Aspergillus oryzae fermentation liquor smoked skipjack and preparation method and application thereof

Abstract

The invention relates to aspergillus oryzae fermentation liquor smoked skipjack and a preparation method and application thereof, and belongs to the technical field of skipjack processing. The preparation method of the aspergillus oryzae fermentation liquor smoked skipjack comprises the following steps: (1) steaming pretreated skipjack blocks, draining, airing, soaking in a smoking solution, draining, and drying to obtain liquid smoked skipjack blocks; and (2) inoculating the liquid smoked skipjack with an aspergillus oryzae spore suspension for fermentation to obtain the aspergillus oryzae fermentation liquid smoked skipjack. The processing efficiency is improved by using the liquid smoking liquid and a soaking mode, and sensory indexes such as color, elasticity and chewiness of the fish meat are improved; aspergillus oryzae is utilized for inoculation and fermentation, the fermentation period can be effectively shortened, and meanwhile the nutrition level and the flavor are improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of skipjack processing, in particular to a rice koji fermentation liquid smoked skipjack segment and a preparation method and application thereof. BACKGROUND

[0002] Skipjack has tender meat and is characterized by low fat and high protein, and is rich in various nutrients such as minerals, unsaturated fatty acids and vitamins. Skipjack segment is a traditional Japanese fermented fish product made of skipjack. It is divided into several types, such as raw segment, naked segment and dry segment, which have important significance in Japanese culture and cooking. The final product is a fermented mature dry segment, which is famous for its unique rich flavor, hard texture and long shelf life.

[0003] In recent years, liquid smoking technology has become a research hotspot due to its strong controllability, low polycyclic aromatic hydrocarbon (PAHs) content and other advantages. Liquid smoking liquid is usually prepared by pyrolysis of wood or coconut shell and contains components such as phenols, organic acids and carbonyl compounds, which not only give the product a unique flavor and color, but also have antibacterial and antioxidant effects.

[0004] The traditional skipjack processing flow includes abdominal dissection and cleaning, cooking to stabilize muscle tissue, smoking and dehydration, and natural fermentation ripening for several months relying on the natural microbial community in the raw segment. This multi-step process has defects such as long fermentation period, difficulty in accurately controlling process parameters, and unstable product quality. Therefore, how to effectively improve the quality of fermented skipjack products and significantly shorten the fermentation period has become a problem to be solved. SUMMARY

[0005] Therefore, the present application provides a rice koji fermentation liquid smoked skipjack segment and a preparation method and application thereof, which significantly improves the overall quality and shelf life of skipjack products and solves the problems of severe water loss, dry and hard taste and insufficient flavor retention in traditional processes.

[0006] The first aspect of the present application provides a preparation method of a rice koji fermentation liquid smoked skipjack segment, comprising the following steps:

[0007] (1) The pre-processed skipjack pieces are steamed and treated, drained and dried, then soaked in a smoking liquid, drained and dried to obtain a liquid smoked raw segment;

[0008] (2) The liquid smoked raw segment is inoculated with a rice koji spore suspension for fermentation to obtain a rice koji fermentation liquid smoked skipjack segment.

[0009] Preferably, the specific process of step (1) is: steaming the tuna blocks at 100-105℃ for 30 min, draining the steamed material, and removing fish bones and skin after cooling to obtain tuna meat; immersing the tuna meat in a smoke solution with an additive amount of 4-8%, and cold-sealing and soaking at 4℃ for 30-50 min, then draining the tuna meat on a sieve, and drying in an oven at 120℃ for 3-4 h to obtain liquid smoked tuna.

[0010] Preferably, in step (1), the smoke solution is hickory wood smoke solution.

[0011] Preferably, in step (1), the pretreatment process of the tuna blocks is: removing the head, internal organs and fins after thawing the tuna, washing to remove blood and mucus, washing the abdominal and dorsal muscle tissues with tap water, and cutting into blocks with a size of 6 cm x 4 cm x 2 cm, obtaining tuna blocks, immersing the tuna blocks in a 5-11% volume fraction of salt solution at 4℃ for 15 min, and then rinsing the surface with running water to remove residual salt water and blood water, obtaining pretreated tuna blocks.

[0012] Preferably, the specific process of step (2) is: uniformly applying Aspergillus oryzae spore suspension with a concentration of 10 8 spore / ml at an inoculum of 0.5-1% to the surface of the liquid smoked tuna, and placing it in a constant temperature and humidity incubator at 30℃ and a relative humidity of 75% for 28 days, sampling at 0d, 14d, 21d, 28d, 35d for intervention operation to obtain liquid smoked tuna fermented with Aspergillus oryzae.

[0013] Preferably, the specific process of the intervention operation is: removing the liquid smoked tuna at 0d, 14d, 21d, 28d and placing it in a 100℃ oven for 15 min, removing the dense mold mycelium on the surface after cooling, and for samples that still need to continue fermentation after the intervention operation, re-inoculating the Aspergillus oryzae spore suspension and placing it back in the incubator for continued fermentation until the fermentation cycle is completed.

[0014] Preferably, the concentration of the Aspergillus oryzae spore suspension is 10 8The preparation process of the 10 spore / ml Aspergillus oryzae spore suspension is as follows: Aspergillus oryzae is subcultured in malt extract medium, cultured at 30°C for 7 days to obtain Aspergillus oryzae liquid; the Aspergillus oryzae liquid is uniformly coated on a PDA plate, cultured at 30°C for 4-7 days until yellow-green spores grow, 2 mL of 0.9% NaCl solution is added to the PDA plate, spores are scraped using a sterilized and cooled inoculation shovel, residual spores are washed with 1 mL of normal saline, transferred to a centrifuge tube and diluted with normal saline to 10 mL, vortexed, centrifuged at 5000 r / min for 5 min, the supernatant is discarded, and spore precipitate is obtained; then 30 mL of 0.9% NaCl solution is added for resuspension and washing, the supernatant is discarded after centrifugation; 5 mL of normal saline is added and vortexed to obtain a spore suspension, which is diluted with 0.9% NaCl solution to obtain a spore suspension with a concentration of 10 8 Aspergillus oryzae spore suspension;

[0015] Preferably, the Aspergillus oryzae is purchased from the China Industrial Microbial Culture Collection Center, with a strain number of CICC2339 and a classification name of Aspergillus oryzae.

[0016] Preferably, the method further comprises step (3) of vacuum preserving the Aspergillus oryzae fermented liquid smoked bonito flakes at room temperature.

[0017] The second aspect of the present application also provides an Aspergillus oryzae fermented liquid smoked bonito flake, which is prepared by the above method, has a water content of 13%, a volatile basic nitrogen content of 200 mg / 100 g, and a hardness of 36592 g.

[0018] The third aspect of the present application also provides application of the above Aspergillus oryzae fermented liquid smoked bonito flake in bonito food.

[0019] Compared with the prior art, the present application has the following beneficial effects:

[0020] (1) The present application uses liquid smoking liquid to improve processing efficiency through soaking, and improves sensory indexes such as fish color, elasticity, and chewiness.

[0021] (2) The present application uses Aspergillus oryzae inoculation and fermentation to effectively shorten the fermentation period, while improving the nutritional level and flavor. DETAILED DESCRIPTION

[0022] In order to more clearly illustrate the technical solutions of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the description of the present application or the prior art. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creating any creative labor.

[0023] Figure 1 The effect of salt solution pickling on the hardness (A), chewiness (B), cohesiveness (C), resilience (D) of the section is shown in the figure.

[0024] Figure 2 The effect of salt solution pickling on the sensory score of the section is shown in the figure.

[0025] Figure 3 The effect of the amount of smoking liquid added on the hardness (A), chewiness (B), cohesiveness (C), resilience (D) of the section is shown in the figure.

[0026] Figure 4 The effect of the amount of smoking liquid added on the sensory score of the section is shown in the figure.

[0027] Figure 5 The effect of liquid smoking time on the hardness (A), chewiness (B), cohesiveness (C), resilience (D) of the section is shown in the figure.

[0028] Figure 6 The effect of liquid smoking time on the sensory score of the section is shown in the figure.

[0029] Figure 7 The effect of drying time after liquid smoking on the hardness (A), chewiness (B), cohesiveness (C), resilience (D) of the section is shown in the figure.

[0030] Figure 8 The effect of drying time after liquid smoking on the sensory score of the section is shown in the figure.

[0031] Figure 9 The response surface and contour diagram of the effect of the interaction of various factors on the sensory score of liquid smoked sections is shown in the figure.

[0032] Figure 10 The response surface and contour diagram of the effect of the interaction of various factors on the hardness of liquid smoked sections is shown in the figure.

[0033] Figure 11 The response surface and contour diagram of the effect of the interaction of various factors on the cohesiveness of liquid smoked sections is shown in the figure.

[0034] Figure 12 The response surface and contour diagram of the effect of the interaction of various factors on the chewiness of liquid smoked sections is shown in the figure.

[0035] Figure 13 The change of pH (A), moisture content (B), TVB-N (C), TBARS (D), AA-N (E), TA (F) during fermentation is shown in the figure. DETAILED DESCRIPTION

[0036] In order to make the purpose, technical scheme and advantages of the present application clearer, the technical scheme of the present application will be described clearly and completely below in conjunction with the drawings in the present application. Obviously, the described embodiments are some but not all of the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of the present application.

[0037] The experimental methods used in the embodiments of the present application are conventional methods unless otherwise specified.

[0038] In the following examples, all raw materials can be obtained by commercial purchase or conventional methods unless otherwise specified.

[0039] Aspergillus oryzae (strain number CICC 2339) was purchased from China Industrial Microbial Culture Collection Center (classified as Aspergillus oryzae); skipjack tuna was purchased from Hainan Yunfu Fishery Co., Ltd.; Wright mountain walnut wood smoke flavoring juice smoke liquid was purchased from Shenzhen Oemuhui Trade Co., Ltd.; edible salt was purchased from Zhongyan Shanghai Salt Industry Co., Ltd.; high-temperature cooking bags, tweezers, sealing boxes, and vacuum packaging bags were commercially available.

[0040] Disodium ethylenediaminetetraacetate, 2-thiobarbituric acid, potassium chloride, formaldehyde standard solution, trichloroacetic acid, sodium hydroxide, hydrochloric acid, and sodium chloride were all domestic analytical pure and purchased from Hainandao Science and Technology Co., Ltd.; copper sulfate, potassium hydroxide, ethanol, sodium chloride, methyl red indicator, bromocresol green indicator, boric acid, and formaldehyde were all analytical pure and provided by National Pharmaceutical Group Chemical Reagent Co., Ltd.

[0041] Example 1: A preparation method of Aspergillus oryzae fermentation liquid smoked skipjack tuna, comprising the following steps:

[0042] (a) Raw material pretreatment: The frozen skipjack tuna was thawed at 4°C for 12 h, and then rinsed with running water for 30 min to remove the head, internal organs, fins, and scales, and to clean the abdominal cavity blood and mucus; the abdominal and dorsal muscles were cut into 6 cm x 4 cm x 2 cm blocks.

[0043] (b) Salt curing and dehydration: The fish blocks were immersed in a 7% (w / v) salt solution and cured at 4°C for 15 min; the surface salt was then rinsed off with running water at 5-10°C, and the fish blocks were drained.

[0044] (c) Cooking and shaping: The fish blocks were placed flat on a tray and steamed at 100-105°C for 30 min; the fish blocks were then drained for 15 min, and the fish bones and skin were removed after cooling.

[0045] (d) Liquid smoking process: The fish blocks were immersed in 6.7% (v / v) walnut wood smoke liquid and soaked at 4°C for 48 min; the fish blocks were then drained for 15 min, and dried in an oven at 120°C for 3.5 h to obtain the crude tuna.

[0046] (e) Aspergillus oryzae inoculation fermentation:

[0047] Strain activation and spore suspension preparation: Aspergillus oryzae (purchased from China Industrial Microbial Culture Collection Center, strain number CICC 2339, classified as Aspergillus oryzae) was inoculated on PDA plates and cultured at 30°C for 7 days, and then diluted with physiological saline to prepare a 10 8 spore / mL spore suspension;

[0048] Inoculation: the spore suspension was uniformly coated on the surface of the section at an inoculation amount of 0.5% (v / w);

[0049] Fermentation: placed in a constant humidity incubator at 30°C and RH 75% for fermentation for 28 days;

[0050] Termination: after the fermentation was completed, the sample was taken out and dried in an oven at 100°C for 15 min to remove the surface mycelium, and the finished product was obtained and stored in a vacuum at room temperature.

[0051] Example 2: Optimization of Aspergillus oryzae fermentation liquid smoked bonito section conditions

[0052] Based on the description in Example 1 above, the conditions for Aspergillus oryzae fermentation liquid smoked bonito section were optimized.

[0053] I. Test method

[0054] 1. Single factor experiment of liquid smoked bonito section processing technology

[0055] Under 4°C refrigeration conditions, use 3, 5, 7, 9, 11% salt solution (w / v) for pickling and soaking, add 6% smoke liquid, soak for 30 min, and dry for 3 h to determine the optimal salt solution pickling.

[0056] After optimal salt solution pickling, select 0, 2, 4, 6, 8% smoke liquid addition amount (v / v), soak for 30 min, and dry for 3 h to determine the optimal smoke liquid addition amount.

[0057] After optimal salt solution pickling, select the optimal smoke liquid addition amount under sealed 4°C refrigeration conditions, and soak for 10, 30, 50, 70, 90 min, and dry for 3 h to determine the optimal soaking time.

[0058] After optimal salt solution pickling, select the optimal smoke liquid addition amount and soaking time under sealed 4°C refrigeration conditions, and after airing, select 2, 2.5, 3, 3.5, 4 h as the single factor to determine the optimal drying time.

[0059] 2. Response surface experiment of liquid smoked bonito shank processing technology

[0060] Based on the results of single factor experiment, the optimal processing parameters were determined by response surface experiment design and model establishment (Table 1).

[0061] Table 1. Factor levels of response surface experiment design

[0062]

[0063] 3. Sensory evaluation

[0064] It is very difficult to select a sensory evaluation method because untrained personnel cannot accurately judge the description of sensory indicators. Considering this factor, a consumer-oriented sensory evaluation method was used in this application, which almost does not require training, emotional testing method, or acceptance testing method.

[0065] Six tasters were asked to rate only their preferences, with a rating scale of 0 to 10, with 10 being the best option and 0 being the worst option. There are five rating indices, including color, odor, taste, texture state, overall acceptability, and sensory grade evaluation criteria are shown in Table 2. All shanks used for sensory evaluation need to be dried for 1 h before sensory evaluation.

[0066] Table 2. Sensory evaluation criteria for liquid smoked bonito shank (full score 50)

[0067]

[0068] 4. Determination of physicochemical indicators of liquid smoked bonito shank

[0069] (1) Texture: Liquid smoked bonito shank was cut into appropriate 4 cm x 2 cm x 1 cm cubes using a texture analyzer. Texture profile analysis (TPA) analysis was performed with the following conditions: probe selection P / 36R, displacement: 10.000 mm; strain: 30.0 %, trigger point 5 g, pre-test speed: 1.00 mm / sec, mid-test speed: 1.00 mm / sec, post-test speed: 1.00 mm / sec. Liquid smoked bonito shank samples were placed on the probe base, and each group was measured in triplicate. Hardness (g), chewiness (g), gumminess (g), and resilience were selected as texture indicators. Each sample was measured in triplicate.

[0070] (2) Color difference: The color difference of the product was measured using a colorimeter to measure the L , a , b values, with a D65 light source. The colorimeter was calibrated black and white (calibration parameters: black calibration L a and b are 0, white calibration L a and b are 87.62, -0.77 and 1.21, respectively), measured at D65 illuminant, 10° angle, and each sample was measured in triplicate.

[0071] (3) Moisture: measured by a rapid moisture analyzer.

[0072] (4) pH determination: The liquid smoked fish muscle was crushed by a high-speed crusher, 2.0 g of the crushed fish muscle was weighed, 18 mL of potassium chloride solution was added, then it was placed for 30 min, filtered, and the pH of the filtrate was determined by a pH meter. Each sample was measured in triplicate.

[0073] 5. Preparation of rice koji fermentation liquid smoked tuna

[0074] The rice koji was purchased from China General Microbiological Culture Collection Center. The strain was subcultured in malt extract medium and cultured at 30 °C for 7 days. The rice koji liquid was evenly coated on PDA plates, and cultured at 30 °C for 4-7 days until the yellow-green spores were grown. 2 mL of 0.9 % NaCl was absorbed into the PDA plate, and the spores were scraped with a sterile spatula, then the residual spores were washed with 1 mL of physiological saline, transferred to a centrifuge tube and supplemented with physiological saline to 10 mL, mixed and vortexed, centrifuged at 5000 r / min for 5 min, and the supernatant was discarded to obtain the spore precipitate. Then, 30 mL of 0.9 % NaCl was added for washing, and the supernatant was discarded after centrifugation, and 5 mL of physiological saline was added to vortex to obtain the spore suspension. The spore suspension was diluted with 0.9 % NaCl to 10 8 spores / mL. Subsequently, the rice koji spore suspension was evenly coated on the surface of the tuna tuna for fermentation. It was divided into three groups, i.e., the inoculation amount was 0 %, 0.5 % and 1 %, respectively, and placed in a constant temperature and humidity incubator at 30 °C, RH = 75 % for fermentation. At 0 d, 14 d, 21 d, 28 d and 35 d, samples were taken from the three groups, dried at 100 °C for 15 min to remove the dense mold on the surface, and then continued to ferment until the fermentation was completed to obtain the final rice koji fermentation liquid smoked tuna product.

[0075] 6. Determination of the physicochemical indexes of rice koji fermentation liquid smoked tuna

[0076] (1) Determination of moisture content: 2.00 g of crushed fish meat was weighed, 18 mL of 0.1 mol / L KCl was added, and it was placed for 30 min. The pH of the filtrate was determined by a pre-calibrated Mettler-Toledo S210 pH meter. Each sample group was measured in triplicate and the average value was taken.

[0077] (2) pH determination: 3.60 g of crushed dried fish powder was weighed and measured using an infrared rapid moisture meter (Mettler-Toledo HB43-S). Each sample group was measured three times and the average value was taken.

[0078] (3) TVB-N determination: According to GB5009.228 standard.

[0079] (4) TBARS determination: 2 g of sample (accurate to 0.01 g) was weighed into a 50 mL centrifuge tube, 20 mL of trichloroacetic acid mixture was accurately added, shaken, sealed with a plug, vortexed for 2 min, and placed for 30 min. Filter with a 0.22 um filter membrane, 5 ml needle tube, accurately take 5 mL of the above filtrate into a 50 mL centrifuge tube, take another 5 mL of trichloroacetic acid mixture as sample blank, respectively add 5 mL of thiobarbituric acid (TBA) aqueous solution, plug, mix well, place in 90℃ water bath for 30 min, take out, cool to room temperature. Place 200ul liquid in a 96-well enzyme-coated plate, parallel point three samples, measure the absorbance at 532 nm.

[0080] (5) Amino acid nitrogen and total acid determination

[0081] Accurately weigh 2.50 g of sample into a centrifuge tube, add 25 mL of 50℃ pure water, homogenize for 1 min, then add 50℃ pure water to 50 mL; water bath at 50℃ for 30 min, cool to room temperature, filter with double-layer filter paper, and take the filtrate for use. Total acid: accurately take 20.00 mL of the above filtrate into a 200 mL beaker, add 60 mL of water and mix well. Start the magnetic stirrer, titrate with 0.050 mol / L NaOH standard solution until the pH meter (previously calibrated) indicates pH 8.2, record the consumption of sodium hydroxide standard titration solution V1, and calculate the total acid content according to the consumption of sodium hydroxide standard titration solution. Amino acid nitrogen: quickly add 10.00 mL of formaldehyde solution (36-40%) to the above titrated total acid solution and mix well, immediately continue titration with 0.050 mol / L NaOH standard solution to pH 9.2, record the consumption of sodium hydroxide standard titration solution V2, and calculate the amino acid nitrogen content according to the consumption of sodium hydroxide standard titration solution. Blank: at the same time, use 80 mL of pure water as a blank control, the consumption of sodium hydroxide (pH = 8.2) V 01 is the total acid blank consumption; the consumption after adding formaldehyde (pH = 9.2) V 02 is the amino acid nitrogen blank consumption.

[0082] Total acid calculation formula

[0083] (1)

[0084] In the formula: X is the total acid content in the sample, g / 100g;

[0085] V1 is the volume of sodium hydroxide standard solution (pH = 8.2) consumed by the titration solution, in mL;

[0086] V 01 The volume of sodium hydroxide standard solution (pH = 8.2) consumed in the blank titration test solution, in mL;

[0087] c represents the concentration of the sodium hydroxide standard solution, in mol / L;

[0088] 0.090 is the conversion factor for acids (calculated as lactic acid);

[0089] m is the sample mass, in grams.

[0090] Formula for amino acid nitrogen:

[0091] (2)

[0092] In the formula: X is the content of amino acid nitrogen in the sample, g / 100g;

[0093] V2 is the volume of sodium hydroxide standard solution (pH = 9.2) consumed by the titration solution, in mL;

[0094] V 02 The volume of NaOH standard solution consumed in the titration of the blank (after adding formaldehyde) test solution (pH = 9.2), mL;

[0095] c represents the concentration of the sodium hydroxide standard solution, in mol / L;

[0096] 0.014 is the mass of nitrogen, in g, equivalent to 1.00 mL of standard NaOH titration solution (c = 1.000 mol / L).

[0097] 7. Data Processing

[0098] Experimental results are expressed as mean ± standard deviation. SPSS statistical software was used to perform significance analysis and testing on the data, and GraphPad Prism 9.50 software was used for plotting.

[0099] II. Results and Analysis

[0100] 1. Single-factor experimental analysis

[0101] (1) Effects of salt solution pickling on the wild rice fields

[0102] In the pre-treatment of skipjack tuna, the osmotic pressure of high-concentration salt is used to remove sticky substances and blood from the fish meat, which facilitates the penetration of the subsequent smoking liquid. Figure 1As the volume fraction of the salt solution increases, the hardness, chewiness, adhesiveness, and resilience first increase and then decrease, reaching their optimal values ​​at 7% (w / v) and 9% (w / v) salt solutions. Table 3 shows that pickling with salt solutions of different volume fractions did not significantly change the moisture content of the arugula, the pH remained relatively stable, and the product brightness value (L) remained consistent. ), redness value (a ) and yellowness value (b There was no significant difference.

[0103] Depend on Figure 2 Sensory evaluation data showed that the sensory indicators were evenly distributed when the salt solution concentration was 7%, and there was no significant difference in the total sensory scores between 7% and 9% salt solutions. Therefore, considering production costs, a 7% (w / v) salt solution was chosen for subsequent experiments.

[0104] Table 3. Effects of salt solution pickling on the harvest season.

[0105]

[0106] (2) Effect of fumigation liquid addition on the wasteland

[0107] High-concentration smoke liquid should not be used directly on meat products. It needs to be diluted before use. Only at a suitable concentration can the aldehydes and phenols in the smoke liquid form a dry, glossy brownish-yellow film on the product surface, and cause the product to oxidize and dehydrate to prevent the subsequent growth of microorganisms and extend the shelf life of the product.

[0108] Depend on Figure 3 Texture analysis showed that the hardness, adhesiveness, and chewiness of products smoked with 2%, 6%, and 8% liquid smoke were better, significantly different from those smoked with 0% and 4%. Table 4 shows that the moisture content of the products with different amounts of smoked liquid addition did not change significantly and remained relatively stable. pH is an important factor affecting the quality of the raw materials, showing a fluctuating trend of first decreasing and then slowly increasing. The pH value was lowest at 6% liquid smoke, and the sensory score was highest at 6% liquid smoke. Figure 4 ).

[0109] In summary, the smoke flavor was mild when the amount of smoke liquid added was 0% and 2%, and the aroma and taste scores decreased when the amount added reached 8%. The 6% smoke liquid was more generally acceptable, therefore, 6% smoke liquid was chosen for the next stage of the experiment.

[0110] Table 4. Effects of different amounts of smoke liquid added on the quality of Arabushi

[0111]

[0112] (3) The effect of liquid fumigation time on the wild harvest

[0113] Analysis of variance showed that the liquid smoking time had a significant effect on hardness, chewiness, resilience, and pH (P < 0.05). Texture analysis ( Figure 5 The results showed that the hardness, adhesiveness, and chewiness were better after 30 min and 50 min of liquid smoking.

[0114] From Table 5, Figure 6 It was found that when the smoking time was 10 minutes, the smoking liquid did not fully penetrate the meat, resulting in a weak aroma and flavor. As the smoking time increased, the flavor gradually penetrated the meat. When the smoking time was 70 minutes or more, the aroma remained unchanged, but the meat became tough and the taste sour. This trend is consistent with the pH change, possibly because the smoking liquid gradually penetrated into the meat, altering the muscle's spatial structure and causing the water retained in the original space to be expelled, leading to tougher meat and a lower sensory score. Considering the changes in pH and other parameters, and given that a smoking time of 50 minutes yielded the highest sensory score, a smoking time of 50 minutes was chosen for the next stage of the experiment.

[0115] Table 5. Effect of liquid fumigation time on the quality of raw rice cakes

[0116]

[0117] (4) The effect of drying time on the dry season

[0118] Table 6 shows that as the drying time increases, the moisture content of the liquid-smoked ham pieces decreases from 45.65% to 24.25%. This is because continuous high-temperature heating denatures the myofibril protein in the meat, thereby reducing the binding force on water molecules, causing free water to continuously flow out and evaporate. Moreover, as the drying time increases, the hardness of the ham pieces gradually increases.

[0119] Color is an important factor affecting the quality of dried goods. As drying time increases, the brightness value (L) of the dried goods increases. ), redness value (a The significant change is likely due to the cross-linking reaction between carbonyl compounds in the smoking liquid and proteins in the meat products, causing a change in the color of the smoked meat. It can be seen that the color difference value L increases with increasing drying time. The color difference value a shows a decreasing trend. The increasing trend may be due to the fact that the longer the drying time, the more obvious the oxidation, the faster the Maillard reaction, and the more liquid stains accumulate on the surface.

[0120] Depend on Figure 7 Texture analysis results show that hardness, adhesiveness, and chewiness generally show an increasing trend, while resilience shows a horizontal trend. Figure 8 The results showed that the meat was too hard due to low moisture content, resulting in poor firmness and chewiness. Baking for 3.5 hours yielded the highest sensory score.

[0121] Based on the above, the products with moderate hardness, gumminess and chewiness were selected for the subsequent response surface experiment, so the baking time of 3.5 h was selected for the next experiment.

[0122] Table 6 Effect of drying time on the quality of section

[0123]

[0124] 2. Response surface experiment analysis

[0125] (1) Response surface experiment design results

[0126] Based on the single factor experiment, the salt solution 7% (w / v) was selected for the experiment. In the response surface design, three factors (A) smoke solution addition, (B) liquid smoke soaking time, (C) drying time were selected as indicators, and the sensory score, hardness, gumminess and chewiness of section products were selected as response values, so as to determine the optimal processing technology of liquid smoked section. The experimental factor level table is shown in Table 7.

[0127] Table 7 Response surface design and experimental results

[0128]

[0129] (2) Response surface results of sensory score

[0130] As shown in Table 8, the model P of sensory score (Y1) response value was less than 0.0001, the model fitting degree was high, and it had statistical significance. The lack of fit term P was greater than 0.05, which indicated that the experimental data and the model had good fitting degree and good repeatability, and could well reflect the experimental results, and the predicted value had high correlation with the experimental value (R 2 =0.9774). According to the F value of each factor, the order of factors affecting the sensory score of section was: A (smoke solution addition) > B (liquid smoke soaking time) > C (drying time).

[0131] The software Design-Expert 13.0 was used for multiple regression fitting analysis of the influence of three factors (A) smoke solution addition, (B) liquid smoke soaking time, (C) drying time on sensory score (Y1), and a quadratic polynomial model was established as follows:

[0132] Y1=38.8+1.75×A-0.875×B+0.375×C-0.75×AB+0.25×AC-0.5×BC-0.65×A 2 -4.4×B 2 -1.4×C 2 (R 2 =0.9774, R 2 Adj=0.9484).

[0133] Table 8. Variance of the Sensory Rating (Y1) Regression Model

[0134]

[0135] The 3D response surface regression model plot and contour plot were compared and analyzed to determine the optimal conditions for the amount of fumigation liquid added, the soaking time, and the drying time. The response surface plot and contour plot can intuitively reflect the magnitude of the interaction on the response value; the steeper the response surface plot, the greater the impact on the response value. The closer the contour plot is to an ellipse, the stronger the interaction between the two factors; the closer the contour plot is to a circle, the less significant the interaction between the two factors.

[0136] Depend on Figure 9 The response surface plot shows that option AB has the steepest slope and the greatest impact on sensory scores, meaning that the amount of smoke liquid added and the soaking time significantly affect sensory scores. The contour plot shows that the interaction between options AB and BC is stronger than that between option AC, consistent with the analysis of variance conclusions.

[0137] (3) Response surface results of texture

[0138] Tables 10 and 11 conclude that, using Design-Expert 13.0 software, with the amount of smoking liquid added (A), the smoking soaking time (B), and the drying time (C) as the three factors, and hardness (Y2), adhesiveness (Y3), and chewiness (Y4) as the response values, the P-values ​​of all models were less than 0.0001, and the P-values ​​of the lack-of-fit terms were all greater than 0.05 and not significant. This indicates that the experimental data and models have a high degree of fit and can well reflect the experimental results. In each regression model, factors A and B had P>0.05, indicating that factors A and B had no significant effect on the texture of the raw product; factor C had P<0.0001, indicating that drying time had a significant effect on the hardness, chewiness, and adhesiveness of the raw product. There were no interactions between terms AB, AC, and BC, indicating that C is an important model that significantly affects the product's hardness, adhesiveness, and chewiness. The effects of multiple regression fitting analysis on hardness (Y2), adhesiveness (Y3), and chewiness (Y4) were used to establish a quadratic polynomial model:

[0139] Y2=32891.5+341.21×A+10.84×B+6557.8×C+528.62×AB-562.9×AC+199×BC+273.64×A 2 -433.76×B 2 -189.19×C 2 (R) 2 = 0.9536, R 2 Adj=0.8938)

[0140] Y3=30656.4+581.08×A+128.64×B+6284.99×C+1181.85×AB-409.6×AC-138.68×BC-185.21×A 2 -979.69×B 2 +90.61×C 2 (R) 2 = 0.9513, R 2 Adj =0.8886)

[0141] Y4=35825.38-1176.38×A+61.77×B+5172.78×C+610.48×AB+276.93×AC-56.17×BC-2081.95×A 2 -117.15×B 2 -1458.15×C 2 (R) 2 = 0.9405, R 2 Adj =0.8639)

[0142] Table 9. Variance of the Hardness (Y2) Regression Model

[0143]

[0144] Table 10. Variance of the Adhesion (Y3) Regression Model

[0145]

[0146] Table 11 Variance of the Chewing (Y4) Regression Model

[0147]

[0148] Depend on Figures 10-12 Response surface methodology revealed that drying time (C) had a highly significant effect on textural properties (P < 0.0001), while the amount of smoke liquor added (A) and the smoking time (B) had no significant effect (P > 0.05). The interaction terms AB, AC, and BC had no effect on hardness, chewiness, or adhesiveness. Only changes in drying time affected the textural properties of the raw product. As the drying time increased from 3 h to 4 h, hardness (Y2), adhesiveness (Y3), and chewiness (Y4) increased by approximately 40.2%, 49.8%, and 42.1%, respectively (Table 7).

[0149] (4) Optimal process and verification test

[0150] The optimal process was obtained by calculating the regression equation using Design Expert 13 software: with a smoke liquid addition of 6.66%, a smoke soaking time of 48.02 min, and a drying time of 3.40 h (for convenience, in the verification experiment, the smoke liquid addition was 6.7% and the smoke soaking time was 48 min), the predicted sensory score was 39.42 points, and the hardness was 3.4 × 10⁻⁶. 3 g, adhesiveness 3.19×10 4 g, chewing capacity 3.61×10 4 g.

[0151] Using mathematical modeling, the model conditions were derived, and three parallel experiments were conducted. The sensory score of the product was 38 points, with a hardness of 36592.91 g, adhesiveness of 32510.2 g, and chewiness of 377412.56 g. These measured data were not significantly different from the predicted model, indicating that the model can effectively predict the sensory score and textural characteristics of liquid-smoked bonito flakes.

[0152] (5) Optimal fermentation process

[0153] The increasing pH trend during the 0-28 day fermentation process can be attributed to the effect of alkaline metabolites produced by fungal fermentation on the surface. Figure 13 A). After 28 days, the pH of the 1% group showed a decreasing trend, which was attributed to the decomposition of glycogen, ATP, and creatine phosphate in the skipjack tuna muscle after fermentation. With prolonged fermentation time, the moisture content of all three groups of products gradually decreased, stabilizing at around 13%. Figure 13 B) The moisture content of commercially available Krabushi products is 11.37%, which is not significantly different.

[0154] As fermentation progressed, the TVB-N content in the three groups of samples ranged from 51.35 to 267.10 mg / 100g. Figure 13 C). The threshold for TVB-N concentration: The U.S. Food and Drug Administration requires that the TVB-N concentration in salted or dried fish products be between 100 and 200 mg / 100g. Higher TVBN values ​​than other seafood products are due to the influence of specific putrefactive bacteria and endogenous enzymes during smoking and fermentation. The TBARS value shows an "increase-decrease-increase" trend. Figure 13 D). As fermentation progresses, oxygen is gradually consumed, leading to a decrease in oxygen content. This inhibits lipid oxidation, resulting in a decrease in TBARS values. With increasing mold fermentation time, the contents of AA-N and TA increase significantly. Figure 13 E, Figure 13F), indicating that the protein in the fermentation sample is continuously hydrolyzed during the fermentation process, and the content of organic acid gradually increases. However, during 28d-35d, the TA and AA-N of 1% fermentation product decrease, indicating that the acid-producing microbial activity of the product decreases, and the fermentation has terminated. The TA and AA-N of 0.5% fermentation product are still rising, indicating that the product is still in the fermentation process and is in good condition. Considering the above factors, the product is best when the inoculation amount is 0.5% and the fermentation time is 28d.

[0155] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a fermented liquid of Aspergillus oryzae smoked horse mackerel fin, characterized by, It comprises the following steps: (1) steaming the pretreated bonito pieces, draining and drying, then soaking in smoke liquid, draining and drying to obtain liquid smoked bonito pieces; (2) inoculating the liquid smoked bonito pieces with Aspergillus oryzae spore suspension for fermentation to obtain Aspergillus oryzae fermented liquid smoked bonito pieces.

2. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 1, characterized in that, The specific process of step (1) is as follows: steaming the bonito pieces at 100-105℃ for 30 min, draining the steamed material, removing fish bones and skin after cooling to obtain bonito meat; immersing the bonito meat in smoke liquid with an additive amount of 4-8%, cold storage and sealed immersion at 4℃ for 30-50 min, then draining on a sieve after immersion, and drying in an oven at 120℃ for 3-4 h to obtain liquid smoked bonito pieces.

3. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 1, characterized in that, In step (1), the smoke liquid is hickory smoke liquid.

4. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 1, characterized in that, In step (1), the pretreatment process of the bonito pieces is as follows: thawing the bonito, removing the head, internal organs and fins, washing to remove blood and mucus, washing the abdominal and dorsal muscle tissues with tap water, and cutting into pieces with a size of 6 cm×4 cm×2 cm to obtain bonito pieces, then immersing the bonito pieces in a 5-11% volume fraction of salt solution at 4℃ for 15 min, and then rinsing the surface with running water to remove residual salt water and blood water to obtain pretreated bonito pieces.

5. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 1, characterized in that, The specific process of the step (2) is: uniformly smear the Aspergillus oryzae spore suspension with a concentration of 10 8 spores / ml on the surface of the liquid smoked section at an inoculation amount of 0.5-1%, and place it in a constant temperature and humidity incubator at 30°C and a relative humidity of 75% for fermentation for 28 days. Take samples on the 0th day, 14th day, 21st day, 28th day, and 35th day of fermentation for intervention operation to obtain the Aspergillus oryzae fermented liquid smoked tuna section.

6. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 5, characterized by, The specific process of the intervention operation is as follows: on the 0th day, 14th day, 21st day and 28th day of fermentation, taking out the liquid smoked bonito pieces and drying in a 100℃ oven for 15 min, removing the dense mold mycelium on the surface after cooling, and for samples that still need to continue fermentation after the intervention operation, re-inoculating the samples with the Aspergillus oryzae spore suspension and returning them to the incubator for continued fermentation until the fermentation cycle is completed.

7. The process for preparing smoked horse mackerel fillets in fermented broth of Aspergillus oryzae according to claim 5, characterized by, The concentration is 10 8 The preparation process of the Aspergillus oryzae spore suspension with a concentration of 10 spore / ml is as follows: Aspergillus oryzae is subcultured in malt extract medium and cultured at 30°C for 7 days to obtain an Aspergillus oryzae liquid; the Aspergillus oryzae liquid is uniformly coated on a PDA plate, which is cultured at 30°C for 4-7 days until yellow-green spores are grown; 2 mL of 0.9% NaCl solution is added to the PDA plate, spores are scraped using a sterilized and cooled inoculation shovel, residual spores are washed with 1 mL of normal saline, transferred to a centrifuge tube, and diluted with normal saline to 10 mL; vortexed, centrifuged at 5000 r / min for 5 min, the supernatant is discarded, and a spore precipitate is obtained; then 30 mL of 0.9% NaCl solution is added for resuspension and washing, the supernatant is discarded after centrifugation; 5 mL of normal saline is added and vortexed to obtain a spore suspension, which is diluted with 0.9% NaCl solution to obtain an Aspergillus oryzae spore suspension with a concentration of 10 8 spore / ml. The Aspergillus oryzae strain is purchased from China Industrial Microbial Culture Collection Center, with a strain number of CICC 2339 and a classification name of Aspergillus oryzae.

8. The process for preparing smoked horse mackerel fillets in a liquid fermented medium of Aspergillus oryzae according to claim 1, characterized by, It further comprises step (3) of vacuum preserving the Aspergillus oryzae fermented liquid smoked bonito pieces at room temperature.

9. A fermented liquid of Aspergillus oryzae smoked bonito flakes, characterized by, The Aspergillus oryzae fermented liquid smoked bonito pieces prepared by the method of any one of claims 1-8 have a moisture mass percentage of 13%, a volatile basic nitrogen content of 200 mg / 100 g, and a hardness of 36592 g.

10. The Aspergillus oryzae fermented liquid smoked bonito pieces of claim 9 for use in bonito food.

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