A dynamic electric heating method for surimi based on electric property change

Abstract

The present application relates to a kind of dynamic power heating method of surimi based on electrical property change, specifically includes the following steps: the fish surimi obtained after fish physical treatment is placed in heating container with parallel polar plate, and power heating;Real-time detection temperature and electrical parameter change data, determine the gel strength of fish surimi at preset temperature point and time interval point, and send data to PC end for processing, generate mathematical model of the relationship between electrical parameter change data and fish surimi gel process;Fish surimi is placed in the above heating container, and fish surimi is heated using voltage gradient from low to high, preset enough gel time, real-time detect electrical parameter change during heating process, obtain gel strength change data according to the mathematical model obtained in step (1), judge gel state, real-time adjust voltage size and heating time based on gel state, until final heating is completed.The present application has lower cost, high quality of fish surimi, and has broad market application prospect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of food technology processing, in particular to a dynamic electric heating method for surimi based on electric property change. BACKGROUND

[0002] In recent years, freshwater fish resources are increasingly abundant, and the optimization of freshwater fish resources is a suitable way to process surimi and its products. Surimi products have the advantages of "four lows and one high", that is, low fat, low cholesterol, low heat and low salt, and high protein nutrition, which meets people's nutritional and healthy consumption needs. The gel strength of surimi is an important indicator for evaluating the quality of surimi. The gel formation process of surimi mainly includes three stages: gelation, gel degradation and fish cake formation. Gelation refers to the formation of a relatively loose network structure of myosin and actin molecules before 50 DEG C, from sol to gel. Gel degradation refers to the formation of a broken network structure at 50 DEG C ~ 70 DEG C, and the decomposition of myosin caused by the increase of endogenous tissue protease activity, resulting in a decrease in gel strength. Fish cake formation is at a temperature above 75 DEG C, and in this state, the fish gel has formed a stable three-dimensional network structure, which has reached the best gel state. However, the gel formation characteristics of surimi are affected by fish species, age, season, freshness and processing technology, so relying on temperature to judge the gel state has certain instability. Moreover, relying on manual experience, the quality of surimi gel obtained by using temperature parameters for segmented heating treatment fluctuates greatly.

[0003] In the heat treatment of surimi products, the traditional water bath heating method has a long heating time and a long gel degradation stage, which affects the gel quality. Many enterprises now use electric heating technology to heat treat surimi products. Electric heating is a processing method that directly converts electrical energy into heat energy by using the resistance of food itself. When the electric current passes through the food material, the internal Joule heat is generated due to the inherent impedance characteristics of the food material, thereby achieving the effect of heating. Compared with traditional heating, electric heating has the advantages of easy temperature control, no heating surface, environmental friendliness, high electric heating efficiency of more than 90% and uniform heating, etc. Electric heating can quickly pass through the gel degradation temperature range and improve the gel properties by using its fast heating characteristics. However, the instantaneous heating characteristics of electric heating can quickly pass through the gel degradation range and improve the gel properties of surimi, but it can also quickly pass through the gelation stage of surimi, which affects the unfolding of myofibrillar proteins and the stability of the three-dimensional network structure. Therefore, it is necessary to change the heating parameters of electric heating according to the stage characteristics of surimi during heating to achieve segmented heating.

[0004] Traditional method for determining gel strength is to heat to a certain temperature point, or in the case of temperature determination, after a period of time, then using a texture analyzer (texture analyzer) to destructive testing of surimi gel samples, and can only be used to determine the different stages of the method to determine the quality of surimi gel changes, can not real-time monitoring in the heating process due to the changes in the network structure of the gel caused by surimi gel characteristics change.

[0005] Secondly, in the heating process, the temperature measuring probe placed in the surimi sample will also cause damage to the surimi sample, resulting in sample waste, and the feedback temperature data has a certain hysteresis, which is not conducive to the determination of the heating state of surimi. SUMMARY

[0006] In view of the technical problems in the background art, the present application provides a dynamic power heating method for surimi based on the change of electrical properties.

[0007] The technical scheme adopted by the present application is: a dynamic power heating method for surimi based on the change of electrical properties, specifically comprising the following steps: placing surimi obtained after physical treatment of fish into a heating container with parallel electrode plates and heating by power supply; detecting temperature and electrical parameter change data in real time, determining the gel strength of surimi at preset temperature points and time interval points, and sending the data to a PC end for processing to generate a mathematical model of the relationship between electrical parameter change data and surimi gel process; placing surimi into the above-mentioned heating container, heating the surimi with a low-to-high voltage gradient, setting sufficient gel time to make myofibrillar proteins in surimi fully unfold and form a three-dimensional network structure, detecting electrical parameter changes in real time during the heating process, obtaining gel strength change data according to the mathematical model obtained in step (1), judging the gel state, and adjusting the voltage size and heating time in real time based on the gel state until the final heating is completed.

[0008] Preferably, the heating container is a lidless cube composed of PVC plates, and two grooves are cut in the interior to place the electrode plates in parallel, providing a substantially uniform electric field for heating surimi, and the electrode plates are made of food-grade 304 stainless steel.

[0009] Preferably, the surimi is heated by a high-frequency power supply, which is composed of a rectifying device, an inverting device, a detecting device and a control device, and outputs a bipolar square wave voltage with adjustable voltage amplitude, frequency and waveform duty cycle.

[0010] Preferably, an impedance analyzer or other electrical parameter measuring device is used to measure the change of electrical parameter values of surimi with temperature during the heating process, and the data is fed back to the connected PC end in real time.

[0011] Compared with the prior art, the method disclosed by the application can realize online nondestructive detection of the gelatinization state of surimi by monitoring the dynamic change value of the electric parameter of surimi in the process of electric heating, and dynamically adjust the heating condition according to the gelatinization state. Meanwhile, the high-frequency electric heating power supply with adjustable output voltage amplitude, frequency and duty cycle is used to heat treat the surimi, so as to effectively prevent the adhesion of the electrode plate and the pollution of the surimi, and the characteristic of fast heat production of the electric heating is used to quickly pass through the gelatinization deterioration interval of the surimi. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 It is a dynamic electric heating structure diagram of surimi based on the change of electric characteristics in the application.

[0013] Figure 2 It is a working flow chart of a dynamic electric heating method of surimi based on the change of electric characteristics.

[0014] Figure 3 It is a curve diagram of the change of impedance value with temperature in the heating process.

[0015] Figure 4 It is a curve diagram of the change of surimi gel strength with temperature in the heating process.

[0016] Figure 5 It is a curve diagram of the relationship between the change of surimi gel strength and the change of impedance value at each temperature in the heating process.

[0017] In the figure: 1. high-frequency heating power supply; 2. heating container; 3. electrode plate; 4. impedance analyzer; 5. PC end. DETAILED DESCRIPTION

[0018] The application will be described in detail below in combination with specific implementation cases.

[0019] As Figure 2 described, it is a working flow chart of the method. After the fish is killed and washed, the head and internal organs are removed, and after the meat is picked, rinsed and dehydrated, 2%-3% salt is added for grinding or chopping to obtain surimi, which is filled into a PVC material heating container 2. Two parallel electrode plates 3 are placed along the clamping grooves on both sides of the heating container, the electrode plates 3 are connected with the high-frequency heating power supply to provide electric energy for the load, and the electric resistance of the surimi itself is used to achieve the purpose of heating.

[0020] The surimi is heat treated by electric heating. On the one hand, the instant heating characteristic of electric heating can make it quickly pass through the gelatinization deterioration stage, and on the other hand, electric heating can quickly inactivate endogenous tissue proteases to avoid gelatinization deterioration, thereby improving the gelatinization characteristics of the surimi.

[0021] Establishing mathematical model: In the heating process, the temperature change data is collected by the temperature measuring fiber in real time, the impedance analyzer 4 is used to determine the change of the electric parameter value of the surimi with temperature in the heating process, and the data is fed back to the PC end 5 in real time. At each heating to a certain temperature point or interval, the surimi sample is taken out for determination of gel strength, the electric parameter value corresponding to different gel states is obtained, and the electric parameter distribution interval of the three stages of gelation-gel deterioration-fish cake in the heating process is judged. According to the collected different gel strength and electric parameter, the mathematical model of the relationship between the electric parameter and the surimi gel process is obtained.

[0022] The mathematical model obtained is input into the computer, the surimi is heated at a lower heating rate, i.e. low voltage gradient, and the impedance analyzer feeds back the electric parameter value of the surimi to the PC end 5 in real time, the corresponding gel strength of the electric parameter value is calculated, the gel state of the surimi gel at this time is judged according to the change of the gel strength, when the trend of the gel strength begins to decrease, it is judged that the surimi gel enters the gel deterioration stage, then the voltage is quickly adjusted, the voltage gradient is increased, and it is quickly passed through the gel deterioration stage. That is, the voltage size is dynamically adjusted to control the heating rate or the heating time is adjusted to control the heating endpoint, so as to realize the optimization of the quality of the surimi gel.

[0023] The method can collect the electric characteristics of the surimi in real time to monitor the gel state of the surimi, dynamically adjust the voltage size and the heating time, and thus obtain the optimal quality of the surimi product under the heating condition.

[0024] The method can reduce the sample loss caused by the surimi gel strength detection device and the surimi gel in the determination process, and reduce the cost.

[0025] The heating container 2 adopts a coverless square cylinder composed of PVC plates, two grooves are cut in the inside for convenient parallel placement of the electrode plate 3, and a basically uniform electric field is provided for heating the surimi. The heating electrode plate is made of 304 stainless steel.

[0026] The high-frequency heating power supply 1 is composed of rectifier device, inverter device, detection device and control device, and mainly outputs bipolar square wave voltage with adjustable voltage amplitude, frequency and waveform duty cycle. High-frequency heating can effectively inhibit the adhesion of the electrode plate and avoid pollution to the electrode plate and the surimi.

[0027] The method can determine the electric characteristics of the surimi in different heating stages, such as conductivity, resistance, inductance, capacitance and other parameters. While achieving the purpose of rapidly heating the surimi, the method can also monitor the gel state of the surimi on line and nondestructively according to the real-time collection of the electric characteristics, dynamically adjust the power heating condition, and optimize the quality of the surimi gel.

[0028] As Figure 1As shown, the system used in the method of the present application can mainly consist of a high-frequency heating power supply 1, an impedance analyzer 4, a heating container 2, and a PC terminal 5.

[0029] The present application will be described in detail below with reference to Figure 3 --5, taking surimi made of carp as an example.

[0030] After being slaughtered, the fresh carp is washed, beheaded, and eviscerated, and then subjected to meat picking, rinsing, and dehydration. Then, 2% of salt by mass is added and chopped for 2 minutes. The moisture content of the surimi is adjusted to 78% by adding ice. Figure 1 As shown, the surimi is filled into a heating container made of PVC, and two parallel electrode plates 2 are placed along the clamping grooves on both sides of the heating container. The electrode plates 2 are connected to the high-frequency heating power supply 1 to provide electric energy for the load. The surimi sample is heated to 90℃ at a voltage gradient of 3.3V / cm (U=50V) at a frequency of 10kHz.

[0031] During the heating process, the temperature change data are collected in real time by using a temperature measuring optical fiber, and the impedance value of the surimi during the heating process is measured by using the impedance analyzer 4, so as to generate a curve graph as shown in Figure 3 The data are fed back to the PC terminal 5 in real time. During the heating process, the surimi that has been heated is taken out every 10℃, quickly placed in ice water, and then stored in a 4℃ refrigerator for 12h to obtain a surimi gel sample. The gel strength of the surimi gel is measured by using a texture analyzer (gel strength=breaking force x breaking distance). When measuring, a 25mm cube sample is placed on the workbench of the texture analyzer, a 5mm diameter spherical probe (P / 0.5) is used, the trigger force is 5g, the measurement speed is set to 1mm / s, and the pressing distance is 15mm. The gel strength of the surimi heated to different temperature points is obtained. Multiple samples are set at each temperature point, and the average value of the parameters of multiple samples is taken. The change of the gel strength is shown in Figure 4 As can be seen from the graph, during the initial stage of the heating process, the gel strength of the surimi increases with the increase of the temperature. The gel strength decreases at 50~60℃, indicating that gel deterioration occurs at this temperature range.

[0032] According to the collected gel strength and impedance value at different temperatures, a mathematical model of the relationship between the impedance and the gel strength of the surimi is obtained. The relationship between the gel strength and the impedance value of the surimi at different temperatures during the heating process is shown in Figure 5

[0033] ​The obtained mathematical model is input into a computer, and the surimi is heated at a voltage gradient of 3.3 V / cm at a frequency of 10 kHz, and a lower heating rate is used to maintain the low-temperature stage for a period of time, so that the myofibrillar proteins in the surimi are fully unfolded, and the formation of the three-dimensional network structure is facilitated. During the heating process, the impedance analyzer 4 feeds back the impedance value to the PC end 5 in real time, calculates the corresponding gel strength under the impedance value, and monitors the gel state at this time. When the heating time is 90±3.56 s, the impedance value is 7.38Ω, the gel strength calculated according to the impedance value decreases, and it is judged that the gel deterioration starts at this time. The heating power voltage is quickly adjusted to 200 V (voltage gradient 13.3 V / cm), the heating rate is increased, and the interval is quickly passed. When the impedance value reaches about 6.35Ω, the surimi gel has formed a stable three-dimensional network structure, and the heating is stopped. Therefore, only the impedance value collected in real time is needed, the corresponding gel strength is obtained according to the above relationship, the surimi gel state in the heating process is monitored, the voltage size is adjusted to control the heating rate or the heating time is adjusted to control the heating endpoint, so as to realize the optimization of the surimi gel quality.

[0034] The method of the application combines the current heating electrode and the measurement electrode, monitors the surimi gel state in real time according to the feedback electric parameter value while quickly heating the surimi, and dynamically adjusts the current heating condition. The method not only reduces the equipment cost but also avoids sample damage caused by detection, and is conducive to popularization and use.

[0035] Although the specific embodiments of the application are described above, those skilled in the art should understand that these are only illustrative, and various changes or modifications can be made to these embodiments without departing from the principles and essence of the application, therefore, the protection scope of the application is defined by the appended claims.

Claims

1. A method for dynamic electric heating of surimi based on changes in electrical properties, characterized in that: The following steps are involved: (1) Establishing a mathematical model: The surimi obtained after physical treatment of the fish is placed in a heating container with parallel electrodes and heated by electricity; the temperature and electrical parameter change data are detected in real time, and the gel strength of the surimi is measured at preset temperature points and time intervals. The change of the electrical parameter values ​​of the surimi with temperature during the heating process is measured using an impedance analyzer, and the data is sent to the PC for processing to generate a mathematical model of the relationship between the electrical parameter change data and the surimi gel process; (2) Electric heating: The surimi is placed in the above-mentioned heating container and heated with a voltage gradient from low to high. A sufficient gelation time is preset to allow the myofibrillar protein in the surimi to fully unfold and form a three-dimensional network structure. The changes in electrical parameters during the heating process are detected in real time. According to the mathematical model obtained in step (1), the gel strength change data is obtained to judge the gel state. The voltage and heating time are adjusted in real time based on the gel state until the final heating is completed.

2. The method for dynamic electric heating of surimi based on electrical characteristic changes according to claim 1, characterized in that: The heating container is a uncovered cube made of PVC board, with two grooves cut inside and parallel plates placed to provide a basically uniform electric field for heating the surimi. The plates are made of food-grade 304 stainless steel.

3. The method for dynamic heating of surimi based on electrical characteristic changes according to claim 1, characterized in that: The fish paste is heated by a high-frequency power supply, which consists of a rectifier, an inverter, a detection device and a control device, and outputs a bipolar square wave voltage with adjustable voltage amplitude, frequency and waveform duty cycle.

4. The method for dynamic electric heating of surimi based on electrical characteristic changes according to claim 1, characterized in that: When measuring the gel strength of the surimi, the surimi in multiple heating containers is taken as samples at the preset temperature points and time intervals, and the average value of the surimi gel strength parameters of the multiple samples is taken.

5. The method for dynamic electric heating of surimi based on changes in electrical characteristics according to any one of claims 1 to 4, characterized in that: The method is mainly implemented by a combination of a high-frequency heating power supply, an impedance analyzer, a heating container, and a PC terminal, which can be combined into a dynamic electric heating system for surimi based on changes in electrical characteristics.

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