the yeast microsphere emulsion, which is as follows: The preparation steps of yeast microsphere emulsion are as follows: (1) Disperse 2 kg of apple pectin in 22 L of 80% ethanol solution, add 18 L of 38% NaOH, and then add 3.4 L of chloroacetic acid, stir evenly, and obtain an apple pectin solution; (2) heating the apple pectin solution to 70° C., stirring continuously for 1 h, cooling, and centrifuging at 7000 r / min for 6 min. The obtained particles were washed with ethanol and dried at 80° C. to obtain carboxymethyl apple pectin for later use. (3) 1 kg of peanut protein was mixed with 14 L of water to prepare a solution, and the mixture was mixed to obtain a peanut protein solution; (4) Dissolve 1 kg of carboxymethyl apple pectin in water, add 0.67 L of peanut protein solution, stir evenly, add 20% activated yeast, and homogenize at 4000 r / min for 4 min to obtain yeast microsphere emulsion. Embedding rate determination: Table 1 Encapsulation efficiency of yeast cells in yeast microsphere emulsion Example 1 Example 2 Example 3 Example 4 Example 5 Comparative Example 1 Embedding rate (%) 88.06 88.14 89.12 88.63 88.45 85.74 As shown in Table 1, the embedding rate of yeast cells in the yeast microsphere emulsions prepared in Examples 1-5 is 88.06-89.12%, while the embedding rate of the yeast microsphere emulsion prepared by peanut protein in Comparative Example 1 is 85.74%. It can be seen that the embedding effect of peanut protein enzymatic hydrolysate is better than that of peanut protein. Therefore, the yeast microsphere emulsion prepared in Example 3 is selected for the subsequent preparation of frozen dough. Example 6 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 70 parts of flour, 0.5 parts of salt and 0.5 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 50 parts of water and 5 parts of yeast microsphere emulsion to the mixture, stir at low speed for 2 minutes, and then stir at high speed for 2 minutes to obtain a dough; S3. The dough was placed under 20% RH and 140°C conditions for wet heat treatment for 5 min, cut into small pieces of 60 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 min to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Example 7 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 72 parts of flour, 0.6 parts of salt and 0.5 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 50 parts of water and 5 parts of yeast microsphere emulsion to the mixture, stir at low speed for 2 min, then stir at high speed for 2 min to obtain a fresh dough; S3. The fresh dough was placed under 20% RH and 140°C conditions for wet heat treatment for 5 min, cut into small pieces of dough of 60 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 min to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Example 8 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 74 parts of flour, 0.7 parts of salt and 0.6 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 51 parts of water and 6 parts of yeast microsphere emulsion to the mixture, stir at low speed for 2 min, then stir at high speed for 3 min to obtain a fresh dough; S3. The fresh dough was placed under 20% RH and 140°C conditions for wet heat treatment for 6 min, cut into small pieces of dough of 70 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 min to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Example 9 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 76 parts of flour, 0.8 parts of salt and 0.6 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 52 parts of water and 6 parts of yeast microsphere emulsion to the mixture, stir at low speed for 2 min, then stir at high speed for 3 min to obtain a fresh dough; S3. The fresh dough was placed under 25% RH and 140°C conditions for wet heat treatment for 7 minutes, cut into small pieces of dough of 70 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Example 10 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 78 parts of flour, 0.9 parts of salt and 0.7 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 53 parts of water and 7 parts of yeast microsphere emulsion to the mixture, stir at low speed for 3 minutes, and then stir at high speed for 4 minutes to obtain a fresh dough; S3. The fresh dough was placed under 25% RH and 145°C conditions for wet heat treatment for 8 minutes, cut into small pieces of dough of 80 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Embodiment 11 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 80 parts of flour, 1 part of salt and 0.7 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 54 parts of water and 7 parts of yeast microsphere emulsion to the mixture, stir at low speed for 3 minutes, and then stir at high speed for 4 minutes to obtain a fresh dough; S3. The fresh dough was placed under 25% RH and 145°C conditions for wet heat treatment for 9 minutes, cut into small pieces of dough of 80 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Example 12 A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 80 parts of flour, 1 part of salt and 0.8 parts of trehalose were weighed and mixed to obtain a mixture; S2. Add 55 parts of water and 8 parts of yeast microsphere emulsion to the mixture, stir at low speed for 3 minutes, and then stir at high speed for 4 minutes to obtain a fresh dough; S3. The fresh dough was placed in a wet heat treatment at 25% RH and 145°C for 10 min, cut into small pieces of dough of 80 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 min to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Comparative Example 2 The difference between this comparative example and Example 9 is that no yeast microsphere emulsion is prepared, and carboxymethyl apple pectin and yeast are directly added, as follows: S1. Disperse 2 kg of apple pectin in 22 L of 80% ethanol solution, add 18 L of 38% NaOH, then add 3.4 L of chloroacetic acid, stir well to obtain an apple pectin solution; S2. The apple pectin solution was heated to 70°C, stirred continuously for 1 hour, cooled, centrifuged at 7000 r / min for 6 minutes, the obtained particles were washed with ethanol, and dried at 80°C to obtain carboxymethyl apple pectin for later use; S3. According to the recipe, 76 parts of flour, 0.8 parts of salt, 0.6 parts of trehalose and 1kg of carboxymethyl apple pectin were weighed and mixed to obtain a mixture; S4. Add 52 parts of water and 20% activated yeast to the mixture, stir at low speed for 2 min, then stir at high speed for 3 min to obtain a fresh dough; S5. The fresh dough was placed under 25% RH and 140°C conditions for wet heat treatment for 7 minutes, cut into small pieces of dough of 70 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Comparative Example 3 The difference between this comparative example and Example 9 is that unmodified apple pectin is used, specifically as follows: S1. Prepare a solution of 1 kg peanut protein and 14 L water, mix well to obtain a mixed solution; S2. The mixed solution was heated at 80°C for 10 min and then cooled to 65°C, 0.7% papain was added for enzymatic hydrolysis for 8 h, the enzyme was inactivated by boiling for 10 min, and the mixture was centrifuged at 7000 r / min for 9 min. The supernatant was obtained to obtain the peanut enzymatic hydrolysate; S3. Dissolve 1 kg of apple pectin in water, add 0.67 L of peanut protein hydrolysate, stir evenly, add 20% activated yeast, homogenize at 4000 r / min for 4 min, and obtain yeast microsphere emulsion; S4. According to the formula, 76 parts of flour, 0.8 parts of salt and 0.6 parts of trehalose were weighed and mixed to obtain a mixture; S6. Add 52 parts of water and 6 parts of yeast microsphere emulsion to the mixture, stir at low speed for 2 min, then stir at high speed for 3 min to obtain a fresh dough; S6. The fresh dough was placed under 25% RH and 140°C conditions for heat-moisture treatment for 7 min, cut into small dough pieces of 70 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 min until the center temperature of the dough reached -18°C, and frozen to obtain frozen dough with high yeast activity. Comparative Example 4 The difference between this comparative example and Example 9 is that no wet heat treatment is used, which is as follows: A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 76 parts of flour, 0.8 parts of salt and 0.6 parts of trehalose were weighed and mixed to obtain a mixture; S2. 52 parts of water and 6 parts of the yeast microsphere emulsion prepared in Example 3 were added to the mixture, stirred at low speed for 2 min, and then stirred at high speed for 3 min to obtain a fresh dough; S3. Cut the fresh dough into small pieces of dough of 70 g, put them into plastic wrap, seal them, and quickly freeze them in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C. Frozen storage can obtain frozen dough with high yeast activity. Comparative Example 5 The difference between this comparative example and Example 9 is that the yeast emulsion microspheres prepared in Comparative Example 1 are as follows: A method for preparing frozen dough with high yeast activity comprises the following steps: S1. According to the formula, 76 parts of flour, 0.8 parts of salt and 0.6 parts of trehalose were weighed and mixed to obtain a mixture; S2. 52 parts of water and 6 parts of the yeast microsphere emulsion prepared in Comparative Example 1 were added to the mixture, stirred at low speed for 2 min, and then stirred at high speed for 3 min to obtain a fresh dough; S3. The fresh dough was placed under 25% RH and 140°C conditions for wet heat treatment for 7 minutes, cut into small pieces of dough of 70 g, put into plastic wrap, sealed, and quickly frozen in a -40°C refrigerator for 90 minutes to make the center temperature of the dough reach -18°C, and frozen to obtain frozen dough with high yeast activity. Performance Test: (1) Determination of yeast survival rate The frozen doughs prepared in Example 9 and Comparative Examples 2-5 were frozen and stored for 1 week for later use. Determine the yeast count of fresh dough (calculated per gram of dough): First, cut 5g of fresh dough from two different parts, the surface and the inner core, with clean scissors or a knife, and place it in 45mL of sterile saline and shake it for about 3 minutes to extract the yeast; Determine the number of yeast in frozen dough (calculated per gram of dough): Thaw the frozen dough in a 4°C refrigerator until the dough softens, then cut 5 g from two different parts, the surface and the inner core, and place it in 45 mL of sterile saline and shake it for about 3 minutes to extract the yeast. Use a 1 mL pipette to take the supernatant of the fresh dough and frozen dough after shaking, and then 5 After multiple dilution and mixing, obtain the dilution solution. Take 1 mL of the dilution solution and add it to the Bengal red agar medium for coating. After coating, turn the culture dish upside down and place it in a 37°C incubator. After 48 hours of incubation, take it out and count the colonies on the plate. Count two plates for each of the surface dough and the inner dough. Repeat the experiment 3 times and take the average value of the results. The formula for calculating the yeast survival rate after freezing is: P=A / A0×100% Wherein, P is the survival rate of yeast after freezing, %; A is the number of yeast colonies in frozen dough, lgCFU / g; A0 is the number of yeast colonies in fresh dough, lgCFU / g. Depend on Figure 1 It can be seen that after one week of frozen storage, the survival rate of yeast on the surface of the frozen dough prepared in Example 9 reached 98%, and the survival rate of yeast in the core was 95%; in Comparative Example 2, the yeast microsphere emulsion was not prepared, and the carboxymethyl apple pectin and yeast were directly added to prepare the frozen dough, the survival rate of yeast on the surface was 75%, and the survival rate of yeast in the core was 71%, and the survival rate decreased significantly. It can be seen that the emulsion prepared by carboxymethyl apple pectin and peanut protein hydrolysate in the present invention is beneficial to protect yeast cells from ice crystal damage, reduce yeast mortality, and prepare frozen dough with high yeast activity; Comparative Example 3 adopts The frozen dough prepared with unmodified apple pectin can only bind a limited amount of water, resulting in more free water in the system. After freezing, more ice crystals are easily formed, which damages the gluten network structure and yeast cells to a certain extent, and reduces the survival rate of yeast. The frozen dough in Comparative Example 4, which is not prepared by wet heat treatment, does not have the better strength and stability of the gluten network as in the embodiments, and has a relatively small effect on the survival rate of yeast. Comparative Example 5 uses the yeast microsphere emulsion prepared in Comparative Example 1, which has relatively poor encapsulation of yeast cells, and frozen storage is more likely to damage yeast cells, reducing the survival rate of yeast. At the same time, it can be seen that the survival rate of yeast on the surface of frozen dough is higher than that of yeast in the inner core. This may be because the frozen moisture in the dough can migrate during the freezing process, and the moisture content on the surface of the dough is less than that in the inner core. Therefore, the ice crystals formed on the surface are less than those in the inner core, and thus the ice crystals are relatively less harmful to the yeast on the surface of the dough. (2) Determination of yeast fermentation capacity The yeast fermentation capacity was determined by the drainage method, referring to the method used by Zhou Honglu et al. in studying the fermentation characteristics of different yeasts on frozen dough, and the calculation was performed according to the following formula: Fermentation power F = V2-V1 Among them, F is the fermentation capacity, mL; V2 is the sum of the displacement in 3 hours, mL; V1 is the sum of the displacement in the first hour, mL. Table 2 Fermentation capacity of frozen dough yeast prepared in each embodiment and comparative example Fermentation capacity (mL) Fermentation capacity (mL) Example 6 810 Example 12 813 Example 7 812 Comparative Example 2 756 Example 8 815 Comparative Example 3 775 Example 9 820 Comparative Example 4 788 Example 10 818 Comparative Example 5 780 Embodiment 11 809 As can be seen from Table 2, the fermentation power of the frozen dough prepared in Examples 6-12 is 809-820 mL. In Comparative Example 2, the yeast microsphere emulsion was not prepared, and the carboxymethyl apple pectin and yeast were directly added to the frozen dough, and the fermentation power was 756 mL. Because the peanut protein hydrolysate was not added, the enzymatic hydrolysate has the effect of promoting yeast growth and improving yeast fermentation performance; Comparative Example 3 uses unmodified apple pectin to prepare frozen dough, and the fermentation power is 775 mL. This is because the increase in ice crystals destroys the gluten yeast structure, which reduces the dough fermentation power; and Comparative Example 4 does not use wet heat treatment to prepare frozen dough, and the effect on the fermentation power is relatively small; Comparative Example 5 uses the yeast microsphere emulsion prepared in Comparative Example 1. The frozen dough is prepared, and the embedding effect of yeast cells is relatively poor, which will also weaken the yeast fermentation power to a certain extent. (3) Dough stretching properties The FTC texture analyzer was used for the measurement, and the test parameters were as follows: force sensor range 250N; starting force 0.1N; test speed 1mm / s; test distance 60mm, and the maximum tensile resistance of the dough was measured. Table 3 Maximum tensile resistance of frozen dough prepared in each embodiment and comparative example Maximum tensile resistance (N) Maximum tensile resistance (N) Example 6 1.38 Example 12 1.36 Example 7 1.35 Comparative Example 2 1.26 Example 8 1.34 Comparative Example 3 1.21 Example 9 1.44 Comparative Example 4 1.22 Example 10 1.37 Comparative Example 5 1.29 Embodiment 11 1.33 The maximum tensile resistance is an important indicator for evaluating the elasticity and gluten strength of dough. The higher the resistance, the stronger the gluten strength and the better the elasticity. As can be seen from Table 3, the maximum tensile resistance of the frozen dough prepared in Examples 6-12 is 1.33-1.44N, the maximum tensile resistance of Comparative Example 2 is 1.26N, and the maximum tensile resistance of the frozen dough prepared in Comparative Examples 3 and 4 is similar, which is 1.21 and 1.22N. It can be seen that after the carboxymethyl modified apple pectin, more water in the system can be combined to reduce the generation of ice crystals, thereby reducing the damage of ice crystals to the gluten network structure. Appropriate wet heat treatment can also enhance the strength and stability of the gluten network and protect the structure of the dough during the freezing process. The above is only a preferred embodiment of the present invention and does not limit the present invention in any form. Any technician familiar with the art can make many possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and technical solution of the present invention, or modify it into an equivalent embodiment of equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention still falls within the scope of protection of the technical solution of the present invention.

Claims

1. A frozen dough with high yeast activity, characterized in that: Includes the following components: 70-80 parts of flour, 50-55 parts of water, 0.5-1 parts of salt, 5-8 parts of yeast microsphere emulsion and 0.5-0.8 parts of trehalose.

2. The frozen dough with high yeast activity according to claim 1, characterized in that: The yeast microsphere emulsion is prepared by coating yeast cells with an emulsion prepared from carboxymethyl apple pectin and peanut protein hydrolysate.

3. A frozen dough with high yeast activity according to claim 2, characterized in that: The preparation steps of the yeast microsphere emulsion are: (1) dispersing apple pectin in 80% ethanol solution, adding 38% NaOH, and then adding 8.5% chloroacetic acid, stirring evenly to obtain an apple pectin solution; (2) heating the apple pectin solution to 60-80° C., stirring continuously for 1 hour, cooling, centrifuging at 6000-8000 r / min for 5-8 minutes, washing the obtained particles with ethanol, and drying at 80° C. to obtain carboxymethyl apple pectin for later use; (3) preparing a solution with peanut protein and water in a ratio of 1:(13-15), and mixing the mixture to obtain a mixed solution; (4) heating the mixed solution at 80° C. for 10 min, cooling it to 60-65° C., adding papain for enzymolysis for 6-9 h, boiling it for 10 min to inactivate the enzyme, centrifuging it at 6000-8000 r / min for 8-10 min, and taking the supernatant to obtain a peanut protein hydrolysate; (5) Dissolve carboxymethyl apple pectin in water, add peanut protein hydrolysate, stir evenly, add activated yeast, and homogenize to obtain yeast microsphere emulsion.

4. The frozen dough with high yeast activity according to claim 3, characterized in that: In the step (1), the mass volume ratio of apple pectin to ethanol solution is 1:(10-11); the mass volume ratio of apple pectin to NaOH is 1:(8-10).

5. The frozen dough with high yeast activity according to claim 3, characterized in that: The amount of papain added in step (4) is 0.5-0.8%.

6. The frozen dough with high yeast activity according to claim 3, characterized in that: In the step (5), the mass volume ratio of carboxymethyl apple pectin to peanut protein hydrolysate is (1-2):1; and the amount of activated yeast added is 10-30%.

7. The frozen dough with high yeast activity according to claim 3, characterized in that: In the step (5), the homogenization speed is 3000-5000 r / min, and the homogenization time is 3-6 min.

8. The method for preparing frozen dough with high yeast activity according to any one of claims 1 to 7, characterized in that: The following steps are involved: S1. Weigh flour, salt and trehalose according to the recipe and mix them evenly to obtain a mixture; S2. Add water and yeast microsphere emulsion to the mixture, stir at low speed for 2-3 minutes, and then stir at high speed for 2-4 minutes to obtain a fresh dough; S3. The fresh dough is placed under 20-25% RH and 140-145° C. for wet heat treatment for 5-10 min, cut into small pieces of dough of 60-80 g, put into plastic wrap, seal, and quickly freeze in a -40° C. refrigerator for 90 min until the center temperature of the dough reaches -18° C., and frozen to obtain frozen dough with high yeast activity.

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