Preparation method of lactobacillus fermented fish cake easy to swallow

Abstract

The invention discloses a preparation method of lactobacillus fermented fish cakes easy to swallow, and belongs to the technical field of food processing. The preparation method comprises the following steps: performing low-temperature semi-unfreezing on frozen surimi, adjusting the water content, performing empty grinding on the surimi, adding table salt, performing chopping and mixing, adding starch, and performing continuous chopping and mixing so as to form surimi gel; lactobacillus plantarum is dissolved in water, and the mixture is added into the minced fillet gel to be chopped and mixed; performing lactobacillus plantarum fermentation on the uniformly mixed surimi sausage at a constant temperature under proper conditions; the fermented minced fillet is subjected to a water bath at 40 DEG C for 30 min, and is transferred to a water bath at 90 DEG C for 30 min to obtain the fermented fish After heating is finished, the fermented fish cake is rapidly put into ice water to be cooled, and low-temperature refrigeration is conducted. By optimizing fermentation process conditions, the lactobacillus fermented fish cake easy to swallow, which is excellent in quality and suitable for being eaten by people with difficulty in swallowing, is developed, the diet requirements of the people with difficulty in swallowing are met, and meanwhile, the development of special diet foods is promoted.

Description

Technical Field

[0001] The present invention belongs to the technical field of food processing, and particularly relates to a preparation method of lactic acid bacteria-fermented easy-to-swallow fish cakes. Background Art

[0002] As a type of food deeply loved by consumers, surimi products occupy an important position in the food market because they are rich in high-quality protein, have a delicious taste, and are convenient to eat. However, for people with swallowing difficulties, the texture of ordinary fish cakes may pose challenges to their eating, restricting the popularity of such nutritious delicacies among special populations. Swallowing difficulties are relatively common among the elderly, people suffering from neurological diseases or certain oral and pharyngeal diseases.

[0003] Lactobacillus plantarum LP 90, as a common probiotic, can utilize substances such as sugars for metabolic activities, producing metabolic products such as organic acids and bacteriocins. These metabolic products can not only regulate the acidity of the fermentation environment, inhibit the growth of harmful microorganisms, and ensure food safety, but also endow the food with a unique flavor. At the same time, during the fermentation process, the interaction between microorganisms and components such as proteins and fats in surimi may change the structure and properties of surimi, thereby affecting the quality of surimi products, such as gel strength and water-holding capacity. Research shows that Lactobacillus plantarum can effectively regulate the taste and texture of products in fermented foods such as yogurt and pickles. At present, there are still many blanks in the application research of Lactobacillus plantarum LP 90 in the surimi fermentation process.

[0004] Alaska pollack fish cake, as a popular marine food, is favored by consumers for its unique flavor and nutritional value. However, during the processing of traditional fish cakes, it is vulnerable to microbial contamination, resulting in unstable quality and a short shelf life. In recent years, lactic acid bacteria fermentation technology has been widely used in the processing field of surimi products due to its remarkable effects in improving food quality, extending shelf life, and enhancing safety. Summary of the Invention

[0005] Aiming at the deficiencies in the prior art, the purpose of the present invention is to provide a preparation method of lactic acid bacteria-fermented easy-to-swallow fish cakes. The texture characteristics and water-holding properties of Alaska pollack fish cakes fermented by Lactobacillus plantarum are improved to a certain extent. At the same time, the fishy smell in Alaska pollack surimi is reduced, the flavor and quality of the fish cake are enhanced, filling the gap in this special food field in the market, and bringing richer, more nutritious and safer dietary choices for people with swallowing difficulties.

[0006] To achieve the above purpose, the present invention adopts the following technical solutions:

[0007] The present invention provides a preparation method of lactic acid bacteria-fermented easy-to-swallow fish cakes, comprising the following steps:

[0008] (1) Thawing and chopping: Thaw the frozen surimi at low temperature semi-thaw, adjust the moisture content, first perform empty chopping on the surimi, then add salt and chop, and then add starch and continue to chop to form surimi gel;

[0009] (2) Fermentation by Lactobacillus plantarum: Dissolve Lactobacillus plantarum in water and add it to the surimi gel for chopping;

[0010] (3) Enema the uniformly mixed surimi and perform Lactobacillus plantarum fermentation under constant temperature and appropriate humidity conditions;

[0011] (4) Heating and ripening: Heat the fermented surimi in a water bath at 40 °C for 30 min, then transfer it to a water bath at 90 °C for 30 min to obtain fermented fish cake;

[0012] (5) Freezing and storage: After the heating is completed, quickly cool the fermented fish cake in ice water and store it at low temperature to obtain.

[0013] Preferably, in step (1), the frozen surimi is the frozen surimi of Alaska pollack.

[0014] Preferably, in step (1), the process of thawing and chopping is as follows: After semi-thawing the frozen surimi at 4 °C, adjust the moisture content to 80%, perform empty chopping for 5 min, add 2% salt and 5% starch according to the mass of the surimi, and continue to chop for 10 min.

[0015] Preferably, in step (2), the Lactobacillus plantarum is Lactobacillus plantarum LP 90, and the addition amount accounts for 0.1%-5% of the mass of the surimi.

[0016] More preferably, in step (2), the addition amount of Lactobacillus plantarum LP 90 accounts for 0.5%-3% of the mass of the surimi.

[0017] Preferably, in step (3), the diameter of the casing used for enema is 20-40 mm.

[0018] More preferably, in step (3), the diameter of the casing used for enema is 30 mm.

[0019] Preferably, in step (3), the fermentation temperature is 30 °C, the fermentation humidity is 85%, and the fermentation time is 2-10 h.

[0020] More preferably, in step (3), the fermentation temperature is 30 °C, the fermentation humidity is 85%, and the fermentation time is 8 h.

[0021] Compared with the prior art, the beneficial technical effects of the present invention are as follows: The present invention provides a preparation method of lactic acid bacteria-fermented easy-to-swallow fish cakes. By optimizing the fermentation process conditions of fish cakes with Lactobacillus plantarum LP90 starter, an easy-to-swallow fish cake fermented by lactic acid bacteria with excellent quality and suitable for people with dysphagia is developed, improving the flavor, texture and overall acceptance of fish cakes, inhibiting the increase of TVB-N value, meeting the dietary needs of people with dysphagia, and promoting the development of special dietary foods. Description of the Drawings

[0022] Figure 1 For the IDDSI dysphagia diet classification.

[0023] Figure 2 For the changes in the pH value and WHC (A), TVB-N and gel strength (B) of fish cakes during the lactic acid bacteria fermentation process in the examples.

[0024] Figure 3 For the IDDSI test results of the control group fish cakes in the examples.

[0025] Figure 4 For the IDDSI test results of the 0.5% group fish cakes in the examples.

[0026] Figure 5 For the changes in the storage modulus G’ (A, B) and loss modulus G” (C, D) of fish cakes during the lactic acid bacteria fermentation process in the examples.

[0027] Figure 6 For the T2 relaxation time curves (A, B) and peak ratio (C) of fish cakes during the lactic acid bacteria fermentation process in the examples.

[0028] Figure 7 For the radar charts (A, B) and PCA analysis (C, D) of the odor characteristics of lactic acid bacteria-fermented fish cakes based on electronic nose in the examples.

[0029] Figure 8 For the radar charts (A, B) and PCA analysis (C, D) of the taste characteristics of lactic acid bacteria-fermented fish cakes based on electronic tongue in the examples.

[0030] Figure 9 For the GC-IMS fingerprint of the volatile components of fish cakes in the examples. Detailed Embodiments

[0031] To more fully understand the technical solutions, objectives, and advantages of the present invention, the technical effects of the present invention will be further described in detail and completely below in conjunction with specific embodiments and the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of them. It should be noted that for those of ordinary skill in the art, other embodiments obtained without departing from the concept of the present invention all belong to the protection scope of the present invention.

[0032] Unless otherwise specified in the following embodiments, the reagents and materials used are all commercially available.

[0033] Materials and reagents used in the following embodiments: light magnesium oxide; trichloroacetic acid; EDTA solution; thiobarbituric acid solution; trichloroacetic acid; perchloric acid; potassium hydroxide; sodium hydroxide.

[0034] Instruments and equipment used in the following embodiments: homogenizer; pH meter; Kjeldahl nitrogen analyzer; refrigerated centrifuge; TA.XTPlus texture analyzer: from Stable Micro System, UK; microplate reader; rotational rheometer; nuclear magnetic resonance imaging instrument; electronic nose; electronic tongue; automatic amino acid analyzer; high performance liquid chromatography; Floorspace gas chromatography-ion mobility spectrometer.

[0035] Example 1

[0036] 1 Experimental method

[0037] 1.1 Fish cake production

[0038] Take the frozen surimi, semi-thaw it at 4°C, adjust the moisture content to 80%, empty beat for 5 min, add 2% salt and 5% starch according to the mass of surimi, and continue chopping for 10 min. Add Lactobacillus plantarum LP 90 starter at 0.5%; 1%; 2%; 3% of the mass of surimi to the surimi respectively (experimental groups). The control group does not add bacteria (ck group). Fill the evenly mixed surimi into casings (Φ = 30 mm), and then ferment at 30°C. Samples of each fermentation group are collected at 0, 2, 4, 6, and 8 h, transferred to a 90°C water bath for 30 min after a 30-min water bath at 40°C, immediately placed in an ice water bath for cooling after heating, and analyzed after refrigerating overnight in a 4°C refrigerator.

[0039] 1.2 pH value

[0040] According to the method of Kang et al., use an FM-200 homogenizer (Fukke Equipment Co., Ltd., Shanghai, China) to mix the prepared surimi with deionized water at a volume ratio of 1:4 at a speed of 15,000 rpm in an ice bath. Use a digital pH meter (FE-28, Mettler-Toledo, Switzerland) to measure the pH value of each treatment group.

[0041] 1.3 Water holding capacity

[0042] Refer to the method of Li et al. Cut the sample into thin slices (about 3 g) for accurate weighing (m1), wrap it with filter paper and put it into a 50 mL centrifuge tube. Use a refrigerated centrifuge to centrifuge the centrifuge tube at 4 °C and 10,000×g for 10 min. After centrifugation, record the sample mass as m2. Calculate WHC using the formula.

[0043]

[0044] 1.4. TVB-N

[0045] Determination was carried out according to GB 5009.228-2016 "National Food Safety Standard - Determination of Volatile Basic Nitrogen in Foods" and the semi-micro Kjeldahl nitrogen determination principle. Accurately weigh 5.000 g of surimi sample and put it into a digestion tube, add 2 spoons of light magnesium oxide powder, and use a Kjeldahl nitrogen analyzer with a set program to determine the TVB-N value of the surimi sample. Take the average value of 3 parallel determinations.

[0046] 1.5. Gel strength

[0047] Cut the prepared surimi sample into cylinders with a diameter of 20 mm and a height of 20 mm, let it stand at room temperature for 30 min to reach equilibrium, and then place it on the analysis platform of a texture analyzer. Use a texture analyzer equipped with a P / 5S spherical plunger to determine the gel strength of the surimi gel. The parameters are as follows: the test speed is set to 1 mm / s, the compression distance is 10 mm, and the trigger force is 5 g. Conduct 3 parallel tests for each group of samples and take the average value of the results.

[0048] 1.6. Texture

[0049] Refer to the method of Trindade et al. with slight modifications. Cut the prepared surimi sample into cylinders with a diameter of 20 mm and a height of 20 mm, let it stand at room temperature for 30 min to reach equilibrium, and then place it on the physical property analysis platform. Use a texture analyzer (TA-XT.plus, Stable Micro Systems Ltd., UK) equipped with a P / 50 probe to measure the texture properties of the cylindrical surimi gel. The pre-test speed, test speed, and post-test speed are all set to 2 mm / s, and the compression deformation is set to 50%. Conduct 3 parallel tests for each group of samples and take the average value of the results.

[0050] 1.7. Sensory evaluation

[0051] Cook the surimi sample at 95 °C ± 2 °C for 10 min. Invite 10 postgraduate students majoring in food science (5 males and 5 females). After learning the relevant professional knowledge and detailed rules, conduct sensory quality evaluation on the surimi products. Rinse the mouth before evaluating each group of samples to reduce sensory errors. The evaluation criteria are shown in Table 1.

[0052] Table 1: Sensory scoring criteria for products

[0053]

[0054]

[0055] 1.8. IDDSI Testing

[0056] The International Dysphagia Diet Standardization Initiative (IDSSI) provides guidelines for adjusting food texture according to different types of foods, as well as a comprehensive classification standard for edible foods, using 8 grades (0 - 7 grades), see Figure 1 .. In the preliminary evaluation, surimi gels were defined as level 5 minced and moist or level 6 soft and bite-sized dysphagia diets. Dysphagia diets according to level 5 minced and moist should exhibit the following characteristics: can be eaten with a fork or spoon; can be scooped and shaped on a plate; soft and moist, without separate thin liquids, and the lumps are easily flattened with the tongue. Level 6 soft and bite-sized dysphagia diets should have the following characteristics: can be eaten with a fork or spoon; can be broken down by the pressure of a fork or spoon; overall soft, soft, and moist, but without separate thin liquids, need to be chewed before swallowing, and the "bite-sized" pieces are suitable for size and oral handling skills. The surimi samples were cut into 2×2×1 cm cuboids for fork drop test, spoon tilt test, and fork compression test. First, the fork drop test was achieved by observing the flow behavior of the surimi sample on the fork. For the spoon tilt test, the sample was placed on the spoon, then the spoon was slowly tilted, and the behavior of the sample during this process was observed and recorded to evaluate the adhesiveness and cohesiveness of the printed surimi, and the sliding of the surimi on the spoon was observed. Finally, a cuboid surimi sample was applied through the fork compression test, and the surimi was pressed with a standard metal fork until the fingernail turned white (pressure ~17 kPa) to observe the deformation behavior of the surimi after pressing.

[0057] 1.9 TBARS

[0058] Take 2 g of surimi sample, add 20 mL of 75% trichloroacetic acid solution containing 0.1% EDTA, homogenize at 4 °C for 1 min, centrifuge at 4 °C and 10000 g for 10 min, mix 5 mL of the supernatant with 5 mL of 0.02 mol / L TBA solution, react in boiling water for 40 min, and measure the absorbance of the sample solution at 532 nm after cooling. The TBARS value is calculated by the following formula:

[0059] TBARS (mg / kg) = A 532 × 7.8.

[0060] 1.10 Rheological Properties

[0061] Using a rheometer (KNX2000, Malvern Instruments Ltd., UK), with a 40-mm diameter probe, the surimi was heated from 25 °C to 90 °C at a rate of 2 °C / min, and the sample gap was set at 1.00 mm; the changes in storage modulus G’ and loss modulus G” with temperature were monitored under the conditions of 1 Hz frequency and 1% strain.

[0062] 1.11 Moisture distribution

[0063] The surimi sample was made into a cylinder with a diameter of 20 mm and a height of 20 mm and placed in a nuclear magnetic resonance imaging instrument. The Carr-Purcell-Meiboom-Gill (CPMG) pulse sequence was used to measure the spin-spin relaxation time (T2). Parameter settings: resonance frequency was 21 MHz, 90° pulse width was 13.20 μs, sampling frequency was 200 kHz, repeat sampling waiting time was 3500 ms, number of accumulations was 4, and radio frequency time was 20 μs. Echo time (TE) was 0.2 ms, and the number of echoes was 8000. The obtained attenuation signal was fitted using MultiExp.Inv analysis software to obtain the component relaxation time T2.

[0064] 1.12 Free amino acids

[0065] Referring to the method of GB 5009.124-2016 Determination of Amino Acids in Foods: Weigh 2.0 g of surimi, add 15 mL of 5% (w / v) trichloroacetic acid and homogenize for 2 min, then sonicate for 5 min. Let the mixture stand at room temperature for 2 h, and then centrifuge at 4 °C and 10000 g for 10 min. Accurately pipette 5 mL of the supernatant, adjust the pH value to 2.0 with NaOH solution, then make up the volume to 25 mL with ultrapure water, filter through a 0.22-mm needle filter, and place the sample in an automatic amino acid analyzer.

[0066] The mobile phase was sodium acetate: methanol: acetonitrile = 1:2:2 (v / v), the UV detection wavelengths were 338 nm and 262 nm (proline), and the flow rate was 1.0 mL / min. FAA identification and quantification were completed according to the retention time and peak area installed in the instrument program. The concentration of FAAs was expressed as mg / 100 g.

[0067] 1.13 Electronic nose

[0068] Chop 2 g of surimi gel sample and put it into a 10-mL headspace vial, tighten the lid to seal, and let the sample stand at room temperature for 30 min. Measurement parameters: test temperature, 25 °C; sample flow rate, 400 mL / min; test time, 80 s; cleaning time, 100 s.

[0069] 1.14 Electronic tongue

[0070] Weigh 2 g of surimi sample, add 10 mL of ultrapure water, homogenize for 1 min. Take another 10 mL of ultrapure water to rinse the machine head and pour it into the homogenate. Ultrasonic for 5 min, centrifuge at 4 °C and 15,000 g for 15 min. Take the supernatant. Repeat the above operations for the precipitate, combine the two supernatants, filter with filter paper, and make up the volume to 80 mL.

[0071] 1.15 GC-IMS

[0072] Weigh 2 g of surimi and put it into a headspace vial, incubate at 60 °C for 20 min, the incubation rotation speed is 500 r / min, the injection needle temperature is 65 °C, and the injection volume is 500 μL.

[0073] Chromatographic conditions: FS-SE-54-CB-1 quartz capillary column (15 m × 0.53 mm × 0.5 μm); column temperature 60 °C; carrier gas is N2 (purity ≥ 99.999%); carrier gas flow rate program: initial flow rate 2.0 mL / min, hold for 2 min, then linearly increase to 100.0 mL / min within 18 min.

[0074] 1.16 Statistical analysis

[0075] Each index was measured in parallel more than 3 times, and the results were expressed as mean ± standard deviation. IBM SPSS Statistics 22.0 software was used for significance analysis, and P < 0.05 indicated significant differences. Origin 2021 software was used for plotting.

[0076] 2. Results and discussion

[0077] 2.1 pH value and water holding capacity

[0078] The pH value is a key factor affecting the gel properties of myofibrillar protein and is also an important indicator for evaluating food freshness. During the fermentation process, the pH values of each group of fish cakes showed a downward trend, mainly due to the metabolic activities of fermenting microorganisms such as lactic acid bacteria, which produced acidic substances such as lactic acid. According to Figure 2 A, as the fermentation time extended, the pH values of the experimental groups showed a trend of first decreasing and then slightly rising, while the pH value of the control group changed less and always fluctuated around 7.4. Within 0 - 4 h, the organic acids produced by the metabolism of lactic acid bacteria caused a significant decrease in pH. The larger the inoculation amount of the starter, the greater the decrease in pH value. The 3% group decreased to 5.88 at 4 h. This is because lactic acid bacteria began to multiply in large numbers and became the dominant bacteria, decomposing the carbohydrates in the fish cake and producing organic acids, thus resulting in different degrees of decrease in pH, indicating that the addition of the starter accelerated the acidification process; but after 6 - 8 h, the pH values of the 0.5%, 1%, and 2% groups slightly increased, which was related to the decrease in microbial activity in the later stage of fermentation, the reduction in the production of acidic substances, and the accumulation of alkaline substances (such as ammonia compounds) produced by protein degradation.

[0079] The water holding capacity is an important indicator to measure the quality of surimi products. During the fermentation process, the water holding capacity of each group of fish cakes decreased, and the water binding ability decreased. According to Figure 2 A, the water holding capacity of the control group fluctuated less during the whole fermentation process, always floating around 83%, showing a trend of first increasing and then decreasing overall. The overall trend of the 0.5% group was close to that of the control group, floating around 82% as a whole. Adding an appropriate amount of lactic acid bacteria starter can help improve the water holding capacity of surimi, thereby improving the taste and texture of surimi products. The fish cake with a 0.5% addition of lactic acid bacteria in the experimental group had the strongest water holding capacity.

[0080] 2.2 TVB-N and gel strength

[0081] TVB-N (total volatile basic nitrogen) is an important indicator to measure the freshness of surimi and the degree of protein spoilage. During the fermentation process, the TVB-N values of all groups of fish cakes were lower than 30 mg / 100 g, meeting the requirement of ≤30 mg / 100 g for total volatile basic nitrogen in prefabricated fishery products in GB 10136-2015 "National Food Safety Standard Fishery Products of Animal Origin". According to Figure 2 B, with the extension of fermentation time, the TVB-N values of each experimental group and the control group showed an overall upward trend. The TVB-N of the control group slowly increased from 4.40 mg / 100 g at the beginning to 4.61 mg / 100 g, showing a relatively stable increase; the TVB-N values of the 1%, 2%, and 3% groups increased slowly in the early stage of fermentation, indicating that lactic acid bacteria had a certain inhibitory effect on the decomposition of fish cake protein in the initial stage of fermentation; the rising speed accelerated in the later stage, and the higher the addition amount of lactic acid bacteria, the faster the rising speed in the later stage, indicating that with the increase of fermentation time, the growth and reproduction of microorganisms accelerated, and the microbial and enzymatic actions accelerated the decomposition of protein. The TVB-N value of the 0.5% group showed no obvious fluctuation at the beginning and finally decreased to 3.94 mg / 100 g, indicating that an appropriate amount of Lactobacillus plantarum had a certain inhibitory effect on the decomposition of fish cake protein. The fish cake with a 0.5% addition of lactic acid bacteria in the experimental group had the lowest TVB-N value and the highest freshness.

[0082] The size of gel strength reflects the firmness of the internal structure of surimi. The change of gel strength is related to the gelation process of protein and microbial metabolism. According to Figure 2B. During the fermentation process, the gel strength of each group of surimi increased. The gel strength of the control group first increased and then decreased, reaching a peak of 273.58 g·cm at about 6 h. The gel strength of the 0.5% group was significantly lower than that of the control group as a whole (p < 0.05). In the initial stage of fermentation, the gel strength decreased, and then reached the maximum value of 262.29 g·cm at 4 h. The change trend of the gel strength of the 1%-3% groups was similar to that of the control group, but higher than that of the control group as a whole, indicating that the addition of the starter culture was helpful to improve the gelation ability of surimi, thereby improving the taste and texture of surimi products. The gel strength of the fish cake with a lactic acid bacteria addition of 0.5% in the experimental group was the lowest.

[0083] 2.3 Texture

[0084] Texture characteristics are important indicators to measure the taste and texture of surimi products, and hardness reflects the sensory palatability of surimi. According to Table 2, with the change of fermentation time, the hardness of the control group and the experimental groups showed an overall upward trend. The hardness of the control group increased significantly in the early stage of fermentation. The cross-linking and aggregation between proteins in the fish cake led to an increase in hardness (p < 0.05). In the later stage of fermentation, the hardness of the control group remained at a relatively high level, and the degree of protein cross-linking had reached a relatively stable state. The hardness of the 0.5% group decreased slightly in the early stage of fermentation. The initial metabolism of lactic acid bacteria disrupted the interaction between protein molecules, resulting in a temporarily loose protein structure and a decrease in hardness. Subsequently, it gradually increased and reached the maximum value at 8 h. As fermentation progressed, the enzymes produced by lactic acid bacteria hydrolyzed proteins to produce small peptide segments, which could interact with other protein molecules, promoting protein cross-linking and aggregation, and the hardness gradually increased. The 1%-3% groups showed an upward trend. The hardness of the 1%-3% groups increased rapidly in the early stage because the higher lactic acid bacteria addition made the metabolic activities of microorganisms more vigorous, producing more enzymes, and these enzymes promoted the cross-linking reaction of proteins, resulting in a rapid increase in hardness.

[0085] According to Table 2, the trends of the control group and the 0.5% group were similar, showing an overall slow increase. This was because the cross-linking and aggregation of proteins made the structure of surimi more compact, requiring more force during chewing, resulting in an increase in chewiness. The chewiness of the 0.5% group was significantly lower than that of the control group. The metabolic activities of microorganisms made the structure of the fish cake relatively loose, requiring less force during chewing (p < 0.05). The trends of the 1%-3% groups were similar, showing an overall increase first and then a decrease. The chewiness increased rapidly in the early stage of fermentation because the higher lactic acid bacteria addition enabled the cross-linking reaction of proteins to proceed rapidly, making the structure of the fish cake very compact and the chewiness increased significantly. However, after reaching the peak at 4 h, it decreased rapidly. Excessive cross-linking led to an overly hard and brittle protein structure, which was easily damaged, resulting in a rapid decrease in chewiness.

[0086] According to Table 2, the elasticity of the control group, 0.5% group, and 1% group fluctuated less during the entire fermentation process and basically remained between 0.94 and 0.98. The interaction between protein molecules did not change significantly, so the elasticity remained relatively stable. The elasticity of the 2% and 3% groups decreased in the early stage of fermentation and increased in the later stage, but overall it was significantly lower than that of the control group. The higher addition amount of lactic acid bacteria made the metabolic activities of microorganisms too intense, and the enzymes produced had a strong hydrolysis effect on proteins, destroying the protein structure and resulting in a decrease in elasticity (p < 0.05).

[0087] Adhesiveness refers to the force required to separate a food surface from the tongue and teeth in the oral cavity, and it is generally negative. According to Table 2, the adhesiveness of the control group fluctuated less. The 0.5% group and 1% group both showed a trend of first decreasing and then increasing. The metabolic activities of lactic acid bacteria in the initial stage destroyed the adhesion between protein molecules, resulting in a gradual decrease in adhesiveness. The adhesiveness of the 2% group and 3% group increased steadily because the higher addition amount of lactic acid bacteria caused a large amount of substances to be produced by the metabolic activities of microorganisms, and these substances promoted the adhesion between protein molecules.

[0088] Table 2

[0089]

[0090] 2.4 Sensory evaluation

[0091] Sensory evaluation, as a means of directly judging the quality of food based on sensory experience, is the most intuitive method for evaluating the quality of surimi products. As can be seen from Table 3, after adding different contents of Lactobacillus plantarum, the flavor and overall acceptability of the fish cakes were significantly improved (p < 0.05). In terms of flavor (changed to in terms of smell and taste), the 0.5% group had the highest score at 4 h of fermentation, with obvious fishy freshness, fermentation fragrance, and weak fishy smell, which was significantly better than the control group (p < 0.05). This indicates that appropriate addition of Lactobacillus plantarum can improve the flavor of fish cakes. In terms of color, the color scores of the experimental groups were generally higher than those of the control group, indicating that the addition of the starter culture helps to improve the color uniformity and gloss of surimi products. In terms of texture, the 0.5% group had the highest texture score at 4 h of fermentation, with delicate meat texture and basically no small pores, showing the best performance. In terms of adhesiveness, the 0.5% group had a higher adhesiveness score at 4 h of fermentation and less residue in the mouth after swallowing. In terms of overall acceptability, the 0.5% group was significantly higher than the control group, indicating that appropriate addition of lactic acid bacteria can improve consumers' acceptance of surimi products (p < 0.05).

[0092] In summary, the overall acceptability of the 0.5% group was the highest, and the 1% group was the second.

[0093] Table 3: Sensory evaluation results of lactic acid bacteria-fermented fish cakes

[0094]

[0095]

[0096] 2.5 IDDSI Test

[0097] IDDSI (International Dysphagia Diet Standardization Initiative) provides global standards for assessing the levels of dysphagia foods. The control group and the 0.5% group were subjected to IDDSI tests, and the fork drip test, spoon tilt test, and fork compression test were used to confirm the level of fermented fish cakes as dysphagia foods. As Figure 3 and 4 shown, the flow of fish cakes through the fork teeth was observed in the fork drip test. The results showed that all fish cake groups piled up on the fork and did not drip from the fork teeth, indicating that the fish cakes were transitional foods (levels 5 / 6 / 7) within the IDDSI framework, which was consistent with the findings of Liang et al. Subsequently, the spoon tilt test was conducted to evaluate the adhesiveness and cohesiveness of the fish cakes. The results showed that all fish cake groups could maintain their original shape on the spoon and had sufficient cohesion. When the spoon was tilted and slightly shaken, the fish cakes easily slipped off the spoon, and this smoothness could reduce the swallowing resistance while avoiding food residue in the mouth or throat, enhancing swallowing safety. For the fork compression test, fish cake samples with dimensions of 1.5 cm × 1.5 cm were used to reduce the possibility of choking. In the fork compression test, a pressure of about 17 kPa that turned the thumb white was applied, relative to the pressure generated when the tongue squeezes food during swallowing. The results showed that when the thumb tip turned white, the fish cakes in the control group and the 0.5% group were both squeezed and deformed. However, in the 0.5% group, after the fork was removed, the fish cakes did not return to their original state and had obvious tooth marks, and these fish cakes were defined as level 6 (soft and one-bite size) dysphagia foods. In contrast, the control group completely returned to its initial state after the fork was removed, indicating that the control group was not within the framework of dysphagia foods defined by IDDSI. In summary, fish cakes with 0.5% addition of Lactobacillus plantarum were classified as level 6 (soft and one-bite size) dysphagia foods within the IDDSI framework and were suitable for dysphagia patients.

[0098] 2.6 Rheological Properties

[0099] Rheological properties can reflect the viscoelastic changes of fish cakes at different temperatures. According to Figure 5A. When the temperature rises from 25 °C to 55 °C, the G' of the control group's fish cakes shows a downward trend. The lowest values of G' for the control group's fish cakes are all around 50 °C. This is because the increased temperature causes the thermal motion of protein molecules to intensify, and some weak interactions between molecules are disrupted, temporarily reducing the elasticity. When the temperature rises from 55 °C to 90 °C, G' gradually increases. This is because the protein denatures and new cross-linking structures begin to form between molecules, thus enhancing the elasticity of the system, improving the ability to store elastic deformation, and the increase in G' at 0 h, 8 h, and 24 h in the control group is more obvious, which is consistent with the deformation of elasticity. According to Figure 5 B. As the temperature increases, the G' of the 0.5% lactic acid bacteria group also first decreases and then increases, but the decrease amplitude is relatively large. Endogenous proteolytic enzymes induce protein degradation and disrupt the gel network structure, resulting in a decrease in G'. And the temperature of the lowest G' value is slightly lower than that of the control group. This is because lactic acid bacteria metabolism can lower the denaturation temperature of proteins, causing the surimi to enter the gelation process earlier, resulting in reduced elasticity. As the temperature further increases, G′ increases and remains stable at 75 °C. This is called the "gel strengthening stage". Due to the denaturation and dissociation of myosin heavy chain (MHC) and the increase in the cross-linking degree between protein molecules, an irreversible thermal gel network is formed. The temperature of the lowest G' value at 4 h and 8 h in the 0.5% lactic acid bacteria group is lower, which is consistent with the change in gel strength.

[0100] The viscous characteristics of surimi are represented by G”. The larger the G″ value, the greater the viscosity of the surimi system, the stronger the cross-linking of the gel, and the easier it is to gelate. According to Figure 5 C and D. As the temperature increases, the G” of both groups of fish cakes first rises and then falls. During the rising stage, the increased temperature causes the thermal motion of protein molecules to intensify, increasing the friction and hindrance between molecules, resulting in an increase in the viscosity of the system. During the falling stage, the protein further denatures, forming a more stable structure between molecules, reducing the relative movement between molecules, and thus reducing the viscosity. After 16 h of fermentation, the G” of the 0.5% lactic acid bacteria group is overall higher than that of the control group, indicating that lactic acid bacteria fermentation changes the interaction forces between protein molecules, resulting in an increase in the viscosity of the system, which is consistent with the change in viscosity.

[0101] 2.7 Water distribution

[0102] LF-NMR identifies various states of water in surimi by evaluating the relaxation characteristics of hydrogen atomic nuclei in a magnetic field. T21 (0.1 - 10 ms) represents bound water, that is, the monolayer water closely related to the polar groups on the surface of macromolecules; T22 (10 - 100 ms) represents immobile water, that is, the water trapped within the muscle fiber network; T23 (100 - 10,000 ms) represents free water, which can migrate freely and exists outside the muscle protein matrix. According to Figure 6For A and B, the addition of lactic acid bacteria shifted the peak of T22 fish cakes to the left, indicating a shortening of the relaxation time and a decrease in the mobility of water molecules. Since fermentation promoted the unfolding and cross-linking of protein molecules, it helped to form a compact network structure, thereby encapsulating more water molecules in the gel network. From Figure 6 As can be seen from C, during the fermentation from 0 to 8 h, the proportion of P22 in the 0.5% lactic acid bacteria group increased slightly and was significantly higher than that of the control group, indicating that the addition of lactic acid bacteria promoted the denaturation and aggregation of proteins, formed a tighter network structure, and accelerated the transformation of water from bound water to free water (p < 0.05). After 8 h of fermentation, the proportion of free water increased, the proportion of immobile water decreased, and the immobile water gradually transformed into free water, increasing the mobility of water. Due to the destruction of the protein structure caused by the fermentation of Lactobacillus plantarum, the immobile water bound to the protein was released and transformed into free water.

[0103] 2.8 Free Amino Acids

[0104] According to Table 4, the amino acids with relatively high contents in the two groups of fish cakes were Tau, Gly, Ala, Lys, and His. As a conditionally essential amino acid, Tau plays an important role in the cardiovascular, nervous, and visual systems; Gly contributes to the sweetness of fish, can remove salty and bitter tastes, has a synergistic effect with other umami substances, and the content in the 0.5% lactic acid bacteria group was higher than that of the control group; Ala is a sweet amino acid with a slightly bitter taste and also has a synergistic effect with Glu, etc.; Lys is the first essential amino acid for the human body and can undergo transamination reactions in the body; His itself is bitter, but it enhances the flavor and forms the "meat aroma" characteristics in some seafood products.

[0105] In the control group, the content of sweet amino acids was relatively stable in the early stage of fermentation and decreased in the later stage; the content of umami amino acids first increased and then decreased, reaching a relatively high value at 16 h; the content of bitter amino acids increased rapidly in the early stage of fermentation, then fluctuated, and the increase in the content of bitter amino acids in the later stage of fermentation would have a negative impact on the flavor.

[0106] In the 0.5% lactic acid bacteria group, the contents of sweet amino acids and umami amino acids showed an upward trend in the early stage of fermentation, and the content in the 0.5% lactic acid bacteria group was higher than that of the control group, reaching a relatively high level at about 16 h. This was because the protease produced by lactic acid bacteria promoted the hydrolysis of proteins, releasing more free amino acids. In the later stage of fermentation, with the metabolism of microorganisms, some amino acids were further utilized or transformed by microorganisms, resulting in a decrease in the contents of sweet and umami amino acids. The content of bitter amino acids fluctuated during the fermentation process, and the overall content was slightly lower than that of the control group, which was related to the change in the transformation pathway of amino acids by the metabolic activities of Lactobacillus plantarum.

[0107] Table 4: Changes in the content of free amino acids in lactic acid bacteria-fermented fish cakes (mg / 100g)

[0108]

[0109]

[0110]

[0111] 2.9 Electronic nose

[0112] An electronic nose was used to measure the volatile flavors of Alaska pollack surimi cakes fermented by lactic acid bacteria for different times, and the measured data were subjected to principal component analysis (PCA). The electronic nose radar analysis can reveal the overall situation of the signal response intensity of the sensor to different samples and the differences between samples. From Figure 7 Figure A, it can be seen that as the fermentation progresses, the response values of all sensors gradually increase. The T30 / 1, T40 / 2, and T70 / 2 sensors can indicate rancid smell, and the T40 / 1 sensor indicates earthy mold smell. The LY2 / g CTl and LY2 / GH sensors are specifically responsive to fishy smell. The response values of these sensors in the control group gradually increase. This is because proteins are decomposed to produce substances such as amines, and fats are oxidized to produce compounds such as aldehydes and ketones, bringing bad flavors to the surimi cakes. From Figure 7 Figure B, it can be seen that the response values of T30 / 1, T40 / 2, T40 / 1, and T70 / 2 in the 0.5% lactic acid bacteria group first decrease and then increase. This is due to the metabolites of lactic acid bacteria, such as organic acids and bacteriocins, which inhibit the growth of some microorganisms, thereby reducing the volatile compounds produced by these microorganisms; at the same time, the metabolism of lactic acid bacteria itself will also produce new volatile components.

[0113] According to Figure 7 Figure C, the total contribution rate of the first principal component (PC1) and the second principal component (PC2) in the control group is 96.3% (>90%), indicating that the two principal components fully cover the main information characteristics of the samples. The distribution characteristics of each group of data on the first principal component are the main factors determining the discrimination effect. The distribution of surimi cakes at the 0h - 8h time points in the figure is relatively concentrated, indicating that at the initial stage of fermentation, the changes in the volatile components of surimi cakes are small, and the similarity between samples is high; the surimi cake samples at 16h and 24h have a high similarity; the samples at 36h and 48h are significantly deviated from the initial samples and are relatively dispersed. This indicates that at the later stage of fermentation, the volatile components of surimi have changed greatly, and the differences between samples have increased. This is because the components such as proteins and fats in surimi cakes are gradually decomposed, and microorganisms grow and reproduce, producing new volatile compounds, resulting in changes in the positions of samples in the PCA score plot. According to Figure 7D. The total contribution rate of the first principal component (PC1) and the second principal component (PC2) of the 0.5% lactic acid bacteria group is 96.7% (>90%), indicating that the two principal components fully cover the main information characteristics of the samples. The distribution of samples in the 0.5% lactic acid bacteria group is relatively concentrated, indicating that the addition of lactic acid bacteria has slowed down the change rate of volatile components of surimi to a certain extent, making the quality change of surimi relatively stable. Because the acidic substances and bacteriocins produced by lactic acid bacteria during metabolism inhibit the growth of other microorganisms, reduce the production of undesirable volatile compounds, and affect the decomposition and transformation process of the components of surimi itself.

[0114] 2.10 Electronic Tongue

[0115] According to Table 5 and Figure 8 A, B, in terms of sourness, the AHS sensor response values ​​of the control group and the 0.5% lactic acid bacteria group increased in the early stage of fermentation, and the 0.5% lactic acid bacteria group decreased more significantly in the later stage. This is because plant lactobacillus fermented to produce organic acids; in the later stage of fermentation, the organic acids in the 0.5% lactic acid bacteria group further participated in other metabolic reactions, resulting in a weakening of the sourness. In terms of saltiness, the CTS sensor response values ​​of both groups showed a trend of first increasing and then decreasing, and the 0.5% lactic acid bacteria group was relatively stable, due to the interaction between microbial metabolites and salt ions. In terms of umami, the umami of the control group was at a low level and did not change much, while the umami of the 0.5% lactic acid bacteria group showed an upward trend, indicating that lactic acid bacteria promoted the production of umami substances. In terms of sweetness, the sweetness of the control group continued to decrease with the progress of fermentation, while the sweetness of the 0.5% lactic acid bacteria group showed a trend of first increasing and then decreasing, due to the synergistic effect of lactic acid bacteria metabolites and various flavor substances. In terms of bitterness, the bitterness of both groups of fish cakes first increased and then decreased. The protein, fat and other components in the fish cakes were decomposed by microorganisms and enzymes to produce some bitter substances. The bitterness of the 0.5% lactic acid bacteria group decreased more significantly, indicating that lactic acid bacteria accelerated the metabolism of bitter substances in the early stage of fermentation.

[0116] according to Figure 8C. The total contribution rate of the first principal component (PC1) and the second principal component (PC2) of the control group is 98.6% (>90%), indicating that the two principal components fully cover the main information characteristics of the samples. PC1 contains most of the information in the original electronic tongue data and is the main factor in distinguishing different samples, but PC2 also accounts for a considerable proportion of the contribution rate and plays an important role in distinguishing samples. The samples fermented for 0h, 4h, and 8h are more concentrated in the upper right area of ​​the figure, indicating that in the early stage of fermentation, the taste characteristics of fish cakes are relatively similar. As fermentation progresses, the samples of 16h and 24h as well as 36h and 48h obviously deviate from the distribution area of ​​the early samples. This shows that in the later stage of fermentation, the taste characteristics of fish cakes have undergone major changes. This is due to the growth and metabolism of microorganisms, the decomposition of components, and other reasons, which cause the electronic tongue to change the response value of different taste sensors, and then change its position in the PCA score graph. According to Figure 8 D. The total contribution rate of the first principal component (PC1) and the second principal component (PC2) of the 0.5% lactic acid bacteria group is 96.7% (>90%), indicating that the two principal components fully cover the main information characteristics of the samples. The samples fermented for 8h, 16h and 24h are concentrated, indicating that the addition of lactic acid bacteria has slowed down the rate of change of the taste characteristics of fish cakes to a certain extent, making the taste of fish cakes relatively more stable during the fermentation process. The samples fermented for 48h are concentrated in the lower left corner of the figure, indicating that the taste characteristics of fish cakes have changed significantly in the later stage of fermentation. The samples in the control group have a clear dispersion trend in the later stage of fermentation, indicating that their taste characteristics have changed significantly. The samples in the 0.5% lactic acid bacteria group are relatively concentrated, indicating that the addition of lactic acid bacteria helps to maintain the relative stability of the taste characteristics of fish paste and has a positive effect on the flavor stability of fish paste.

[0117] Table 5: Electronic tongue sensor response values ​​of lactic acid bacteria fish cake during fermentation

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[0119]

[0120] 2.11GC-IMS

[0121] GC-IMS (gas chromatography-ion mobility spectrometry) technology can effectively separate and identify volatile flavor substances. GC-IMS was used to separate and identify the volatile substances in fish cakes. The fingerprint results of the volatile substances in fish cakes are shown in Figure 9 Table 6 and Figure 9It shows the complete volatile substance information during the fermentation process of fish cakes and the differences in the concentrations of volatile substances among fish cakes. It can be seen that there are obvious differences in the types and contents of volatile odor substances between the 0.5% lactic acid bacteria group and the control group during the fermentation process. As the fermentation progresses, the volatile substances in the fish cakes begin to decrease or even disappear, but new volatile substances also appear. A total of 84 volatile flavor substances were detected in 14 groups of samples. Using the IMS migration time database and the NIST 2014 gas phase retention index database for two-dimensional qualitative analysis, 84 known volatile components were identified as shown in Table 6. The 84 volatile flavor substances mainly include 11 alcohols, 16 aldehydes, 16 ketones, 18 esters, 4 alkenes, 3 furans, 3 thioethers, 3 amines, 2 ethers, 2 acids and other types.

[0122] Alcohol compounds are partially reduced from aldehydes under the action of reductase and have a relatively mild plant aroma and fresh fragrance. The alcohol content in the 0.5% lactic acid bacteria group gradually increases, indicating that the metabolism of lactic acid bacteria contributes to the formation of 4-methyl-2-pentanol and 2-methylpropanol, improving the flavor of fish cakes. Ketone substances make a certain contribution to eliminating fishy smell. Esters are the main contributors to the fruity and sweet flavors in surimi products. The ester content in the 0.5% lactic acid bacteria group is always higher than that in the control group, adding a fresh feeling to the fish cakes.

[0123] Table 6: GC-IMS global region set integration parameters of fish cakes

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[0125]

[0126]

[0127] To sum up, by studying the effects of different addition amounts of Lactiplantibacillus plantarum LP90 starter on various indicators during the fermentation process of fish cakes, the present invention shows that the addition amount of lactic acid bacteria and the fermentation time significantly affect the pH value, water holding rate, TVB-N value, gel strength, texture properties, sensory quality and IDDSI test results of fish cakes. Within a certain range, adding Lactiplantibacillus plantarum LP90 can improve the flavor, texture and overall acceptance of fish cakes and inhibit the increase of TVB-N value. Lactic acid bacteria contribute to improving the water holding capacity of fish cakes, inhibiting the spoilage and oxidation of fish cakes, improving the texture properties and rheological properties of fish cakes, and optimizing the water distribution of fish cakes. The fermentation of Lactiplantibacillus plantarum LP90 has a significant impact on the flavor of Alaska pollack fish cakes. In actual production, the flavor quality of fish cakes can be optimized by controlling the fermentation time and the addition amount of Lactiplantibacillus plantarum, providing a theoretical basis for the development of fermented Alaska pollack fish cake products with unique flavors and more suitable for specific populations.

[0128] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A preparation method of a lactic acid bacteria-fermented easy-to-swallow fish cake, characterized in that, Including the following steps: (1) Thawing and chopping: Thaw the frozen surimi at low temperature and adjust the moisture content. First, chop the surimi without adding ingredients, then add salt and continue chopping, and then add starch and continue chopping to form surimi gel; (2) Fermentation by Lactobacillus plantarum: Dissolve Lactobacillus plantarum in water and add it to the surimi gel for chopping; (3) Stuff the uniformly mixed surimi into casings and carry out fermentation by Lactobacillus plantarum under constant temperature and appropriate humidity conditions; (4) Heating and ripening: Subject the fermented surimi to a water bath at 40 °C for 30 min, and then transfer it to a water bath at 90 °C for 30 min to obtain fermented fish cakes; (5) Freezing and storage: After heating, quickly cool the fermented fish cakes in ice water and store them at low temperature to obtain the product.

2. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 1, characterized in that, In step (1), the frozen surimi is frozen surimi of Alaska pollack.

3. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 1, wherein, In step (1), the process of thawing and chopping is as follows: The frozen surimi is semi-thawed at 4 °C, the moisture content is adjusted to 80%, chopped without adding ingredients for 5 min, 2% salt and 5% starch are added according to the mass of the surimi, and then chopped for another 10 min.

4. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 1, characterized in that In step (2), the Lactobacillus plantarum is Lactobacillus plantarum LP 90, and the addition amount accounts for 0.1%-5% of the mass of the surimi.

5. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 4, wherein, In step (2), the addition amount of Lactobacillus plantarum LP 90 accounts for 0.5%-3% of the mass of the surimi.

6. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 1, characterized in that, In step (3), the diameter of the casing used for stuffing is 20-40 mm.

7. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 6, characterized in that, In step (3), the diameter of the casing used for stuffing is 30 mm.

8. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 1, characterized in that In step (3), the fermentation temperature is 30 °C, the fermentation humidity is 85%, and the fermentation time is 2-10 h.

9. The preparation method of the easily swallowable fish cake fermented by lactic acid bacteria according to claim 8, wherein, In step (3), the fermentation temperature is 30 °C, the fermentation humidity is 85%, and the fermentation time is 8 h.

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