Instant dried oyster and method for preparing the same

Abstract

The present application relates to the technical field of aquatic product processing, in particular to instant dried oysters and a preparation method thereof. By taking microwave enzyme inactivation as an independent pretreatment step, precisely controlling the enzyme inactivation temperature, and combining with low-temperature vacuum drying, the problems of mutual restriction between enzyme inactivation and drying, destruction of heat-sensitive nutrients, requirement of cold chain for products, and difficulty in instant eating in the existing dried oyster preparation technology are solved, complete inactivation of endogenous enzymes of oysters and maximum retention of nutritional components are realized, and the prepared instant dried oysters can be stored for a long time at room temperature and eaten immediately after opening the bag.

Description

Technical Field

[0001] This invention relates to the field of aquatic product processing technology, specifically to a ready-to-eat dried oyster and its preparation method. Background Technology

[0002] Oysters (Ostrea gigas Thunberg), also known as raw oysters, are an important economic shellfish in my country. They are rich in nutrients, including protein, taurine, zinc, and selenium, and have high nutritional and health value. However, oyster processing has long faced a serious preservation challenge: oysters have active endogenous enzyme systems, and even after drying, residual enzyme activity can still lead to protein degradation and fat oxidation, producing unpleasant flavor compounds and accelerating spoilage. Currently, dried oyster products mainly rely on frozen storage to maintain quality, which not only significantly increases cold chain costs and transportation restrictions but also limits market promotion and consumer convenience.

[0003] The existing oyster drying and processing technologies mainly include the following: (1) Hot air drying method: The drying temperature is high and the time is long, which can easily lead to protein denaturation, serious loss of nutrients, poor rehydration of products and rough taste.

[0004] (2) Vacuum freeze drying: Although it can better preserve nutrients, it requires large equipment investment, high energy consumption, low production efficiency, and high product cost.

[0005] (3) Microwave vacuum drying method: Existing patents (such as CN102224949A, a preparation process of oyster (oyster) whole nutritional powder (peptide)) use microwave vacuum drying to prepare oyster whole nutritional powder, inactivating enzymes while drying. However, this method combines enzyme inactivation and drying into one process, with process parameters mutually restricting each other, and the product form is powder or peptide, which is not suitable as a ready-to-eat whole meat product. Another patent, CN121286651A (a dried oyster and its preparation method and application), discloses a method for making dried oysters, which involves microwave treatment until the juice content is ≤3% after opening the shell, and then baking at 10℃~40℃. The main purpose of the microwave treatment is to open the shell and perform preliminary drying, rather than specifically to inactivate enzymes.

[0006] In conclusion, developing a method for preparing ready-to-eat dried oysters that can completely inactivate enzymes, maximize the preservation of oyster nutrition and flavor, and allow for room temperature storage has significant practical implications and market value. Summary of the Invention

[0007] The technical problem that this invention aims to solve is that currently, dried oyster products mainly rely on frozen storage to maintain their quality. This not only significantly increases cold chain costs and transportation restrictions, but also limits the market promotion and consumer convenience of the products.

[0008] To address the problems of existing technologies, this invention provides a ready-to-eat dried oyster and its preparation method. This method uses microwave enzyme inactivation as an independent pretreatment step, precisely controls the enzyme inactivation temperature, and combines it with low-temperature vacuum drying. This aims to solve the problems of "mutual restraint between enzyme inactivation and drying, destruction of heat-sensitive nutrients, need for cold chain, and difficulty in ready-to-eat products" in existing oyster drying technologies. It achieves complete inactivation of endogenous enzymes in oysters and maximum retention of nutrients, so that the prepared ready-to-eat dried oysters can be stored at room temperature for a long time and can be eaten immediately after opening the bag.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for preparing ready-to-eat dried oysters, comprising the following steps: (1) Raw material pretreatment: Select fresh oysters or thawed frozen oysters, clean, remove shells and meat, remove mud and impurities, rinse the removed oyster meat with clean water 2-3 times, and drain the surface water. (2) Microwave enzyme inactivation pretreatment: The pretreated oyster meat is placed in a microwave treatment device (433MHz or 915MHz single-mode microwave heating system) for microwave heating enzyme inactivation treatment. The microwave power and heating time are controlled at 1-3KW for 20-60s (under the premise of fixed microwave power, the microwave heating power and time are determined by adjusting the heating time and recording the temperature of the oyster meat, and the microwave heating time should be controlled within 1min). The core temperature of the oyster meat reaches 85-95℃ and is maintained at this temperature for 30-120 seconds to inactivate the endogenous enzymes in the oyster meat. Microwaves have the characteristics of selective heating and rapid temperature rise, which can make the oyster meat uniformly heated to 85-95℃ in a short time. This temperature is sufficient to cause irreversible denaturation and inactivation of the oyster's endogenous proteases and lipoxygenases, while avoiding the loss of nutrients caused by traditional hot water blanching. (3) Low-temperature vacuum drying: Transfer the enzyme-inactivated oyster meat to a vacuum drying equipment and vacuum dry it under the conditions of vacuum degree of 50-100 Pa and temperature of 35-45℃ until the moisture content of the oyster meat drops to below 15%. (4) Packaging: Vacuum packing or nitrogen-filled packaging of dried oyster meat to obtain ready-to-eat dried oyster products.

[0010] This invention creatively incorporates microwave enzyme inactivation as a separate pretreatment step—first, the oyster meat is microwaved to 85–95°C to completely inactivate endogenous enzymes, and then transferred to low-temperature (35–45°C) vacuum drying. This two-step separation allows for independent optimization of the respective process parameters without compromise.

[0011] Furthermore, in step (2), the core temperature of the oyster meat is brought to 90°C and maintained at this temperature for 30–120 seconds. Below this temperature, enzyme inactivation is incomplete, while above this temperature, heat-sensitive nutrients begin to be damaged. This invention precisely targets 90°C as the endpoint for enzyme inactivation, achieving the optimal balance between complete enzyme inactivation and maximum nutrient retention.

[0012] Furthermore, the temperature for low-temperature vacuum drying in step (3) is 40°C. Since the endogenous enzymes in the oyster meat have been deactivated after enzyme inactivation, there is no need to worry about enzymatic degradation during the drying process. The vacuum condition lowers the boiling point of water, so a lower temperature of 40°C can be used for vacuum drying to effectively remove moisture. Low-temperature drying effectively protects heat-sensitive nutrients such as taurine, zinc, and selenium, as well as the natural flavor of the oyster.

[0013] Furthermore, in step (3), the oyster meat is vacuum dried at low temperature until the moisture content is 10%–15%. This ensures that the product falls into a low water activity range where microorganisms cannot reproduce, allowing for long-term storage at room temperature without the need for preservatives; it also avoids the problem of dry, hard meat and poor rehydration caused by excessively low moisture content. This range balances storage stability and palatability, making the product ready to eat immediately after opening and with a suitable chewiness.

[0014] Further, step (4) is a step of seasoning the dried oyster meat before packaging, wherein the seasoning process involves adding salt and / or spices to the oyster meat.

[0015] A ready-to-eat dried oyster prepared by the above method. The product is in whole meat form, can be stored at room temperature for a long time, and can be eaten directly after opening the bag, or rehydrated for cooking. Existing microwave vacuum drying technology for oysters mostly produces powdered or peptide products. This invention completely eliminates enzymatic deterioration factors by thoroughly inactivating enzymes, combined with low water activity (achieved by drying to ≤15% moisture content) and vacuum packaging to isolate oxygen. The synergistic effect of these three factors allows the product to be stored at room temperature for a long time without the need for a cold chain; and it retains the whole meat form of the oyster, becoming a ready-to-eat snack food after vacuum packaging, filling a market gap.

[0016] The beneficial effects of this invention are as follows: (1) Thorough enzyme inactivation and long storage period: Through an independent microwave enzyme inactivation step and precise temperature control, the endogenous enzymes of oysters (mainly protease and lipoxygenase) are completely inactivated, which fundamentally solves the problem of enzyme-induced spoilage. The product can be stored at room temperature for a long time without freezing, completely eliminating the dependence on the cold chain and greatly reducing storage and transportation costs.

[0017] (2) Good nutrient retention: Low-temperature vacuum drying is used after enzyme inactivation, which avoids the destruction of heat-sensitive nutrients such as taurine, zinc, and selenium by high temperature, resulting in a high nutrient retention rate of the product.

[0018] (3) Pure flavor: Low-temperature drying preserves the natural freshness of oysters to the maximum extent, without the burnt or off-flavors produced by hot air drying.

[0019] (4) Novel product form: It retains the shape of whole oyster meat, can be eaten directly after opening the bag, has a suitable taste, can be eaten directly as a snack, or can be used for cooking after rehydration.

[0020] (5) The process is controllable and suitable for industrial production: Microwave enzyme inactivation and vacuum drying are both mature industrial technologies with clear process parameters, which are easy to standardize and scale up production.

[0021] (6) Energy saving and environmental protection: Compared with vacuum freeze drying, it has lower energy consumption; compared with hot air drying, microwave enzyme inactivation is faster and more efficient. Detailed Implementation

[0022] The following description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0023] The following embodiments can be understood as illustrating only a part of the structure or method of the present invention, or as a combination of embodiments explaining the broader structure or method of the present invention. Unless otherwise specified, all raw materials of the present invention are commercially available.

[0024] In the following embodiments, the device is a 433MHz or 915MHz industrial solid-state microwave generator, equipped with an infrared thermometer to monitor the material temperature in real time.

[0025] Example 1: Take 100 kg of fresh oysters, clean them, remove the shells and extract the meat, yielding approximately 35 kg of oyster meat. Rinse the oyster meat three times with clean water and drain.

[0026] Spread the drained oyster meat evenly in a microwave processing device, set the microwave power to 5kW, and the processing time to 3-5 minutes. After the center temperature of the oyster meat reaches 90℃, continue to maintain it for 60 seconds.

[0027] After enzyme inactivation, the oyster meat was transferred to a vacuum drying oven, where a vacuum of 80 Pa and a temperature of 40 °C were set. The oyster meat was dried for 8–12 hours until the moisture content dropped to 12%.

[0028] The dried oyster meat is vacuum-packed, with each bag containing 20-30g. After sealing, the ready-to-eat dried oyster product is obtained.

[0029] Testing showed that the ready-to-eat dried oyster product prepared in this embodiment, when stored at room temperature (25℃) for 6 months, had a TVB-N value ≤15mg / 100g and a total bacterial count ≤10. 4It contains CFU / g, meets food safety standards, and has a delicious taste with no unpleasant flavor.

[0030] Example 2: Take 50 kg of frozen oyster meat, thaw it at room temperature, rinse it twice with clean water, and drain it.

[0031] Place the oyster meat in a microwave processing device with a microwave power of 3kW and a processing time of 4 to 6 minutes. After the center temperature reaches 90°C, maintain it for 90 seconds.

[0032] After enzyme inactivation, the oyster meat was transferred to a vacuum drying device at a vacuum degree of 60 Pa and a temperature of 38 °C for 10–14 hours until the moisture content dropped to 14%.

[0033] The dried oyster meat is seasoned (with appropriate amounts of salt, spices, etc.), and then vacuum-packed to obtain seasoned ready-to-eat dried oysters.

[0034] Comparative example: To verify the technical effects of the present invention, the following comparative examples are provided: Comparative Example 1 (Direct Drying Without Enzyme Inactivation): Oyster meat was directly vacuum dried at 40℃ to a moisture content of 12% without microwave enzyme inactivation. Results: An off-odor appeared during the drying process, and the TVB-N value increased significantly after one month of storage at room temperature, indicating product spoilage.

[0035] Comparative Example 2 (insufficient enzyme inactivation temperature): Microwave treatment was carried out until the core temperature reached 70℃, followed by subsequent drying. Results: After 3 months of storage at room temperature, the product developed an off-odor, and enzyme activity testing showed that some enzyme activity remained.

[0036] Comparative Example 3 (High-Temperature Drying): After microwave inactivation of enzymes to 90°C, the product was dried with hot air at 60°C until the moisture content reached 12%. Results: The product darkened in color, had a slight burnt smell, and the taurine content was reduced by approximately 25% compared to the product of this invention.

[0037] All aspects, embodiments, and features of this invention should be considered illustrative in all respects and not limiting of the invention; the scope of the invention is defined only by the claims. Other embodiments, modifications, and uses will become apparent to those skilled in the art without departing from the spirit and scope of the invention as claimed.

[0038] In the preparation method of this invention, the order of the steps is not limited to the listed order. For those skilled in the art, variations in the order of the steps without creative effort are also within the scope of protection of this invention. Furthermore, two or more steps or actions can be performed simultaneously.

[0039] Finally, it should be noted that the specific embodiments described herein are merely illustrative examples of the invention and are not intended to limit the implementation of the invention. Those skilled in the art can make various modifications or additions to the described specific embodiments or use similar methods to replace them; it is neither necessary nor possible to exemplify all embodiments here. However, these obvious variations or modifications derived from the essential spirit of the invention still fall within the scope of protection of the invention, and interpreting them as any additional limitation would contradict the spirit of the invention.

Claims

1. A method for preparing ready-to-eat dried oysters, characterized in that... Includes the following steps: (1) Raw material pretreatment: Select fresh oysters or thawed frozen oysters, clean, remove shells and meat, remove mud and impurities, rinse the removed oyster meat with clean water 2-3 times, and drain the surface water. (2) Microwave enzyme inactivation pretreatment: The pretreated oyster meat is placed in a microwave treatment device with a solid microwave source of 433MHz or 915MHz for microwave heating enzyme inactivation treatment. The microwave power and heating time are controlled at 1-3KW for 20-60s, so that the core temperature of the oyster meat reaches 85-95℃ and is maintained at this temperature for 30-120 seconds to inactivate the endogenous enzymes in the oyster meat. (3) Low-temperature vacuum drying: Transfer the enzyme-inactivated oyster meat to a vacuum drying equipment and vacuum dry it under the conditions of vacuum degree of 50-100 Pa and temperature of 35-45℃ until the moisture content of the oyster meat drops to below 15%. (4) Packaging: Vacuum packing or nitrogen-filled packaging of dried oyster meat to obtain ready-to-eat dried oyster products.

2. The preparation method according to claim 1, characterized in that: In step (2), the temperature of the oyster meat center is brought up to 90°C and maintained at that temperature for 30 to 120 seconds.

3. The preparation method according to claim 1, characterized in that: In step (3), the temperature for low-temperature vacuum drying is 40℃.

4. The preparation method according to claim 1, characterized in that: In step (3), the oyster meat is dried at low temperature under vacuum until the moisture content is 10% to 15%.

5. The preparation method according to claim 1, characterized in that: Step (4) is the step of seasoning the dried oyster meat before packaging, wherein the seasoning process involves adding salt and / or spices to the oyster meat.

6. A ready-to-eat dried oyster prepared by the method of claim 1, characterized in that: It is in whole meat form and can be stored at room temperature for a long time. It can be eaten immediately after opening the bag, or rehydrated and used for cooking.