Preparation method of coated oyster

Abstract

The present application belongs to the technical field of food processing, and particularly relates to a preparation method of coated oysters. The preparation method comprises the following steps of pretreatment, dry powder coating, batter coating, bread crumb coating, quick freezing and molding, and oil frying. In the batter, a proper amount of sodium carboxymethyl cellulose is added to replace corn starch to improve the rheological property and water holding capacity of the batter, form a dense coating structure, and perform quick freezing to reduce the damage of ice crystals to the oyster tissue, effectively reduce the water loss and oil absorption in the oil frying process, improve the water holding capacity, crispness and tissue integrity of the product, and improve the color and flavor quality of the product. The coated oysters prepared by the method have a crisp shell, tender and juicy interior, low oil content and stable quality, and provide a high-quality processing method for the industrialized production of pre-coated coated aquatic products.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and specifically relates to a method for preparing fried breaded food, particularly a breaded oyster made from oysters and its preparation method. Background Technology

[0002] Oysters are an important marine bivalve mollusks, characterized by high protein, low fat, and rich content of glycogen, taurine, unsaturated fatty acids, and minerals such as zinc and selenium. Their high nutritional value and delicious flavor make them a favorite among consumers. With the rapid development of the prepared food industry, breaded oysters, due to their ease of preparation, crispy texture, and stable flavor, have become one of the most popular prepared aquatic products in catering and home consumption.

[0003] Coated oysters are typically made from oysters through processes such as coating with dry powder, batter, or breadcrumbs, followed by freezing and frying. Product quality is significantly affected by the coating system and freezing process. Because oysters have a high water content and soft texture, large ice crystals easily form during freezing, damaging the muscle tissue and increasing juice loss after thawing. During frying, the coating is prone to cracking or falling off, accompanied by significant moisture loss and oil penetration, resulting in high oil content, decreased texture, deteriorated flavor, and browning, all of which negatively impact product quality and consumer acceptance.

[0004] In existing technologies, most breaded oyster products improve their quality by adjusting the ratio of flour and starch or optimizing the frying process. However, there is limited research on the synergistic regulation of coating system stability, moisture retention capacity, and tissue damage during freezing. Especially under rapid freezing conditions, how to construct a coating structure with good adhesion and water retention to reduce moisture loss and oil absorption during freezing and frying, and improve product crispness, tissue integrity, and overall quality, remains a pressing technical problem to be solved in the field of breaded oyster processing. Summary of the Invention

[0005] This invention provides a method for preparing coated oysters. By optimizing the composition of the coating system and the freezing process, the water-holding capacity and structural stability of the coating are improved, the moisture loss and oil absorption during frying are reduced, and the crispness, texture and overall quality of the product are improved.

[0006] The technical solution of the present invention is a method for preparing coated oysters, comprising the following steps: (1) The pre-treated fresh oyster meat is evenly coated with dry powder to obtain oyster meat with a uniform coating of dry powder on the surface. (2) The oyster meat coated with dry powder obtained in step (1) is placed into a batter that is evenly mixed with wheat flour, corn starch, sodium carboxymethyl cellulose and salt to coat it evenly, and then drained until no batter drips down to obtain oyster meat with even coating; the mass ratio of wheat flour, corn starch and salt is 58-60:39-41:0.9-1.1, preferably 59-59.5:39.5-40:1; 0.25%-0.75% of the mass of corn starch is replaced with sodium carboxymethyl cellulose, preferably 0.3%-0.7% of the mass of corn starch is replaced with sodium carboxymethyl cellulose, further preferably 0.4%-0.6% of the mass of corn starch is replaced with sodium carboxymethyl cellulose, and even more preferably 0.5% of the mass of corn starch is replaced with sodium carboxymethyl cellulose; the total mass of wheat flour, corn starch, sodium carboxymethyl cellulose and salt to the volume ratio of water is 1:1-1.5, preferably 1:1.1-1.3, and even more preferably 1:1.2; (3) Roll the oyster meat coated with breadcrumbs obtained in step (2) evenly to obtain oyster meat with breadcrumbs evenly coated on the surface, with a breading rate of 35%-45%; (4) Quick-freeze the breadcrumb-coated oyster meat obtained in step (3) until its core temperature drops to 100°C. Below 18 ℃; (5) Fry the oyster meat obtained from the quick-freezing process in step (4) at 180℃±5℃ for 2-5 minutes to obtain the coated oysters.

[0007] Step (1), the pretreatment of fresh oyster meat includes: removing the shells from fresh oysters and taking out the meat, immersing it in water and repeatedly rubbing and washing the surface of the oyster meat to remove the surface mucus and attached impurities until the rinsing liquid is clear, draining the water and temporarily storing it at 4°C.

[0008] In step (1), the dry powder is selected from wheat flour and / or corn starch, preferably wheat flour.

[0009] Step (2), the preparation of a paste containing wheat flour, corn starch, sodium carboxymethyl cellulose and salt includes: weighing wheat flour, corn starch, sodium carboxymethyl cellulose and salt in proportion and mixing them, adding water in proportion and stirring evenly, and then letting it stand for 20-25 minutes. The mass ratio of wheat flour, corn starch, and salt is 58-60:39-41:0.9-1.1, preferably 59-59.5:39.5-40:1; 0.25%-0.75% of the corn starch mass is replaced with sodium carboxymethyl cellulose, preferably 0.3%-0.7% of the corn starch mass is replaced with sodium carboxymethyl cellulose, more preferably 0.4%-0.6% of the corn starch mass is replaced with sodium carboxymethyl cellulose, and even more preferably 0.5% of the corn starch mass is replaced with sodium carboxymethyl cellulose; the total mass of wheat flour, corn starch, sodium carboxymethyl cellulose, and salt to the volume ratio of water is 1:1-1.5, preferably 1:1.1-1.3, and more preferably 1:1.2.

[0010] Step (2), the draining time is 30 seconds.

[0011] Before quick-freezing the breadcrumb-coated oyster meat obtained in steps (4) and (3), it is lightly pressed and shaped. Specifically, it is placed in a mold and lightly pressed and shaped.

[0012] Step (4): The breadcrumb-coated oyster meat obtained in step (3) is rapidly frozen at -40°C until its core temperature drops to 40°C. Below 18 ℃, further, control its core temperature to drop to... 18 ℃; quick-freezing time is 40-50 min.

[0013] Step (4), the quick-freezing method is blower freezing or liquid nitrogen freezing.

[0014] Step (5): The oyster meat obtained from the quick-freezing process in step (4) is directly fried at 180℃±5℃. The frying temperature is preferably 180℃±3℃, and more preferably 180℃±2℃. The frying time is preferably 2.5-4.5 min, more preferably 3-4 min, and even more preferably 3.4-3.6 min.

[0015] The mass-to-volume ratio of oyster meat obtained from quick-freezing in steps (5) and (4) to frying oil is 1:2.5-3.5, preferably 1:2.8-3.2, and more preferably 1:3.

[0016] The present invention provides powdered oysters, which are prepared by the powdered oyster preparation method provided above.

[0017] The preparation method of this invention uses a batter in which an appropriate amount of sodium carboxymethyl cellulose (CMC) is added to replace part of the corn starch, and rapid freezing is performed using blower freezing or liquid nitrogen freezing. CMC improves the rheological properties and water-holding capacity of the batter, forming a continuous and dense coating structure. Simultaneously, rapid freezing reduces the damage of ice crystals to the oyster tissue, effectively reducing moisture loss and oil absorption during frying, improving the product's water retention, crispness, and tissue integrity, as well as its color and flavor. The coated oysters prepared by this invention exhibit simultaneously improved integrity, low oil retention, and antioxidant quality. The coated oysters have crispy shells, tender and juicy interiors, low oil content, and stable quality, providing a high-quality processing method for the industrial production of pre-coated aquatic products. This solves the technical problems of traditional coated oysters, such as severe moisture loss, high oil content, easy oxidation, and poor texture and quality. Attached Figure Description

[0018] Figure 1 This is a process flow diagram of the method for preparing breaded oysters according to the present invention.

[0019] Figure 2 This is a schematic diagram of the three-stage processing product of the breaded oysters according to the present invention.

[0020] Figure 3 The effect of different CMC concentrations of batter on the pick-up rate of breaded oysters.

[0021] Figure 4 The variation in water retention of batter with different CMC concentrations.

[0022] Figure 5 The effect of different CMC concentrations of batter on the changes in water content of coated oyster shells and oyster meat after frying (2.5 min, 3.5 min, 4.5 min) was investigated, where Batter represents the fried shell group and Core represents the internal oyster meat group.

[0023] Figure 6 The effect of different CMC concentrations of batter on the oil content of coated oyster shells and oyster meat after frying (2.5 min, 3.5 min, 4.5 min).

[0024] Figure 7 The effect of different CMC concentrations of batter on the carbonyl changes of oyster meat myofibrillar protein inside oysters after frying (2.5 min, 3.5 min, 4.5 min).

[0025] CK was the control group, C-0.25% was the 0.25% CMC batter group, C-0.5% was the 0.5% CMC batter group, and C-0.75% was the 0.75% CMC batter group. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of this invention, and not all of them. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0027] Example 1 A method for preparing powdered oysters, the specific steps of which are as follows: S1. Oyster pretreatment: Remove the meat from the fresh oysters, immerse them in water and repeatedly rub the surface of the oyster meat with your hands to remove the surface mucus and attached impurities until the rinsing liquid is clear. After draining the water, store them temporarily in a refrigerator at 4°C.

[0028] S2. Coat with dry powder: After wiping the surface of the oysters dry with kitchen paper towels, coat them with wheat flour to form a uniform dry powder layer on the surface of the oysters.

[0029] S3. Coating with Batter: Take wheat flour, corn starch, and salt in a mass ratio of wheat flour:corn starch:salt = 59.4:39.6:1.0. Replace 0.5% of the corn starch mass with sodium carboxymethyl cellulose (CMC). The flour-to-water mass-to-volume ratio is 1:1.2. After stirring evenly, let it stand for 20-25 minutes to allow the batter to fully hydrate, flow well, and appear smooth and uniform. Then, dip the oysters coated with dry flour into the batter to coat them evenly, and drain for 30 seconds until no batter drips down.

[0030] S4. Breading: Roll the battered oysters evenly in breadcrumbs, ensuring the breadcrumbs adhere evenly to the product surface, thus maximizing the coating rate. The content is stabilized between 35% and 45%, and then placed in a mold to set.

[0031] S5. Rapid Freezing: Place the breaded oysters in the mold into a -40℃ forced-air quick-freezing machine for rapid freezing and monitor the center temperature. When the center temperature of the product drops to... Remove from the refrigerator and store below 18°C.

[0032] S6. Deep-frying: Without fully thawing, the frozen, breaded oysters are directly deep-fried in preheated cooking oil at 180°C. To ensure consistent oil quality, the oil is changed after each batch. The oyster-to-oil volume ratio is maintained at 1:3 to ensure adequate oil coverage and even heating. When the oil temperature reaches 180°C, the oysters are evenly added and fried until golden brown and crispy on the outside and cooked through on the inside. They are then removed and drained of excess oil to obtain the breaded oyster product.

[0033] Example 2 A method for preparing powdered oysters, the specific steps of which are as follows: S1. Oyster pretreatment: Same as in Example 1.

[0034] S2, Coating with dry powder: Same as in Example 1.

[0035] S3. Coating with batter: Same as in Example 1, except that 0.25% of the corn starch mass is replaced with sodium carboxymethyl cellulose (CMC).

[0036] S4. Coat with breadcrumbs: Same as in Example 1.

[0037] S5. Rapid freezing: Same as in Example 1.

[0038] S6. Frying and shaping: Same as in Example 1.

[0039] Example 3 A method for preparing powdered oysters, the specific steps of which are as follows: S1. Oyster pretreatment: Same as in Example 1.

[0040] S2, Coating with dry powder: Same as in Example 1.

[0041] S3. Coating with batter: Same as in Example 1, except that 0.75% of the corn starch mass is replaced with sodium carboxymethyl cellulose (CMC).

[0042] S4. Coat with breadcrumbs: Same as in Example 1.

[0043] S5. Rapid freezing: Same as in Example 1.

[0044] S6. Frying and shaping: Same as in Example 1.

[0045] Results analysis: (1) The effect of CMC on coating pick-up rate Compared to the C-0.25%, C-0.5%, and C-0.75% groups, the CK group batter did not contain sodium carboxymethyl cellulose (CMC).

[0046] The oysters were immersed in the prepared batter for 10 seconds, coated, and dripped for 10 seconds. After being weighed again, the amount of coating picked up was calculated using the following formula: Where m1 represents the mass of the oyster raw material after it has been dried, and m2 represents the weight of the oyster after it has been coated with batter.

[0047] The results are as follows Figure 3As shown, the pick-up rates of the batter with different CMC contents ranged from 36.73% to 47.52%. Initially, the low concentration of CMC in the batter did not significantly change the coating pick-up rate, but as the concentration gradually increased, the batter pick-up rate increased significantly. Only when the amount of CMC added reached a certain level could its thickening and network-enhancing effects be effectively converted into stronger coating adhesion, leading to an increase in fluid flow resistance.

[0048] (2) The effect of CMC on the water-holding capacity of batter Compared to the C-0.25%, C-0.5%, and C-0.75% groups, the CK group batter did not contain sodium carboxymethyl cellulose (CMC).

[0049] Place 10 g of freshly prepared batter into a 50 mL centrifuge tube, centrifuge at 4000 rpm for 5 min, remove the supernatant and weigh the remaining portion, then calculate the water retention of the batter using the following formula: Where m3 represents the total weight before centrifugation, and m4 represents the weight of the remaining centrifuge tube after the supernatant is removed.

[0050] like Figure 4 As shown, compared with the control group (CK), the addition of CMC affected the water-holding capacity of the batter, and the water content (WHC) increased significantly with increasing CMC content. This is because the presence of hydrophilic groups such as carboxymethyl groups in the CMC molecule promotes the binding of water with the system components. Notably, there was no significant difference between the CMC-0.5% and CMC-0.75% treatment groups. This phenomenon may be because the water binding and retention capacity of the batter network has stabilized, and further increasing CMC did not lead to further improvement.

[0051] (3) Changes in oil and water content inside and outside the powdered oyster shell coating The shells and oyster meat of the deep-fried, breaded oysters were separated within 30 minutes of frying. The moisture content of both the breaded shells and oyster meat was measured using an electric blast drying oven (DHG-9053A, Shanghai Yiheng Technology Co., Ltd., China). The shells and meat were placed in the drying oven at 105 °C until a constant weight was obtained. Moisture content was calculated as a percentage of the weight loss before and after drying relative to the weight of the sample before drying. Furthermore, the oil content of the breaded shells and oyster meat was measured using a Soxhlet extractor with petroleum ether (30–60 °C) as the solvent. Oil content was calculated as a percentage of the extracted oil mass relative to the corresponding sample mass before drying.

[0052] As frying time increased, the moisture content of both the outer shell and the inner meat in all groups showed a decreasing trend (Figure 5), which may be because the heating process promoted moisture loss. Previous studies have shown that the addition of CMC inhibits moisture evaporation to some extent. This may be because CMC not only helps to enhance the barrier effect and continuity of the coating, but also because its hydrophilic groups can bind with water molecules, improving the water-holding capacity of the system. Therefore, the inner oyster meat, protected by the shell, maintained a high moisture content and a low oil content throughout the frying process.

[0053] Corresponding to the change in moisture content, the oil content of the shells in the CMC-treated groups was generally lower than that in the control group (Figure 6), further illustrating that the CMC-mediated shell structure helps inhibit oil absorption. The oil content of the shells in the control group did not change significantly throughout the frying process. Notably, after frying for 3.5 min, the moisture and oil content of the shells in all CMC-treated groups generally tended to stabilize; however, the moisture and oil content of the shells in the CMC-0.75% group decreased significantly after 3.5 min, while the oil content of the oyster meat inside was higher than in the other experimental groups. This may be because excessive CMC addition leads to an overly thick coating and reduced structural uniformity, making the shell more prone to cracking under strong thermal stress, thus weakening its barrier effect and promoting oil penetration.

[0054] (4) Analysis of carbonyl changes in proteins of deep-fried breaded oysters 5 g of sample was mixed with four times its volume of solution A (0.1 M NaCl, 2 mM MgCl2, 1 mM EDTA, pH 7.0) and homogenized for 30 s. The mixture was then centrifuged at 10,000 rpm for 15 min, and the supernatant was discarded. This process was repeated twice. The precipitate was then homogenized with four times its volume of solution B (0.6 M NaCl, pH 7.0), allowed to stand at 4 °C for 2 h, and then centrifuged (10,000 rpm, 15 min). The supernatant was collected as the MP solution and stored at 4 °C. All analyses were performed within 48 h. The entire procedure was performed on ice. Two aliquots of the diluted MP solution were taken as a control and a blank, each 2 mL in volume. The control tube was thoroughly mixed with 2 mL of 10 mM DNPH, and the blank tube was thoroughly mixed with hydrochloric acid (2 mol / L). The reaction was carried out in the dark for 1 h. The solution was then incubated with 20% TCA on ice for 15 min, followed by centrifugation at 10,000 rpm and 4 °C for 10 min. The precipitate was washed three times with ethanol and ethyl acetate (1:1). The precipitate was then dissolved in 1 mL of 6 mol / L guanidine hydrochloride and incubated in the dark at 37 °C for 30 min, followed by centrifugation under the same conditions for 10 min. The absorbance was measured at 370 nm, and a blank tube was used to zero the absorbance.

[0055] like Figure 7As shown, with increasing frying time, the oxidation of oyster myofibrillar proteins significantly intensified, and the carbonyl content increased markedly. Compared with the control group, the addition of CMC generally slowed down the protein oxidation process. This is mainly attributed to the shell network constructed by CMC, which has a certain barrier effect on the migration of oil and oxygen during frying, while delaying the transfer of heat to the interior, thereby inhibiting protein oxidation. At 3.5 min of frying, C-0.25%, C-0.5%, and C-0.75% were reduced by 30.46%, 36.67%, and 29.40% respectively compared with the control group, with the C-0.5% group showing the best performance. This may be because the continuous and stable barrier shell can achieve better water retention and oil resistance. C-0.75% showed shell cracking in the later stage of frying, further aggravating protein oxidation. In conclusion, an appropriate concentration of CMC can delay protein oxidation and reduce the negative effects of high temperature.

[0056] This invention develops a new product of coated oysters. The ingredients selected through experiments are: wheat flour, corn starch, and salt in a mass ratio of 59.4:39.1:1.0. 0.5% of the corn starch mass is replaced with CMC, and the flour-to-water ratio is 1:1.2. Compared with the original formula, the water retention rate of the batter is increased by 14.13%, the coating pick-up rate is increased by 13.58%, the oil content of the shell is reduced by 19.56% after frying for 3.5 minutes, the water content of the oyster meat is increased by 3.55%, the color is stable, and the protein carbonyl content is reduced by 36.67%. This achieves simultaneous improvement in structural integrity, low oil water retention, and antioxidant quality, solving the problem of high oil content in traditional coated oysters.

[0057] This invention improves the adhesion and water retention of coated oyster shells by optimizing the composition of the coating system and the freezing process, reduces moisture loss and oil absorption during freezing and frying, and improves the texture, color and overall quality of the product. It provides an efficient, stable and commercially viable technical solution for the processing of pre-coated aquatic products.

[0058] Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions provided above are only for illustrating the principles of the present invention and are not intended to limit the scope of protection of the present invention. Various modifications, substitutions, or improvements can be made to the present invention without departing from its spirit and essence. For example, adjustments can be made to the amount of sodium carboxymethyl cellulose (CMC) added, the composition and ratio of the breading system, the breading rate, the freezing method, the freezing endpoint temperature, the frying temperature, the frying time, and other process parameters suitable for breaded aquatic product processing. All such modifications, substitutions, or improvements should fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for preparing coated oysters, characterized in that the steps include... include: (1) Coating with dry powder: The pre-treated fresh oyster meat is placed in dry powder and coated evenly to obtain oyster meat with a uniform coating of dry powder on the surface; (2) Coating with batter: Place the oyster meat coated with dry powder obtained in step (1) into a batter that is evenly mixed with wheat flour, corn starch, sodium carboxymethyl cellulose and salt, and make it evenly coated with batter. Drain until no batter drips down to obtain oyster meat with even coating. The mass ratio of wheat flour, corn starch and salt is 58-60:39-41:0.9-1.

1. 0.25%-0.75% of the mass of corn starch is replaced with sodium carboxymethyl cellulose. The total mass of wheat flour, corn starch, sodium carboxymethyl cellulose and salt and the volume ratio of water are 1:1-1.

5. (3) Coating with breadcrumbs: Roll the oyster meat coated with the batter obtained in step (2) evenly in breadcrumbs to obtain oyster meat with a breadcrumb coating evenly on the surface, with a coating rate of 35%-45%; (4) Quick-freezing: The breadcrumb-coated oyster meat obtained in step (3) is quick-frozen until its core temperature drops to a certain level. Below 18 ℃; (5) Frying and shaping: Fry the oyster meat obtained from the quick-freezing treatment in step (4) at 180℃±5℃ for 2-5 minutes to obtain the powdered oysters.

2. The preparation method according to claim 1, characterized in that, Step (1), the pretreatment of fresh oyster meat includes: removing the shells from fresh oysters and taking out the meat, immersing it in water and repeatedly rubbing and washing the surface of the oyster meat to remove the surface mucus and attached impurities until the rinsing liquid is clear.

3. The preparation method according to claim 1, characterized in that, Step (1), the dry powder is selected from wheat flour and / or corn starch.

4. The preparation method according to claim 1, characterized in that, Step (2), the preparation of a paste containing wheat flour, corn starch, sodium carboxymethyl cellulose and salt includes: weighing wheat flour, corn starch, sodium carboxymethyl cellulose and salt in proportion and mixing them, adding water in proportion and stirring evenly, and then letting it stand for 20-25 minutes.

5. The preparation method according to claim 1, characterized in that, Step (2), the draining time is 30 seconds.

6. The preparation method according to claim 1, characterized in that, The breadcrumb-coated oyster meat obtained in step (3) was rapidly frozen at -40°C until its core temperature dropped to -40°C. Below 18 ℃.

7. The preparation method according to claim 1 or 6, characterized in that, Step (4), the center temperature is 18 ℃.

8. The preparation method according to claim 1, characterized in that, Before quick-freezing, the breadcrumb-coated oyster meat obtained in steps (4) and (3) is lightly pressed and shaped.

9. The preparation method according to claim 1, characterized in that, The mass-to-volume ratio of oyster meat obtained from quick-freezing in steps (5) and (4) to frying oil is 1:2.5-3.

5.

10. Flour-coated oysters, characterized in that, It is prepared by any one of claims 1-9.

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