Pre-fermented pizza dough and method for preparing the same

Abstract

The application discloses a pre-fermentation pizza dough embryo and a preparation method thereof. The pre-fermentation pizza dough embryo is prepared from the following raw materials in parts by weight: 51.12-54.03 parts by weight of wheat flour, 1.02-2.05 parts by weight of milk powder, 0.83-1.34 parts by weight of salt, 4.81-5.53 parts by weight of whole egg liquid, 2.82-3.61 parts by weight of fresh yeast, 2.82-3.31 parts by weight of butter, 5.05-5.52 parts by weight of white granulated sugar, 25.13-27.24 parts by weight of water, 1.06-1.57 parts by weight of leavening agent and 0.16-0.20 parts by weight of compound enzyme preparation. The pre-fermentation pizza dough embryo has high water-retention capacity during freezing and baking, and the pizza crust can be thickened by more than 20% after baking. The preparation method of the pre-fermentation pizza dough embryo greatly improves the work efficiency of a store.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of food processing, in particular to a pre-fermentation pizza frozen embryo and a preparation method thereof. BACKGROUND

[0002] Pizza is a famous Italian food, originated in Naples, Italy, and is popular all over the world. It has become a global food, but people in different countries and regions have slightly different tastes when eating this pie. Traditional food industrialization is the development trend of food industry at home and abroad.

[0003] However, the traditional pizza pie processing process is complicated, the manual operation is arbitrary, the process is difficult to control, and the taste of the pizza pie produced is quite different. Usually, food additives are added to solve these problems. Alum is a kind of aluminum compound, which has been used as the main component of leavening agent in the food industry for a long time. However, experiments have proved that frequent consumption of food with excessive aluminum can cause problems such as senile dementia, loss of motor coordination, memory loss, and impact on children's intelligence development. Subsequently, other leavening agents are used instead when making pizza, but many kinds of leavening agents need to be mixed to achieve the effect of fluffiness, which is not convenient to operate.

[0004] In addition, the traditional frozen pizza dough needs to be thawed and proofed for several hours after being sent to the store, which is time-consuming and labor-intensive. The pre-fermented frozen pizza dough on the market also needs to be thawed for a period of time before baking.

[0005] Therefore, it is necessary to provide a pizza that is convenient to make. SUMMARY

[0006] The present application aims to solve at least one of the problems in the prior art, and thus, in a first aspect of the present application, the present application provides a pre-fermentation pizza frozen embryo, which is prepared from the following raw materials by weight: 51.12-54.03 parts by weight of wheat flour, 1.02-2.05 parts by weight of milk powder, 0.83-1.34 parts by weight of salt, 4.81-5.53 parts by weight of whole egg liquid, 2.82-3.61 parts by weight of fresh yeast, 2.82-3.31 parts by weight of butter, 5.05-5.52 parts by weight of white sugar, 25.13-27.24 parts by weight of water, 1.06-1.57 parts by weight of leavening agent, and 0.16-0.20 parts by weight of compound enzyme preparation.

[0007] The leavening agent is composed of gluconic acid-delta-lactone and NaHCO3 in a mass ratio of (1.34-3.54):1.

[0008] The compound enzyme preparation is composed of xylanase, glucose oxidase, and maltogenic amylase in a mass ratio of (2-5):(1-2):1.

[0009] By the above technical solution, the moisture content reduction rate of the pre-fermented pizza is within 35%, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is within 60%, the elasticity reduction rate is within 15%, and the thickness increase rate of the baked pizza is more than 20%.

[0010] Preferably, the raw materials for preparing the pre-fermented pizza embryo further comprise an additive, and the additive comprises at least one of vitamin C and resistant dextrin.

[0011] By the above technical solution, when vitamin C or resistant dextrin is added to the pre-fermented pizza embryo, the moisture content reduction rate of the pre-fermented pizza after being frozen is smaller, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is smaller, and the elasticity change rate is smaller, which may be because vitamin C and resistant dextrin can improve the water retention performance of the raw materials and improve the affinity between the raw materials.

[0012] Preferably, the additive comprises 0.08-0.12 parts by weight of vitamin C and 0.01-0.04 parts by weight of resistant dextrin.

[0013] Preferably, the additive comprises 0.1 part by weight of vitamin C and 0.03 part by weight of resistant dextrin.

[0014] By the above technical solution, the inventors have unexpectedly found that vitamin C and resistant dextrin have obvious synergistic effect on improving the moisture content reduction rate of the pre-fermented pizza embryo after being frozen, the hardness change rate after being stored for 2 days, and the elasticity change rate. When vitamin C and resistant dextrin are added at the same time, the moisture content reduction rate of the pre-fermented pizza can be controlled within 25%, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is within 35%, and the elasticity reduction rate is within 8%.

[0015] Preferably, the additive further comprises 1-1.5 parts by weight of protein powder. Preferably, the protein powder is 1.2 parts by weight.

[0016] By the above technical solution, the moisture content reduction rate of the pre-fermented pizza can be controlled within 20%, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is within 25%, and the elasticity reduction rate is within 5%. This may be because the protein powder can play a lubricating role between the raw materials.

[0017] In the second aspect of the present application, the present application provides a method for preparing the pre-fermented pizza embryo in the first aspect of the present application, comprising the following steps:

[0018] Step 1): Mix the raw materials and stir them uniformly;

[0019] Step 2): Forming, rolling into a pizza crust;

[0020] Step 3): proofing;

[0021] Step 4): quick freezing, to obtain the pre-fermented pizza frozen dough.

[0022] Preferably, in the step 1), the surface temperature is controlled to be 18-20℃.

[0023] Preferably, the step 1) comprises:

[0024] Step 1-1): dissolve the xylanase and glucose oxidase in water, and stir to dissolve;

[0025] Step 1-2): add other substances and stir to mix evenly.

[0026] Through the above technical solution, the thickness rate of the baked pizza is improved.

[0027] Preferably, in the step 3), the proofing is carried out at a temperature of 30-40℃ and a humidity of 75-90%, and the height of the pizza cake is 1-2cm after proofing.

[0028] Preferably, in the step 4), the quick freezing is carried out at-30--40℃ for 20-40min.

[0029] Through the above technical solution, the moisture content decrease rate of the pre-fermented pizza frozen dough after freezing is small, and the hardness change rate and the elasticity change rate of the pre-fermented pizza after storage at 5℃ for 2 days are small. This may be because different freezing temperatures will affect the texture of the pizza and the performance of the leavening agent and additives, and therefore, a suitable freezing temperature needs to be adopted.

[0030] Preferably, the step 1-2) further comprises:

[0031] 1-2-1) stir the wheat flour, milk powder, salt, vitamin C, resistant dextrin, whole egg liquid and water to mix evenly, and place for 1-2h; 1-2-2) add fresh yeast, butter, white granulated sugar, leavening agent, malt sugar amylase and egg white powder, and stir to mix evenly. In a third aspect, the present application provides a preparation method of pre-fermented pizza, comprising the following steps: adding ingredients on the pre-fermented pizza frozen dough prepared by the preparation method of the second aspect of the present application, and baking, to obtain the pre-fermented pizza.

[0032] Preferably, the baking is carried out at 170-180℃ in a gas oven for 10-12min, and at 160-200℃ in a flat oven for 14-18min.

[0033] Preferably, the baking temperature in the gas oven is 175-180℃.

[0034] The present application has the following beneficial effects:

[0035] 1. The pre-fermented pizza dough ball has strong water retention capacity during freezing and baking, and the water content of the pre-fermented pizza dough ball after freezing decreases by less than 35%, and the pizza crust can be thickened by more than 20% after baking; 2. The pre-fermented pizza dough ball preparation method is easy to operate, and the standard fermentation is intensive in the factory, and the pre-fermented pizza dough ball is formed in the factory, and after the pre-fermented pizza dough ball frozen in the factory is transported to the store, it does not need to be thawed and leavened, and is directly baked and formed, which greatly improves the work efficiency of the store and reduces the production cost; 3. The pre-fermented pizza is prepared by adding ingredients and food materials on the pre-fermented pizza dough ball, and the pre-fermented pizza prepared by the preparation method has good anti-aging performance, and the hardness improvement rate is less than 60% and the elasticity decrease rate is less than 15% after two days of storage. DETAILED DESCRIPTION

[0036] The application will be further described below in conjunction with specific examples. However, the following examples are only used to illustrate the application, and should not be regarded as limiting the scope of the application. In the following examples, the specific conditions are not specified, and the conventional conditions or the conditions recommended by the manufacturer are used. The methods used are conventional methods known in the art unless otherwise specified. The consumables and reagents used are commercially available unless otherwise specified. Unless otherwise specified, the professional and scientific terms used in this text have the same meaning as those familiar to persons skilled in the art. In addition, any method or material similar or equivalent to the described content can also be applied in the application. Whole egg liquid is obtained by breaking the shell of a raw egg and stirring uniformly. Milk powder is a commercially available Nestle whole family nutrition milk powder. Resistant dextrin is food-grade resistant dextrin purchased from Shaanxi Chenming Biological Technology Co., Ltd.

[0037] Example 1

[0038] The pre-fermented pizza dough ball is prepared from the following raw materials by weight:

[0039] Wheat flour 52.77 kg; milk powder 1.58 kg; salt 0.95 kg; whole egg liquid 5.28 kg; fresh yeast 3.17 kg; butter 3.17 kg; white sugar 5.28 kg; water 26.39 kg; leavening agent 1.26 kg; compound enzyme preparation 0.18 kg.

[0040] The leavening agent is composed of 0.84 kg of glucono-delta-lactone and 0.42 kg of NaHCO3.

[0041] The compound enzyme preparation is composed of 0.10 kg of xylanase, 0.05 kg of glucose oxidase, and 0.03 kg of maltogenic amylase.

[0042] The embodiment provides a preparation method of pre-fermented pizza, and comprises the following steps:

[0043] Step 1): the raw materials are mixed, stirred uniformly, and the surface temperature is controlled to be 18-20 DEG C;

[0044] Step 2): shaping, rolling into a pizza shape;

[0045] Step 3): fermentation at a temperature of 38 DEG C and a humidity of 85 DEG C to a height of 1.5 cm;

[0046] Step 4): quick freezing at-35 DEG C for 30 min, and pre-fermented pizza dough is obtained; the pre-fermented pizza dough can be stored in a frozen state at-18 DEG C;

[0047] Step 5): the frozen pre-fermented pizza dough is directly placed in a tray, and ingredients (beef, tomato, corn) are added on the pre-fermented pizza dough; the pizza is baked in a wind furnace at 178 DEG C for 11 min and baked in a flat furnace at 180 DEG C for 16 min, and pre-fermented pizza is obtained.

[0048] Embodiment 2

[0049] The embodiment provides a pre-fermented pizza dough, which is prepared from the following raw materials in the following proportions:

[0050] 51.12 kg of wheat flour, 2.05 kg of milk powder, 1.34 kg of salt, 4.81 kg of whole egg liquid, 2.82 kg of fresh yeast, 3.31 kg of butter, 5.05 kg of white sugar, 27.24 kg of water, 1.06 kg of leavening agent and 0.16 kg of compound enzyme preparation.

[0051] The leavening agent is composed of 0.99 kg of glucono-delta-lactone and 0.28 kg of NaHCO3.

[0052] The compound enzyme preparation is composed of 0.10 kg of xylanase, 0.04 kg of glucose oxidase and 0.02 kg of maltogenic amylase.

[0053] The embodiment provides a preparation method of pre-fermented pizza, and comprises the following steps:

[0054] Step 1): the raw materials are mixed, stirred uniformly, and the surface temperature is controlled to be 18-20 DEG C;

[0055] Step 2): shaping, rolling into a pizza shape;

[0056] Step 3): fermentation at a temperature of 30 DEG C and a humidity of 75 DEG C to a height of 1.5 cm;

[0057] Step 4): quick freezing at-30 DEG C for 40 min, and pre-fermented pizza dough is obtained; the pre-fermented pizza dough can be stored in a frozen state at-18 DEG C;

[0058] Step 5): The frozen pre-fermented pizza dough is directly placed in a tray, and ingredient materials (beef, tomato, corn) are added thereon, and then baked in a convection oven at 175℃ for 10 min and in a flat oven at 200℃ for 14 min to obtain a pre-fermented pizza.

[0059] Example 3

[0060] The present example provides a pre-fermented pizza dough, which is prepared from the following raw materials by weight:

[0061] 54.03 kg of wheat flour, 1.02 kg of milk powder, 0.83 kg of salt, 5.53 kg of whole egg liquid, 3.61 kg of fresh yeast, 2.82 kg of butter, 5.52 kg of white sugar, 25.13 kg of water, 1.57 kg of leavening agent, and 0.20 kg of compound enzyme preparation.

[0062] The leavening agent is composed of 0.78 kg of glucono-delta-lactone and 0.58 kg of NaHCO3.

[0063] The compound enzyme preparation is composed of 0.10 kg of xylanase, 0.05 kg of glucose oxidase, and 0.05 kg of maltogenic amylase.

[0064] The present example provides a method for preparing a pre-fermented pizza, which comprises the following steps:

[0065] Step 1): Mix the raw materials and stir them uniformly, and control the surface temperature to be 18-20℃;

[0066] Step 2): Shape into a pizza shape;

[0067] Step 3): Let it rise at a temperature of 40℃ and a humidity of 90° until the height is 1.5 cm;

[0068] Step 4): Freeze at -40℃ for 20 min to obtain a pre-fermented pizza dough; the pre-fermented pizza dough can be stored in a frozen state at -18℃;

[0069] Step 5): Place the frozen pre-fermented pizza dough in a tray, add ingredient materials (beef, tomato, corn) thereon, and then bake in a convection oven at 180℃ for 12 min and in a flat oven at 160℃ for 18 min to obtain a pre-fermented pizza.

[0070] Example 4

[0071] The difference between Example 4 and Example 1 is that in Step 1), the order of adding the raw materials is as follows:

[0072] Step 1-1): Dissolve xylanase and glucose oxidase in water and stir to dissolve;

[0073] Step 1-2): Put other substances, stir evenly, control the surface temperature at 18-20℃.

[0074] Example 5

[0075] Example 5 differs from Example 4 in that the raw materials for preparing the pre-fermented pizza dough also include 0.1 kg of vitamin C.

[0076] Example 6

[0077] Example 6 differs from Example 4 in that the raw materials for preparing the pre-fermented pizza dough also include 0.03 kg of resistant dextrin.

[0078] Example 7

[0079] Example 7 differs from Example 4 in that the raw materials for preparing the pre-fermented pizza dough also include 0.1 kg of vitamin C and 0.03 kg of resistant dextrin.

[0080] Example 8

[0081] Example 8 differs from Example 7 in that the raw materials for preparing the pre-fermented pizza dough also include 1.2 kg of egg powder. The egg powder is obtained by cooking eggs with shells, removing the shells, removing the egg yolks, and crushing them into a paste.

[0082] Example 9

[0083] Example 9 differs from Example 8 in that step 1-2) further includes:

[0084] 1-2-1) Stir the wheat flour, milk powder, salt, vitamin C, resistant dextrin, whole egg liquid, and water evenly and place for 1-2 h; 1-2-2) Add fresh yeast, butter, white sugar, leavening agent, malt sugar amylase, and egg powder and stir evenly.

[0085] Example 10

[0086] Example 10 differs from Example 8 in that it is baked in a wind furnace at 170℃ for 11 min and in a flat furnace at 180℃ for 16 min.

[0087] Example 11

[0088] Example 11 differs from Example 8 in that it is baked in a wind furnace at 175℃ for 11 min and then in a wind furnace at 180℃ for 16 min.

[0089] Comparative Example 1

[0090] The difference between Comparative Example 1 and Example 1 is that the bulking agent is composed of 1.008 kg of glucono-delta-lactone and 0.252 kg of NaHCO3.

[0091] Comparative Example 2

[0092] The difference between Comparative Example 2 and Example 1 is that the complex enzyme preparation is composed of 0.12 kg of xylanase, 0.04 kg of glucose oxidase, and 0.02 kg of maltogenic amylase.

[0093] Comparative Example 3

[0094] The difference between Comparative Example 3 and Example 1 is that in the complex enzyme preparation, the maltogenic amylase is replaced by alpha amylase.

[0095] The moisture content reduction rate and the texture of the pre-fermented pizza prepared in the above examples and comparative examples are measured, and the method and results are as follows:

[0096] 1. Measurement of the moisture content reduction rate of the pre-fermented pizza

[0097] The moisture content of the pre-fermented pizza dough prepared in step 4) of the examples and comparative examples is measured according to the method of GB5009.3, and the result is A1. The pre-fermented pizza dough prepared in step 4) of the examples and comparative examples is stored at -18°C for 30 days, and then the moisture content is measured according to the method of GB5009.3, and the result is A2. The moisture content reduction rate x of the pre-fermented pizza dough is calculated, x = |A2-A1| / A1, and the results of the moisture content reduction rate of the pre-fermented pizza dough are shown in Table 1.

[0098] 2. Measurement of the hardness and elasticity of the pre-fermented pizza

[0099] The hardness and elasticity of the fresh pre-fermented pizza and the pre-fermented pizza stored at 5°C for 2 days prepared in the examples and comparative examples are measured using a texture analyzer, and the hardness and elasticity change rates are calculated, and the results are shown in Table 1.

[0100] 3. The thickness h1 of the pre-fermented pizza dough before baking and the thickness h2 of the pizza crust prepared after baking are measured using a caliper, and the pizza crust thickening rate z is calculated, z = h2-h1 / h1, and the results of the pizza crust thickening rate are shown in Table 1.

[0101]

[0102]

[0103] Comparing Example 1-3 with Example 4, when the leavening agent is stirred and dissolved in water, and then other substances are added and stirred uniformly in step 1), the thickness increase rate of the baked pizza is improved.

[0104] Comparing Example 4 with Example 5, when vitamin C is added to the pre-fermented pizza dough, the moisture content decrease rate of the pre-fermented pizza after freezing is smaller, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is smaller, and the elasticity change rate is smaller.

[0105] Comparing Example 4 with Example 6, when resistant dextrin is added to the pre-fermented pizza dough, the moisture content decrease rate of the pre-fermented pizza after freezing is smaller, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is smaller, and the elasticity change rate is smaller.

[0106] Comparing Example 4 with Example 5-7, vitamin C and resistant dextrin have obvious synergistic effect on improving the moisture content decrease rate of the pre-fermented pizza after freezing, the hardness change rate after being stored at 5℃ for 2 days, and the elasticity change rate.

[0107] Comparing Example 7 with Example 8, when protein powder is added to the pre-fermented pizza dough, the moisture content decrease rate of the pre-fermented pizza after freezing is smaller, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is smaller, and the elasticity change rate is smaller.

[0108] Comparing Example 8 with Example 9, when wheat flour, milk powder, salt, vitamin C, resistant dextrin, whole egg liquid, and water are stirred and uniformly placed for 1-2h, and then other substances are added, the moisture content decrease rate of the pre-fermented pizza after freezing is smaller, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is smaller, the elasticity change rate is smaller, and the thickness increase rate of the baked pizza is improved.

[0109] Comparing Example 8 with Example 10 and 11, when the baking temperature in the oven is changed, or the baking method is changed from oven baking to separate oven baking or separate oven baking, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is larger, the elasticity change rate is larger, and the thickness increase rate of the baked pizza is reduced.

[0110] Comparing Example 1 with Comparative Example 1, when the mass ratio of glucono-delta-lactone to NaHCO3 in the leavening agent is outside the range of (1.34-3.54):1, the moisture content decrease rate of the pre-fermented pizza is above 35%, the hardness change rate of the pre-fermented pizza after being stored at 5℃ for 2 days is above 70%, the elasticity change rate is above 20%, and the thickness increase rate of the baked pizza is below 20%.

[0111] As can be seen from the comparison between Example 1 and Comparative Example 2, when the mass ratio of xylanase, glucose oxidase and maltogenic amylase in the complex enzyme preparation is not within the range of (2-5):(1-2):1, the moisture content reduction rate of the pre-fermented pizza is more than 35%, the hardness change rate of the pre-fermented pizza after being stored at 5°C for 2 days is more than 70%, the elasticity change rate is more than 20%, and the pizza thickening rate after baking is less than 20%.

[0112] As can be seen from the comparison between Example 1 and Comparative Example 3, when the type of enzyme preparation in the complex enzyme preparation is changed, the moisture content reduction rate of the pre-fermented pizza is more than 35%, the hardness change rate of the pre-fermented pizza after being stored at 5°C for 2 days is more than 70%, the elasticity change rate is more than 20%, and the pizza thickening rate after baking is less than 20%.

[0113] The above are preferred embodiments of the present application, and are not intended to limit the protection scope of the present application, and thus: any equivalent changes made according to the structure, shape and principle of the present application should be covered within the protection scope of the present application.

Claims

1. A pre-fermented pizza dough, characterized in that: The pre-fermented pizza frozen dough is prepared from the following raw materials in parts by weight: 51.12-54.03 parts by weight of wheat flour, 1.02-2.05 parts by weight of milk powder, 0.83-1.34 parts by weight of salt, 4.81-5.53 parts by weight of whole egg liquid, 2.82-3.61 parts by weight of fresh yeast, 2.82-3.31 parts by weight of butter, 5.05-5.52 parts by weight of white sugar, 25.13-27.24 parts by weight of water, 1.06-1.57 parts by weight of a leavening agent, 0.16-0.20 parts by weight of a composite enzyme preparation, 0.08-0.12 parts by weight of vitamin C, and 0.01-0.04 parts by weight of resistant dextrin; Wherein, the leavening agent is composed of glucono-δ-lactone and NaHCO3 in a mass ratio of (1.34-3.54):1; The compound enzyme preparation consists of xylanase, glucose oxidase and maltogenic amylase in a mass ratio of (2-5): (1-2):

1.

2. A pre-fermented pizza dough, characterized in that: The pre-fermented pizza frozen dough is prepared from the following raw materials in parts by weight: 51.12-54.03 parts by weight of wheat flour, 1.02-2.05 parts by weight of milk powder, 0.83-1.34 parts by weight of salt, 4.81-5.53 parts by weight of whole egg liquid, 2.82-3.61 parts by weight of fresh yeast, 2.82-3.31 parts by weight of butter, 5.05-5.52 parts by weight of white sugar, 25.13-27.24 parts by weight of water, 1.06-1.57 parts by weight of a leavening agent, 0.16-0.20 parts by weight of a composite enzyme preparation, 0.08-0.12 parts by weight of vitamin C, 0.01-0.04 parts by weight of resistant dextrin, and 1-1.5 parts by weight of egg white powder; Wherein, the leavening agent is composed of glucono-δ-lactone and NaHCO3 in a mass ratio of (1.34-3.54):1; The compound enzyme preparation is composed of xylanase, glucose oxidase and maltogenic amylase in a mass ratio of (2-5): (1-2): 1; The egg white powder is obtained by boiling eggs in their shells, removing the shells and yolks, and crushing them into a paste.

3. A method for preparing a pre-fermented pizza frozen dough according to claim 2, characterized in that: The steps include: Step 1): Mix the raw materials and stir evenly; Step 2): Shape and roll into dough; Step 3): Proofing; Step 4): Quick freezing to obtain pre-fermented pizza frozen dough.

4. The method for preparing the pre-fermented pizza frozen embryo according to claim 3, wherein The step 1) includes: Step 1-1): Dissolve xylanase and glucose oxidase in water and stir to dissolve; Step 1-2): Add other substances and stir evenly.

5. The method for preparing the pre-fermented pizza frozen embryo according to claim 4, wherein The steps 1-2) further include: 1-2-1) Mix wheat flour, milk powder, salt, vitamin C, resistant dextrin, whole egg liquid and water and let it stand for 1-2 hours; 1-2-2) Add fresh yeast, butter, sugar, leavening agent, maltose amylase and egg white powder and mix well.

6. A method for preparing pre-fermented pizza, characterized in that: The method comprises the following steps: adding ingredients to the pre-fermented pizza frozen dough prepared by the preparation method according to any one of claims 3 to 5, and baking the pre-fermented pizza to obtain the pre-fermented pizza.

7. The method for preparing pre-fermented pizza according to claim 6, characterized in that: The baking is carried out in a blast furnace at 170-180°C for 10-12 min, or in an open hearth furnace at 160-200°C for 14-18 min.

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