Pre-baked frozen toast and preparation method thereof

Abstract

The invention discloses pre-baked frozen toast and a preparation method thereof, and belongs to the technical field of frozen food. The pre-baked frozen toast disclosed by the invention comprises the following raw materials in parts by mass: 100-110 parts of wheat flour, 60-65 parts of water, 10-15 parts of white granulated sugar, 2-4 parts of table salt, 1.6 parts of dried yeast and 0.3-0.5 part of an anti-freezing agent, the anti-freezing agent is propylene glycol alginate; and the protein content of the wheat flour is more than 12%. The toast prepared by unfreezing and re-baking the pre-baked frozen toast has good sense, the specific capacity of the toast is reduced to a limited extent, the quality of the product after re-baking is ensured, and the cost of the toast baked on site is reduced at the same time.

Description

Technical Field

[0001] This invention relates to the field of frozen food technology, and in particular to a pre-baked frozen toast and its preparation method. Background Technology

[0002] In 2023, the retail market size of baked goods in my country reached 561.42 billion yuan, a year-on-year increase of 9.2%. It is projected to reach 859.56 billion yuan by 2029, demonstrating the enormous potential of the baking industry. Frozen dough is one of the main products used in the industrialized production of staple foods from flour-based foods.

[0003] However, frozen pasta products suffer from problems such as decreased taste and freshness, and unstable product quality during storage and transportation, which seriously restricts market sales and product development. Bread obtained through pre-baking and freezing methods closely resembles the texture of fully baked fresh bread. However, because pre-baked frozen bread requires prolonged refrigeration and subsequent thawing and two baking processes, it exhibits problems such as reduced specific volume and increased staleness compared to fresh bread. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a pre-baked frozen toast and its preparation method. This invention achieves a new pre-baked frozen toast through improvements to raw materials. The resulting pre-baked frozen toast, after thawing and rebaking, produces toast with excellent sensory qualities. The specific volume of the toast decreases only slightly, ensuring the quality of the product after rebaking, while simultaneously reducing the cost of freshly baked toast.

[0005] The technical solution of the present invention is as follows: The first aspect of this invention protects a pre-baked frozen toast, comprising the following ingredients by weight: 100-110 parts wheat flour, 60-65 parts water, 10-15 parts white sugar, 2-4 parts salt, 1.6 parts dry yeast, and 0.3-0.5 parts antifreeze agent. The antifreeze agent is propylene glycol alginate; The protein content of the wheat flour is >12%.

[0006] Preferably, the wheat flour is high-gluten flour.

[0007] Preferably, the wheat flour is purchased from Yihai Kerry Group.

[0008] Preferably, the degree of esterification of the propylene glycol alginate is 75-95%.

[0009] Preferably, the propylene glycol alginate is obtained by mixing alginic acid, propylene oxide, and alkali, reacting to obtain a slurry, adjusting the pH, centrifuging, drying the resulting precipitate, and pulverizing it.

[0010] Preferably, the mass ratio of the alginic acid to the propylene oxide is 1:0.6~1; The mass of the alkali is 0.5 to 2% of the mass of the alginic acid.

[0011] Preferably, the reaction temperature is 50~70℃, the pressure is 0.2~0.3MPa, and the time is 1~3h; The pH adjustment refers to adjusting the pH to 3-4.

[0012] A second aspect of this invention protects a method for preparing the pre-baked frozen toast described in the second aspect above, comprising the following steps: S1: Mix the wheat flour, white sugar, salt, and antifreeze in the specified amounts to obtain a premix; S2: Add 1-10 parts water to the dry yeast of the recipe amount and mix to obtain yeast water; S3: Add the yeast water and the remaining water to the premix from step S1 and stir until a dough is formed; S4: After letting the dough from step S3 rest, degas, cut, and shape, it is proofed, baked, and frozen to obtain pre-baked frozen toast.

[0013] Preferably, in steps S1 and S3, the stirring time is 22-27 minutes.

[0014] Preferably, in step S4, the settling temperature is 2~4℃ and the settling time is 11~13min; The proofing temperature is 35~37℃, and the time is 50~60min; The baking process uses both top and bottom heat, with the top heat temperature at 190~210℃ and the bottom heat temperature at 180~190℃, and the baking time at 10~13 minutes. The freezing temperature is -24 to -18°C, and the freezing time is 2 to 7 days.

[0015] The beneficial technical effects of this invention are as follows: This invention optimizes the raw material composition by introducing propylene glycol alginate (PGA) and high-gluten flour in a synergistic effect, thereby improving the freezing stability of pre-baked frozen toast, reducing its hardness, and resulting in a texture close to fresh bread after thawing and rebaking, while also reducing its staleness. The molecular structure of propylene glycol alginate retains unesterified carboxylic acid groups (hydrophilic) and introduced propylene glycol groups (hydrophobic). This unique chemical composition endows propylene glycol alginate with excellent emulsifying, thickening, and stabilizing properties, enhancing the taste and texture of frozen dough products. Simultaneously, it restricts water migration, reducing the formation of large ice crystals from internal free water that pierce the gluten network and pore structure, thus minimizing the damage to storage quality caused by ice crystals. Furthermore, high-gluten flour with high protein content not only facilitates the formation of a strong and elastic gluten network, allowing for better carbon dioxide retention during fermentation and improving the fluffiness of baked toast, but also allows propylene glycol alginate to promote the binding of protein molecules in high-gluten flour, forming a large molecular network structure, further enhancing the freezing stability of the dough, reducing the hardness of pre-baked frozen toast, and improving its quality. Attached Figure Description

[0016] Figure 1 This is an internal texture diagram of the toast prepared in the embodiments and comparative examples of the present invention. Detailed Implementation

[0017] The present invention will now be described in detail with reference to the embodiments.

[0018] The general process for making and using pre-baked frozen toast includes: kneading dough → proofing → dividing → shaping → fermentation → pre-baking → freezing → thawing → baking → finished product. Due to the need for freezing, thawing, and secondary baking, large ice crystals can form inside the bread during freezing, affecting its storage and reprocessing quality. Compared to fresh bread, pre-baked frozen bread exhibits a smaller specific volume and is more prone to aging. This invention provides a pre-baked frozen toast and its preparation method to solve the above-mentioned technical problems.

[0019] The first aspect of this invention provides a method for preparing pre-baked frozen toast, comprising the following steps: The first aspect of this invention protects a pre-baked frozen toast, comprising, by weight, the following ingredients: 100-110 parts wheat flour, 60-65 parts water, 10-15 parts white sugar, 2-4 parts salt, 1.6 parts dry yeast, and 0.3-0.5 parts antifreeze agent; wherein the antifreeze agent is propylene glycol alginate; and the protein content of the wheat flour is >12%.

[0020] In some embodiments, the wheat flour is high-gluten flour.

[0021] Understandably, high-gluten flour contains more than 12.2% protein. The higher protein content in high-gluten flour helps form a strong, elastic gluten network during kneading, and during fermentation, it effectively traps the carbon dioxide produced by yeast, allowing the dough to fully expand and resulting in a full-bodied, fluffy loaf of toast. PGA, through its synergistic effect with gluten proteins, improves the freezing stability of pre-baked frozen toast and reduces the hardness of the finished product.

[0022] In some embodiments, the wheat flour is purchased from Yihai Kerry Group.

[0023] It is understandable that one of the main reasons why pre-baked frozen bread experiences a decrease in specific volume and is prone to aging during storage and secondary processing is the formation of ice crystals during dough freezing, and the recrystallization of ice crystals caused by moisture migration due to temperature fluctuations in the frozen dough during storage and transportation. The propylene glycol alginate added in this invention is an alginate esterification derivative. As a hydrophilic colloid, it can form complexes with bound water and gluten protein molecules in the frozen dough system, increasing the water-holding capacity of the frozen dough, altering moisture migration characteristics, and mitigating the damage to the gluten protein structure caused by ice crystal recrystallization. The unesterified carboxyl groups in the propylene glycol alginate of this invention carry a negative charge, which binds to gluten proteins through electrostatic interactions, alleviating the damage to the gluten structure caused by repeated freeze-thaw cycles and maintaining the shape and texture of the toast.

[0024] In some embodiments, the degree of esterification of the propylene glycol alginate is 75-95%, including but not limited to 75%, 80%, 85%, 90%, and 95%, preferably 78.8-92%. By selecting a suitable degree of esterification of propylene glycol alginate as an antifreeze agent and adding it to the dough, the hardness of the toast is reduced, and the specific volume, water retention, and texture of the toast are improved. This effectively alleviates the quality degradation of the toast caused by repeated freeze-thaw cycles, thereby improving the acceptability and sensory evaluation of the product.

[0025] In some embodiments, the propylene glycol alginate is obtained by mixing alginic acid, propylene oxide, and alkali, reacting to obtain a slurry, adjusting the pH, centrifuging, drying the resulting precipitate, and pulverizing it.

[0026] Understandably, by optimizing the preparation process of propylene glycol alginate, the molecular structure of the prepared propylene glycol alginate retains the unesterified carboxylic acid groups (hydrophilic) and the introduced propylene glycol groups (hydrophobic). This unique chemical composition endows propylene glycol alginate with excellent emulsifying, thickening, and stabilizing properties. Propylene glycol alginate can promote the binding of protein molecules, forming a large molecular network structure, enhancing the freezing stability of dough, thereby reducing the hardness of pre-baked frozen toast and improving its quality. If too little propylene glycol alginate is added, the freeze resistance will decrease, and the internal free water will easily form large ice crystals. These ice crystals will pierce the gluten network and pore structure, resulting in a loose and inelastic internal structure, losing the normal fluffy shape of toast.

[0027] In some embodiments, the mass ratio of the alginic acid to the propylene oxide is 1:0.6 to 1, including but not limited to 1:0.6, 1:0.8, and 1:1.

[0028] In some embodiments, the mass of the alkali is 0.5 to 2% of the mass of the alginic acid, including but not limited to 0.5%, 1%, 1.5%, and 2%.

[0029] In some embodiments, the reaction temperature is 50~70°C, including but not limited to 50°C, 55°C, 60°C, 65°C, and 70°C; the pressure is 0.2~0.3MPa, including but not limited to 0.2MPa, 0.25MPa, and 0.3MPa; and the time is 1~3h, including but not limited to 1h, 2h, and 3h.

[0030] In some embodiments, adjusting the pH means adjusting the pH to 3-4, including but not limited to 3, 3.5, and 4.

[0031] A second aspect of this invention protects a method for preparing the pre-baked frozen toast described in the second aspect above, comprising the following steps: S1: Mix the wheat flour, white sugar, salt, and antifreeze in the specified amounts to obtain a premix; S2: Add 1-10 parts water to the dry yeast of the recipe amount and mix to obtain yeast water; S3: Add the yeast water and the remaining water to the premix from step S1 and stir until a dough is formed; S4: After letting the dough from step S3 rest, degas, cut, and shape, it is proofed, baked, and frozen to obtain pre-baked frozen toast.

[0032] In some embodiments, the stirring time in steps S1 and S3 is 22 to 27 minutes, including but not limited to 22 minutes, 24 minutes, 25 minutes, and 27 minutes.

[0033] In some embodiments, step S3 is to obtain a shaped dough using a dough mixer. The present invention does not require a conventional dough mixer, but preferably a dough mixer with different speed settings. However, the speed settings of the dough mixer do not have a significant impact on the effect of the present invention.

[0034] In some embodiments, in step S4, the settling temperature is 2~4℃, including but not limited to 2℃, 3℃, 4℃, and the time is 10~13min, including but not limited to 10min, 11min, 12min, 13min.

[0035] In some embodiments, the proofing temperature is 35~37°C, including but not limited to 35°C, 36°C, and 37°C, and the time is 50~60 minutes, including but not limited to 50 minutes, 55 minutes, and 60 minutes.

[0036] In some embodiments, the baking is carried out using both top and bottom heat, with the top heat temperature being 190~210℃, including but not limited to 190℃, 200℃, and 210℃, and the bottom heat temperature being 180~190℃, including but not limited to 180℃, 185℃, and 190℃, and the baking time being 11~13min, including but not limited to 11min, 12min, and 13min.

[0037] In some embodiments, the freezing temperature is -24 to -18°C, including but not limited to -24°C, -22°C, -20°C, and -18°C, and the freezing time is 2 to 7 days, including but not limited to 2 days, 4 days, and 7 days.

[0038] The following are specific implementation examples.

[0039] Example 1 A pre-baked frozen toast, by weight, comprises the following ingredients: 100 parts high-gluten wheat flour, 60 parts water, 10 parts white sugar, 2 parts salt, 0.3 parts propylene glycol alginate, and 1.6 parts dry yeast. The preparation method of propylene glycol alginate in this embodiment is as follows: 300g of alginic acid, 190g of propylene oxide, and 2g of sodium hydroxide were added to a reaction vessel and reacted. The reaction was carried out at a pressure of 0.2-0.3 MPa and a temperature of 50°C for 3 hours to obtain propylene glycol alginate. The degree of esterification of the propylene glycol alginate obtained in this example was determined to be 78.8% according to GB 1886.226-2016 standard.

[0040] A method for preparing pre-baked frozen toast includes the following steps: (1) Prepare each ingredient according to the above proportions; and add the ingredients according to the above formula.

[0041] (2) Add the dry yeast to 10 parts of warm water at 25°C and stir well to obtain yeast water.

[0042] (3) Add high-gluten wheat flour, white sugar, salt, remaining water, propylene glycol alginate, and yeast water to the dough mixer. First, mix the dough in the first speed setting until it forms a dough, then mix it in the third speed setting until it forms a thin film. The model of the dough mixer is Yingou SM-1508BM.

[0043] (4) Place the kneaded dough at 4℃ for 10 minutes; after the dough has been kneaded, it is degassed, cut and shaped, then placed in a mold and placed in a fermentation box at 35℃ for 50 minutes.

[0044] (5) Place the proofed dough in a preheated oven, control the top heat temperature at 210℃ and the bottom heat temperature at 190℃, and bake for 12 minutes. The pre-baked bread is 80% cooked and should be cooled at room temperature. The 80% cooked product is the product obtained by calculating the baking time of this step based on 80% of the normal baking time. The pre-baking and freezing technology avoids the problem of decreased yeast activity in conventionally frozen dough because the dough has already completed the key fermentation and preliminary baking and shaping in the pre-baking stage. During the subsequent freezing and storage process, the yeast activity has basically no impact on the quality of the finished product.

[0045] (6) After cooling, the pre-baked dough is placed in the refrigerator and frozen at -24℃ for 7 days to obtain pre-baked frozen toast dough.

[0046] Before use, proof the bread in a proofing box for 30 minutes, then bake it at 210℃ top heat and 190℃ bottom heat for 6 minutes to obtain the finished toast.

[0047] Example 2: A pre-baked frozen toast, by weight, comprises the following components: 100 parts high-gluten wheat flour, 60 parts water, 15 parts granulated sugar, 2 parts salt, 0.3 parts propylene glycol alginate, and 1.6 parts dry yeast. The degree of esterification of the propylene glycol alginate is 86.7%. The preparation method of the propylene glycol alginate is as follows: 200 g of alginic acid, 200 g of propylene oxide, and 0.2 g of sodium hydroxide were added to a reaction vessel for 3 hours, 0.2 MPa, and 60 °C. The resulting propylene glycol alginate had a degree of esterification of 86.7%.

[0048] A method for preparing pre-baked frozen toast is basically the same as that in Example 1, except that the degree of esterification of propylene glycol alginate prepared in this example is different.

[0049] Example 3 A pre-baked frozen toast is basically the same as in Example 1, except for propylene glycol alginate and its preparation. The preparation method of propylene glycol alginate in this example is as follows: 400g of alginic acid, 360g of propylene oxide, and 3g of sodium hydroxide were added to a reaction vessel for 2 hours, 0.3MPa, and 60℃. The resulting propylene glycol alginate had a degree of esterification of 83.6%.

[0050] A method for preparing pre-baked frozen toast is basically the same as that in Example 1, except that propylene glycol alginate is used in this example.

[0051] Example 4 A pre-baked frozen toast is basically the same as in Example 1, except for propylene glycol alginate and its preparation. The preparation method of propylene glycol alginate in this example is as follows: 500g of alginic acid, 500g of propylene oxide, and 4g of sodium hydroxide were added to a reaction vessel for reaction. The reaction time was 1 hour, the reaction pressure was 0.3 MPa, and the reaction temperature was 70℃. The resulting propylene glycol alginate had an esterification degree of 91.7%.

[0052] Example 5 It is basically the same as Example 1, except that: the amount of propylene glycol alginate is 0.5 parts.

[0053] Example 6 It is basically the same as Example 2, except that: the amount of propylene glycol alginate is 0.5 parts.

[0054] Example 7 It is basically the same as Example 3, except that the amount of propylene glycol alginate is 0.5 parts.

[0055] Example 8 It is basically the same as Example 4, except that: the amount of propylene glycol alginate is 0.5 parts.

[0056] Comparative Example 1 It is basically the same as Example 1, except that propylene glycol alginate was not added.

[0057] Comparative Example 2 It is basically the same as Comparative Example 1, except that the dough was not frozen and was baked directly until fully cooked, making it a fresh toast.

[0058] That is, step (5) is: put the proofed dough into the preheated oven, control the top heat temperature to 210℃, the pre-baking bottom heat temperature to 190℃, bake for 15 minutes, and get the finished toast.

[0059] Comparative Example 3 It is basically the same as Example 1, except that: the amount of propylene glycol alginate is 0.1 parts.

[0060] Comparative Example 4 It is basically the same as Example 2, except that: the amount of propylene glycol alginate is 0.1 parts.

[0061] Comparative Example 5 It is basically the same as Example 3, except that: the amount of propylene glycol alginate is 0.1 parts.

[0062] Comparative Example 6 It is basically the same as Example 4, except that the amount of propylene glycol alginate is 0.1 parts.

[0063] Comparative Example 7 It is basically the same as Example 1, except that white sugar is omitted.

[0064] Comparative Example 8 It is basically the same as Example 1, except that the amount of high-gluten flour added is 120 parts.

[0065] Comparative Example 9 It is basically the same as Example 1, except that the amount of high-gluten flour added is 60 parts.

[0066] Comparative Example 10 It is basically the same as Example 1, except that 100 parts of medium-gluten flour were used, which was purchased from Yihai Kerry Group.

[0067] Test example: The pre-baked doughs obtained in Examples 1-8 and Comparative Examples 1, 3-10 were placed in a proofing box and proofed for 30 minutes. Then, they were re-baked for 6 minutes at an upper heat temperature of 210°C and a lower heat temperature of 190°C to obtain the finished toast.

[0068] Using conventional testing methods in the field, the baking loss, specific volume, moisture content, and hardness (measured by a texture analyzer) of the finished toasts prepared from the pre-baked doughs described in Examples 1-8 and Comparative Examples 1-10 were measured respectively, and the results are shown in Table 1 below.

[0069] Table 1. Baking loss, specific volume, moisture content of bread crumb, and hardness of toast.

[0070] As shown in Table 1, the pre-baked frozen toast products prepared in Examples 1-8 and Comparative Examples 3-6 have a better overall evaluation than Comparative Example 1, indicating that the different degrees of esterification of propylene glycol alginate used in this invention can effectively improve the baking loss, bread core moisture content, and hardness of pre-baked frozen toast. This is because propylene glycol alginate can bind to water molecules through hydrogen bonds. In addition, the unesterified carboxyl groups carry a negative charge and can bind to gluten proteins through electrostatic interactions. The two work synergistically to reduce the damage to the structure caused by ice crystals and reduce the damage to the dough caused by ice crystals during freezing. Propylene glycol alginate increases the specific volume of the toast product, indicating that its binding with gluten proteins can strengthen the internal network structure of the toast molecules, retain more carbon dioxide produced by yeast, and allow it to expand more during fermentation and baking. The toast with 0.3 parts and 0.5 parts of propylene glycol alginate added have similar effects on improving the pre-baked frozen toast. Considering cost, adding 0.3 parts is more appropriate. Adding 0.1 parts of propylene glycol alginate resulted in a relatively low specific volume and an increased hardness value.

[0071] Comparative Example 7 omitted sugar, which not only reduced the specific volume but also increased the baking loss rate. Sugar is quickly utilized and broken down by yeast to produce carbon dioxide; without sugar, yeast can only slowly break down the starch in the flour, resulting in insufficient dough expansion. Therefore, this affected the quality of pre-baked frozen toast and its further processed products. Comparative Examples 8-10 changed the content and type of flour. The core of different flours is the gluten protein content, indicating that both excessively strong and weak gluten protein will affect dough fermentation, thus reducing the specific volume of the pre-baked frozen toast.

[0072] Figure 1 These are internal structural diagrams of the finished bread products from Examples 1-4 and Comparative Example 1 of the present invention. From... Figure 1 It can be seen that the toast in Comparative Example 1 without added propylene glycol alginate has uneven pore size and large holes, while the pore size in the Example is more uniform and regularly distributed, indicating that the addition of propylene glycol alginate is beneficial to maintaining the stability of the toast structure.

[0073] The judges will comprehensively consider the bread's color, texture, and quality, and then give scores for each aspect and a total score. See Table 2 for the specific scoring criteria. The evaluation is divided into five aspects: crust color, crust color, texture, crust texture, and taste, for a total of 100 points.

[0074] Table 2 Sensory Evaluation Table for Pre-baked Frozen Toast

[0075] Table 3 Sensory evaluation of pre-baked frozen toast bread (unit: points)

[0076] Table 3 shows that the addition of an appropriate amount of highly esterified propylene glycol alginate, in synergy with other components, increases the overall acceptability of the toast and improves its sensory score.

[0077] The above description is merely a preferred embodiment of the present invention, and the present invention is not limited to the above embodiments. It is understood that other improvements and variations that are directly derived or conceived by those skilled in the art without departing from the spirit and concept of the present invention should be considered to be included within the protection scope of the present invention.

Claims

1. A pre-baked frozen toast, characterized in that, By weight, it includes the following ingredients: 100-110 parts wheat flour, 60-65 parts water, 10-15 parts white sugar, 2-4 parts salt, 1.6 parts dry yeast, and 0.3-0.5 parts antifreeze agent; The antifreeze agent is propylene glycol alginate; The protein content of the wheat flour is >12%.

2. The pre-baked frozen toast according to claim 1, characterized in that, The wheat flour is high-gluten flour.

3. The pre-baked frozen toast according to any one of claims 1-2, characterized in that, The wheat flour was purchased from Yihai Kerry Group.

4. The pre-baked frozen toast according to claim 1, characterized in that, The degree of esterification of the propylene glycol alginate is 75-95%.

5. The pre-baked frozen toast according to claim 1, characterized in that, The propylene glycol alginate is obtained by mixing alginic acid, propylene oxide, and alkali, reacting to obtain a slurry, adjusting the pH, centrifuging, drying the resulting precipitate, and pulverizing it.

6. The pre-baked frozen toast according to claim 5, characterized in that, The mass ratio of the alginic acid to the propylene oxide is 1:0.6~1; The mass of the alkali is 0.5 to 2% of the mass of the alginic acid.

7. The pre-baked frozen toast according to claim 5, characterized in that, The reaction is carried out at a temperature of 50-70℃, a pressure of 0.2-0.3MPa, and a time of 1-3h. The pH adjustment refers to adjusting the pH to 3-4.

8. A method for preparing pre-baked frozen toast according to any one of claims 1-7, characterized in that, Includes the following steps: S1: Mix the wheat flour, white sugar, salt, and antifreeze in the specified amounts to obtain a premix; S2: Add 1-10 parts water to the dry yeast of the recipe amount and mix to obtain yeast water; S3: Add the yeast water and the remaining water to the premix from step S1 and stir until a dough is formed; S4: After letting the dough from step S3 rest, degas, cut, and shape, it is proofed, baked, and frozen to obtain pre-baked frozen toast.

9. The method according to claim 8, characterized in that, In steps S1 and S3, the stirring time is 22-27 minutes.

10. The method according to claim 8, characterized in that, In step S4, the settling temperature is 2~4℃ and the time is 10~13min; The proofing temperature is 35~37℃, and the time is 50~60min; The baking process uses both top and bottom heating elements, with the top heating element temperature at 190~210℃ and the bottom heating element temperature at 180~190℃, and the baking time at 11~13 minutes. The freezing temperature is -24 to -18°C, and the freezing time is 2 to 7 days.

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