A method for improving the quality of soy sauce

Abstract

This invention provides a method for improving the quality of soy sauce. The method includes: 1) providing cooked soy sauce; 2) purging the cooked soy sauce from step 1 with nitrogen for at least 12 days to improve its quality. Using this method, the quality of soy sauce can be improved.

Description

Technical Field

[0001] This invention relates to the field of soy sauce, and more particularly to a method for improving the quality of soy sauce. Background Technology

[0002] Improving soy sauce quality, especially its ammonia nitrogen level, has always been a hot topic in the soy sauce industry. Ammonia nitrogen is a crucial indicator of soy sauce quality. The production mechanism of soy sauce involves the hydrolysis of proteins and starches in the raw materials by microorganisms such as Aspergillus. Proteins are first hydrolyzed into peptones, then into polypeptides and amino acids. Starch undergoes a series of enzymatic hydrolysis processes, gradually breaking down into dextrins, maltose, and glucose. Ammonia nitrogen originates from the hydrolysis of proteins in the raw materials; therefore, under suitable protein hydrolysis conditions, the ammonia nitrogen content is high, and vice versa. Currently, increasing protein yield can improve ammonia nitrogen levels, but this requires trying many complex methods, such as selecting raw materials with high protein content, minimizing protein loss during raw material pretreatment, and optimizing koji-making and fermentation conditions. Even then, the results are not always significant. The complex fermentation conditions of soy sauce can affect ammonia nitrogen levels.

[0003] Among the sensory indicators of color, aroma, taste, and appearance in light soy sauce, color is the most intuitive. Color is undoubtedly one of the important indicators consumers consider when purchasing soy sauce, and it is also a crucial indicator of a soy sauce company's competitiveness. However, during storage, soy sauce color tends to gradually darken as shelf life extends, and this is an irreversible phenomenon. This affects the stability of the soy sauce, and its flavor compounds also change, thus impacting the consumer experience. The formation of soy sauce color mainly occurs through two pathways: the Maillard reaction and the enzymatic browning of polyphenols. Therefore, controlling the color of soy sauce during storage is an urgent problem that needs to be solved. Summary of the Invention

[0004] The inventors of this invention discovered that passing nitrogen gas through soy sauce for several days (especially by first passing oxygen gas for a certain period and then passing nitrogen gas) can increase the ammonia nitrogen level of the soy sauce. This does not affect the color of the soy sauce during long-term storage, ensuring its good quality. Nitrogen gas also inhibits surface oxidation of raw soy sauce, preventing discoloration and oxidative odor. The method in this invention can be applied to preservative-free products, simultaneously increasing ammonia nitrogen levels and protecting the color of soy sauce, demonstrating excellent application prospects.

[0005] Therefore, a first aspect of the present invention is to provide a method for improving the quality of soy sauce.

[0006] The method provided by this invention includes:

[0007] 1) Provide cooked soy sauce;

[0008] 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

[0009] In a preferred embodiment of the present invention, the ventilation is as follows:

[0010] 1) Purge with nitrogen for 12-28 days, or

[0011] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0012] In a preferred embodiment of the present invention, the aeration is 1-3L per minute for every 30L of soy sauce.

[0013] In a preferred embodiment of the present invention, the soy sauce quality is determined by ammonia nitrogen, color, taste, aroma, and / or body shape.

[0014] A second aspect of the present invention is to provide a method for preparing soy sauce.

[0015] The method provided by this invention includes:

[0016] 1) Provide cooked soy sauce;

[0017] 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

[0018] In a preferred embodiment of the present invention, the ventilation is as follows:

[0019] 1) Purge with nitrogen for 12-28 days, or

[0020] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0021] In a preferred embodiment of the present invention, the aeration is 1-3L per minute for every 30L of soy sauce.

[0022] In a preferred embodiment of the present invention, the soy sauce quality is determined by ammonia nitrogen, color, taste, aroma, and / or body shape.

[0023] A third aspect of the present invention is to provide a method for improving the quality of soy sauce by introducing nitrogen gas into it.

[0024] In a preferred embodiment of the present invention, the nitrogen purging is performed for more than 12 days.

[0025] In a preferred embodiment of the present invention, the nitrogen gas purging is:

[0026] 1) Purge with nitrogen for 12-28 days, or

[0027] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0028] In a preferred embodiment of the present invention, the nitrogen or oxygen gas is introduced at a rate of 1-3L per minute for every 30L of soy sauce.

[0029] In a preferred embodiment of the present invention, the soy sauce quality is determined by ammonia nitrogen, color, taste, aroma, and / or body shape. Detailed Implementation

[0030] Unless otherwise stated, the terms used in this application have the same meaning as commonly understood by those skilled in the art. For the various experimental techniques mentioned herein, those skilled in the art may refer to various textbooks, literature, and commercial product specifications, as well as the specific examples given in the Embodiments section of this application.

[0031] It should be understood that the term “about” as used herein (e.g., in component content and reaction parameters) is interpreted in the sense that would be commonly understood by those skilled in the art. Generally, the term “about” can be understood as any value within a range of plus or minus 5% of a given value; for example, about X can represent any value in the range of 95%X to 105%X.

[0032] It should also be understood that the specific numerical values ​​given herein (e.g., in component content, culture temperature, and culture time) should not only be understood as individual values, but also as providing endpoints of a range, and can be combined to provide other ranges. For example, when it is disclosed that the content of a component can be 1% or 5%, it is also equivalent to disclosing that its content can be from 1% to 5%.

[0033] The following describes some exemplary embodiments of this application in detail. It should be understood that these detailed descriptions are only intended to provide a clearer understanding of the content of this application to those skilled in the art, and are not intended to limit it in any way. Those skilled in the art can make various modifications and variations to the described embodiments.

[0034] The inventors of this invention discovered that passing nitrogen gas through soy sauce for several days (especially by first passing oxygen gas for a certain period and then passing nitrogen gas) can increase the ammonia nitrogen level of the soy sauce. This does not affect the color of the soy sauce during long-term storage, ensuring its good quality. Nitrogen gas also inhibits surface oxidation of raw soy sauce, preventing discoloration and oxidative odor. The method in this invention can be applied to preservative-free products, simultaneously increasing ammonia nitrogen levels and protecting the color of soy sauce, demonstrating excellent application prospects.

[0035] Therefore, a first aspect of the present invention is to provide a method for improving the quality of soy sauce.

[0036] The method provided by this invention includes:

[0037] 1) Provide cooked soy sauce;

[0038] 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

[0039] In this invention, the soy sauce used (also known as cooked oil, cooked soy sauce, etc.) can be obtained commercially or prepared by conventional methods in the art, for example, by the following method: inoculating a mixture of defatted soybeans and wheat with Aspergillus oryzae to make koji, mixing the soy sauce koji with brine and fermenting to obtain mature soy mash, lightly pressing the mature soy mash at 0.8 MPa for 20 h, then heavily pressing it at 5 MPa for 20 h, filtering with diatomaceous earth to obtain raw soy sauce, and then sterilizing it at 85°C to obtain cooked oil.

[0040] In this invention, the Aspergillus oryzae used can be a commercially available Aspergillus oryzae product, such as koji, Hu Niang 3.042, or an Aspergillus oryzae strain from a preservation institution or a screened Aspergillus oryzae strain, as long as it can be used to prepare koji in soy sauce.

[0041] In a preferred embodiment of the present invention, the ventilation is as follows:

[0042] 1) Purge with nitrogen for 12-28 days, or

[0043] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0044] In a preferred embodiment of the present invention, nitrogen is purged for 14-21 days, or for 12-16 days.

[0045] In a preferred embodiment of the invention, nitrogen gas is passed through for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0046] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 14-21 days, or nitrogen for 12-16 days.

[0047] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0048] In a preferred embodiment of the present invention, the aeration is 1-3L per minute for every 30L of soy sauce, for example, 1L, 2L or 3L.

[0049] In a preferred embodiment of the present invention, the quality of the soy sauce is defined by ammonia nitrogen content, color, flavor, aroma, and / or body. Specifically, increasing the ammonia nitrogen content can improve the color, aroma, flavor, and body of the soy sauce, and reduce color changes during long-term storage.

[0050] A second aspect of the present invention is to provide a method for preparing soy sauce.

[0051] The method provided by this invention includes:

[0052] 1) Provide cooked soy sauce;

[0053] 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

[0054] In this invention, the soy sauce used (also known as cooked oil, cooked soy sauce, etc.) can be obtained commercially or prepared by conventional methods in the art, for example, by the following method: inoculating a mixture of defatted soybeans and wheat with Aspergillus oryzae to make koji, mixing the soy sauce koji with brine and fermenting to obtain mature soy mash, lightly pressing the mature soy mash at 0.8 MPa for 20 h, then heavily pressing it at 5 MPa for 20 h, filtering with diatomaceous earth to obtain raw soy sauce, and then sterilizing it at 85°C to obtain cooked oil.

[0055] In this invention, the Aspergillus oryzae used can be a commercially available Aspergillus oryzae product, such as koji, Hu Niang 3.042, or an Aspergillus oryzae strain from a preservation institution or a screened Aspergillus oryzae strain, as long as it can be used to prepare koji in soy sauce.

[0056] In a preferred embodiment of the present invention, the ventilation is as follows:

[0057] 1) Purge with nitrogen for 12-28 days, or

[0058] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0059] In a preferred embodiment of the present invention, nitrogen is purged for 14-21 days, or for 12-16 days.

[0060] In a preferred embodiment of the invention, nitrogen gas is passed through for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0061] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 14-21 days, or nitrogen for 12-16 days.

[0062] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0063] In a preferred embodiment of the present invention, the aeration is 1-3L per minute for every 30L of soy sauce, for example, 1L, 2L or 3L.

[0064] In a preferred embodiment of the present invention, the quality of the soy sauce is defined by ammonia nitrogen content, color, flavor, aroma, and / or body. Specifically, increasing the ammonia nitrogen content can improve the color, aroma, flavor, and body of the soy sauce, and reduce color changes during long-term storage.

[0065] A third aspect of the present invention is to provide a method for improving the quality of soy sauce by introducing nitrogen gas into it.

[0066] In this invention, the soy sauce used (also known as cooked oil, cooked soy sauce, etc.) can be obtained commercially or prepared by conventional methods in the art, for example, by the following method: inoculating a mixture of defatted soybeans and wheat with Aspergillus oryzae to make koji, mixing the soy sauce koji with brine and fermenting to obtain mature soy mash, lightly pressing the mature soy mash at 0.8 MPa for 20 h, then heavily pressing it at 5 MPa for 20 h, filtering with diatomaceous earth to obtain raw soy sauce, and then sterilizing it at 85°C to obtain cooked oil.

[0067] In this invention, the Aspergillus oryzae used can be a commercially available Aspergillus oryzae product, such as koji, Hu Niang 3.042, or an Aspergillus oryzae strain from a preservation institution or a screened Aspergillus oryzae strain, as long as it can be used to prepare koji in soy sauce.

[0068] In a preferred embodiment of the present invention, the nitrogen purging is performed for more than 12 days.

[0069] In a preferred embodiment of the present invention, the nitrogen gas purging is:

[0070] 1) Purge with nitrogen for 12-28 days, or

[0071] 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

[0072] In a preferred embodiment of the present invention, nitrogen is purged for 14-21 days, or for 12-16 days.

[0073] In a preferred embodiment of the invention, nitrogen gas is passed through for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0074] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 14-21 days, or nitrogen for 12-16 days.

[0075] In a preferred embodiment of the present invention, oxygen is first introduced for 1, 2, or 3 days, followed by nitrogen for 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, or 28 days.

[0076] In a preferred embodiment of the present invention, the nitrogen or oxygen gas is introduced at a rate of 1-3L per minute per 30L of soy sauce, for example, 1L, 2L or 3L.

[0077] In a preferred embodiment of the present invention, the quality of the soy sauce is defined by ammonia nitrogen content, color, flavor, aroma, and / or body. Specifically, increasing the ammonia nitrogen content can improve the color, aroma, flavor, and body of the soy sauce, and reduce color changes during long-term storage.

[0078] The present invention has the following beneficial effects:

[0079] This invention provides a method for increasing the ammonia nitrogen level of soy sauce without complex operations, by introducing nitrogen gas into the air above the soy sauce to replace oxygen. This method also helps maintain the color of the soy sauce for a longer period and prevents a rapid decrease in the L* value during long-term shelf storage. Compared with existing technologies, this invention has the following advantages:

[0080] (1) The method provided by the present invention can improve the ammonia nitrogen level of soy sauce without complicated operation.

[0081] (2) The method provided by the present invention can ensure that the color of soy sauce will not continue to darken during long-term shelf storage, thus ensuring the color of soy sauce.

[0082] (3) The method provided by this invention conforms to people’s concept of zero corrosion and great health, and does not require preservatives and other chemicals, and has excellent application prospects.

[0083] The present invention will be further described below by way of specific embodiments. It should be understood that these embodiments are merely illustrative and are not intended to limit the scope of the invention. Unless otherwise stated, the methods and reagents used in the embodiments are conventional methods and reagents in the art.

[0084] In the following embodiments of the present invention, the detection method is as follows:

[0085] The detection of ammonia nitrogen was carried out in accordance with the national standard GB5009.235-2016 "National Food Safety Standard - Determination of Amino Acid Nitrogen in Food";

[0086] The detection of total acidity was performed in accordance with the national standard GB 18186-2000 "Brewn Soy Sauce";

[0087] Salt content was tested in accordance with the national standard GB 5009.44-2016, "National Food Safety Standard: Determination of Chloride in Food".

[0088] The change in color L* was detected using a desktop spectrophotometer (Shenzhen Sanenshi).

[0089] In the following embodiments of the present invention, the soy sauce used (also known as cooked oil, cooked soy sauce, etc.) can be prepared by conventional methods in the art, for example, by the following methods:

[0090] A mixture of defatted soybeans and wheat was inoculated with Aspergillus oryzae (the koji was purchased from Wenxian Qugao Biological Products Factory, product brand name Hu Niang 3.042) to make koji. The koji of soy sauce was mixed with brine and fermented to obtain mature soy mash. The mature soy mash was lightly pressed at 0.8 MPa for 20 hours, then heavily pressed at 5 MPa for 20 hours. The raw soy sauce was obtained by diatomaceous earth filtration. After sterilization at 85℃, cooked oil (also known as cooked soy sauce) was obtained.

[0091] Experiment: The effect of nitrogen or oxygen on the physicochemical properties of soy sauce

[0092] Example 1.1 Effect of continuous nitrogen flow for 28 days on the physicochemical properties of soy sauce (nitrogen flow rate 0.1 L / min)

[0093] Take 3L of soy sauce and add it to a 5L fermentation tank. Aeration with nitrogen at a rate of 0.1L / min is carried out continuously for 28 days. Samples are taken on the 7th, 14th, 21st and 28th days to detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 1.

[0094] Example 1.2 Effect of continuous nitrogen flow for 28 days on the physicochemical properties of soy sauce (nitrogen flow rate 0.2 L / min)

[0095] The ventilation rate was set to 0.2 L / min, and everything else was the same as in Example 1.1. The results are shown in Table 1.

[0096] Example 1.3 Effect of continuous nitrogen flow for 28 days on the physicochemical properties of soy sauce (nitrogen flow rate 0.3 L / min)

[0097] The ventilation rate was set to 0.3 L / min, and other parameters were the same as in Example 1.1. The results are shown in Table 1.

[0098] Example 1.4 Effect of continuous oxygen supply for 28 days on the physicochemical properties of soy sauce (nitrogen gas flow rate 0.1 L / min)

[0099] To evaluate the effect of oxygen ventilation on the physicochemical properties of soy sauce, oxygen was continuously circulated for 28 days, with the ventilation rate set to 0.1 L / min. Other parameters were the same as in Example 1.1. The results are shown in Table 1.

[0100] Example 1.5 Effect of continuous oxygen supply for 28 days on the physicochemical properties of soy sauce (nitrogen gas flow rate 0.2 L / min)

[0101] The oxygen ventilation rate was set to 0.2 L / min, and everything else was the same as in Example 1.1. The results are shown in Table 1.

[0102] Example 1.6 Effect of continuous oxygen supply for 28 days on the physicochemical properties of soy sauce (nitrogen gas flow rate 0.3 L / min)

[0103] The oxygen ventilation rate was set to 0.3 L / min, and everything else was the same as in Example 1.1. The results are shown in Table 1.

[0104] Based on the results obtained in Examples 1.1-1.6 of Table 1, the effect of nitrogen and oxygen aeration rates of 0.2 L / min on soy sauce was better than other aeration rates. Therefore, subsequent experiments set the aeration rates of nitrogen and oxygen to 0.2 L / min. To investigate the effect of introducing oxygen and nitrogen together on the quality of soy sauce, the soy sauce was intermittently aerated with oxygen and nitrogen, and the number of days for oxygen and nitrogen aeration were explored.

[0105] Example 1.7 Effect of passing oxygen for 1 day followed by nitrogen for 12 days on the physicochemical properties of soy sauce

[0106] Take 3L of soy sauce and add it to a 5L fermentation tank. Aeration is carried out at a rate of 0.2L / min. First, oxygen is introduced for 1 day, and then nitrogen is introduced for 12 days. Samples are taken on the 2nd, 4th, 6th, 8th, 10th and 12th days after the oxygen is introduced and after the nitrogen is introduced. The ammonia nitrogen, salt content, pH and total acid content are measured. The results are shown in Table 2.

[0107] Example 1.8 Effect of purging oxygen for 2 days followed by nitrogen for 12 days on the physicochemical properties of soy sauce

[0108] Take 3L of soy sauce and add it to a 5L fermentation tank. Aerate for 2 days at a rate of 0.2L / min, then aerate for 12 days. Take samples on the 2nd, 4th, 6th, 8th, 10th, 12th and 14th days after the oxygen is exhausted and on the nitrogen day. Detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 2.

[0109] Example 1.9 Effect of passing oxygen for 3 days followed by nitrogen for 12 days on the physicochemical properties of soy sauce

[0110] Take 3L of soy sauce and add it to a 5L fermentation tank. Aerate for 3 days at a rate of 0.2L / min, then aerate for 12 days. Take samples on the 2nd, 4th, 6th, 8th, 10th, 12th and 14th days after the oxygen is exhausted and on the nitrogen day. Detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 2.

[0111] Based on the experimental results of Examples 1.7-1.9 in Table 2, the soy sauce obtained by ventilating with oxygen for 2 days was of better quality than that obtained under other conditions. Therefore, the number of days of oxygen ventilation was fixed at 2 days to evaluate the effect of the number of days of nitrogen ventilation on the quality of soy sauce.

[0112] Example 1.10: Effect of purging with oxygen for 2 days followed by nitrogen for 10 days on the physicochemical properties of soy sauce.

[0113] Take 3L of soy sauce and add it to a 5L fermentation tank. Aerate for 2 days with an aeration rate of 0.2L / min, then aerate for 10 days with nitrogen. Take samples on the 2nd, 4th, 6th, 8th and 10th days after the oxygen is exhausted and on the 10th day after the nitrogen is introduced. Detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 2.

[0114] Example 1.11 Effect of passing oxygen for 2 days followed by nitrogen for 12 days on the physicochemical properties of soy sauce

[0115] Take 3L of soy sauce and add it to a 5L fermentation tank. Aerate for 2 days at a rate of 0.2L / min, then aerate for 12 days. Take samples on the 2nd, 4th, 6th, 8th, 10th and 12th days after the oxygen is purged and on the nitrogen purging days. Detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 2.

[0116] Example 1.12 Effect of passing oxygen for 2 days followed by nitrogen for 14 days on the physicochemical properties of soy sauce

[0117] Take 3L of soy sauce and add it to a 5L fermentation tank. Aerate for 2 days at a rate of 0.2L / min, then aerate for 14 days. Take samples on the 2nd, 4th, 6th, 8th, 10th, 12th and 14th days after the oxygen is exhausted and on the nitrogen day. Detect ammonia nitrogen, salt content, pH and total acid content. The results are shown in Table 2.

[0118] Example 1.13 Effects of intermittent oxygen and nitrogen purging on the color of soy sauce during long-term preservation

[0119] Based on the results in Tables 1 and 2, passing oxygen for 2 days followed by nitrogen for 12 days at a rate of 0.2 L / min can effectively improve the quality of soy sauce. Therefore, under these conditions, in order to evaluate the effect of this condition on the color stability of soy sauce stored on shelves for a long time, the soy sauce was sealed and stored for 6 months. Samples were taken each month to test the changes in ammonia nitrogen, total acid, salt, pH, and L* value. Other conditions were the same as in Example 1.1. The results are shown in Table 3.

[0120] Comparative Example 1.1 Effect of Lack of Ventilation on Physicochemical Properties of Soy Sauce

[0121] Compared with Examples 1.1-1.6, a control group without gas was designed. No gas was introduced and the control group was left to stand under the same conditions as in Example 1.1. The results are shown in Table 1.

[0122] Comparative Example 1.2: Effects of nitrogen purging for 2 days followed by oxygen purging on the physicochemical properties of soy sauce.

[0123] Compared with Examples 1.7-1.12, a control group was designed with nitrogen gas for 2 days followed by oxygen gas for 12 days, under the same conditions as Example 1.7. The results are shown in Table 2.

[0124] Comparative Example 1.3 Effects of intermittent oxygen and nitrogen purging on the color of soy sauce during long-term preservation

[0125] As a control of Example 1.13, the soy sauce was first purged with nitrogen for 2 days, then with oxygen for 12 days at a rate of 0.2 L / min, and sealed for 6 months. Samples were taken each month to test the changes in ammonia nitrogen, total acid, salt, pH, and L* value of the soy sauce. Other parameters were the same as in Example 1.1. The results are shown in Table 3.

[0126] Results and Discussion

[0127] To investigate the effects of different nitrogen and oxygen aeration rates on the physicochemical properties of soy sauce, aeration rates of 0.1-0.3 L / min were set, and the physicochemical properties (ammonia nitrogen, total acid, salt, and pH) of soy sauces that were continuously aerated for 28 days and continuously aerated for 28 days were measured. The results are shown in Table 1. The initial soy sauce sample had a pH of 4.39, a salt content of 14.05 g / 100 g, a total acid content of 1.69 g / 100 g, and an ammonia nitrogen content of 1.0266 g / 100 g. Compared with Examples 1.5-1.6, Examples 1.1-1.3 were experimental groups with continuous nitrogen purging. The results showed that continuous nitrogen purging can effectively increase the ammonia nitrogen level of soy sauce. Based on the sampling results at different time periods, the ammonia nitrogen level after 7 days of nitrogen purging was 12% higher than that of the soy sauce sample that had just been added. The ammonia nitrogen level on the 12th day of nitrogen purging was 1.6% higher than that on the 7th day and 14% higher than that of the soy sauce sample that had just been added. The ammonia nitrogen level after 14 days of nitrogen purging was 4.4% higher than that on the 7th day and 17.5% higher than that of the soy sauce sample that had just been added. The ammonia nitrogen level was significantly improved after 14 days of nitrogen purging. The longer the nitrogen purging time, the more significant the increase in ammonia nitrogen level of soy sauce. Examples 1.1-1.3 show the results of different nitrogen aeration rates. The ammonia nitrogen level in soy sauce was higher when the nitrogen aeration rate was 0.2 L / min, which was better than the result at 0.1 L / min. However, there was no significant difference in the effect of nitrogen aeration rates of 0.2 L / min and 0.3 L / min on the ammonia nitrogen level of soy sauce. Examples 1.4-1.5 show the effect of continuous oxygen aeration on the physicochemical properties of soy sauce. With the extension of oxygen aeration time, the ammonia nitrogen level of soy sauce gradually decreased. There was no significant difference in the effect of different oxygen aeration rates on soy sauce, with the oxygen aeration rate of 0.2 L / min being slightly better than the other two groups. Comparative Example 1.1 is the control group without any gas aeration. Even when soy sauce was left to stand without any gas aeration, the ammonia nitrogen level also decreased over time. Compared with oxygen aeration, the rate of decrease in ammonia nitrogen in soy sauce without any gas aeration was slower.

[0128] Table 1. Effects of continuous nitrogen or oxygen purging on the physicochemical properties of soy sauce.

[0129]

[0130]

[0131] To further investigate the effects of nitrogen and oxygen purging on the physicochemical properties of soy sauce, experimental groups with intermittent oxygen and nitrogen purging were set up. The results are shown in Tables 2, 3, and 4. First, the nitrogen purging period was fixed at 12 days, and different oxygen purging periods (1 day, 2 days, and 3 days) were set to evaluate their impact on soy sauce quality. The corresponding results are shown in Examples 1.7-1.9. After oxygen purging, nitrogen purging continuously increased the ammonia nitrogen level of the soy sauce. When the oxygen purging period was 1 day and 2 days, the ammonia nitrogen level was better than when oxygen was purged for 3 days. As can be seen from the results of Examples 1.7-1.9, the effect was better when the oxygen purging period was 2 days. Subsequent experiments fixed the oxygen aeration period at 2 days and discussed the effects of different nitrogen aeration periods on the physicochemical properties of soy sauce. The results correspond to Examples 1.10-1.12 in Table 2. The results after oxygen aeration were similar to those of the three groups after nitrogen aeration for days 2-12. The difference was that in Example 1.12, nitrogen aeration was carried out for 14 days. From the detection results on day 14 of nitrogen aeration, although the ammonia nitrogen level was still rising, the corresponding total acid and salt concentrations also increased significantly, and the corresponding pH decreased significantly. Therefore, considering all factors, the effect was optimal when nitrogen aeration lasted for 12 days. Comparative Example 1.2 shows the detection results after 2 days of nitrogen aeration followed by 12 days of oxygen aeration. The ammonia nitrogen level of soy sauce after 2 days of nitrogen aeration was higher than that after 2 days of oxygen aeration in Example 1.8, which further illustrates that nitrogen aeration can indeed increase the ammonia nitrogen level. After continuous oxygen aeration, the ammonia nitrogen level of soy sauce gradually decreased with the extension of oxygen aeration time.

[0132] Table 2. Effects of intermittent nitrogen and oxygen purging on the physicochemical properties of soy sauce (Examples 1.7-1.9)

[0133]

[0134]

[0135] Table 3. Effects of intermittent nitrogen and oxygen purging on the physicochemical properties of soy sauce (Examples 1.10-1.12)

[0136]

[0137]

[0138] Table 4. Effects of intermittent nitrogen and oxygen purging on the physicochemical properties of soy sauce (Comparative Example 1.2)

[0139]

[0140] To evaluate the effects of nitrogen and oxygen introduction on the long-term shelf life of soy sauce, samples were sealed and stored for 6 months under the conditions of Example 1.11, which showed the best effect as indicated by the above experimental results. The control group was sealed and stored for 6 months under the conditions of Comparative Example 1.2. Samples were taken monthly to test ammonia nitrogen, total acid, salt, pH, and L* value. The results are shown in Table 5. As the storage time increased, the ammonia nitrogen level and L* value of both the experimental and control groups gradually decreased. The ammonia nitrogen level of Example 1.13 was consistently higher than that of Comparative Example 1.3, and the rate of decrease was also slower than that of Comparative Example 1.3. After six months of storage, the ammonia nitrogen level of Example 1.13 decreased by 2%, and that of Comparative Example 1.3 decreased by 4.5%. In addition, nitrogen introduction can reduce the color change of soy sauce during long-term storage. Normally, the color of soy sauce will darken and the L* value will decrease rapidly when stored for a long time. Nitrogen plays a protective role in the color of soy sauce and can reduce the oxidation and darkening of the soy sauce color.

[0141] Table 5. Effects of nitrogen and oxygen on long-term storage of soy sauce (ammonia nitrogen and total acid: g / 100g, salt concentration: g / 100mL)

[0142]

[0143] Test example: Sensory evaluation

[0144] Sensory evaluation tests were conducted on the soy sauces from the above-mentioned examples and comparative examples in Experiment 1 (where Example 1.13 and Comparative Example 1.3 were both soy sauces stored for 6 months). A sensory group composed of 10 professionally trained personnel took out the soy sauces, randomly numbered them into three-digit numbers, and had the sensory evaluation personnel perform quantitative evaluations. The amount of soy sauce consumed each time was consistent. The two types of soy sauce were rinsed with water for 30 seconds between 1-minute intervals. The color, aroma, taste, and texture of the soy sauces were compared and scored, with a full score of 100 points. The scoring criteria were formulated with reference to the sensory characteristics in GB / T 18186-2000 "Brewed Soy Sauce". [1] Scoring and evaluation will be conducted.

[0145] According to the results in Table 6, compared with soy sauce that only absorbs oxygen (Examples 1.4-1.6), soy sauce that only absorbs nitrogen (Examples 1.1-1.3) is superior in color, aroma, taste, and texture. Soy sauce that absorbs oxygen first and then nitrogen (Examples 1.7-1.12) is also superior in all four indicators, especially in color and taste. The soy sauce in this case is a deep reddish-brown color, bright and glossy, with a rich, mellow, and harmonious aroma, and a delicious, balanced, and palatable taste. In terms of texture, it is clear, transparent, and viscous. The results for Example 1.13 and Comparative Example 1.3 were evaluated after 6 months of storage. Due to the long storage time, the taste of the soy sauce stored for 6 months after absorbing nitrogen slightly decreased, but it was still better than the soy sauce stored for 6 months after absorbing oxygen.

[0146] Table 6 Sensory Evaluation of Soy Sauce

[0147]

[0148] [1] Zhang Wei, Yang Junwen, Yu Bingyan, et al. Selection of salt-tolerant Lactobacillus plantarum and its effect on the quality of high-salt dilute fermented soy sauce [J]. Food and Fermentation Industries, 2023, 49(1): 86-94.

Claims

1. A method for improving the quality of soy sauce, characterized in that, The methods shown include: 1) Provide cooked soy sauce; 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

2. A method for preparing soy sauce, characterized in that, The method includes: 1) Provide cooked soy sauce; 2) Pour nitrogen gas into the cooked soy sauce from step 1 for more than 12 days to improve the quality of the soy sauce.

3. The method as described in claim 1 or 2, characterized in that, The ventilation is as follows: 1) Purge with nitrogen for 12-28 days, or 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

4. The method according to any one of claims 1-3, characterized in that, The ventilation rate is 1-3L per minute for every 30L of soy sauce.

5. The method according to any one of claims 1-4, characterized in that, The quality of the soy sauce is defined as ammonia nitrogen, color, taste, aroma, and / or appearance.

6. The use of nitrogen gas to improve the quality of soy sauce.

7. The use as described in claim 6, characterized in that, The nitrogen purging process involves purging nitrogen for more than 12 days.

8. The use as described in claim 7, characterized in that, The nitrogen gas used is: 1) Purge with nitrogen for 12-28 days, or 2) First, introduce oxygen for 1-3 days, then introduce nitrogen for 12-28 days.

9. The use as described in any one of claims 6-8, characterized in that, The nitrogen or oxygen gas is introduced at a rate of 1-3L per minute for every 30L of soy sauce.

10. The use as described in any one of claims 6-9, characterized in that, The quality of the soy sauce is defined as ammonia nitrogen, color, taste, aroma, and / or appearance.

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