Processing method of low-salt fermented bean curd

Abstract

The invention provides a processing method of low-salt fermented bean curd, and belongs to the technical field of food processing. The processing method disclosed by the invention comprises the following steps: sterilizing a bean curd white blank, performing primary fermentation, performing pickling with seasoning and quality guaranteeing liquid, and performing secondary fermentation. According to the method, the bean curd white blank is sterilized and inoculated with actinomucor elegans for primary fermentation, namely directional pure fermentation, so that infectious microbe pollution can be effectively avoided, and the limitation of fermented bean curd fermentation on a high-salt environment is eliminated. Moreover, compared with the traditional method for pickling by using solid pickling materials, the method for pickling the fermented bean curd blank by using the seasoning quality-guaranteeing liquid can promote the water seepage of the fermented bean curd blank, is more beneficial to endowing the fermented bean curd with salty and fresh taste, can effectively reduce the salt content of the low-salt fermented bean curd on the premise of ensuring the product flavor, and is more in line with the pursuit of current consumers for healthy diet; the health risk of diseases such as hypertension and cardiovascular diseases caused by excessive intake of salt of consumers is reduced, and the consumer groups of the product, especially the crowds having requirements on low-salt diet, are widened.

Description

Technical Field

[0001] The invention belongs to the technical field of food processing, and in particular relates to a processing method of low-salt fermented bean curd. Background Art

[0002] Low-salt fermented bean curd is a traditional fermented soy product. Salt has multiple mechanisms of action in the production process of low-salt fermented bean curd. From the perspective of osmotic pressure, it can promote the exudation of water from the fermented bean curd, reduce water activity, and inhibit the growth of microorganisms; in terms of flavor shaping, it gives the fermented bean curd a salty and fresh taste; at the same time, it has a regulatory effect on the activity of key enzymes such as proteases and lipases, affecting the fermentation process of the fermented bean curd. However, the salt content of traditional fermented bean curd is usually maintained at 12% to 15% in the later stage of fermentation, which is relatively high. However, if the salt content is reduced excessively, the internal water migration of the fermented bean curd will be unbalanced, resulting in a loose texture and collapsed structure; and the low-salt environment cannot effectively inhibit the growth of harmful microorganisms, which can easily lead to corruption and deterioration, greatly shortening the shelf life of the product.

[0003] Therefore, developing a low-salt fermented bean curd is of great significance to promoting the healthy and sustainable development of the fermented bean curd industry. Summary of the invention

[0004] The purpose of the present invention is to provide a processing method for low-salt fermented bean curd, which can obtain low-salt fermented bean curd.

[0005] The invention provides a processing method for low-salt fermented bean curd, comprising the following steps: sterilizing a white tofu blank, inoculating Actinobacillus elegans on the surface of the sterilized white tofu blank, performing pre-fermentation until Actinobacillus elegans hyphae are generated on the surface of the white tofu blank, and obtaining a fermented bean curd blank; flattening the Actinobacillus elegans hyphae on the surface of the fermented bean curd blank, adding the hyphae into a seasoning preservation liquid for soaking, draining the water, and obtaining a pickled fermented bean curd blank; submerging the pickled fermented bean curd blank with cooked rapeseed oil in a container, performing post-fermentation, and inactivating enzymes, and obtaining a low-salt fermented bean curd; the seasoning preservation liquid uses saturated salt water as a solvent and further comprises components of the following concentrations: 2-5 g / L monosodium glutamate, 1-4 g / L disodium nucleotide, 0.1-0.4 g / L sucralose, and 0.3-0.5 g / L sodium dehydroacetate.

[0006] Preferably, the step of inoculating the surface of the sterilized tofu base with Actinomyces elegans comprises: spraying a spore suspension of Actinomyces elegans onto the surface of the sterilized tofu base.

[0007] Preferably, the spore concentration of the spore suspension of Actinobacillus elegans is 10 3 ~10 5 Pieces / mL.

[0008] Preferably, the Actinomucor elegans includes Actinomucor elegans CICC 3093.

[0009] Preferably, the ambient temperature of the pre-fermentation is 25-30° C.; the ambient humidity of the pre-fermentation is 70%-85%; and the time of the pre-fermentation is 20-28 hours.

[0010] Preferably, the soaking time is 10 minutes to 4.5 hours.

[0011] Preferably, the ambient temperature of the post-fermentation is 20-37° C.; and the time of the post-fermentation is ≥30 days.

[0012] Preferably, the sterilization includes high-pressure steam sterilization; the temperature of the high-pressure steam sterilization is 115-121° C.; and the time of the high-pressure steam sterilization is 10-20 minutes.

[0013] Preferably, the soaking process also includes intermittent stirring.

[0014] The present invention also provides low-salt fermented bean curd obtained by the processing method described in the above scheme; the salt content of the low-salt fermented bean curd is 1% to 7%.

[0015] The present invention provides a method for processing low-salt fermented bean curd, comprising the following steps: sterilizing a white tofu base, inoculating Actinobacillus elegans on the surface of the sterilized white tofu base, pre-fermenting, and obtaining a fermented bean curd base; soaking and pickling the fermented bean curd base in a seasoning preservation liquid to obtain a pickled fermented bean curd base; mixing the pickled fermented bean curd base and cooked rapeseed oil in a container, sealing, and then post-fermenting. Traditional fermented bean curd has a high salt content, which is because the traditional fermentation method requires the use of a high-salt environment to inhibit the growth of harmful microorganisms. The present invention sterilizes the white tofu base first and then inoculates Actinobacillus elegans for pre-fermentation, that is, directional pure strain fermentation, which can effectively avoid contamination by miscellaneous bacteria and get rid of the limitation of fermented bean curd fermentation on a high-salt environment. In addition, the present invention utilizes seasoning preservative liquid to soak and marinate the fermented bean curd blank, which can promote the water permeation of the fermented bean curd blank compared with the traditional method of marinating with solid marinade, and is more conducive to giving the fermented bean curd a salty and fresh taste. It can effectively reduce the salt content of low-salt fermented bean curd while ensuring the flavor of the product, which is more in line with the current consumer's pursuit of healthy diet, reduces the health risks of consumers causing hypertension, cardiovascular diseases and the like due to excessive salt intake, and broadens the consumer group of the product, especially those who have a demand for a low-salt diet.

[0016] In addition, the processing method of the present invention adopts directional pure strain fermentation and accurately controls the fermentation microorganism to be Actinomucor elegantis, ensuring the controllability and stability of the fermentation process. Actinomucor elegantis secretes a variety of extracellular enzymes during the fermentation process, such as proteases, lipases, peptidases, etc. These enzymes work synergistically to decompose soy protein and fat into flavor precursors such as amino acids, small molecule peptides, fatty acids, and then generate rich flavor substances through Maillard reaction, esterification reaction, etc., giving fermented bean curd a unique, rich and layered flavor. Compared with traditional fermented fermented bean curd, the low-salt fermented bean curd produced by the processing method of the present invention has an increase of more than 30% in the types of flavor substances, and the proportion of flavor components is more coordinated, bringing consumers a new taste enjoyment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the implementation cases of the present invention or the technical solutions in the prior art, the drawings required for use in the implementation cases will be briefly introduced below. Obviously, the drawings described below are only some implementation cases of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0018] Figure 1 The following are scanning electron microscope (SEM) images of commercially available fermented bean curd, implementation cases, and comparative cases. DETAILED DESCRIPTION

[0019] The invention provides a processing method for low-salt fermented bean curd, comprising the following steps: sterilizing a white tofu blank, inoculating Actinobacillus elegans on the surface of the sterilized white tofu blank, performing pre-fermentation until Actinobacillus elegans hyphae are generated on the surface of the white tofu blank, and obtaining a fermented bean curd blank; flattening the Actinobacillus elegans hyphae on the surface of the fermented bean curd blank, adding the hyphae into a seasoning preservation liquid for soaking, draining the water, and obtaining a pickled fermented bean curd blank; submerging the pickled fermented bean curd blank with cooked rapeseed oil in a container, performing post-fermentation, and inactivating enzymes, and obtaining a low-salt fermented bean curd; the seasoning preservation liquid uses saturated salt water as a solvent and further comprises components of the following concentrations: 2-5 g / L monosodium glutamate, 1-4 g / L disodium nucleotide, 0.1-0.4 g / L sucralose, and 0.3-0.5 g / L sodium dehydroacetate.

[0020] The present invention sterilizes the tofu base first and then inoculates Actinomucor elegans for pre-fermentation, i.e., directional pure strain fermentation, which can effectively avoid contamination by miscellaneous bacteria and get rid of the limitation of fermented bean curd fermentation on high-salt environment. In addition, the processing method of the present invention does not cause structural collapse or rancidity under low-salt conditions.

[0021] In the specific implementation process of the present invention, the processing method consists of the following steps: after sterilizing the tofu blank, inoculating the surface of the sterilized tofu blank with Actinobacillus elegans, pre-fermenting until Actinobacillus elegans hyphae are produced on the surface of the tofu blank to obtain a fermented bean curd blank; flattening the Actinobacillus elegans hyphae on the surface of the fermented bean curd blank, adding it to a seasoning preservation liquid for soaking, draining the water, and obtaining a pickled fermented bean curd blank; using cooked rapeseed oil to submerge the pickled fermented bean curd blank in a container, post-fermenting, inactivating enzymes, and obtaining a low-salt fermented bean curd.

[0022] The method sterilizes tofu blanks, then inoculates Actinobacillus elegans on the surface of the sterilized tofu blanks, performs pre-fermentation, and produces Actinobacillus elegans hyphae on the surface of the tofu blanks to obtain fermented bean curd blanks.

[0023] The purpose of the present invention to sterilize the tofu base is to sterilize the tofu base. In the specific implementation process of the present invention, the sterilization includes high-pressure steam sterilization; the temperature of the high-pressure steam sterilization is 115-121°C; the time of the high-pressure steam sterilization is 10-20 minutes; after the sterilization, it also includes cooling to room temperature.

[0024] In the specific implementation process of the present invention, the tofu base is brine tofu; the tofu base is in a cubic shape with a size of 3×3×3cm; the preparation method of the tofu base comprises the following steps: boiling raw soy milk, cooling it to 85°C, adding MgCl2 to make a paste, keeping it warm in a water bath for 30 minutes, breaking it into pieces, pouring it into a mold, pressing it with a heavy object for 1 hour, and cutting it to obtain the tofu base; the amount of MgCl2 added accounts for 0.03% to 0.04% of the mass percentage of the raw soy milk, and further 0.038%; the preparation method of the raw soy milk is: soaking the washed soybeans in water for 10 hours, taking out the soybeans, grinding and filtering them according to a mass ratio of dry beans to water of 1:6 to 1:8 to obtain raw soy milk; the particle size of the raw soy milk is less than 200 meshes; the soybeans are selected high-quality soybeans.

[0025] In the specific implementation process of the present invention, the inoculation of the sterilized tofu white base with the spore suspension of Actinobacillus elegans comprises: spraying the spore suspension of Actinobacillus elegans onto the sterilized tofu white base, with the spraying being uniform. In the specific implementation process of the present invention, the spore concentration of the spore suspension of Actinobacillus elegans is 10 3 ~10 5 / mL, further 10 4 In the specific implementation of the present invention, the Actinomucor elegans includes Actinomucor elegans CICC 3093. In the specific implementation of the present invention, the preparation method of the Actinomucor elegans spore suspension is as follows: using physiological saline to prepare Actinomucor elegans spores with a concentration of 10 5 / mL spore suspension was inoculated into potato glucose liquid medium at a volume ratio of 1:100, and cultured at 28°C and 200 rpm for 36 h. The hyphae were removed by filtration with sterile gauze, and the spore suspension after shaking culture was diluted to 10 with physiological saline. 3 ~10 5 Pieces / mL.

[0026] In the specific implementation process of the present invention, the ambient temperature of the pre-fermentation is 25-30°C, further 28°C; the ambient humidity of the pre-fermentation is 70%-85%; the time of the pre-fermentation is 20-28h. The pre-fermentation conditions of the present invention are suitable conditions for Actinomucor elegans. Under a suitable environment, Actinomucor elegans grows and reproduces rapidly, has high metabolic activity, and can quickly convert substrates into target products. In addition, the mycelium is well developed to form a supporting structure, so that the pores in the microstructure are uniform, the texture is good, and the enzymatic hydrolysis and reorganization form uniformly dispersed microparticles.

[0027] After obtaining the fermented bean curd blank, the present invention flattens the Actinomucor elegantis hyphae on the surface of the fermented bean curd blank, adds the fermented bean curd blank into a seasoning preservation liquid for soaking, drains the water, and obtains the pickled fermented bean curd blank; the seasoning preservation liquid uses saturated salt water as a solvent and further includes the following components in concentrations: 2-5 g / L monosodium glutamate, 1-4 g / L disodium nucleotide, 0.1-0.4 g / L sucralose, and 0.3-0.5 g / L sodium dehydroacetate.

[0028] In the present invention, the functions of flattening the elegant Actinobacillus hyphae on the surface of the fermented bean curd blank are as follows: 1) removing hyphae: the white hyphae (Mucor) formed in the early fermentation needs to be removed to avoid excessive reproduction and corruption during subsequent pickling; 2) promoting flavor absorption: destroying the hyphae network structure to make salt and seasonings easier to penetrate; 3) adjusting the texture: slightly damaging the surface of the tofu through physical friction to form a delicate taste; 4) controlling fermentation: interrupting the hyphae metabolic activity to prevent excessive decomposition of protein.

[0029] In the specific implementation process of the present invention, the seasoning preservation liquid uses saturated salt water as a solvent and is composed of the following components in the following concentrations: 2-5 g / L monosodium glutamate, 1-4 g / L disodium nucleotide, 0.1-0.4 g / L sucralose and 0.3-0.5 g / L sodium dehydroacetate; the seasoning preservation liquid is used to adjust the flavor of fermented bean curd.

[0030] In one embodiment of the present invention, the seasoning preservation solution uses saturated saline as a solvent and is composed of the following components in the following concentrations: 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate.

[0031] In the specific implementation of the present invention, the soaking time is 10 minutes to 4.5 hours, and further 20 minutes to 2 hours.

[0032] During the soaking process, the present invention also includes intermittent stirring to ensure that the salt is evenly distributed inside the fermented bean curd, so that each mouthful of the fermented bean curd has consistent saltiness, a stable taste, and a balanced flavor; the intermittent stirring is slow stirring every 5 minutes.

[0033] After obtaining the pickled fermented bean curd blank, the invention uses cooked rapeseed oil in a container to submerge the pickled fermented bean curd blank, and then ferments and inactivates enzymes to obtain low-salt fermented bean curd.

[0034] In the specific implementation process of the present invention, the ambient temperature of the post-fermentation is 15-40°C, further 20-37°C, and this temperature condition is conducive to improving the quality of fermented bean curd; the time of the post-fermentation is ≥30d, further 30-45d; the post-fermentation is carried out under sealed conditions to avoid contamination by miscellaneous bacteria; the enzyme inactivation includes high-temperature enzyme inactivation, and the high-temperature enzyme inactivation includes water bathing at 90°C for 30min.

[0035] The present invention adopts directional pure strain fermentation combined with reasonable pre-fermentation and post-fermentation conditions, which can significantly shorten the fermentation cycle of fermented bean curd. Compared with traditional natural fermentation, the fermentation cycle of the present invention is shortened by more than 50%, which effectively reduces production costs, improves enterprise production efficiency and economic benefits, and enhances the competitiveness of products in the market. During the post-fermentation process, the enzymes produced by Mucor continue to act on the fermented bean curd, reducing the hardness, elasticity and chewiness of the fermented bean curd. At the same time, the rapeseed oil interacts with the fermented bean curd ingredients, further optimizing the texture and taste of the fermented bean curd, making it more delicate and smooth, with a unique oily flavor, and improving the overall quality of the product and consumer satisfaction.

[0036] In the specific implementation process of the present invention, the preparation method of the cooked rapeseed oil comprises the following steps: burning the rapeseed oil until it smokes, and cooling it to room temperature in a sterile environment.

[0037] The present invention also provides low-salt fermented bean curd obtained by the processing method described in the above scheme; the salt content of the low-salt fermented bean curd is 1% to 7%, further 1% to 5%.

[0038] Compared with the fermented bean curd prepared by the traditional method, the salt content of the low-salt fermented bean curd of the invention can be reduced to 2%-5%.

[0039] The low-salt fermented bean curd of the invention not only has a low salt content but also has a mellow flavor, is helpful in reducing salt intake, conforms to the trend of healthy diet, and has good application value.

[0040] In order to further illustrate the present invention, a processing method of low-salt fermented bean curd provided by the present invention is described in detail below in conjunction with the accompanying drawings and implementation examples, but they should not be construed as limiting the scope of protection of the present invention.

[0041] Implementation Case 1

[0042] A method for preparing low-salt fermented bean curd, comprising the following steps:

[0043] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0044] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0045] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0046] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0047] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 28°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0048] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 20 minutes and drain the water, add cooked rapeseed oil to seal and place it at 30°C for post-fermentation for 45 days, and water bath at 90°C for 30 minutes to inactivate the enzyme to obtain low-salt fermented bean curd.

[0049] Implementation Case 2

[0050] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0051] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0052] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0053] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0054] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 28°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0055] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 2 hours and drain the water, add cooked rapeseed oil to seal and place it at 30°C for post-fermentation for 45 days, and inactivate the enzyme in a water bath at 90°C for 30 minutes to obtain low-salt fermented bean curd.

[0056] Implementation Case 3

[0057] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0058] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0059] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0060] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0061] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 104 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 28°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0062] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 4.5 hours and drain the water, add cooked rapeseed oil to seal and place it at 30°C for post-fermentation for 45 days, and inactivate the enzyme in a water bath at 90°C for 30 minutes to obtain low-salt fermented bean curd.

[0063] Comparative Case 1

[0064] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0065] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0066] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0067] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0068] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 20°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0069] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 20 minutes and drain the water, add cooked rapeseed oil to seal and place it at 30°C for post-fermentation for 45 days, and water bath at 90°C for 30 minutes to inactivate the enzyme to obtain low-salt fermented bean curd.

[0070] Comparative Case 2

[0071] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0072] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0073] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0074] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0075] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinobacillus elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 35°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank, thus obtaining the fermented bean curd blank;

[0076] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 20 minutes and drain the water, add cooked rapeseed oil to seal and place it at 30°C for post-fermentation for more than 45 days, and water bath at 90°C for 30 minutes to inactivate the enzyme to obtain low-salt fermented bean curd.

[0077] Comparative Case 3

[0078] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0079] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0080] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0081] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0082] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 28°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0083] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 20 minutes and drain the water, add cooked rapeseed oil to seal and place it at 15°C for post-fermentation for 45 days, and water bath at 90°C for 30 minutes to inactivate the enzyme to obtain low-salt fermented bean curd.

[0084] Comparative Case 4

[0085] 1) Preparation of raw soy milk: Soak the washed soybeans in water until they swell, take out the soybeans, grind them and filter them to obtain raw soy milk;

[0086] 2) Preparation of seasoning solution: add 3 g / L monosodium glutamate, 3 g / L disodium nucleotide, 0.4 g / L sucralose and 0.5 g / L sodium dehydroacetate to saturated saline;

[0087] 3) Preparation of tofu blank: boil the mixed soy milk, cool to 85° C., add 0.038% of MgCl2 coagulant by weight of the soy milk, gently stir and mix evenly, let stand and press for 1 hour, cut into pieces, and obtain tofu blank;

[0088] 4) Sterilization of tofu: sterilize with high pressure steam at 121°C for 20 min, and cool to room temperature;

[0089] 5) Preparation and pickling of fermented bean curd: Use physiological saline to make a spore suspension of Actinobacillus elegans (10 5 / mL) and inoculated it into potato glucose liquid medium at a volume ratio of 1:100 and cultured at 28°C with shaking (200 rpm) for 36 h. Filter the mycelium with sterile gauze and dilute the spore suspension to 10 4 The suspension of Actinomucor elegans spores is evenly sprayed on the surface of the sterilized tofu blank in step 4), and pre-fermented at 28°C for 25 hours with a pre-fermentation humidity of 85%, and Mucor hyphae are generated on the surface of the tofu blank to obtain the fermented bean curd blank;

[0090] 6) Preparation of low-salt fermented bean curd: flatten the mold hyphae on the surface of the fermented bean curd blank, add seasoning liquid to soak for 20 minutes and drain the water, add cooked rapeseed oil to seal and place it at 40°C for post-fermentation for 45 days, and water bath at 90°C for 30 minutes to inactivate the enzyme to obtain low-salt fermented bean curd.

[0091] Test Example 1

[0092] The low-salt fermented bean curd of implementation cases 1 to 3 and the finished low-salt fermented bean curd of comparison cases 1 to 4 were tested, and the sensory score table is shown in Table 1. As can be seen from Table 2, the fermented bean curd bodies and cross-sections of implementation cases 1 to 3 are light yellow and shiny. The fermented bean curd has a soft texture, moderate saltiness, a delicate and long taste, and the auxiliary materials are coordinated with the unique aroma of fermentation. The aroma is pure and attractive, which helps to increase appetite and has a high sensory score. The commercially available fermented bean curd is salty, and the internal granularity of comparison cases 1 to 3 is strong, the texture is soft and rotten, and the taste is rough. The color of comparison case 4 is dark yellow, the organizational morphology and taste are poor, and the sensory score is low.

[0093] Table 1 Sensory score table for low-salt fermented bean curd

[0094]

[0095]

[0096] Table 2 Sensory evaluation results of low-salt fermented bean curd of implementation cases 1 to 3, low-salt fermented bean curd of comparison cases 1 to 4, and traditional fermented bean curd sold on the market

[0097]

[0098] Note: The fermented bean curd available on the market is produced and bottled within 1 month.

[0099] Test Example 2

[0100] The quality of the low-salt fermented bean curd of implementation cases 1 to 3, the low-salt fermented bean curd of comparison cases 1 to 4, and the commercially available traditional fermented bean curd (Bridge brand white fermented bean curd) was compared.

[0101] The texture of low-salt fermented bean curd was analyzed using a TA-XTplus texture analyzer. Measurement parameters: probe P36 / R, pre-test speed 1mm / s, test speed 2mm / s, post-test speed 1mm / s, trigger force 0.4g, data acquisition rate 200pps. The epidermal hardness and internal hardness are the loads measured when the probe penetrates 2mm and 8mm from the gel surface, respectively. The results are shown in Table 3.

[0102] Table 3 Quality comparison of implementation cases and traditional fermented bean curd sold on the market

[0103]

[0104]

[0105] As can be seen from Table 3, the hardness, elasticity and chewiness of the low-salt fermented bean curd of Implementation Cases 1 to 3 are better than those of the commercially available group and other implementation case groups; and because the amount of salt added in Implementation Case 1 is 2%, the salt content is lower than that in Implementation Case 2 and Implementation Case 3, so during the post-fermentation process, the enzyme produced by Mucor continues to act on the fermented bean curd, reducing the hardness, elasticity and chewiness of the fermented bean curd; after the subsequent enzyme inactivation treatment, the texture of Implementation Case 1 is still better than that of the commercially available group.

[0106] Table 4 Comparison of main physical and chemical indicators

[0107]

[0108] From the test results in Table 4, it can be seen that the total acid, amino acid nitrogen and moisture of the low-salt fermented bean curd of implementation cases 1 to 3 and the low-salt fermented bean curd of comparison cases 1 to 4 all meet the national standards, and the fermented bean curd prepared in implementation case 1 is the best.

[0109] The microstructure of low-salt fermented bean curd was observed using a Czech TESCAN VEGA 3SBU scanning electron microscope. The specific process is as follows: 1) Sample preparation: Cut low-salt fermented bean curd into slices of 10mm×10mm×1mm; 2) Fixation: Add 2.5% glutaraldehyde solution and fix overnight at 4℃; 3) Rinse: Rinse the sample 3 times with 0.1mol / L pH 6.8 phosphate buffer, 15min each time; 4) Dehydration: Dehydrate with 30%, 50%, 70%, 80%, 90%, 95% ethanol solution in a gradient manner, 15min each time, and dehydrate with 100% ethanol for 3 times, 15min each time; 5) Replacement: Replace with isoamyl acetate twice, 15min each time; 6) Drying: CO2 critical point drying; 7) Spray gold; 8) Observe at 2000 times.

[0110] During the fermentation process, protein aggregates and gel pores gradually decrease, and the internal structure changes from rough to smooth. Figure 1 As shown, Figure 1 Scanning electron microscope (SEM) images of commercially available fermented bean curd, implementation cases, and comparative cases. SEM parameters: All images were acquired at an accelerating voltage of 20.0 kV, with an image magnification of 2.00 kx (i.e., 2000 times), and the shooting date was August 2, 2024, using a VEGA3 TE-SCAN device. The working distance (WD) is slightly different, as indicated at the bottom of each image in millimeters (mm); Scale: The scale at the bottom of the image is used to measure the size of the microstructure in micrometers (μm), which can be used to visually compare the size of the microstructure of different samples, such as particle diameter, pore spacing, and other features.

[0111] The results showed that the microstructure of implementation cases 1 to 3 was smoother and more delicate than that of commercially available low-salt fermented bean curd; the microstructure of implementation cases 1 to 3 was smoother and more delicate than that of comparison cases 1 and 2. This was because when the pre-fermentation temperature was too high or too low, resulting in poor growth of Mucor, the mycelium was not well developed and could not form a supporting structure, resulting in uneven pores in the microstructure, affecting the texture, and insufficient enzymatic hydrolysis resulting in large particles rather than evenly dispersed tiny particles; the microstructure of implementation cases 1 to 3 was smoother and more delicate than that of comparison cases 3 and 4. This was because the post-fermentation stage of fermented bean curd was a critical period for quality formation, and temperature played a decisive role in the formation and stability of the microstructure.

[0112] In summary, the present invention compares the texture of low-salt fermented bean curd fermented by elegant Actinobacillus and commercially available low-salt fermented bean curd during the fermentation process. The results show that the hardness of the low-salt fermented bean curd fermented by elegant Actinobacillus is less than that of the commercially available low-salt fermented bean curd, and the microstructure is more delicate, indicating that it can replace traditional natural fermentation to improve the texture of low-salt fermented bean curd in the actual production process, and adopts a saturated salt water soaking process to ensure that the salt content of the fermented bean curd is evenly distributed. In addition, the method of the present invention reduces the salt content of the fermented bean curd while ensuring the taste and quality of the fermented bean curd.

[0113] Although the above implementation case has made a detailed description of the present invention, it is only a part of the implementation cases of the present invention, rather than all the implementation cases. People can also obtain other implementation cases based on this implementation case without creativity, and these implementation cases all fall within the scope of protection of the present invention.

Claims

1. A method for processing low-salt fermented bean curd, characterized in that: The following steps are involved: After sterilizing the tofu base, inoculating Actinobacillus elegans on the surface of the sterilized tofu base, and performing pre-fermentation until Actinobacillus elegans hyphae are produced on the surface of the tofu base to obtain the fermented bean curd base; After flattening the hyphae of Actinomucor elegantis on the surface of the fermented bean curd blank, adding it into the seasoning preservation liquid for soaking, draining the water, and obtaining the pickled fermented bean curd blank; The pickled fermented bean curd blank is submerged in cooked rapeseed oil in a container, post-fermented, and enzyme-killed to obtain low-salt fermented bean curd; The seasoning preservation liquid uses saturated salt water as a solvent and further comprises components in the following concentrations: 2-5 g / L monosodium glutamate, 1-4 g / L disodium nucleotide, 0.1-0.4 g / L sucralose and 0.3-0.5 g / L sodium dehydroacetate.

2. The processing method according to claim 1, characterized in that: The method of inoculating the surface of the sterilized tofu base with Actinobacillus elegans comprises: spraying a suspension of Actinobacillus elegans spores onto the surface of the sterilized tofu base.

3. The processing method according to claim 2, characterized in that: The spore concentration of the spore suspension of Actinobacillus elegans is 10 3 ~10 5 Pieces / mL.

4. The processing method according to claim 1, characterized in that: The Actinomucor elegans includes Actinomucor elegans CICC 3093.

5. The processing method according to claim 1, characterized in that: The environmental temperature of the pre-fermentation is 25-30° C.; the environmental humidity of the pre-fermentation is 70%-85%; and the time of the pre-fermentation is 20-28 hours.

6. The processing method according to claim 1, characterized in that: The soaking time is 10 minutes to 4.5 hours.

7. The processing method according to claim 1, characterized in that: The environmental temperature of the post-fermentation is 20-37° C.; the time of the post-fermentation is ≥30 days.

8. The processing method according to claim 1, characterized in that: The sterilization includes high-pressure steam sterilization; the temperature of the high-pressure steam sterilization is 115-121° C.; the time of the high-pressure steam sterilization is 10-20 minutes.

9. The processing method according to claim 1, characterized in that: The soaking process also includes intermittent stirring.

10. Low-salt fermented bean curd obtained by the processing method according to any one of claims 1 to 9; the salt content of the low-salt fermented bean curd is 1% to 7%.

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