Ancient-method dried rabdosia lophanthide making method based on TPA texture analysis and dried rabdosia lophanthide product

Abstract

The invention provides an ancient-method dried rabdosia lophanthide making method based on TPA texture analysis and a dried rabdosia lophanthide product, and belongs to the field of aquatic product processing. The method provided by the invention comprises the following steps: measuring water content, protein content and fat content data of fish meat; carrying out vacuum-normal pressure back infiltration circular treatment; at least three stages of gradient dehydration and pulse air supply drying are carried out in sequence; in the gradient dehydration and pulse air supply drying process, on-line sampling is carried out at a plurality of preset sampling time points, and TPA characteristic indexes of the obtained samples are measured through a texture analyzer; calculating a predicted texture quality index; the predicted texture quality index is compared with a preset target texture quality index, and a process parameter correction value of at least one stage in the dehydration and pulse air supply drying treatment process is calculated; and adjusting the process parameters of the corresponding stages based on the process parameter correction values. According to the making method and the dried fish product provided by the invention, salt reduction, nutrition retention, stable texture and high-efficiency production can be realized at the same time.

Description

Technical Field

[0001] This application relates to the field of aquatic product processing technology, and in particular to a traditional method for making dried stream fish based on TPA texture analysis and the dried fish product. Background Technology

[0002] Stream fish, represented by the Acrossocheilus fasciatus, have delicate and delicious flesh, and are rich in highly nutritious polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). Dried fish made from these fish using traditional methods has a unique flavor and is highly favored by consumers, making it a specialty aquatic resource with good market potential.

[0003] However, the traditional process relies heavily on experiential judgment based on sight, touch, and smell, resulting in a series of technical defects that urgently need to be addressed: First, the sodium content of the products is too high, with salt concentrations typically reaching 8-12%, far exceeding the recommended daily intake and not in line with modern healthy eating trends; second, nutrients and flavor substances are severely lost, with EPA / DHA oxidation rates exceeding 20% ​​during processing, and significant volatilization of flavor amino acids; third, quality evaluation is subjective and unstable, lacking objective and quantitative control standards, leading to significant fluctuations in the texture (softness, hardness, toughness) of different batches of products, with differences reaching ±15% or more, severely restricting the standardized inheritance of the process, large-scale production, and brand development; fourth, production efficiency is low, with process parameter adjustments relying entirely on trial and error, resulting in a waste of time and materials.

[0004] To address these issues, existing technologies have made some attempts, such as using hot air drying and heat pump drying to improve efficiency, or applying vacuum freeze-drying to preserve nutrients. However, these technologies are mainly designed for the texture characteristics of marine fish and are not well-suited to the delicate muscle fibers and easily oxidized fats of freshwater fish: high-temperature rapid drying can easily cause the surface proteins of freshwater fish to denature quickly, forming a dense, hard shell, exacerbating uneven drying inside and out, hardening of the texture, and loss of internal nutrients and flavor; while vacuum freeze-drying can better preserve nutrients, it is expensive, and the finished product has a crumbly texture, which deviates significantly from the chewiness and flavor characteristics of traditional dried fish, limiting market acceptance.

[0005] Although texture profile analysis (TPA) technology has been widely used for the objective evaluation of the texture of finished food products, its function is mostly limited to post-processing detection in existing technologies. How to accurately and directly couple the microscopic dynamic changes in texture with macroscopic process parameters to achieve a fundamental shift from experience-driven to data-driven production has become a technical bottleneck restricting the intelligent and standardized production of dried river fish and similar traditional specialty foods. Summary of the Invention

[0006] In view of this, this application provides a traditional method for making dried river fish and a dried fish product based on TPA texture analysis, which can stably produce high-quality dried river fish products that are low in salt, healthy, have high nutrient retention, uniform texture, and can be standardized, while preserving the traditional flavor.

[0007] Specifically, this application is implemented through the following technical solution:

[0008] The first aspect of this application provides a traditional method for making dried river fish based on TPA texture analysis, the method comprising:

[0009] After pretreatment of fresh stream fish, the water content, protein and fat content of the fish meat were measured.

[0010] The pretreated fish meat is immersed in a low-salt permeate solution and subjected to vacuum-atmospheric pressure re-osmosis circulation treatment.

[0011] The fish meat, after being treated by vacuum-atmospheric pressure re-osmosis circulation, is subjected to at least three stages of gradient dehydration and pulsed air drying.

[0012] During the gradient dehydration and pulsed air drying process, online sampling was carried out at multiple preset sampling time points, and the TPA characteristic index of the samples was measured using a texture analyzer.

[0013] Based on the data measured after pretreatment, the process parameters during the vacuum-atmospheric pressure re-osmosis cycle treatment and the gradient dehydration and pulse air drying process, and the TPA characteristic index, the control unit calculates and predicts the texture quality index through a pre-established mapping model between process parameters and TPA texture index.

[0014] The predicted texture quality index is compared with the preset target texture quality index. When the absolute difference between the two texture quality indices is greater than a set threshold, the process parameter correction value for at least one stage of the dehydration and pulse air drying process is calculated in reverse based on the process parameters and the TPA texture index mapping model.

[0015] Based on the process parameter correction value, adjust the process parameters of the corresponding stage, and return to continue executing gradient dehydration and pulse air drying. Repeat the subsequent steps starting from the online sampling until the absolute difference between the two texture quality indices is less than or equal to the set threshold, thus completing the production of dried fish.

[0016] The second aspect of this application provides a traditional stream fish dried product based on TPA texture analysis, wherein the dried fish product has a sodium content of 1.5% to 3.5%, a texture variation coefficient of ≤5%, an EPA / DHA retention rate of >92%, a water activity Aw of ≤0.75, and a moisture difference between the surface and interior of the fish meat of ≤2%.

[0017] The traditional method for making dried stream fish and the dried fish products based on TPA texture analysis provided in this application have the following advantages compared with traditional traditional processes and existing improved technologies:

[0018] 1. Significantly reduce sodium content and upgrade product health: By adopting a vacuum-re-osmosis circulation low-salt permeation process, the salt concentration of the permeate is reduced from the traditional 8-12% to 1.5-3.5% (w / w), resulting in a reduction of more than 30% in the salt content of the final product, thus solving the problem of high sodium content in traditional dried fish.

[0019] 2. Highly efficient preservation of core nutrients and inherent flavor: Through a three-level gradient temperature and humidity and pulsed air drying strategy, combined with natural antioxidants added to the permeate solution, oxidation reactions and heat damage during processing are effectively inhibited. This process can keep the retention rate of heat-sensitive polyunsaturated fatty acids EPA and DHA stable at over 92%, and reduce the volatilization of flavor amino acids. Thus, while reducing salt content, it maximizes the preservation of the inherent fresh flavor and nutritional value of stream fish, effectively solving the problem of loss of both nutrition and flavor.

[0020] 3. Improved production efficiency and resource utilization: The data-driven closed-loop intelligent control model completely replaces the traditional experience-based approach of adjusting processes by looking, touching, smelling, and trial and error. It can perceive, predict, and automatically correct production deviations in real time, reducing rework and scrap caused by substandard quality. It transforms the adjustment of production process parameters from lagging and inefficient to immediate and precise, thereby significantly improving production efficiency and resource utilization. Attached Figure Description

[0021] Figure 1 This is a flowchart of Example 1 of the traditional method for making dried river fish based on TPA texture analysis provided in this application. Detailed Implementation

[0022] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this application.

[0023] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms “a,” “the,” and “the” used herein are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0024] It should be understood that although the terms first, second, third, etc., may be used in this application to describe various information, such information should not be limited to these terms. These terms are only used to distinguish information of the same type from one another. For example, without departing from the scope of this application, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the word "if" as used herein may be interpreted as "when," "when," or "in response to determination."

[0025] The following specific embodiments are given to illustrate the technical solution of this application in detail.

[0026] Example 1

[0027] Figure 1 This is a flowchart of Example 1 of the traditional method for making dried river fish based on TPA texture analysis provided in this application. Please refer to... Figure 1 The method provided in this embodiment may include:

[0028] S101. After pre-treating fresh stream fish, measure the water content, protein content, and fat content of the fish meat.

[0029] It should be noted that this embodiment preferably uses fresh Acrossocheilus fasciatus as raw material. This fish species is a common stream fish with delicate muscle fibers, delicious flesh, and is rich in polyunsaturated fatty acids such as eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), which are beneficial to the human body. It is an ideal raw material for making high-quality dried fish.

[0030] Specifically, the pretreatment involves stunning the live gudgeon, quickly scraping off the scales, gutting the fish, and removing the black membrane from the abdomen. The fish is then thoroughly rinsed with clean, cool running water to remove blood and impurities. After cleaning, the fish is split in half along the spine, or cut into uniformly sized segments according to product specifications. This standardized cutting aims to eliminate individual morphological differences in the raw materials, ensuring uniformity and consistency in subsequent processing, such as salting and drying.

[0031] After completing the above pretreatment, representative samples should be immediately extracted from the same batch of raw materials, and their basic moisture content, crude protein content, and crude fat content should be rapidly determined using industry standard methods. For example, moisture content can be determined by direct drying, crude protein content by the Kjeldahl method, and crude fat content by Soxhlet extraction.

[0032] It should be noted that the initial composition of stream fish caught in different batches and seasons naturally fluctuates. Accurately measuring this data is essential to establishing an objective and quantitative starting point for all subsequent processing steps. Furthermore, the protein and fat content of the raw materials directly affects their heat denaturation temperature, moisture-binding capacity, and the texture formation pathway during drying. Recording these measurements at the outset helps in accurately predicting the final product's texture.

[0033] S102. Immerse the pretreated fish meat in a low-salt permeate solution and perform vacuum-atmospheric pressure re-osmosis circulation treatment.

[0034] To address the issues of excessive sodium content and loss of nutrients and flavor in traditional processes, this embodiment employs a treatment process combining low-salt permeate with vacuum-re-osmosis circulation.

[0035] Specifically, a functional low-salt permeate solution is first prepared, based on a salt solution with a mass concentration controlled between 1.5% and 3.5% (w / w). Compared to traditional high-salt solutions of 8-12%, this concentration design can reduce the sodium content of the final product by more than 30%, meeting health requirements. To ensure product preservation and flavor quality while reducing salt, at least one of natural antioxidants and flavor enhancers is selectively added to the permeate solution. Preferably, the natural antioxidant is tea polyphenols, whose main function is to inhibit the oxidation of polyunsaturated fatty acids such as EPA and DHA, which are abundant in fish, during subsequent processing; the flavor enhancer includes seaweed and seaweed extracts, whose abundant natural flavor substances can effectively compensate for the blandness that may result from salt reduction and enhance the natural umami flavor of the fish.

[0036] The use of natural antioxidant tea polyphenols in this application has advantages over synthetic antioxidants (such as BHT and BHA) or other natural alternatives. First, tea polyphenols are a general term for a class of polyhydroxyphenolic compounds. The phenolic hydroxyl groups in their molecular structure can effectively provide hydrogen atoms, neutralizing lipid free radicals and interrupting the chain reaction of lipid oxidation. For river fish meat rich in easily oxidized polyunsaturated fatty acids (such as EPA and DHA), tea polyphenols have extremely strong free radical scavenging and metal ion chelating abilities, effectively inhibiting lipid oxidation and rancidity during processing and storage. Their antioxidant activity has been proven to be superior to or equivalent to some synthetic antioxidants in many systems. Second, tea polyphenols are natural extracts from tea leaves, widely considered safe, and have a long history of use in food with broad consumer acceptance. They also possess various potential health benefits (such as antibacterial and anti-inflammatory properties). The use of tea polyphenols completely avoids consumer concerns and regulatory restrictions that may arise from the use of synthetic antioxidants, perfectly aligning with the upgraded positioning of salt reduction and health promotion. Furthermore, the inherent flavor (slight astringency) of tea polyphenols generally exhibits good compatibility when combined with seafood, without producing unpleasant off-flavors. More importantly, by inhibiting lipid oxidation, it effectively prevents the formation of rancid and fishy-smelling substances in fish, thus protecting and highlighting the original umami flavor of the fish. Here, tea polyphenols can synergistically work with flavor enhancers such as seaweed to create a rich and harmonious flavor profile. It should also be noted that in the subsequent gradient drying stages, especially in the second (60-70℃) and third (75-85℃) stages, tea polyphenols exhibit good thermal stability, continuously exerting their antioxidant effects throughout the drying process. In addition, after significant salt reduction, the product's preservative and antibacterial capabilities partially depend on low water activity (Aw). Tea polyphenols themselves possess certain broad-spectrum antibacterial activity, and their addition can beneficially complement the salt reduction system, synergizing with low Aw to further ensure the product's microbial safety.

[0037] After preparing the permeate solution, a vacuum-re-osmosis cycle is performed. Specifically, the pre-treated and drained fish meat is completely immersed in the low-salt permeate solution and then placed in a sealed container. First, the vacuum pump is activated to reduce the pressure inside the container to 60-80 kPa, and this vacuum condition is maintained for 5-15 minutes. The purpose of this vacuum stage is to utilize the negative pressure environment to quickly remove air from the interstitial spaces and microvessels of the fish meat tissue, eliminating osmotic resistance and creating conditions for rapid, deep initial permeation of the low-concentration salt. Subsequently, the vacuum is released, allowing the pressure inside the container to return to normal atmospheric pressure. The purpose of the atmospheric pressure re-osmosis stage is to utilize the external atmospheric pressure to force the permeate solution already attached to the surface of the fish meat to further penetrate and diffuse into the muscle tissue along the microchannels formed during the vacuum stage.

[0038] It should be noted that, in order to achieve a full and uniform distribution of salt and flavor compounds within the fish meat and to avoid uneven penetration, the above-mentioned vacuum treatment-atmospheric pressure re-osmosis process constitutes a complete treatment cycle. Preferably, this cycle is repeated 2 to 3 times. Through this cyclic treatment, the effective penetration of salt and functional components can be ensured while significantly reducing the amount of salt used, providing a uniform starting point for flavor and texture in the subsequent dehydration process.

[0039] S103. The fish meat that has undergone vacuum-atmospheric pressure re-osmosis cycle treatment is subjected to at least three stages of gradient dehydration and pulse air drying.

[0040] It should be noted that the gradient dehydration and pulse air drying process includes a first stage (pre-drying stage), a second stage (main drying stage), and a third stage (final drying stage).

[0041] The first stage is conducted at a temperature of 20°C to 30°C and a relative humidity of 75% to 85%, with a drying time of 2 to 3 hours. This stage utilizes a pulsed airflow mode throughout, with the pulsed airflow duty cycle (the ratio of airflow time to the total cycle time) set at 1:2. It should be noted that the purpose of the first stage is to achieve a gentle start-up and prevent the formation of a hard, dense crust. The lower initial temperature and higher ambient humidity significantly slow down the rate of moisture evaporation from the fish surface, thus preventing rapid denaturation, contraction, and the formation of a dense crust due to excessive surface moisture loss. The pulsed airflow, with its one-blow-two-stop (1:2 duty cycle) interval longer than the airflow period, promotes airflow while providing ample time for the fish surface to rehydrate, facilitating the migration of internal moisture to the surface and laying the foundation for subsequent efficient and uniform dehydration.

[0042] After completing the first stage, the second stage begins. In this stage, the ambient temperature is raised to 60°C to 70°C, the relative humidity is adjusted to 55% to 60%, and the drying time is 1 to 2 hours. The pulse airflow duty cycle in the second stage is adjusted to 1:1. It should be noted that the purpose of the second stage is efficient dehydration. Increasing the temperature accelerates the migration kinetic energy of water molecules, while moderately reducing humidity increases the water vapor partial pressure difference between the fish surface and the air, strengthening the driving force for dehydration. At this point, since the formation of a hard surface crust has been effectively suppressed in the first stage, the diffusion path of internal moisture is relatively unobstructed. Using a pulse airflow mode with half-blowing and half-stopping (1:1 duty cycle), dehydration efficiency is ensured while the intermittent periods mitigate excessive surface moisture loss, continuously guiding internal moisture to replenish the surface, thereby ultimately reducing the average water content of the fish to approximately 28%.

[0043] Finally, the third stage is conducted, with a controlled temperature of 75°C to 85°C and a relative humidity of 45% to 55%, for a short drying period of 0.4 to 0.6 hours. The duty cycle of the pulsed airflow in this third stage is further adjusted to 1:3. It should be noted that the purpose of this third stage is to lock in the quality of the fish and ensure safety. The higher temperature and lower humidity environment can quickly and thoroughly remove the most firmly bound moisture from the fish, allowing the final product's water activity (Aw) to be stably reduced to 0.75 or below. This inhibits the growth of most microorganisms and achieves the goal of safe storage under non-refrigerated conditions. Simultaneously, strictly controlling the drying time and employing an intermittent airflow method (one-on-three, duty cycle 1:3) minimizes the damage of high temperatures to heat-sensitive nutrients (such as unsaturated fatty acids) and volatile flavor compounds, thus ensuring the final quality of the product.

[0044] Through the synergistic effect of gradient dehydration and pulsed air drying in the three stages described above, a technical effect of balanced dehydration and efficient nutrient retention is achieved. Specifically, the rate of water diffusion from the inside of the fish to the outside and the rate of water evaporation from the surface to the air reach a high dynamic equilibrium, with an evaporation-diffusion rate difference ≤0.3g / (100g·h). After drying, the moisture difference between the inside and outside of the fish meat is ≤2%, resulting in a uniform product texture and overcoming the common problems of external dryness and internal moisture or hardening in traditional processes. In addition, due to precise temperature control and shortened high-temperature exposure time, key nutrients are effectively protected, with EPA and DHA retention rates exceeding 92%.

[0045] S104. During the gradient dehydration and pulsed air drying process, online sampling is performed at multiple preset sampling time points, and the TPA characteristic index of the sample is determined using a texture analyzer.

[0046] It should be noted that the preset sampling time points include: after the first stage, when the drying time in the second stage reaches half of the total drying time, and 4-6 minutes before the end of the third stage. Specifically, the first node is set after the first stage, when the fish has just completed initial mild dehydration and surface condition adjustment; its texture data reflects the effectiveness of the initial drying stage and provides an initial reference for subsequent process decisions in the second stage. The second node is set when the drying time in the second stage reaches half of its preset total time. This node is in the middle of efficient dehydration and can keenly capture the dynamic changes in the fish's texture during the main dehydration process, making it the optimal time for process intervention and preventing deviations from the expected trajectory. The third node is set 4-6 minutes before the end of the third stage, when drying is nearing completion. The detection data at this node is used for a final pre-assessment of the final product's texture quality, providing a final decision opportunity to confirm whether it meets the standards or requires fine-tuning. It should be noted that these three sampling points cover the start-up, core, and end stages of the drying process, enabling a complete and effective characterization of the dynamic evolution of the texture.

[0047] After online sampling, the samples were immediately subjected to TPA testing using a texture analyzer. The TPA test simulates the chewing motion of the human mouth, compressing the sample twice to obtain a series of objectively quantifiable parameters of food texture characteristics. The TPA indicators measurable by the texture analyzer include hardness, springiness, cohesiveness, gumminess, chewiness, and resilience. In this embodiment, preferred TPA characteristics include at least hardness, springiness, and chewiness. Hardness directly reflects the firmness of the dried fish, which is the first sensation a consumer experiences when biting into it; springiness characterizes the dried fish's ability to recover its original shape after deformation under stress, affecting whether the texture is stiff or chewy; chewiness integrates hardness, cohesiveness, and springiness, reflecting the total effort required to chew the dried fish to a swallowable state, and is a core indicator for evaluating overall palatability.

[0048] It should also be noted that, to meet the real-time requirements of online process control, the aforementioned TPA test must be completed within a very short time. Preferably, the entire measurement time, from sample placement to obtaining complete characteristic index data from the texture analyzer, should be ≤30 seconds. This rapid detection capability ensures that process data can be promptly fed back to the control unit.

[0049] S105. Based on the data measured after pretreatment, the process parameters during the vacuum-atmospheric pressure re-osmosis cycle treatment and the gradient dehydration and pulse air drying process, and the TPA characteristic index, the control unit calculates and predicts the texture quality index through a pre-established mapping model between process parameters and TPA texture index.

[0050] It should be noted that, based on the multi-source data collected throughout the entire process in the aforementioned steps, the control unit calculates and predicts the quality of the final product's texture using a built-in model. Specifically, in this embodiment, the control unit is preferably a programmable logic controller (PLC).

[0051] During predictive calculations, the control unit simultaneously receives and integrates real-time and historical data from the following four dimensions. The data measured after pretreatment includes the initial water content, protein, and fat content of the fish meat measured in step S101. The process parameters in the vacuum-atmospheric pressure re-osmosis cycle are the parameters actually used in step S102, including but not limited to low-salt permeate concentration, vacuum pressure, vacuum treatment time, and number of re-osmosis cycles; these parameters determine the penetration state of salt and flavor substances. The process parameters in the gradient dehydration and pulsed air drying process are the process parameters executed and currently being executed in step S103, including the temperature, relative humidity, pulsed air duty cycle, and corresponding processing time implemented in each drying stage. The TPA characteristic indicators are the measured values ​​of hardness, elasticity, chewiness, etc., rapidly measured by a texture analyzer at the latest sampling point in step S104, used for online calibration of the model prediction.

[0052] The control unit pre-establishes and stores a mapping model between process parameters and TPA texture indicators. It should be noted that this model is a mathematical relationship or algorithm trained on a large amount of historical experimental data using methods such as machine learning or multivariate statistical analysis. During the model training phase, the input variables are the data measured after the aforementioned treatments, the complete process data chain including the process parameters during the vacuum-atmospheric pressure re-osmosis cycle treatment and the gradient dehydration and pulsed air drying processes, and the output variable is the stable texture indicator of the corresponding batch of finished product as determined by TPA. This model learns and characterizes the complex nonlinear relationship between specific raw materials and the final texture result obtained after specific salting and drying processes.

[0053] During processing, the control unit inputs real-time multi-source data into the trained mapping model. Based on the current raw material state, the executed process path, and the latest measured texture feedback (by comparing the measured value with the model's current prediction to correct the prediction trajectory), the model runs its internal algorithm to calculate and output a comprehensive quantitative value, namely the Predicted Texture Quality Index (TQI_pred). This index is not a single TPA indicator, but rather a single scalar value formed by weighting multiple key texture parameters (such as hardness, elasticity, and chewiness). Its significance lies in the quantitative prediction of the overall texture quality that this batch of products can ultimately achieve under the current process path.

[0054] S106. Compare the predicted texture quality index with the preset target texture quality index. When the absolute difference between the two texture quality indices is greater than a set threshold, calculate the process parameter correction value for at least one stage in the dehydration and pulse air drying process based on the process parameters and the TPA texture index mapping model.

[0055] Specifically, the control unit compares the calculated predicted texture quality index (TQI_pred) with a pre-set target texture quality index (TQI_target) stored in the system in real time. TQI_target is a quantified ideal taste template value, based on the best overall texture score determined from historically best batch products, samples with the highest market acceptance, or experiments correlated with extensive sensory evaluation and TPA analysis. This value represents the quantitative standard for texture of products with optimal palatability (moderate firmness, good elasticity, and good chewiness) that this method aims to consistently produce.

[0056] The comparison is based on the absolute difference between the two index values. This embodiment sets a threshold for this difference, preferably 5%. It should be noted that this 5% threshold is set based on a comprehensive consideration of high standards for product texture consistency and the fluctuation range of traditional processes. Traditional experience-based processes can have batch-to-batch textural differences exceeding ±15%. Setting the threshold to 5% means the system requires compressing production fluctuations to a level far below traditional levels, thereby ensuring high product quality stability. Simultaneously, this threshold provides reasonable tolerance for system intervention, avoiding frequent and unnecessary adjustments due to minor random fluctuations, and ensuring the smoothness of the production process.

[0057] Specifically, when the system determines that |TQI_pred-TQI_target|≤5%, it indicates that the prediction result based on the current process parameters is very close to the ideal target, and the processing can continue along the predetermined path without intervention; when the system determines that |TQI_pred-TQI_target|>5%, it determines that the current process path may cause the final product to deviate from the ideal template, and active intervention is necessary.

[0058] In cases requiring intervention, the system will activate a reverse calculation mechanism. At this point, the control unit will invoke the aforementioned process parameter and TPA texture index mapping model, but in the opposite direction to the prediction (forward). The system uses TQI_target as the input target value, combining currently collected raw material data, executed salting and partial drying process parameters, and real-time TPA characteristic indicators, requiring the model to solve in reverse. To ensure the final predicted value approaches TQI_target, adjustments should be made to which key process parameters in the remaining unexecuted drying process (at least one stage, such as the later part of the second stage or the third stage), and in what direction and magnitude. The model uses its built-in algorithm to deduce one or more process parameter correction values ​​in reverse. For example, increasing the temperature of the second stage by ΔT (e.g., +2℃), adjusting the pulse air duty cycle of the third stage to a new ratio (e.g., from 1:3 to 1:2.5), or decreasing the relative humidity of the final drying stage by ΔRH, etc. These correction values ​​are output as explicit instructions, forming the direct basis for the next step of precise control.

[0059] S107. Adjust the process parameters of the corresponding stage based on the process parameter correction value, and return to continue executing gradient dehydration and pulse air drying. Repeat the subsequent steps starting from the online sampling until the absolute difference between the two texture quality indices is less than or equal to the set threshold, thus completing the production of dried fish.

[0060] Specifically, after generating the process parameter correction value in step S106, the control unit issues instructions to the corresponding drying equipment actuators (such as heaters, humidifiers, variable frequency fans, etc.) to adjust the process parameters of the drying stage (such as the later stage of the second stage or the third stage) indicated by the correction value to the new set value in real time. For example, if the correction instruction is "increase the temperature of the second stage by 2°C, and at the same time adjust its pulse air duty cycle from 1:1 to 1.2:1", the system will immediately adjust the relevant equipment so that the subsequent drying environment of this stage operates according to these new parameters.

[0061] It should be noted that the processing flow does not end after this parameter adjustment. Instead, the system will return to the gradient dehydration and pulsed air drying process described in S103 and continue the subsequent drying process from the adjustment point. Simultaneously, to ensure the adjusted effect meets expectations, the system will reactivate and repeat the series of monitoring and decision-making steps that began with online sampling in S104. Thus, at subsequent preset sampling points (or sampling points temporarily added to monitor the adjustment effect), online sampling, rapid TPA determination, multi-source data integration, and calculation of a new predicted texture quality index (TQI_pred') based on a mapping model will be performed again, and this new predicted value will be compared with the target value (TQI_target) once more.

[0062] This creates a closed-loop feedback loop of execution-monitoring-evaluation-re-decision. The system will continue this iterative cycle until, at a certain monitoring point, the absolute difference between the newly calculated predicted texture quality index (TQI_pred') and the target texture quality index (TQI_target) is less than or equal to the set threshold (e.g., 5%). At this point, it is determined that the current process path has successfully guided the product quality towards the ideal target range, and no further intervention is required. Subsequently, the system will allow or control the drying process to continue running to the preset final end point, thereby completing the production of the entire batch of dried fish.

[0063] The method provided in this embodiment, by integrating low-salt vacuum-re-osmosis, three-stage gradient pulse drying, TPA online detection, and intelligent closed-loop control based on a mapping model, produces a series of synergistic beneficial effects. Firstly, regarding health benefits, the product's salt content has been significantly reduced from 8-12% using traditional processes to 1.5-3.5%, meeting the modern market's demand for low-sodium healthy foods. Secondly, in terms of nutrient and flavor preservation, the unique gradient drying and pulsed air delivery strategy, combined with the use of natural antioxidants, ensures that the retention rate of heat-sensitive core nutrients EPA and DHA reaches over 92%, effectively locking in the original fresh flavor of the fish and solving the problem of nutrient and flavor loss in traditional processing. Furthermore, regarding quality uniformity and standardization, intelligent control driven by real-time feedback signals based on the TPA index has stably controlled the batch-to-batch textural differences from over 15% in traditional processes to within 5%, achieving a high degree of consistency in product hardness, elasticity, and chewiness, laying the foundation for large-scale production. Finally, in terms of production efficiency, this data-driven closed-loop model replaces the trial-and-error method relying on human experience, enabling automatic optimization and real-time correction of process parameters, significantly improving production efficiency and resource utilization while reducing energy consumption.

[0064] To better illustrate this application, a specific embodiment is also provided.

[0065] Specific Implementation Examples: Specific Process Parameters and Online Control Examples

[0066] It should be noted that this embodiment is based on Figure 1 The process shown provides a complete set of implementation data, specifically demonstrating how the method of this application achieves products with low salt content, high retention rate, and stable texture.

[0067] Specifically, 30 live *Sinocyclocheilus scoparia* were selected, with an average body length of 9.72±1.5cm and an average weight of 6.2±2.8g. After stunning, scaling, eviscerating, and cleaning, the fish were dissected and cut into sections. Samples were taken to determine the basic components, with average values ​​of: water content 78.07±0.5%, crude protein 17.96±0.3%, and crude fat 2.43±0.2%.

[0068] A 3.5% (w / w) saline solution was prepared, with the addition of 0.05% tea polyphenols and 1% seaweed extract. Fish fillets were immersed in the permeate solution and placed in a sealed permeation tank. A vacuum-atmospheric pressure re-osmosis cycle was performed: the vacuum phase was at 70 kPa for 10 min; then atmospheric pressure was restored, and re-osmosis was performed for 10 min. This cycle was repeated twice. After treatment, samples were taken for analysis. The water content of the fish meat slightly increased to 78.54%, and the presence of fat resulted in a decrease in crude fat to 0.96%, indicating that the permeate solution had initially penetrated and replaced some lipids.

[0069] The permeation-treated fish fillets were evenly spread on drying trays and then placed into a temperature- and humidity-controlled pulse-flow dryer. The drying process was strictly carried out in the following three stages, and the real-time parameter records are shown in Table 1:

[0070] Table 1 Real-time parameter records

[0071] Drying stage Temperature range (°C) Humidity range (%) Duration Pulse air supply duty cycle (air supply: intermittent) Moisture content at the end of the stage (%) Phase 1 22.5–29.7 83.2–74.8 2.5h 30s:60s (1:2) 64.7 Phase Two 62.3–69.2 59.7–55.3 1.5h 30s:30s (1:1) 42.2 Phase Three 77.5–82.7 53.8–46.5 0.5h 30s:90s (1:3) 18.1

[0072] After drying, the water activity (Aw) of the finished product was measured and found to be 0.72 ± 0.02, which meets the safe storage requirement of ≤0.75.

[0073] During the drying process, online sampling was conducted at the following three preset time points, and TPA testing was completed within 25 seconds using a texture analyzer: at the end of the first stage (t=2.5h), halfway through the second stage (t=3.25h), and 5 minutes before the end of the third stage (t=4.55h). The measured TPA characteristic indicators (hardness, elasticity, chewiness) were transmitted to the control unit in real time.

[0074] The control unit (PLC) has a built-in process parameter and TPA (Total Texture Index) mapping model. Based on real-time collected process data and TPA characteristic indicators, it calculates the current predicted texture quality index (TQI_pred). In this operation, at t=3.25h, the model predicted TQI_pred to be 87.5, and the absolute difference from the preset target value (TQI_target=90.0) was 2.5 (2.8%), which is less than the set threshold of 5%. Therefore, the process was judged to be operating normally, and no parameter correction was triggered. The drying process continued until completion according to the original set parameters.

[0075] Multiple indicators were tested on the dried fish product after drying, and the results are as follows:

[0076] Sodium content: The sodium content of three batches of samples was determined by atomic absorption spectrometry. The sodium content was 685.3, 705.8 and 699.7 mg / 100g (average 696.9 mg / 100g), which is equivalent to a salt content of about 1.77%, which is within the low salt design range of 1.5% to 3.5%.

[0077] EPA / DHA retention rate: The total EPA and DHA content in the finished product was determined to be 4.33±0.06 g / 100g using gas chromatography. Referring to the typical value in literature on fresh live Gynostemma pentaphyllum (EPA+DHA approximately 4.70 g / 100g), the retention rate was calculated to be 92.1%, which meets the requirement of >92%.

[0078] Texture analysis: The finished product underwent TPA (Total Physical Aspect Ratio) testing. The average values ​​of key indicators were: hardness 7207.27±3874.31g, elasticity 0.81±0.10, and chewiness 3522.98±1766.03mJ. The intra-batch coefficient of variation (CV) for the main texture parameters (hardness and chewiness) was ≤4.5%, meeting the product requirement of ≤5%.

[0079] Sensory evaluation: A blind evaluation was conducted by a panel of 10 people. The finished products scored between 6 and 10 points (out of 10) in terms of color, texture, aroma, taste and saltiness, indicating that the products have the characteristics of natural color, firm texture, rich aroma, appropriate saltiness and good chewiness.

[0080] This embodiment demonstrates that dried stream fish with low salt content, high retention of core nutrients, uniform texture, and excellent sensory quality can be stably produced in approximately 4.5 hours.

[0081] Furthermore, in order to clearly demonstrate the significant advantages of each core process step of this application compared to traditional or alternative methods, the following series of comparative experiments were designed and conducted.

[0082] I. Comparison of the effects of salt penetration process

[0083] Experimental group: The method of this application was adopted, namely the parameters described in the specific embodiment (3.5% low salt permeate, 70kPa vacuum-atmospheric pressure re-osmosis twice).

[0084] Comparative Example 1 (Traditional high-salt static soaking): A 10% high-salt solution was used for static soaking at room temperature for 2 hours (the total treatment time is similar to that of this application).

[0085] Comparative Example 2 (simple low-salt static soaking): 3.5% low-salt solution (without additives) was used for static soaking at room temperature for 2 hours.

[0086] The results are shown in Table 2:

[0087] Table 2. Salt Osmosis Comparison Table

[0088] Group Sodium content of the finished product (mg / 100g) <![CDATA[Salt penetration uniformity (Cl content difference between the surface and the interior)]]> - > Coefficient of variation (CV) of hardness in finished TPA experimental group 696.9 ≤0.2% 4.5% Comparative Example 1 2150.5 ≤0.8% 12.7% Comparative Example 2 580.3 ≥2.5% 18.3%

[0089] Please refer to Table 2. The sodium content of the experimental product is only 32.4% of that of Comparative Example 1 (traditional process), achieving a salt reduction of over 65%. The salt permeation uniformity of the experimental group is significantly better than that of Comparative Example 2, proving that the vacuum-atmospheric pressure re-osmosis cycle can effectively overcome the permeation resistance at low salt concentrations and achieve uniform salt distribution. The texture hardness CV value of the experimental group is much lower than that of the two comparative examples, indicating that the permeation process of this application lays the foundation for subsequent drying to form a uniform texture.

[0090] II. Comparison of the effects of gradient dehydration and pulsed air drying processes

[0091] Experimental group: The method of this application was adopted, namely the three-level gradient pulse drying parameters described in Example 2.

[0092] Comparative Example 3 (Constant Temperature Drying): The temperature was kept constant at 60°C with continuous air supply, and the drying was carried out until the same endpoint water activity (Aw≈0.72) was achieved.

[0093] Comparative Example 4 (gradient temperature continuous drying): The same three-stage temperature setting as the experimental group was used, but the air supply was changed to continuous, without pulse intermittent.

[0094] The results are shown in Table 3:

[0095] Table 3 Comparison of Gradient Dehydration and Pulse Air Drying

[0096] Group Total drying time (h) EPA / DHA retention rate (%) The difference in moisture content between the surface and interior of the fish meat (%) Does the surface have a hardened crust / cracks? experimental group 4.5 92.1 1.8 no Comparative Example 3 5.0 78.5 8.5 Yes (obviously a hard shell) Comparative Example 4 4.3 85.2 3.2 Slight cracking

[0097] Referring to Table 3, the experimental group exhibited significantly higher EPA / DHA retention rates compared to Comparative Example 4, with similar drying times. This demonstrates that the pulsed airflow mode, through intermittent rehumidification, reduces the continuous damage to heat-sensitive nutrients caused by high temperatures. The experimental group also showed the smallest surface-to-internal moisture difference and intact appearance, indicating that the synergistic effect of gradient temperature and pulsed airflow effectively coordinated the rates of moisture evaporation and internal diffusion, preventing excessive surface water loss leading to a hard crust or cracking, and achieving balanced dehydration.

[0098] III. Verification of the effectiveness of TPA online closed-loop control

[0099] Experimental group (closed-loop control, n=5 batches): The method of this application was fully implemented, including online TPA detection and model-based real-time parameter correction.

[0100] Comparative Example 5 (open-loop control, n=5 batches): The same initial raw materials and preset process parameters as the experimental group were used, but the online TPA detection and feedback correction function was turned off, and the operation was carried out completely according to the preset program.

[0101] The experiment showed that the final texture of each batch in the experimental group was highly consistent, with a batch-to-batch CV value of only 1.34%, far lower than the 5.56% of the comparative example 5, and a pass rate of 100%. This proves that closed-loop control based on TPA online detection can effectively compensate for minor fluctuations in raw materials and environmental interference, ensuring that the texture of different batches of products remains stable within the preset high standard range.

[0102] Example 2

[0103] Corresponding to the aforementioned embodiment of a traditional method for making dried river fish based on TPA texture analysis, this application also provides a traditional dried river fish product based on TPA texture analysis, wherein the dried fish product has a sodium content of 1.5% to 3.5%, a texture variation coefficient ≤5%, an EPA / DHA retention rate >92%, a water activity Aw ≤0.75, and a moisture difference between the surface and interior of the fish meat ≤2%.

[0104] For details, please refer to the previous introduction; they will not be repeated here.

[0105] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A traditional method for making dried stream fish based on TPA texture analysis, characterized in that, The method includes: After pretreatment of fresh stream fish, the water content, protein and fat content of the fish meat were measured. The pretreated fish meat is immersed in a low-salt permeate solution and subjected to vacuum-atmospheric pressure re-osmosis circulation treatment. The fish meat, after being treated by vacuum-atmospheric pressure re-osmosis circulation, is subjected to at least three stages of gradient dehydration and pulsed air drying. During the gradient dehydration and pulsed air drying process, online sampling was carried out at multiple preset sampling time points, and the TPA characteristic index of the samples was measured using a texture analyzer. Based on the data measured after pretreatment, the process parameters during the vacuum-atmospheric pressure re-osmosis cycle treatment and the gradient dehydration and pulse air drying process, and the TPA characteristic index, the control unit calculates and predicts the texture quality index through a pre-established mapping model between process parameters and TPA texture index. The predicted texture quality index is compared with the preset target texture quality index. When the absolute difference between the two texture quality indices is greater than a set threshold, the process parameter correction value for at least one stage of the dehydration and pulse air drying process is calculated in reverse based on the process parameters and the TPA texture index mapping model. Based on the process parameter correction value, adjust the process parameters of the corresponding stage, and return to continue executing gradient dehydration and pulse air drying. Repeat the subsequent steps starting from the online sampling until the absolute difference between the two texture quality indices is less than or equal to the set threshold, thus completing the production of dried fish.

2. The method according to claim 1, characterized in that, The process of immersing the pretreated fish meat in a low-salt permeate solution for vacuum-atmospheric pressure re-osmosis circulation includes: The pretreated fish meat is placed in a low-salt permeate solution with a mass concentration of 1.5% to 3.5%, and treated under vacuum conditions of 60 kPa to 80 kPa for 5 to 15 minutes. Then, it is restored to normal pressure for re-osmosis. The vacuum-normal pressure re-osmosis cycle is performed 2 to 3 times.

3. The method according to claim 1, characterized in that, The low-salt permeate contains at least one of a natural antioxidant and a flavor enhancer; the natural antioxidant is tea polyphenols, and the flavor enhancer includes seaweed and seaweed extract.

4. The method according to claim 1, characterized in that, The gradient dehydration and pulsed air drying process, which involves at least three stages, includes a first stage, a second stage, and a third stage performed sequentially. The first stage includes drying for 2 to 3 hours at a temperature of 20°C to 30°C and a relative humidity of 75% to 85%, during which a pulse air supply mode is used, and the duty cycle of the pulse air supply is 1:

2. The second stage includes drying for 1 to 2 hours at a temperature of 60°C to 70°C and a relative humidity of 55% to 60%, during which a pulse air supply mode is used, and the duty cycle of the pulse air supply is 1:

1. The third stage includes drying for 0.4 to 0.6 hours at a temperature of 75°C to 85°C and a relative humidity of 45% to 55%, during which a pulse air supply mode is used, and the duty cycle of the pulse air supply is 1:

3.

5. The method according to claim 4, characterized in that, After the third stage is completed, the water activity Aw of the fish meat is ≤0.

75.

6. The method according to claim 4, characterized in that, The preset multiple sampling time points include: after the first stage ends, when the drying time of the second stage reaches 1 / 2 of the total drying time, and 4-6 minutes before the end of the third stage.

7. The method according to claim 4, characterized in that, After three stages of gradient dehydration and pulsed air drying, the evaporation-diffusion rate difference is ≤0.3g / (100g·h), the moisture difference between the surface and interior of the fish meat is ≤2%, and the EPA / DHA retention rate is >92%.

8. The method according to claim 1, characterized in that, The set threshold is 5%.

9. The method according to claim 1, characterized in that, The TPA characteristic indicators include at least hardness, elasticity and chewiness, and the measurement time of the texture analyzer is ≤30s.

10. A traditional stream fish dried product based on TPA texture analysis, characterized in that, The dried fish product is prepared based on the method described in any one of claims 1-9, and the dried fish product has a sodium content of 1.5% to 3.5%, a texture variation coefficient of ≤5%, an EPA / DHA retention rate of >92%, a water activity Aw of ≤0.75, and a moisture difference between the surface and interior of the fish meat of ≤2%.

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