Method for improving quality of skipjack fish cake by utilizing low-temperature fishy smell removal and pre-curing treatment

Abstract

The invention discloses a method for improving the quality of skipjack cakes by using low-temperature fishy smell removal and pre-curing treatment, which comprises the steps of pretreatment, salt dipping, desalination, low-temperature rosemary dipping fishy smell removal, steaming curing and the like, optimizes the dipping process, and is applied to preparation of skipjack cakes. According to the preparation method, the low-temperature fishy smell removal and cooking combined curing mode is adopted, so that the skipjack cake with light fishy smell and good flavor is obtained. The fishy smell removal-hot processing integrated process adopted by the invention is mild in process and simple and convenient to operate, two-way improvement of flavor and texture can be completed on the premise that the protein structure of the skipjack is not damaged, and the method is suitable for industrial production line pretreatment and flexible terminal processing and is beneficial to improving the deep processing additional value of low-value fish such as the skipjack.

Description

Technical Field

[0001] The invention discloses a method for improving the quality of bonito fish cakes by utilizing low-temperature deodorization and coordinated pre-cooking treatment, and belongs to the field of food processing. Background Art

[0002] Skipjack tuna, listed as a major tuna resource by the Food and Agriculture Organization of the United Nations (FAO), is widely distributed in tropical, subtropical, and temperate waters worldwide and boasts high nutritional value. However, due to its strong fishy flavor, it is currently primarily used for canning, resulting in a low market position and being considered a "low-value tuna." Despite this, skipjack tuna's widespread distribution and high production yield significant development potential and room for improvement, requiring further exploration and improvement of its resource value.

[0003] Fish cakes, a type of surimi product, are considered a mid- to high-end aquatic product. Their key characteristic is that they retain the texture and flavor of fish flesh, yet lack visible flesh. They possess a delicate texture, are tender with a slight crispness, and are delicious. The flesh is white, tender, and smooth, with a rich umami flavor and no fishy odor. They are rich in nutrients, including high protein and low cholesterol. Deep-frying the surimi or combining it with enzymatic hydrolysis techniques can effectively improve the flavor and texture of fish cakes. This is primarily because the frying process not only masks some of the fishy odor but also promotes the formation of flavor compounds on the fish surface through the Maillard reaction. However, the fish meat in bonito cakes has a strong fishy odor during preparation, making it difficult to completely remove it through frying alone. Furthermore, the frying process results in a significant loss of nutrients from the fish meat. Furthermore, consuming fried fish can cause internal heatiness, which can negatively impact health. Fried fish cakes are often associated with undesirable texture issues, such as a high hardness.

[0004] Deodorizing bonito and combining it with a aging process to make fish cakes is an effective way to improve the flavor of bonito cakes. The fishy smell of bonito mainly comes from its red meat and high fat content. The lipids are easily oxidized, forming volatile compounds such as aldehydes, ketones and alcohols. Due to its safety and effectiveness, rosemary extract has gradually been used to remove the fishy smell of fish products while enhancing their flavor. At present, the traditional use of rosemary extract is mostly direct addition or room temperature immersion treatment. For example, in the article "The Effect of Rosemary Extract on the Fishy Odor of Silver Carp and Optimization of Deodorization Conditions", Huang Pi Miao et al. successfully removed some fishy substances by soaking silver carp at room temperature and optimizing the process conditions. However, in actual applications, rosemary extract often faces the difficult problem of balancing the deodorization effect and quality maintenance in the deodorization process of aquatic products.

[0005] For example, Huang Pimiao et al.'s research noted that silver carp deodorization still suffers from poor results (e.g., poor removal of aldehydes, which have a distinct fishy smell) and instability (e.g., the fish can return to its original smell after being cooked). Furthermore, insufficient flavor masking can affect raw material quality.

[0006] Furthermore, fishy deodorization is typically a pretreatment step in the preparation of bonito cakes. After deodorization, the fish requires subsequent processing, such as chopping and cooking. Existing fishy deodorization techniques often cause fishy flavor to return or deteriorate in quality after heat treatment. Therefore, there is an urgent need to develop a method for preparing bonito cakes that can maintain excellent flavor and quality after cooking. Summary of the Invention

[0007] In response to the above-mentioned problems, the purpose of the present invention is to provide a method for improving the quality of bonito fish cakes by utilizing low-temperature deodorization and pre-cooking treatment. The deodorization effect of bonito meat is improved by optimizing the low-temperature impregnation linkage process of rosemary extract, and the deodorized bonito meat is subjected to a cooking treatment to prepare bonito fish cakes. While significantly improving the deodorization effect, the method of the present invention better ensures the quality stability of the bonito raw material. The present invention provides a technical solution for the efficient deodorization of bonito. By constructing a diversified processing technology system for bonito cakes, it lays the foundation for the industrial development of bonito products and is of great significance for promoting the deep processing of bonito products.

[0008] To achieve the above-mentioned purpose, the present invention first provides a method for improving the quality of bonito fish cakes by utilizing low-temperature deodorization and pre-cooking treatment, comprising the following steps:

[0009] (1) Raw material pretreatment: thaw the frozen bonito at a core temperature of 0-4°C until the tail is loose and tender when pressed by fingers, remove the head, skin, and bones, and cut the bonito into uniform fish pieces or strips;

[0010] (2) Salt soaking: soak the fish pieces or fish strips prepared in step (1) in salt water. During the soaking process, gently stir the fish meat to allow the salt water to fully contact the fish meat.

[0011] (3) Desalting: Wash the bonito meat soaked in step (2) with clean water 2 to 3 times to remove the salt remaining in the bonito meat, and drain the water;

[0012] (4) deodorization treatment: immersing the bonito meat treated in step (3) in an aqueous solution of rosemary extract at a temperature of 0 to 4°C, draining the water after immersion, and then refrigerating at 4°C for 1 hour to obtain deodorized bonito meat;

[0013] (5) chopping the deodorized bonito obtained in step (4) for 2 to 3 minutes, adding salt, and continuing to chop and stir for 2 to 3 minutes to prepare it into fish cakes (the whole process is carried out in an ice bath);

[0014] (6) Put the fish cake obtained in step (5) into a steamer and steam it to obtain bonito cake.

[0015] In one embodiment of the present invention, in step (2), the immersion temperature is 0-4° C., the brine concentration is 10 g / L-20 g / L, each immersion is 15-30 minutes, and is repeated 1-3 times.

[0016] In one embodiment of the present invention, in step (4), the mass concentration of the rosemary extract in the aqueous solution of the rosemary extract is 0.2% to 1.2%, preferably 0.6 to 1.0%.

[0017] In one embodiment of the present invention, in step (4), the material-liquid ratio during immersion is 1:3 to 1:4 (w / v), and the immersion time is 0.5 to 2 hours.

[0018] In one embodiment of the present invention, in step (5), the amount of salt added is 1.5-2.5% of the mass of the bonito meat.

[0019] In one embodiment of the present invention, in step (6), steaming is performed at 90° C. to 100° C. for 15 to 20 minutes.

[0020] The present invention also provides a bonito cake prepared according to the method.

[0021] Beneficial effects:

[0022] (1) In the preparation process of bonito cakes, the conventional method is to directly chop and cook the bonito meat. Among the commonly used cooking methods, the bonito cakes prepared by frying and cooking have a better flavor and a lighter fishy smell and are widely accepted, while the bonito cakes prepared by steaming and cooking have a bland flavor and a stronger fishy smell. The present invention adopts a low-temperature deodorization combined with a cooking method to obtain bonito cakes with a lighter fishy smell and better flavor. During the cooking process after low-temperature deodorization, the hot and humid conditions of steaming (95% RH) promote the unfolding of myosin light chains, exposing more hydrophobic binding sites, so that polyphenols such as chlorogenic acid and luteolin in rosemary extract form non-covalent complexes with proteins. This combination not only improves the thermal stability of polyphenols, but also inhibits the lipid peroxidation chain reaction through the steric hindrance effect, thereby helping to further improve the flavor of the bonito cakes.

[0023] (2) The bonito cakes prepared by the present invention using a low-temperature deodorization combined with steaming method have good textural properties, which is attributed to the moist heat-induced protein gel network structure, which causes moderate cross-linking of myofibrillar proteins (such as myosin heavy chain). At the same time, the chelation effect of rosemary polyphenols on metal ions effectively alleviates excessive protein cross-linking and avoids textural hardening. The umami value of the bonito cakes after steaming is the highest, and the glycosylamine intermediates produced by steaming can directionally regulate the polyphenol oxidation pathway and reduce the production of bitter peptides.

[0024] (3) The deodorization-thermal processing integrated path process adopted by the present application is mild and easy to operate, and can complete the bidirectional improvement of flavor and texture without destroying the protein structure of bonito, is suitable for pretreatment and flexible terminal processing of industrial production lines, and helps to improve the deep processing added value of low-value fish species such as bonito.

[0025] (4) The unique chemical composition of rosemary extract enables it to more effectively adsorb and neutralize key odor substances in bonito under low temperature conditions, thereby achieving more thorough deodorization. This advantage makes rosemary extract irreplaceable in improving the quality of bonito products, providing a more efficient and reliable deodorization solution for the bonito processing industry. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 GC-MS heat map of non-deodorized, deodorized bonito meat in Example 2 and Comparative Example 1;

[0027] Figure 2 Lipid oxidation effect diagram of deodorized bonito meat in Example 2 and Comparative Example 1, wherein (A) and (B) are POV value and TBARS value, respectively;

[0028] Figure 3 GC-IMS fingerprint of bonito cake after maturation in Example 1 and Comparative Examples 2, 5-12;

[0029] Figure 4 GC-MS heat map of bonito cake after maturation in Example 1 and Comparative Examples 2, 5-12;

[0030] Figure 5 Water distribution diagram of bonito cake after maturation in Example 1 and Comparative Examples 2, 5-12;

[0031] Figure 6 Electronic tongue taste analysis diagram of bonito cake after maturation in Example 1 and Comparative Examples 2, 5-12;

[0032] Figure 7 Sensory evaluation diagram of bonito cake after maturation in Example 1 and Comparative Examples 2-4, 6, 10;

[0033] Figure 8 Water holding capacity analysis diagram of bonito cake after maturation in Example 1 and Comparative Examples 2-4, 6, 10. DETAILED DESCRIPTION

[0034] The preferred embodiments of the present application are described below, and it should be understood that the embodiments are for better explanation of the present application and are not used to limit the present application.

[0035] Test method:

[0036] Method for detecting the volatile flavor of bonito meat: Gas chromatography-ion mobility spectrometry (GC-IMS) and gas chromatography-mass spectrometry (GC-MS) were used to detect the volatile flavor of bonito.

[0037] GC-IMS: 3 g of fish sample was weighed and minced for each group, placed in a headspace vial, and incubated at 60°C for 20 min at 500 rpm. 500 μL of headspace sample was injected into a headspace autosampler at 80°C in splitless mode.

[0038] Chromatographic conditions were as follows: column temperature, 60°C; carrier gas, N2 (purity not less than 99.999%); carrier gas flow rate, 2.0 mL / min, maintained for 2 min, then linearly increased to 100 mL / min over 22 min and maintained for 5 min. The drift tube (5.3 cm) temperature and flow rate were maintained at 45°C and 150 mL / min, respectively. Beta radiation was used as the radiation source, and positive ionization mode was selected.

[0039] GC-MS: 3 g of fish sample was minced, added with 10 μL of cyclohexanone (100 mL / L internal standard), and placed in a 20 mL headspace vial. Volatile compounds were extracted at 50°C for 40 min using an SPME needle (30 m × 0.25 mm × 0.25 μm, Agilent, Santa Clara, CA, USA) equipped with a DVB / CGAR / PDMS fiber (50 / 30 μm, Supelco, Bellefonte, PA, USA). Helium was used as the carrier gas at a flow rate of 20 mL / min.

[0040] Chromatographic conditions were as follows: the column oven was initially maintained at 40°C for 5 min, then raised to 180°C at a rate of 4°C / min and held isothermally for 0 min. Finally, the column temperature was raised to 220°C at a rate of 10°C / min and held there for 5 min. The injection temperature was set at 250°C.

[0041] Mass spectrometry conditions were as follows: scan range 30–500 m / z, ionization voltage 70 eV, detector interface temperature 250°C, and ion source temperature 230°C. To identify volatile compounds, GC-MS mass spectra of volatile compounds were compared with those of standards retrieved from the NIST14 mass spectral library. Compounds with a match of 800 or greater were selected to screen for heterogeneous peaks.

[0042] Bonito meat lipid oxidation detection method:

[0043] POV value: Accurately weigh 50 g of bonito sample and add it to a cold mixture of water, methanol, and chloroform (25:100:100 by volume). After thorough mixing, rotary evaporation is performed to extract lipids. Dissolve 1 g of extracted lipids in 6 mL of a 3:2 solution of glacial acetic acid and trichloroacetic acid (v / v) and add 0.1 mL of potassium iodide. Protect from light for 10 min. To stabilize the solution, add 10 mL of deionized water and 1 mL of a 1 g starch solution (100 mL). Titrate the mixture with 0.01 M sodium thiosulfate solution until colorless. Calculate the POV value according to the following formula.

[0044]

[0045] Wherein, X1 is peroxide value, the unit is gram per 100g (g / 100g);

[0046] V—volume of sodium thiosulfate standard titration solution consumed by the sample, in milliliters (mL);

[0047] V 0—— The volume of sodium thiosulfate standard titration solution consumed in the blank test, in milliliters (mL);

[0048] c—concentration of sodium thiosulfate standard titration solution, in moles per liter (mol / 1);

[0049] 0.1269—The mass of iodine equivalent to 1.00 mL of sodium thiosulfate standard titration solution [c(Na2S2O3) = 1.000 mol / L], expressed in grams per millimole (g / mmol);

[0050] m—sample mass, in grams (g);

[0051] 100—Conversion factor for 100g sample.

[0052] TBARS value: 2 g of bonito flakes were placed in a centrifuge tube and homogenized in 20 mL of 10% (m / v) trichloroacetic acid (TCGA) for 2 minutes. The supernatant was then filtered and 5 mL was transferred to a stoppered glass tube containing 5 mL of a 0.02 mol / L TBA solution. The mixture was heated in a boiling water bath for 20 minutes and then cooled to room temperature. The absorbance was measured at a wavelength of 532 nm, and a blank test was performed. The absorbance was used to construct a calibration curve for 1,1,3,3-tetraethoxypropane and expressed as mg MDA / kg of sample.

[0053]

[0054] Where: TBARS—thiobarbituric acid value of the sample (mg / kg);

[0055] c—micrograms (μg) of malondialdehyde obtained from the standard curve;

[0056] m—mass of sample (g);

[0057] 5—Dilution factor.

[0058] Electronic nose analysis of bonito meat:

[0059] Detection of volatile flavor of bonito cake: The GC-IMS and GC-MS detection methods are consistent with the detection method of volatile flavor of bonito meat.

[0060] Bonito Cake Texture Testing: The texture characteristics of the samples were evaluated using the full texture analysis mode of the physical property analyzer. The cooked samples were cut into cylinders with a diameter of 30 mm and a height of 20 mm. Using a p50 probe, a trigger force of 5 g, and a pre-test speed of 2 mm / s, a test speed of 1 mm / s, and a post-test speed of 1 mm / s, each sample was compressed twice, with a compression ratio of 30%.

[0061] Bonito cake flavor detection method:

[0062] Electronic tongue testing method for bonito cakes: Accurately weigh 2g of cooked bonito meat and homogenize it with five times the volume of ultrapure water for 10 seconds, until the fish and water are thoroughly mixed. The mixture is then allowed to stand at 4°C for 2 hours. Centrifuge the mixture at 8000 rpm for 10 minutes in a high-speed refrigerated centrifuge, and the supernatant is extracted and filtered. Finally, the filtrate is diluted to 100mL with ultrapure water to ensure the sample is clear and transparent. 70mL of each prepared sample is evenly transferred to a sample cup and tested on the instrument.

[0063] Bonito Cake Color Testing: The color of the fish cakes was measured using a colorimeter, calibrated using a standard white plate. The fish cakes were cut into 20mm thick pieces. The color of the exterior and interior of the fish cakes was measured, and the L* (lightness), a* (red-green), and b* (yellow-blue) values ​​were recorded.

[0064] Testing the moisture distribution of bonito cakes: The sample was placed in a 10 mL EP tube. A standard solution was placed at the center of a 60 mm RF coil. Calibration was performed in FID mode to determine the center frequency and pulse duration. The sample was then placed in a 40 mm diameter cylindrical sample tube and exposed to a magnetic field with a strength of 0.5 T and a frequency of 21 MHz. The pulse lengths were set to 18.0 μs and 36.0 μs, respectively.

[0065] Example 1

[0066] A method for improving the quality of bonito fish cakes by utilizing low-temperature deodorization and pre-cooking treatment, comprising the following steps:

[0067] (1) Raw material pretreatment: The frozen bonito was thawed to a center temperature of 0-4℃ until the fish tail was loose and the fish was soft when pressed with fingers. The head, skin and fish bones were removed, and the bonito meat was cut into uniform pieces of 1 cm x 1 cm x 1 cm;

[0068] (2) Salt immersion: The fish pieces in step (1) were immersed in 10 g / L salt water at 4℃ for 30 min each time. During the soaking process, the fish meat was gently stirred to allow the salt water to fully contact the fish meat. The soaking was repeated twice;

[0069] (3) Desalination treatment: The bonito meat after immersion treatment in step (2) was washed with clean water for 3 times to remove the salt remaining in the bonito meat, and the water was drained;

[0070] (4) Deodorization treatment: The bonito meat after treatment in step (3) was immersed in a 1.0% rosemary extract aqueous solution at a ratio of 1:3 (w / v) for 40 min at 4℃. After immersion, the water was drained, and then the bonito meat was stored at 4℃ for 1 h to obtain deodorized bonito meat;

[0071] (5) Fish cake preparation: The deodorized bonito meat obtained in step (4) was chopped for 2 min, and 2.5% (w / w) salt was added. The mixture was chopped for another 2 min to prepare fish cakes;

[0072] (6) Maturation: The fish cakes obtained in step (5) were placed in a steamer and steamed at 100℃ for 20 min to obtain bonito cakes.

[0073] Example 2

[0074] Selection of rosemary extract concentration: Rosemary extract aqueous solutions with concentrations of 0.2%, 0.4%, 0.6%, 0.8% and 1.0% were prepared. The deodorized bonito meat obtained after steps (1)-(3) in Example 1 was deodorized according to the method of step (4) in Example 1. The deodorized bonito meat after deodorization with the five rosemary extract aqueous solutions with different concentrations corresponded to 0.2%, 0.4%, 0.6%, 0.8% and 1.0%, respectively. The deodorized bonito meat obtained without step (4) in Example 1 was used as a control.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 2 is that the immersion temperature in step (4) is 25℃, and the concentration of the rosemary extract aqueous solution is 1.0%.

[0077] Deodorization effect analysis:

[0078] Figure 1The GC-MS quantitative analysis results for the rosemary extract-deodorized bonito meat from different bonito varieties in Example 2 are shown. A total of 27 volatile flavor compounds were detected in Example 2, including 5 aldehydes, 8 alcohols, 2 ketones, and 12 alkanes. Due to their low detection threshold, aldehydes account for a large proportion of bonito volatile flavor compounds. Bonito meat contains a variety of aldehydes, including nonanal, hexanal, heptanal, (E)-2-octenal, decanal, and 2,5-bis(trimethylsilyloxy)benzaldehyde. As the rosemary extract concentration increased to 0.8%, nonanal, hexanal, and heptanal were no longer detected in the bonito flesh. Specifically, as the rosemary extract content in the impregnation solution increased, the nonanal content decreased from 0.69 mg / kg to 0.00 mg / kg, the heptanal content from 0.47 mg / kg to 0.00 mg / kg, and the hexanal content decreased even more significantly, from 2.75 mg / kg to 0.00 mg / kg. Decanal was found in the control, highlighting the beneficial effects of low temperature and rosemary extract impregnation on reducing aldehyde content in bonito. Alcohols such as 1-penten-3-ol and 1-octen-3-ol can also produce a fishy odor. The main alcohols detected in Example 2 included 1-penten-3-ol, 1-octen-3-ol, octanol, 1-hexanol, and other alcohols. Notably, 1-octen-3-ol is important for the volatile flavor of bonito due to its low detection threshold. This compound, known for its mushroom-like odor and role in fishy odor, is the most predominant volatile alcohol in various fish. In Example 2, the content of 1-octen-3-ol decreased with increasing amounts of rosemary extract. When the concentration of rosemary extract was increased to 1.0%, the 1-octen-3-ol content decreased by 67.21%. This reduction in 1-octen-3-ol further demonstrates the beneficial effects of rosemary extract infusion on the deodorization of bonito.

[0079] Example 2 and Comparative Example 1 compare the effects of low temperature and room temperature immersion on the deodorization of bonito. Figure 1 It can be seen that compared with Example 2, the deodorizing effect of Comparative Example 1 is lower. Aldehyde substances such as hexanal can still be detected in Comparative Example 1, and the removal effect of compounds representing fishy substances such as 1-octen-3-ol is significantly poor.

[0080] Figure 2 This is a graph evaluating lipid oxidation in the deodorized bonito meat after the bonito was immersed in the deodorizing liquid of Example 2 and Comparative Example 1. Figure 2A can be used to evaluate the degree of primary lipid oxidation in bonito flakes. The fish meat from the control and comparative example 1 had the highest POV values. However, the degree of lipid oxidation in the bonito flakes from Example 2 gradually decreased with increasing rosemary extract concentration (p < 0.05). When the rosemary extract concentration was increased to 1.0%, the POV value of the bonito flakes significantly decreased by 76.47% (p < 0.05) compared to the POV value in comparative example 1, and by 20.27% compared to the POV in comparative example 1, demonstrating that rosemary extract is more effective in reducing bonito flake lipid oxidation at low temperatures.

[0081] TBARS results ( Figure 2 B) shows that the malondialdehyde content in the bonito meat of the control example was the highest, while the malondialdehyde content in the bonito meat of Example 2 was significantly lower (p<0.05). Specifically, when the rosemary extract concentration was increased to 0.8% and 1.0%, respectively, compared to the control example, the TBARS values ​​decreased by 48.40% and 52.63%, indicating that low-temperature immersion in the deodorizing solution effectively reduced lipid oxidation in the bonito meat.

[0082] Comparative Example 2

[0083] The difference between Comparative Example 2 and Example 1 is that the deodorization treatment in step (4) is omitted, and the bonito meat obtained in step (3) is directly chopped and used to prepare bonito cakes.

[0084] Comparative Example 3

[0085] The difference between Comparative Example 3 and Example 1 is that the immersion temperature in step (4) is different from that in Example 1, and the immersion temperature is 25°C.

[0086] Comparative Example 4

[0087] The difference between Comparative Example 4 and Example 1 is that the immersion temperature in step (4) is different from that in Example 1, that is, the immersion temperature is 25° C. The aging method in step (6) is different, that is, frying at 1800 W for 150 s.

[0088] Comparative Example 5

[0089] The difference between Comparative Example 5 and Example 1 is that the aging method in step (6) is different. The aging method is two-stage heating. The conditions of the two-stage heating are: cooking at 40°C for 30 minutes and cooking at 90°C for 30 minutes to obtain bonito cakes.

[0090] Comparative Example 6

[0091] The difference between Comparative Example 6 and Example 1 is that the cooking method in step (6) is different, and the cooking method is frying at 1800W for 150s.

[0092] Comparative Example 7

[0093] The difference between Comparative Example 7 and Example 1 is that the cooking method in step (6) is different, and the cooking method is frying at 1400W for 180s.

[0094] Comparative Example 8

[0095] The difference between Comparative Example 8 and Example 1 is that the aging method in step (6) is different, and the aging method is microwave at 100% power for 20 seconds.

[0096] Comparative Example 9

[0097] The difference between Comparative Example 9 and Comparative Example 4 is that the deodorization treatment in step (4) is omitted, and the bonito meat obtained in step (3) is directly chopped and used to prepare bonito cakes.

[0098] Comparative Example 10

[0099] The difference between Comparative Example 10 and Comparative Example 5 is that the deodorization treatment in step (4) is omitted, and the bonito meat obtained in step (3) is directly chopped and used to prepare bonito cakes.

[0100] Comparative Example 11

[0101] The difference between Comparative Example 11 and Comparative Example 6 is that the deodorization treatment in step (4) is omitted, and the bonito meat obtained in step (3) is directly chopped and used to prepare bonito cakes.

[0102] Comparative Example 12

[0103] The difference between Comparative Example 12 and Comparative Example 7 is that the deodorization treatment in step (4) is omitted, and the bonito meat obtained in step (3) is directly chopped and used to prepare bonito cakes.

[0104] Test results of bonito cakes:

[0105] The change in color brightness can effectively determine the concentration change of volatile compounds in the sample. The brighter the color, the higher the concentration of the volatile compound in the sample. Figure 3 The GC-IMS fingerprints of the cooked bonito cakes of Example 1, Comparative Examples 5-8 and Comparative Examples 2 and Comparative Examples 9-12 are given. Figure 3As can be seen from the results, 55 volatile flavor compounds can be detected in the bonito cakes made from the bonito meat that has not been deodorized and has been deodorized with rosemary extract. Among them, there are 11 aldehydes, including aldehydes such as propanal, valeraldehyde, n-butyraldehyde, hexanal, and benzaldehyde. In the fish cake samples that have not been deodorized, the signals of aldehydes and alcohols (such as 1-octen-3-ol) are stronger in the result of Comparative Example 2, and may be accompanied by a small amount of nitrogenous compounds (such as trimethylamine), and the fishy smell signal is more obvious. In the non-deodorized fried group of Comparative Example 10, the signal in the corresponding nitrogenous compound area is significantly weakened, which may be due to the rapid volatilization of low-boiling point fishy smell substances under high temperature frying, and the Maillard reaction of free amino acids and reducing sugars produced by high temperature promotion protein decomposition, which converts some amine substances into non-volatile nitrogenous heterocyclic compounds (such as 2-methylpyrazine, and the signal intensity is significantly higher than that of the non-deodorized steamed group.

[0106] Comparing the five groups of samples that were not deodorized, the five groups of samples after the rosemary extract was deodorized showed a significant trend of decreasing color brightness, including n-butyraldehyde, hexanal, propionaldehyde, valeraldehyde, and benzaldehyde. The decline was particularly significant in Example 1 and Comparative Example 8, which may be due to the rosemary polyphenols effectively blocking the lipid peroxidation chain reaction by inhibiting lipoxygenase activity or scavenging free radicals. There are 11 alcohols, including amyl alcohol, butanol, 1-hexanol, 1-octen-3-ol, and other alcohols. Alcohols are mainly derived from the degradation of polyunsaturated fatty acids. In comparison, the bonito flakes in Comparative Examples 2, 9-12 had higher alcohol content, while the bonito flakes in Example 1 and Comparative Examples 5-8 had lower alcohol brightness. Among them, 1-octen-3-ol, which represents the fishy smell, showed the most significant change in brightness between Comparative Examples 2, 9-12 and Example 1 and Comparative Examples 5-8. This shows that the deodorization treatment of rosemary extract will not become ineffective after heat treatment, and the phenolic substances in rosemary extract have the effect of improving the degradation of fatty acids in fish cakes. There are 7 kinds of ester substances, which usually represent floral and fruity aromas. In Example 1, the content of ethyl butyrate and propyl butyrate in the comparative example 5-8 groups is relatively high. This result shows that the bonito cakes after deodorization treatment with rosemary extract can show better floral and fruity aroma. At the same time, the brightness change of α-pinene, which represents the aroma of pine wood, also has the same trend as ethyl butyrate and propyl butyrate. It suggests that rosemary extract may indirectly promote ester synthesis by regulating the fatty acid metabolic pathway or the conversion of Maillard reaction intermediates.

[0107] Figure 4 The GC-MS spectra of the cooked bonito cakes of Comparative Examples 2, 9-12 and Example 1, Comparative Examples 5-8 are given. Figure 4HS-SPME-GC-MS analysis of volatile compounds in bonito cakes processed differently revealed 63 volatile compounds, including 10 aldehydes, 10 alcohols, 6 ketones, 27 hydrocarbons, 3 acids, and 6 other compounds. Among these, aldehydes and alcohols, with lower odor thresholds, dominated the volatile compounds, primarily originating from the oxidation of unsaturated fatty acids. This suggests that fatty acid oxidation is the primary pathway for the formation of volatile flavor in bonito cakes.

[0108] Aldehyde substances include hexanal, heptanal, nonanal, decanal, dodecanal, (Z)-2-heptenal, benzaldehyde, (Z)-7-hexadecenal and 2-undecenal. Figure 4 As can be seen, after cooking, in Comparative Example 2, due to the low heating temperature and the humid environment, which inhibited the release of volatile components, a relatively high amount of short-chain aldehydes and ketones (such as fat oxidation products like valeraldehyde) remained (represented by light blue and white signals in the heat map). While these substances are not strongly odorous, they may contribute to the perception of stale oil. Furthermore, high-boiling-point alkanes and alkenes, due to their low volatility, remained in large quantities (light blue and white signals), potentially hindering the release of pleasant flavors and indirectly enhancing the perception of fishy odors. In contrast, in Comparative Example 10 (deep-fried), under high temperature, low-boiling-point aldehydes and ketones rapidly volatilized and partially decomposed into CO2 and water (corresponding to dark blue signals). The content of high-boiling-point alkanes and alkenes also decreased significantly due to thermal volatilization and cracking, effectively reducing unpleasant flavor precursors. Furthermore, the deep-fried group produced a small amount of esters through high-temperature esterification, producing a pleasant fruity aroma, further attenuating the potential fishy odor through a "flavor masking effect." No heptanal was detected in the deodorized bonito cakes. By comparing the experimental results of the comparative examples and the embodiments under the same processing mode, it can be seen that the decreasing trend of the aldehyde content before and after deodorization is more obvious in comparative example 5 and embodiment 1. Compared with comparative example 9, the hexanal content in comparative example 5 decreased by 80.95%, and the nonanal content decreased by 0.69%; compared with comparative example 2, the hexanal content of embodiment 1 decreased by 89.67%, and the nonanal content decreased by 72.73%. It may be because the hot and humid environment promotes the binding of polyphenols to proteins, enhancing their antioxidant stability. The accumulation of (Z)-7-hexadecenal in comparative examples 6 and 7 may be due to the directional cracking of long-chain fatty acids caused by high temperature.

[0109] Alcohols such as 1-octen-3-ol have mushroom and metallic taste and are considered as the characteristic fishy odor substances of fish. The lowest content of 1-octen-3-ol in Comparative Example 5 and Example 1 indicates that different processing methods have different effects on the fishy odor of the bonito cake after deodorization, and two-stage heating and steaming are more helpful to improve the fishy odor of the bonito cake. The production of 1-hexanol is mainly derived from the oxidative decomposition of fat, and heat treatment can exacerbate the production of 1-hexanol. Boryl alcohol is an aromatic compound in rosemary extract, and only a small amount of boryl alcohol exists in Comparative Example 8 after heat treatment. This may be because the microwave heating time is short and does not cause the complete decomposition of boryl alcohol.

[0110] Ketones are produced by thermal oxidative degradation of unsaturated fatty acids or amino acids, and the formation of ketones can be promoted by thermal peroxidation of saturated fatty acids, ketone enol tautomerization of hydroperoxide, further oxidation, decomposition and intramolecular electronic rearrangement of unsaturated fatty acid peroxide of hydrocarbon. Figure 3 It can be seen that heat treatment can exacerbate the oxidative decomposition of fatty acids, especially in the frying group and the frying group.

[0111] Table 1 gives the texture data of the bonito cakes after ripening of Comparative Examples 2, 9-12 and Example 1, Comparative Examples 5-8. As can be seen from Table 1, compared with Comparative Examples 2, 9-12, the hardness of all deodorized samples is significantly reduced, except for the frying group, which may be due to the inhibition of protein cross-linking by polyphenols in rosemary extract, reducing the hardness of the wet heat ripened fish cake. The hardness of the fish cake of Comparative Example 2 and Example 1 is the lowest (p<0.05), which may be due to the retention of high-quality protein during steaming processing. In contrast, the hardness of the bonito cakes of Comparative Example 10 and Comparative Example 6 is the highest, at 5173.38 g and 5405.13 g. This is due to the shell produced during the frying process, which makes it hard. It can be seen from the data of Comparative Example 11 and Comparative Example 7 that frying has a small effect on the hardness of the fish cake and does not cause the shell to be too hard. As can be seen from the elasticity data, the elasticity of the fish cake of Comparative Example 5 is the highest, at 0.99±0.00. The elasticity of the fish cake heated by microwave is lower than that of the fish cake steamed but higher than that of the fish cake processed by frying, which may be the result of the rapid transfer of heat by microwave heating, causing the protein and starch to denature rapidly and form a tight structure. In addition, the cohesiveness of the fish cake of Comparative Example 8 is higher. Different heating methods significantly affect the texture properties of the surimi product, and the steaming processing method has an advantage in retaining the quality of surimi.

[0112] Table 1 Texture data of bonito cakes after ripening of Example 1 and Comparative Examples 2, 5-12

[0113]

[0114]

[0115] Table 2 shows the surface color results of the cooked bonito cakes from Example 1 and Comparative Examples 2, 5-12. As shown in Table 2, analysis of the fish surface color reveals that bonito, rich in myoglobin, gives it a reddish appearance. The whiteness values ​​(W*) of the bonito meat treated with the different processing methods increased to varying degrees, likely due to thermal denaturation of myoglobin in the bonito muscle. Compared to the other treatment groups, the Example 1 group had the highest L* value, at 66.69±0.87, and the highest W* value, at 63.22±0.58. The deep-fried groups (Comparative Examples 10 and 6) and the pan-fried groups (Comparative Examples 11 and 7) had the lowest L* and W* values, while having higher b* values. This is likely due to the combined effects of various chemical and physical processes, such as the Maillard reaction, lipid oxidation, and oil adsorption, which result in a golden crust on the fish surface. Compared with the two-stage heating (Comparative Example 9 and Comparative Example 5) and the steaming group (Example 1 and Comparative Example 2), the L* value and W* value of the fish surface in the microwave group (Comparative Example 12 and Comparative Example 8) do not show advantages. This may be because the microwave heating speed is fast and the temperature distribution is uneven, which may cause uneven color and dryness on the surface, and the color is darker. In addition, the color of the fish cross-section was analyzed (Table 3). There is no obvious difference in the L* value and W* value of the bonito meat processed by different methods, and all show a higher whiteness value. The internal myoglobin denaturation is more homogeneous during the heat penetration process, and is less affected by the surface oxidation / browning reaction.

[0116] Table 2 Surface color of cooked bonito cakes of Example 1 and Comparative Examples 2, 5-12

[0117]

[0118] Table 3 Color of the cross section of cooked bonito cakes of Example 1 and Comparative Examples 2, 5-12

[0119]

[0120] Figure 5 The moisture distribution diagram of the cooked bonito cakes of Example 1 and Comparative Example 2, 5-12, is shown in FIG. Figure 5It can be seen that the majority of the water in the bonito cakes cooked using different processing methods comes from fixed water. The fixed water content in Comparative Examples 5 and 9 was significantly higher than in the other treatment groups. This is because the two-stage heating method allows the protein in the bonito meat to tightly bind with water, forming a gel, thereby increasing its water-holding capacity. Furthermore, the fixed water content in Example 1 and Comparative Example 2 was relatively high, with only a portion converted into free water. This may be because, compared to two-stage heating, steaming has a slightly weaker positive effect on gel formation in bonito meat. Water in the form of free water is a potential moisture state that contributes to cooking losses, and the formation and increase of free water during heating may also contribute to water loss. Some of the immobile water in Comparative Examples 10-11 and Comparative Examples 6-7 was converted into free water. This may be due to factors such as rapid evaporation caused by high temperature and rapid heat transfer, water consumption during chemical reactions, and the formation of an external hard shell that prevents internal moisture from being fixed. Two-stage heating significantly improves the retention of fixed water by forming a stable protein gel network, while high-temperature and rapid transfer processing methods (such as microwaves) are more likely to cause fixed water to convert into free water, increasing water loss.

[0121] Figure 6 The electronic tongue taste characteristics of the cooked bonito patties of Example 1 and Comparative Examples 2, 5-12 are shown. The electronic tongue can objectively quantify the overall taste characteristics of food samples and analyze the differences between groups. The electronic tongue analysis of bonito patties processed in different ways before and after deodorization with rosemary extract was performed to evaluate the sourness, saltiness, bitterness, astringency, umami, and aftertaste. Figure 6 ). The sample of Example 1 showed a higher umami taste. This may be because during the steaming process, the 100°C hot and humid environment causes the fish protein to denature moderately under relatively mild conditions, thereby protecting the content of amino acids such as glutamic acid and aspartic acid that present umami. At the same time, the antioxidant effect of rosemary polyphenols can inhibit the interference of lipid oxidation products on umami receptors, thereby enhancing the perception of umami. The microwave group (Comparative Example 12 and Comparative Example 8) had the lowest umami taste compared to the other groups, which may be because it is closely related to the "hot spot effect" unique to microwave heating. The oscillation of water molecules induced by the electromagnetic field leads to a temperature gradient difference, which accelerates excessive protein denaturation and destroys the muscle fiber network structure, resulting in a decrease in the dissolution rate of umami substances. The astringency of fish may come from blood residues, fat oxidation products, and some nitrogen-containing compounds. The astringency of Comparative Example 6 was the lowest compared to the other groups. This difference may be due to the Maillard reaction products (such as melanoidins and pyrazine compounds) triggered by high temperature binding to polyphenol-metal ion complexes through hydrogen bonds, thus masking the astringency caused by blood residues (such as heme iron). Among the ten groups of samples, the saltiness of Comparative Example 5 and Example 1 was the highest, and the saltiness of Comparative Example 7 was the lowest. This may be because the processing methods of steaming and two-stage heating are relatively mild, which promotes the absorption of Na +The uniform diffusion of Na in the interfilament space, while the dense shell formed during frying and deep-frying hinders the diffusion of Na + Contact with taste buds results in a decrease in the intensity of salty taste perception.

[0122] Figure 7 The sensory evaluation chart of the cooked bonito cakes of Example 1 and Comparative Examples 2, 5-12 is shown. Sensory properties directly affect consumers' product experience and are key indicators for product evaluation. The sensory properties of the bonito cakes were evaluated based on odor, appearance, texture, elasticity, hardness, and overall preference. Figure 7 ). Compared with comparative examples 2, 9-12, the panelists gave higher overall preference scores for the deodorized bonito fish cakes (p<0.05), indicating that the deodorization treatment effectively improved the flavor and texture of the bonito fish cakes. Among them, the sample with the highest appearance attribute score was Example 1, which may be because the steaming treatment maintained structural uniformity through moderate protein gelation. There was no significant difference in hardness and elasticity properties between the groups. The odor and tissue state preference scores for comparative example 7 were the highest, indicating that the deodorization combined with frying and maturation generated a burnt flavor (such as pyrazines and furans) that complemented the herbal aroma of rosemary polyphenols, which can effectively enhance the masking effect of the fishy smell. At the same time, the high-temperature, short-time frying treatment may cause the myofibrillar protein to form a dense and porous gel network, which both retains moisture and imparts chewiness, and its overall preference score is the highest.

[0123] Figure 8The water holding capacity analysis diagram of the cooked bonito cakes of Example 1 and Comparative Examples 2-4, 6, and 10 is obtained by comparing the effects of different deodorization temperatures (undeodorized, deodorized at room temperature, and deodorized at low temperature) and processing methods (steaming and frying) on ​​the water holding capacity of the fish cakes. The results show that in the undeodorized groups (Comparative Examples 2 and 10), the water holding capacity of Comparative Example 2 was significantly higher than that of Comparative Example 10, indicating that under the undeodorized conditions, the steaming process promoted moderate denaturation of proteins through a humid and hot environment to form a dense gel network, effectively locking in moisture; while the fried group lost moisture due to rapid vaporization due to high temperature, and the free oil and fishy substances in the undeodorized fish paste interfered with the integrity of the protein network, further reducing the water holding capacity. Among the room temperature deodorized groups (Comparative Examples 3 and 4), the water holding capacity of the room temperature deodorized steaming group (Comparative Example 3) was slightly lower than that of Example 1, but significantly higher than the room temperature deodorized fried group (Comparative Example 4). Room temperature deodorization (25°C) removes some soluble proteins and free fishy substances by rinsing, and optimizes the protein gel structure to a certain extent. However, compared with low temperature deodorization (4°C), room temperature may cause slight denaturation of heat-sensitive myofibrillar proteins and reduce the density of the gel network, so the water holding capacity is lower than that of Example 1. The water holding capacity of Example 1 reaches a maximum of 79.53%, which is significantly higher than that of Comparative Example 6. The core advantages of low-temperature deodorization are: inhibiting endogenous protease activity and reducing protein degradation; maintaining the natural structure of myofibrillar proteins, forming a more ordered three-dimensional gel network through gentle heating during cooking, and enhancing water binding capacity; the warm environment reduces the loss of water-soluble flavor substances and avoids the formation of "holes" in the protein network due to missing components, thereby maximizing water retention. In particular, the synergistic effect of low-temperature deodorization and cooking process (Example 1) is significantly better than other combinations: the natural protein structure retained by low-temperature deodorization and the mild gelation process of cooking form a "complementary" relationship, which increases the water holding capacity by 13.9% compared with the non-deodorized and cooked group (Comparative Example 2) and by 9.7% compared with the room temperature deodorized and cooked group (Comparative Example 3), confirming the technical advantages of the "low-temperature deodorization-steaming" combination.

[0124] Mechanism analysis: This patent systematically analyzed the synergistic effects of different ripening methods and rosemary deodorization and found that the combination of steaming process and rosemary extract showed the best quality control effect. Its control mechanism stems from the synergistic antioxidant effect of the humid and hot environment and polyphenols and the protein structure control effect. GC-MS data showed that the content of hexanal and nonanal in Example 1 decreased by 89.67% and 72.73% (p < 0.05) compared with the non-deodorized group. This is closely related to the specific inhibition of rosemary polyphenols on lipoxygenase. It is speculated that the phenolic hydroxyl group may coordinate the Fe at the active center of LOX. 2+, blocking the conversion of linoleic acid to hydroperoxides. At the same time, the moist heat conditions of steaming (95% RH) promote the unfolding of myosin light chains, exposing more hydrophobic binding sites, allowing polyphenols such as chlorogenic acid and luteolin to form non-covalent complexes with proteins. This binding not only improves the thermal stability of polyphenols but also inhibits lipid peroxidation chain reactions through steric hindrance. Notably, pyrrolines produced by the thermal denaturation of myoglobin during steaming can form Schiff base adducts with polyphenols. This interaction significantly promotes the synthesis of ester flavor compounds, increasing the ethyl butyrate content compared to the fried group, which is highly consistent with the result of a 37% increase in the brightness of α-pinene in the GC-IMS spectrum.

[0125] Compared with other cooking methods, steaming shows unique advantages in texture regulation. The hardness of the fish cake in Example 1 was the lowest, significantly lower than that of the fried group (5173.38g, p<0.05), which was attributed to the moist heat-induced protein gel network structure, and the moderate cross-linking of myofibrillar proteins (such as myosin heavy chain). At the same time, the chelation effect of rosemary polyphenols on metal ions effectively alleviated the excessive cross-linking of proteins and avoided texture hardening. Electronic tongue analysis further revealed that Example 1 had the highest umami value, and the glycosylamine intermediates produced by steaming could directionally regulate the polyphenol oxidation pathway and reduce the production of bitter peptides, while the fried group had excessive accumulation of acrylamide due to local temperatures exceeding 180°C.

[0126] The embodiments provided above are not intended to limit the scope of the present invention, nor are the steps described to limit their execution order. Any obvious improvements to the present invention made by those skilled in the art in combination with existing common knowledge shall fall within the scope of protection defined by the claims of the present invention.

Claims

1. A method for improving the quality of bonito fish cakes by utilizing low-temperature deodorization and pre-cooking treatment, characterized in that: The following steps are involved: (1) Raw material pretreatment: After thawing, remove the head, skin, and bones of the frozen bonito, and cut the bonito meat into uniform fish pieces or uniform fish strips; (2) salt soaking: soaking the fish pieces or fish strips in salt water to obtain soaked bonito meat; (3) Desalination: The bonito meat after the immersion treatment in step (2) is washed with clean water to remove the salt remaining in the bonito meat, and the water is drained; (4) deodorization treatment: immersing the bonito meat treated in step (3) in an aqueous solution of rosemary extract at a temperature of 0 to 4°C, draining the water after immersion, and then refrigerating at 4°C for 1 hour to obtain deodorized bonito meat; (5) chopping: chopping the deodorized bonito meat obtained in step (4) for 2 to 3 minutes in an ice bath, adding salt, and continuing to chop for 2 to 3 minutes to prepare it into fish cakes; (6) Put the fish cake obtained in step (5) into a steamer and steam it to obtain bonito cake.

2. The method according to claim 1, characterized in that In step (2), the immersion temperature is 0-4° C., the brine concentration is 10 g / L-20 g / L, each immersion is 15-30 minutes, and is repeated 1-3 times.

3. The method according to claim 1, characterized in that In step (4), the mass concentration of the rosemary extract in the aqueous solution of the rosemary extract is 0.2% to 1.2%.

4. The method according to claim 1, wherein In step (4), the mass volume ratio of the bonito meat to the rosemary extract aqueous solution during immersion is 1:3 to 1:4, and the immersion time is 0.5 to 2 hours.

5. The method according to claim 1, wherein In step (5), the amount of salt added is 1.5-2.5% of the mass of the bonito meat.

6. The method according to claim 1, characterized in that In step (6), the steaming is performed at 90° C. to 100° C. for 15 to 20 minutes.

7. The bonito cake prepared according to the method according to any one of claims 1 to 6.

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