Method for preparing smoked dried star eels based on composite vegetable juice emulsion fermentation

Abstract

The invention relates to the technical field of food, and discloses a method for preparing smoked dried star eel based on composite vegetable juice emulsion fermentation, which comprises the following steps: mashing Chinese cabbage and seaweed, mixing the mashed Chinese cabbage and seaweed with star eel head oil, and emulsifying to obtain the composite vegetable juice emulsion; immersing the star eel in the composite vegetable juice emulsion, and carrying out anaerobic fermentation to obtain a fermented fish body; and pickling, drying and smoking the fermented eel body to obtain the smoked dried star eel. By adopting the method disclosed by the invention, negative effects caused by long-time smoking can be reduced, so that after being smoked for a long time, the star eel meat still can keep delicious taste and pure fish flavor, is compact and chewy, does not have hard or astringent conditions, also has the characteristic of strong sweet potato flavor, is moderate in smoked flavor, and is free from any side effects. The sour taste, the astringent taste and the earthy taste are light.

Description

Technical Field

[0001] The invention relates to the technical field of food, and in particular to a method for preparing smoked dried conger eel based on composite vegetable juice emulsion fermentation. Background Art

[0002] The common conger eel products on the market are relatively single, which is mainly due to the limitations of conger eel processing technology and market demand. Although conger eels are tender, fat-rich and have high economic value, the conger eel products on the market are still mainly grilled eels, grilled eels and salted eels, lacking diversified choices.

[0003] The traditional process of making smoked fish includes descaling, removing the internal organs, washing, and cutting the fresh fish, and removing the black film in the belly of the fish; then adding appropriate seasonings and spices according to taste preferences, stirring evenly and marinating for a period of time; then drying to remove some of the moisture in the fish meat, and then placing the dried fish on top of the smoking pot and smoking it over medium and low heat for a period of time. Applying this traditional process to conger eels will give conger eel products new vitality and meet consumers' demand for diversified and personalized food.

[0004] However, the characteristic of conger eel meat is its relatively high fat content, and the fat distribution pattern is unique. Unlike most fish, the fat is not mainly accumulated under the skin, but delicately penetrates into every fiber of the fish meat. This unique fat distribution characteristic puts forward special requirements for the development of smoked conger eel products: in order to avoid the sensory quality of the product being reduced due to fat oxidation during the subsequent storage period, a relatively longer smoking time must be adopted. However, the long smoking process often causes the conger eel meat to be overly dry and hardened, and the smoked flavor becomes extremely strong, which masks the unique freshness of the conger eel meat itself, making the final product homogenized with many fish products that have been smoked for a long time, and losing the unique flavor that conger eels should have. Therefore, finding a balance between the shelf life and flavor retention of smoked conger eel products has become a task that tests both technology and creativity. Summary of the invention

[0005] In order to solve the technical problem that the meat of conger eels becomes too dry and hardened after long-term smoking, and the smoked flavor becomes abnormally strong, which covers up the unique deliciousness of the conger eel meat itself, the present invention provides a method for preparing smoked dried conger eels based on compound vegetable juice emulsion fermentation. The method of the present invention can make the conger eel meat still maintain its own delicious taste after long-term smoking, and the meat is firm and chewy, and at the same time has the characteristics of strong potato aroma, moderate smoked flavor, and light sour taste, astringency and earthy taste.

[0006] The specific technical scheme of the present invention is: A method for preparing smoked dried conger eel based on composite vegetable juice emulsion fermentation, comprising the following steps: S1: Pulping the Chinese cabbage and Nostoc mollissima, mixing with the conger eel head oil, and emulsifying to obtain a composite vegetable juice emulsion; S2: immersing the conger eel in the composite vegetable juice emulsion for anaerobic fermentation to obtain a fermented fish body; S3: salting, drying and smoking the fermented fish body to obtain smoked dried conger eel.

[0007] In the present invention, the composite vegetable juice can be formed into an emulsion by utilizing the conger eel head oil and emulsification operation. For the conger eel meat with rich texture, the emulsion form helps the composite vegetable juice to better penetrate into the gaps, and further enhances the adhesion and stability, which is beneficial to the subsequent anaerobic fermentation process, using the microorganisms and enzymes in the cabbage and the sea moss for fermentation, so that a series of complex biochemical changes occur in the conger eel meat, including the acidification of the microorganisms and enzymes, the gelation of collagen fibers and sarcoplasmic proteins, and the degradation of proteins and lipids. Through the above-mentioned effects, the conger eel meat can be prevented from being excessively dry and hardened during the long-term smoking process, and the problems of too strong smoky taste, sour taste, astringency and earthy taste can be avoided, so that the conger eel meat after long-term smoking can still maintain its own delicious taste and pure fish flavor, and the meat is firm and chewy, and has more prominent fermented taste, caramel taste, floral fragrance and sweetness, showing the characteristics of "potato fragrance" as a whole.

[0008] In the above process, the selection of vegetables and oils used in the composite vegetable juice emulsion has an important influence. The present invention uses Chinese cabbage, sea moss and conger eel head oil to cooperate with each other, which can improve the fermentation effect and better reduce the negative effects of long-term smoking (including excessive drying and hardening of the meat, and the production of too strong smoky, sour, astringent and earthy taste), so that the smoked dried conger eel finally prepared has a better flavor. Specifically: (1) The synergistic effect of Chinese cabbage and Nostoc: The combination of lactic acid bacteria in Chinese cabbage and oligosaccharides in Nostoc can not be replaced by other vegetables in the fermentation process of conger eels. There is a complex interaction mechanism between them. This interaction mechanism is not only reflected in the utilization and metabolism of oligosaccharides by lactic acid bacteria, but also in the regulation of oligosaccharides on the growth and metabolism of lactic acid bacteria.

[0009] On the one hand, the lactic acid bacteria in Chinese cabbage have a unique metabolic regulation mechanism and flavor generation ability, which can make full use of the oligosaccharides in Nostoc as a carbon source and energy source, and produce organic acids such as lactic acid, acetic acid, propionic acid, and ethanol, aldehydes, ketones, and esters by intensifying metabolic pathways such as glycolysis, citric acid cycle, and pentose phosphate pathway. These flavor substances and functional ingredients not only give smoked dried conger eel a unique taste and aroma, but also improve its nutritional value and health benefits.

[0010] On the other hand, the oligosaccharides in Nostoc have special microbial regulation and metabolic activation effects. In addition to promoting the growth and reproduction of beneficial microorganisms in cabbage lactic acid bacteria, the specific biological recognition ability produced by the sulfate and phosphate groups in its structure is very outstanding in activating the metabolic activity of cabbage lactic acid bacteria, which helps to further improve the fermentation efficiency and quality.

[0011] The above interaction mechanism enables the lactic acid bacteria in Chinese cabbage and the oligosaccharides in Nostoc to form a complex and stable ecosystem during the fermentation of conger eels. In this ecosystem, the lactic acid bacteria in Chinese cabbage and the unique oligosaccharides in Nostoc to form a complex and stable ecosystem during the fermentation of conger eels. In this ecosystem, the lactic acid bacteria in Chinese cabbage and the unique oligosaccharides in Nostoc to form a complex and stable ecosystem during the fermentation of conger eels. They work together to produce a unique fermentation effect and flavor characteristics, thereby reducing the negative effects of long-term smoking and improving the flavor of smoked dried conger eels.

[0012] (2) Effects of conger eel head oil: Conger eel head oil has a relatively high content of polyunsaturated fatty acids and phospholipids. According to preliminary measurements, the conger eel head oil used in the present invention has a polyunsaturated fatty acid (PUFA) / saturated fatty acid (SFA) ratio of 5.38, and a phospholipid content of 8.15 g / 100 g of conger eel head oil. These polyunsaturated fatty acids and phospholipids can play the following roles: under the treatment of high-pressure microfluidization technology, the polyunsaturated fatty acids and phospholipids in the conger eel head oil are well released, and more efficiently mixed and dispersed with the components in the vegetable juice. This process effectively reduces the tension of the oil-water interface and forms smaller emulsion droplets with better stability by intensifying the hydrophobic interaction and the formation of hydrogen bonds; secondly, the polyunsaturated fatty acids and phospholipids in the conger eel head oil can affect the composition and fluidity of the microbial cell membrane and act as signal molecules to induce the metabolic pathways and product generation of specific microorganisms during the fermentation process, thereby enriching the flavor level of the fermented product; in addition, compared with other oils, the high content of polyunsaturated fatty acids and phospholipids in the conger eel head oil can better serve as a regulatory factor for enzymes in conger eel meat, and has a more significant effect in promoting the decomposition of fat and protein in fish meat and increasing the content of alcohol, aldehyde and organic acid substances in conger eel meat. Through the above effects, the preparation of composite vegetable juice emulsion using conger eel head oil can reduce the negative effects of long-term smoking, so that the smoked dried conger eel obtained in the end has a better flavor.

[0013] Preferably, in step S1, the mass ratio of the Chinese cabbage to the Nostoc laminaria is 4-6:1.

[0014] The cabbage and the sea moss are compounded in a specific mass ratio (4-6:1), which can make the lactic acid bacteria in the cabbage and the oligosaccharides in the sea moss better play their synergistic role, thereby effectively reducing the negative impact of long-term smoking and giving the smoked dried conger eel a better flavor.

[0015] Preferably, in step S1, the mass of the conger eel head oil is 10-14wt% of the mass of the pulped Chinese cabbage and Nostoc laminaria; the emulsification is performed by high-pressure micro-jetting, the micro-jet pressure is 25000-35000psi, and the number of treatments is 6-10 times.

[0016] By increasing the microjet intensity (including pressure and number of treatments), the seaweed polysaccharide in the composite vegetable juice emulsion can be degraded, thereby reducing the emulsion particle size; in addition to the microjet intensity, the amount of conger eel head oil also affects the particle size of the composite vegetable juice emulsion, and by increasing the amount of conger eel meat oil, the particle size of the composite vegetable juice emulsion can be reduced. The reduction in the particle size of the composite vegetable juice emulsion is conducive to its better penetration into the conger eel meat, and further enhances the adhesion and stability, thereby reducing the negative impact of long-term smoking to a greater extent, improving the subsequent fermentation efficiency, and making the smoked dried conger eel finally prepared have a better flavor.

[0017] Preferably, in step S2, the temperature of the anaerobic fermentation is 25-28° C., and the time is 36-48 hours; and the mass ratio of the conger eel to the composite vegetable juice emulsion is 1:3-4.

[0018] Preferably, in step S1, the preparation step of the conger eel head oil comprises: cutting the conger eel head into pieces, placing the pieces in water, enzymolyzing the pieces with papain, and centrifuging the upper layer to obtain the conger eel head oil; the mass of the papain is 0.6-1.0% of the mass of the conger eel head; the enzymatic activity of the papain is 60,000-100,000 U / g; the enzymolysis temperature is 50-55°C, and the time is 2-4h.

[0019] Furthermore, before the conger eel head is cut into pieces, the conger eel is dried to remove surface moisture.

[0020] Preferably, in step S2, before immersing the conger eel in the composite vegetable juice emulsion, the conger eel is pretreated, the steps comprising: removing the head and internal organs of the conger eel, and then washing it.

[0021] Preferably, in step S3, the smoking temperature is 58-62° C. and the smoking time is 30-40 min.

[0022] Preferably, in step S3, during the smoking process, the smoking wood used is one or more of oak, apple wood, alder and agarwood.

[0023] Furthermore, in step S3, during the smoking process, the smoking wood used includes, by weight, 60 to 65 parts of oak, 20 to 25 parts of apple wood, 10 to 15 parts of alder, and 5 to 10 parts of agarwood.

[0024] Preferably, in step S3, the pickling step comprises: applying salt on the surface and inside of the fermented fish body, the amount of salt used is 80-90g / 500g of the fermented fish body mass, and pickling at 25-28°C for 23-25h.

[0025] Preferably, in step S3, the drying step comprises: wiping off the salt particles and excess water on the surface of the pickled fish body, and baking at 50-60° C. for 28-30 hours.

[0026] Compared with the prior art, the present invention has the following advantages: (1) The method of the present invention can reduce the negative effects of long-term smoking, so that the conger eel meat can still maintain its own delicious taste and pure fish flavor after long-term smoking, and the meat is firm and chewy, not hard or astringent, and has the characteristics of strong potato flavor, moderate smoky flavor, and light sour taste, astringency and earthy taste.

[0027] (2) The method of the present invention can make the smoked dried conger eel reddish brown, evenly distributed, without variegated colors or spots, with good surface gloss, bright and textured. At the same time, the regular shape of the conger eel pieces can be better maintained to avoid damage or breakage. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The characteristic odor evaluation results of smoked dried conger eel samples 4 to 6. Note: Since it is impossible to distinguish different samples in the non-colored picture, Figure 1 Color images were used.

[0029] Figure 2 The effect of the amount of conger eel head oil added on the particle size of composite vegetable juice emulsion.

[0030] Figure 3 Effect of microfluidization pressure on particle size of composite vegetable juice emulsion.

[0031] Figure 4 The effect of microfluidization treatment times on the particle size of composite vegetable juice emulsion.

[0032] Figure 5 The flavor fingerprints of conger eel meat samples 1 to 3. Note: Since the red signal cannot be distinguished in the non-colored image, Figure 5 Color images were used.

[0033] Figure 6 The microbial diversity of conger eel meat samples 1 to 3. Note: Since different bacterial genera cannot be distinguished in the non-colored image, Figure 6 Color images were used.

[0034] Figure 7 The organic acid content in conger eel meat at different fermentation times. Note: Since different organic acids cannot be distinguished in the non-colored graph, Figure 7 Color images were used.

[0035] Figure 8 The gel strength of conger eel meat changes with different fermentation times.

[0036] Fig. 9 The sensory evaluation results of smoked dried conger eel samples 4 to 6 are shown below. Note: Since the samples cannot be distinguished in the non-colored images, Fig. 9 Color images were used.

[0037] Fig.10 The sensory evaluation results of smoked dried conger eel samples 6 and 7 to 9 are shown in Figure 1. Fig.10 Color images were used.

[0038] Fig.11The characteristic odor evaluation results of smoked dried conger eel samples 6 and 7 to 9 are shown in the figure. Note: Since it is impossible to distinguish different samples in the non-colored figure, Fig.11 Color images were used.

[0039] Fig.12 The sensory evaluation results of smoked dried conger eel samples 6 and 10-12 are shown in Figure 1. Note: Since different samples cannot be distinguished in the non-colored image, Fig.12 Color images were used.

[0040] Fig.13 The characteristic odor evaluation results of smoked dried conger eel samples 6 and 10-12 are shown in the figure. Note: Since it is impossible to distinguish different samples in the non-colored figure, Fig.13 Color images were used.

[0041] Fig.14 The sensory evaluation results of smoked dried conger eel samples 6 and 13 are shown in the figure. Fig.14 Color images were used.

[0042] Fig.15 The characteristic odor evaluation results of smoked dried conger eel samples 6 and 13. Note: Since different samples cannot be distinguished in the non-colored figure, Fig.15 Color images were used. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the embodiments.

[0044] Overall embodiment A method for preparing smoked dried conger eel based on composite vegetable juice emulsion fermentation, comprising the following steps: S1: Pulping the Chinese cabbage and Nostoc mollissima, mixing with the conger eel head oil, and emulsifying to obtain a composite vegetable juice emulsion; S2: immersing the conger eel in the composite vegetable juice emulsion for anaerobic fermentation to obtain a fermented fish body; S3: salting, drying and smoking the fermented fish body to obtain smoked dried conger eel.

[0045] As a specific implementation, in step S1, the preparation step of the conger eel head oil comprises: cutting the conger eel head into pieces, placing it in water, enzymolyzing it with papain, centrifuging and taking the upper layer to obtain the conger eel head oil; the mass of the papain is 0.6-1.0% of the mass of the conger eel head; the enzymatic activity of the papain is 60000-100000 U / g; the enzymolysis temperature is 50-55°C, and the time is 2-4 hours. Optionally or preferably, before cutting the conger eel head into pieces, the conger eel is dried to remove surface moisture.

[0046] As a specific implementation, in step S1, the mass ratio of the Chinese cabbage to the Nostoc laminaria is 4-6:1.

[0047] As a specific implementation, in step S1, the mass of the conger eel head oil is 10-14wt% of the mass of the pulped Chinese cabbage and sea moss; the emulsification is performed by high-pressure micro-jetting, the micro-jet pressure is 25000-35000psi, and the number of treatments is 6-10 times.

[0048] As a specific implementation, in step S2, before immersing the conger eel in the composite vegetable juice emulsion, the conger eel is pre-treated, and the steps include: removing the head and internal organs of the conger eel, and then washing it.

[0049] As a specific implementation, in step S2, the temperature of the anaerobic fermentation is 25-28°C, and the time is 36-48 hours; the mass ratio of the conger eel to the composite vegetable juice emulsion is 1:3-4.

[0050] As a specific implementation, in step S3, the pickling step includes: applying salt on the surface and inside of the fermented fish body, the amount of salt used is 80-90g / 500g of the fermented fish body mass, and pickling at 25-28°C for 23-25h.

[0051] As a specific implementation, in step S3, the drying step includes: wiping off the salt particles and excess water on the surface of the pickled fish body, and baking at 50-60° C. for 28-30 hours.

[0052] As a specific implementation, in step S3, during the smoking process, the smoking wood used is one or more of oak, apple, alder and agarwood; the smoking temperature is 58-62°C, and the time is 30-40 minutes. Optionally or preferably, the smoking wood used includes, by weight, 60-65 parts of oak, 20-25 parts of apple, 10-15 parts of alder, and 5-10 parts of agarwood. Specific embodiments The present invention is described below by specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Without departing from the spirit and scope of the inventive concept, changes and advantages that can be thought of by those skilled in the art are included in the present invention, and the attached claims and any equivalents thereof are the protection scope of the present invention.

[0054] In the following examples and comparative examples, in order to facilitate horizontal comparison to demonstrate the technical effect of the present invention, the mass of the selected conger eels is 1500-2000 g. However, the protection scope of the present invention is not limited thereto.

[0055] Example 1: Preparation of smoked dried conger eel Prepare smoked dried conger eel by following the steps below: S1: Pretreatment of conger eels and extraction of conger eel head oil Use a sharp knife to quickly cut below the head of the conger eel, making sure to cut through the spine in one stroke, and then immediately remove the head to maintain the integrity of the fish and quickly drain the blood. After slaughtering, remove the viscera, cut open the belly of the fish and remove all the internal organs. Thoroughly wash the inside and outside of the fish to remove any remaining blood, mucus and any impurities to obtain the pre-processed conger eel.

[0056] The cleaned eel head was dried in an oven at 50°C for 20 min until the surface moisture was removed, and then cut into small pieces of about 1 cm×1 cm×1 cm. Purified water was added at a solid-liquid ratio of 1:4, and 0.6% of papain (enzyme activity 100,000 U / g) of the mass of the conger eel head was added for enzymolysis. The enzymolysis temperature was 55°C and the enzymolysis time was 4 h. The obtained enzymolysis solution was centrifuged at 8000 rpm and the upper layer was taken to obtain conger eel head oil.

[0057] S2: Preparation of composite vegetable juice emulsion The cabbage and the sea moss were added into a wall breaking machine at a mass ratio of 4:1, and the pulping was performed at 30000 rpm to obtain a slurry. The conger eel head oil was added into the slurry at an addition amount of 10wt% (i.e., the mass of the conger eel head oil was 10wt% of the mass of the slurry), mixed evenly, and treated with a high-pressure microjet at a microjet pressure of 25000psi for 8 times to obtain a composite vegetable juice emulsion.

[0058] S3: Wet fermentation The pretreated conger eel and the composite vegetable juice emulsion were placed in an anaerobic fermentation tank at a mass ratio of 1:4, ensuring that the composite vegetable juice emulsion completely submerged the conger eel, and fermented under anaerobic conditions for 36 hours at a fermentation temperature of 25° C. to obtain a fermented fish body.

[0059] S4: Cured, dried and smoked Sprinkle an appropriate amount of salt evenly on the fermented fish body, the amount of salt used is 80g / 500g of the fermented fish body mass. Gently knead to evenly distribute the salt on the surface and inside of the fish body, marinate at 25°C for 23 hours until a small amount of water is precipitated on the surface of the conger eel. Take out the marinated conger eel, wipe off the salt particles and excess water on the surface, and dry it in a 50°C oven for 28 hours until the surface of the conger eel becomes dry and slightly elastic. Put the dried conger eel into a smoking furnace for smoking treatment, the smoking temperature is 58°C, the smoking time is 40 minutes, and the smoking wood used is composed of the following 4 types of wood by mass percentage: 60% oak, 20% apple wood, 10% alder, and 10% agarwood. After the smoking treatment is completed, smoked dried conger eel is obtained.

[0060] Embodiment 2~5: preparation of smoked dried conger eel In Examples 2 to 5, smoked dried conger eels were prepared according to the steps of Example 1, and the only difference from Example 1 was that in Examples 2 to 5, the amount of conger eel head oil added in step S2 was changed from 10 wt % to 6, 8, 12 and 14 wt % respectively. The remaining steps were the same as in Example 1.

[0061] Examples 6-9: Preparation of smoked dried conger eel In Examples 6 to 9, smoked dried conger eels were prepared according to the steps of Example 1, and the only difference from Example 1 was that in Examples 6 to 9, the microjet pressure in step S2 was changed from 25,000 psi to 15,000, 20,000, 30,000, and 35,000 psi, respectively. The remaining steps were the same as in Example 1.

[0062] Examples 10-13: Preparation of smoked dried conger eel In Examples 10 to 13, smoked dried conger eels were prepared according to the steps of Example 1, and the only difference from Example 1 was that in Examples 10 to 13, the number of microfluidization treatments in step S2 was changed from 8 to 2, 4, 6, and 10, respectively. The remaining steps were the same as in Example 1.

[0063] Test Example 1: Effect of the amount of conger eel head oil added, microjet pressure and microjet number The particle sizes of the composite vegetable juice emulsions prepared in Examples 1 to 13 were measured using a zetasizer laser particle size analyzer. The results are shown in Figures 2 to 4 .

[0064] from Figures 2 to 4 It can be seen that the particle size of the composite vegetable juice emulsion decreases with the increase of the amount of conger eel head oil added; when the amount of conger eel head oil added is 10-14wt%, the particle size of the composite vegetable juice emulsion reaches the minimum and there is no significant difference. With the increase of microjet pressure, the particle size of the composite vegetable juice emulsion also shows a trend of gradually decreasing, reaching the minimum at 25000-35000psi and the difference is not significant. With the increase of the number of microjet treatments, the particle size of the composite vegetable juice emulsion also gradually decreases, reaching the minimum at 6-10 microjet times and there is no significant difference. The increase in microjet intensity (pressure and number) causes the composite vegetable juice emulsion to tend towards a finer structure, which may be related to the degradation of seaweed polysaccharides therein. Since a smaller particle size helps the composite vegetable juice emulsion to better penetrate into the pores of the conger eel meat and further enhance the adhesion and stability to improve the fermentation efficiency, the preferred amount of conger eel head oil added in the present invention is 10 to 14 wt %, the microjet pressure is 25,000 to 35,000 psi, and the number of microjet treatments is 6 to 10 times.

[0065] Comparative Example 1: Preparation of smoked dried conger eel The difference between this comparative example and Example 12 is that the conger eel is not subjected to wet fermentation in this comparative example. Specifically, the steps for preparing smoked dried conger eel in this comparative example are as follows: S1: Pretreatment of conger eels and extraction of conger eel head oil Use a sharp knife to quickly cut below the head of the conger eel, making sure to cut through the spine in one stroke, and then immediately remove the head to maintain the integrity of the fish and quickly drain the blood. After slaughtering, remove the viscera, cut open the belly of the fish and remove all the internal organs. Thoroughly wash the inside and outside of the fish to remove any remaining blood, mucus and any impurities to obtain the pre-processed conger eel.

[0066] S2: Cured, dried and smoked Sprinkle an appropriate amount of salt evenly on the pretreated conger eel, the amount of salt used is 80g / 500g of the pretreated conger eel mass. Gently knead to evenly distribute the salt on the surface and inside of the fish body, marinate at 25°C for 23 hours until a small amount of water is precipitated on the surface of the conger eel body. Take out the marinated conger eel, wipe off the salt particles and excess water on the surface, and place it in a 50°C oven to dry for 28 hours until the surface of the conger eel body becomes dry and slightly elastic. Put the dried conger eel into a smoking furnace for smoking treatment, the smoking temperature is 58°C, the smoking time is 40min, and the smoking wood used is composed of the following 4 types of wood by mass percentage: 60% oak, 20% apple wood, 10% alder, and 10% agarwood. After the smoking treatment is completed, smoked dried conger eel is obtained.

[0067] Comparative Example 2: Preparation of smoked dried conger eel The difference between this comparative example and Example 12 is that in this comparative example, after the Chinese cabbage and Nostoc laminaria were pulped, the conger eel head oil was not added to the obtained pulp and high-pressure micro-jetting was not performed. Specifically, the steps for preparing smoked dried conger eel in this comparative example are as follows: S1: Pretreatment of conger eels and extraction of conger eel head oil Use a sharp knife to quickly cut below the head of the conger eel, making sure to cut through the spine in one stroke, and then immediately remove the head to maintain the integrity of the fish and quickly drain the blood. After slaughtering, remove the viscera, cut open the belly of the fish and remove all the internal organs. Thoroughly wash the inside and outside of the fish to remove any remaining blood, mucus and any impurities to obtain the pre-processed conger eel.

[0068] S2: Preparation of compound vegetable juice The cabbage and the seaweed were added into a wall breaking machine at a mass ratio of 4:1, and the mixture was blended at 30000 rpm to obtain a composite vegetable juice.

[0069] S3: Wet fermentation The pretreated conger eel and the compound vegetable juice were placed in an anaerobic fermentation tank at a mass ratio of 1:4, ensuring that the compound vegetable juice completely submerged the conger eel, and fermented under anaerobic conditions for 36 hours at a fermentation temperature of 25°C to obtain a fermented fish body.

[0070] S4: Cured, dried and smoked Sprinkle an appropriate amount of salt evenly on the fermented fish body, the amount of salt used is 80g / 500g of the fermented fish body mass. Gently knead to evenly distribute the salt on the surface and inside of the fish body, marinate at 25°C for 23 hours until a small amount of water is precipitated on the surface of the conger eel. Take out the marinated conger eel, wipe off the salt particles and excess water on the surface, and dry it in a 50°C oven for 28 hours until the surface of the conger eel becomes dry and slightly elastic. Put the dried conger eel into a smoking furnace for smoking treatment, the smoking temperature is 58°C, the smoking time is 40 minutes, and the smoking wood used is composed of the following 4 types of wood by mass percentage: 60% oak, 20% apple wood, 10% alder, and 10% agarwood. After the smoking treatment is completed, smoked dried conger eel is obtained.

[0071] Test Example 2: Effect of wet fermentation of composite vegetable juice emulsion 2.1 Effects on volatile flavor components The volatile flavor components of the samples were analyzed by gas chromatography-ion mobility spectrometry (GC-IMS), and the specific process was as follows: 2 g of conger eel meat before pickling in Comparative Example 1, Comparative Example 2 and Example 12 (respectively recorded as "sample 1", "sample 2" and "sample 3") were taken and placed in a 20 mL headspace injection bottle, and enriched and balanced at a temperature of 50° C. and an oscillation frequency of 250 rpm for 20 min. 500 μL of the headspace was drawn from the injection needle and injected into the injection port. The volatile components were separated by a polar chromatographic column MXT-WAX (15 m×0.53 mm×1 μm) and then injected into the IMS. The carrier gas (high-purity N2) E1 flow rate was 150 mL / min, and the E2 flow rates were 2, 2, 10, 50, 100 and 150 mL / min at 0, 2, 10, 20, 25 and 30 min, respectively. LAV (Version 2.21) workstation was used to identify, organize data and draw pictures. The fingerprints obtained are shown in Figure 5 .

[0072] In the flavor fingerprint, the redder the signal color, the higher the substance content. Figure 5 It can be seen that: (1) Compared with the unfermented sample (sample 1), higher levels of volatile alcohols, aldehydes and ketones were detected in the conger eel meat after wet fermentation with composite vegetable juice (sample 2) and wet fermentation with composite vegetable juice emulsion (sample 3). Among them, the volatile alcohols with higher levels include 1-pentanol, 1-hexanol, 3-octanol, 2-propanol, 1-propanol, 1-butanol and 1-octen-3-ol. These volatile alcohols are mainly produced as products of fat oxidation and derivatives of the Maillard reaction, which can give unique floral, fruity and sweet aromas. The aldehyde and ketone components with higher content include cyclohexanone, butanal, 2-octanone, 2-heptanone, heptanal and 2-octenal ((E)-2-octenal). In addition, the content of 1-octene has also increased. These substances are mainly produced through the oxidation and degradation of lipids. Their aroma can be reminiscent of fresh grass, malt and various fruits. These ketones are derived from the oxidation of unsaturated fatty acids and the degradation of amino acids, and can also give fruity aroma.

[0073] (2) Compared with the wet fermentation of composite vegetable juice (sample 2), after the wet fermentation of composite vegetable juice emulsion (sample 3), the conger eel meat has a relatively higher content of the aforementioned volatile alcohols, aldehydes and ketones. This also shows that the wet fermentation method of composite vegetable juice emulsion in the present invention has higher fermentation efficiency and more significant fermentation effect.

[0074] 2.2 Impact on microbial diversity The conger eel meat before pickling in Comparative Example 1, Comparative Example 2 and Example 12 (respectively referred to as "sample 1", "sample 2" and "sample 3") was taken, and the microbial diversity was detected by high-throughput sequencing. The detection results are shown in Figure 6 .

[0075] from Figure 6It can be seen that in the unfermented conger eel meat (sample 1), the microbial community is mainly composed of Kocuria (13.92%), Pseudomonas (9.48%), Citrobacter (9.46%), Diaphorobacter (8.02%), Azospirillum (7.31%) and Dermacoccus (5.15%). In the conger eel meat after wet fermentation with composite vegetable juice (sample 2), the composition of the microbial community mainly includes Streptococcus (38.98%), Enterobacter (11.01%), Lactococcus (16.06%) and Citrobacter (2.36%). In the conger eel meat (sample 3) after wet fermentation with composite vegetable juice emulsion, the microbial community is mainly composed of Streptococcus (22.01%), Enterobacter (20.15%), Citrobacter (16.32%) and Lactococcus (13.48%). The difference in the above microbial community combined with the test results in "2.1 Effect on Volatile Flavor Components" confirms that the composite vegetable juice emulsion wet fermentation of conger eel meat has a faster fermentation speed than the composite vegetable juice wet fermentation method.

[0076] 2.3 Effect on organic acid content Wet fermentation was carried out according to the steps of Comparative Example 2 (recorded as "Sample 2") and Example 12 (recorded as "Sample 3"), and the organic acid content in the conger eel meat was detected at 0, 12, 24, 36 and 48 hours of wet fermentation, wherein 0 hour was equivalent to the conger eel meat before pickling in Comparative Example 1 (i.e., "Sample 1"). The method for detecting the organic acid content in the conger eel meat is as follows: 2.0 g of conger eel meat sample was weighed, 10 mL of phosphoric acid solution (v / v, 0.1%) was added, homogenized for 2 minutes, and then centrifuged at 10000 rpm for 10 minutes at 4°C. The above operation was repeated once, and then the two supernatants were combined in a 25 mL volumetric flask and fixed to volume with phosphoric acid solution (v / v, 0.1%). After the above solution passed through a 0.22 mm aqueous phase filter membrane, it was detected by a high performance liquid chromatography system. Chromatographic conditions such as: C18 chromatographic column; mobile phase is 0.1% H3PO4-methanol (v / v=93:7); detection wavelength 210nm; flow rate 1mL / min; column temperature: 30℃; injection volume 10μL. The test results are shown in Figure 7 .

[0077] from Figure 7It can be seen that as the wet fermentation proceeds, the total amount of organic acids in Sample 2 and Sample 3 both show an upward trend, and the total amount of organic acids in Sample 3 is significantly higher than that in Sample 2. The above changes in organic acid content can also prove that compared with the wet fermentation method using compound vegetable juice, the wet fermentation of conger eel meat using compound vegetable juice emulsion has a better fermentation effect.

[0078] 2.4 Effect on gel strength Wet fermentation was carried out according to the steps of Comparative Example 2 (referred to as "Sample 2") and Example 12 (referred to as "Sample 3"), and the gel strength of the conger eel meat was detected at 0, 12, 24, 36 and 48 hours of wet fermentation, wherein 0 hour was equivalent to the conger eel meat before pickling in Comparative Example 1 (i.e., "Sample 1"). The method for detecting the gel strength of conger eel meat is as follows: the conger eel meat sample was cut into uniform cylinders with a height of 2.5 cm and a diameter of 2 cm, and the gel strength program of the texture analyzer was used for determination, and the specific parameters for obtaining the gel strength data were as follows: probe type R0.5, detection speed 60 mm / min, initial force 0.2 N, deformation 60%. The test results are shown in Figure 8 .

[0079] from Figure 8 It can be seen that as the wet fermentation progresses, the gel strength of the conger eel meat shows a rising trend. From the 12th hour, the gel strength of sample 3 is significantly higher than that of sample 2. The gel strength of sample 2 shows a slow rising trend from the 24th hour, while sample 3 still shows a sharp rising trend, which also causes the gap between the two to continue to widen. From the results, it can be seen that whether it is the wet fermentation of composite vegetable juice or the wet fermentation of composite vegetable juice emulsion, the gel properties of conger eel meat can be improved and the meat becomes firm. At the same time, the wet fermentation of composite vegetable juice emulsion has a more prominent effect.

[0080] 2.5 Effects on the flavor of smoked dried conger eel The smoked dried conger eels prepared in Comparative Example 1, Comparative Example 2 and Example 12 (respectively recorded as "Sample 4", "Sample 5" and "Sample 6") were taken for sensory evaluation, and the method was as follows: a sensory evaluation team of 30 people was formed, and the team members were professionally trained in advance. A sensory evaluation table was formulated for smoked dried conger eel products as shown in Table 1. The evaluation items include color (20 points), aroma (30 points), taste (40 points) and morphology (10 points), which are all divided into 4 levels: excellent, good, general and poor. As shown in Table 2, the smoked dried conger eel products were further sensory scored for odors such as fermentation (0-9 points), smoky flavor (0-9 points), caramel flavor (0-9 points), floral flavor (0-9 points), earthy flavor (0-9 points), green flavor (0-9 points), sour taste (0-9 points) and astringency (0-9 points), which were divided into 4 levels: excellent, good, general and poor. The sensory evaluation results are shown in Table 3, Figure 1 and Fig. 9 .

[0081] Table 1 Sensory evaluation indexes of smoked dried conger eel Table 2 Evaluation index of odor of dried smoked conger eel Table 3 Sensory evaluation results of smoked dried conger eel samples 4 to 6 sample Total score level 4 56 Difference 5 78 good 6 95 excellent From Table 3, Figure 1 and Fig. 9 It can be seen that: (1) The dried conger eel smoked after wet fermentation with the composite vegetable juice emulsion of the present invention has the best sensory score, especially in terms of aroma and taste.

[0082] (2) The dried conger eel smoked after wet fermentation with composite vegetable juice emulsion has more prominent fermentation flavor, caramel flavor, floral aroma and sweetness than those prepared under the other two conditions. The higher fermentation flavor confirms that wet fermentation with composite vegetable juice emulsion has a higher fermentation efficiency than fermentation with composite vegetable juice alone. The caramel flavor, floral aroma and sweetness also reflect that it has a stronger "potato aroma". At the same time, it can be seen that wet fermentation has greatly reduced the smoky flavor, sourness, astringency and earthy taste brought by long-term smoking, which will make the smoked dried conger eel more prominent in the overall flavor presentation. "Potato aroma" characteristics.

[0083] Comparative Example 3: Preparation of smoked dried conger eel In Comparative Example 3, smoked dried conger eel was prepared according to the steps of Example 12, and the only difference from Example 12 was that in Comparative Example 3, the Chinese cabbage and Nostoc laminaria in step S2 were replaced with Chinese cabbage of equal mass. The remaining steps were the same as those of Example 12.

[0084] Comparative Example 4: Preparation of smoked dried conger eel In Comparative Example 4, smoked dried conger eel was prepared according to the steps of Example 12, and the only difference from Example 12 was that in Comparative Example 4, the Chinese cabbage and Nostoc laminaria in step S2 were replaced with Nostoc laminaria of equal mass. The remaining steps were the same as those of Example 12.

[0085] Comparative Example 5: Preparation of smoked dried conger eel In Comparative Example 5, smoked dried conger eel was prepared according to the steps of Example 12, and the only difference from Example 12 was that in Comparative Example 5, the seaweed in step S2 was replaced with seaweed of equal mass. The remaining steps were the same as those of Example 12.

[0086] Test Example 3: Effect of Vegetable Selection on the Flavor of Smoked Conger Eel The smoked dried conger eels prepared in Example 12 and Comparative Examples 3 to 5 (respectively referred to as "Sample 6", "Sample 7", "Sample 8" and "Sample 9") were subjected to sensory evaluation according to the method in Test Example 2. The results are shown in Tables 4, Fig.10 and Fig.11 . Fig.11 In the figure, the lines of some samples are covered by the lines of other samples, which are described as follows: the astringency score of sample 6 is 1; the fermentation taste score of sample 7 is 7; the green taste score of sample 8 is 5, the sour taste score is 3, and the astringency score is 2.

[0087] Table 4 Sensory evaluation results of smoked dried conger eel samples 6 to 9 sample Total score level 6 95 excellent 7 85 good 8 82 good 9 80 good From Table 4, Fig.10 and Fig.11 It can be seen that: in the composite vegetable juice emulsion used in the present invention, the combination of Chinese cabbage and Nostoc mollis can reduce the negative effects of long-term smoking to a greater extent and enhance the flavor of smoked dried conger eel; when Chinese cabbage (sample 7) or Nostoc mollis (sample 8) is used alone, or a combination of Chinese cabbage and seaweed (sample 9) is used, the smoked dried conger eel caused by long-term smoking is aggravated, and there is also a heavier earthy taste, sour taste and astringency in samples 8 and 9. This is because there is a complex interaction mechanism between the lactic acid bacteria in Chinese cabbage and the oligosaccharides in Nostoc mollis, which is not only reflected in the utilization and metabolism of oligosaccharides by lactic acid bacteria, but also in the regulation of oligosaccharides on the growth and metabolism of lactic acid bacteria. The two are interdependent and mutually reinforcing, and act together on the fermentation process of conger eels, thereby producing a unique fermentation effect and flavor characteristics.

[0088] Example 14 and Comparative Examples 6-7: Preparation of Smoked Dried Conger Eel In Example 14 and Comparative Examples 6-7, smoked dried conger eel was prepared according to the steps of Example 12, and the only difference from Example 12 was that in Examples 14-15 and Comparative Examples 6-7, the mass ratio of Chinese cabbage to Nostoc mollissima in step S2 was changed from 4:1 to 6:1, 1:1 and 10:1 respectively. The remaining steps were the same as in Example 12.

[0089] Test Example 4: Effect of the ratio of Chinese cabbage and seaweed on the flavor of smoked dried conger eel The smoked dried conger eels prepared in Examples 12, 14 and Comparative Examples 6-7 (respectively referred to as "Sample 6", "Sample 10", "Sample 11" and "Sample 12") were subjected to sensory evaluation according to the method in Test Example 2. The results are shown in Tables 5, Fig.12 and Fig.13 . Fig.13 In the figure, some sample lines are covered by other sample lines, which are described as follows: the astringency score of sample 6 is 1; the astringency score of sample 10 is 1, the sourness score is 2, the green taste score is 5, and the earthy taste score is 3; the sweetness score of sample 11 is 5.

[0090] Table 5 Sensory evaluation results of smoked dried conger eel samples 6, 10 to 12 sample Total score level 6 95 excellent 10 90 excellent 11 86 good 12 83 good From Table 5, Fig.12 and Fig.13 It can be seen that in the process of preparing the composite vegetable juice emulsion, the ratio between the Chinese cabbage and the sea moss will affect the quality of the smoked dried conger eel. When the mass ratio of Chinese cabbage to sea moss is 4 to 6:1, the smoked dried conger eel has a better flavor, and the smoky taste, earthy taste, sour taste and astringency caused by long-term smoking are lighter, and it has a more prominent fermentation taste, caramel taste, floral taste and sweetness; when the relative amount of the former of Chinese cabbage and sea moss is too small (sample 11), the earthy taste of the smoked dried conger eel will be aggravated, and the fermentation taste, caramel taste and sweetness will be weakened. When the relative amount of the latter is too small (sample 12), the smoked dried conger eel will have aggravated smoky taste, sour taste and astringency, and weakened fermentation taste, caramel taste and sweetness.

[0091] Comparative Example 8: Preparation of smoked dried conger eel In Comparative Example 8, smoked dried conger eel was prepared according to the steps of Example 12, and the only difference from Example 12 was that in Comparative Example 8, the conger eel head oil in step S2 was replaced with soybean oil of equal mass. The remaining steps were the same as those of Example 12.

[0092] Test Example 5: Effect of Oil Selection on the Flavor of Smoked Dried Conger Eel The smoked dried conger eels prepared in Example 12 and Comparative Example 8 (respectively referred to as "Sample 6" and "Sample 13") were subjected to sensory evaluation according to the method in Test Example 2. The results are shown in Tables 6, Fig.14 and Fig.15 .

[0093] Table 6 Sensory evaluation results of smoked dried conger eel samples 6 and 13 sample Total score level 6 95 excellent 13 77 good From Table 6, Fig.14 and Fig.15 It can be seen that in the composite vegetable juice emulsion used in the present invention, compared with other oils (such as soybean oil), the use of conger eel head oil can make the smoked dried conger eel meat more chewy, and can reduce the smoky taste, earthy taste, sour taste and astringency caused by long-term smoking to a greater extent, making the fermented taste, caramel taste, sweetness and floral taste of the smoked dried conger eel more prominent, making it have a "potato aroma". This is because the conger eel head oil contains a high content of polyunsaturated fatty acids and phospholipids. After these components are released under high-pressure microfluidization treatment, they can be more efficiently mixed and dispersed with the components in the vegetable juice. This process effectively reduces the tension at the oil-water interface and forms smaller emulsion droplets with better stability by intensifying hydrophobic interactions and the formation of hydrogen bonds. In addition, the polyunsaturated fatty acids and phospholipids in the conger eel head oil can affect the composition and fluidity of microbial cell membranes and act as signal molecules to induce the metabolic pathways and product generation of specific microorganisms during the fermentation process, thereby enriching the flavor level of the fermented product. In addition, polyunsaturated fatty acids and phospholipids can better serve as regulatory factors for enzymes in conger eel meat, and are more effective in promoting the decomposition of fat and protein in fish meat and increasing the content of alcohol, aldehydes, and organic acids in conger eel meat.

[0094] Unless otherwise defined, all technical terms and scientific terms used in the present invention have the same meanings as those commonly understood by ordinary technicians in the field to which the present disclosure belongs. Unless otherwise specified, the raw materials and equipment used in the present invention are conventional raw materials and equipment in the field and can be obtained from conventional commercial channels; unless otherwise specified, the methods used in the present invention are conventional methods in the field.

[0095] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent transformation made to the above embodiment based on the technical essence of the present invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing smoked dried conger eel based on composite vegetable juice emulsion fermentation, characterized in that: The following steps are involved: S1: Pulping the Chinese cabbage and Nostoc mollissima, mixing with the conger eel head oil, and emulsifying to obtain a composite vegetable juice emulsion; S2: immersing the conger eel in the composite vegetable juice emulsion for anaerobic fermentation to obtain a fermented fish body; S3: salting, drying and smoking the fermented fish body to obtain smoked dried conger eel.

2. The method according to claim 1, characterized in that In step S1, the mass ratio of the Chinese cabbage to the Nostoc laminaria is 4-6:

1.

3. The method according to claim 1, characterized in that: In step S1, the mass of the conger eel head oil is 10-14 wt % of the mass of the Chinese cabbage and Nostoc after pulping; the emulsification is performed by high-pressure micro-jetting, the micro-jet pressure is 25000-35000 psi, and the number of treatments is 6-10 times.

4. The method according to claim 1, characterized in that: In step S2, the temperature of the anaerobic fermentation is 25-28° C., and the time is 36-48 h; the mass ratio of the conger eel to the composite vegetable juice emulsion is 1: 3-4.

5. The method according to claim 1 or 2, characterized in that: In step S1, the preparation step of the conger eel head oil includes: cutting the conger eel head into pieces, placing the pieces in water, enzymolyzing the pieces with papain, centrifuging and taking the upper layer to obtain the conger eel head oil; the mass of the papain is 0.6-1.0% of the mass of the conger eel head; the enzymatic activity of the papain is 60000-100000 U / g; the enzymolysis temperature is 50-55°C, and the time is 2-4 h.

6. The method according to claim 1, characterized in that In step S2, before immersing the conger eel in the composite vegetable juice emulsion, the conger eel is pre-processed, and the steps include: removing the head and internal organs of the conger eel, and then washing it.

7. The method according to claim 1, characterized in that In step S3, the smoking temperature is 58-62° C. and the time is 30-40 min.

8. The method according to claim 1 or 7, characterized in that: In step S3, during the smoking process, the smoking wood used is one or more of oak, apple wood, alder and agarwood.

9. The method according to claim 1, characterized in that: In step S3, the pickling step includes: applying salt on the surface and inside of the fermented fish body, the amount of salt used is 80-90 g / 500 g of the fermented fish body mass, and pickling at 25-28° C. for 23-25 ​​h.

10. The method according to claim 1, characterized in that In step S3, the drying step includes: wiping off the salt particles and excess water on the surface of the pickled fish body, and drying at 50-60° C. for 28-30 hours.

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