A frozen flour product composite improver and its application

Abstract

The application discloses a frozen flour product composite improver and application thereof, and the composite improver is composed of glycine acylated lentinan and casein phosphopeptide-calcium-surfactin chelate, a two-stage mixing process is adopted, and then, after leavening, rapid freezing and packaging, frozen dough is obtained. In the first stage, the proportion of wheat flour is controlled to prepare a flowable batter matrix, and gluten proteins are fully hydrated to form cluster-like pre-aggregates; in the second stage, the remaining wheat flour, the composite improver and leavening agents are added to promote the cross-linking and aggregation of the gluten network. The composite improver can promote the cross-linking of gluten proteins, enhance the hydrogen bond density, strengthen the strength of gluten macro-molecules, continuously inhibit the recrystallization of ice crystals, regulate the content of freezable water during the frozen storage of the dough, maintain the continuity of the gluten network and the activity of the yeast, and effectively solve the problems of the destruction of the gluten structure, the inactivation of the yeast and the quality deterioration of the traditional frozen dough.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, specifically relating to a composite improver for frozen rice and flour products and its application. Background Technology

[0002] Frozen dough is a product made primarily from wheat flour, with the addition of water, leavening agents, salt, improvers, and other auxiliary ingredients, through a process of kneading, fermentation, shaping, quick-freezing, and packaging. With the prevalence of fast-paced lifestyles, frozen dough, due to its long shelf life and convenient consumption, has become a core ingredient in processed foods such as bread, steamed buns, noodles, and pastries. However, issues such as the proofing process reducing gluten macromer content and affecting gluten network properties, ice crystal growth, gluten protein denaturation, and moisture migration during freezing and thawing directly lead to deterioration of the dough, including a dry texture, easy cracking after steaming or boiling, shrinkage in volume after baking, and loss of flavor, thus reducing consumer acceptance.

[0003] Existing technologies for improving the quality of frozen dough mainly focus on a single aspect of freeze resistance or freeze-thaw stability. For example, isothermal buffered freezing storage involves immersing the frozen dough in a high specific heat medium solution outside the packaging at -20°C. Although the high specific heat medium solution can reduce temperature fluctuations, this storage method is quite inconvenient, and the food safety risks arising from the immersion of the high specific heat medium solution into the frozen dough need to be considered. Physical field effects (such as ultrasound, electromagnetic fields, etc.) can regulate ice crystal morphology to some extent, but they can reduce the content of gluten polymers in the dough, thus having an unintended impact on the gluten structure. Chemically modified gluten proteins or starches can improve network strength, but they often introduce exogenous chemical substances, which can lead to changes in flavor. Therefore, the above technologies mainly focus on improving the quality of frozen dough during storage. Summary of the Invention

[0004] Technical Problem to be Solved: To address the aforementioned technical problems, the present invention aims to disclose a composite improver for frozen rice and flour products and its application. This composite improver is composed of glycine-amyled lentinan and casein phosphopeptide-calcium-surfactin chelate. A two-stage mixing process is employed, followed by proofing, rapid freezing, and packaging to obtain frozen dough. In the first stage, the proportion of wheat flour is controlled at 30-50% to prepare a fluid batter matrix. In the second stage, the remaining wheat flour, the composite improver, and the leavening agent are added to prepare high-quality frozen dough. This invention effectively solves the problems of gluten structure damage, yeast inactivation, and quality deterioration in traditional frozen dough.

[0005] Technical solution: A method for preparing a composite improver for frozen rice and flour products, comprising the following steps: S1. Preparation of glycine-amiditized lentinan L-cysteine ​​hydrochloride solution and EDTA were added to papain solution to obtain activated enzyme solution. Glycine solution and lentinan solution were added to the activated enzyme solution in sequence and reacted at -8-0℃ under N2 conditions for 20-28h. After enzyme inactivation, the enzyme was extracted with alcohol, filtered, washed and dried to obtain glycine-amiditized lentinan. S2. Preparation of casein phosphopeptide-calcium-surfactin chelate Casein phosphopeptide and surfactantin were dissolved in water and the pH was adjusted to 7-8. Calcium chloride solution was added for chelation treatment. After alcohol precipitation, filtration, washing and drying, CPP-Ca-SF chelate was obtained. S3. A composite modifier was prepared by mixing glycine-amyled lentinan and CPP-Ca-SF chelate.

[0006] Furthermore, in S1, the mass concentration of papain solution is 1-3%, the volume ratio of papain solution to L-cysteine ​​hydrochloride solution is (6-10):1, and the amount of EDTA added is 0.01-0.06% based on the volume of papain solution.

[0007] Furthermore, in S1, the volume ratio of glycine solution to activating enzyme solution is (0.5-1):1, and the concentration of glycine solution is 10-30 mmol / L; the volume ratio of lentinan solution to activating enzyme solution is (0.4-2):1, and the mass fraction of lentinan solution is 2-6%.

[0008] Furthermore, in S2, the mass ratio of casein phosphopeptide, surfactantin, and calcium chloride is (1-3):(0.5-2):2, and the chelation treatment conditions are a temperature of 25-45℃ and a time of 0.5-2.5h; in S3, the ratio of glycine amidated lentinan to CPP-Ca-SF chelate is (1-4.5):(2-3.5).

[0009] The above-mentioned composite improver for frozen rice and flour products is used to improve the processing and storage quality of frozen dough.

[0010] A method for improving the processing and storage quality of frozen dough using a compound improver for frozen rice and flour products includes the following steps: Step 1. First, mix 30-50% wheat flour, 50-70% water (by total mass of wheat flour), 1-3% wheat gluten, and 0.5-2% salt to make a batter base; Step 2. Add 50-70% wheat flour, 2.5-4.5% compound improver, and 1.5-4% leavening agent to the batter base, and continue mixing and stirring to form dough; the wheat flour in Step 1 and Step 2 is based on 100% mass, and the additives such as gluten, salt, compound improver, and leavening agent are all based on the total mass of wheat flour; Step 3. The dough is then proofed, quickly frozen, packaged, and stored.

[0011] Furthermore, the starter culture is composed of Angel semi-dry active yeast and Leuconostoc membranaceus in a mass ratio of (1-3):1.

[0012] Beneficial effects: 1. This invention employs a two-stage mixing process in the preparation of frozen dough. In the first stage, the proportion of wheat flour is controlled between 30-50% to prepare a fluid paste matrix. During the mixing process, the gluten proteins in the wheat flour are fully hydrated, increasing the gluten aggregation index. This allows the wheat flour to form stable clusters of pre-aggregates through hydrogen bonding and hydrophobic interactions, providing a basis for the expansion of the gluten network in the second stage of dough preparation. However, when the proportion of wheat flour in the first stage exceeds 50%, the gluten proteins and starches in the wheat flour have already formed a continuous network. In the second stage, the gluten proteins and starches in the remaining wheat flour accumulate disorderly in the dense network, resulting in poor continuity of the gluten network in the dough. In the second stage, the remaining wheat flour, compound improver, and leavening agent are added to the batter matrix and mixed until a smooth and firm dough is formed. The gluten protein in the wheat flour cross-links with the clustered pre-aggregates of the batter system through multi-level interactions, which promotes the formation of a continuous and dense gluten network by gluten protein and starch. At the same time, the fluidity of the batter matrix is ​​conducive to the uniform dispersion of the compound improver and leavening agent, which can provide a stable gas-generating structural basis for the proofing stage and effectively solve the problem of disordered gluten aggregation caused by water competition or excessive mechanical shearing in the traditional one-step method.

[0013] 2. In the proofing stage, this invention crosslinks the amide bonds of lentinan with gluten protein amino acid residues and starch polysaccharide chains via glycine amidation. Glycine also enhances the hydrogen bond density of the gluten network, significantly improving its elasticity. Furthermore, the casein phosphopeptide-calcium-surfactant chelate (CPP-Ca-SF chelate) connects the carboxyl and phosphate groups in gluten protein through calcium bridges, increasing the strength of glutenin macropolymers in the dough gluten network. This counteracts the mechanical forces exerted during yeast gas production and expansion during proofing, thus maintaining stable glutenin polymer content and continuously increasing the gluten aggregation index. The Angel semi-dry active yeast in the starter culture, due to its high intracellular trehalose accumulation, stabilizes the membrane lipids and proteins of yeast cells. Additionally, the dextran produced by *Leuconostoc mesenteroides* during proofing forms a sticky coating layer outside the yeast cells, acting as a physical barrier to reduce freezing damage. This allows the yeast cells to maintain structural integrity and metabolic dormancy, laying an active foundation for subsequent thawing and recovery.

[0014] 3. In this invention, the CPP-Ca-SF chelate continuously exerts calcium bridging effects during the storage of frozen dough, enhancing the cross-linking between gluten proteins and making the gluten network less susceptible to damage during repeated freeze-thaw cycles. Glycine-amyled lentinan can convert free water into bound water through its high uronic acid properties, regulating the content of freezeable water during the storage of frozen dough. At the same time, the glycine-modified amide groups can also eliminate the electrostatic repulsion between gluten proteins in frozen dough, synergistically enhancing the interaction between gluten proteins and polysaccharides. The three-dimensional network formed by polysaccharides and gluten physically constrains the growth space of ice crystals, further weakening the damage to the gluten structure and maintaining the continuity and elasticity of the gluten network. In addition, the trehalose accumulated in the yeast cells of the starter culture can protect them from damage by ice crystals, and dextran can further synergistically inhibit the recrystallization of ice crystals and make the ice crystals small and evenly distributed, ensuring that the frozen dough still has good processing quality after thawing. Attached Figure Description

[0015] Figure 1 The content of gluten macromers and the gluten aggregation index in the batter matrix of Examples 6-8 and Comparative Example 4; Figure 2 The contents of glutenin macromers, free thiol groups, and disulfide bonds in Examples 6-12 and Comparative Examples 4-10; Figure 3 The tensile properties of Examples 6-12 and Comparative Examples 4-10 are shown, where A represents tensile energy, B represents elongation, C represents tensile resistance, and D represents stretch ratio. Figure 4 The GMP changes of the frozen dough described in Example 9 and Comparative Examples 4-10 during storage; Figure 5 The changes in frozen dough (FW) during storage for the frozen dough described in Example 9 and Comparative Examples 4-10; Figure 6 The changes in the relative retention rate of yeast activity during storage of the frozen dough described in Example 9 and Comparative Examples 4-10; Figure 7 The specific volume and sensory evaluation of the steamed buns obtained after thawing the frozen dough stored in Example 9 and Comparative Examples 4-10; Figure 8 The textural properties of steamed buns obtained after thawing the frozen dough stored in Examples 9 and Comparative Examples 4-10 are given, where A represents hardness, B represents elasticity, and C represents chewiness. Detailed Implementation

[0016] The present invention will be further described below with reference to embodiments. These embodiments are illustrative of the present invention, but the present invention is not limited to these embodiments: Example 1

[0017] A method for preparing a composite improver for frozen rice and flour products includes the following steps: S1. Activate the enzyme solution by mixing 600 mL of 1% papain solution, 100 mL of L-cysteine ​​hydrochloride solution, and 60 mg of EDTA. Then, add 350 mL of 10 mmol / L glycine solution and 280 mL of 2% lentinan solution. After mixing, react for 20 h at -4 °C under nitrogen protection. Inactivate the enzyme by boiling in a water bath for 10 min. Then, add 3 times the volume of anhydrous ethanol for alcohol precipitation, filter and collect the precipitate, and freeze-dry to obtain glycine-amylated lentinan. S2. Weigh 1.0 g casein phosphopeptide and 0.5 g surfactin and dissolve them in 100 mL of water. After stirring and dissolving, adjust the pH value to 7.0. Then add 2.0 g calcium chloride and mix well. Chelate the mixture at 30 °C for 0.5 h. Then add 2 times the volume of anhydrous ethanol for alcohol precipitation. Filter and collect the precipitate. Wash it with 100 mL of water and 100 mL of anhydrous ethanol. Freeze-dry to obtain CPP-Ca-SF chelate. S3. Repeat steps S1 and S2 to obtain 10.0g of glycine-amyled lentinan and 20.0g of CPP-Ca-SF chelate, which are then mixed to obtain a composite modifier. Example 2

[0018] A method for preparing a composite improver for frozen rice and flour products includes the following steps: S1. Activate the enzyme solution by mixing 800 mL of 2% papain solution, 100 mL of L-cysteine ​​hydrochloride solution, and 280 mg of EDTA. Then, add 720 mL of 20 mmol / L glycine solution and 960 mL of 4% lentinan solution. After mixing, react for 24 h at -4 °C under nitrogen protection. Inactivate the enzyme by boiling in a water bath for 10 min. Then, add 3 times the volume of anhydrous ethanol for alcohol precipitation, filter and collect the precipitate, and freeze-dry to obtain glycine-amylated lentinan. S2. Weigh 2.0g casein phosphopeptide and 1.2g surfactin and dissolve them in 100mL of water. After stirring and dissolving, adjust the pH to 7.5. Then add 2.0g calcium chloride and mix well. Chelate the mixture at 35℃ for 1.5h. Then add 2 times the volume of anhydrous ethanol for alcohol precipitation. Filter and collect the precipitate. Wash with 100mL of water and 100mL of anhydrous ethanol. Freeze-dry to obtain CPP-Ca-SF chelate. S3. Repeat steps S1 and S2 to obtain 25.0g of glycine-amyled lentinan and 30.0g of CPP-Ca-SF chelate, which are then mixed to obtain a composite modifier. Example 3

[0019] A method for preparing a composite improver for frozen rice and flour products includes the following steps: S1. Activate the enzyme solution by mixing 900 mL of 2% papain solution, 100 mL of L-cysteine ​​hydrochloride solution, and 450 mg of EDTA. Then, add 810 mL of 15 mmol / L glycine solution and 1000 mL of 3.5% lentinan solution sequentially. After mixing, react for 20 h at -4 °C under nitrogen protection. Inactivate the enzyme by boiling in a water bath for 10 min. Then, add 3 times the volume of anhydrous ethanol for alcohol precipitation, filter and collect the precipitate, and freeze-dry to obtain glycine-amylated lentinan. S2. Weigh 2.5g casein phosphopeptide and 1.8g surfactin and dissolve them in 100mL of water. After stirring and dissolving, adjust the pH to 7.0. Then add 2.0g calcium chloride and mix well. Chelate the mixture at 40℃ for 2h. Then add 2 times the volume of anhydrous ethanol for alcohol precipitation. Filter and collect the precipitate. Wash it with 100mL of water and 100mL of anhydrous ethanol. Freeze-dry to obtain CPP-Ca-SF chelate. S3. Repeat steps S1 and S2 to obtain 35g of glycine-amyled lentinan and 32g of CPP-Ca-SF chelate, which are then mixed to obtain a composite modifier. Example 4

[0020] A method for preparing a composite improver for frozen rice and flour products includes the following steps: S1. 700 mL of 1% papain solution, 100 mL of L-cysteine ​​hydrochloride solution, and 60 mg of EDTA were stirred and mixed to obtain an activated enzyme solution; then 560 mL of 10 mmol / L glycine solution and 800 mL of 3.5% lentinan solution were added sequentially, mixed, and reacted continuously at -5℃ under nitrogen protection for 24 h. The enzyme was then inactivated by boiling water bath for 10 min. Subsequently, 3 times the volume of anhydrous ethanol was added for alcohol precipitation, the precipitate was collected by filtration, and freeze-dried to obtain glycine-amylated lentinan. S2. Weigh 1.5g casein phosphopeptide and 1.0g surfactin and dissolve them in 100mL of water. After stirring and dissolving, adjust the pH to 7.0. Then add 2.0g calcium chloride and mix well. Chelate the mixture at 30℃ for 1h. Then add 2 times the volume of anhydrous ethanol for alcohol precipitation. Filter and collect the precipitate. Wash it with 100mL of water and 100mL of anhydrous ethanol. Freeze-dry to obtain CPP-Ca-SF chelate. S3. Repeat steps S1 and S2 to obtain 15.0g of glycine-amyled lentinan and 25.0g of CPP-Ca-SF chelate, which are then mixed to obtain a composite modifier. Example 5

[0021] A method for preparing a composite improver for frozen rice and flour products includes the following steps: S1. Activate the enzyme solution by stirring and mixing 600 mL of 3% papain solution, 100 mL of L-cysteine ​​hydrochloride solution, and 60 mg of EDTA. Then, add 700 mL of 10 mmol / L glycine solution and 1000 mL of 3% lentinan solution in sequence. After mixing, react for 25 h at -8 °C under nitrogen protection. Inactivate the enzyme by boiling water bath for 10 min. Then, add 3 times the volume of anhydrous ethanol for alcohol precipitation, filter and collect the precipitate, and freeze-dry to obtain glycine-amylated lentinan. S2. Weigh 3.0g casein phosphopeptide and 2g surfactin and dissolve them in 100mL of water. After stirring and dissolving, adjust the pH to 7.0. Then add 2.0g calcium chloride and mix well. Chelate the mixture at 45℃ for 2.5h. Then add 2 times the volume of anhydrous ethanol for alcohol precipitation. Filter and collect the precipitate. Wash it with 100mL of water and 100mL of anhydrous ethanol. Freeze-dry to obtain CPP-Ca-SF chelate. S3. Repeat steps S1 and S2 to obtain 20.0g of glycine-amyled lentinan and 15.0g of CPP-Ca-SF chelate, which are then mixed to obtain a composite modifier. Comparative Example 1

[0022] The difference between this comparative example and Example 2 is that glycine-amyled lentinan is replaced with lentinan; the remaining operations are the same as in Example 2. Comparative Example 2

[0023] The difference between this comparative example and Example 2 is that no casein phosphopeptide is added; the remaining operations are the same as in Example 2. Comparative Example 3

[0024] The difference between this comparative example and Example 2 is that surfactantin is not added; the remaining operations are the same as in Example 2. Example 6

[0025] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 300g of wheat flour, 500mL of purified water, 10g of wheat gluten, and 5g of edible salt. Put them into the container of a dough mixer and stir for 15 minutes until the batter base is prepared. Step 2. Add 700g of wheat flour to the batter base, along with 25g of the composite improver prepared in Example 1 and 15g of the composite starter (7.5g of Angel semi-dry active yeast). + 7.5g of Leuconostoc membranaceus was added, and the dough was continuously stirred and kneaded to obtain fresh dough. Step 3. Place the fresh dough in a proofing box and proof at 28°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Example 7

[0026] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 400g of wheat flour, 500mL of purified water, 10g of wheat gluten, and 5g of edible salt. Put them into the container of a dough mixer and stir for 15 minutes until the batter base is prepared. Step 2. Add 600g of wheat flour to the batter base, along with 25g of the composite improver prepared in Example 1 and 15g of the composite starter (7.5g of Angel semi-dry active yeast). + 7.5g of Leuconostoc membranaceus was added, and the dough was continuously stirred and kneaded to obtain fresh dough. Step 3. Place the fresh dough in a proofing box and proof at 30°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Example 8

[0027] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 500g of wheat flour, 500mL of purified water, 10g of wheat gluten, and 5g of edible salt. Put them into the container of a dough mixer and stir for 15 minutes until the batter base is prepared. Step 2. Add 500g of wheat flour to the batter base, along with 25g of the composite improver prepared in Example 1 and 15g of the composite starter (7.5g of Angel semi-dry active yeast). + 7.5g of Leuconostoc membranaceus was added, and the dough was continuously stirred and kneaded to obtain fresh dough. Step 3. Place the fresh dough in a proofing box and proof at 35°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Comparative Example 4

[0028] The difference between this comparative example and Example 7 is that the proportion of wheat flour in S1 is adjusted to 55%, as follows: A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 550g of wheat flour, 500mL of purified water, 10g of wheat gluten, and 5g of edible salt. Put them into the container of a dough mixer and stir for 15 minutes until the batter base is prepared. Step 2. Add 450g of wheat flour to the batter base, along with 25g of the composite improver prepared in Example 1 and 15g of the composite starter (7.5g of Angel semi-dry active yeast). +7.5g of Leuconostoc membranaceus was added, and the dough was continuously stirred and kneaded to obtain fresh dough. Step 3. Place the fresh dough in a proofing box and proof at 30°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough.

[0029] The quality characteristics of the batter matrix prepared in Examples 6-8 and Comparative Example 4 were evaluated using the gluten macromer content and gluten aggregation index as evaluation indicators. The specific methods for determining the gluten macromer content and gluten aggregation index are as follows: ① Gluten macromer content: Weigh 5g of batter matrix, add 30mL of 1.5% SDS solution, shake for 1h, centrifuge at 5000rpm for 20min to remove the supernatant, and determine the nitrogen content of the precipitate by the biuret method, which is the content of glutenin macromers.

[0030] ② Gluten protein aggregation index: After letting the fresh batter stand for 8 minutes, dilute it with 250 mL of water and stir it on a plate mixer for 15 minutes. Then add 1000 mL of water and continue stirring for 15 minutes to further wash the suspension. Pour the suspension into a vibrating sieve and pass it through pores of 400 μm, 200 μm, and 80 μm in sequence. During the sieving process, wash the retained gluten protein components with 1000 mL of water. The recovered gluten protein is freeze-dried, weighed, and analyzed for gluten protein aggregation index (GPAI) (%) = W 400 / Wt×100%, where W 400 Wt represents the protein content retained on a 400μm sieve, and Wt represents the total gluten protein content recovered.

[0031] Depend on Figure 1 It can be seen that the gluten macromer content (GMP) and gluten aggregation index (GPAI) of the paste matrix in S1 described in Examples 6-8 increase with the increase of wheat flour content, while the gluten macromer content (GMP) and gluten aggregation index (GPAI) of Comparative Example 4 (wheat flour content of S1 is 55%) are significantly reduced. This indicates that the paste matrix obtained when the wheat flour content of the first stage mixture is between 30-50% has formed a good gluten network. However, once the wheat flour content exceeds 50%, the viscosity of the paste increases significantly, which prevents the gluten protein from being fully hydrated in the early stage. Furthermore, the starch granules absorb water and swell to form a continuous and dense network, which hinders the aggregation and cross-linking of gluten protein, thereby reducing the gluten macromer content and gluten aggregation index. Example 9

[0032] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 400g of wheat flour, 500mL of purified water, 20g of wheat gluten, and 12.5g of edible salt. Put them into the container of a dough mixer and stir until the batter base is prepared. Step 2. Add 600g of wheat flour to the batter base, along with 30g of the composite improver prepared in Example 2 and 25g of the composite starter (18g of Angel semi-dry active yeast). + 7g of Leuconostoc membranaceus), continue stirring and kneading to obtain fresh dough; Step 3. Place the fresh dough in a proofing box and proof at 35°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Example 10

[0033] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 400g of wheat flour, 600mL of purified water, 10g of wheat gluten, and 5g of edible salt. Put them into the container of a dough mixer and stir until the batter base is prepared. Step 2. Add 600g of wheat flour to the batter base, along with 30g of the composite improver prepared in Example 3, 20g of the composite starter (12g of Angel semi-dry active yeast). + 8g of Leuconostoc membranaceus), continue stirring and kneading to obtain fresh dough; Step 3. Place the fresh dough in a proofing box and proof at 28°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Example 11

[0034] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 400g of wheat flour, 500mL of purified water, 25g of wheat gluten, and 17.5g of edible salt. Put them into the container of a dough mixer and stir until the batter base is prepared. Step 2. Add 600g of wheat flour to the batter base, along with 40g of the composite improver prepared in Example 4 and 30g of the composite starter (22.5g of Angel semi-dry active yeast). + 7.5g of Leuconostoc membranaceus was added, and the dough was continuously stirred and kneaded to obtain fresh dough. Step 3. Place the fresh dough in a proofing box and proof at 30°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Example 12

[0035] A method for improving the processing and storage quality of frozen dough includes the following steps: Step 1. Based on 1000g of wheat flour, weigh out 400g of wheat flour, 700mL of purified water, 30g of wheat gluten, and 15g of edible salt. Put them into the container of a dough mixer and stir until the batter base is prepared. Step 2. Add 600g of wheat flour to the batter base, along with 45g of the composite improver prepared in Example 5 and 40g of the composite starter (30g of Angel semi-dry active yeast). + 10g of Leuconostoc membranaceus), continue stirring and kneading to obtain fresh dough; Step 3. Place the fresh dough in a proofing box and proof at 30°C for 30 minutes. Quickly freeze and vacuum pack to obtain frozen dough. Comparative Example 5

[0036] The difference between this comparative example and Example 9 is that the composite modifier prepared in Comparative Example 1 is used; the remaining operations are the same as in Example 9. Comparative Example 6

[0037] The difference between this comparative example and Example 9 is that the composite modifier prepared in Comparative Example 2 is used; the remaining operations are the same as in Example 9. Comparative Example 7

[0038] The difference between this comparative example and Example 9 is that the composite modifier prepared in Comparative Example 3 is used; the remaining operations are the same as in Example 9. Comparative Example 8

[0039] The difference between this comparative example and Example 9 is that the composite modifier prepared in Example 2 is not added; the remaining operations are the same as in Example 9. Comparative Example 9

[0040] The difference between this comparative example and Example 9 is that Leuconostoc membranaceus is not added; the remaining procedures are the same as in Example 9. Comparative Example 10

[0041] The difference between this comparative example and Example 9 is that no gluten powder is added; the remaining operations are the same as in Example 9. Performance testing

[0042] (1) Content of glutenin macromers, free sulfhydryl groups and disulfide bonds The frozen dough sample was freeze-dried in a SY-10 vacuum freeze dryer and then ground through a 200-mesh sieve to obtain the sample to be tested. The content of gluten macromers, free thiol groups and disulfide bonds were analyzed according to the following method.

[0043] ① Gluten macromer content: Take 500 mg of lyophilized sample powder into a 50 mL centrifuge tube, add 10 mL of 1.5% sodium dodecyl sulfate and stir magnetically at 25 °C for 1 h. Centrifuge at 8500 r / min for 20 min and discard the supernatant. Repeat the extraction twice with the precipitate. Carefully scrape off the upper gel of the precipitate and determine the gluten macromer content using a fully automated Kjeldahl nitrogen analyzer. ② Content of free thiol groups and disulfide bonds: Accurately weigh 75 mg of lyophilized sample powder, add 1 mL of Tris-glycine buffer, mix well, then add 4.7 g of guanidine hydrochloride, and adjust the volume to 10 mL with buffer solution. For thiol group determination, take 1 mL of the above solution, add 4 mL of urea-guanidine hydrochloride solution and 0.05 mL of L'Illman reagent to a 10 mL centrifuge tube, and measure the absorbance at 412 nm. For disulfide bond determination, take 1 mL of the above solution, add 0.05 mL of β-mercaptoethanol and 4 mL of urea-guanidine hydrochloride solution to a 10 mL centrifuge tube, incubate for 1 h, add 10 mL of 12% trichloroacetic acid, centrifuge at 10000 r / min for 10 min, discard the supernatant, wash the precipitate twice with 5 mL of 12% trichloroacetic acid, then add 10 mL of 8 mol / L urea solution, shake to dissolve the precipitate completely, and finally add 0.04 mL of L'Illman reagent, and measure the absorbance at 412 nm. Calculate the thiol content and disulfide bond content using the formula, where the thiol content (μmol / g) = (75.35 × A) 412 ×D) / C; Disulfide bond content (μmol / g) = (total thiol content - free thiol content) / 2, where: 73.53 represents the molar extinction coefficient of Ellman's reagent, D represents the dilution factor, and C represents the protein mass concentration.

[0044] (2) Tensile properties Take a 30 g dough sample and place it in the dough preparation tank of the texture analyzer. Press it into a 60 mm × 2 mm dough strip. Place the dough strip in the test area of ​​the texture analyzer and measure it immediately with an A / KIE probe.

[0045] Depend on Figure 2 and Figure 3It can be seen that the GMP content and disulfide bond content of Examples 6-12 are higher than those of Comparative Examples 4-10, and the free thiol content is lower than that of Comparative Examples 4-10. Moreover, the tensile properties of Examples 6-12 are better than those of Comparative Examples 4-10, with Example 9 showing the best results. The GMP content and disulfide bond formation in Example 9 demonstrate that the dough formed a well-crosslinked gluten network. Compared with Comparative Example 4, it further proves that when 30-50% wheat flour is mixed with water to form a fluid paste matrix in the first stage, the gluten protein is fully hydrated under sufficient water conditions. Hydrogen bonds and hydrophobic interactions drive the gluten protein molecules to aggregate in an orderly manner, forming stable clusters of pre-aggregates. Furthermore, the degree of hydration and aggregation of gluten protein in the paste matrix reaches a balance. The presence of this pre-aggregate provides a structural template for the expansion of the gluten network in the second stage, enabling the gluten protein in the remaining wheat flour added later to undergo multi-level crosslinking with the pre-aggregate, ultimately forming a continuous and dense three-dimensional network. The tensile properties of Example 9 show that the gluten network in the dough can effectively resist external deformation, while the high extensibility enables the dough to have good plasticity and adapt to the expansion stress brought about by yeast gas production during the proofing stage, so as to ensure the quality of the dough.

[0046] (3) Storage test The frozen doughs prepared in Example 9 and Comparative Examples 4-10 were stored at -20°C. The content of gluten macromers, the content of freezeable water, and the relative retention rate of yeast activity in the frozen doughs were analyzed on days 0, 10, 20, and 30, respectively. After the storage test, the frozen doughs were steamed and made into steamed buns, and the textural characteristics, sensory evaluation, and specific volume of the steamed buns were analyzed.

[0047] ① Freezeable water content: The amount of freezeable water in the frozen dough was determined using a differential scanning calorimeter (DSC). 25 mg of sample was weighed and sealed in a weighing aluminum DSC pan. An empty crucible was used as a control and placed on the DSC sample plate. The temperature curve was set as follows: equilibrate at 25 °C for 5 min, cool from 25 °C to -30 °C using liquid nitrogen at a rate of 10 °C / min, and then heat to 30 °C at a rate of 10 °C / min. During the heating process, the enthalpy (ΔH) of the melting peak was recorded. The calculation formula is FW (%) = ΔH / (ΔH0 × W0) × 100%, where FW represents the freezeable water content, ΔH represents the melting peak enthalpy, ΔH0 represents the melting peak enthalpy of pure water, and W0 represents the dough moisture content.

[0048] ② Relative retention rate of yeast activity: Cut 5g of the thawed dough from the center and place it in 45 mL of 0.85% sterile physiological saline. Homogenize for 2.5 min to mix evenly. Take the supernatant and perform serial dilutions. Take 100μL of the diluted solution and incubate it in a plate at 37℃ for 48h. The ratio of the number of live yeast cells to the number of live yeast cells in the fresh dough is taken as the relative retention rate of activity.

[0049] Depend on Figure 4 , Figure 5 and Figure 6 It can be seen that during storage, the relative retention rates of GMP and yeast activity in Example 9 and Comparative Examples 4-10 decreased with the extension of storage time, while FW showed an increasing trend. However, Example 9 showed a much better reduction in the relative retention rates of GMP and yeast activity and an increase in FW than Comparative Examples 4-10. The results indicate that the glycine-amiditized lentinan and CPP-Ca-SF chelate in the composite improver can bind free water in frozen dough and convert it into bound water, reducing the proportion of freezeable water and thus reducing the mechanical damage to the gluten network caused by ice crystal formation. It can also neutralize the negative charge on the surface of gluten protein to make the interaction between gluten protein and polysaccharide more compact. The three-dimensional network structure formed can effectively constrain the growth space of ice crystals and inhibit the recrystallization of ice crystals. At the same time, the accumulation of trehalose in yeast cells in the starter can resist the direct damage of ice crystals to the cell structure. The dextran produced by Leuconostoc mesenteroides can not only synergistically protect yeast cells, but also further increase the density of the dough network, thereby ensuring the storage stability of frozen dough.

[0050] ③ Steamed Bun Quality Determination: The thawed dough was steamed in a steamer for 25 minutes, then allowed to stand for 5 minutes, and cooled at room temperature for 1 hour for subsequent index determination. The steamed buns cooled for 1 hour were weighed, and their volume was determined using the millet substitution method. The ratio of volume to mass was the specific volume. The specific method for textural properties was as follows: a 2cm thick, 3cm diameter slice was cut from the center of each steamed bun as the test sample. The parameters were: pre-test speed 1.00mm / s, test speed 3.00mm / s, post-test speed 3.00mm / s, compression ratio 50%, trigger force 5.0g, and interval time 5s. Sensory evaluation was conducted according to Table 1.

[0051] Table 1 Sensory Evaluation Criteria for Steamed Buns

[0052] Depend on Figure 7 and Figure 8 It can be seen that the steamed buns made from the dough stored in Example 9 have higher specific volume and sensory scores than those of Comparative Examples 4-10. Furthermore, the steamed buns made from the dough stored in Example 9 exhibit lower hardness and higher elasticity and chewiness, indicating that the steamed buns made from the dough stored in Example 9 have a fuller shape and a softer, chewier texture. In contrast, the steamed buns made from Comparative Examples 4-10 show a harder texture and a wrinkled surface, resulting in reduced sensory quality. This further demonstrates that Example 9 of this invention uses a two-stage mixing process, combined with the use of a composite improver and a leavening agent, to stabilize the frozen dough during storage, thus resulting in steamed buns with excellent quality characteristics after thawing.

[0053] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the spirit and technical essence of the present invention. Therefore, any simple modifications, equivalent substitutions, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the technical solutions of the present invention, shall still fall within the scope of protection of the present invention.

Claims

1. A method for preparing a composite improver for frozen rice and flour products, characterized in that, Includes the following steps: S1. Preparation of glycine-amiditized lentinan L-cysteine ​​hydrochloride solution and EDTA were added to papain solution to obtain activated enzyme solution. Glycine solution and lentinan solution were added to the activated enzyme solution in sequence and reacted at -8-0℃ under N2 conditions for 20-28h. After enzyme inactivation, the enzyme was extracted with alcohol, filtered, washed and dried to obtain glycine-amiditized lentinan. S2. Preparation of casein phosphopeptide-calcium-surfactin chelate Casein phosphopeptide and surfactantin were dissolved in water and the pH was adjusted to 7-8. Calcium chloride solution was added for chelation treatment. After alcohol precipitation, filtration, washing and drying, CPP-Ca-SF chelate was obtained. S3. A composite modifier was prepared by mixing glycine-amyled lentinan and CPP-Ca-SF chelate.

2. The preparation method of a composite improver for frozen rice and flour products according to claim 1, characterized in that: The mass concentration of papain solution in S1 is 1-3%, the volume ratio of papain solution to L-cysteine ​​hydrochloride solution is (6-10):1, and the amount of EDTA added is 0.01-0.06% based on the volume of papain solution.

3. The preparation method of a composite improver for frozen rice and flour products according to claim 1, characterized in that: The volume ratio of glycine solution to activating enzyme solution in S1 is (0.5-1):1, and the concentration of glycine solution is 10-30 mmol / L.

4. The preparation method of a composite improver for frozen rice and flour products according to claim 1, characterized in that: The volume ratio of lentinan solution to activating enzyme solution in S1 is (0.4-2):1, and the mass fraction of lentinan solution is 2-6%.

5. The preparation method of a composite improver for frozen rice and flour products according to claim 1, characterized in that: In S2, the mass ratio of casein phosphopeptide, surfactantin, and calcium chloride is (1-3):(0.5-2):2, and the chelation treatment conditions are a temperature of 25-45℃ and a time of 0.5-2.5h; in S3, the ratio of glycine amidated lentinan to CPP-Ca-SF chelate is (1-4.5):(2-3.5).

6. A composite improver for frozen rice and flour products prepared by the method according to any one of claims 1-5.

7. The application of the composite improver for frozen rice and flour products according to claim 6 in improving the processing and storage quality of frozen dough.

8. The application according to claim 7, characterized in that, The method for preparing the frozen dough includes the following steps: Step 1. First, mix 30-50% wheat flour, 50-70% water, 1-3% wheat gluten, and 0.5-2% salt to make a batter base; Step 2. Add 50-70% wheat flour, compound improver, and leavening agent to the batter base, and continue mixing and stirring to form a dough; Step 3. The dough is then proofed, quickly frozen, packaged, and stored.

9. The application according to claim 8, characterized in that, In step 2, the starter culture is composed of Angel semi-dry active yeast and Leuconostoc membranaceus in a mass ratio of (1-3):1, and the amount of starter culture added is 1.5-4%; the amount of compound improver added is 2.5-4.5%, all based on the total mass of wheat flour.

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