A method for preparing a low total sulfur caramel color
By combining xylose mother liquor and glucose mother liquor and precisely controlling reaction conditions, the problem of residual sulfur in caramel color was solved, achieving efficient preparation of low-total-sulfur caramel color, improving product safety and economic benefits, and expanding the international market.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- ZHEJIANG HUAKANG PHARMA
- Filing Date
- 2026-03-31
- Publication Date
- 2026-07-07
AI Technical Summary
The existing production of caramel colorings poses health risks and high costs due to sulfur residues, especially the ammonium sulfite method, which results in excessive sulfur residues, affecting food safety and increasing production costs.
The residue obtained by separating xylose mother liquor and glucose mother liquor through a simulated moving bed was used as a reaction substrate. By combining raw materials and precisely controlling reaction conditions, including pH and temperature, the amount of catalyst used was reduced, and the caramelization reaction was carried out efficiently to prepare low total sulfur caramel color.
It significantly reduces the total sulfur content in caramel color, improves the redness and salt resistance of products, reduces production costs, meets food safety standards, reduces environmental treatment costs, avoids trade barriers, and enhances product quality and market competitiveness.
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Figure SMS_1
Abstract
Description
Technical Field
[0001] This invention belongs to the field of sugar alcohol preparation technology, and specifically relates to a method for preparing low total sulfur caramel color. Background Technology
[0002] Caramel color is a complex reddish-brown or dark brown mixture formed by the dehydration, decomposition, and polymerization of sugars (such as maltose, sucrose, molasses, invert sugar, lactose, malt syrup, and starch hydrolysis products) at high temperatures. Some of these substances are colloidal aggregates. It is a widely used semi-natural food coloring agent. Based on the raw materials used in its production, caramel color is classified into four categories: Category I is ordinary caramel color prepared using traditional processes; Category II is caustic sulfite caramel color; Category III is ammonia-based caramel color; and Category IV is ammonium sulfite caramel color. In my country, only Category I, III, and IV caramel color are permitted for use, with Category IV (ammonium sulfite method) caramel color being the most widely used. The essence of the ammonium sulfite method is to use ammonium sulfite as a catalyst to accelerate the caramelization and Maillard reactions of sugars, thereby efficiently producing caramel color. However, this method itself has the problem of large amounts of residual sulfur, such as sulfites, sulfonation reaction residues, and sulfur-containing intermediates.
[0003] From a food safety perspective, sulfur residues pose potential health risks. Firstly, there are acute toxicity and allergic reactions. For example, some individuals (such as asthma patients) may be allergic to sulfites; ingesting caramel coloring with high sulfur content may trigger allergic reactions such as shortness of breath, rashes, and diarrhea. Furthermore, high doses of inorganic sulfur (such as sulfites) may irritate the gastrointestinal mucosa, leading to nausea, vomiting, or abdominal pain. Secondly, there are chronic toxicity and long-term risks. For instance, animal studies have shown that long-term intake of high doses of sulfur-containing caramel coloring may increase the metabolic burden on the liver and kidneys.
[0004] From a cost perspective, most manufacturers using the ammonium sulfite process to prepare caramel color often use catalysts with a concentration exceeding 15%, resulting in high total sulfur content and consequently high product costs. Furthermore, reducing the total sulfur content to meet national standards may require the use of high-purity raw materials (such as low-sulfur sugars and refined ammonium sulfite) or the introduction of additional purification steps (such as activated carbon adsorption and membrane separation), which increases raw material costs and production cycles. Moreover, optimizing reaction conditions (such as precise temperature control and staged pH adjustment) may necessitate equipment upgrades, further increasing production costs. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a method for preparing low total sulfur caramel color, which uses the residue obtained by separating xylose mother liquor and glucose mother liquor through a simulated moving bed as a reaction substrate. Under the premise of significantly reducing the amount of catalyst and the introduction of sulfur source, the raw material compounding achieves synergistic effect, ensuring that the caramelization reaction and Maillard reaction proceed efficiently and completely, and obtaining a low total sulfur caramel color product with higher redness and better salt resistance.
[0006] This invention is achieved by providing a method for preparing low-total-sulfur caramel color, comprising the following steps: Step 1: The xylose mother liquor and glucose mother liquor obtained by separation in a simulated moving bed are evaporated and concentrated to 65%~80% refractive index, and then set aside. Step 2: Weigh the concentrated xylose extract and glucose extract separately according to a mass ratio of 7:3 to 6:4 and mix them. Then add 5% to 8% of a catalyst by mass to obtain a mixed solution. The catalyst is ammonium sulfite and sodium metabisulfite, with the ratio of ammonium sulfite to sodium metabisulfite being 1:1 to 1:4. Step 3: Adjust the pH of the mixed solution to 5-6 using 30% sodium hydroxide, then add it to the reactor. Control the reaction temperature between 115-130℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches 0.035-0.038, add 0.5%-0.7% sodium metabisulfite by mass and add 30% sodium hydroxide to adjust the pH to 5-6. Step 4: Heat to 135~140℃, react for 2~3 hours, then cool to room temperature to obtain the desired caramel coloring product.
[0007] Traditional low-sulfur caramel production suffers from the drawback of "reaction first, remedial measures later," requiring downstream refining processes such as ozone oxidation, calcium hydroxide desulfurization, membrane filtration, and flash evaporation, resulting in a lengthy and costly process. This invention replaces downstream remedial measures with precise front-end control. By controlling the pH of the reaction system to 5-6 and the segmented temperatures of 115-130℃ and 135-140℃, the formation of sulfites and 4-methylimidazole is suppressed at the source, eliminating all subsequent refining processes and achieving a redundancy-free process chain design. This invention does not require the addition of ozone, oxidants, or calcium hydroxide to the reaction vessel for sulfur dioxide removal, reducing reaction costs and being environmentally friendly.
[0008] This invention breaks through the bottlenecks of traditional low-sulfur caramel, which suffers from low red index and poor salt tolerance. It achieves a triple synergy of total sulfur content (2.1%~2.6%), red index (6.2~6.3), and salt tolerance, overcoming the industry prejudice that low sulfur necessarily means low quality. 1.5g of caramel color product prepared using this method shows no precipitation in 50mL of 18% sodium chloride solution, meeting the requirements for use in high-salt systems. The total sulfur content is below 3% and complies with the EU standard of ≤10ppm sulfur dioxide. This invention reconstructs the quality system of low-sulfur caramel through a fully coupled chain.
[0009] Compared with the prior art, the method for preparing low total sulfur caramel color of the present invention also has the following characteristics: 1. Significant environmental benefits: Low total sulfur technology reduces sulfur emissions at the source by reducing or eliminating the use of sulfur-containing substances, thereby reducing environmental treatment costs. Furthermore, some processes use green solvents, further reducing environmental pollution and conforming to the trend of "green manufacturing".
[0010] 2. Higher process efficiency and lower production cost: The low total sulfur technology achieves milder reaction conditions (such as low temperature and low pressure) through catalyst-coordinated reaction or continuous reaction equipment. Compared with the high temperature and high pressure reaction of the existing technology, it can reduce energy consumption by more than 30%. At the same time, due to the reduction of by-products, the subsequent purification steps are simpler and no further refining process is required, which improves the overall yield and indirectly reduces production costs.
[0011] 3. Compliant with regulatory upgrades and circumventing trade barriers: In recent years, countries have increasingly stringent safety requirements for food additives, with restrictions on sulfur residues in caramel colorings gradually tightening (e.g., China's GB1886.64-2015 sets a clear upper limit for sulfur residues in caramel colorings). Caramel coloring products exceeding sulfur content limits may face market bans or recalls. Products manufactured using low-total-sulfur technology directly meet the latest regulatory requirements, helping companies circumvent trade barriers and expand into international markets.
[0012] 4. Product health and safety: Low total sulfur technology reduces the total sulfur content to below 3% by reducing catalysts and optimizing process parameters (such as adjusting temperature, pH value, and reaction time), which greatly reduces the threat to human health. Detailed Implementation
[0013] To make the technical problems, solutions, and beneficial effects of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.
[0014] A preferred embodiment of the method for preparing low-total-sulfur caramel color of the present invention includes the following steps: Step 1: The xylose mother liquor and glucose mother liquor obtained by separation by simulated moving bed are evaporated and concentrated to 65%~80% refractive index, and then set aside.
[0015] Step 2: Weigh out the concentrated xylose extract and glucose extract separately according to a mass ratio of 7:3 to 6:4 and mix them. Then add 5% to 8% of a catalyst by mass to obtain a mixed solution. The catalyst is ammonium sulfite and sodium metabisulfite, with an ammonium sulfite:sodium metabisulfite ratio of 1:1 to 1:4.
[0016] Step 3: Adjust the pH of the mixed solution to 5-6 using 30% sodium hydroxide, then add it to the reactor. Control the reaction temperature between 115-130℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches 0.035-0.038, add 0.5%-0.7% sodium metabisulfite by mass and add 30% sodium hydroxide to adjust the pH to 5-6.
[0017] Step 4: Heat to 135~140℃, react for 2~3 hours, then cool to room temperature to obtain the desired caramel coloring product.
[0018] In step one, the xylose mother liquor contains, by mass percentage: xylose 11.2%~12.0%, mannose 4.0%~6.0%, glucose 26.0%~34.0%, arabinose 28.0%~31.0%, and other components 17.0%~31.0%.
[0019] In step one, the glucose mother liquor contains, by mass percentage: 78.0%~83.0% glucose, 5.0%~10.0% fructose, and 8.0%~12.0% other components.
[0020] In step two, the glucose extract contains, by mass percentage: 28.0% to 32.0% glucose, 40.0% to 45.0% fructose, and 25.0% to 30.0% other components.
[0021] In step two, the xylose extract contains, by mass percentage: xylose 2.0%~4.0%, mannose 6.0%~8.0%, glucose 35.0%~40.0%, arabinose 35.0%~40.0%, and other components 8.0%~22.0%.
[0022] The method for preparing low-total-sulfur caramel color according to the present invention is further illustrated below through specific embodiments.
[0023] Example 1
[0024] The first embodiment of the method for preparing low total sulfur caramel color of the present invention includes the following steps: Step 11: The xylose mother liquor and glucose mother liquor, obtained by separation using a simulated moving bed, are concentrated by evaporation and concentration to 70% refractive index at 80℃ and -0.1MPa, and then set aside. The xylose mother liquor, by mass percentage, contains: xylose 11.6%, mannose 5.0%, glucose 30.0%, arabinose 29.5%, and other components 23.9%; the glucose mother liquor, by mass percentage, contains: glucose 80.5%, fructose 7.5%, and other components 12.0%.
[0025] Step 12: Weigh 700g of the concentrated xylose extract and glucose extract separately and mix them at a mass ratio of 6:4. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 7% and 1:1 and mix to obtain a mixed solution. The glucose extract, by mass percentage, contains: 30.0% glucose, 42.5% fructose, and 27.5% other components; the xylose extract, by mass percentage, contains: 3.0% xylose, 7.0% mannose, 37.5% glucose, 37.5% arabinose, and 15.0% other components.
[0026] Step 13: Adjust the pH of the mixed solution to 5.5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 115℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.6% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 5.5.
[0027] Step 14: Heat to 135℃, react for 3 hours, then cool to room temperature to obtain the desired caramel coloring product.
[0028] The prepared caramel color product was subjected to relevant tests. The caramel color product of Example 1 had an absorbance of 0.058, a red finger of 6.20, and passed the salt resistance test. Using the total sulfur detection method specified in the national standard GB1886.64-2015, the total sulfur detection result was 2.1%.
[0029] Example 2
[0030] A second embodiment of the method for preparing low-total-sulfur caramel color of the present invention includes the following steps: Step 21: The xylose mother liquor and glucose mother liquor, obtained by separation using a simulated moving bed, are concentrated by evaporation and concentration to 65% refractive index at 80℃ and -0.1MPa, respectively, for later use. The xylose mother liquor, by mass percentage, contains: xylose 11.2%, mannose 6.0%, glucose 26.0%, arabinose 31%, and other components 25.8%; the glucose mother liquor, by mass percentage, contains: glucose 78%, fructose 10%, and other components 12.0%.
[0031] Step 22: Weigh 700g of the concentrated xylose extract and glucose extract separately and mix them at a mass ratio of 6:4. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 8% and 1:3 respectively to obtain a mixed solution. The glucose extract, by mass percentage, contains: 28.0% glucose, 45.0% fructose, and 27.0% other components; the xylose extract, by mass percentage, contains: 2.0% xylose, 6.0% mannose, 40.0% glucose, 40.0% arabinose, and 12.0% other components.
[0032] Step 23: Adjust the pH of the mixed solution to 5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 120℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.5% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 5.
[0033] Step 24: Heat to 137℃, react for 2.5 hours, then cool to room temperature to obtain the desired caramel coloring product.
[0034] The prepared caramel color product was subjected to relevant tests. The caramel color product of Example 1 had an absorbance of 0.058, a red finger of 6.30, and passed the salt resistance test. Using the total sulfur detection method specified in the national standard GB1886.64-2015, the total sulfur detection result was 2.3%.
[0035] Example 3
[0036] A third embodiment of the method for preparing low-total-sulfur caramel color of the present invention includes the following steps: Step 31: The xylose mother liquor and glucose mother liquor, obtained by separation using a simulated moving bed, are concentrated by evaporation and concentration to 80% refractive index at 80℃ and -0.1MPa, and then set aside. The xylose mother liquor, by mass percentage, contains: xylose 12.0%, mannose 4.0%, glucose 34.0%, arabinose 28.0%, and other components 22.0%; the glucose mother liquor, by mass percentage, contains: glucose 83.0%, fructose 5.0%, and other components 13.0%.
[0037] Step 32: Weigh 700g of the concentrated xylose extract and glucose extract separately and mix them at a mass ratio of 6:4. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 7% and 1:4 to obtain a mixed solution. The glucose extract, by mass percentage, contains: 32.0% glucose, 40.0% fructose, and 28.0% other components. The xylose extract, by mass percentage, contains: 4.0% xylose, 8.0% mannose, 35.0% glucose, 35.0% arabinose, and 18.0% other components.
[0038] Step 33: Adjust the pH of the mixed solution to 6 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 130℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.7% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 6.
[0039] Step 34: Heat to 140℃, react for 2 hours, then cool to room temperature to obtain the desired caramel coloring product.
[0040] The prepared caramel color product was subjected to relevant tests. The caramel color product of Example 1 had an absorbance of 0.058, a red finger of 6.24, and passed the salt resistance test. Using the total sulfur detection method specified in the national standard GB1886.64-2015, the total sulfur detection result was 2.6%.
[0041] Comparative Example 1 The first comparative example of the preparation of caramel color according to the present invention includes the following steps: Step D11: The xylose extract obtained by separating the xylose mother liquor through a simulated moving bed is concentrated and evaporated and concentrated to 70% refractive index at 80℃ and -0.1MPa for later use.
[0042] Step D12: Weigh 700g of the concentrated xylose extract, add ammonium sulfite and sodium metabisulfite catalyst in a mass ratio of 7% and 1:1, and mix to obtain a mixed liquid.
[0043] Step D13: Adjust the pH of the mixture to 5.5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 115℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.6% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 6.
[0044] Step D14: After reacting for 3 hours, cool to room temperature to obtain the desired caramel coloring product.
[0045] The prepared caramel color product was subjected to relevant tests. The caramel color product of Comparative Example 1 had an absorbance of 0.058, a red finger of 5.50, and passed the salt resistance test. The total sulfur content was 2.9% according to the total sulfur detection method specified in the national standard GB1886.64-2015.
[0046] Comparative Example 2 The second comparative example of preparing caramel color according to the present invention includes the following steps: Step D21: Concentrate the glucose retentate obtained by separating the glucose mother liquor through a simulated moving bed, and evaporate and concentrate it to 65% refractive index at 80℃ and -0.1MPa for later use.
[0047] Step D22: Weigh 700g of the concentrated glucose extract, add ammonium sulfite and sodium metabisulfite catalyst in a mass ratio of 7% and 1:1, and mix to obtain a mixed solution.
[0048] Step D23: Adjust the pH of the mixed solution to 5.5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 115℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.5% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 6.
[0049] Step D24: After reacting for 3 hours, cool to room temperature to obtain the desired caramel coloring product.
[0050] The prepared caramel color product was subjected to relevant tests. The absorbance of the caramel color product in Example 1 was 0.058, the red finger was 5.80, and the salt resistance was unqualified. Using the total sulfur detection method specified in the national standard GB1886.64-2015, the total sulfur detection result was 2.7%.
[0051] Comparative Example 3 The third comparative example of preparing caramel color according to the present invention includes the following steps: Step D31: The xylose mother liquor and glucose mother liquor obtained by simulated moving bed separation are concentrated and evaporated and concentrated to 80% refractive index at 80℃ and -0.1MPa, and then set aside for later use.
[0052] Step D32: Weigh 700g of concentrated xylose extract and glucose extract separately and mix them. The xylose extract and glucose extract are weighed at a mass ratio of 6:4. Then add 15% ammonium sulfite catalyst by mass and mix to obtain a mixed solution.
[0053] Step D33: Adjust the pH of the mixed solution to 5.5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 135℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 30% sodium hydroxide to adjust the pH to 5.5.
[0054] Step D34: After reacting for 3 hours, cool to room temperature to obtain the desired caramel coloring product.
[0055] The prepared caramel color product was subjected to relevant tests. The absorbance of the caramel color product in Example 1 was 0.058, the red finger was 5.00, and the salt resistance was unqualified. Using the total sulfur detection method specified in the national standard GB1886.64-2015, the total sulfur detection result was 4.5%.
[0056] The main parameters for preparing caramel color products in Examples 1-3 and Comparative Examples 1-3 were compared, and the data table shown in Table 1 was obtained.
[0057] Table 1
[0058] Due to the significant advantages of this invention in terms of safety, quality, and environmental protection, the method for preparing low-total-sulfur caramel color is becoming a core direction for the upgrading of the caramel color industry. Firstly, this method promotes the diversification of raw materials from sucrose to xylose, glucose syrup, and others. For example, the cost of low-total-sulfur caramel color made from xylose mother liquor is 18% lower than that of sucrose-based products, while simultaneously driving value-added in the corn deep-processing industry. Secondly, in terms of market demand, with consumers' increasing focus on food safety and health, the demand for low-sulfur or sulfur-free food additives has increased significantly. Furthermore, the demand for natural, low-toxicity additives in emerging markets such as functional foods and organic foods further promotes the application of low-total-sulfur caramel color.
[0059] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.
Claims
1. A method for preparing low total sulfur caramel color, characterized in that, Includes the following steps: Step 1: The xylose mother liquor and glucose mother liquor obtained by separation in a simulated moving bed are evaporated and concentrated to 65%~80% refractive index, and then set aside. Step 2: Weigh the concentrated xylose extract and glucose extract separately according to a mass ratio of 7:3 to 6:4 and mix them. Then add 5% to 8% of a catalyst by mass to obtain a mixed solution. The catalyst is ammonium sulfite and sodium metabisulfite, with the ratio of ammonium sulfite to sodium metabisulfite being 1:1 to 1:
4. Step 3: Adjust the pH of the mixed solution to 5-6 using 30% sodium hydroxide, then add it to the reactor. Control the reaction temperature between 115-130℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches 0.035-0.038, add 0.5%-0.7% sodium metabisulfite by mass and add 30% sodium hydroxide to adjust the pH to 5-6. Step 4: Heat to 135~140℃, react for 2~3 hours, then cool to room temperature to obtain the desired caramel coloring product.
2. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, In step one, the xylose mother liquor contains, by mass percentage: xylose 11.2%~12.0%, mannose 4.0%~6.0%, glucose 26.0%~34.0%, arabinose 28.0%~31.0%, and other components 17.0%~31.0%.
3. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, In step one, the glucose mother liquor contains, by mass percentage: 78.0%~83.0% glucose, 5.0%~10.0% fructose, and 8.0%~12.0% other components.
4. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, In step two, the glucose extract contains, by mass percentage: 28.0% to 32.0% glucose, 40.0% to 45.0% fructose, and 25.0% to 30.0% other components.
5. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, In step two, the xylose extract contains, by mass percentage: xylose 2.0%~4.0%, mannose 6.0%~8.0%, glucose 35.0%~40.0%, arabinose 35.0%~40.0%, and other components 8.0%~22.0%.
6. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, Includes the following steps: Step 11: The xylose mother liquor and glucose mother liquor obtained by simulated moving bed separation are concentrated and evaporated to 70% refractive index at 80℃ and -0.1MPa for later use. Step 12: Weigh 700g of concentrated xylose extract and glucose extract separately and mix them. Weigh the xylose extract and glucose extract at a mass ratio of 6:
4. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 7% and 1:1 and mix to obtain a mixed liquid. Step 13: Adjust the pH of the mixture to 5.5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 115℃. During the reaction, check the absorbance of the reaction solution and monitor the pH every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.7% sodium metabisulfite and 30% sodium hydroxide to adjust the pH to 5.
5. Step 14: Heat to 135℃, react for 3 hours, then cool to room temperature to obtain the desired caramel coloring product.
7. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, Includes the following steps: Step 21: The xylose mother liquor and glucose mother liquor obtained by simulated moving bed separation are concentrated and evaporated to 65% refractive index at 80℃ and -0.1MPa for later use. Step 22: Weigh 700g of concentrated xylose extract and glucose extract separately and mix them. Weigh the xylose extract and glucose extract at a mass ratio of 6:
4. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 8% and 1:3 and mix to obtain a mixed liquid. Step 23: Adjust the pH of the mixture to 5 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 120℃. During the reaction, check the absorbance of the reaction solution and monitor the pH of the solution every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.7% sodium metabisulfite by mass and 30% sodium hydroxide to adjust the pH to 5. Step 24: Heat to 137℃, react for 2.5 hours, then cool to room temperature to obtain the desired caramel coloring product.
8. The method for preparing low total sulfur caramel color according to claim 1, characterized in that, Includes the following steps: Step 31: The xylose mother liquor and glucose mother liquor obtained by simulated moving bed separation are concentrated and evaporated and concentrated to 80% refractive index at 80℃ and -0.1MPa, and then set aside. Step 32: Weigh 700g of concentrated xylose extract and glucose extract separately and mix them. Weigh the xylose extract and glucose extract at a mass ratio of 7:
3. Then add ammonium sulfite and sodium metabisulfite catalyst at a mass ratio of 7% and 1:4 and mix to obtain a mixed liquid. Step 33: Adjust the pH of the mixed solution to 6 using 30% sodium hydroxide, then add it to a 1L reactor. Control the reaction temperature to 130℃. During the reaction, check the absorbance of the reaction solution and monitor the pH of the solution every half hour. When the absorbance reaches between 0.035 and 0.038, add 0.7% sodium metabisulfite by mass and add 30% sodium hydroxide to adjust the pH to 6. Step 34: Heat to 140℃, react for 2 hours, then cool to room temperature to obtain the desired caramel coloring product.