A method for improving the oxidative stability and freeze-thaw stability of surimi products by using natural oil bodies

Abstract

This invention discloses a method for improving the oxidative and freeze-thaw stability of surimi products using natural oils, comprising the following steps: Oil preparation: Oil-containing plant seeds are crushed, soaked, and centrifuged to obtain the upper oil layer, thus obtaining a natural oil; Chopping: Surimi raw materials are sequentially air-chopped and salt-chopped in a chopper at 0℃~10℃, and then 0.1%~15% of the natural oil by weight of the surimi raw materials is added and mixed to obtain an emulsified slurry; Shaping and heat-induced gelation: The emulsified slurry is shaped, and gelation is induced by a first-stage heating and a second-stage heating, followed by cooling. This invention solves the problems of easy oxidation and deterioration and poor freeze-thaw stability of traditional surimi products, significantly improving freeze-thaw stability and oxidative stability, and is suitable for developing high-quality surimi products with long shelf life.

Description

Technical Field

[0001] This invention relates to the field of aquatic product processing technology, and in particular to a method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils. Background Technology

[0002] Surimi products are widely popular among consumers due to their high protein and rich nutritional content, making them an important product in the aquatic product processing industry. Traditional surimi products require the addition of a suitable amount of oil (mainly lard) to improve taste and flavor. However, surimi products often undergo repeated freeze-thaw cycles during cold chain logistics and storage, which easily leads to oil oxidation within the system. This further induces protein denaturation and aggregation, resulting not only in an unpleasant rancid taste but also a significant decrease in the water-holding capacity of the gel network, ultimately reducing product quality. Although existing technologies can improve this by adding food additives (antifreeze agents, antioxidants) and artificial pre-emulsification systems, these methods also present challenges such as complex processes and incompatibility with current natural, green, and healthy product concepts.

[0003] Plant oils are natural components in plant seeds that store oils. Due to their unique ternary structure of "triglyceride core - phospholipid monolayer - oil body protein", they have excellent emulsification stability, anti-aggregation and antioxidant properties, and have broad application prospects in food, medicine, cosmetics and skin care products. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for improving the oxidative stability and freeze-thaw stability of surimi products using natural plant oils. This invention solves the problems of easy oxidation and deterioration and poor freeze-thaw stability of surimi products by adding 0.1% to 15% of natural oils by weight of the surimi, making it suitable for developing high-quality surimi products with long shelf lives.

[0005] The objective of this invention is achieved through the following technical solution:

[0006] This invention provides a method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils, comprising the following steps:

[0007] Oil preparation: The oil-bearing seeds of plants are crushed, soaked and centrifuged to separate the oil layer, and the upper oil layer is taken to obtain the natural oil.

[0008] Chopping: The fish paste raw material is chopped in a chopper in sequence under the conditions of 0℃~10℃, and then the natural oil body accounting for 0.1%~15% of the total weight of the fish paste raw material is added and mixed and chopped to obtain an emulsified slurry.

[0009] Molding and heat-induced gelation: The emulsified slurry is shaped, and after a first-stage heating and a second-stage heating heat-induced gelation treatment, it is cooled to obtain the surimi product.

[0010] In some embodiments of the present invention, the natural oil is one of peanut oil, soybean oil, sunflower seed oil, rapeseed oil, rice bran oil, and walnut oil.

[0011] In some embodiments of the present invention, the centrifugal separation conditions are: rotation speed of 3000~15000 r / min, temperature of 0~10℃, and centrifugation time of 5~60 min.

[0012] In some embodiments of the present invention, the time for air chopping is 0.5 to 5 minutes, and the speed of the chopper is 1000 to 4500 r / min; the time for salt chopping is 0.5 to 10 minutes, and the speed of the chopper is 4500 to 6500 r / min; the time for mixed chopping is 0.5 to 10 minutes.

[0013] In some embodiments of the present invention, the natural oil is added alone or in combination with free oil; the free oil is selected from at least one of vegetable oil or animal fat.

[0014] In some embodiments of the present invention, salt is added to the salt-chopping process at 2-3% of the weight of the chopped fish paste.

[0015] In some embodiments of the present invention, the conditions for the first stage of heating are: temperature 35-45°C, heating time 10-90 min; and the conditions for the second stage of heating are: temperature 75-95°C, heating time 5-40 min.

[0016] In some embodiments of the present invention, the surimi product is one of fish intestines, fish balls, fish tofu, fish cakes, and fish cakes.

[0017] The present invention also provides a surimi product, which is prepared by the method described above for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils.

[0018] Compared with the prior art, the present invention has the following advantages and beneficial effects:

[0019] (1) The method of improving the oxidative stability and freeze-thaw stability of surimi by using natural oil in this invention involves adding 0.1% to 15% of natural oil by weight of surimi. In the surimi product prepared, the natural oil particles are uniformly and completely embedded in the dense protein grid, avoiding phase separation and significantly improving its freeze-thaw stability and oxidative stability. It is suitable for developing high-quality surimi products with long shelf life.

[0020] (2) The surimi products of the present invention significantly reduce the rate of increase in protein carbonyl content and oil TBARS value caused by oxidation reaction, thus delaying the quality deterioration caused by oxidation reaction; at the same time, after multiple freeze-thaw cycles, the water holding capacity of the product is still greater than 60%, and can reach up to 69.5%, which has excellent water retention properties. Attached Figure Description

[0021] Figure 1 The water-holding capacity (WHC) of surimi gels prepared from different types of oils changed after multiple freeze-thaw cycles; where A, B, C, and D correspond to lipid addition concentrations of 2%, 4%, 6%, and 8%, respectively.

[0022] Figure 2 Comparison of lipid oxidative stability of surimi gels prepared from different types of oils; where A, B, C, and D correspond to lipid addition concentrations of 2%, 4%, 6%, and 8%, respectively.

[0023] Figure 3 Comparison of protein oxidative stability of surimi gels prepared from different types of oils; where A, B, C, and D correspond to lipid addition concentrations of 2%, 4%, 6%, and 8%, respectively.

[0024] Figure 4 The image shown is a scanning electron microscope image of fish paste gel for Comparative Example 8, where A is magnified 300 times and B is magnified 1000 times.

[0025] Figure 5 The image shown is a scanning electron microscope image of the fish paste gel in Example 4, where A is magnified 300 times and B is magnified 1000 times.

[0026] Figure 6 Changes in water-holding capacity (WHC) of fish myofibrillar protein gels prepared for different types of oils after multiple freeze-thaw cycles.

[0027] Figure 7 Comparison of lipid oxidative stability of fish myofibrillar protein gels prepared for different types of oils; among which, Figure 7 In the middle (a), the sample has not undergone freeze-thaw cycles. Figure 7 (b) is the sample after 4 freeze-thaw cycles.

[0028] Figure 8 A comparison of the protein oxidative stability of fish myofibrillar protein gels prepared for different types of oils; among them, Figure 8 (a) is the sample that has not been frozen and thawed. Figure 8 (b) is the sample after 4 freeze-thaw cycles. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention and their accompanying drawings.

[0030] In the following examples, the natural oil body was prepared as follows: peanut kernels were soaked or not soaked, then crushed and filtered. The filtrate was centrifuged at 10,000 r / min and 4℃ for 20 min, and the upper oil layer was collected.

[0031] Example 1:

[0032] A method for improving the oxidative stability and freeze-thaw stability of surimi products, the method being as follows:

[0033] S1. Thawing: Thaw the frozen fish paste stored at -20℃ at 4℃ for 12 hours to keep the temperature of the fish paste below 10℃.

[0034] S2. Air chopping: Place the thawed fish paste into a chopper and chop it at medium-low speed for 2 minutes. Keep the temperature inside the chopper below 10℃ to make the fish paste clump together and obtain air-chopped fish paste.

[0035] S3. Salt chopping: Add salt at 2.5% of the weight of the fish paste, along with a fixed amount of ice water. Chop at medium-high speed for 2 minutes, keeping the temperature inside the chopper below 10℃ to ensure the protein is fully dissolved and a viscous fish paste is obtained.

[0036] S4. Mixing and chopping: Add peanut oil to the viscous fish paste at 2% of the total weight of the frozen fish paste, chop at medium-high speed for 2 minutes, and keep the temperature below 10℃ to obtain oil-fish paste slurry.

[0037] S5. Adjust the moisture content: Add ice water to the oil-fish paste to adjust the final moisture content (e.g., 78%), continue chopping for 2 minutes, temperature <10℃, to obtain a uniform fish paste.

[0038] S6. Molding and maturation: The fish paste is shaped using a casting mold, heated in a 40℃ water bath for 30 minutes (first stage heating), and then heated in a 90℃ water bath for 30 minutes (second stage heating) to obtain a matured fish paste gel.

[0039] S7. Cooling: Place in ice water to cool for 30 minutes, wipe dry and store at 4°C.

[0040] Example 2

[0041] A method for improving the oxidative stability and freeze-thaw stability of surimi products, except that the amount of peanut oil added is 4%, the other steps are the same as in Example 1.

[0042] Example 3

[0043] A method for improving the oxidative stability and freeze-thaw stability of surimi products, except that the amount of peanut oil added is 6%, the other steps are the same as in Example 1.

[0044] Example 4

[0045] A method for improving the oxidative stability and freeze-thaw stability of surimi products, except that the amount of peanut oil added is 8%, the other steps are the same as in Example 1.

[0046] Comparative Examples 1-4

[0047] A traditional method for preparing surimi gel with added lard, wherein the peanut oil in Examples 1-4 is replaced with an equal mass of lard (added amounts of 2%, 4%, 6%, and 8%, respectively), and the remaining steps are the same as in Example 1.

[0048] Comparative Examples 5-8

[0049] A method for preparing surimi gel with added peanut oil, wherein the peanut oil body in Examples 1-4 is replaced with an equal mass of peanut oil (the amount added is 2%, 4%, 6%, and 8%, respectively), and the remaining steps are the same as in Example 1.

[0050] Comparative Example 9

[0051] A method for preparing surimi gel without adding any oil, which involves only air-cutting, salt-cutting, moisture adjustment and shaping and maturation steps, with the remaining steps being the same as in Example 1.

[0052] Example 5:

[0053] A method for improving the oxidative and freeze-thaw stability of fish myofibrillar (MP) gel:

[0054] (1) MP extraction and purification: The fish paste was mixed with 10 mmol / L phosphate buffer, and then crushed and homogenized (13000 r / min, 30 s, repeated twice) and filtered. The resulting homogenate was centrifuged to collect the precipitate, which was then washed three times each with 10 mmol / L and 50 mmol / L (containing 0.1 mol / L NaCl) phosphate buffer. The entire process was carried out at 0~4℃.

[0055] (2) Mixing and chopping: Add 8% (mass fraction) of peanut oil to the MP solution (50 mg / mL), place it in a chopper and chop it in a directional manner at a rate of 3000 r / min for 3 min.

[0056] (3) Molding and thermal gelation: The emulsified slurry is shaped by heating it in a 40°C water bath for 30 min (first stage heating) and then heating it in a 90°C water bath for 30 min (second stage heating) to obtain the matured surimi gel.

[0057] Comparative Examples 10-12

[0058] The method for preparing fish myofibrillar protein (MP) gel involves replacing the peanut oil mixture during mixing with equal masses of water (Comparative Example 10), lard (Comparative Example 11), and peanut oil (Comparative Example 12), with the remaining steps being the same as in Example 5.

[0059] The oxidative stability and freeze-thaw stability of the above embodiments and comparative examples were evaluated using the following methods:

[0060] 1. Evaluation of oxidative stability

[0061] (1) Protein oxidative stability: 0~400 mmol / L hydrogen peroxide was added to the surimi gel / MP gel and oxidized at 4℃ for 12h. The carbonyl content of the protein was then determined.

[0062] (2) Temperature-dependent oxidation of oils: The fish paste gel / MP gel was heated in a constant temperature oven at 60℃ for 0~24h to accelerate the oxidation process, and samples were taken at regular intervals to determine the TBARS value.

[0063] (3) Indicator measurement:

[0064] Protein carbonyl content: determined by the 2,4-dinitrophenylhydrazine (DNPH) colorimetric method. After reacting the sample with DNPH and washing the precipitate, the sample was dissolved in guanidine hydrochloride, and the absorbance was measured at 370 nm. The results are expressed as nmol / mg protein.

[0065] Thiobarbituric acid reactants (TBARS) values ​​of oils and fats: determined by the thiobarbituric acid (TBA) colorimetric method. Samples were extracted with trichloroacetic acid (TCA) and then reacted with TBA solution in a boiling water bath for color development. The absorbance was measured at 532 nm, and the results are expressed as mg MDA / kg.

[0066] 2. Freeze-thaw stability evaluation

[0067] (1) Freeze-thaw cycle treatment: Seal the gel sample and freeze it at -20°C for 20 h, then transfer it to 25°C to thaw for 4 h, which is recorded as one complete freeze-thaw cycle. Repeat the above operation and collect samples that have undergone 0, 1, 2, 3 and 4 freeze-thaw cycles respectively.

[0068] (2) Indicator measurement:

[0069] Accurately weigh the sample before freeze-thaw cycles and record the mass as M1. After freeze-thaw cycles, wrap the sample in qualitative filter paper and place it in a centrifuge tube. Centrifuge at 4°C and 4000 r / min for 10 min. Remove the sample, dry the surface moisture, and weigh it again, recording the weight as M2. The water-holding capacity calculation formula is as follows:

[0070]

[0071] Results analysis:

[0072] Figure 1 Changes in water-holding capacity (WHC) of surimi gels prepared from different types of oils after multiple freeze-thaw cycles. Figure 1 It is known that freeze-thaw cycles significantly reduce the water-holding capacity (WHC) of surimi gel. By comparing the control group (Comparative Example 9) without oil, it can be found that the water-holding capacity of the surimi gel significantly decreases due to the introduction of exogenous lipids (Examples 1-4 and Comparative Examples 1-8). Furthermore, the water-holding capacity of the surimi gel decreases significantly with increasing freeze-thaw cycles. Among these, at the same concentration, the decrease in water-holding capacity of the surimi gel in the peanut oil group is significantly slower, indicating better freeze-thaw stability. The surimi gel in the peanut oil group exhibits the worst freeze-thaw stability. At a high lipid level of 8% ( Figure 1 In the example (D), with increasing freeze-thaw cycles, the water-holding capacity of the peanut oil group (Comparative Example 8) decreased significantly, dropping from 81.35% to 52.1% after three cycles. The lard group (Comparative Example 4) followed, with its water-holding capacity decreasing from 92.63% to 66.63%. In contrast, the natural oil group (Example 4), with the same amount of added oil, maintained a water-holding capacity of approximately 69.5%, demonstrating a strong moisture-locking ability. This indicates that natural oil can effectively slow down the decrease in the water-holding capacity of the surimi gel during freeze-thaw cycles, significantly improving its freeze-thaw stability.

[0073] Figure 2 Comparison of the lipid oxidative stability of surimi gels prepared from different types of oils. Figure 2 The results showed that, within the 24-hour observation period, the TBARS values ​​of all samples increased significantly with prolonged heating time. Compared to the control group without oil (Comparative Example 9), the introduction of exogenous lipids (Examples 1-4 and Comparative Examples 1-8) resulted in a significantly higher oil TBARS value for the surimi gel. Furthermore, the rate of increase in TBARS value was significantly higher with increasing lipid content. When the lipid content was 8% ( Figure 2 In Example 8, the peanut oil group (Comparative Example 8) had the highest TBARS value of 5.75 mg MDA / kg; followed by the lard group (Comparative Example 4), which had the highest TBARS value of 4.69 mg MDA / kg; the TBARS value in Example 4 increased very slowly throughout the test period, reaching a maximum of only 3.26 mg MDA / kg. It is evident that compared to other lipid groups, the lipid oxidation process in the natural oil group was significantly slower, exhibiting excellent lipid oxidation stability.

[0074] Figure 3 A comparison of the protein oxidative stability of surimi gels prepared from different types of oils. Figure 3It can be seen that, compared with the blank group (Comparative Example 9) without exogenous lipids, the carbonyl content and growth rate of the lipid-containing samples were significantly higher, indicating that the free radicals generated by the oxidation of exogenous lipids further exacerbated the oxidative degradation of proteins. Furthermore, the rate of increase in carbonyl content was significantly higher with increasing lipid concentration. Figure 3 As shown in Figure D, under the induction of 400 mM H2O2, the group with 8% peanut oil (Comparative Example 8) had the highest carbonyl content of 9.9 nmol / mg protein; followed by the lard group (Comparative Example 4), with the highest carbonyl content of 8.19 nmol / mg protein; the peanut oil group (Example 4) showed the slowest increase in carbonyl content, remaining at an extremely low level, with a maximum of only 0.8 nmol / mg protein. It is evident that compared to other lipid groups, the natural oil group exhibited a significantly slower protein oxidation process, demonstrating excellent protein oxidation stability.

[0075] Figure 4 and Figure 5 This is a scanning electron microscope image of fish paste gel. (From...) Figure 4 (Comparative Example 8, 8% peanut oil) As can be seen, free peanut oil caused significant phase separation in the matrix, resulting in the formation of large, smooth-surfaced pores inside the gel. This loose and porous deteriorated structure severely weakens the water-locking capacity and physical barrier properties of the gel network, which is the direct cause of its significant decrease in water retention and accelerated oxidation. Example 4 (8% peanut oil body) surimi gel ( Figure 5 The natural oil particles are uniformly and completely embedded in the dense protein mesh, with no smooth pores observed, and the distribution of oil particles and protein matrix is ​​stable.

[0076] Figure 6 A comparative graph showing the changes in water-holding capacity (WHC) of fish myofibrillar protein gels prepared for different types of oils after multiple freeze-thaw cycles. Figure 6 It can be seen that the water-holding capacity of all samples decreased with the increase of freeze-thaw cycles. Among them, the natural oil group (Example 5) showed the most gradual decrease, and its water-holding capacity remained at 80% after 4 freeze-thaw cycles, while the water-holding capacity of the peanut oil group (Comparative Example 12) decreased to 73.5%. This indicates that the natural oil can effectively slow down the decrease in the water-holding capacity of fish myofibril protein gel during freeze-thaw cycles and significantly improve its freeze-thaw stability.

[0077] Figure 7 Comparative graph of lipid oxidative stability of fish myofibrillar protein gels prepared for different types of oils. Figure 7 It can be seen that the unfrozen sample ( Figure 7 The oxidative stability of the oil in (a) was significantly higher than that of the sample that underwent four freeze-thaw cycles. Figure 7 (b) ). Peanut oil samples that have not been frozen and thawed ( Figure 7In (a), comparative example 12, after heating for 24 h, its TBARS value increased from the initial 0.29 to 5.38 mg MDA / kg, compared to the natural oil body group ( Figure 7 In Example 5 (a), the TBARS value increased from 0.26 to 2.06 mg MDA / kg. After four freeze-thaw cycles, the peanut oil sample ( Figure 7 In the control group (b), after heating for 24 hours, the TBARS value increased sharply from 0.84 to 9.82 mg MDA / kg; in the natural oil body group ( Figure 7 In (b), Example 5), the TBARS value increased the slowest, with a maximum value of 6.0 mg MDA / kg.

[0078] Figure 8 A comparative diagram of the oxidative stability of fish myofibrillar protein gels prepared from different types of oils. Figure 8 It can be seen that, compared to samples that have not undergone freeze-thaw cycles ( Figure 8 (a) Sample after 4 freeze-thaw cycles ( Figure 8 The protein oxidative stability of group (b) was significantly worse. Meanwhile, the free oil group (comparative examples 11-12) showed a more pronounced trend of oxidative degradation under free radical attack than the natural oil group. After induction with 400 mM H2O2, the peanut oil group (after 4 freeze-thaw cycles) showed significantly lower oxidative stability. Figure 8 In (b), compared to Example 12, the carbonyl content reached a maximum of 7.5 nmol / mg protein, while the peanut oil body group ( Figure 8 In (b), Example 5), the highest value was 6.5 nmol / mg protein.

[0079] The above results indicate that the method of the present invention can effectively improve the oxidative stability and freeze-thaw stability of surimi products, delay the oxidative deterioration process of lipids and proteins, reduce the decrease in water-holding capacity of surimi gel caused by freeze-thaw cycles, and improve the microstructure and texture of surimi gel.

[0080] In some embodiments of the present invention, the natural oil body may be one of soybean oil body, sunflower seed oil body, rapeseed oil body, rice bran oil body, and walnut oil body.

[0081] In some embodiments of the present invention, the surimi product is one of fish intestines, fish balls, fish tofu, fish cakes, and fish cakes.

[0082] Those skilled in the art will readily understand that the above description is merely an embodiment of the present invention and is not intended to limit 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.

Claims

1. A method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils, characterized in that, Includes the following steps: Oil preparation: The oil-bearing seeds of plants are crushed, soaked and centrifuged to separate the oil layer, and the upper oil layer is taken to obtain the natural oil. Chopping: The fish paste raw material is chopped in a chopper in sequence under the conditions of 0℃~10℃, and then the natural oil body accounting for 0.1%~15% of the total weight of the fish paste raw material is added and mixed and chopped to obtain an emulsified slurry. Molding and heat-induced gelation: The emulsified slurry is shaped, and after a first-stage heating and a second-stage heating heat-induced gelation treatment, it is cooled to obtain the surimi product.

2. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1, characterized in that, The natural oil is one of the following: peanut oil, soybean oil, sunflower seed oil, rapeseed oil, rice bran oil, or walnut oil.

3. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1, characterized in that, The centrifugation conditions are: rotation speed of 3000~15000 r / min, temperature of 0~10℃, and centrifugation time of 5~60 min.

4. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1, characterized in that, The time for air chopping is 0.5 to 5 minutes, and the speed of the chopper is 1000 to 4500 r / min; the time for salt chopping is 0.5 to 10 minutes, and the speed of the chopper is 4500 to 6500 r / min; the time for mixed chopping is 0.5 to 10 minutes.

5. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1 or 4, characterized in that, The natural oil is added alone or in combination with free oils; the free oils are selected from at least one of vegetable oils or animal fats.

6. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1 or 4, characterized in that, In the salt-chopping process, salt is added at 2-3% of the weight of the chopped fish paste.

7. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1, characterized in that, The conditions for the first stage of heating are: temperature 35–45°C, heating time 10–90 min; the conditions for the second stage of heating are: temperature 75–95°C, heating time 5–40 min.

8. The method for improving the oxidative stability and freeze-thaw stability of surimi products using natural oils according to claim 1, characterized in that, The surimi product is one of the following: fish intestines, fish balls, fish tofu, fish cakes, and fish cakes.

9. A surimi product, characterized in that, It is prepared by the method described in any one of claims 1 to 8, which utilizes natural oils to enhance the oxidative stability and freeze-thaw stability of surimi products.

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