Method for preparing tagatose and application

Abstract

The invention relates to the technical field of tagatose preparation, and particularly discloses a method for preparing tagatose and application. The method for preparing tagatose comprises the following steps: (1) mixing a galactose solution and an alkaline calcium isomerization agent, and carrying out an isomerization reaction; (2) carrying out acid neutralization reaction by adopting a mixed acid solution; acid in the mixed acid solution comprises phosphoric acid and citric acid; the mass ratio of the phosphoric acid to the citric acid is 1: (1-6); the pH value of the acid neutralization reaction is 2-5.0. According to the preparation method disclosed by the invention, the environmental pollution caused when phosphoric acid is singly used for production conventionally is reduced, the production safety is improved, and an ideal tagatose yield is obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of tagatose preparation, and in particular to a method for preparing tagatose and application thereof. Background Art

[0002] Tagatose is a functional sweetener with a sweetness comparable to that of sucrose, low in calories, and has functional properties such as hypoglycemic, anti-obesity, anti-oxidation, and intestinal flora regulation. Tagatose is made from galactose as a direct raw material through isomerization, decolorization, desalination, concentration, crystallization and other steps. The isomerization step is a key technical link in the production of tagatose. At present, the isomerization step in industrial production is mainly a chemical method, in which alkali metal salts or alkaline earth metals are used as isomerizers to catalyze the reaction to form an insoluble tagatose complex, which is then neutralized with acid. The acid reacts with the insoluble tagatose complex to form an insoluble salt, and the tagatose solution is separated. Among them, the acid neutralization step is an important link that affects the yield and separation and purification of tagatose. In production and most studies, phosphoric acid, CO2, sulfuric acid, carbonic acid, etc. are mostly used for neutralization. However, the use of large amounts of phosphoric acid and sulfuric acid is easy to pollute the environment, and the neutralization reaction time using CO2 and carbonic acid is long, and the production efficiency is low, so further innovation and exploration in technology is still needed. Summary of the invention

[0003] One of the purposes of the present invention is to provide a method for preparing tagatose with low environmental pollution, high production efficiency and ideal tagatose yield.

[0004] The present invention provides a method for preparing tagatose, which comprises: (1) mixing a galactose solution and an alkaline calcium isomerizer to carry out an isomerization reaction; (2) A mixed acid solution is used for acid neutralization reaction; the acid in the mixed acid solution includes phosphoric acid and citric acid; the mass ratio of phosphoric acid to citric acid is 1:(1-6); and the pH value of the acid neutralization reaction is 2-5.0.

[0005] The present invention has found that different types of acids have a great influence on the release and desalting treatment of tagatose in insoluble tagatose complexes. When phosphoric acid and citric acid are acid-neutralized in a specific combination, fewer by-products are produced during the reaction, which can promote the release of tagatose in the isomerization intermediate, thereby efficiently obtaining an ideal tagatose yield. Moreover, compared with the traditional phosphoric acid neutralization process, the scheme of the present invention reduces the amount of phosphoric acid used, thereby reducing environmental pollution. Citric acid is a powder, which belongs to a food processing aid. Compared with commonly used phosphoric acid, sulfuric acid, etc., it is easy to store and operate, and has a high safety factor.

[0006] Preferably, in the method for preparing tagatose of the present invention, the mass ratio of phosphoric acid to citric acid is 1:(3-5), more preferably 1:4, so as to obtain a higher tagatose yield.

[0007] Preferably, in the method for preparing tagatose of the present invention, the pH value of the acid neutralization reaction is 2.5-4, more preferably 3-4, so as to achieve both high yield of tagatose and low conductivity of the neutralization reaction solution.

[0008] In the method of the present invention, the lower the pH value of acid neutralization, the more conducive to the improvement of tagatose yield. However, when the pH value is too low, by-products are easily produced, reducing the purity of tagatose. In addition, at the same pH value, a higher tagatose yield can be obtained with the preferred mass ratio of phosphoric acid and citric acid of the present invention.

[0009] Moreover, after the neutralization reaction is carried out with the preferred specific combination of acids of the present invention, the conductivity of the neutralization reaction solution (containing tagatose solution) can be effectively reduced by centrifugation, thereby helping to reduce the desalting pressure in the subsequent tagatose separation and purification process, reducing the difficulty of subsequent separation and purification operations in industrial production, and thus reducing production costs.

[0010] In the method for preparing tagatose of the present invention, the concentration of galactose in the galactose solution is 5-18%, preferably 9-15%, and more preferably 10-12%. During production, if the galactose content in the galactose solution is too low, the concentration of tagatose in the obtained tagatose-containing solution will be correspondingly reduced, which is not conducive to industrial batch production. If it is too high, solid insoluble intermediates will be generated during the isomerization reaction, resulting in a reduced tagatose yield.

[0011] In the method for preparing tagatose of the present invention, the alkaline calcium isomerizer is calcium hydroxide and / or calcium oxide; the molar ratio of the alkaline calcium isomerizer to the galactose in the galactose solution is (0.5-2):1.

[0012] Those skilled in the art can select the amount of alkaline calcium isomerization agent to be added according to the isomerization reaction principle. Preferably, the molar ratio of the alkaline calcium isomerization agent to the galactose in the galactose solution is 1:1, so as to balance the reaction efficiency and the cost of raw material use.

[0013] In the method for preparing tagatose of the present invention, the temperature of the isomerization reaction is 15-25° C., and the time is 0.5-4 h; preferably, the temperature of the isomerization reaction is 20° C., and the time is 1-3 h.

[0014] In the method for preparing tagatose of the present invention, the temperature of the acid neutralization reaction is 5-15°C; preferably, the temperature of the acid neutralization reaction is 8-12°C (more preferably 10°C). Properly lowering the temperature during the acid adjustment process helps to balance the reaction efficiency and reduce the generation of reaction by-products.

[0015] In the method for preparing tagatose of the present invention, the mass concentration of the acid in the mixed acid solution is 30-60% (preferably 50-60%, more preferably 60%). If the mass concentration of the acid in the mixed acid solution is too low, the amount of wastewater to be treated during production will increase, and if it is too high, the mixed acid will not be easily fully dissolved.

[0016] The method for preparing tagatose of the present invention further comprises the step of centrifuging the product after the acid neutralization reaction in step (2) to obtain a supernatant; The method of separating the tagatose-containing solution from the product after the acid neutralization reaction is well known in the art. Preferably, the centrifugal conditions are: 3000-10000 rpm, 5-20 min, more preferably, the centrifugal conditions are: 5000 rpm, 10-15 min.

[0017] The method for preparing tagatose of the present invention further comprises the step of separating and purifying the tagatose in the supernatant.

[0018] In order to further obtain a purer tagatose product, the tagatose in the supernatant can be further separated and purified. Specifically, the conventional methods in the art can be used for separation and purification. For example, separation and purification include desalting and decolorization, concentration (preferably concentrated to 50-60% Brix) and chromatographic separation (obtaining tagatose separation liquid, galactose separation liquid, and other component sugar separation liquid). Desalting and decolorization treatment is for the purpose of removing the color and salt components in the solution, including but not limited to activated carbon decolorization, ion exchange, nanofiltration, electrodialysis and other methods. Concentration treatment includes but is not limited to evaporation concentration, nanofiltration membrane concentration and other methods. Chromatographic separation can be carried out by simulated moving bed separation, and the chromatographic separation resin used includes but is not limited to Ca 2+ Type, K + type, the eluent is water, the operating temperature, the eluent flow rate and the flow rate of the liquid to be separated can be set according to the common sense in the art to ensure that the various sugar separation liquids in the liquid to be separated can be effectively separated.

[0019] The present invention also provides application of the method for preparing tagatose in improving the yield of preparing tagatose and reducing environmental pollution.

[0020] The beneficial effects of the present invention are at least: The present invention adopts a specific mixed acid in the acid neutralization step of tagatose preparation, thereby reducing the environmental pollution when conventional phosphoric acid is used alone for production, improving production safety, and efficiently obtaining an ideal tagatose yield. The present invention can replace traditional single phosphoric acid or sulfuric acid for large-scale production, and has important guiding significance for the industrial production of tagatose. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1Schematic diagram of the preparation process for obtaining a sugar solution containing tagatose. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0023] The experimental methods used in the following examples are conventional methods unless otherwise specified. The materials, reagents, etc. used in the following examples are commercially available or prepared according to conventional methods in the art unless otherwise specified.

[0024] Example 1 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 3.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min to obtain the supernatant (sugar solution containing tagatose); the process diagram for obtaining the supernatant is shown in Figure 1 .

[0025] The supernatant can be further separated and purified: the supernatant obtained by centrifugation is desalted (to a conductivity of <20 μs / cm) and decolorized (to clarity and transparency) by ion exchange (filler resin model anion resin LX-360, cation resin LX-150), then evaporated and concentrated to 55% Brix, and then separated by chromatography to obtain a purified tagatose solution.

[0026] Example 2 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0027] Example 3 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 4.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0028] Example 4 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:1. The acid solution is slowly added under continuous stirring until the solution pH is 3.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0029] Example 5 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:6. The acid solution is slowly added under constant stirring until the solution pH is 3.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0030] Example 6 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 5% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 2:1 with galactose, and carry out isomerization reaction at 15°C for 0.5h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 5°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:1. The acid solution is slowly added under continuous stirring until the solution pH is 3.2, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 10000rpm for 5min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0031] Example 7 This embodiment provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 18% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 0.5:1 with galactose, and carry out isomerization reaction at 25°C for 4 hours; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 15°C, and 30% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 2.5, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 3000 rpm for 20 min to obtain the supernatant; The supernatant can be further separated and purified using the same method as in Example 1.

[0032] Comparative Example 1 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) phosphoric acid is used for acid neutralization. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0033] Comparative Example 2 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) citric acid solution is used for acid neutralization. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0034] Comparative Example 3 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:7. The acid solution is slowly added under constant stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0035] Comparative Example 4 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 2:1. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0036] Comparative Example 5 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and glacial acetic acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0037] Comparative Example 6 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) lactic acid is used for acid neutralization. The acid solution is slowly added under continuous stirring until the solution pH is 5.0, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0038] Comparative Example 7 This comparative example provides a method for preparing tagatose solution, and the specific preparation process is as follows: 1. Preparation of galactose solution: weigh galactose, prepare a sugar solution with a galactose content of 10% (M / M) with water, and stir to fully dissolve; 2. Isomerization reaction: add calcium hydroxide to the above galactose solution at a molar ratio of 1:1 with galactose, and carry out isomerization reaction at 20°C for 2h; 3. Acid neutralization reaction: After the isomerization reaction is completed, the solution temperature is lowered to 10°C, and 60% (M / M) acid solution is used for acid neutralization. The acid in the acid solution is composed of phosphoric acid and citric acid in a mass ratio of 1:4. The acid solution is slowly added under continuous stirring until the solution pH is 1.5, then the acid addition is stopped and stirring is continued for 10 minutes; 4. Centrifugation: Centrifuge at 5000 rpm for 15 min and obtain the supernatant.

[0039] Experimental example In this experimental example, the tagatose content and conductivity of the supernatant obtained in step 4 of each embodiment and comparative example were detected, and the yield of tagatose was calculated. The results are shown in Table 1.

[0040] The conductivity was directly detected by a conductivity meter; the tagatose content in the supernatant was detected by liquid chromatography, and the liquid chromatography detection conditions were: chromatographic column Sugar-PakTM I WAT085188 (6.5mm×300 mm), column temperature 90℃, differential refractometer temperature 35℃, pure water mobile phase, flow rate 0.4ml / min, injection concentration 0.5%, injection volume 20 microliters. Tagatose yield = tagatose content in supernatant (M / V, g / L) × supernatant volume (L) / raw material galactose weight (g) × 100%.

[0041] Table 1 It can be seen from the analysis of the embodiments and comparative examples that when the phosphoric acid: citric acid mass ratio of 1:4 is used for acid neutralization in Example 1, and the end point is pH 3.0, the tagatose yield in the obtained supernatant is high, which can reach 58.7%, the tagatose content reaches 46.14g / L, and the conductivity of the tagatose solution is reduced to less than 1000μs / cm. Under the same pH conditions, the tagatose yield is higher when the mass ratio of phosphoric acid to citric acid is 1:4. Under the same acid ratio conditions, the lower the neutralization pH, the more tagatose can be released, the higher the supernatant recovery amount, and the higher tagatose yield is obtained. In summary, the scheme of Example 1 is better.

[0042] Although the present invention has been described in detail above with general descriptions and specific embodiments, it is obvious to those skilled in the art that some modifications or improvements may be made thereto based on the present invention. Therefore, these modifications or improvements made without departing from the spirit of the present invention all fall within the scope of protection claimed by the present invention.

Claims

1. A method for preparing tagatose, characterized in that: include: (1) mixing a galactose solution and an alkaline calcium isomerizer to carry out an isomerization reaction; (2) Using a mixed acid solution to carry out acid neutralization reaction; The acid in the mixed acid solution includes phosphoric acid and citric acid; the mass ratio of the phosphoric acid to the citric acid is 1:(1-6); and the pH value of the acid neutralization reaction is 2-5.

0.

2. The method for preparing tagatose according to claim 1, characterized in that: The mass ratio of the phosphoric acid to the citric acid is 1:(3-5).

3. The method for preparing tagatose according to claim 1 or 2, characterized in that: The pH value of the acid neutralization reaction is 2.5-4, preferably 3-4.

4. The method for preparing tagatose according to any one of claims 1 to 3, characterized in that: The concentration of galactose in the galactose solution is 5-18%.

5. The method for preparing tagatose according to any one of claims 1 to 4, characterized in that: The alkaline calcium isomerizer is calcium hydroxide and / or calcium oxide; the molar ratio of the alkaline calcium isomerizer to the galactose in the galactose solution is (0.5-2):

1.

6. The method for preparing tagatose according to any one of claims 1 to 5, characterized in that: The isomerization reaction temperature is 15-25° C. and the reaction time is 0.5-4 h.

7. The method for preparing tagatose according to any one of claims 1 to 6, characterized in that: The temperature of the acid neutralization reaction is 5-15°C; And / or, the mass concentration of acid in the mixed acid solution is 30-60%.

8. The method for preparing tagatose according to any one of claims 1 to 7, characterized in that: The method further comprises the step of centrifuging the product after the acid neutralization reaction in step (2) to obtain a supernatant; preferably, the centrifugation condition is: 3000-10000 rpm, 5-20 min.

9. The method for preparing tagatose according to claim 8, characterized in that: The method also includes a step of separating and purifying tagatose in the supernatant.

10. Use of the method for preparing tagatose according to any one of claims 1 to 9 in improving the yield of preparing tagatose and reducing environmental pollution.

Images