Laochou sauce and method for preparing the same

Abstract

This invention relates to a dark soy sauce and its preparation method. The preparation method includes: mixing compressed air, caramel color, and clarified soy sauce to prepare a gas-liquid mixed colored soy sauce; and conducting a first heat preservation reaction on the colored soy sauce under sealed conditions at 56℃-66℃ to prepare a soy sauce intermediate; wherein, the time of the first heat preservation reaction is calculated by temperature integral, and the reaction constant y is calculated as follows: y = 0.048e 0.110x Where x is the real-time reaction temperature, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on x. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1500-1700. A second heat preservation reaction is then carried out on the soy sauce intermediate at 40℃-55℃ under non-sealed conditions with compressed air introduced for 10-28 hours. This method can reduce the bitterness of dark soy sauce while also enhancing its flavor and texture.

Description

Technical Field

[0001] This invention relates to the field of condiment technology, and in particular to a dark soy sauce and its preparation method. Background Technology

[0002] Dark soy sauce is a high-salt, liquid-state fermented soy sauce, suitable for coloring, and often uses caramel coloring as a raw material. During the preparation of caramel coloring, caramelization and Maillard reactions mainly occur, producing bitter substances. This results in a certain bitterness in dark soy sauce products containing caramel coloring, reducing the product's flavor appeal. Therefore, it is necessary to find a method to remove bitterness from dark soy sauce and improve its flavor appeal. Summary of the Invention

[0003] Therefore, the purpose of this invention is to provide a method that can reduce the bitterness of dark soy sauce while also improving its flavor and taste.

[0004] The technical solution is as follows:

[0005] A method for preparing dark soy sauce includes the following steps:

[0006] Compressed air, caramel coloring, and clarified soy sauce are mixed to prepare a gas-liquid mixture for coloring soy sauce;

[0007] The coloring soy sauce was subjected to a first heat preservation reaction at a temperature of 56℃-66℃ under sealed conditions to prepare a soy sauce intermediate.

[0008] The time for the first heat preservation reaction is calculated by integrating the temperature, and the reaction constant y is calculated as follows:

[0009] y = 0.048e 0.110x

[0010] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on x. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1500-1700.

[0011] The soy sauce intermediate was subjected to a second heat preservation reaction for 10-28 hours at a temperature of 40℃-55℃ and under non-sealed conditions with compressed air introduced.

[0012] In one embodiment, the total volume of the caramel color and the clarified soy sauce is 100m³. 3 The volume of the compressed air is calculated to be 2m³. 3 -16m 3 The compressed air has a volumetric oxygen content of 20%-22%.

[0013] In one embodiment, the volume percentage of the caramel color to the clarified soy sauce in the liquid is (25%-45%):(75%-55%).

[0014] In one embodiment, the pH of the coloring soy sauce is 5.1-5.6.

[0015] In one embodiment, the temperature of the second heat preservation reaction is 40°C-50°C.

[0016] In one embodiment, the second heat preservation reaction takes 12-24 hours.

[0017] In one embodiment, during the second heat preservation reaction, the flow rate of the compressed air is 10 m³ / s. 3 / h-20m 3 / h, the introduction time is 2h-4h, and the volumetric oxygen content of the compressed air is 20%-22%.

[0018] In one embodiment, the method for preparing the caramel color includes the following steps:

[0019] Caramel color precursor is prepared by caramelizing at least one of granulated sugar and starch sugar;

[0020] The caramel color precursor is mixed with food-grade alkali to prepare caramel color, wherein the pH of the caramel color is 5.5-6.0.

[0021] In one embodiment, the food-grade alkali is a mixture of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0022] In one embodiment, the clarified soy sauce is produced by a high-salt dilute state process.

[0023] In one embodiment, the method for preparing the clarified soy sauce includes the following steps:

[0024] Soybeans are crushed and cooked to obtain intermediate soybean materials;

[0025] Wheat is roasted and crushed to obtain intermediate wheat material;

[0026] The soybean intermediate material is mixed with the wheat intermediate material to prepare the raw material for fermentation.

[0027] The raw materials to be fermented are mixed with koji to make koji;

[0028] The Daqu (a type of starter culture) is mixed with salt and water and fermented to prepare a fermentation liquid;

[0029] The fermentation broth is subjected to oil extraction to prepare soy sauce stock solution;

[0030] The soy sauce stock solution is clarified to prepare clarified soy sauce.

[0031] In one embodiment, the mass percentage of the soybean intermediate to the wheat intermediate is (50%-70%):(30%-50%).

[0032] In one embodiment, the moisture content of the soybean intermediate is 40wt%-55wt%.

[0033] In one embodiment, the conditions for koji making include:

[0034] The mass ratio of the raw material to be fermented to the koji is 100:(0.3-0.6), and the koji-making temperature is 25℃-40℃ for 30h-60h.

[0035] In one embodiment, the mass ratio of the Daqu (a type of starter culture) to the saline solution is 1:(1.5-1.7), and the mass percentage concentration of the saline solution is 18%-22%.

[0036] In one embodiment, the fermentation conditions include:

[0037] The fermentation temperature is 30℃-40℃, and the time is 40d-60d.

[0038] In one embodiment, the clarification process includes the following steps:

[0039] The soy sauce stock solution is kept at 75℃-100℃ for 10h-30h, then cooled to 38℃-40℃, and centrifuged to obtain the clear liquid.

[0040] The present invention also provides a dark soy sauce, which is prepared according to the dark soy sauce preparation method described above.

[0041] In one embodiment, the content of amino acid nitrogen in the dark soy sauce is 0.4g / 100mL-0.5g / 100mL.

[0042] In one embodiment, the total nitrogen content of the dark soy sauce is 0.8g / 100mL-1.2g / 100mL.

[0043] In one embodiment, the total acid content of the dark soy sauce is 2.0g / 100mL-2.40g / 100mL.

[0044] In one embodiment, the content of soluble non-salt solids in the dark soy sauce is 40g / 100mL-45g / 100mL.

[0045] In one embodiment, the relative density of the dark soy sauce is 1.25-1.35g.

[0046] In one embodiment, the color of the dark soy sauce is 6000EBC-6800EBC.

[0047] In one embodiment, the viscosity of the dark soy sauce is 90cp / 25℃-100cp / 25℃.

[0048] In one embodiment, the red index of the dark soy sauce is 6.1-6.4.

[0049] In one embodiment, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 420 ppm.

[0050] In one embodiment, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 300 ppm.

[0051] The present invention has at least the following beneficial effects:

[0052] The method for preparing dark soy sauce provided by this invention mainly includes mixing caramel color, clarified soy sauce, and compressed air to prepare coloring soy sauce, followed by a first heat preservation reaction at 56℃-66℃ under sealed conditions, and a second heat preservation reaction under non-sealed conditions. The compressed air contains oxygen, and during the micro-oxygen and first heat preservation reaction (thermal reaction), the bitter substance 5-hydroxymethylfurfural undergoes degradation and oxidation, reducing its content and thus lowering bitterness. Furthermore, the reaction degree is precisely controlled using temperature integral to ensure stable bitterness reduction. Simultaneously, the oxidation of aldehydes produces organic acids and other products, which can mask bitterness to some extent, reducing the bitterness of the dark soy sauce product and enhancing its flavor. This eliminates the need for additional bitterness masking agents, avoiding their adverse effects on the product. Conducting a second heat treatment at 40℃-55℃ promotes the Maillard reaction in the system, enhancing the flavor and aroma intensity. Furthermore, this second heat treatment is carried out under non-sealed conditions (such as in an open container) and with compressed air introduced. During the thermal reaction, moisture evaporates, and volatile bitter substances such as furfural are removed, further strengthening the bitterness removal effect and improving the product's flavor and taste. In addition, this method has a relatively simple process flow, reducing production costs. Attached Figure Description

[0053] Figure 1 This is a flowchart illustrating a method for preparing dark soy sauce according to an embodiment of the present invention. Detailed Implementation

[0054] The present invention will be further described in detail below with reference to specific embodiments. The present invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of the present invention.

[0055] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0056] The terms "preferred," "more preferably," etc., used in this invention refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of this invention.

[0057] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0058] When using “including,” “having,” and “contains” as described herein, the intention is to cover non-exclusive inclusion, unless an explicit qualifying term such as “only,” “consisting of,” etc., is used, in which case another component may be added.

[0059] In this invention, the terms "preferredly," "more preferably," "better," and "even better" refer to embodiments of the invention that provide certain beneficial effects under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the description of one or more preferred embodiments does not imply that other embodiments are unavailable, nor is it intended to exclude other embodiments from the scope of the invention. That is, in this invention, "preferredly," "more preferably," "better," and "even better" are merely descriptions of more effective implementations or examples, but do not constitute a limitation on the scope of protection of the invention.

[0060] In this invention, terms such as "further," "even more," and "particularly" are used for descriptive purposes and to indicate differences in content, but should not be construed as limiting the scope of protection of this invention.

[0061] In this invention, "at least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two layers, three layers, etc., unless otherwise explicitly specified. In the description of this invention, "several" means at least one, such as one, two, etc., unless otherwise explicitly specified.

[0062] Unless otherwise specified, all steps of this invention may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0063] Unless otherwise stated, a singular term may include a plural term and should not be understood as having a quantity of one.

[0064] In this invention, "above" or "below" both include the number itself. For example, "below 1" includes 1.

[0065] In this invention, clarified soy sauce refers to a product obtained through a soy sauce clarification process, which has the same meaning as commonly understood by those skilled in the art, and can also be further optimized through the process.

[0066] There are two main types of fermented soy sauce processes: traditional low-salt solid-state fermentation and high-salt liquid-state fermentation. High-salt liquid-state fermented soy sauce inherits traditional Chinese fermentation techniques, using soybeans or defatted soybeans, wheat or wheat flour as raw materials. After steaming and cooking, and with the addition of Aspergillus oryzae to make koji (fermentation starter), the mixture is combined with brine to form a thin mash, which is then fermented. The fermentation period is generally 4-6 months, resulting in high-quality products with abundant aroma components and rich nutrients. High-salt liquid-state fermentation has many advantages that low-salt solid-state fermentation cannot match, such as a more pronounced ester aroma and a more delicious taste. High-salt liquid-state fermented soy sauce is made from soybeans / or defatted soybeans, wheat and / or wheat flour as raw materials. After steaming and cooking, and with the addition of Aspergillus oryzae to make koji, the mixture is combined with brine to form a thin mash, which is then fermented.

[0067] In this invention, the high-salt dilute state process has the same meaning as commonly understood by those skilled in the art, and the process can be further improved or optimized.

[0068] The Maillard reaction, also known as non-enzymatic browning, is a widespread non-enzymatic browning process in the food industry. It is a reaction between carbonyl compounds (reducing sugars) and amino compounds (amino acids and proteins), ultimately producing brown or even black macromolecular substances called melanoidins or pseudomelanins through a complex process; hence, it is also called the carbonyl-amine reaction (proposed by the French chemist L.C. Maillard in 1912). Besides producing melanoidins, the reaction also generates reductones, aldehydes, and heterocyclic compounds, which are the main sources of color and flavor in food. Almost all foods containing carbonyl and amino groups will undergo the Maillard reaction under heating conditions, giving them unique flavor and color.

[0069] Dark soy sauce is a high-salt, dilute-state fermented soy sauce, suitable for coloring, and often uses caramel color as a raw material. The preparation of caramel color mainly involves caramelization and Maillard reactions. In these reactions, pentose dehydrates to produce furfural, and hexose dehydrates to produce 5-hydroxymethylfurfural (HMF) and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP). Both of these characteristic substances have a bitter taste, resulting in a certain bitterness in dark soy sauce products containing caramel color, reducing the product's flavor appeal. Therefore, it is necessary to find a technique to remove bitterness from dark soy sauce and improve its flavor appeal.

[0070] Traditional food bitterness removal techniques mainly fall into the following six categories:

[0071] (1) Adsorption method: Adsorption separation is carried out by activated carbon or resin, for example, a low bitterness soy sauce, a compound seasoning containing it and its preparation method have been reported. Low bitterness soy sauce is prepared by adding microporous activated carbon and plasma-modified activated carbon fiber to soy sauce to adsorb bitter substances. However, after adding activated carbon, separation operation is required to ensure that the adsorbed activated carbon does not flow into the final product. This increases the production steps, increases the processing cost and causes the final product to be mixed. At the same time, activated carbon will indiscriminately adsorb large molecules in soy sauce. For dark soy sauce, the pigment molecules that make it color will also be adsorbed, affecting the coloring effect. Therefore, this technology is not suitable for removing bitterness from dark soy sauce.

[0072] (2) Encapsulation method: bitter molecules are encapsulated and complexed by amylopectin or cyclodextrin. Although the bitterness removal effect is good and direct contact with bitter taste receptors is avoided, there is also the problem of encapsulating or complexing other components, which affects the flavor of the final product. Therefore, there are certain limitations in practical application.

[0073] (3) Enzymatic method: Enzymes are used to remove hydrophobic amino acids from peptides. For example, a method for preparing non-bitter soybean peptides by double enzyme hydrolysis has been reported. The double enzyme method can prepare low molecular weight non-bitter soybean peptide products. However, most enzymatic processes can only target the bitterness caused by hydrophobic amino acids, which is highly specific and has no significant effect on the bitterness caused by other chemical substances.

[0074] (4) Inhibit the formation of bitter substances: For example, a method to reduce the bitterness of caramel color has been reported, which involves adding phenolic acid during the caramel color preparation process to inhibit the bitter substances generated during the reaction. However, the phenolic acid added by this method has a high market cost, which leads to an increase in production costs.

[0075] (5) Add bitter taste inhibitors: For example, a method has been reported to use isobutyl angelica to inhibit bitter substances from citrus fruits, coffee, tea and other bitter substances. However, bitter taste inhibitors have a certain specificity in inhibiting bitter substances. They generally only have a bitter taste inhibitory effect on one or a few bitter substances. Moreover, most bitter taste inhibitors have special flavors. Adding them will damage the original flavor of the food.

[0076] (6) Add other flavoring agents such as sweeteners to mask bitterness: For example, a method for masking the bitterness of soybean protein hydrolysate has been reported, which involves adding sucralose and anhydrous citric acid to mask the bitterness of soybean protein hydrolysate. However, the use of sweeteners will affect the original flavor of the food. In addition, although the bitterness is masked by sweeteners, the bitter substances are not eliminated and are still detected by taste receptors and recognized by the brain. The masking effect is unstable.

[0077] Based on this, the purpose of the present invention is to provide a method that can reduce the content of 5-hydroxymethylfurfural, reduce the bitterness of dark soy sauce, and at the same time improve the flavor and taste of dark soy sauce.

[0078] The technical solution is as follows:

[0079] A method for preparing dark soy sauce includes the following steps:

[0080] Compressed air, caramel coloring, and clarified soy sauce are mixed to prepare a gas-liquid mixture for coloring soy sauce;

[0081] The coloring soy sauce was subjected to a first heat preservation reaction at a temperature of 56℃-66℃ under sealed conditions to prepare a soy sauce intermediate.

[0082] The time for the first heat preservation reaction is calculated by integrating the temperature, and the reaction constant y is calculated as follows:

[0083] y = 0.048e 0.110x

[0084] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on x. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1500-1700.

[0085] The soy sauce intermediate was subjected to a second heat preservation reaction for 10-28 hours at a temperature of 40℃-55℃ and under non-sealed conditions with compressed air introduced.

[0086] 5-Hydroxymethylfurfural (5-HMF) is chemically reactive, sensitive to acids, alkalis, and oxidants, and is also heat-sensitive, readily undergoing polymerization or degradation reactions. When caramel color, clarified soy sauce, and compressed air are stirred, the dissolved oxygen in the system increases. During the micro-oxygen and high-temperature thermal reaction process, 5-HMF readily undergoes degradation and oxidation reactions, reducing its content and thus lowering bitterness. Furthermore, precise control of the reaction degree using temperature integral ensures stable bitterness reduction. Simultaneously, the oxidation of aldehydes produces organic acids and other products, which can mask bitterness to some extent, reducing the astringency of dark soy sauce products. A secondary thermal reaction at 40℃-55℃ after the initial thermal reaction simulates the traditional sun-drying process, promoting the Maillard reaction in the system and further increasing the content of other flavor compounds in the dark soy sauce, enhancing its taste and aroma, and ultimately improving product quality. Furthermore, the second heat treatment reaction is carried out under non-sealed conditions with compressed air introduced (such as in an open container). During the thermal reaction, the system's moisture evaporates, and volatile bitter substances such as furfural are also removed, further enhancing the debittering effect and improving product quality. In addition, this invention avoids the addition of exogenous substances such as bitterness masking agents, encapsulating complexes like cyclodextrin, and sweeteners, preventing these substances from affecting the product's flavor. The process is also relatively simple, avoiding the separation and impurity removal steps required for activated carbon adsorption debittering methods, thus reducing production costs and avoiding the risk of contamination due to incomplete adsorption separation.

[0087] The preparation method of the dark soy sauce of the present invention will be described in further detail below through step-by-step description.

[0088] S100: Prepares a gas-liquid mixed coloring soy sauce by mixing compressed air, caramel color, and clarified soy sauce.

[0089] In one embodiment, the process of mixing compressed air, caramel color, and clarified soy sauce to prepare a gas-liquid mixed coloring soy sauce includes the following steps:

[0090] S1001 mixes caramel coloring with clarified soy sauce to prepare a liquid mixture;

[0091] S1002 Compressed air is introduced into the liquid mixture to prepare a gas-liquid mixed coloring soy sauce.

[0092] Furthermore, in one embodiment, the step of mixing compressed air, caramel color, and clarified soy sauce to prepare a gas-liquid mixed coloring soy sauce includes the following steps:

[0093] S10011 is used to prepare caramel color;

[0094] S10012 Prepares Clarified Soy Sauce;

[0095] S10013 The caramel color is mixed with clarified soy sauce to prepare a liquid mixture;

[0096] S1002 Compressed air is introduced into the liquid mixture to prepare a gas-liquid mixed coloring soy sauce.

[0097] S10011 is used to prepare caramel color:

[0098] In one embodiment, the method for preparing the caramel color includes the following steps:

[0099] Caramel color precursor is prepared by caramelizing at least one of granulated sugar and starch sugar;

[0100] The caramel color precursor is mixed with food-grade alkali to prepare caramel color, wherein the pH of the caramel color is 5.5-6.0.

[0101] In one embodiment, citric acid was also added during the coking process.

[0102] In one embodiment, the coking temperature is 110℃-180℃, the pressure is 0MPa-0.10MPa, and the time is 60min-300min. Preferably, the coking temperature is 120℃-160℃, the pressure is 0.05MPa-0.10MPa, and the time is 90min-200min.

[0103] In one embodiment, the food-grade alkali is a mixture of sodium hydroxide, sodium carbonate, and sodium bicarbonate.

[0104] In one embodiment, after the step of mixing the caramel color precursor with food-grade alkali to prepare caramel color with a pH of 5.5-6.0, a cooling and filtering step is also included.

[0105] Further, the cooling process includes cooling the pH-adjusted caramel color to 50°C-55°C at 0 MPa.

[0106] Furthermore, the filtration process includes: the cooled caramel coloring is filtered through a 60-mesh filter bag and then set aside for use.

[0107] In one embodiment, the caramel color has a color rate of 10000EBC-12000EBC.

[0108] S10012 Preparation of Clarified Soy Sauce:

[0109] In one embodiment, the clarified soy sauce is produced by a high-salt dilute state process.

[0110] In one embodiment, the method for preparing the clarified soy sauce includes the following steps:

[0111] Soybeans are crushed and cooked to obtain intermediate soybean materials;

[0112] Wheat is roasted and crushed to obtain intermediate wheat material;

[0113] The soybean intermediate material is mixed with the wheat intermediate material to prepare the raw material for fermentation.

[0114] The raw materials to be fermented are mixed with koji to make koji;

[0115] The Daqu (a type of starter culture) is mixed with salt and water and fermented to prepare a fermentation liquid;

[0116] The fermentation broth is subjected to oil extraction to prepare soy sauce stock solution;

[0117] The soy sauce stock solution is clarified to prepare clarified soy sauce.

[0118] In this invention, cooked beans refer to beans that are not undercooked, do not peel, do not clump together, have a uniform softness and hardness, and are intact.

[0119] Understandably, in one embodiment, before the step of steaming and cooking the soybeans to prepare soybean intermediate material, the process includes steps of removing impurities, removing stones, color sorting, and washing the soybeans. This helps to remove most of the impurities, reduce the impact of impurities on the subsequent fermentation process, and further improve the sensory and safety and hygiene quality of the fermented soybeans.

[0120] In one embodiment, the moisture content of the soybean intermediate is 40wt%-55%.

[0121] In one embodiment, the mass percentage of the soybean intermediate material to the wheat intermediate material is (50%-70%):(30%-50%), including but not limited to 50%:50%, 55%:45%, 60%:40%, 65%:35%, or 70%:30%.

[0122] In one embodiment, the conditions for koji making include:

[0123] The mass ratio of the raw material to be fermented to the koji is 100:(0.3-0.6), the koji-making temperature is 25℃-40℃, and the time is 30h-60h.

[0124] In one embodiment, the mass ratio of the Daqu (a type of starter culture) to the saline solution is 1:(1.5-1.7), and the mass percentage concentration of the saline solution is 18%-22%.

[0125] In one embodiment, the fermentation conditions include:

[0126] The fermentation temperature is 30℃-40℃, and the time is 40d-60d.

[0127] In one embodiment, the clarification process includes the following steps:

[0128] The soy sauce stock solution is kept at 75℃-100℃ for 10h-30h, then cooled to 38℃-40℃, and centrifuged to obtain the clear liquid.

[0129] S1001 / S10013 mixes the caramel color with clarified soy sauce to prepare a liquid mixture.

[0130] In one embodiment, the volume percentage of the caramel color to the clarified soy sauce is (25%-45%):(75%-55%), including but not limited to 25%:75%, 30%:70%, 35%:65%, 40%:60%, or 45%:55%.

[0131] S1002 Compressed air is introduced into the liquid mixture to prepare a gas-liquid mixed coloring soy sauce.

[0132] In one embodiment, the total volume of the caramel color and the clarified soy sauce is 100m³. 3 The volume of the compressed air is calculated to be 2m³. 3 -16m 3 The compressed air contains 20%-22% oxygen by volume. Too much oxygen may cause excessive oxidation of the system, resulting in a decrease in aroma intensity and a slightly unpleasant odor, thus reducing the liking of the material's aroma; while too little oxygen will weaken the debittering effect.

[0133] Understandably, the total volume of the caramel color and the clarified soy sauce is 100m³. 3 The volume of the compressed air is calculated to be 2m³. 3 -8m 3 including but not limited to 2m 3 3m 3 4m 3 5m 3 6m 3 7m3 7.5m 3 8m 3 9m 3 10m 3 11m 3 12m 3 13m 3 14m 3 15m 3 or 16m 3 Furthermore, the compressed air has a volumetric oxygen content of 20%-22%, including but not limited to 20%, 21%, or 22%.

[0134] In one embodiment, in the step of preparing a gas-liquid mixed coloring soy sauce by introducing compressed air into the liquid mixture, the compressed air acts as both a reactant and agitates the materials.

[0135] Furthermore, the total volume of the caramel color and the clarified soy sauce is 100m³. 3 It is estimated that the volume of compressed air introduced per hour is 2m³. 3 -8m 3 The compressed air has a volumetric oxygen content of 20%-22%, and the stirring time is 1-2 hours.

[0136] In one embodiment, the pH of the coloring soy sauce is 5.1-5.6.

[0137] S200: The coloring soy sauce is subjected to a first heat preservation reaction at a temperature of 56℃-66℃ and under closed conditions to prepare a soy sauce intermediate;

[0138] The time for the first heat preservation reaction is calculated by integrating the temperature, and the reaction constant y is calculated as follows:

[0139] y = 0.048e 0.110x

[0140] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on x. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1500-1700.

[0141] Compressed air contains oxygen. During the initial heat treatment process (thermal reaction) in a slightly oxygenated environment, the bitter substance 5-hydroxymethylfurfural undergoes degradation and oxidation, reducing its content and thus lowering its bitterness. Furthermore, the reaction degree is precisely controlled using temperature integration to ensure stable bitterness reduction. Simultaneously, the oxidation of aldehydes produces organic acids and other products, which can mask bitterness to some extent, reducing the astringency of dark soy sauce products and enhancing their flavor. This eliminates the need for additional bitterness masking agents, avoiding their adverse effects on the product.

[0142] Understandably, the temperature of the first heat preservation reaction is 56℃-66℃, including but not limited to 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃, 65℃, or 66℃. If the temperature of the first heat preservation reaction exceeds 66℃, the aroma intensity of the dark soy sauce increases, but the burnt aroma becomes stronger, and the bitterness intensifies; if the temperature is below 56℃, the aroma intensity of the dark soy sauce weakens, and the bitterness-removing effect is reduced. Controlling the temperature of the first heat preservation reaction to 56℃-66℃ achieves both good aroma intensity and a good bitterness-removing effect.

[0143] In this invention, the real-time temperature of the system refers to the actual temperature at the detection time point. For example, starting from 0h, after 1h, the actual temperature of the system is counted as the temperature of 1h, and after another 1h, the actual temperature of the system is counted as the temperature of 2h.

[0144] S300 performs a second heat preservation reaction on the soy sauce intermediate for 10-28 hours under non-sealed conditions with a temperature of 40℃-55℃ and compressed air introduced.

[0145] A second heat treatment at 40℃-55℃ for 10-28 hours simulates traditional sun-drying, promoting the Maillard reaction in the system and further increasing the content of other flavor compounds in dark soy sauce. This enhances the taste and aroma, thus improving product quality. Furthermore, the second heat treatment is conducted under non-sealed conditions with compressed air (such as in an open container). This micro-oxygen environment accelerates the oxidation and decomposition of bitter substances like furfural. During the thermal reaction, the evaporation of moisture also removes volatile bitter substances like furfural, further strengthening the debittering effect and mimicking the evaporation process of traditional sun-drying, resulting in a flavor closer to traditional methods and improved product quality.

[0146] Understandably, the temperature of the second heat preservation reaction is 40℃-55℃, including but not limited to 40℃, 41℃, 42℃, 43℃, 44℃, 45℃, 46℃, 47℃, 48℃, 49℃, 50℃, 51℃, 52℃, 53℃, 54℃, or 55℃. Preferably, the temperature of the second heat preservation reaction is 40℃-50℃, which can achieve both good aroma intensity and better bitterness removal effect.

[0147] Understandably, the duration of the second heat preservation reaction is 10-28 hours, including but not limited to 10 hours, 12 hours, 14 hours, 16 hours, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, or 28 hours. Preferably, the duration of the second heat preservation reaction is 12-24 hours, which can achieve both good aroma intensity and better bitterness removal effect.

[0148] In one embodiment, during the second heat preservation reaction, the flow rate of the compressed air is 10 m³ / s. 3 / h-20m 3 The compressed air is supplied at a rate of / h for 2-4 hours, with a volumetric oxygen content of 20%-22%. Understandably, the compressed air flow rate includes, but is not limited to, 10 m³ / h. 3 / h、12m 3 / h, 14m 3 / h, 15m 3 / h、18m 3 / h or 20m 3 / h; the compressed air introduction time is including but not limited to 2h, 2.5h, 3h, 3.5h or 4h; the volumetric oxygen content of the compressed air is 20%-22%, including but not limited to 20%, 21% or 22%.

[0149] In one embodiment, compressed air is introduced simultaneously with the start of the second heat preservation reaction.

[0150] Figure 1 This is a flowchart illustrating a method for preparing dark soy sauce according to an embodiment of the present invention.

[0151] This invention also provides a dark soy sauce, which is prepared according to the method described above. The dark soy sauce prepared according to this method has the following characteristics: its amino acid nitrogen content meets the requirements of the National Food Safety Standard for Food; its total nitrogen and soluble non-salt solids meet the requirements of GB18186-2000 for brewed soy sauce; its total acidity meets the requirements of GB12456-2021 for food; and its bitter substance content meets the requirements of GBT18932.18-2003.

[0152] In one embodiment, the content of amino acid nitrogen in the dark soy sauce is 0.4g / 100mL-0.5g / 100mL.

[0153] In one embodiment, the total nitrogen content of the dark soy sauce is 0.8g / 100mL-1.2g / 100mL.

[0154] In one embodiment, the total acid content of the dark soy sauce is 2.0g / 100mL-2.40g / 100mL.

[0155] In one embodiment, the content of soluble non-salt solids in the dark soy sauce is 40g / 100mL-45g / 100mL.

[0156] In one embodiment, the relative density of the dark soy sauce is 1.25-1.35g.

[0157] In one embodiment, the color of the dark soy sauce is 6000EBC-6800EBC.

[0158] In one embodiment, the viscosity of the dark soy sauce is 90cp / 25℃-100cp / 25℃.

[0159] In one embodiment, the red index of the dark soy sauce is 6.1-6.4.

[0160] In this invention, the content of 5-hydroxymethylfurfural was determined in accordance with GB / T 18932.18-2003.

[0161] In one embodiment, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 420 ppm. Further, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 300 ppm. Even further, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 200 ppm. Still further, the content of 5-hydroxymethylfurfural in the dark soy sauce is less than 150 ppm.

[0162] The present invention will be further described below with reference to specific embodiments.

[0163] (1) The determination of amino acid nitrogen shall be in accordance with GB5009.235-2016 National Food Safety Standard for the determination of amino acid nitrogen in food.

[0164] (2) The detection of total nitrogen and soluble non-salt solids shall be in accordance with GB18186-2000 brewed soy sauce.

[0165] (2) The total acidity was determined in accordance with GB12456-2021 National Food Safety Standard for the Determination of Total Acidity in Food.

[0166] (3) Absorbance: determined according to the method specified in Appendix A of GB1886.64-2015 National Food Safety Standard for Food Additives Caramel Color.

[0167] (4) Viscosity: The viscosity was measured using a BROOKFIEL DV-II viscometer under the following conditions: rotor No. 2, 100 rpm, 25℃.

[0168] Example 1:

[0169] This embodiment provides a dark soy sauce and its preparation method, as detailed below:

[0170] (1) Preparation of caramel color:

[0171] 1.1) Mixing: Add 30 kg of fructose syrup with a solid content of 70%-80% to a 50 L reactor. Add 28 g of citric acid solution with a concentration of 35 wt% to the reactor and stir until homogeneous.

[0172] 1.2) Reaction: The mixed materials were heated to 135℃ and reacted at 0-0.05MPa for 120min.

[0173] 1.3) pH adjustment: After the reaction is complete, the pH of the reaction product is adjusted to 5.5 using a 25wt% sodium hydroxide aqueous solution.

[0174] 1.4) Cooling: Cool the pH-adjusted caramel color to 50℃-55℃ at 0MPa.

[0175] 1.5) Filtration: The cooled caramel coloring is filtered through a 60-mesh filter bag and then set aside for use.

[0176] (2) Preparation of clarified soy sauce:

[0177] 2.1) Raw material processing: 1.0 part by weight of soybean raw material (dried soybean grains) is crushed and cooked to obtain 1.75 parts by weight of soybean intermediate material; 1.0 part by weight of wheat raw material (dried wheat) is roasted and crushed to obtain 0.92 parts by weight of wheat intermediate material; the soybean intermediate material and wheat intermediate material are mixed evenly at a weight ratio of 65%:35%.

[0178] 2.2) Koji making: Add koji evenly to the processed raw materials at a rate of 0.35 wt%, and then make koji at a temperature of 28℃-32℃ for 38-40 hours to obtain koji.

[0179] 2.3) Fermentation: Add brine (22wt%) to the Daqu at 1.5 times the mass of Daqu, place it in a fermentation tank for fermentation, the fermentation temperature is 38℃-40℃, and the fermentation time is 46-48 days.

[0180] 2.4) Extracting oil: After fermentation, drain the original soy sauce liquid from the bottom of the fermentation tank for later use.

[0181] 2.5) Heating and clarification: Heat the soy sauce stock solution to 92℃ and maintain for 10 hours. After cooling to 38℃-40℃, centrifuge at 4500 rpm to remove the precipitate and obtain clarified soy sauce.

[0182] (3) Preparation of coloring soy sauce:

[0183] 3.1) Place the caramel coloring in a storage tank and add the soy sauce liquid. The volume ratio of caramel coloring to clarified soy sauce is 30%:70%.

[0184] 3.2) The caramel color and the clarified soy sauce are mixed evenly to obtain the colored soy sauce, and the pH of the colored soy sauce is 5.1.

[0185] 3.3) Use compressed air for stirring, with a compressed air flow rate of 3 m³ / h. 3 / h, the volumetric oxygen content of the compressed air is 20%-22%, after stirring for 1 hour, the material is heated to 56℃ and pumped to the insulated tank for the next reaction.

[0186] (4) First heat preservation reaction:

[0187] The coloring soy sauce is pumped into a sealed, insulated storage tank and kept at 56℃ for a certain period of time. The reaction period is calculated by integrating the temperature, and the reaction constant y is calculated as follows:

[0188] y = 0.048e 0.110x

[0189] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on the real-time reaction temperature. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1500.

[0190] (5) Second heat preservation reaction:

[0191] The coloring soy sauce, after the first heat treatment, was cooled to 40°C and placed in an open container for a second heat treatment. The reaction time was 12 hours. At the beginning of the reaction, compressed air was introduced to stir and ensure the system was homogeneous and to promote moisture evaporation. The flow rate of the compressed air was 12 m³ / h. 3 The reaction was terminated when the oxygen content of the compressed air was 20%-22% by volume, the water content was reduced to 1.0% of the total mass before the reaction, and the air flow was 2h / h.

[0192] (6) Cooling;

[0193] The coloring soy sauce that had been used to terminate the reaction was pumped into a plate heat exchanger and cooled to room temperature. After blending, dark soy sauce was obtained. The test results are shown in Table 1 below.

[0194] Table 1: Physicochemical properties of dark soy sauce from Example 1

[0195]

[0196]

[0197] As shown in Table 1, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce, and the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, indicating that the bitterness removal effect is significant.

[0198] Comparative Example 1:

[0199] This comparative example examines the effect of whether or not compressed air is introduced during the blending process of the color-adjusting soy sauce on the sensory characteristics of the dark soy sauce. It is basically the same as Example 1, except that compressed air is introduced during the blending process of the color-adjusting soy sauce in Example 1, while compressed air is not introduced during the blending process of the color-adjusting soy sauce in Comparative Example 1.

[0200] (1) The reaction conditions are shown in Table 2 below:

[0201] Table 2

[0202]

[0203] (2) The physicochemical properties of dark soy sauce are shown in Table 3 below:

[0204] Table 3: Physicochemical properties of dark soy sauce from Example 1 and Comparative Example 1

[0205]

[0206]

[0207] As shown in Table 3, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce, and the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is lower than that of Comparative Example 1, indicating that the bitterness removal effect is significant.

[0208] (3) Flavor evaluation of the samples is shown in Table 4 below:

[0209] Table 4

[0210] Evaluation Dimensions Total number of evaluators Example 1 Comparative Example 1 Preferred ratio Aroma intensity 10 5 5 50％ Aroma preference 10 6 4 60％ Bitter taste 10 7 3 70％ Taste preference 10 7 3 70％

[0211] As shown in Table 4, the effect of removing bitterness from the sample is more obvious after passing oxygen-containing compressed air through the mixing step of coloring soy sauce.

[0212] Comparative Examples 2 to 3

[0213] Comparative Examples 2 and 3 investigated the effect of the temperature of the first heat preservation reaction on the sensory properties of dark soy sauce. They were basically the same as those in Example 1, except that the temperature of the first heat preservation reaction in Example 1 was 56°C, while the temperature of the first heat preservation reaction in Comparative Example 2 was 68°C, and the temperature of the first heat preservation reaction in Comparative Example 3 was 50°C.

[0214] (1) The reaction conditions are shown in Table 5 below:

[0215]

[0216]

[0217] Note: Temperature integral calculation is performed according to the formula in step 4 of Example 1.

[0218] (2) The physicochemical properties of dark soy sauce are shown in Table 6 below:

[0219] Table 6: Physicochemical properties of dark soy sauce from Example 1, Comparative Example 2, and Comparative Example 3

[0220]

[0221] As shown in Table 6, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is significantly lower than that of Comparative Example 2 and Comparative Example 3, indicating that the bitterness removal effect is significant.

[0222] (3) Flavor evaluation of the samples is shown in Tables 7 and 8 below:

[0223] Table 7

[0224]

[0225]

[0226] As shown in Table 7, when the temperature of the first heat treatment was increased from 56℃ to 68℃, the aroma intensity of the sample increased. However, the evaluators felt that the aroma had a strong burnt smell and was less appealing. At the same time, the bitterness of the taste increased after the temperature was increased.

[0227] Table 8

[0228] Evaluation Dimensions Total number of evaluators Example 1 Comparative Example 3 Preferred ratio Aroma intensity 10 7 3 70％ Aroma preference 10 7 3 70％ Bitter taste 10 7 4 70％ Taste preference 10 6 4 60％

[0229] As shown in Table 8, when the temperature of the first heat preservation reaction decreased from 56℃ to 50℃, the aroma intensity of the sample weakened, the taste of the evaluators was lower, and the effect of heat preservation to remove bitterness was weakened.

[0230] In summary, excessively high initial insulation temperatures can impart a burnt taste to the product and increase bitterness. Conversely, excessively low initial insulation temperatures can weaken the product's aroma and reduce its bitterness-removing effect. Based on actual test results, this invention sets the initial insulation temperature to 56℃-66℃.

[0231] Comparative Example 4:

[0232] Comparative Example 4 examines the sensory effects of open and closed tests on the second heat preservation reaction of dark soy sauce. It is basically the same as Example 1, except that the second heat preservation reaction in Example 1 was carried out in an open container, while Comparative Example 4 was carried out under closed conditions.

[0233] (1) The reaction conditions are shown in Table 9 below:

[0234] Table 9

[0235]

[0236] (2) The physicochemical properties of dark soy sauce are shown in Table 10 below:

[0237] Table 10: Physicochemical properties of dark soy sauce from Example 1 and Comparative Example 4

[0238]

[0239] As shown in Table 10, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is significantly lower than that in Comparative Example 4, indicating that the bitterness removal effect is significant.

[0240] (3) The flavor evaluation results of the samples are shown in Table 11 below:

[0241] Table 11

[0242] Evaluation Dimensions Total number of evaluators Example 1 Comparative Example 4 Preferred ratio Aroma intensity 10 5 5 50％ Aroma preference 10 7 3 70％ Bitter taste 10 7 3 70％ Taste preference 10 8 2 80％

[0243] As shown in Table 11, the product has better sensory characteristics when the second heat-insulated reaction vessel is open, with weaker bitterness, better taste, and better aroma.

[0244] Comparative Example 5:

[0245] Comparative Example 5 investigated the effect of the temperature of the second heat preservation reaction on the sensory properties of dark soy sauce. It was basically the same as Example 1, except that the temperature of the second heat preservation reaction in Example 1 was 40°C, while the temperature of the second heat preservation reaction in Comparative Example 5 was 35°C.

[0246] (1) The reaction conditions are shown in Table 12 below:

[0247] Table 12

[0248] Fourth group comparison Insulation temperature / ℃ Insulation time / h Example 1 40 12 Comparative Example 5 35 12

[0249] (2) The physicochemical properties of dark soy sauce are shown in Table 13 below:

[0250] Table 13: Physicochemical properties of dark soy sauce from Example 1 and Comparative Example 5

[0251]

[0252] As shown in Table 13, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is significantly lower than that of Comparative Example 5, indicating that the bitterness removal effect is significant.

[0253] (3) The flavor evaluation results of the samples are shown in Table 14 below:

[0254] Table 14

[0255]

[0256]

[0257] As shown in Table 14, when the temperature of the second heat preservation reaction decreased from 40℃ to 35℃, the aroma intensity and likability of the sample were low, and the second bitterness removal effect was significantly weakened, resulting in very low taste likability. Therefore, the temperature of the second heat preservation reaction should be set above 40℃.

[0258] Comparative Example 6:

[0259] Comparative Example 6 investigated the effect of the second heat preservation reaction time on the sensory properties of dark soy sauce. It was basically the same as Example 1, except that the second heat preservation reaction time in Example 1 was 12 hours, while the second heat preservation reaction time in Comparative Example 6 was 7 hours.

[0260] (1) The reaction conditions are shown in Table 15 below:

[0261] Table 15

[0262] Fifth group comparison Insulation temperature / ℃ Insulation time / h Example 1 40 12 Comparative Example 6 40 7

[0263] (2) The physicochemical properties of dark soy sauce are shown in Table 16 below:

[0264] Table 2: Physicochemical properties of dark soy sauce from Example 1 and Comparative Example 6

[0265]

[0266]

[0267] As shown in Table 16, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is significantly lower than that in Comparative Example 6, indicating that the bitterness removal effect is significant.

[0268] (3) The flavor evaluation results of the samples are shown in Table 17 below:

[0269] Table 17

[0270] Evaluation Dimensions Total number of evaluators Example 1 Comparative Example 6 Preferred ratio Aroma intensity 12 8 4 33％ Aroma preference 12 7 5 67％ Bitter taste 12 8 4 67％ Taste preference 12 9 3 75％

[0271] As shown in Table 17, when the second heat preservation time was reduced from 12 hours to 7 hours, the aroma intensity and palatability of the sample decreased. Furthermore, the second bitterness removal effect was not as good as in Example 1, resulting in lower taste preference. Therefore, the second heat preservation time was set to be more than 12 hours.

[0272] Comparative Example 7:

[0273] This comparative example is basically the same as Example 1, except that compressed air is introduced into the second heat preservation reaction process in Example 1, while compressed air is not introduced into the second heat preservation reaction process in Comparative Example 7.

[0274] (1) The reaction conditions are shown in Table 18 below:

[0275] Table 18

[0276] Sixth group comparison Should compressed air be introduced? <![CDATA[Ventilation flow rate m 3 / h]]> Ventilation time / h Example 1 yes 12 2 Comparative Example 7 no -- --

[0277] (2) The physicochemical properties of dark soy sauce are shown in Table 19 below:

[0278] Table 19: Physicochemical properties of dark soy sauce from Example 1 and Comparative Example 7

[0279]

[0280] As shown in Table 19, the dark soy sauce prepared in Example 1 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 130 ppm, which is significantly lower than that in Comparative Example 7, indicating that the bitterness removal effect is significant.

[0281] (3) Flavor evaluation of the samples is shown in Table 20 below:

[0282] Table 20

[0283] Evaluation Dimensions Total number of evaluators Example 1 Comparative Example 7 Preferred ratio Aroma intensity 10 7 3 70％ Aroma preference 10 6 4 60％ Bitter taste 10 7 3 70％ Taste preference 10 7 3 70％

[0284] As shown in Table 20, during the second heat preservation reaction, the aroma intensity, aroma preference, bitterness and taste preference of the sample were all better than those without compressed air during the second heat preservation reaction. This indicates that introducing compressed air during the second heat preservation reaction is beneficial to further enhance the bitterness removal effect and improve the aroma quality.

[0285] Example 2

[0286] Example 2 is basically the same as Example 1, except that the temperature of the second heat preservation reaction in Example 1 is 40°C, while the temperature of the second heat preservation reaction in Example 2 is 55°C.

[0287] (1) The reaction conditions are shown in Table 21 below:

[0288] Table 21

[0289] Seventh group comparison Insulation temperature / ℃ Insulation time / h Example 1 40 12 Example 2 55 12

[0290] (2) The physicochemical properties of dark soy sauce are shown in Table 22 below:

[0291] Table 22: Physicochemical properties of dark soy sauce from Examples 1 and 2

[0292]

[0293] (3) The flavor evaluation results of the samples are shown in Table 23 below:

[0294] Table 23

[0295]

[0296]

[0297] As shown in Table 23, when the second heat treatment temperature was increased from 40℃ to 55℃, the aroma intensity of the sample increased. However, the tasters reported a slightly burnt aroma, which reduced its acceptability. Furthermore, the second bitterness removal effect was not as good as in Example 1, resulting in a slightly lower taste preference. It is speculated that this might be because the sample at 55℃ had a higher HMF content, but also a higher degree of thermal reaction, leading to a greater increase in total acidity and a stronger sour taste. Some bitterness was suppressed by organic acids, resulting in a slightly better score. In conclusion, the optimal temperature for the second heat treatment reaction is 40℃-50℃.

[0298] Example 3:

[0299] Example 3 is basically the same as Example 1, except that the second heat preservation reaction time in Example 1 is 12 hours, while the second heat preservation reaction time in Example 3 is 28 hours.

[0300] (1) The reaction conditions are shown in Table 24 below:

[0301] Table 24

[0302] Group 8 comparison Second heat preservation reaction temperature / ℃ Insulation time / h Example 1 40 12 Example 3 40 28

[0303] (2) The physicochemical properties of dark soy sauce are shown in Table 25 below:

[0304] Table 25: Physicochemical properties of dark soy sauce from Examples 1 and 3

[0305]

[0306]

[0307] (3) The flavor evaluation results of the samples are shown in Table 26 below:

[0308] Table 26

[0309] Evaluation Dimensions Total number of evaluators Example 1 Example 3 Preferred ratio Aroma intensity 12 5 7 42％ Aroma preference 12 7 5 58％ Bitter taste 12 7 5 58％ Taste preference 12 7 5 58％

[0310] As shown in Table 26, extending the second incubation time from 12h to 28h increased the aroma intensity of the samples, but decreased their palatability. Simultaneously, the second bitterness removal effect was less than in Example 1, resulting in lower palatability. This is likely because although the 28h sample had a higher HMF content, the extended reaction time also led to a higher degree of thermal reaction and a greater increase in total acidity, resulting in a stronger sour taste. Some bitterness was suppressed by organic acids, leading to a slightly better score. In conclusion, the optimal time for the second incubation reaction is 12h-24h.

[0311] Example 4:

[0312] This embodiment provides a dark soy sauce and its preparation method, as detailed below:

[0313] (1) Preparation of caramel color:

[0314] 1.1) Mixing: Take 35 kg of a 77%-80% solids content white sugar aqueous solution and add it to a 50 L reactor. Add 30 g of a 37 wt% citric acid solution to the reactor and stir until homogeneous.

[0315] 1.2) Reaction: The mixed materials were heated to 145℃ and reacted at 0.05MPa-0.10MPa for 150min.

[0316] 1.3) pH adjustment: After the reaction is complete, the pH of the reaction product is adjusted to 5.8 using a 25wt% sodium hydroxide aqueous solution.

[0317] 1.4) Cooling: Cool the pH-adjusted caramel color to 50℃-55℃ at 0MPa.

[0318] 1.5) Filtration: The cooled caramel coloring is filtered through a 60-mesh filter bag and then set aside for use.

[0319] (2) Preparation of clarified soy sauce:

[0320] 2.1) Raw material processing: 1.0 part by weight of soybean raw material (dried soybean grains) is crushed and cooked to obtain 1.85 parts by weight of soybean intermediate material; 1.0 part by weight of wheat raw material (dried wheat) is roasted and crushed to obtain 0.93 parts by weight of wheat intermediate material; the soybean intermediate material and wheat intermediate material are mixed evenly at a weight ratio of 60%:40%.

[0321] 2.2) Koji making: Add koji evenly to the processed raw materials at a rate of 0.45 wt%, and then make koji at a temperature of 28℃-32℃ for 38-40 hours to obtain koji.

[0322] 2.3) Fermentation: Add brine (20wt%) to the Daqu at 1.7 times the mass of Daqu, place it in a fermentation tank for fermentation, the fermentation temperature is 32℃-34℃, and the fermentation time is 52-54 days.

[0323] 2.4) Extracting oil: After fermentation, drain the original soy sauce liquid from the bottom of the fermentation tank for later use.

[0324] 2.5) Heating clarification: Heat the soy sauce stock solution to 85℃ and maintain for 16 hours. After cooling to 38℃-40℃, centrifuge at 4500 rpm to remove the precipitate and obtain clarified soy sauce.

[0325] (3) Preparation of coloring soy sauce:

[0326] 3.1) Place the caramel coloring in a storage tank and add the clarified soy sauce. The volume ratio of caramel coloring to clarified soy sauce is 35%:65%.

[0327] 3.2) Mix caramel coloring and clarified soy sauce evenly to obtain colored soy sauce with a pH of 5.3.

[0328] 3.3) Use compressed air for stirring, with a compressed air flow rate of 5 m³ / h. 3 / h, with a volumetric oxygen content of 20%-22%, after stirring for 1.5h to achieve uniformity, heat the coloring soy sauce to 60℃-62℃ and pump it into a thermal tank for the next reaction.

[0329] (4) First heat preservation reaction:

[0330] The heated soy sauce is pumped into a sealed, insulated storage tank and kept at 60°C for a certain reaction period; the reaction period is calculated as an integral of temperature. The reaction constant y is calculated as follows:

[0331] y = 0.048e 0.110x

[0332] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on the real-time reaction temperature. n The temperature integral is ∑y n The heat preservation reaction is terminated when the temperature integral reaches 1600.

[0333] (5) Second heat preservation reaction:

[0334] The coloring soy sauce, after the first heat treatment, was cooled to 46°C and placed in an open container for a second heat treatment. The reaction period was 18 hours. At the beginning of the reaction, compressed air was introduced and stirred regularly to ensure the system was homogeneous and to promote moisture evaporation. The flow rate of the compressed air was 15 m³ / h. 3 The reaction was terminated after the volumetric oxygen content of the compressed air was 20%-22% at a rate of 1 / h, with the water content evaporating to 1.5% of the total mass before the reaction.

[0335] (6) Cooling;

[0336] The coloring soy sauce that had been used to terminate the reaction was pumped into a plate heat exchanger and cooled to room temperature. After blending, dark soy sauce was obtained. The test results are shown in Table 27 below.

[0337] Table 27: Physicochemical properties of dark soy sauce from Example 4

[0338]

[0339] As shown in Table 27, the dark soy sauce prepared in Example 4 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 100 ppm, which is lower than that of Comparative Examples 1 to 7, indicating that the bitterness removal effect is significant.

[0340] Example 5:

[0341] This embodiment provides a dark soy sauce and its preparation method, as detailed below:

[0342] (1) Preparation of caramel color:

[0343] 1.1) Mixing: Take 40 kg of a 77%-80% solids content white sugar aqueous solution and add it to a 50 L reactor. Add 35 g of a 39 wt% citric acid solution to the reactor and stir until homogeneous.

[0344] 1.2) Reaction: The mixed materials were heated to 155℃ and reacted at 0.05MPa-0.10MPa for 180min.

[0345] 1.3) pH adjustment: After the reaction is complete, the pH of the reaction product is adjusted to 6.0 using a 25wt% sodium hydroxide aqueous solution.

[0346] 1.4) Cooling: Cool the pH-adjusted caramel color to 50℃-55℃ at 0MPa.

[0347] 1.5) Filtration: The cooled caramel coloring is filtered through a 60-mesh filter bag and then set aside for use.

[0348] (2) Preparation of clarified soy sauce:

[0349] 2.1) Raw material processing: 1.0 part by weight of soybean raw material (dried soybean grains) was crushed and cooked to obtain 1.95 parts by weight of soybean intermediate material. 1.0 part by weight of wheat raw material (dried wheat) was roasted and crushed to obtain 0.94 parts by weight of wheat intermediate material. The soybean intermediate material and wheat intermediate material were mixed evenly at a weight ratio of 55%:45%.

[0350] 2.2) Koji making: Add koji evenly to the processed raw materials at a rate of 0.50 wt%, and then make koji at a temperature of 28℃-32℃ for 38-40 hours to obtain koji.

[0351] 2.3) Fermentation: Add brine (18wt%) to the Daqu at 1.6 times the mass of Daqu, place it in a fermentation tank for fermentation, the fermentation temperature is 36℃-38℃, and the fermentation time is 49-51 days.

[0352] 2.4) Extracting oil: After fermentation, drain the original soy sauce liquid from the bottom of the fermentation tank for later use.

[0353] 2.5) Heating and clarification: Heat the soy sauce stock solution to 80℃ and maintain for 22 hours. After cooling to 38℃-40℃, centrifuge at 4500 rpm to remove the precipitate and obtain clarified soy sauce.

[0354] (3) Preparation of coloring soy sauce:

[0355] 3.1) Place the caramel coloring in a storage tank and add the clarified soy sauce. The volume ratio of caramel coloring to clarified soy sauce is 40%:60%.

[0356] 3.2) Mix caramel coloring and clarified soy sauce evenly to obtain colored soy sauce with a pH of 5.4-5.5.

[0357] 3.3) Use compressed air for stirring, with a compressed air flow rate of 8 m³ / h. 3 / h, the volumetric oxygen content of the compressed air is 20%-22%, and the stirring time is 2h; after stirring evenly, the coloring soy sauce is heated to 63℃-65℃ and pumped to the heat preservation tank for the next reaction.

[0358] (4) First heat preservation reaction:

[0359] The heated coloring soy sauce is pumped into a sealed, insulated storage tank and kept at 66℃ for a certain period of time. The reaction period is calculated by integrating the temperature, and the reaction constant y is calculated as follows:

[0360] y = 0.048e 0.110x

[0361] Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on the real-time reaction temperature. n The temperature integral is ∑y n The first heat preservation reaction is terminated when the temperature integral reaches 1700.

[0362] (5) Second heat preservation reaction:

[0363] The coloring soy sauce, after the first heat treatment, was cooled to 50°C and placed in an open container for a second heat treatment. The reaction cycle was 24 hours. At the beginning of the reaction, compressed air was introduced to stir and ensure the system was homogeneous and to promote moisture evaporation. The flow rate of the compressed air was 20 m³ / h. 3 The reaction was terminated after the oxygen content of the compressed air was 20%-22% by volume, and the water content was reduced to 2.0% of the total mass before the reaction.

[0364] (6) Cooling;

[0365] The coloring soy sauce that had been used to terminate the reaction was pumped into a plate heat exchanger and cooled to room temperature. After blending, dark soy sauce was obtained. The test results are shown in Table 28 below.

[0366] Table 28: Physicochemical properties of dark soy sauce from Example 5

[0367]

[0368]

[0369] As shown in Table 28, the dark soy sauce prepared in Example 5 meets all the relevant regulations for dark soy sauce. Moreover, the content of the bitter substance 5-hydroxymethylfurfural is 70 ppm, which is significantly lower than that of Comparative Examples 1 to 7, indicating that the bitterness removal effect is significant.

[0370] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0371] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims.

Claims

1. A method for preparing dark soy sauce, characterized in that, Includes the following steps: Compressed air, caramel coloring, and clarified soy sauce are mixed to prepare a gas-liquid mixture for coloring soy sauce; The coloring soy sauce was subjected to a first heat preservation reaction at a temperature of 56℃-66℃ under sealed conditions to prepare a soy sauce intermediate. The time for the first heat preservation reaction is calculated by integrating the temperature, and the reaction constant y is calculated as follows: Where x is the real-time reaction temperature in °C, measured in hours, and the hourly reaction constants y1, y2, ... y are calculated based on x. n The temperature integral is The first heat preservation reaction is terminated when the temperature integral reaches 1500-1700. The soy sauce intermediate was subjected to a second heat preservation reaction for 10-28 hours at a temperature of 40℃-55℃ and under non-sealed conditions with compressed air introduced. In the step of preparing the gas-liquid mixed coloring soy sauce, the total volume of the caramel color and the clarified soy sauce is 100m³. 3 The volume of the compressed air is 2m³. 3 -16m 3 The compressed air has a volumetric oxygen content of 20%-22%; in the liquid of the coloring soy sauce, the volume percentage of the caramel color to the clarified soy sauce is (25%-45%):(75%-55%). During the second heat preservation reaction, the flow rate of the compressed air is 10 m³ / s. 3 / h-20m 3 / h, the introduction time is 2h-4h, and the volumetric oxygen content of the compressed air is 20%-22%.

2. The method for preparing dark soy sauce according to claim 1, characterized in that, In the step of preparing the gas-liquid mixed coloring soy sauce, the pH of the coloring soy sauce is 5.1-5.

6.

3. The method for preparing dark soy sauce according to claim 1, characterized in that, The second heat preservation reaction is carried out at a temperature of 40℃-50℃ for 12h-24h.

4. The method for preparing dark soy sauce according to any one of claims 1 to 3, characterized in that, The method for preparing the caramel color includes the following steps: Caramel color precursor is prepared by caramelizing at least one of granulated sugar and starch sugar; The caramel color precursor is mixed with food-grade alkali to prepare caramel color, wherein the pH of the caramel color is 5.5-6.

0.

5. The method for preparing dark soy sauce according to any one of claims 1 to 3, characterized in that, The clarified soy sauce is produced through a high-salt dilute state process.

6. The method for preparing dark soy sauce according to claim 5, characterized in that, The method for preparing the clarified soy sauce includes the following steps: Soybeans are crushed and cooked to obtain intermediate soybean materials; Wheat is roasted and crushed to obtain intermediate wheat material; The soybean intermediate material is mixed with the wheat intermediate material to prepare the raw material for fermentation. The raw materials to be fermented are mixed with koji to make koji; The Daqu (a type of starter culture) is mixed with salt water and fermented to prepare a fermentation liquid. The fermentation broth is subjected to oil extraction to prepare soy sauce stock solution; The soy sauce stock solution is clarified to prepare clarified soy sauce.

7. The method for preparing dark soy sauce according to claim 6, characterized in that, At least one of the following (1)-(2) must be satisfied: (1) The mass percentage of the soybean intermediate material to the wheat intermediate material is (50%-70%): (30%-50%). (2) The moisture content of the soybean intermediate material is 40wt%-55wt%.

8. The method for preparing dark soy sauce according to claim 6, characterized in that, At least one of the following (3)-(6) must be satisfied: (3) The conditions for making the koji include: The mass ratio of the raw material to be fermented to the koji is 100:(0.3-0.6), the koji-making temperature is 25℃-40℃, and the time is 30h-60h; (4) The mass ratio of the Daqu (a type of starter culture) to the saline solution is 1:(1.5-1.7), and the mass percentage concentration of the saline solution is 18%-22%. (5) The fermentation conditions include: The fermentation temperature is 30℃-40℃, and the time is 40d-60d; (6) The clarification process includes the following steps: The soy sauce stock solution is kept at 75℃-100℃ for 10h-30h, then cooled to 38℃-40℃, and centrifuged to obtain the clear liquid.

9. A dark soy sauce, characterized in that, The dark soy sauce is prepared according to any one of claims 1 to 8.

10. The dark soy sauce according to claim 9, characterized in that, Satisfy at least one of the following (7)-(15): (7) The content of amino acid nitrogen is 0.4g / 100mL-0.5g / 100mL; (8) The total nitrogen content is 0.8g / 100mL-1.2g / 100mL; (9) The total acid content is 2.0 g / 100 mL - 2.40 g / 100 mL; (10) The content of soluble salt-free solids is 40g / 100mL-45g / 100mL; (11) The relative density is 1.25-1.35 g; (12) The color rate is 6000EBC-6800EBC; (13) Viscosity is 90cp / 25℃-100cp / 25℃; (14) The red index is 6.1-6.4; (15) The content of 5-hydroxymethylfurfural is less than 420 ppm.

Images