Preparation method of aluminum-free and alum-free fluffy quick-frozen fried dough stick dough

Abstract

The application provides a preparation method of an aluminum-free and alum-free fluffy quick-frozen fried dough stick dough, and belongs to the field of quick-frozen dough product processing. The fried dough stick dough comprises the following raw materials: wheat flour, coarse grain flour, gluten, a composite swelling agent, modified soybean phospholipid, mono-diglyceride fatty acid ester, mono-diglyceride diacetyl tartaric acid ester and hydroxypropyl methyl cellulose. The coarse grain flour is pre-gelatinized by boiling water, and then the emulsifier is added. After cooling, the remaining flour, oil and ice water are mixed to knead the dough. After relaxation, kneading, vacuum pre-cooling, tabletting, cutting and stacking, the dough is formed by gradient freezing. The modified soybean phospholipid is modified by phospholipase ultrasonic enzymolysis and caprylate exchange. The gluten network is protected by pre-gelatinization, and the air chamber structure is stabilized by the ternary emulsifier (modified soybean phospholipid, mono-diglyceride fatty acid ester and mono-diglyceride diacetyl tartaric acid ester). The gradient freezing fixes the micropores. The technical problems of insufficient aluminum-free fried dough stick puffiness, rough taste caused by coarse grain addition and poor frozen storage stability are solved.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a method for preparing aluminum-free and alum-free fluffy quick-frozen fried dough stick embryos. Background Technology

[0002] Traditional fried dough stick processing heavily relies on alum as the core leavening agent. While alum can create uniform pores during high-temperature decomposition, ensuring the dough sticks are fluffy and crispy, it also leads to excessive aluminum residue in the finished product. Long-term consumption of aluminum-containing fried dough sticks can damage the human nervous system, bone metabolism, and digestive system, failing to meet modern food safety standards and healthy dietary needs. Existing conventional aluminum-free leavening technologies mostly use a single chemical leavening agent, which suffers from problems such as single gas production and uncontrollable gas production rate. Furthermore, the leavening stability throughout the entire process of dough mixing, proofing, quick-freezing, and frying is poor, easily resulting in insufficient fluffiness, uneven pore size, and a hard, dense texture in the fried dough sticks. These technologies cannot completely replace the leavening effect of alum.

[0003] Furthermore, the processing performance of quick-frozen dough after adding whole grains is extremely poor, making industrialization difficult. Currently, most quick-frozen fried dough sticks are made from refined wheat flour, resulting in a monotonous taste and nutritional profile. If whole grain flours (corn flour, buckwheat flour, oat flour, etc.) are directly added to prepare whole-grain fried dough sticks, the lack of gluten protein and high dietary fiber content of these grains will disrupt the gluten network structure of the dough, leading to a significant decrease in dough extensibility and gas retention. Simultaneously, whole grains have high water absorption and uneven moisture distribution. Quick-frozen dough prepared using conventional processes is prone to moisture migration and ice crystal coarsening during low-temperature freezing storage. Upon thawing or direct frying, it is highly susceptible to cracking, collapse, shrinkage, and crumbling. The finished product has poor fluffiness, a rough texture, and high oil absorption, resulting in a short quick-frozen storage period and poor quality stability, making it difficult to meet the needs of industrial-scale quick-frozen production and long-term storage.

[0004] Existing quick-freezing processes are incompatible with the leavening system of raw dough, resulting in low consistency in finished product quality: Current quick-frozen dough preparation mostly employs conventional dough mixing, single proofing, and rapid freezing processes, without optimizing parameters for aluminum-free leavening systems and the characteristics of whole-grain dough. Aluminum-free leavening agents, if their initial gas production is too rapid or too slow, can easily lead to over-proofing in the early stages and weak frying in the later stages when combined with whole-grain dough. Conventional quick-freezing processes can easily damage the microporous structure already formed inside the dough, causing the leavening to fail during refrying, resulting in quality defects such as smaller finished products, stiff outer shells, dense interiors, and softening and hardening after cooling, with significant batch-to-batch quality variations. Summary of the Invention

[0005] The purpose of this invention is to provide a method for preparing aluminum-free and alum-free fluffy quick-frozen fried dough sticks. The fried dough sticks provided by this invention have good fluffiness, crispy taste, rich nutrition and stable quality after freezing.

[0006] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides an aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo, comprising the following raw materials in parts by weight: 65-75 parts wheat flour, 25-35 parts coarse grain flour, 6-10 parts wheat gluten, 3-5 parts compound leavening agent, 0.2-0.4 parts modified soybean lecithin, 0.2-0.4 parts mono- and diglycerides of fatty acids, 0.2-0.4 parts diacetyl tartaric acid mono- and diglycerides, 1.5-2 parts hydroxypropyl methylcellulose, 2-2.5 parts salt, 1.5-2 parts white sugar, 5-8 parts oil, and 55-65 parts water; the compound leavening agent comprises two or more of citric acid, sodium bicarbonate, glucono-δ-lactone, and calcium dihydrogen phosphate.

[0007] Preferably, the wheat flour is composed of high-gluten flour and medium-gluten flour in a weight ratio of (5-7):(3-5).

[0008] Preferably, the whole grain flour includes at least one of corn flour, oat flour, and buckwheat flour.

[0009] Preferably, the method for preparing the modified soybean lecithin includes: mixing soybean lecithin with water, adding phospholipase A2 for ultrasonic enzymatic hydrolysis, inactivating the enzyme, adding caprylic acid and lipase for transesterification, filtering, subjecting the filtrate to high-pressure microfluidic treatment, and drying to obtain the modified soybean lecithin.

[0010] More preferably, the ultrasonic enzymatic hydrolysis is performed at a temperature of 55-60°C, a pH value of 5.8-6.2, a power of 250-350W, a frequency of 25-30kHz, and a time of 2.5-3.5h.

[0011] More preferably, the mass ratio of soybean lecithin to caprylic acid is 1:(6-8); the transesterification temperature is 50-60℃, the stirring rate is 80-120rpm, and the time is 10-12h.

[0012] More preferably, the high-pressure microjet treatment is performed at a pressure of 90-110 MPa, a temperature of 40-50°C, and 3-5 times.

[0013] Preferably, the oil includes at least one of shortening, sunflower seed oil, and palm oil; the water includes ice water at 0-4°C and boiling water.

[0014] This invention also provides a method for preparing the above-mentioned aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo, comprising: boiling 33-36 parts by weight of water and mixing it with coarse grain flour, adding mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, letting it stand, cooling, adding wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and remaining water to form a dough, letting it stand and relax, kneading, vacuum pre-cooling, pressing into sheets, cutting into strips, stacking into shape, and gradient quick-freezing to obtain the aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo.

[0015] Preferably, the gradient quick-freezing method includes: pre-freezing at -15~-10℃ for 25-35 minutes, and then freezing at -35~-40℃ to the embryo center temperature of -18℃.

[0016] The present invention has the following beneficial effects: This invention uses a composite leavening agent composed of two or more of citric acid, sodium bicarbonate, glucono-δ-lactone, and calcium dihydrogen phosphate, completely replacing alum, which is relied upon in traditional fried dough stick making. The aluminum-free composite leavening agent used in this invention eliminates the risk of aluminum toxicity at the source, effectively reducing the food safety risks of fried dough stick products and meeting modern healthy eating needs.

[0017] This invention significantly improves the dietary fiber content and nutritional value of fried dough sticks by adding whole grain powder. However, whole grain powder does not contain gluten protein and has a high dietary fiber content. Direct addition will seriously damage the gluten network structure of the dough, resulting in a significant decrease in the dough's extensibility and gas retention. At the same time, whole grains have strong water absorption and uneven moisture distribution. Quick-frozen dough prepared by conventional processes is prone to moisture migration and ice crystal coarsening during low-temperature freezing. This invention solves the above problems through the following technical methods: adding gluten powder to supplement gluten protein and repair the disruption of the gluten network caused by coarse grain fiber; pregelatinizing the coarse grain powder with boiling water to partially gelatinize the starch and coat the dietary fiber, reducing its intense competition for water and physical damage to the gluten network; constructing a synergistic system of modified soybean lecithin, mono- and diglycerides of fatty acids, and diacetyl tartaric acid mono- and diglycerides of glycerols as emulsifiers, with diacetyl tartaric acid mono- and diglycerides of glycerols ... The synergistic effect of these three ingredients allows whole grain fried dough sticks to retain excellent fluffiness and delicate texture while obtaining rich dietary fiber nutrition, solving the technical problems of traditional whole grain fried dough sticks being rough in texture, crumbly, and prone to cracking and collapsing.

[0018] This invention involves enzymatic modification of soybean lecithin: first, ultrasonic-assisted enzymatic hydrolysis with phospholipase A2 specifically hydrolyzes acyl groups to generate lysophospholipids, significantly enhancing hydrophilicity and interfacial activity; then, octanoic acid and lipase undergo transesterification to introduce medium-chain fatty acids, regulating hydrophobic segments and optimizing the hydrophilic-lipophilic balance; finally, high-pressure microfluidic treatment increases specific surface area, improving dispersibility in the aqueous phase and interaction efficiency with gluten proteins. In the dough stage, the modified soybean lecithin forms interfacial bridges between coarse grain fiber and gluten proteins, repairing the gas-holding network damaged by dietary fiber; in the quick-freezing stage, its polyhydroxy structure binds free water through hydrogen bonds, inhibiting ice crystal coarsening and preventing the raw dough from cracking; in the frying stage, the stable interfacial film effectively reduces oil penetration, ensuring a crisp outer shell and uniform internal pores in the finished product. When the modified soybean lecithin is compounded with mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, the product exhibits significant improvements in frozen storage stability, frying leavening, and moisture retention.

[0019] The aluminum-free and alum-free fluffy quick-frozen dough for fried dough sticks described in this invention exhibits excellent performance in terms of specific volume, appearance, color, aroma, ready-to-eat taste, taste after 30 minutes, and texture, thus solving the technical problem of poor processing performance of quick-frozen dough for fried dough sticks after the addition of coarse grains. Detailed Implementation

[0020] This invention provides an aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo, comprising the following raw materials in parts by weight: 65-75 parts wheat flour, 25-35 parts coarse grain flour, 6-10 parts wheat gluten, 3-5 parts compound leavening agent, 0.2-0.4 parts modified soybean lecithin, 0.2-0.4 parts mono- and diglycerides of fatty acids, 0.2-0.4 parts diacetyl tartaric acid mono- and diglycerides, 1.5-2 parts hydroxypropyl methylcellulose, 2-2.5 parts salt, 1.5-2 parts white sugar, 5-8 parts oil, and 55-65 parts water; the compound leavening agent comprises two or more of citric acid, sodium bicarbonate, glucono-δ-lactone, and calcium dihydrogen phosphate.

[0021] In this invention, the wheat flour is preferably composed of high-gluten flour and medium-gluten flour in a weight ratio of (5-7):(3-5), more preferably 6:4; the coarse grain flour preferably includes at least one of corn flour, oat flour, and buckwheat flour.

[0022] In this invention, the preferred method for preparing the modified soybean lecithin includes: mixing soybean lecithin with water, adding phospholipase A2 for ultrasonic enzymatic hydrolysis, inactivating the enzyme, adding caprylic acid and lipase for transesterification, filtering, subjecting the filtrate to high-pressure microfluidic treatment, and drying to obtain the modified soybean lecithin; the preferred amount of phospholipase A2 added is 200-250 U / g soybean lecithin, more preferably 230 U / g soybean lecithin; the preferred amount of lipase added is 180-220 U / g soybean lecithin, more preferably 200 U / g soybean lecithin; the preferred temperature for ultrasonic enzymatic hydrolysis is 55-60℃, more preferably 58℃, the preferred pH value is 5.8-6.2, more preferably 6, and the preferred power is 250-350 ppm. The preferred power is 0W, more preferably 300W; the preferred frequency is 25-30kHz, more preferably 28kHz; the preferred time is 2.5-3.5h, more preferably 3h; the preferred mass ratio of soybean lecithin to caprylic acid is 1:(6-8), more preferably 1:7; the preferred temperature for transesterification is 50-60℃, more preferably 55℃; the preferred stirring speed is 80-120rpm, more preferably 100rpm; the preferred time is 10-12h, more preferably 11h; the preferred pressure for high-pressure microjet treatment is 90-110MPa, more preferably 100MPa; the preferred temperature is 40-50℃, more preferably 45℃; the preferred number of treatments is 3-5 times, more preferably 4 times.

[0023] During the preparation process, phospholipase A2 can specifically hydrolyze acyl groups to generate lysophospholipids, enhancing hydrophilicity and interfacial activity. Ultrasonic assistance can improve the uniformity of enzymatic hydrolysis. Octyl ester exchange can introduce medium-chain fatty acids, regulate hydrophobic segments, optimize the hydrophilic-lipophilic balance, and improve the stability of the interfacial film. High-pressure microfluidic treatment can increase the specific surface area, improve the dispersibility in the aqueous phase, and enhance the interaction efficiency with gluten proteins. Modified soybean lecithin has dual functions of emulsification and stabilization and antifreeze quality improvement in quick-frozen fried dough stick embryos. Targeting the damage to the gluten network caused by the high dietary fiber in whole grain flour, it can form an interfacial bridge between fiber and gluten proteins, repairing the gas retention of the dough. During the quick-freezing stage, it inhibits ice crystal coarsening by binding free water through hydrogen bonds, preventing the embryo from cracking. During frying, the stable interfacial film can effectively reduce oil penetration, ensuring a crispy outer shell and uniform internal pores, while alleviating the problems of crumb and rough texture caused by the addition of whole grains.

[0024] The modified soybean lecithin of this invention, combined with mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, forms a synergistic system that strengthens the skeletal structure, prevents retrogradation, and locks in water and oil. Diacetyl tartaric acid mono- and diglycerides preferentially bind to gluten proteins, strengthening disulfide bond cross-linking, improving the disruption of the gluten network by coarse grain fibers, and giving the dough sufficient gas-holding capacity. Mono- and diglycerides of fatty acids form helical inclusion complexes with amylose, inhibiting starch recrystallization, while simultaneously adsorbing onto the surface of starch granules, delaying the retrogradation process of amylopectin, and stabilizing the small pores formed by leavening agents, reducing starch hardening after cooling. The modified soybean lecithin, with its enhanced hydrophilic end, promotes the fine and uniform dispersion of oils and, through its polyhydroxy structure, binds free water to form a flexible water-locking film. Simultaneously, the dense interfacial film reduces oil leakage during frying, decreases water evaporation channels, inhibits ice crystal migration, and improves frozen storage stability. During the frying process, the mono- and diglycerides of diacetyl tartaric acid ensure that the gluten skeleton expands fully. The mono- and diglycerides of fatty acids and modified soybean lecithin work together to reduce the surface tension of the oil and form a dense oil-blocking layer, resulting in a crispy outer shell and uniform internal pores after frying. Furthermore, it alleviates the hardening problem caused by the addition of coarse grains after the fried dough sticks have cooled down.

[0025] In this invention, the oil preferably includes at least one of shortening, sunflower seed oil, and palm oil; the water preferably includes ice water at 0-4°C and boiling water.

[0026] This invention also provides a method for preparing the above-mentioned aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo, comprising: boiling 33-36 parts by weight of water and mixing it with coarse grain flour, adding mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, letting it stand, cooling, adding wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and remaining water to form a dough, letting it stand and relax, kneading, vacuum pre-cooling, pressing, cutting into strips, stacking and shaping, and gradient quick-freezing to obtain the aluminum-free and alum-free fluffy quick-frozen fried dough stick embryo; the gradient quick-freezing method comprises: pre-freezing at -15~-10℃ for 25-35 minutes, and then freezing at -35~-40℃ to the center temperature of the embryo at -18℃.

[0027] During the preparation process, vacuum precooling cools the green embryo, effectively inhibiting excessive gas production by the composite leavening agent before quick-freezing and preventing excessive expansion or collapse of the microporous structure inside the green embryo before freezing. At the same time, the vacuum environment can reduce surface adhesion and prevent the green embryos from sticking together during subsequent freezing. The precooling section allows the surface of the green embryo to be quickly shaped, and the ultra-low temperature ice crystal formation section promotes the distribution of small and uniform ice crystals. Then, the center temperature is lowered to below -18℃ to fix the formed microporous structure.

[0028] The soybean phospholipids are from Henan Qingjia Trading Co., Ltd., product number QJ60413187; the phospholipase A2 activity is 200U / g, from Shanghai Yuanye Biotechnology Co., Ltd.; the lipase activity is 50000U / g, from Shandong Longket Enzyme Preparation Co., Ltd.

[0029] Example 1 (1) Preparation of modified soybean phospholipids Soybean lecithin and water were mixed at a mass ratio of 1:3, and phospholipase A2 (230 U / g soybean lecithin) was added. The mixture was enzymatically hydrolyzed by sonication at 58℃, pH 6.0, power 300W, and frequency 28kHz for 3 hours to inactivate the enzyme. Caprylic acid (soybean lecithin to caprylic acid mass ratio 1:7) and lipase (200 U / g soybean lecithin) were added, and the mixture was subjected to transesterification at 55℃ and 100 rpm for 11 hours. The mixture was filtered through a 20 kDa ultrafiltration membrane, and the filtrate was subjected to high-pressure microfluidic treatment at 100 MPa and 45℃ four times. The mixture was then concentrated and dried to constant weight to obtain modified soybean lecithin.

[0030] (2) Weighing Wheat flour is composed of high-gluten flour and medium-gluten flour in a weight ratio of 6:4; Whole grain flour is composed of corn flour and oat flour in a 1:1 weight ratio; The compound leavening agent is composed of citric acid, sodium bicarbonate, and glucono-δ-lactone in a mass ratio of 1:2:1. Accurately weigh the following ingredients by weight: 70 parts wheat flour, 30 parts coarse grain flour, 8 parts wheat gluten, 4 parts compound leavening agent, 0.3 parts modified soybean lecithin, 0.3 parts mono- and diglycerides of fatty acids, 0.3 parts diacetyl tartaric acid mono- and diglycerides, 1.8 parts hydroxypropyl methylcellulose, 2.2 parts salt, 1.8 parts white sugar, 6.5 parts oil, and 60 parts water.

[0031] (3) Preparation of quick-frozen fried dough stick embryos Boil 34 parts water and mix with whole grain flour. Add mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides. Let stand for 15 minutes and then cool to 20°C. Add wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and the remaining water (2°C ice water). Stir at 80 rpm for 20 minutes to form a dough. Cover with plastic wrap and let rest for 20 minutes. Knead to remove air and pre-cool under vacuum at -2°C for 20 minutes. Press the dough into sheets (thickness 8±2mm, length 18±2cm, width 2.5±0.3cm), brush with water lines, pre-freeze at -12°C for 30 minutes, and then freeze at -38°C until the center temperature of the dough reaches -18°C to obtain quick-frozen fried dough stick dough.

[0032] Example 2 (1) Preparation of modified soybean phospholipids Soybean lecithin and water were mixed at a mass ratio of 1:2, and phospholipase A2 (200 U / g soybean lecithin) was added. The mixture was ultrasonically hydrolyzed for 3.5 h at 55℃, pH 5.8, power 250 W, and frequency 25 kHz to inactivate the enzyme. Caprylic acid (soybean lecithin to caprylic acid mass ratio 1:6) and lipase (180 U / g soybean lecithin) were added, and the mixture was transesterified at 50℃ and 80 rpm for 12 h. The mixture was filtered through a 10 kDa ultrafiltration membrane, and the filtrate was subjected to high-pressure microfluidic treatment five times at 90 MPa and 40℃. The mixture was then concentrated and dried to constant weight to obtain modified soybean lecithin.

[0033] (2) Weighing Wheat flour is composed of high-gluten flour and medium-gluten flour in a weight ratio of 5:5; The whole grain flour is buckwheat flour; The compound leavening agent is composed of citric acid, sodium bicarbonate, and glucono-δ-lactone in a mass ratio of 1:1.5:0.8. Accurately weigh the following ingredients by weight: 65 parts wheat flour, 35 parts coarse grain flour, 10 parts wheat gluten, 5 parts compound leavening agent, 0.2 parts modified soybean lecithin, 0.2 parts mono- and diglycerides of fatty acids, 0.4 parts diacetyl tartaric acid mono- and diglycerides, 2 parts hydroxypropyl methylcellulose, 2.5 parts salt, 1.5 parts white sugar, 8 parts oil, and 65 parts water.

[0034] (3) Preparation of quick-frozen fried dough stick embryos Boil 36 parts water and mix with whole grain flour. Add mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides. Let stand for 12 minutes and then cool to 17°C. Add wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and the remaining water (0°C ice water). Stir at 50 rpm for 25 minutes to form a dough. Cover and let rest for 25 minutes. Knead to remove air and pre-cool under vacuum at -1°C for 18 minutes. Press the dough into sheets (thickness 8±2mm, length 18±2cm, width 2.5±0.3cm), brush with water lines, pre-freeze at -10°C for 35 minutes, and then freeze at -35°C until the center temperature of the dough reaches -18°C to obtain quick-frozen fried dough stick dough.

[0035] Example 3 (1) Preparation of modified soybean phospholipids Soybean lecithin and water were mixed at a mass ratio of 1:4, and phospholipase A2 (250 U / g soybean lecithin) was added. The mixture was enzymatically hydrolyzed by sonication at 60℃, pH 6.2, power 350W, and frequency 30kHz for 2.5 hours to inactivate the enzyme. Caprylic acid (soybean lecithin to caprylic acid mass ratio 1:8) and lipase (220 U / g soybean lecithin) were added, and transesterification was performed at 60℃ and 120 rpm for 10 hours. The mixture was filtered through a 30 kDa ultrafiltration membrane, and the filtrate was subjected to high-pressure microfluidic treatment three times at 110 MPa and 50℃. The mixture was then concentrated and dried to constant weight to obtain modified soybean lecithin.

[0036] (2) Weighing Wheat flour is composed of high-gluten flour and medium-gluten flour in a weight ratio of 7:3; Whole grain flour is oat flour; The compound leavening agent is composed of citric acid, sodium bicarbonate, and glucono-δ-lactone in a mass ratio of 1:2.2:1.2. Accurately weigh the following ingredients by weight: 75 parts wheat flour, 25 parts coarse grain flour, 6 parts wheat gluten, 3 parts compound leavening agent, 0.4 parts modified soybean lecithin, 0.4 parts mono- and diglycerides of fatty acids, 0.2 parts diacetyl tartaric acid mono- and diglycerides, 1.5 parts hydroxypropyl methylcellulose, 2 parts salt, 2 parts white sugar, 5 parts oil, and 55 parts water.

[0037] (3) Preparation of quick-frozen fried dough stick embryos Boil 33 parts water and mix with whole grain flour. Add mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides. Let stand for 17 minutes and then cool to 22°C. Add wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and the remaining water (4°C ice water). Stir at 100 rpm for 18 minutes to form a dough. Cover with plastic wrap and let rest for 18 minutes. Knead to remove air and pre-cool under vacuum at -4°C for 17 minutes. Press the dough into sheets (thickness 8±2mm, length 18±2cm, width 2.5±0.3cm), brush with water lines, pre-freeze at -15°C for 25 minutes, and then freeze at -40°C until the center temperature of the dough reaches -18°C to obtain quick-frozen fried dough stick dough.

[0038] Comparative Example 1 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.9 parts of modified soybean lecithin", while the total weight parts remain unchanged.

[0039] Comparative Example 2 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.9 parts of mono- and diglycerides of fatty acids", while the total weight parts remain unchanged.

[0040] Comparative Example 3 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.9 parts of diacetyl tartaric acid mono- and diglycerides", while the total weight parts remain unchanged.

[0041] Comparative Example 4 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.45 parts of mono- and diglycerides of fatty acids and 0.45 parts of diacetyl tartaric acid mono- and diglycerides", while the total weight parts remain unchanged.

[0042] Comparative Example 5 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.45 parts of modified soybean lecithin and 0.45 parts of diacetyl tartaric acid mono- and diglycerides", while the total weight parts remain unchanged.

[0043] Comparative Example 6 The difference from Example 1 is that "0.3 parts of modified soybean lecithin, 0.3 parts of mono- and diglycerides of fatty acids, and 0.3 parts of diacetyl tartaric acid mono- and diglycerides" are replaced with "0.45 parts of modified soybean lecithin and 0.45 parts of mono- and diglycerides of fatty acids", while the total weight parts remain unchanged.

[0044] Comparative Example 7 The difference from Example 1 is that the preparation method of modified soybean lecithin in step (1) is as follows: soybean lecithin and water are mixed at a mass ratio of 1:3, phospholipase A2 (addition amount 230U / g soybean lecithin) is added, and the mixture is enzymatically hydrolyzed by ultrasound at 58℃, pH 6.0, power 300W, and frequency 28kHz for 3 hours to inactivate the enzyme. The mixture is then filtered with a 20kDa ultrafiltration membrane, and the filtrate is treated with high pressure microfluidic jet at 100MPa and 45℃ 4 times. The filtrate is then concentrated and dried to constant weight to obtain modified soybean lecithin.

[0045] Comparative Example 8 The difference from Example 1 is that the preparation method of modified soybean lecithin in step (1) is as follows: soybean lecithin and water are mixed at a mass ratio of 1:3, octanoic acid (mass ratio of soybean lecithin to octanoic acid is 1:7) and lipase (addition amount 200U / g soybean lecithin) are added, and the mixture is subjected to ester exchange at 55℃ and 100rpm for 11h. The mixture is then filtered with a 20kDa ultrafiltration membrane, and the filtrate is subjected to high pressure microfluidic treatment at 100MPa and 45℃ 4 times. The mixture is then concentrated and dried to constant weight to obtain modified soybean lecithin.

[0046] Comparative Example 9 The difference from Example 1 is that the preparation method of quick-frozen fried dough stick embryo in step (3) is as follows: wheat flour, coarse grain flour, gluten powder, compound leavening agent, modified soybean lecithin, mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, hydroxypropyl methylcellulose, salt, white sugar, oil and water (2°C ice water) are stirred at 80 rpm for 20 min to form a dough, covered with film and allowed to rest for 20 min, kneaded to remove air, vacuum pre-cooled at -2°C for 20 min, the dough is pressed into a sheet (thickness 8±2 mm, length 18±2 cm, width 2.5±0.3 cm), brushed with water lines, pre-frozen at -12°C for 30 min, and then frozen at -38°C to the center temperature of the embryo at -18°C to obtain quick-frozen fried dough stick embryo.

[0047] Comparative Example 10 The difference from Example 1 is that the preparation method of quick-frozen fried dough stick embryo in step (3) is as follows: Boil 34 parts of water, mix with coarse grain flour, add mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides, let stand for 15 minutes and then cool to 20°C, then add wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and the remaining water (2°C ice water), stir at 80 rpm for 20 minutes to form dough, cover with film and let stand for 20 minutes to relax, knead to remove air, vacuum pre-cool at -2°C for 20 minutes, press the dough into a sheet (thickness 8±2mm, length 18±2cm, width 2.5±0.3cm), brush with water lines, freeze at -38°C to the center temperature of the embryo at -18°C to obtain quick-frozen fried dough stick embryo.

[0048] Application Detection 1 The quick-frozen dough sticks prepared in Example 1 and Comparative Examples 1-10 were fried, and their specific volume was measured.

[0049] The frying method is as follows: when the oil temperature is 185±5℃, put in the frozen dough sticks, and when they float to the surface, turn them over with chopsticks and fry for 150±20 seconds, then remove them.

[0050] The specific volume determination method is the rapeseed displacement method: Weigh the fried dough sticks and record the mass m. Place them in a graduated cylinder, fill the graduated cylinder with rapeseed oil and shake it firmly. Record the volume V1 of the fried dough sticks and rapeseed oil. Remove the fried dough sticks and record the volume V2 of the rapeseed oil. Calculate the specific volume. Specific volume (mL / g) = (V1-V2) / m.

[0051] Five parallel tests were set up for each sample, and the average of the five parallel tests was taken as the result.

[0052] The specific results of the average specific volume of the quick-frozen fried dough stick embryos of the control, Example 1, and Comparative Examples 1-10 are shown in Table 1.

[0053] Table 1. Specific volume results of the samples Example 1 4.20 Comparative Example 1 3.17 Comparative Example 2 2.93 Comparative Example 3 2.86 Comparative Example 4 3.34 Comparative Example 5 3.49 Comparative Example 6 3.21 Comparative Example 7 3.58 Comparative Example 8 3.72 Comparative Example 9 2.47 Comparative Example 10 2.65 Table 1 shows that the specific volume of Example 1 is as high as 4.20 mL / g, which is better than all comparative examples, indicating that the technical solution of Example 1 can make the fried dough sticks have excellent fluffy effect.

[0054] The specific volumes of Comparative Examples 1-6 were all lower than those of Example 1, demonstrating the necessity of a specific ternary emulsifier blend (modified soybean lecithin, mono- and diglycerides of fatty acids, and diacetyl tartaric acid mono- and diglycerides). Comparative Example 1 used only modified soybean lecithin; the lack of diacetyl tartaric acid mono- and diglycerides to strengthen the disulfide bonds in gluten resulted in insufficient gas-holding capacity of the dough, exacerbating the disruptive effect of coarse grain fibers on the gluten network, leading to gas escape and limited expansion during frying. Comparative Examples 2 and 3 used mono- and diglycerides of fatty acids or diacetyl tartaric acid mono- and diglycerides alone, respectively, resulting in decreased specific volumes. This indicates that a single emulsifier may cause gluten network collapse, pore merging, or rupture, leading to smaller volumes. Although the specific volumes of Comparative Examples 4-6 showed some recovery, they were still significantly lower than those of Example 1, indicating that the three emulsifiers are complementary and indispensable. Modified soybean lecithin binds free water at its hydrophilic end, inhibiting ice crystal coarsening; mono- and diglycerides of fatty acids delay starch retrogradation and fix pores; and diacetyl tartaric acid mono- and diglycerides enhance gluten elasticity. Together, these three components construct a stable air chamber wall, thereby increasing the specific volume of fried dough sticks.

[0055] In the preparation of modified soybean lecithin, Comparative Example 7 (without caprylate exchange) and Comparative Example 8 (without phospholipase hydrolysis) both showed lower specific volumes than Example 1. Phospholipase A2 hydrolysis introduced hydrophilic lysophospholipids, enhancing interfacial activity; caprylate exchange introduced medium-chain fatty acids, optimizing the hydrophilic-lipophilic balance, making the modified soybean lecithin more likely to form bridges between coarse grain fiber and gluten protein, repairing the gas-holding network damaged by dietary fiber. Unmodified lecithin exhibited reduced dispersibility and interaction efficiency, failing to effectively inhibit ice crystal migration, resulting in damaged pore structure during frozen storage and decreased post-frying leavening.

[0056] Comparative Example 9: The whole grain flour was not pregelatinized with boiling water, resulting in a lower specific volume. Pregelatinization with boiling water partially gelatinizes the starch in the whole grains, encapsulating the dietary fiber and reducing its intense competition for water. It also softens the grain particles, reducing physical disruption of the gluten network. Ungelatinized whole grain flour absorbs water unevenly, has a discontinuous gluten network, and extremely poor gas retention, preventing it from fully expanding during frying. Comparative Example 10: Without gradient freezing, the specific volume was lower than in Example 1. The -12℃ pre-freezing stage in gradient freezing rapidly shapes the surface of the raw dough and initially fixes the internal micropores. Subsequent deep freezing at -38℃ forms fine, uniform ice crystals, avoiding the large ice crystals that pierce the pore walls caused by direct flash freezing. Without gradient freezing, the already formed loose microstructure is directly destroyed, leading to collapse and shrinkage after frying.

[0057] Application Detection 2 Sensory evaluations were conducted on the appearance, color, aroma, taste, and texture of the quick-frozen dough sticks from Examples 1 and Comparative Examples 1-10 after frying.

[0058] Twenty professional assessors with sensory evaluation experience in Chinese pastry (10 males and 10 females, aged 25-40) were selected. All assessors had no olfactory or gustatory disorders and had no history of smoking, drinking alcohol, or consuming spicy foods within 24 hours prior to the experiment. They underwent unified training on the scoring criteria and pre-evaluation practice before the experiment to ensure consistency in scoring.

[0059] For the frying method of the sample, refer to Application Testing 1.

[0060] All samples were immediately removed from the oil after frying and drained. They were then placed in a constant temperature and humidity environment for 5 minutes, followed by 30 minutes, and tasted twice (to assess whether the fried dough sticks hardened after being left to stand). Samples were randomly numbered with a three-digit code and sent to the evaluation room immediately after preparation. Evaluators used a blind sample method to avoid subjective bias. Five parallel samples were set up for each sample, and the evaluation result was the average of the five parallel samples. The total score was the sum of the average results of all indicators.

[0061] The sensory evaluation criteria are as follows: Appearance: 16-20 points: The dough sticks are uniform in thickness, straight and full, without bending, collapsing, breaking or crumbling; both ends are sealed intact, without cracks or large holes exposed; after frying, they expand fully, have a regular shape, and there is no separation at the joints of the raw dough. 11-15 points: Overall, it is relatively full, slightly curved, with some small cracks and minor chipping; the expansion is acceptable, with no large-area cracks or obvious collapse. 6-10 points: Uneven shape, obvious bending, local collapse, multiple small cracks, and a lot of chipping; insufficient expansion, and smaller size; 0-5 points: Severe collapse, significant shrinkage, multiple fractures, large-area cracking and splintering; the embryo separates into layers and has a deformed and incomplete shape.

[0062] Color: 16-20 points: The whole grain is golden and uniform, with a natural luster and no charred spots or whitish areas; the color is consistent and the coarse grains have a soft and beautiful color. 11-15 points: The main color is golden yellow, with slight light white or light yellow in some areas, and only a few very small focal points. The overall color is harmonious. 6-10 points: The color is light and whitish, or there are large areas of burnt yellow; there are many obvious burnt spots, and the luster is dull; 0-5 points: Large areas are charred and carbonized, or the whole is pale white with a mottled and messy color, resulting in a poor appearance.

[0063] aroma: 12-15 points: The aroma of wheat is fresh and the fragrance of whole grains is rich and harmonious, with no off-odors; there is no rancid smell of oil, no alkaline smell, no pungent chemical smell, and the fried aroma is pure; 8-11 points: The aroma of grains is light and simple, with no unpleasant odors, and the slight smell of fried oil smoke is not overpowering; 4-7 points: Weak grain aroma, strong oily smell, slight alkaline smell, slight rancid smell; 0-3 points: Distinct rancid oil smell, pungent alkaline smell, fermented odor, no grain aroma.

[0064] Taste (taste after 5 minutes and taste after 30 minutes): Immediate taste: 12-15 points: The outer skin is crispy and thin, while the inside is soft and porous; the whole grains are fine and have no coarse texture, and they do not irritate the throat; the salty and sweet taste is moderate, with no astringent or bitter taste from aluminum alum, and it is not greasy and has a light chewing experience. 8-11 points: The outer skin is hard or slightly soft, and the inside is soft; the whole grains are slightly rough, with a small amount of residue, the taste is normal, and it is slightly oily. 4-7 points: The outer skin is hard and tough, and the inside is dense and dry; it has a strong coarse grain texture, is harsh on the throat, and is greasy and oily, with an unbalanced flavor. 0-3 points: The outer skin is dry, hard, and difficult to chew; the inside is sticky and dense; the coarse grains are harsh on the throat, have a strong bitter taste, and are extremely greasy.

[0065] Taste after 30 minutes: 12-15 points: The outer skin remains crispy, only slightly softened, and the inside is still fluffy; there is no obvious hardening or dryness, the coarse grains do not have a harsh feeling in the throat, and they do not clump together; 8-11 points: The outer skin is moderately softened, the inner layer is slightly hardened, and the whole thing is still chewable without serious lumps or roughness; 4-7 points: The outer skin is severely tough and hard, the inside is dry and compacted, the coarse grains are rough and irritating to the throat, and it is difficult to chew; 0-3 points: Completely hardened and compacted, impossible to chew, leaves a mouthful of dry residue, feels dry and astringent, and has lost its edible texture.

[0066] Organizational structure: 12-15 points: The internal pores are fine, uniform, and intact, with consistent size; there are no large voids or solid hard cores; the gluten network is continuous, the coarse grain fibers are evenly distributed, and there is no clumping or splitting of the gluten. 8-11 points: The pores are relatively uniform, with a few larger pores and some areas that are slightly solid; a small amount of coarse grains are clustered together, and the gluten network is slightly broken. 4-7 points: The pores vary greatly in size, there are many large cavities, and many solid cores; coarse grains are gathered and cut the gluten, and the structure is loose; 0-3 points: The interior is dense and without air holes, with large solid pieces; the gluten is completely broken, layered and crumbling, and the texture is broken.

[0067] The sensory evaluation scores for each sample are shown in Table 2.

[0068] Table 2 Sensory evaluation scores for each sample (points) Example 1 19.5 18.9 14.6 14.2 13.7 14.0 94.9 Comparative Example 1 12.3 18.0 13.4 9.5 8.8 9.1 71.1 Comparative Example 2 10.6 17.7 14.0 8.7 7.4 8.3 66.7 Comparative Example 3 10.8 17.5 14.2 7.4 7.0 7.7 64.6 Comparative Example 4 13.2 17.2 13.8 10.3 9.1 10.9 74.5 Comparative Example 5 14.9 16.8 13.5 10.1 10.6 11.3 77.2 Comparative Example 6 11.4 18.3 13.7 8.9 8.5 9.6 70.4 Comparative Example 7 15.0 18.4 14.1 11.6 11.3 11.5 81.9 Comparative Example 8 16.7 17.1 13.6 11.8 11.4 12.2 82.8 Comparative Example 9 8.5 14.6 9.9 5.3 5.2 5.8 49.3 Comparative Example 10 9.1 15.7 13.3 6.6 5.7 6.4 56.8 Table 2 shows that Example 1 performed excellently in all aspects, with sensory scores higher than all comparative examples. This indicates that the invention's formula and process optimization not only improved the fluffiness but also comprehensively improved the quality of frozen whole grain fried dough sticks from multiple dimensions such as appearance, taste, and texture, overcoming the problems of traditional whole grain fried dough sticks such as collapsing, crumbling, and hardening.

[0069] In terms of appearance, both Comparative Examples 9 and 10 showed severe collapse, cracking, and crumbling. Pregelatinization softened and evenly dispersed the coarse grain fibers, while gradient freezing prevented freezing cracks caused by the coarsening of ice crystals. The combination of these two methods ensured the integrity of the raw embryo structure and its regular expansion after frying. In terms of color, Comparative Example 9 had a whitish, undercooked surface due to insufficient gelatinization of the coarse grains.

[0070] Regarding aroma, Comparative Example 9 had a strong raw grain flavor due to the lack of pregelatinization of the coarse grains, and uneven moisture release during frying easily resulted in a burnt taste. Comparative Examples 1-6 scored in the middle in terms of aroma. Although the change in the emulsifier combination did not directly produce off-flavors, the collapse of the fried dough sticks led to a high internal oil content and an increased risk of oil oxidation, which slightly affected the purity of the aroma.

[0071] In terms of taste, Example 1 scored 14.2 points for ready-to-eat taste and maintained a score of 13.7 points after 30 minutes, indicating that it was crispy on the outside and soft on the inside, with fine coarse grains and only slight hardening after cooling. This is because mono- and diglycerides of fatty acids inhibit starch retrogradation, modified soybean lecithin forms a flexible water-locking film, and diacetyl tartaric acid mono- and diglycerides strengthen the gluten skeleton; these three factors synergistically delay starch recrystallization and water migration. Comparative Example 2 shows that without diacetyl tartaric acid mono- and diglycerides and modified soybean lecithin, the gluten network strength is insufficient and water retention is poor, resulting in hardened fried dough sticks that become dry and tough after cooling. Comparative Example 9 has coarse grain particles that are rough and irritating to the throat, and the ungelatinized starch rapidly retrogrades during aging, leading to severe hardening. Comparative Example 10 was frozen without gradient, resulting in ice crystals damaging the tissue structure, severe moisture loss after frying, and a dry and hard texture.

[0072] In terms of structure, Example 1 exhibits fine and uniform pores, a complete honeycomb structure, and evenly dispersed coarse grain fibers. The changes in emulsifier composition in Comparative Examples 1-6 are all less pronounced than in Example 1, mainly due to uneven pore size, localized solid areas, or coarse grain aggregation that breaks the gluten. In Comparative Examples 2 and 3, the gluten network is fractured due to a lack of synergistic reinforcement, resulting in uneven air chamber wall thickness. After frying, many pores merge into large holes or collapse into a solid, hard core. Comparative Example 9, without a pre-gelatinization process for the coarse grains, has a dense interior without pores and severe gluten breakage; Comparative Example 10, lacking gradient freezing, results in ice crystal punctures, leading to a loose, layered structure.

[0073] From the overall score, the integrity of the ternary compound emulsifier has the greatest impact on quality; the dual modification of modified soybean phospholipids using two enzymes and transesterification is superior to single modification; pregelatinization of coarse grains and gradient quick-freezing are important factors in ensuring product stability. Example 1 achieved a comprehensive improvement in the sensory quality of coarse grain fried dough sticks through a technical solution of pregelatinization to protect gluten, emulsifier synergistic construction of air cells, and gradient quick-freezing to fix micropores.

[0074] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fluffy, quick-frozen fried dough stick dough without aluminum or alum, characterized in that, The raw materials include the following parts by weight: 65-75 parts wheat flour, 25-35 parts coarse grain flour, 6-10 parts wheat gluten, 3-5 parts compound leavening agent, 0.2-0.4 parts modified soybean lecithin, 0.2-0.4 parts mono- and diglycerides of fatty acids, 0.2-0.4 parts diacetyl tartaric acid mono- and diglycerides, 1.5-2 parts hydroxypropyl methylcellulose, 2-2.5 parts salt, 1.5-2 parts white sugar, 5-8 parts oil, and 55-65 parts water; the compound leavening agent includes two or more of citric acid, sodium bicarbonate, glucono-δ-lactone, and calcium dihydrogen phosphate.

2. The aluminum-free and alum-free fluffy quick-frozen fried dough stick preform according to claim 1, characterized in that, The wheat flour is composed of high-gluten flour and medium-gluten flour in a weight ratio of (5-7):(3-5).

3. The aluminum-free and alum-free fluffy quick-frozen fried dough stick prep according to claim 1, characterized in that, The whole grain flour includes at least one of corn flour, oat flour, and buckwheat flour.

4. The aluminum-free and alum-free fluffy quick-frozen fried dough stick prep according to claim 1, characterized in that, The method for preparing the modified soybean lecithin includes: mixing soybean lecithin with water, adding phospholipase A2 for ultrasonic enzymatic hydrolysis, inactivating the enzyme, adding caprylic acid and lipase for transesterification, filtering, subjecting the filtrate to high-pressure microfluidic treatment, and drying to obtain the modified soybean lecithin.

5. The aluminum-free and alum-free fluffy quick-frozen fried dough stick prep according to claim 4, characterized in that, The ultrasonic enzymatic hydrolysis is performed at a temperature of 55-60℃, a pH value of 5.8-6.2, a power of 250-350W, a frequency of 25-30kHz, and a time of 2.5-3.5h.

6. The aluminum-free and alum-free fluffy quick-frozen fried dough stick preform according to claim 4, characterized in that, The mass ratio of soybean lecithin to caprylic acid is 1:(6-8); the transesterification temperature is 50-60℃, the stirring rate is 80-120rpm, and the time is 10-12h.

7. The aluminum-free and alum-free fluffy quick-frozen fried dough stick prep according to claim 4, characterized in that, The high-pressure microjet treatment is performed at a pressure of 90-110 MPa, a temperature of 40-50°C, and 3-5 times.

8. The aluminum-free and alum-free fluffy quick-frozen fried dough stick preform according to claim 1, characterized in that, The oils include at least one of shortening, sunflower oil, and palm oil; the water includes ice water at 0-4°C and boiling water.

9. A method for preparing aluminum-free and alum-free fluffy quick-frozen fried dough sticks according to any one of claims 1-8, characterized in that, include: Boil 33-36 parts by weight of water and mix with coarse grain flour. Add mono- and diglycerides of fatty acids and diacetyl tartaric acid mono- and diglycerides. Let stand and cool. Add wheat flour, wheat gluten, compound leavening agent, modified soybean lecithin, hydroxypropyl methylcellulose, salt, white sugar, oil and the remaining water to form a dough. Let stand and relax, knead, vacuum pre-cool, press into sheets, cut into strips, stack into shapes, and quick-freeze in gradient to obtain aluminum-free and alum-free fluffy quick-frozen fried dough stick embryos.

10. The preparation method according to claim 9, characterized in that, The gradient quick-freezing method includes: pre-freezing at -15~-10℃ for 25-35 minutes, and then freezing at -35~-40℃ to the embryo center temperature of -18℃.