A method for reducing levulinic acid content in caramel color and its application

Abstract

The present invention discloses a method and application for reducing the content of levulinic acid in caramel. The method for reducing the content of levulinic acid in caramel provided by the present invention comprises the following steps: S1, making a syrup having a pH of 7 to 8 undergo a caramelization reaction in a reducing atmosphere, reacting to a chroma of 12000-17000EBC, and obtaining a preliminary caramel; S2, adjusting the pH of the preliminary caramel to 8 to 9, performing a secondary caramelization reaction in a reducing atmosphere, reacting to a pH of 5 to 7, and obtaining a caramel. The present invention is carried out by two caramelization reactions under alkaline conditions, so that levulinic acid is produced later and in less amount; meanwhile, the reaction is carried out in a reducing atmosphere, and levulinic acid can be deacetylated to generate ethanol and sodium propionate, thereby further reducing the content of levulinic acid in caramel, and ensuring that the caramel has good product quality, such as good red index and salt tolerance.

Description

Technical Field

[0001] The invention belongs to the technical field of caramel color production, and in particular relates to a method for reducing the content of levulinic acid in caramel color and application thereof. Background Art

[0002] Caramel color, also known as sauce color, is one of the food additives with the longest history of human use. It is widely used in a variety of foods such as soy sauce, vinegar, biscuits, beverages, candy, and alcohol. It is the most widely used food coloring in my country and plays an extremely important role in the food industry.

[0003] Caramel color is divided into four categories based on its production process: (I) conventional caramel color, (II) caustic sulfite caramel color, (III) ammonium caramel color, and (IV) ammonium sulfite caramel color. Conventional caramel color is the safest of the four caramel colors because it prohibits the use of sulfites and ammonia compounds during production, has very low residual SO₂ levels (less than 40 ppm), and does not produce 4-MI. Therefore, conventional caramel color is the safest of the four caramel colors and is permitted in most countries and regions of the world for addition to a wide range of foods. my country's current "National Food Safety Standard for the Use of Food Additives" (GB2760) stipulates that conventional caramel color can be used in a variety of foods, including biscuits, soy sauce, vinegar, beverages, blended alcoholic beverages, and jellies. In most foods, it can be used in appropriate amounts according to production requirements. Furthermore, conventional caramel color has good water solubility, a high redness index, a bright red color, and excellent stability, making it widely used in dark soy sauce.

[0004] Existing technology uses the levulinic acid content in soy sauce products to distinguish between brewed soy sauce and formulated soy sauce with added acid-hydrolyzed vegetable protein liquid. If the levulinic acid content in brewed soy sauce exceeds 0.1% (i.e., 1000 ppm), it is considered formulated soy sauce with added "acid-hydrolyzed vegetable protein seasoning liquid." my country has also considered using this method to distinguish brewed soy sauce from formulated soy sauce. However, due to the raw materials and reaction process, the caramelization reaction of conventional caramel color inevitably produces furfural and furfuryl alcohol, which inevitably leaves residual levulinic acid. The levulinic acid content of commercially available caramel color ranges from 6000 to 15000 ppm. Therefore, there is a need to find a method to effectively reduce the levulinic acid content of conventional caramel color. Summary of the Invention

[0005] In order to overcome the problems existing in the prior art, one of the objects of the present invention is to provide a method for reducing the content of levulinic acid in caramel color.

[0006] A second object of the present invention is to provide an application of the above method in the food field.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] A first aspect of the present invention provides a method for reducing the levulinic acid content in caramel color, comprising the following steps:

[0009] S1. Caramelizing the syrup at a pH of 7 to 8 in a reducing atmosphere until the color reaches 12000-17000 EBC to obtain a preliminary caramel color.

[0010] S2. Adjust the pH of the preliminary caramel color to 8-9, and perform a secondary caramelization reaction in a reducing atmosphere until the pH reaches 5-7 to obtain caramel color.

[0011] The inventive concept of the present invention is that, since reducing sugars generate 1,2-enol hexoses under alkaline conditions, further heating and reaction can cleave to generate enol trioses, glyceraldehyde, and hydrated methylglyoxal, which then undergo a one-step condensation reaction to produce melanin and organic acid compounds, the pH of the material decreases accordingly. Reducing sugars generate 1,2-enol hexoses under acidic conditions, which then undergo a series of dehydration reactions to generate furfural, which then undergoes hydrolysis, ring opening, and rearrangement to generate levulinic acid. Therefore, reacting under alkaline conditions can help reduce the levulinic acid content in caramel color. However, if the reaction pH is maintained at alkaline conditions, product quality, such as water solubility and salt tolerance, will be affected. Therefore, the present invention conducts the reaction initially under weakly alkaline conditions, which can delay the production of levulinic acid and reduce the amount produced. The second reaction under alkaline conditions can further reduce the levulinic acid content in the caramel color. Furthermore, the caramelization reaction of the present invention is carried out in a reducing atmosphere, which can deacetylate the levulinic acid in the caramel color to produce ethanol and sodium propionate, thereby reducing the levulinic acid content in the caramel color.

[0012] Furthermore, the method is to reduce the levulinic acid content in conventional caramel color.

[0013] Preferably, the reducing atmosphere is selected from a hydrogen atmosphere.

[0014] The present invention adopts hydrogen as a reducing agent, which can deacetylate the levulinic acid in the caramel color and effectively reduce the levulinic acid in the caramel color.

[0015] Preferably, the reducing atmosphere contains only reducing gases.

[0016] Preferably, the temperature of the primary caramelization reaction is 110-130°C; more preferably 115-125°C.

[0017] Preferably, the temperature of the secondary caramelization reaction is 115-140°C; more preferably 120-135°C.

[0018] Preferably, the temperature of the secondary caramelization reaction is higher than that of the primary caramelization reaction; further preferably, the temperature of the secondary caramelization reaction is 5-15° C. higher than that of the primary caramelization reaction.

[0019] Preferably, the primary caramelization reaction and the secondary caramelization reaction are each independently carried out in a closed environment.

[0020] The present invention can also meet the requirement of reducing levulinic acid under normal pressure, but because the container is not airtight, it is necessary to continue to pass through hydrogen to achieve the desired effect. And continuing to pass through and discharge hydrogen is unfavorable for production safety, while significantly increasing production cost. Therefore, the present invention reacts under a closed environment, allowing the reaction to be carried out under the condition of only containing reducing gas (such as hydrogen).

[0021] Preferably, the gauge pressure of the primary caramelization reaction and the secondary caramelization reaction are each independently 0.01 to 0.1 MPa; more preferably 0.02 to 0.05 MPa.

[0022] The present invention introduces reducing gas before the reaction and continues to introduce reducing gas to maintain a certain pressure after sealing, ensuring that the reaction is carried out under conditions containing only reducing gas, which is conducive to better deacetylation, while ensuring production safety and reducing production costs. The gauge pressure described in the present invention is the pressure difference between absolute pressure and atmospheric pressure.

[0023] Preferably, the syrup comprises at least one of white sugar, glucose, fructose, maltose or xylose.

[0024] Preferably, in step S1, the pH adjuster for adjusting the pH of the syrup to 7-8 is a Lewis base; further preferably, the Lewis base includes at least one of sodium acetate, sodium citrate or sodium phosphate.

[0025] Lewis bases such as sodium acetate, sodium citrate, and sodium phosphate have weak buffering capacity and can keep the reaction weakly alkaline in the initial stage.

[0026] Preferably, in step S1, the pH of the syrup is 7.2 to 7.9; more preferably, 7.5 to 7.8.

[0027] Preferably, in step S1, the reaction is carried out until the color reaches 13000-16000 EBC; more preferably, 14000-15000 EBC.

[0028] Preferably, in step S2, the pH of the preliminary caramel color is adjusted to 8 to 8.8; more preferably, 8 to 8.5.

[0029] Preferably, the pH of the secondary caramelization reaction is greater than the pH of the primary caramelization reaction; further preferably, the pH of the secondary caramelization reaction is 0.5 to 1 higher than the pH of the primary caramelization reaction.

[0030] Preferably, in step S2, the reaction is performed until the pH is 5.5 to 6.5; more preferably, 6 to 6.2.

[0031] Preferably, in step S2, the pH adjuster for adjusting the initial caramel color to a pH of 8 to 9 is an alkaline substance; more preferably, an alkali; and even more preferably, sodium hydroxide or potassium hydroxide. Step S2 does not need to maintain a weak alkaline state; therefore, an alkaline substance can be used to adjust the material to a pH of 8 to 9.

[0032] The number of caramelization reactions in the present invention is not limited to two. However, after two caramelization reactions, the levulinic acid content reaches the required level, so further reactions are unnecessary. If a lower levulinic acid content is desired, more than two caramelization reactions may be performed, and the subsequent caramelization reaction conditions are the same as those for the second caramelization reaction.

[0033] The second aspect of the present invention provides an application of the method described in the first aspect of the present invention in the food field.

[0034] Preferably, the food comprises at least one of biscuits, soy sauce, vinegar, beverages, blended liquor or jelly.

[0035] The beneficial effects of the present invention are as follows: the present invention causes levulinic acid to be produced later and in a smaller amount through two caramelization reactions under alkaline conditions; at the same time, the reaction is carried out in a reducing atmosphere, which can deacetylate the levulinic acid to produce ethanol and sodium propionate, thereby further reducing the levulinic acid content in the caramel color and ensuring that the caramel color has better product quality, such as a better red index and salt tolerance.

[0036] Specifically, compared with the prior art, the present invention has the following advantages:

[0037] 1. The primary caramelization reaction of the present invention is carried out under weak alkaline conditions, which can cause levulinic acid to be produced later and in a smaller amount. Moreover, the reaction is carried out under conditions containing only reducing gases such as hydrogen, which is conducive to better deacetylation and reduces the levulinic acid in the caramel color to within 2000 ppm.

[0038] 2. The secondary caramelization reaction of the present invention is carried out under alkaline conditions containing only reducing gases, further reducing the levulinic acid content in the caramel color. Experiments have shown that the levulinic acid content of conventional caramel color produced by the present invention can be reduced to less than 1000 ppm.

[0039] 3. The reaction of the present invention is carried out in a closed environment, ensuring that the reaction is carried out under conditions containing only reducing gas, which is conducive to better deacetylation, while ensuring production safety and reducing production costs. DETAILED DESCRIPTION

[0040] The content of the present invention is further described in detail below through specific examples. It should be understood that the following examples are only used to further illustrate the present invention and cannot be interpreted as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the principles set forth in the present invention all fall within the scope of protection of the present invention. The specific process parameters and the like in the following examples are only examples within a suitable range, and those skilled in the art can make selections within a suitable range through the description herein, and are not limited to the specific data exemplified below. The raw materials, reagents or devices used in the following examples and comparative examples, unless otherwise specified, can be obtained from conventional commercial sources, or can be obtained by existing known methods.

[0041] The embodiment of the present invention is described by producing 36Be, 15000EBC common method caramel color (EBC is the color rate unit of caramel color; Be refers to the Baume value of caramel color, and color rate and Baume are both measurement indicators of caramel color).

[0042] Example 1

[0043] A process for reducing the levulinic acid content in conventional caramel color comprises the following steps:

[0044] 1) Metering and feeding of raw syrup: Measuring fructose syrup and pumping it into the reactor;

[0045] 2) Adding Lewis base: Add an appropriate amount of sodium acetate to the reactor and adjust the pH to 7.50;

[0046] 3) Introduction of hydrogen: hydrogen was introduced into the reactor, and after the air in the reactor was exhausted, the reactor was sealed and hydrogen was continued to be introduced until the apparent pressure reached 0.02 MPa;

[0047] 4) Primary caramelization reaction: heat to 115°C, react until the color yield reaches 15,000 EBC, release the pressure, cool, and terminate the reaction;

[0048] 5) Neutralization: Cool the terminated reaction material and add alkali to adjust the pH to 8.0;

[0049] 6) Re-introducing hydrogen: Introduce hydrogen into the reactor, expel the air from the reactor, seal the reactor, and continue to introduce hydrogen until the apparent pressure reaches 0.02 MPa;

[0050] 7) Secondary caramelization reaction: heating to 120°C and continuing the reaction until the pH reaches 6.2;

[0051] 8) Terminate the reaction: release the pressure, cool, and mix to obtain caramel color.

[0052] Example 2

[0053] A process for reducing the levulinic acid content in conventional caramel color comprises the following steps:

[0054] 1) Raw material syrup metering feed: glucose syrup is metered and pumped into the reactor;

[0055] 2) Adding Lewis base: Add an appropriate amount of sodium citrate to the reactor and adjust the pH to 7.65;

[0056] 3) Introduction of hydrogen: hydrogen was introduced into the reactor, and after the air in the reactor was exhausted, the reactor was sealed and hydrogen was continued to be introduced until the apparent pressure reached 0.04 MPa;

[0057] 4) Primary caramelization reaction: heating to 120°C until the color yield reaches 15,000 EBC, releasing the pressure, cooling, and terminating the reaction;

[0058] 5) Neutralization: Cool the terminated reaction material and add alkali to adjust the pH to 8.3;

[0059] 6) Re-introducing hydrogen: Introduce hydrogen into the reactor, expel the air from the reactor, seal the reactor, and continue to introduce hydrogen until the apparent pressure reaches 0.03 MPa;

[0060] 7) Secondary caramelization reaction: heating to 130°C and continuing the reaction until the pH reaches 6.1;

[0061] 8) Terminate the reaction: release the pressure, cool, and mix to obtain caramel color.

[0062] Example 3

[0063] A process for reducing the levulinic acid content in conventional caramel color comprises the following steps:

[0064] 1) Metering and feeding of raw syrup: Measuring xylose syrup and pumping it into the reactor;

[0065] 2) Adding Lewis base: Add an appropriate amount of sodium phosphate to the reactor and adjust the pH to 7.8;

[0066] 3) Introduction of hydrogen: hydrogen was introduced into the reactor, and after the air in the reactor was exhausted, the reactor was sealed and hydrogen was continued to be introduced until the apparent pressure reached 0.05 MPa;

[0067] 4) Primary caramelization reaction: heating to 125°C until the color yield reaches 15,000 EBC, releasing the pressure, cooling, and terminating the reaction;

[0068] 5) Neutralization: Cool the terminated reaction material and add alkali to adjust the pH to 8.5;

[0069] 6) Re-introducing hydrogen: Introduce hydrogen into the reactor, expel the air from the reactor, seal the reactor, and continue to introduce hydrogen until the apparent pressure reaches 0.05 MPa;

[0070] 7) Secondary caramelization reaction: heating to 135°C and continuing the reaction until the pH reaches 6.0;

[0071] 8) Terminate the reaction: release the pressure, cool, and mix to obtain caramel color.

[0072] Comparative Example 1

[0073] This comparative example is based on Example 1, and differs from Example 1 in that: hydrogen is not introduced in step 3), that is, the primary caramelization reaction is carried out under pressurized conditions without hydrogen introduction, and the other steps and conditions are carried out according to Example 1.

[0074] Comparative Example 2

[0075] This comparative example is based on Example 2, and differs from Example 2 in that: hydrogen is not introduced in step 6), that is, the secondary caramelization reaction is carried out under pressurized conditions without hydrogen, and the other steps and conditions are carried out according to Example 2.

[0076] Comparative Example 3

[0077] This comparative example is based on Example 3, and differs from Example 3 in that the secondary caramelization reaction is carried out under acidic conditions with a pH value of less than 7.0, and the other steps and conditions are carried out according to Example 3.

[0078] Performance Testing

[0079] 1. Use fluorescence spectrophotometry to determine the red index. The calculation formula is as follows: Red index is the OD value of the sample at 510 nm, is the OD value of the sample at 610 nm.

[0080] 2. According to the national standard GB 5009.252-2016 "Determination of Levulinic Acid in Foods with National Food Safety Labeling," the levulinic acid content in the caramel-colored products of Examples 1 to 3 and Comparative Examples 1 to 3 was determined. The results are shown in Table 1 below.

[0081] Table 1 Levulinic acid content in caramel products of Examples 1 to 3 and Comparative Examples 1 to 3

[0082]

[0083] As can be seen from Table 1, under similar solid content and color rate conditions, the levulinic acid content in the caramel color products obtained in Comparative Examples 1 to 3 is much higher than the levulinic acid content in Examples 1 to 3. It can be seen that the method of the present invention can effectively reduce the levulinic acid content in conventional caramel color.

[0084] The primary caramelization reaction of the present invention is carried out under weakly alkaline conditions, which can make levulinic acid produced later and in a smaller amount, and the reaction is carried out under conditions containing only reducing gases such as hydrogen, which is conducive to better deacetylation and reduces the levulinic acid in the caramel color to within 2000ppm. The secondary caramelization reaction of the present invention is maintained under alkaline conditions containing only reducing gases, which can further reduce the levulinic acid in the caramel color. Experiments have shown that the conventional caramel color produced by the present invention can reduce the levulinic acid content to within 1000ppm. The reaction of the present invention is carried out in a closed environment, which ensures that the reaction is carried out under conditions containing only reducing gases, is conducive to better deacetylation, and simultaneously ensures production safety and reduces production costs.

[0085] The present invention causes levulinic acid to be produced later and in a smaller amount through two caramelization reactions under alkaline conditions. At the same time, the reaction is carried out in a reducing atmosphere, which can deacetylate the levulinic acid to produce ethanol and sodium propionate, thereby further reducing the levulinic acid content in the caramel color and ensuring that the caramel color has better product quality, such as a higher red index and better salt tolerance.

Claims

1. A method for reducing the content of levulinic acid in caramel color, characterized in that: The following steps are involved: S1. Caramelizing the syrup at a pH of 7.2 to 7.9 in a reducing atmosphere until the chroma reaches 12,000 to 17,000 EBC to obtain a preliminary caramel color. S2. Cooling the preliminary caramel color, adjusting the pH of the cooled preliminary caramel color to 8-9, and performing a secondary caramelization reaction in a reducing atmosphere until the pH reaches 5-7 to obtain a caramel color.

2. The method according to claim 1, characterized in that The reducing atmosphere is selected from a hydrogen atmosphere.

3. The method according to claim 1, characterized in that The temperature of the primary caramelization reaction is 110-130°C.

4. The method according to claim 1, wherein The temperature of the secondary caramelization reaction is 120-140°C.

5. The method according to claim 1, wherein The primary caramelization reaction and the secondary caramelization reaction are each independently carried out in a closed environment.

6. The method according to claim 5, characterized in that The gauge pressures of the primary caramelization reaction and the secondary caramelization reaction are each independently 0.02 to 0.05 MPa.

7. The method according to claim 1, characterized in that The syrup comprises at least one of white sugar, glucose, fructose, maltose or xylose.

8. The method according to claim 1, characterized in that In step S1, the pH of the syrup is adjusted to 7.2-7.9 using a Lewis base as the pH adjuster.

9. The method according to claim 8, characterized in that The Lewis base includes at least one of sodium acetate, sodium citrate or sodium phosphate.

10. Use of the method according to any one of claims 1 to 9 in the food field.

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