Preparation method of quick-frozen breaded dough with prolonged shelf life

Abstract

The application provides a preparation method of a long-shelf-life quick-frozen dough stick blank, and belongs to the technical field of food processing.The quick-frozen dough stick blank comprises high-gluten flour, modified waxy corn starch, a compound leavening agent, a composite enzyme, sodium lactate, sodium ascorbate, table salt, white granulated sugar, egg liquid, oil and ice water.The modified waxy corn starch is prepared through magnesium carbonate nucleation, low-temperature ultrasonic-assisted pullulanase enzymolysis and pulse-type heat pressing cycle treatment; and the composite enzyme is composed of xylanase and glucose oxidase.Through the modified waxy corn starch, the composite enzyme and the gradient quick-freezing process, the application significantly delays gluten weakening, ice crystal coarsening, starch aging and oil oxidation during frozen storage, so that the quick-frozen dough stick blank can still maintain excellent bulkiness, crispness and low oil absorption rate after being stored at-18 DEG C for three months, and has good quality stability.

Description

Technical Field

[0001] This invention relates to the field of food processing technology, specifically to a method for preparing quick-frozen fried dough stick embryos with extended shelf life. Background Technology

[0002] As a classic Chinese fried dough product, fried dough sticks suffer from high spoilage and labor costs when made and sold on-site. Frozen fried dough stick dough, however, has become a mainstream product for restaurant chains and supermarkets due to its suitability for standardized store operations and the elimination of the need for on-site kneading and proofing. However, current conventional frozen fried dough stick dough preparation processes suffer from significant shortcomings in frozen storage quality, resulting in generally short shelf lives and rapid quality deterioration during cold chain storage, hindering long-distance distribution and long-term inventory management.

[0003] Traditional recipes rely solely on a single leavening agent and ordinary wheat flour to construct the dough system, resulting in insufficient low-temperature stability of the gluten network. When the dough is frozen, the free water inside forms large ice crystals that continuously pierce the gluten network structure. After long-term frozen storage, the raw dough is prone to problems such as surface dehydration and shrinkage, cracking at the cross-section, and yellowing or browning. At the same time, the low-temperature environment accelerates starch aging and oil oxidation, leading to defects such as insufficient fluffiness, uneven hollow layers, collapse after frying, and rapid softening and hardening of the finished product after frying. It also has a high oil absorption rate and a significantly reduced taste.

[0004] Conventional quick-freezing processes typically employ rapid freezing at a single temperature without a gradient temperature control and shaping process. This results in a significant difference in the rate of ice crystal formation inside and outside the embryo, further exacerbating structural damage. Existing improvement methods often involve the addition of single enzymes or humectants, offering limited effects and failing to simultaneously achieve multiple benefits such as gluten strengthening, ice crystal control, slow-release gas production, and long-lasting moisture retention and antioxidant properties.

[0005] The lack of a compound system on the market that can synergistically improve gluten structure, inhibit freezing deterioration, and stabilize gas production performance during frying makes it impossible to meet the quality requirements of long shelf life and crispy, low oil absorption of finished products. This has become the core technical bottleneck for the large-scale, long-cycle circulation of frozen fried dough sticks. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing quick-frozen fried dough sticks with extended shelf life. The quick-frozen fried dough sticks prepared by this invention remain fluffy and crispy, with low oil absorption rate and stable sensory quality after being frozen for 3 months.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution: This invention provides a quick-frozen dough stick embryo with extended shelf life, comprising the following raw materials in parts by weight: 100 parts high-gluten flour, 5-10 parts modified waxy corn starch, 1.8-3.5 parts compound leavening agent, 0.001-0.002 parts compound enzyme, 0.18-0.22 parts sodium lactate, 0.03-0.1 parts sodium ascorbate, 1-2.2 parts salt, 0.8-1.8 parts white sugar, 3-8 parts egg liquid, 2-6 parts oil, and 48-62 parts ice water.

[0008] Preferably, the preparation method of the modified waxy corn starch includes: mixing waxy corn starch with water, adding magnesium carbonate, letting it stand, ultrasonic treatment, adding pullulanase for enzymatic hydrolysis, inactivating the enzyme, performing pulsed hot-pressing cycle treatment, and vacuum drying to obtain modified waxy corn starch.

[0009] More preferably, the mass ratio of the waxy corn starch, magnesium carbonate and water is 100:(0.25-0.35):(400-500).

[0010] More preferably, the ultrasonic treatment is performed at a temperature of 2-6°C, a power of 180-230W, and a time of 10-15 minutes.

[0011] More preferably, the amount of pullulanase added is 0.5-0.8% of the mass of waxy corn starch, the enzymatic hydrolysis temperature is 30-35℃, the pH value is 5-5.5, and the time is 20-30 min.

[0012] More preferably, the pulsed hot-pressing cycle treatment is performed at a temperature of 58-62℃ and a pressure of 0.08-0.12MPa, with pressure held for 5-10 minutes and then depressurized for 1.5-2.5 minutes, and the cycle is repeated 3-5 times.

[0013] Preferably, the compound leavening agent comprises at least one of glucono-δ-lactone, calcium dihydrogen phosphate, calcium carbonate, disodium dihydrogen pyrophosphate, and sodium bicarbonate; the oil comprises at least one of palm oil, soybean oil, and rapeseed oil.

[0014] Preferably, the complex enzyme is composed of xylanase and glucose oxidase in a mass ratio of (4-6):(2-4).

[0015] This invention also provides a method for preparing the above-mentioned extended shelf-life quick-frozen fried dough stick embryo, comprising: mixing high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar to obtain a premix; mixing ice water with sodium lactate and sodium ascorbate, then mixing with the premix, adding egg liquid and oil to form a dough, allowing it to rest and relax, kneading, vacuum precooling, pressing into sheets, cutting into strips, stacking into shapes, and gradient quick-freezing to obtain the extended shelf-life quick-frozen fried dough stick embryo.

[0016] Preferably, the gradient quick-freezing includes pre-freezing at -15~-10℃ for 25-35 minutes, and then freezing at -35~-40℃ to the embryo center temperature of -18℃.

[0017] The present invention has the following beneficial effects: This invention solves the quality deterioration problems of conventional quick-frozen fried dough sticks during frozen storage, such as gluten structure weakening, ice crystals coarse, starch retrogradation, oil oxidation and browning, and frying collapse and softening, by combining high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, sodium lactate, sodium ascorbate and other components with gradient quick-freezing process. It enables the product to maintain excellent edible quality after being frozen at -18℃ for 3 months, and significantly extends the shelf life.

[0018] This invention utilizes modified waxy corn starch, which undergoes magnesium carbonate nucleation, low-temperature ultrasonic-assisted pullulanase hydrolysis, and pulsed hot-pressing cycling to generate short-chain branched starch molecules and achieve ordered rearrangement, thus endowing it with excellent water-locking and antifreeze properties. When combined with high-gluten flour, the modified waxy corn starch strengthens the cross-linking network of gluten proteins through additional hydrogen bonding sites and binds free water with controllable water-holding capacity. Combined with the moisturizing effect of sodium lactate, this effectively inhibits the formation and growth of large ice crystals during frozen storage, preventing the piercing and irreversible damage to the gluten skeleton caused by freeze-thaw cycles. This solves the problems of surface dehydration and shrinkage, and surface cracking of raw dough. Simultaneously, the short-chain branched structure generated by enzymatic hydrolysis significantly reduces the recrystallization tendency of starch molecules. Combined with the antioxidant effect of sodium ascorbate, this continuously delays starch aging and oil oxidation during long-term frozen storage, making fried dough sticks less prone to rapid softening and hardening, maintaining a high degree of crispness, low oil absorption, and superior sensory quality.

[0019] This invention employs a complex enzyme system of xylanase and glucose oxidase in a specific ratio. Xylanase moderately hydrolyzes insoluble arabinoxylan to release bound water, increasing the extensibility of the gluten network. In conjunction with glucose oxidase, it catalyzes the oxidation of sulfhydryl groups in gluten proteins to form disulfide bonds, strengthening the rigidity and toughness of the gluten skeleton. The combination of the two improves the dough's handling tolerance and frozen storage stability, enabling the product to maintain a uniform and delicate texture even after being frozen for 3 months.

[0020] The compound leavening agent components of this invention slowly release gas during frozen storage, avoiding the problem of conventional leavening agents reacting and becoming ineffective during long-term storage. Combined with the slow-release gas-generating characteristics of modified starch during frying and heating, it ensures that the raw embryo still has uniform hollow layers and full expansion volume after 3 months of frozen storage.

[0021] This invention employs a gradient quick-freezing process of pre-freezing followed by deep freezing, which effectively reduces the difference in the rate of ice crystal formation between the inside and outside of the embryo, avoids tissue tearing and stress cracking caused by excessive temperature difference, and inhibits changes in the physicochemical properties and sensory quality of the product during cryopreservation. Detailed Implementation

[0022] This invention provides a quick-frozen dough stick embryo with extended shelf life, comprising the following raw materials in parts by weight: 100 parts high-gluten flour, 5-10 parts modified waxy corn starch, 1.8-3.5 parts compound leavening agent, 0.001-0.002 parts compound enzyme, 0.18-0.22 parts sodium lactate, 0.03-0.1 parts sodium ascorbate, 1-2.2 parts salt, 0.8-1.8 parts white sugar, 3-8 parts egg liquid, 2-6 parts oil, and 48-62 parts ice water.

[0023] The high-gluten flour described in this invention provides gluten proteins (glutenin and prolamins) to form a continuous three-dimensional network structure, which can improve the dough's gas retention and elasticity. The high-gluten flour has sufficient gluten content, which can resist the mechanical damage of ice crystals during freezing and maintain the integrity of the raw dough. During frying, it can effectively encapsulate the gas released by the leavening agent, forming a uniform hollow structure and improving the fluffiness of the fried dough sticks.

[0024] In this invention, the preferred method for preparing the modified waxy corn starch includes: mixing waxy corn starch with water, adding magnesium carbonate, allowing it to stand, ultrasonically treating it, adding pullulanase for enzymatic hydrolysis, inactivating the enzyme, performing pulsed hot-pressing cycling treatment, and vacuum drying to obtain the modified waxy corn starch; the preferred mass ratio of waxy corn starch, magnesium carbonate, and water is 100:(0.25-0.35):(400-500), more preferably 100:0.3:450; the preferred ultrasonic treatment temperature is 2-6℃, more preferably 4℃, the preferred power is 180-230W, more preferably 200W, and the preferred time is 10-15min, more preferably 12min; The preferred amount of pullulanase added is 0.5-0.8% of the mass of waxy corn starch, more preferably 0.7%. The preferred temperature for enzymatic hydrolysis is 30-35℃, more preferably 32℃. The preferred pH value is 5-5.5, more preferably 5.2. The preferred time is 20-30 min, more preferably 25 min. The preferred temperature for pulsed hot-pressing cycle treatment is 58-62℃, more preferably 60℃. The preferred pressure is 0.08-0.12 MPa, more preferably 0.1 MPa. The preferred pressure is maintained for 5-10 min followed by depressurization for 1.5-2.5 min, more preferably maintained for 8 min followed by depressurization for 2 min. The preferred number of cycles is 3-5, more preferably 4.

[0025] During the preparation process, magnesium carbonate acts as a nucleation site, uniformly dispersed among starch granules, inhibiting random starch agglomeration and ensuring uniform enzymatic hydrolysis and hot-pressing modification reactions. Low-temperature ultrasound only loosens the surface crystalline structure of starch without destroying the intact starch granule skeleton, increasing the active sites for subsequent enzymatic hydrolysis and preventing premature starch gelatinization. Pullulanase hydrolysis generates short-chain branched starch molecules, which reduces starch recrystallization and provides more hydrogen bond sites for subsequent cross-linking, laying the foundation for improving the gluten network structure. At temperatures below complete gelatinization, pulsed pressure causes the short-chain starch molecules to rearrange in an orderly manner, achieving the dual properties of water retention and freeze protection, and controllable gas production.

[0026] In this invention, the compound leavening agent comprises at least one of glucono-δ-lactone, calcium dihydrogen phosphate, calcium carbonate, disodium dihydrogen pyrophosphate, and sodium bicarbonate; the oil preferably comprises at least one of palm oil, soybean oil, and rapeseed oil.

[0027] In this invention, the complex enzyme is preferably composed of xylanase and glucose oxidase in a mass ratio of (4-6):(2-4), and more preferably in a mass ratio of 5:3.

[0028] This invention addresses the problem of conventional products collapsing, softening, and deteriorating in taste after 3 months of frozen storage by using a compound system that strengthens gluten, controls ice crystals, slows gas release, and provides long-lasting water retention and antioxidant protection.

[0029] This invention uses high-gluten flour as a base, combined with additional hydrogen bonding sites provided by modified waxy corn starch, and oxidative modification of gluten proteins by complex enzymes (xylanase and glucose oxidase), which significantly enhances the toughness and stability of the gluten network. Modified waxy corn starch, after being treated with pulsed hot-pressing cycles, improves its water-locking and antifreeze properties. Combined with the moisturizing effect of sodium lactate, it effectively binds free water, inhibits the formation and growth of large ice crystals during freezing, and prevents ice crystals from piercing the gluten structure, thus preventing the surface of the raw dough from drying out and cracking. Modified waxy corn starch, after being pulsed at a temperature below gelatinization temperature, causes short-chain starch molecules to rearrange in an orderly manner. Combined with compound leavening agents, it slowly releases gas during frying, ensuring that the raw dough still has excellent fluffiness and uniform hollow layers after long-term frozen storage. The short-chain branched molecules generated by enzymatic hydrolysis in modified waxy corn starch effectively reduce the tendency of starch recrystallization (aging). Combined with the antioxidant effect of sodium ascorbate, it makes the fried dough sticks less likely to soften and harden quickly after frying, and significantly reduces the oil absorption rate, resulting in a crispier texture. Furthermore, this invention employs a gradient freezing method of pre-freezing followed by deep freezing, which reduces the difference in the rate of ice crystal formation inside and outside the raw dough, avoiding tissue tearing due to excessive temperature differences. This allows the raw dough to withstand repeated temperature fluctuations during cold chain transportation, preventing rapid deterioration of physicochemical properties and sensory quality due to temperature changes. The compounded components of this invention work together to achieve gluten stability, ice crystal refinement, color retention, and stable gas production during frying, thus balancing long shelf life and high sensory quality.

[0030] This invention also provides a method for preparing the above-mentioned extended shelf-life quick-frozen fried dough stick embryo, comprising: mixing high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar to obtain a premix; mixing ice water with sodium lactate and sodium ascorbate, then mixing with the premix, adding egg liquid and oil to form a dough, allowing it to rest and relax, kneading, vacuum precooling, pressing into sheets, cutting into strips, stacking into shapes, and gradient quick-freezing to obtain the extended shelf-life quick-frozen fried dough stick embryo; the gradient quick-freezing preferably includes pre-freezing at -15~-10℃ for 25-35 minutes, and then freezing at -35~-40℃ to the center temperature of the embryo at -18℃.

[0031] The quick-frozen dough sticks of this invention do not require thawing; they can be directly deep-fried after being removed from the oil. The processing method of the quick-frozen dough sticks of this invention is as follows: when the oil temperature is 185±5℃, put the quick-frozen dough sticks into the oil, and when they float to the surface, turn them over with chopsticks and deep-fry for 180±20 seconds. Then, remove them to obtain golden and crispy dough sticks.

[0032] The waxy corn starch was sourced from Gansu Kunlun Biochemical Co., Ltd.; pullulanase, with an enzyme activity of 2000 U / g, was sourced from Zhejiang Zhongmu Pharmaceutical Co., Ltd.; xylanase, with an enzyme activity of 10,000 U / g, was sourced from Guangzhou Jinmanyuan Biotechnology Co., Ltd.; and glucose oxidase, with an enzyme activity of 10,000 U / g, was sourced from Henan Anrui Biotechnology Co., Ltd.

[0033] Example 1 (1) Preparation of modified waxy corn starch Waxy corn starch and water were mixed at a mass ratio of 100:450. 0.3% (by weight of the waxy corn starch) of magnesium carbonate was added. After standing for 30 minutes, the mixture was ultrasonically treated for 12 minutes at 4℃ and 200W. Then, 0.7% (by weight of the waxy corn starch) of pullulanase was added, and the mixture was enzymatically hydrolyzed for 25 minutes at 32℃ and pH 5.2. The enzyme was then inactivated, and the temperature was increased to 60℃ at a rate of 2℃ / min. The mixture was then subjected to pulsed hot-pressing cycling, concentrated under reduced pressure, and vacuum dried to a moisture content of 4.06 wt%. The mixture was then pulverized through a 100-mesh sieve to obtain modified waxy corn starch. The pulsed hot-pressing cycling process was performed at a pressure of 0.1 MPa, with the pressure held for 8 minutes and then released for 2 minutes, repeated 4 times.

[0034] (2) Weighing Xylanase and glucose oxidase were mixed at a weight ratio of 5:3 to obtain a composite enzyme; Sodium bicarbonate and gluconate-δ-lactone were mixed at a mass ratio of 2:1 to obtain a composite leavening agent; Accurately weigh the following ingredients according to their weight proportions: 100 parts high-gluten flour, 8 parts modified waxy corn starch, 2.8 parts compound leavening agent, 0.0015 parts compound enzyme, 0.2 parts sodium lactate, 0.07 parts sodium ascorbate, 1.8 parts salt, 1.5 parts white sugar, 7 parts egg liquid, 5 parts palm oil, and 60 parts ice water.

[0035] (3) Preparation of quick-frozen fried dough stick embryos Mix high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar, and stir at 80 rpm for 5 minutes to obtain a premix. Mix ice water with sodium lactate and sodium ascorbate, add to the premix, and stir at 80 rpm for 10 minutes. Then add egg liquid and palm oil, and stir at 80 rpm for 5 minutes, followed by stirring at 150 rpm for 4 minutes to obtain dough. Cover and let rest at 18℃ for 20 minutes, knead to remove air, and pre-cool under vacuum at -4℃ for 15 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℃ for 30 minutes, and then freeze at -38℃ until the center temperature of the dough reaches -18℃ to obtain quick-frozen fried dough stick dough.

[0036] Example 2 (1) Preparation of modified waxy corn starch Waxy corn starch and water were mixed at a mass ratio of 100:400. 0.25% (by weight of the waxy corn starch) of magnesium carbonate was added. After standing for 25 minutes, the mixture was ultrasonically treated for 15 minutes at 2℃ and 180W. Then, 0.5% (by weight of the waxy corn starch) of pullulanase was added, and the mixture was enzymatically hydrolyzed for 30 minutes at 30℃ and pH 5. The enzyme was then inactivated, and the temperature was increased to 58℃ at a rate of 1.5℃ / min. The mixture was then subjected to pulsed hot-pressing cycling, concentrated under reduced pressure, and vacuum dried to a moisture content of 3.73 wt%. The mixture was then pulverized through an 80-mesh sieve to obtain modified waxy corn starch. The pulsed hot-pressing cycling treatment was performed at a pressure of 0.08 MPa, with pressure maintained for 5 minutes followed by a 1.5-minute depressurization cycle, repeated 5 times.

[0037] (2) Weighing Xylanase and glucose oxidase were mixed at a weight ratio of 4:2 to obtain a composite enzyme; Sodium bicarbonate and disodium dihydrogen pyrophosphate were mixed at a mass ratio of 1.5:1 to obtain a composite leavening agent; Accurately weigh the following ingredients according to the specified weight: 100 parts high-gluten flour, 5 parts modified waxy corn starch, 3.5 parts compound leavening agent, 0.001 parts compound enzyme, 0.18 parts sodium lactate, 0.03 parts sodium ascorbate, 2.2 parts salt, 0.8 parts white sugar, 8 parts egg liquid, 2 parts soybean oil, and 62 parts ice water.

[0038] (3) Preparation of quick-frozen fried dough stick embryos Mix high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar, and stir at 60 rpm for 7 minutes to obtain a premix. Mix ice water with sodium lactate and sodium ascorbate, add to the premix, and stir at 60 rpm for 12 minutes. Then add egg liquid and soybean oil, and stir at 60 rpm for 7 minutes, followed by stirring at 120 rpm for 5 minutes to obtain dough. Cover and let rest at 16℃ for 25 minutes, knead to remove air, and pre-cool under vacuum at -2℃ 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℃ for 35 minutes, and then freeze at -35℃ until the center temperature of the dough reaches -18℃ to obtain quick-frozen fried dough stick dough.

[0039] Example 3 (1) Preparation of modified waxy corn starch Waxy corn starch and water were mixed at a mass ratio of 100:500. 0.35% (by weight of the waxy corn starch) of magnesium carbonate was added. After standing for 25 minutes, the mixture was ultrasonically treated for 10 minutes at 6℃ and 230W. Then, 0.8% (by weight of the waxy corn starch) of pullulanase was added, and the mixture was enzymatically hydrolyzed for 20 minutes at 35℃ and pH 5.5. The enzyme was then inactivated, and the temperature was increased to 62℃ at a rate of 2.5℃ / min. The mixture was then subjected to pulsed hot-pressing cycling treatment, followed by vacuum concentration and vacuum drying to a moisture content of 3.52 wt%. The mixture was then pulverized through a 120-mesh sieve to obtain modified waxy corn starch. The pulsed hot-pressing cycling treatment was performed at a pressure of 0.12 MPa, with pressure held for 10 minutes and then released for 2.5 minutes, repeated three times.

[0040] (2) Weighing Xylanase and glucose oxidase were mixed at a weight ratio of 6:2 to obtain a composite enzyme; Sodium bicarbonate, calcium dihydrogen phosphate, and calcium carbonate are mixed in a mass ratio of 2:1:0.5 to obtain a composite leavening agent; Accurately weigh the following ingredients according to the specified weight: 100 parts high-gluten flour, 10 parts modified waxy corn starch, 1.8 parts compound leavening agent, 0.002 parts compound enzyme, 0.22 parts sodium lactate, 0.1 parts sodium ascorbate, 1 part salt, 1.8 parts white sugar, 3 parts egg liquid, 6 parts rapeseed oil, and 48 parts ice water.

[0041] (3) Preparation of quick-frozen fried dough stick embryos Mix high-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar, and stir at 100 rpm for 5 minutes to obtain a premix. Mix ice water with sodium lactate and sodium ascorbate, add to the premix, and stir at 100 rpm for 12 minutes. Then add egg liquid and rapeseed oil, and stir at 100 rpm for 4 minutes, followed by stirring at 170 rpm for 3 minutes to obtain dough. Cover and let rest at 20℃ for 18 minutes, knead to remove air, and pre-cool under vacuum at -6℃ for 12 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℃ for 25 minutes, and then freeze at -40℃ until the center temperature of the dough reaches -18℃ to obtain quick-frozen fried dough stick dough.

[0042] Comparative Example 1 The difference from Example 1 is that step (1) is omitted and the modified waxy corn starch is replaced with waxy corn starch.

[0043] Comparative Example 2 The difference from Example 1 is that the preparation of modified waxy corn starch in step (1) is as follows: waxy corn starch and water are mixed at a mass ratio of 100:140, 0.3% magnesium carbonate by mass of waxy corn starch is added, and after standing for 30 min, ultrasonic treatment is carried out at a temperature of 4℃ and a power of 200W for 12 min. Then, the temperature is increased to 60℃ at 2℃ / min, and pulse hot pressing cycle treatment is carried out. After depressurization and concentration, vacuum drying is carried out until the water content is 3.92wt% to obtain modified waxy corn starch. The pressure of pulse hot pressing cycle treatment is 0.1MPa, and after holding the pressure for 8 min, the pressure is released for 2 min, and the cycle is repeated 4 times.

[0044] Comparative Example 3 The difference from Example 1 is that the preparation of modified waxy corn starch in step (1) is as follows: waxy corn starch and water are mixed at a mass ratio of 100:140, 0.3% magnesium carbonate by mass of waxy corn starch is added, and after standing for 30 min, ultrasonic treatment is carried out at 4℃ and 200W for 12 min. Pullulanase by mass of waxy corn starch is added, and enzymatic hydrolysis is carried out at 32℃ and pH 5.2 for 25 min. The enzyme is inactivated, the temperature is increased to 60℃ at 2℃ / min, and stirred at 60℃ and 200rpm for 40 min. The mixture is concentrated under reduced pressure and vacuum dried to a water content of 4.16wt% to obtain modified waxy corn starch.

[0045] Comparative Example 4 The difference from Example 1 is that in step (2), the complex enzyme is composed of xylanase and glucose oxidase in a weight ratio of 5:5, and the amount remains the same.

[0046] Comparative Example 5 The difference from Example 1 is that in step (2), the complex enzyme is composed of xylanase and glucose oxidase in a weight ratio of 5:1.2, and the amount remains the same.

[0047] Comparative Example 6 The difference from Example 1 is that sodium lactate in step (2) is replaced with trehalose.

[0048] Application Detection 1 The quick-frozen dough sticks from Examples 1 and Comparative Examples 1-6 were stored at -18°C for 3 months. Fresh dough sticks from Example 1 (not frozen after brushing with water) served as a control.

[0049] The specific volume and oil content of the quick-frozen fried dough sticks from Example 1, Comparative Examples 1-6, and the control were tested respectively.

[0050] For fresh fried dough sticks, place them in oil at 185±5℃. Once they float, turn them over with chopsticks and fry for 50±5 seconds. Remove them from the oil. For frozen fried dough sticks, place them in oil at 185±5℃. Once they float, turn them over with chopsticks and fry for 180±20 seconds. Remove them from the oil.

[0051] The specific volume determination method is the rapeseed displacement method: Weigh the fried dough sticks and record the mass m. Place the dough sticks in a graduated cylinder, fill the graduated cylinder with rapeseed and shake it firmly. Record the volume V1 of the fried dough sticks and rapeseed. Remove the fried dough sticks and record the volume V2 of the rapeseed. Calculate the specific volume. Specific volume (mL / g) = (V1-V2) / m.

[0052] The method for determining oil absorption rate refers to the Soxhlet extraction method in GB 5009.6-2016 National Food Safety Standard for the Determination of Fat in Food.

[0053] Five parallel tests were set up for each sample, and the average of the five parallel tests was taken as the result.

[0054] The specific results of the average specific volume and average oil content of the quick-frozen fried dough sticks of the control, Example 1, and Comparative Examples 1-6 are shown in Table 1.

[0055] Table 1. Specific volume and oil content results of the samples

[0056] As shown in Table 1, the specific volume and oil content of Example 1 are not much different from those of the control, and are significantly better than all comparative examples, indicating that the quick-frozen fried dough sticks of the present invention have good freeze-drying durability.

[0057] Regarding specific volume, in Comparative Example 1, replacing modified waxy corn starch with ordinary waxy corn starch significantly reduced the specific volume of the finished product, demonstrating that the modified waxy corn starch improved the frozen storage stability of the quick-frozen fried dough sticks. Unmodified ordinary starch experienced accelerated aging and retrogradation during freezing, resulting in decreased gas-holding capacity and the inability to effectively encapsulate and dissipate gas generated by the leavening agent during frying. In Comparative Example 2, omitting the enzymatic hydrolysis step in the preparation of modified waxy corn starch led to a decrease in specific volume, indicating a lack of short-chain branched molecules generated by pullulanase hydrolysis, resulting in reduced water retention and freeze resistance of the modified waxy corn starch. In Comparative Example 3, omitting the pulsed hot-pressing treatment resulted in insufficient starch crystal rearrangement, leading to a certain degree of quality deterioration even after long-term frozen storage. In Comparative Examples 4 and 5, changing the ratio of the compound enzymes resulted in a decrease in specific volume. Excessive hydrolysis of insoluble arabinoxylan by xylanase weakens the gluten structure, or excessive hydrogen peroxide produced by glucose oxidase leads to excessive oxidation and brittleness of the gluten, both of which are detrimental to gas holding capacity.

[0058] Regarding oil content, Comparative Example 1 had a higher oil content than Example 1, indicating that after the gluten network was damaged, moisture evaporated rapidly during frying, forming a porous and rough surface, allowing a large amount of oil to penetrate. Comparative Examples 2 and 3 both had higher oil content than Example 1, indicating that missing any step in the preparation of modified waxy corn starch weakens its surface film-forming properties and water-locking ability, leading to increased oil absorption. Comparative Examples 4 and 5 all had higher oil content than Example 1, which may be related to the uniformity of the gluten network and the density of the starch-protein interface.

[0059] The results above show that Example 1 has significant advantages in terms of fluffiness and low oil content. This is due to the water-locking, antifreeze, and slow-release gas-producing effects of the modified waxy corn starch, as well as the gluten strengthening and modification effects of the compound enzyme and the ice crystal refining effect of gradient quick-freezing. This indicates that the present invention has a positive effect on inhibiting frozen storage quality.

[0060] Application Detection 2 Using the fresh fried dough stick embryo from Example 1 (which was not frozen after being brushed with water) as a control, the quick-frozen fried dough stick embryos from Examples 1 and Comparative Examples 1-6 were stored at -18°C for 3 months. Sensory evaluations were conducted on the appearance, color, aroma, taste, and texture of the quick-frozen fried dough stick embryos (stored at -18°C for 3 months) after frying, including the control, Example 1, and Comparative Examples 1-6.

[0061] Twelve professional assessors with sensory evaluation experience in Chinese pastry (six men and six women, 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.

[0062] For sample preparation methods, refer to Application Detection 1.

[0063] All samples were immediately removed from the oil after frying and drained, then placed in a constant temperature and humidity environment for 10 minutes. Samples were randomly numbered with a three-digit code. After preparation, samples were immediately sent to the evaluation room. Evaluators used a blind sample method to avoid subjective bias. Five parallel samples were prepared 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 for all indicators.

[0064] The sensory evaluation criteria are as follows: Appearance: 18-20 points: The fried dough sticks are plump and intact, without any collapse, cracks, or deformities, and are of uniform thickness with symmetrical ends; 14-17 points: The shape is relatively intact, with slight collapse, no obvious cracks, and the thickness is basically uniform; 10-13 points: Incomplete shape, obvious collapse / cracks, uneven thickness, and deformity; 0-9 points: Severely collapsed and broken, unable to maintain the shape of the fried dough stick.

[0065] Color: 18-20 points: The surface is a uniform golden yellow, glossy, without burnt color or whitish / dark areas; 14-17 points: The color is relatively uniform, light golden yellow, without obvious burning, and slightly dark. 10-13 points: Uneven color, localized whitening / burnt areas, overall dull and lacking luster; 0-9 points: Severely charred, or grayish-white overall, with no edible value. aroma: 13-15 points: It has a pure wheat aroma and the unique fragrance of fried dough products, without any rancid or off-flavors; 10-12 points: Mild wheat aroma, no obvious off-odor; 7-9 points: No obvious wheat aroma, with a slight rancid oily smell; 0-6 points: Has a distinct rancid, sour, or other off-odor.

[0066] Taste: 27-30 minutes: crispy on the outside and tender on the inside, with a high degree of crispness on the outside and no hard core. It does not stick to your teeth when chewing, does not soften quickly, and has a rich wheat aroma. 21-26 points: Good crispness, slightly sticky, no obvious hard core, and slow softening speed; 15-20 points: Poor crispness, obvious hard core, sticky to teeth, leaves residue when chewing, and quickly softens and hardens again; 0-14 points: The texture is either soft or hard, making it impossible to chew, and it has a noticeable off-flavor.

[0067] Organizational structure: 13-15 points: The interior is hollow and evenly layered, with a fine mesh structure, without large holes or lumps; 10-12 points: The hollow layers are relatively uniform, with a few small holes and no obvious lumps; 7-9 points: The hollow structure is uneven, with obvious large cavities or doughy lumps, and the texture is loose; 0-6 points: No hollow structure, dense inside, and in a dead state.

[0068] The sensory evaluation scores for each sample are shown in Table 2.

[0069] Table 2 Sensory evaluation scores for each sample (points)

[0070] As shown in Table 2, although the total score of Example 1 was slightly lower than that of the control, it was still at a very high level, and all scores were better than those of the control. In particular, the advantages were significant in terms of taste and texture, which are directly related to frozen storage damage. This demonstrates the significant progress of the present invention in maintaining sensory quality after long-term frozen storage.

[0071] Appearance and color reflect physical damage and oxidative deterioration during freezing. The appearance of Comparative Example 1 was significantly worse than that of Example 1, corresponding to a substantial decrease in specific volume in Table 1. The collapse of the gluten network led to water loss and shrinkage of the raw dough surface, causing cracking of the cross-section and preventing it from maintaining its plump shape after frying. The color of Comparative Example 1 was also significantly lower than that of Example 1, possibly due to starch retrogradation and fat oxidation browning. Comparative Examples 2 and 3 showed better color than Comparative Example 1, indicating that the preparation method of the modified waxy corn starch of this invention has a positive effect on color retention.

[0072] Aroma is a comprehensive evaluation of oil oxidation and flavor retention. Example 1 is similar to the control, while Comparative Example 1 has the lowest score, indicating that free water forms large ice crystals during freezing, which not only damages the gluten structure but also accelerates the oxidation of oils upon contact with oxygen, leading to rancidity.

[0073] Texture and structure are core determinants of consumer acceptance. Example 1 showed little difference in texture from the control, indicating that the frozen fried dough sticks of Example 1 still achieved a crispy exterior, tender interior, and uniformly hollow center after 3 months of frozen storage. Comparative Example 1 exhibited a noticeably hard core, stickiness, softening and hardening after frying, and a dense interior without hollow centers, demonstrating the irreversible damage to the gluten network caused by ice crystals, thus impairing texture and structure. Comparative Examples 2-3 scored lower than Example 1, indicating that physical modification or enzymatic hydrolysis alone cannot simultaneously achieve both antifreeze and water-locking effects, as well as uniform gas production during frying. The texture and structure of Comparative Examples 4-5 were also inferior to Example 1, indicating that the mass ratio of xylanase to glucose oxidase affects the fluffiness and crispness after frying.

[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 quick-frozen dough stick preform with extended shelf life, characterized in that, The ingredients include the following parts by weight: 100 parts high-gluten flour, 5-10 parts modified waxy corn starch, 1.8-3.5 parts compound leavening agent, 0.001-0.002 parts compound enzyme, 0.18-0.22 parts sodium lactate, 0.03-0.1 parts sodium ascorbate, 1-2.2 parts salt, 0.8-1.8 parts white sugar, 3-8 parts egg liquid, 2-6 parts oil, and 48-62 parts ice water.

2. The extended shelf-life quick-frozen fried dough stick dough according to claim 1, characterized in that, The method for preparing the modified waxy corn starch includes: mixing waxy corn starch with water, adding magnesium carbonate, allowing it to stand, ultrasonically treating it, adding pullulanase for enzymatic hydrolysis, inactivating the enzyme, performing pulsed hot-pressing cycle treatment, and vacuum drying to obtain the modified waxy corn starch.

3. The extended shelf-life quick-frozen fried dough stick prep according to claim 2, characterized in that, The mass ratio of the waxy corn starch, magnesium carbonate and water is 100:(0.25-0.35):(400-500).

4. The extended shelf-life quick-frozen fried dough stick prep according to claim 2, characterized in that, The ultrasonic treatment is performed at a temperature of 2-6℃, a power of 180-230W, and a time of 10-15 minutes.

5. The extended shelf-life quick-frozen fried dough stick prep according to claim 2, characterized in that, The pullulanase is added at 0.5-0.8% of the mass of the waxy corn starch, and the enzymatic hydrolysis is performed at a temperature of 30-35℃, a pH of 5-5.5, and a time of 20-30 minutes.

6. The extended shelf-life quick-frozen fried dough stick prep according to claim 2, characterized in that, The pulsed hot-pressing cycle treatment is performed at a temperature of 58-62℃ and a pressure of 0.08-0.12MPa. After holding the pressure for 5-10 minutes, the pressure is released for 1.5-2.5 minutes, and the cycle is repeated 3-5 times.

7. The extended shelf-life quick-frozen fried dough stick prep according to claim 1, characterized in that, The compound leavening agent contains at least one of glucono-δ-lactone, calcium dihydrogen phosphate, calcium carbonate, disodium dihydrogen pyrophosphate, and sodium bicarbonate; the oil contains at least one of palm oil, soybean oil, and rapeseed oil.

8. The extended shelf-life quick-frozen fried dough stick preform according to claim 1, characterized in that, The complex enzyme is composed of xylanase and glucose oxidase in a mass ratio of (4-6):(2-4).

9. A method for preparing extended-shelf-life quick-frozen fried dough stick embryos according to any one of claims 1-8, comprising: High-gluten flour, modified waxy corn starch, compound leavening agent, compound enzyme, salt, and white sugar are mixed to obtain a premix. Ice water is mixed with sodium lactate and sodium ascorbate, and then mixed with the premix. Egg liquid and oil are added to form a dough. The dough is allowed to rest and relax, kneaded, vacuum pre-cooled, pressed into sheets, cut into strips, stacked and shaped, and then quick-frozen in a gradient to obtain a quick-frozen dough stick embryo with extended shelf life.

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

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