Preparation method for deodorizing enzymolysis oyster juice

Abstract

The invention relates to the technical field of agricultural product processing, and particularly discloses a preparation method for deodorizing enzymolysis oyster juice. According to characteristic fishy smell substances in different processing stages of the enzymolysis oyster juice, physical adsorption and fermentation methods are adopted to reduce or remove the fishy smell substances, the content of flavor substances such as aldehydes and alcohols is increased, meanwhile, esterification reaction is strengthened, 1-pentene-3-ol with fruity flavor is increased, the aroma coordination degree of the oyster juice is optimized, and the quality of the oyster juice product is improved. Moreover, main flavor substances of the oyster juice are effectively retained through a physical adsorption and fermentation dual-treatment method, main fishy smell substances (1-octylene-3-alcohol, dimethyl disulfide and valeraldehyde) of the enzymolysis oyster juice can be effectively removed, meanwhile, 1-pentene-3-alcohol with fruity flavor is increased, and the yield of the oyster juice is increased by about 50%.

Description

Technical Field

[0001] The present application relates to the technical field of agricultural product processing, and in particular to a method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell. Background Art

[0002] Existing odor control technologies usually use a single method such as biological method or fermentation technology to improve the odor problem of oyster sauce in oyster seasoning products. At present, publication number CN117770415A discloses a method for increasing the umami taste of oyster sauce using enzymatic hydrolysis technology, using oysters and edible mushrooms crushed by high-pressure jet mill as enzymatic substrates, and using multiple enzymes to fully enzymatically hydrolyze to release flavor substances, and then using a deodorizing and flavor-enhancing reaction to remove the fishy smell of the oyster hydrolyzate, enhance the umami taste, and obtain oyster sauce; the prepared oyster sauce has a strong umami flavor, no fishy smell, no bitterness, and the flavor of the oyster sauce is harmonious; publication number CN117581971A discloses a method for improving the flavor of oyster enzymatic protein powder base The invention discloses a process and application. The process aims at the fishy smell of existing oyster enzymatic hydrolysis products, adopts multiple deodorization methods to achieve the purpose of completely removing the fishy smell, and improves the problems of poor flavor and poor solubility of oyster enzymatic protein powder base material. The oyster enzymatic protein powder base material produced by the invention is bright in color, orange-yellow in color, has no fishy smell, and has the fresh smell of fragrant grass and the sweetness of maltodextrin. Its palatability is significantly improved, and it can be directly consumed as a healthy food, and can also be used as a food base material for making various foods with oyster flavor, nutrition, functionality and color. Publication No. CN117502629A discloses a fermented oyster juice and a preparation method thereof. The method comprises the steps of first subjecting oyster meat and water to a pre-enzymatic hydrolysis with amylase, then subjecting the residue after enzymatic hydrolysis to solid-state fermentation and liquid fermentation in sequence, and using the enzyme system and microorganisms produced by the solid-state fermentation to subsequent liquid fermentation. This can significantly reduce the contamination of the oyster juice by the fishy components in the oyster digestive glands in the enzymatic hydrolyzed oyster juice, enhance the flavor and umami of the oyster juice, and obtain a fermented oyster juice with a harmonious aroma, full umami taste, and pure flavor. Publication No. CN117481315A discloses a method for removing fishy smell and improving flavor of oyster hydrolysate by using scented tea, the method comprising the following steps: step one: preparing oyster hydrolysate, adding scented tea to the oyster hydrolysate to prepare a sample; step two: scoring the odor of the sample; step three: calculating the short peptide yield of the sample; step four: analyzing and measuring the sample by electronic nose; step five: measuring the sample by GC-IMS, and calculating the retention index of each volatile compound; step six: obtaining the result and performing data analysis, the method has the advantages of effectively reducing the fishy smell and peculiar smell of oyster hydrolysate, being efficient, convenient and safe, and providing a useful reference for the development of high-value utilization technology for deep processing of oysters.

[0003] The above prior art does not analyze the types of fishy substances and the deodorization effect of enzymatic oyster juice at different processing stages. Therefore, the application effect cannot be well judged after the deodorization treatment is implemented, and oyster juice with pure flavor and harmonious aroma cannot be prepared. Summary of the invention

[0004] The purpose of this application is to overcome the shortcomings of the above-mentioned prior art and provide a method for preparing enzymatic oyster juice to remove the fishy smell. This application analyzes the types of fishy substances in different processing stages of enzymatic oyster juice, selects a combination of physical adsorption and flavor fermentation for characteristic compounds, and prepares oyster juice with pure flavor and harmonious aroma.

[0005] To achieve the above purpose, the technical solution adopted by this application is:

[0006] The present application provides a method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell, comprising the following steps:

[0007] S1. Take the thawed oysters, add distilled water, homogenize to obtain oyster raw material slurry, add neutral protease for enzymolysis, and then inactivate the enzyme in a boiling water bath to obtain enzymolysis solution;

[0008] S2, adding cyclodextrin to the enzymatic hydrolysate for embedding, and then centrifuging to obtain the treated enzymatic hydrolysate;

[0009] S3, adding saccharomyces cerevisiae to the treated enzymolysis clear solution and stirring to obtain a fermented enzymolysis clear solution;

[0010] S4. Concentrate the enzymatic supernatant after fermentation and centrifuge to obtain oyster juice concentrate.

[0011] In the technical scheme of the present application, the fishy substances in different processing stages of enzymatically hydrolyzed oyster juice are determined (through the method of volatile flavor substance analysis), and then the content of fishy substances is reduced after comprehensive treatment using physical adsorption and flavor fermentation methods according to the material characteristics of each stage. The fishy substances are effectively controlled, thereby improving the flavor of oyster juice, the quality and aroma of oyster juice.

[0012] The results of the analysis of the fishy substances in the different processing stages of the enzymatic hydrolysis of oyster juice show that the main fishy substances in the enzymatic hydrolysate are produced by fat oxidation, and the fishy substances are produced by fatty acid degradation reaction after subsequent processing. Therefore, the cyclodextrin physical adsorption method is used to remove most of the fat in the enzymatic hydrolysate stage to prevent the generation of fishy substances due to lipid oxidation in the subsequent processing. Cyclodextrin is a cyclic oligosaccharide with a three-dimensional hydrophobic cavity. It can form inclusion complexes with many guests and molecules based on the matching of the molecular size between the host and the guest, as well as the van der Waals force and the hydrophobic force, so as to achieve the purpose of degreasing. The enzymatic hydrolysate after defatting can promote the production of more flavor substances, such as aldehydes, alcohols, etc. after fermentation; the concentration of the fermented enzymatic hydrolysate can avoid the fishy substances caused by fatty acid degradation, and the fermentation can further strengthen the esterification reaction to achieve the purpose of improving the flavor of the enzymatic hydrolysed oyster juice.

[0013] As a preferred embodiment of the method for removing the fishy smell from oyster juice by enzymatic hydrolysis described in the present application, the addition amount of the neutral protease is 0.5% to 0.6% of the mass of the oyster raw material slurry, preferably 0.6%.

[0014] The use of the above-mentioned added amount of neutral protease can better enzymatically hydrolyze the oyster raw material.

[0015] As a preferred embodiment of the method for removing the fishy smell from enzymatically hydrolyzed oyster juice described in the present application, the amount of cyclodextrin added is 0.5-1.5% of the mass of the enzymatic hydrolyzate. Preferably, the amount of cyclodextrin added is 1.0% of the mass of the enzymatic hydrolyzate.

[0016] The cyclodextrin used in this application is a commonly used and easier to separate adsorbent in food, which is more guaranteed in terms of food safety. If other adsorbents such as activated carbon, etc., there are potential safety risks. In this application, cyclodextrin can be removed by centrifugation.

[0017] The present application adopts cyclodextrin added in the above range. Cyclodextrin is a cyclic oligosaccharide with a three-dimensional hydrophobic cavity. It can form inclusion complexes with many guests and molecules based on the matching of host-guest molecular sizes, as well as van der Waals forces and hydrophobic forces, thereby achieving the purpose of degreasing; and it can also remove the main fishy substance heptanal (fat smell and fishy smell).

[0018] When the addition amount of cyclodextrin is preferably 1.0% of the mass of the enzymatic hydrolyzate, the fishy smell of the enzymatic hydrolyzate is the lowest, and the flavor of the prepared enzymatic hydrolyzed oyster juice is better.

[0019] As a preferred embodiment of the method for removing the fishy smell from enzymatically hydrolyzed oyster juice described in the present application, the amount of brewer's yeast added is 0.2-0.4% of the mass of the treated enzymatically hydrolyzed clear liquid. Preferably, the amount of brewer's yeast added is 0.3% of the mass of the treated enzymatically hydrolyzed clear liquid.

[0020] The flavor type obtained by the fermentation of commonly used and safer yeast in this application is softer when paired with oyster sauce. If strains with excessively high microbial risks (such as lactic acid bacteria) are used, they are not suitable for seafood seasoning processing.

[0021] The present application uses brewer's yeast fermentation in the above-mentioned range of addition amount to further enhance the esterification reaction, promote the production of more flavor substances, such as aldehydes, alcohols, etc., and improve the flavor of enzymatically hydrolyzed oyster juice.

[0022] The addition amount of brewer's yeast is preferably 0.3% of the mass of the treated hydrolyzed liquid, which can reduce the protein loss rate in the hydrolyzed liquid, and can also increase the relative content of the main volatile flavor substances, reduce the irritating smell in the hydrolyzed liquid, and increase the aroma components (isovaleraldehyde, phenylethanol, caryophyllene, etc.).

[0023] The present application adopts physical adsorption methods such as cyclodextrin and flavor fermentation methods to effectively reduce or remove fishy substances, increase the content of flavor substances such as aldehydes and alcohols, and at the same time strengthen the esterification reaction, increase the fruity 1-penten-3-ol, thereby optimizing the aroma coordination of oyster juice and improving the quality of oyster juice products.

[0024] Moreover, the double treatment of physical adsorption and fermentation effectively removes the fishy smell of the enzymatic oyster juice, while increasing the fruity 1-penten-3-ol. The protein loss rate is less than 5%, and the oyster juice yield is increased by about 50%.

[0025] As a preferred embodiment of the method for removing the fishy smell from oyster juice by enzymatic hydrolysis described in the present application, in the step S1, the temperature of the enzymatic hydrolysis is 45°C to 50°C, and the time of the enzymatic hydrolysis is 3 hours.

[0026] As a preferred embodiment of the method for removing the fishy smell from oyster juice by enzymatic hydrolysis described in the present application, in step S1, the material-liquid ratio of oysters to distilled water is 1:2.

[0027] As a preferred embodiment of the method for removing the fishy smell from oyster juice by enzymatic hydrolysis described in the present application, in the step S2, the embedding temperature is 40° C. and the embedding time is 1 hour.

[0028] By adopting the above-mentioned embedding conditions, the fat in the enzymatically hydrolyzed oyster juice can be better removed, and the fishy substances in the enzymatically hydrolyzed oyster juice can be better removed. At the same time, the fruity 1-penten-3-ol is increased, the aroma coordination of the oyster juice is optimized, and the quality of the oyster juice product is improved.

[0029] As a preferred embodiment of the method for removing the fishy smell of enzymatically hydrolyzed oyster juice described in the present application, in step S2, when cyclodextrin is added to the enzymatic solution for embedding, the pH of the enzymatic solution is adjusted to 6.5-7.0.

[0030] As a preferred embodiment of the method for removing the fishy smell from enzymatically hydrolyzed oyster juice described in the present application, in the step S2, the centrifugal speed is 4000 r / min, and the centrifugal time is 15 min; in the step S4, the centrifugal speed is 3000 r / min, and the centrifugal time is 30 min.

[0031] As a preferred embodiment of the method for removing the fishy smell from enzymatically hydrolyzed oyster juice described in the present application, in the step S4, the fermented enzymatically hydrolyzed clear liquid is kept warm at a temperature of 105° C. for 6 hours to complete the concentration and reach the end point.

[0032] The enzymatic hydrolysis clear liquid after concentrated fermentation in the present application can avoid the fishy smell substances caused by fatty acid degradation. At the same time, fermentation can further strengthen the esterification reaction and improve the flavor of the enzymatic hydrolyzed oyster juice.

[0033] This application conducts a material analysis on the fishy substances in different processing stages of enzymatically hydrolyzed oyster juice, uses a comprehensive method of physical adsorption and flavor fermentation to effectively control the fishy substances and applies them to production.

[0034] Compared with the prior art, this application has the following beneficial effects:

[0035] The present application provides a method for preparing enzymatic oyster juice to remove fishy smell. According to the characteristic fishy smell substances in different processing stages of enzymatic oyster juice, physical adsorption and fermentation methods are used to reduce or remove the fishy smell substances, and the content of flavor substances such as aldehydes and alcohols is increased. At the same time, the esterification reaction is strengthened, and the fruity 1-pentene-3-ol is increased, so as to achieve the optimization of the aroma coordination of oyster juice and improve the quality of oyster juice products. In addition, through the physical adsorption and fermentation double treatment method, the main flavor substances of oyster juice are effectively retained, and the main fishy smell substances (1-octen-3-ol, dimethyl disulfide, and valeraldehyde) of enzymatic oyster juice can be effectively removed, and the fruity 1-pentene-3-ol is increased, and the oyster juice yield is increased by about 50%. DETAILED DESCRIPTION

[0036] In order to better illustrate the purpose, technical solutions and advantages of the present application, the present application will be further described with reference to specific embodiments below.

[0037] In the following examples and comparative examples, the experimental methods used are conventional methods unless otherwise specified, and the materials, reagents, etc. used are all commercially available unless otherwise specified.

[0038] Example 1: A method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell

[0039] This embodiment provides a method for removing the fishy smell from oyster juice by enzymatic hydrolysis, comprising the following steps:

[0040] S1. Enzymatic hydrolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a constant temperature water bath at 50°C for 3h; take the enzymatically hydrolyzed oyster raw material slurry in a boiling water bath at 100°C for 10min to inactivate the enzyme, take out and cool to room temperature to obtain an enzymatic solution.

[0041] S2, adsorption: add 0.5% cyclodextrin by weight of the enzymatic hydrolysate to the enzymatic hydrolysate obtained in step S1, stir thoroughly, adjust the pH to 6.5, embed in a 40°C constant temperature water bath for 1 hour, and centrifuge at 4000 r / min for 15 minutes to obtain the treated enzymatic hydrolysate.

[0042] S3, fermentation: adding 0.2% of the mass of the enzymatic hydrolysis supernatant to the treated enzymatic hydrolysis supernatant obtained in step S2 with brewer's yeast, stirring evenly and keeping warm at 45° C. for 100 min to obtain a fermented enzymatic hydrolysis supernatant.

[0043] S4, concentration: the fermented enzymatic supernatant obtained in step S3 is kept at 105° C. for 6 h, and centrifuged at 3000 r / min for 30 min to obtain oyster juice concentrate.

[0044] Example 2: A method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell

[0045] This embodiment provides a method for removing the fishy smell from oyster juice by enzymatic hydrolysis, comprising the following steps:

[0046] S1. Enzymolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a constant temperature water bath at 50°C for 3h; take the raw material slurry after enzymolysis, inactivate the enzyme in a boiling water bath at 100°C for 10min, take out and cool to room temperature to obtain an enzymolysis solution.

[0047] S2, adsorption: add cyclodextrin of 1% by mass of the enzymatic hydrolysate to the enzymatic hydrolysate obtained in step S1, stir thoroughly, adjust the pH to 6.5, embed in a constant temperature water bath at 40°C for 1 hour, and centrifuge at 4000 r / min for 15 minutes to obtain the treated enzymatic hydrolysate.

[0048] S3, fermentation: adding 0.3% of the mass of the enzymatic hydrolysis supernatant to the treated enzymatic hydrolysis supernatant obtained in step S2 with brewer's yeast, stirring evenly and keeping warm at 45° C. for 100 min to obtain a fermented enzymatic hydrolysis supernatant.

[0049] S4, concentration: the fermented enzymatic supernatant obtained in step S3 is kept at 105°C for 6 hours, and centrifuged at 3000 r / min for 30 minutes to obtain oyster juice concentrate.

[0050] Example 3: A method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell

[0051] This embodiment provides a method for removing the fishy smell from oyster juice by enzymatic hydrolysis, comprising the following steps:

[0052] S1. Enzymolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a constant temperature water bath at 50°C for 3h; take the raw material slurry after enzymolysis, inactivate the enzyme in a boiling water bath at 100°C for 10min, take out and cool to room temperature to obtain an enzymolysis solution.

[0053] S2. Adsorption: add cyclodextrin in an amount of 1.5% by mass of the enzymatic hydrolysate to the enzymatic hydrolysate obtained in step S1, stir thoroughly, adjust the pH to 6.5, embed in a constant temperature water bath at 40° C. for 1 hour, and centrifuge at 4000 r / min for 15 minutes to obtain the treated enzymatic hydrolysate.

[0054] S3, fermentation: adding 0.4% of the mass of the enzymatic hydrolysis supernatant to the treated enzymatic hydrolysis supernatant obtained in step S2 with brewer's yeast, stirring evenly and keeping warm at 45° C. for 100 min to obtain a fermented enzymatic hydrolysis supernatant.

[0055] S4, concentration: the fermented enzymatic supernatant obtained in step S3 is kept at 105°C for 6 hours, and centrifuged at 3000 r / min for 30 minutes to obtain oyster juice concentrate.

[0056] Comparative Example 1

[0057] This comparative example provides a method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell, comprising the following steps:

[0058] S1. Enzymatic hydrolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a 50°C constant temperature water bath for 3 hours. Take the raw material slurry after enzymolysis and inactivate the enzyme in a 100°C boiling water bath for 10 minutes, take out and cool to room temperature to obtain an enzymatic solution.

[0059] S2. Centrifugation: Centrifuge the enzymatic hydrolysate at 4000 r / min for 15 min to obtain the treated enzymatic hydrolysate.

[0060] S3. Concentration: After the enzymatic hydrolysis liquid is kept at 105°C for 6 hours, it is centrifuged at 3000 r / min for 30 minutes to obtain oyster juice concentrate.

[0061] Comparative Example 2

[0062] Compared with Example 2, the only difference is that activated carbon is used instead of cyclodextrin, and the remaining steps are the same as Example 2.

[0063] Comparative Example 3

[0064] Compared with Example 2, the only difference is that sweet wine yeast is used instead of brewer's yeast, and the remaining steps are the same as Example 2.

[0065] Comparative Example 4: A method for preparing enzymatically hydrolyzed oyster juice to remove fishy smell (adsorption only)

[0066] This comparative example provides a method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell, comprising the following steps:

[0067] S1. Enzymolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a constant temperature water bath at 50°C for 3h; take the raw material slurry after enzymolysis, inactivate the enzyme in a boiling water bath at 100°C for 10min, take out and cool to room temperature to obtain an enzymolysis solution.

[0068] S2, adsorption: add cyclodextrin of 1% by mass of the enzymatic hydrolysate to the enzymatic hydrolysate obtained in step S1, stir thoroughly, adjust the pH to 6.5, embed in a constant temperature water bath at 40°C for 1 hour, and centrifuge at 4000 r / min for 15 minutes to obtain the treated enzymatic hydrolysate.

[0069] S3, concentration: the enzymatic hydrolysis supernatant obtained in step S2 is kept at 105° C. for 6 h, and centrifuged at 3000 r / min for 30 min to obtain oyster juice concentrate.

[0070] Comparative Example 5: A method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell (fermentation only)

[0071] This comparative example provides a method for preparing enzymatically hydrolyzed oyster juice to remove the fishy smell, comprising the following steps:

[0072] S1. Enzymolysis: Take the thawed oysters, add distilled water according to the material-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a constant temperature water bath at 50°C for 3h; take the raw material slurry after enzymolysis, inactivate the enzyme in a boiling water bath at 100°C for 10min, take out and cool to room temperature to obtain an enzymolysis solution.

[0073] S2. Centrifugation: Centrifuge the enzymatic hydrolysate at 4000 r / min for 15 min to obtain the treated enzymatic hydrolysate.

[0074] S3, fermentation: adding 0.3% of the mass of the enzymatic hydrolysis supernatant to the treated enzymatic hydrolysis supernatant obtained in step S2 with brewer's yeast, stirring evenly and keeping warm at 45° C. for 100 min to obtain a fermented enzymatic hydrolysis supernatant.

[0075] S4, concentration: the fermented enzymatic supernatant obtained in step S3 is kept at 105°C for 6 hours, and centrifuged at 3000 r / min for 30 minutes to obtain oyster juice concentrate.

[0076] Experimental Example 1: Analysis of flavor substances in different processing stages of enzymatic oyster juice

[0077] The various processed products in the process of enzymatic hydrolysis of oyster juice were taken as the research objects: the enzymatic hydrolyzate, the concentrated solution, and the clear liquid of the separated upper layer were taken as the analysis objects, and the flavor components were analyzed.

[0078] Experimental methods:

[0079] (1) Preparation of enzymatic hydrolysate: Take the thawed oysters, add distilled water at a solid-liquid ratio of 1:2, homogenize in a wall breaking machine to obtain an oyster raw material slurry, adjust the pH to 7.0, add 0.6% neutral protease by weight of the oyster raw material slurry, stir well, and enzymolyze in a 50°C constant temperature water bath for 3 h; take the enzymatically hydrolyzed raw material slurry and inactivate the enzyme in a 100°C boiling water bath for 10 min, take out and cool to room temperature, and then centrifuge at 4000 r / min for 15 min to obtain a treated enzymatic hydrolysate.

[0080] Preparation of concentrated solution: The enzymatic hydrolysate prepared above was kept at 105°C for 6 hours to obtain a concentrated solution.

[0081] Separate the upper clear liquid: centrifuge the above prepared concentrated solution at 3000r / min for 30min to obtain the separated upper clear liquid.

[0082] (2) Instruments and consumables: constant temperature magnetic stirrer (08-2T, Shanghai Meiyingpu Instrument Manufacturing Co., Ltd.); solid phase microextraction device (57330-U, supelco); 50 / 30um DVB / CAR / PDMS solid phase microextraction needle (57348-U, supelco); gas chromatography-mass spectrometer (Agilent 6890N-5973GC-MS); gas chromatography column: HP-INNOWax (60mx 250μm x 0.25μm).

[0083] (3) Extraction conditions: Weigh 5 g of sample into a 20 mL extraction bottle, seal it, place it in an 85°C water bath, and stir it at 500 rpm. After equilibration for 20 min, insert the extraction needle and extract for 30 min. Before use, activate the extraction needle at the gas injection port for 20 min (250°C).

[0084] (4) GC-MS analysis: The GC conditions were as follows: inlet temperature 250 °C, GC-MS interface temperature 250 °C, carrier gas flow rate 1.5 mL / min, split ratio 4:1. Temperature program: initial temperature 40 °C, hold for 5 min, increase the temperature to 250 °C at a rate of 5 °C / min and hold for 10 min. MS conditions: ion source temperature 230 °C, quadrupole temperature 150 °C, EI ionization energy 70 eV, full scan from 35 to 550 da.

[0085] (5) Principal component analysis: Whether a certain substance has a great impact on the flavor depends not only on its concentration but also on its threshold value. That is, the contribution of volatile compounds to the overall flavor of the sample is jointly determined by their concentration and threshold value in the flavor system.

[0086] Therefore, in this study, the contribution of the substance to the overall flavor of the sample was evaluated by calculating the relative odor activity value (ROAV). Where Cri and Ti are the relative concentrations and corresponding sensory thresholds of each compound, and Cmax and Tmax are the relative concentrations and corresponding sensory thresholds of the component with the greatest contribution to the overall flavor. All components satisfy 0 < ROAVi < 100, and the greater the ROAVi value, the greater the contribution of the component to the overall flavor of the sample. Flavor compounds with ROAV > 1 are the main flavor components of the analyzed sample.

[0087] Experimental results:

[0088] The comparison of the types and relative contents of the main volatile flavor substances in different processed products of oysters is shown in Table 1 and Table 2.

[0089] Table 1 Types of the main volatile flavor substances in different processed products of oysters

[0090] Enzyme hydrolysate Concentrate Separate the upper layer Alcohols 15 23 21 Aldehydes 15 18 32 Ketones 11 21 22 Ethers 8 2 5 Esters 23 23 28 Acids 3 4 2 Olefins 4 11 10

[0091] Table 2 Relative contents (%) of the main volatile flavor substances in different processed products of oysters

[0092] Enzyme hydrolysate Concentrate Separate the upper layer Alcohols 22.14 15.60 13.74 Aldehydes 15.42 11.86 18.66 Ketones 8.23 10.04 16.17 Ethers 5.42 0.67 1.36 Esters 12.61 8.00 13.11 Acids 0.66 2.11 0.39 Olefins 4.92 3.47 1.08 Alkanes 0.77 1.43 5.72 Furans 1.72 1.68 3.10 total 71.90 54.85 73.34

[0093] Analysis found that after the enzymatic hydrolysate was concentrated at high temperature for a long time, the substances such as alcohols, aldehydes, esters, ethers, and olefins decreased, by 6.54, 3.57, 4.76, 4.61, and 1.45% respectively, while the substances such as ketones, acids, and pyrazines increased slightly (Table 3).

[0094] Table 3 Comparison of volatile flavor substances before and after concentration

[0095]

[0096] The number of volatile flavor substances in the supernatant obtained by separation of the concentrate decreased by 11, mainly ketones, esters and pyrazines, which decreased by 4.56, 2.22 and 2.25% respectively, and aldehydes increased by 7.28%. The threshold of aldehydes is relatively low, and a very low concentration can have a significant effect on the flavor of oyster liquid. After centrifugation of the oyster concentrate, the relative content of aldehydes increased significantly (Table 4).

[0097] Table 4 Analysis of flavor substance changes before and after centrifugation

[0098]

[0099]

[0100] Result analysis:

[0101] Aldehydes are a class of substances that play a leading role in the flavor of aquatic products. The threshold of aldehydes is low, and some aldehydes can produce obvious flavor overlap effects with other components. Therefore, they can make a significant contribution to the flavor when present in trace amounts. The enzymatic hydrolysis process increased the relative contents of (E,E)-2,6-nonadienal, melonaldehyde 2,6-dimethyl-5-heptenal, furfural, benzaldehyde, and trans-4-decenal in oysters from 0.92, 0.76, 0.11, 0.11, and 0.05% to 1.54, 2.99, 0.46, 1.32, and 0.23%, respectively; the relative contents of heptaldehyde, phenylacetaldehyde, trans-2-heptenal, (E)-citral / geranial, citral, and pineapple aldehyde increased to 0.28, 0.92, 0.31, 0.31, 0.40, and 0.25%, respectively. The enzymatic hydrolysis process increases the green fragrance, sweet fragrance and other aroma and flavor of the product. Enaldehydes and dienals are produced by the oxidation of unsaturated fatty acids and are the main source of fishy smell in the enzymatic hydrolyzate.

[0102] After high-temperature concentration of the enzymatic hydrolysate, the relative contents of 2-furanmethanol (burnt bitter aroma), lauryl butyrate (rich fruity aroma), isovaleraldehyde (chocolate aroma), and phenylacetaldehyde (green aroma, rose aroma, and chocolate aroma) increased significantly; at the same time, some flavor-enhancing aldehydes were added, such as nerol, cocoaldehyde, melon aldehyde, 3,7-dimethyl (E)-2,6-octadienal, 4-carboxaldehyde, 5-methyl 2-furancarboxaldehyde, and cycloho-citral. The relative contents of furfural, benzaldehyde, and melon aldehyde decreased. The content and types of ester substances increased significantly, indicating that esterification occurred during high-temperature concentration, and new substances were added: 2,5-dimethylpyrazine and 2,3,5-trimethylpyrazine, which mainly showed fat aroma and fishy smell.

[0103] The concentrate was centrifuged to obtain a clear liquid in the upper separation layer. Compared with the concentrate, the relative contents of 2-furanmethanol (burnt bitter aroma), isovaleraldehyde (chocolate aroma), phenylacetaldehyde (green aroma, rose aroma, chocolate aroma), furfural, 2,5-dimethylpyrazine (fat aroma), and 2,3,5-trimethylpyrazine (burnt aroma) in the clear liquid in the upper separation layer increased significantly, but the types and contents of aldehydes and esters decreased, indicating that the separation process removed some flavor components, resulting in an increase in the relative content of the main components. The upper separation layer mainly showed green aroma, burnt aroma and fat aroma.

[0104] in conclusion:

[0105] (1) The main odorous substances in the hydrolysate are 1-octen-3-ol, heptanal, and trans-2-heptenal, which are mainly produced by fat oxidation.

[0106] (2) The concentrate mainly has caramel, chocolate, nut and fat aromas. The main fishy substances are: trans, trans-2,4-decadienal (fishy, ​​grassy), 2,3-pentanedione (creamy, caramel aroma). In addition, ketones are derived from the degradation reaction of fatty acids in oyster meat, which can enhance the intensity of fishy smell.

[0107] The clear liquid in the separated upper layer mainly has caramel aroma, chocolate aroma, wine aroma and fat aroma; the main fat odor substances are: 2,3-pentanedione (cream, caramel aroma), lauryl alcohol (grease smell), and 2-nonanone (sweet fragrance, cream smell).

[0108] Through the analysis of the fishy substances in the different processing stages of the hydrolyzed oyster juice, it was found that the main fishy substances in the hydrolyzate are produced by fat oxidation, and the fatty acid degradation reaction occurs after subsequent processing to produce fishy substances. Therefore, the present application designs Examples 1-3, which use physical adsorption to remove fat in the hydrolyzate stage before subsequent processing. Cyclodextrin is a cyclic oligoglucose with a three-dimensional hydrophobic cavity. It can form inclusion complexes with many guests and molecules based on the matching of the molecular size between the host and the guest, as well as the van der Waals force and the hydrophobic force, so as to achieve the purpose of defatting. The hydrolyzate after defatting can be fermented to promote the production of more flavor substances, such as aldehydes, alcohols, etc.; the hydrolyzate after high-temperature concentration and defatting can avoid the fishy substances caused by fatty acid degradation, and fermentation can further strengthen the esterification reaction, thereby achieving the purpose of improving the flavor of the hydrolyzed oyster juice.

[0109] Comparison of the effects of Experimental Example 2, Examples 1 to 3 and Comparative Examples 1 to 5

[0110] 1. After comprehensive treatment of adsorption and fermentation, the centrifugal yield of oyster juice in Examples 1 to 3 increased by 47.78-53.95% compared with the untreated group (Comparative Example 1), other treatment groups (Comparative Examples 2 to 3) and Comparative Examples 4 to 5.

[0111] 2. Comparison of flavor results of enzymatic hydrolyzed liquid:

[0112] After the oyster hydrolysate was treated with different concentrations of cyclodextrin (Examples 1-3 and Comparative Example 4, the hydrolysate was taken for detection in step S2), the flavor volatile substances in the hydrolysate also changed. After 0.5% cyclodextrin treatment, pineapple ketone (burnt sweet aroma) and melon aldehyde (green aroma, melon, cucumber-like aroma) were retained as key flavor substances in the hydrolysate; the modified flavor substances were: ethyl myristate (sweet aroma), trans-2-dodecenal (barbecue aroma), 2-methoxy-3-methylpyrazine (burnt aroma), trans-4-decenal (citrus aroma, fat aroma), (E,E)-2,4-heptadienal (moss and fishy smell); hexanal (fruit aroma), phenylethanol (sweet aroma), and furfuryl alcohol (rose aroma) decreased. After 0.5% cyclodextrin treatment, the fishy smell of the hydrolysate increased and the flavor substances decreased.

[0113] The key flavor substances in the hydrolyzed liquid after treatment with 1.0% cyclodextrin are: pineapple ketone (burnt sweet aroma), melon aldehyde (green aroma, melon, cucumber-like aroma), 2-methoxy-3-methylpyrazine (burnt aroma); modified flavor substances are: ethyl myristate (sweet aroma), trans, trans-2,4-decadienal (citrus-like sweet aroma), isovaleraldehyde (chocolate aroma), citral (lemon aroma), trans-2-octenal (fishy smell, oxidized flavor), 2-ethylfuran (burnt aroma). Substances with potential flavors are: phenylethanol (sweet aroma) and furfuryl alcohol (rose aroma). It shows that after the oyster hydrolyzate is treated with 1.0% cyclodextrin, due to the removal of 90% of the fat, the hydrolyzed liquid after treatment mainly has the aroma of cucumber, retains the sweet aroma of enzymatic hydrolysis, and the fishy smell of fat oxidation is significantly reduced.

[0114] The key flavor substances in the enzymatic hydrolysis liquid after treatment with 1.5% cyclodextrin are: melon aldehyde (green, melon, cucumber-like aroma), isovaleraldehyde (chocolate aroma), 2-methoxy-3-methylpyrazine (earthy smell), trans-4-decenal (citrus and fat aroma), (E,E)-2,4-heptadienal (mossy and fishy smell); the modified flavor substances are: ethyl myristate (sweet, creamy smell), trans, trans-2,4-decadienal (citrus-like sweet aroma), isovaleraldehyde (chocolate aroma), heptaldehyde (fat and fishy smell), 2-nonanone (green, creamy smell), trans-2-octenal (fat, fishy smell), phenylethanol (sweet aroma), furfuryl alcohol (rose aroma), 2-ethylfuran (burnt aroma), and the fishy substances are significantly increased.

[0115] Therefore, cyclodextrin treatment can remove the main fishy substance heptaldehyde (fat and fishy smell), but after 0.5% addition treatment, the fishy substance (E,E)-2,4-heptadienal (moss and fishy smell) in the enzymatic supernatant increased and the flavor substances decreased. After 1.5% addition treatment, the main fishy substance heptaldehyde (fat and fishy smell) in the enzymatic supernatant still played the main flavor, and the aldehyde fishy substances increased (Table 5). Therefore, the fishy smell of the enzymatic supernatant after treatment with 1.0% cyclodextrin addition concentration was the lowest.

[0116] Table 5 Types and numbers of volatile substances before and after cyclodextrin

[0117]

[0118] 3. Comparison of flavor results after fermentation:

[0119] The protein loss rate was calculated for the enzymatic supernatant after fermentation with different addition amounts of brewer's yeast (Examples 1-3, the enzymatic supernatant after fermentation was taken for testing in step S3), and it was found that when the addition amount was 0.3%, the protein loss rate was the lowest (Table 6). Therefore, the subsequent flavor analysis was performed on the treatment group (Example 2, step S3) and comparative example 1.

[0120] Table 6 Effect of the amount of brewer's yeast added on the protein loss rate of the enzymatic supernatant

[0121] Yeast addition amount (%) Protein loss rate (%) Example 1 (the amount of yeast added is 0.2%) 16.13±3.29 Example 2 (the amount of yeast added is 0.3%) 15.73±0.52 Example 3 (the amount of yeast added is 0.4%) 22.63±2.31

[0122] After fermentation of oyster hydrolysate by Saccharomyces cerevisiae, the total number of volatile flavor substances increased by 16, mainly aldehydes, esters, alkenes and alkanes, which increased by 3, 3, 4 and 3 respectively. The relative content of the main volatile flavor substances after yeast fermentation also increased by 24.76% compared with that before fermentation, and the relative content of alkenes, aldehydes and esters increased the most, increasing by 2.74, 0.96 and 0.24 times respectively (Table 7).

[0123] Table 7 Changes in relative content and types of flavor substances before and after fermentation

[0124]

[0125]

[0126] Among the key flavor compounds in the products before and after biological fermentation, the key flavor compounds before fermentation are: 2-ethyl-3,5-dimethylpyrazine, methylfurfuryl disulfide, phenylacetaldehyde, dimethyl trisulfide; the key compounds after fermentation are: 2-ethyl-3,5-dimethylpyrazine, phenylacetaldehyde, 2-acetyl-3-methylpyrazine, 4-methylbenzaldehyde (almond aroma), and p-menthene (mint aroma). In addition, among the modified flavor compounds: the methylfurfuryl disulfide with irritating taste is missing in the product after biological fermentation treatment, and isovaleraldehyde, phenylethanol, and caryophyllene with aroma components are increased. The results show that biological fermentation treatment can reduce the irritating smell in the oyster enzymatic clear liquid and increase the aroma (Table 8).

[0127] Table 8 Key flavor compounds in the products of oyster hydrolysate before and after biological fermentation

[0128]

[0129]

[0130] 4. The effects of different deodorization methods on oyster juice concentrate.

[0131] The total relative content of aldehydes, alcohols, ketones, hydrocarbons, and nitrogen-containing sulfur heterocyclic compounds in the oyster juice concentrate treated with cyclodextrin decreased (Table 9), and the ester content of the oyster juice concentrate treated with cyclodextrin and brewer's yeast (Example 3) increased by 4.21-7.37%.

[0132] Table 9 Comparison of relative contents of volatile flavor substances after treatment with different methods

[0133]

[0134] Straight-chain saturated aldehydes, such as valeraldehyde, have a pungent taste, and heptanal has a fatty taste. When the concentration of these aldehydes is low, they have a fresh and fatty smell, which plays a positive role in the aroma of the finished product; when the concentration is high, they will become a foreign smell. The main fishy smell in the oyster juice concentrate comes from valeraldehyde. After adsorption treatment, the contents of valeraldehyde and heptanal are significantly reduced. The content of valeraldehyde and heptanal in the adsorption and fermentation combined treatment group decreased most significantly, among which the oyster juice concentrate adsorbed with cyclodextrin and fermented with brewer's yeast (Example 3) had the lowest content of valeraldehyde and heptanal (Table 10).

[0135] Non-aliphatic aldehydes, such as 2-methylbutanal, 3-methylbutanal, benzaldehyde, phenylacetaldehyde, and isobutyraldehyde, originate from Strecker degradation or microbial metabolism of branched-chain amino acids and phenylalanine, and mainly contribute to chocolate, almond and caramel flavors. They are the main flavor components in oyster juice concentrate. Benzaldehyde may come from undigested algae in the oyster body.

[0136] After fermentation, the relative contents of the main flavor substances such as benzaldehyde, phenylacetaldehyde, 5-methylfurfural, etc., which contribute to the oyster juice concentrate, decreased, and the pungent furfural and fishy valeraldehyde also decreased significantly, but the lipids were further oxidized to produce heptanal due to the action of yeast. The group treated with koji instead of yeast (Comparative Example 3) retained the main flavor components of the oyster juice concentrate, and the content of irritating and fishy substances was the lowest. The group treated with cyclodextrin and brewer's yeast (Example 3) increased cinnamaldehyde with cinnamon aroma.

[0137] Table 10 Effects of different treatment methods on the main aldehyde components in oyster juice concentrate

[0138]

[0139]

[0140] The threshold of ketone compounds is relatively similar to that of aldehydes. In food, they are mainly derived from the degradation of amino acids, thermal oxidation of unsaturated fatty acids and oxidation by microorganisms, which have a certain enhancement effect on the fishy smell. However, they have little effect on the volatile flavor of oyster juice concentrate and have no major contribution.

[0141] The threshold of saturated alcohol in alcohol compounds is higher than that of unsaturated alcohol. Furfuryl alcohol, benzyl alcohol and phenylethyl alcohol, which contribute more to the flavor of oyster juice concentrate, mainly present flowery and soy sauce flavors, and are the main flavor components of oyster enzymatic concentrate. In addition, the fishy 1-octen-3-ol is significantly reduced after treatment with brewer's yeast, and the fruity 1-penten-3-ol is increased after comprehensive treatment with cyclodextrin and brewer's yeast (Example 3) (Table 11).

[0142] Table 11 Effects of different treatment methods on the main alcohol components in oyster juice concentrate

[0143]

[0144]

[0145] Conclusion: After the enzymatic hydrolysis clear liquid was physically adsorbed by cyclodextrin, most of the fat was first attached to prevent the subsequent processing process from generating fishy substances due to lipid oxidation. After centrifugation to remove the adsorbent, brewer's yeast was added for flavor fermentation to obtain more flavor substances such as aldehydes and alcohols, while enhancing the esterification reaction in the subsequent concentration process. The results showed that after the dual treatment of physical adsorption and biological fermentation, the main flavor substances of oyster juice were effectively retained. Through the analysis of substances in different processing stages of enzymatic hydrolysis of oyster juice, it was concluded that the main fishy substances were 1-octen-3-ol, dimethyl disulfide, and valeraldehyde. After cyclodextrin adsorption and brewer's yeast fermentation, they were effectively removed, and the fruity 1-penten-3-ol was added, and the oyster juice yield was increased by about 50%. The application adopts the comprehensive treatment of brewer's yeast and cyclodextrin to effectively remove the fishy smell of oyster hydrolysis oyster juice, and forms a preparation method that can be used in production.

[0146] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present application rather than to limit the scope of protection of the present application. Although the present application has been described in detail with reference to the preferred embodiments, ordinary technicians in this field should understand that the technical solution of the present application can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present application.

Claims

1. A method for removing the fishy smell of enzymatically hydrolyzed oyster juice, characterized in that: The following steps are involved: S1. Take the thawed oysters, add distilled water, homogenize to obtain oyster raw material slurry, add neutral protease for enzymolysis, and then inactivate the enzyme in a boiling water bath to obtain enzymolysis solution; S2, adding cyclodextrin to the enzymatic hydrolysate for embedding, and then centrifuging to obtain the treated enzymatic hydrolysate; S3, adding saccharomyces cerevisiae to the treated enzymolysis clear solution and stirring to obtain a fermented enzymolysis clear solution; S4. Concentrate the enzymatic supernatant after fermentation and centrifuge to obtain oyster juice concentrate.

2. The method for removing the fishy smell from enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: The addition amount of the neutral protease is 0.5% to 0.6% of the mass of the oyster raw material slurry.

3. The method for removing the fishy smell from enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: The added amount of the cyclodextrin is 0.5-1.5% of the mass of the enzymatic hydrolysate.

4. The method for removing the fishy smell from enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: The addition amount of the brewer's yeast is 0.2-0.4% of the mass of the treated enzymatic hydrolysis clear liquid.

5. The method for removing the fishy smell from enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In step S1, the temperature of enzymolysis is 45° C. to 50° C., and the time of enzymolysis is 3 hours.

6. The method for removing the fishy smell from enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In step S1, the material-liquid ratio of oysters to distilled water is 1:

2.

7. The method for removing the fishy smell of enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In step S2, the embedding temperature is 40° C. and the embedding time is 1 hour.

8. The method for removing the fishy smell of enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In the step S2, when cyclodextrin is added to the enzymatic solution for embedding, the pH of the enzymatic solution is adjusted to 6.5-7.

0.

9. The method for removing the fishy smell of enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In step S2, the centrifugal speed is 4000 r / min and the centrifugal time is 15 min; in step S4, the centrifugal speed is 3000 r / min and the centrifugal time is 30 min.

10. The method for removing the fishy smell of enzymatically hydrolyzed oyster juice according to claim 1, characterized in that: In the step S4, the fermented enzymatic supernatant is kept warm at 105° C. for 6 hours.

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