A method for efficient basification of cocoa powder

Abstract

The application belongs to the field of food processing, and particularly relates to a high-efficiency alkalinization method for cocoa powder, which comprises the following steps: completely mixing cocoa powder with water to obtain a cocoa powder aqueous solution, adding NaOH solution to adjust the pH of the system to 6.8-9.2 to perform alkalinization, immediately using microwave heating, wherein the microwave heating power is 380-700 W, the microwave heating time is 5-15 min, immediately placing the system in an ice water bath to cool after the heating is completed, and then performing freeze drying, so that alkalinized cocoa powder is finally obtained. The alkalinized cocoa powder prepared by the method has brown color, retains more phytochemical substances (epicatechin, catechin, theobromine, etc.), has stronger antioxidant capacity, and has better flavor, and can be widely applied in the field of food processing, such as beverage, baking, dessert and candy making.

Description

Technical Field

[0001] This invention belongs to the field of food processing, specifically relating to a method for the efficient alkalization of cocoa powder. Background Technology

[0002] Cocoa is an ingredient and raw material extracted from the fruit of the cacao tree (Theobroma cacao). It requires a series of complex processing steps to be made into a product, including fermentation, drying, roasting and alkalization. These steps have an important impact on the flavor, color and health of the final product.

[0003] The raw materials for the alkalization step can be a series of intermediate products in cocoa processing, such as cocoa powder, cocoa beans, and cocoa liquor. Among these, cocoa powder is an important alkalization raw material due to its low fat content and easy-to-control processing. Alkalization is a crucial step in cocoa processing. It involves using alkaline substances (such as sodium hydroxide and potassium carbonate) to change the pH value of the cocoa powder, and then promoting a chemical reaction at a certain temperature. This affects the color, flavor, and solubility of the cocoa, improving its sensory quality and functionality, making it more suitable for various applications. However, existing cocoa powder alkalization processes generally suffer from long heat treatment times and damage to nutritional components.

[0004] Depending on the degree of alkalization, the color of alkalized cocoa powder changes from its natural light brown to red or black. At the same time, polyphenols, represented by flavanols (catechins), and alkaloids are reduced to some extent. However, although the content of these phytochemicals, especially catechins and epicatechins, is reduced after alkalization, they still retain certain beneficial effects. In recent years, cocoa products have received considerable attention in the fields of medicine and nutrition. Therefore, controlling the quality of alkalized cocoa powder is particularly important.

[0005] In the existing technology of alkalization using cocoa powder, patent CN101502292A provides an alkalization method for controlling the color and flavor of cocoa powder. It uses cocoa kernels or cocoa powder as raw materials, adds potassium carbonate solution, alkalizes under pressure, then bakes at high temperature, and finally grinds and sieves to obtain alkalized powder with a mesh size of less than or equal to 60 mesh. The alkalization neutralizes the sour taste of cocoa powder and makes its color consistent and uniform, thus improving its flavor and quality. However, this method uses pressure conditions and only focuses on the color change of cocoa powder after alkalization.

[0006] In their study on the effects of alkalization conditions on the color of cocoa powder (China Oils & Fats, 2020), Xu et al. investigated the effects of temperature, pressure, alkalization time, and concentration of alkalization solution on the color of alkalized cocoa powder. However, the drying process after alkalization used an oven drying at 130℃. Oven drying at high temperatures can cause further changes in the color of alkalized cocoa powder, which increases the interference with the evaluation of the color of alkalized cocoa powder.

[0007] In her study on the alkalization process of cocoa kernels / powder (Jiangnan University, 2008), Feng Yun first investigated the relationship between different alkalization conditions and the color of cocoa powder after alkalization, and then preliminarily explored the influence of alkalization conditions on the flavor of cocoa powder. However, this article also mainly carried out alkalization under pressure, used a mixture of various alkali solutions, and when exploring the influence of alkalization conditions on the flavor of cocoa powder, only potassium carbonate solution was used to change the pH value of cocoa powder. At the same time, when exploring the relationship between alkalization conditions and the flavor of cocoa powder, she only tested the chemical substances related to the color and smell of cocoa powder, and did not pay attention to the changes in the beneficial components of cocoa powder after alkalization, nor did she explore the influence of the alkalization method on the quality of cocoa powder.

[0008] In summary, existing technologies suffer from long heating times, damage to nutritional components, cumbersome alkalization steps under pressure, the use of multiple alkali solutions for alkalization, difficulty in controlling and detecting the pH value of the alkalization solution, and the lack of comprehensive indicators, such as the color, nutritional components, and antioxidant capacity of the alkalized cocoa powder, to control the quality of cocoa powder. Summary of the Invention

[0009] To address the aforementioned technical problems, this invention uses cocoa powder as a raw material and employs a single sodium hydroxide solution for alkalization under normal pressure, providing a preparation method that can improve the retention rate of effective components in cocoa powder. Compared to potassium carbonate solution, alkalization with sodium hydroxide solution can more effectively adjust the pH value of cocoa powder, reduce its acidity, improve its flavor, and increase its solubility; therefore, this invention selects sodium hydroxide solution.

[0010] This invention also utilizes microwave heating to assist alkalization. The microwave field direction changes continuously at extremely high frequencies, causing the electric dipoles in water molecules to attempt to rotate rapidly in the direction of the electric field. Due to the constantly changing electric field direction, the dipoles rotate rapidly and generate friction, directly generating heat. Similarly, the rapid movement and oscillation of Na+ and OH- ions in the microwave field intensifies friction and collisions in the solution, generating additional heat energy. The ionic conductivity further enhances the effect of microwave heating. This dual heating mechanism makes the heating speed faster and more uniform, significantly shortening the heating time and minimizing the damage to nutrients. Simultaneously, microwaves directly act on the water-containing parts or other polar molecules in cocoa powder, making the vibration and rotation of these molecules more intense. This molecular-level activation effectively reduces the energy barrier required for the reaction and accelerates the reaction rate. Furthermore, the penetrability of microwaves ensures that the cocoa powder heats up simultaneously inside and out, unlike traditional heating methods that rely on heat conduction and are prone to the phenomenon of high external temperature and low internal temperature. This uniform heating characteristic is particularly important for the alkalization process because it allows all parts of the cocoa powder to react under the same conditions, ensuring consistent alkalization effects and improving the uniformity of product quality.

[0011] This invention uses ultra-high performance liquid chromatography-high resolution mass spectrometry to analyze the phytochemical components of unalkalized and alkalized cocoa powder, and detects indicators such as pH and antioxidant capacity of cocoa powder, and provides a comprehensive evaluation of the effective components of alkalized cocoa powder.

[0012] Color changes during alkalization typically indicate changes in the structure and content of polyphenolic compounds (especially flavonoids). Studies have identified polar or nonpolar chromophores during cocoa alkalization. Catechins and their free radical-derived 6'-hydroxycatechins are the main causes of the reddish-brown color. Therefore, catechins and other polyphenols are considered potential markers of alkalization. Flavonoids possess strong antioxidant capabilities, can lower blood lipids and cholesterol, promote blood circulation, improve blood flow, and have preventative and therapeutic effects on certain cancers. Therefore, by analyzing color changes before and after cocoa alkalization, we can infer trends in the content of polyphenolic compounds (especially flavonoids) and thus assess how these changes affect the health benefits of cocoa products.

[0013] To achieve the above-mentioned technical effects, the first objective of this invention is to provide an alkalization method for cocoa powder, comprising the following steps:

[0014] (1) Mix cocoa powder with water to obtain a cocoa powder aqueous solution;

[0015] (2) Add NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system;

[0016] (3) Microwave heating is performed on the cocoa powder aqueous solution after the pH of the system is adjusted in step (2). The microwave heating power is 380-700W and the microwave heating time is 5-15min (equivalent to continuous heating to 60-110℃). After heating, the solution is immediately placed in an ice water bath to cool and then freeze-dried to finally obtain alkalized cocoa powder.

[0017] Further, the mass-to-volume ratio of cocoa powder to deionized water in step (1) is 1:3-1:20 (g:mL);

[0018] Preferably, the mass-to-volume ratio of cocoa powder to deionized water is 1:5-1:13.

[0019] Furthermore, the conditions for the cocoa powder to be completely dissolved in water in step (1) are to stir at 100-900 rpm for 3-10 minutes at 15-30℃.

[0020] Preferably, the cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 500-700 rpm for 4-6 minutes at 20-25°C.

[0021] Furthermore, the concentration of the NaOH solution in step (2) is 1-10M, and the pH of the system is adjusted to 7.5-8.5;

[0022] Preferably, the concentration of the NaOH solution in step (2) is 3-5M, and the pH of the system is adjusted to 7.8-8.3.

[0023] Further, in step (2), the pH of the system is adjusted while stirring, with a stirring speed of 100-900 rpm and a stirring time of 3-10 min;

[0024] Preferably, in step (2), the pH of the system is adjusted while stirring, with a stirring speed of 500-700 rpm and a stirring time of 4-6 min.

[0025] Preferably, in step (3), the microwave heating power is 500-600W and the microwave heating time is 8-12min, which is equivalent to continuous heating to 90-100℃.

[0026] Preferably, the microwave heating power in step (3) is suitable for materials with a mass of 1g-500g. If the mass of the material changes, the microwave parameters need to be adjusted so that the effect after microwave heating is comparable to the effect of the above-mentioned addition amount.

[0027] The results showed that the prepared alkalized cocoa powder was brown in color, with a moderate degree of alkalization. It retained a large amount of phytochemicals (epicatechin, catechin, theobromine, etc.), had strong antioxidant capacity, and excellent flavor. It can be widely used in food processing fields such as beverages, baking, desserts, and candy making.

[0028] The second objective of this invention is to provide a method for increasing the retention of active ingredients in cocoa powder, comprising the following steps:

[0029] (1) Mix cocoa powder with water to obtain a cocoa powder aqueous solution;

[0030] (2) Add NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system;

[0031] (3) Microwave heating is performed on the cocoa powder aqueous solution after the pH of the system is adjusted in step (2). The microwave heating power is 380-700W and the microwave heating time is 5-15min (equivalent to continuous heating to 60-110℃). After heating, the solution is immediately placed in an ice water bath to cool and then freeze-dried to finally obtain alkalized cocoa powder.

[0032] Further, the mass-to-volume ratio of cocoa powder to deionized water in step (1) is 1:3-1:20 (g:mL);

[0033] Preferably, the mass-to-volume ratio of cocoa powder to deionized water is 1:5-1:13.

[0034] Furthermore, the conditions for the cocoa powder to be completely dissolved in water in step (1) are to stir at 100-900 rpm for 3-10 minutes at 15-30℃.

[0035] Preferably, the cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 500-700 rpm for 4-6 minutes at 20-25°C.

[0036] Furthermore, the concentration of the NaOH solution in step (2) is 1-10M, and the pH of the system is adjusted to 7.5-8.5;

[0037] Preferably, the concentration of the NaOH solution in step (2) is 3-5M, and the pH of the system is adjusted to 7.8-8.3.

[0038] Further, in step (2), the pH of the system is adjusted while stirring, with a stirring speed of 100-900 rpm and a stirring time of 3-10 min;

[0039] Preferably, in step (2), the pH of the system is adjusted while stirring, with a stirring speed of 500-700 rpm and a stirring time of 4-6 min.

[0040] Preferably, in step (3), the microwave heating power is 500-600W and the microwave heating time is 8-12min, which is equivalent to continuous heating to 90-100℃.

[0041] The results showed that the prepared alkalized cocoa powder was brown in color, with a moderate degree of alkalization. It retained a large amount of phytochemicals (epicatechin, catechin, theobromine, etc.), had strong antioxidant capacity, and excellent flavor. It can be widely used in food processing fields such as beverages, baking, desserts, and candy making.

[0042] Beneficial effects

[0043] 1. Polyphenolic compounds degrade significantly faster when heated above 80°C, leading to a substantial decrease in their content; this phenomenon is particularly pronounced at temperatures above 90°C. This invention utilizes microwave heating to assist in the alkalization of cocoa powder. Heating for 10 minutes at a microwave power of 540W, as used in Example 1 of this invention, is equivalent to continuous heating to 90°C. This microwave heating is faster and more uniform, significantly shortening the processing time of the cocoa powder and minimizing the damage to its nutrients (such as polyphenolic compounds).

[0044] 2. The microwave heating of this invention shortens the alkalization reaction time, significantly reduces energy consumption, improves the operating efficiency of the production line, and further reduces production costs, making this process highly economical in large-scale commercial production.

[0045] 3. In the method of the present invention, after microwave heating is completed, the cocoa powder after alkalization is rapidly cooled using an ice-water bath. This can immediately terminate the reaction and prevent the occurrence of side reactions at high temperatures, thus maintaining the purity and quality of the cocoa powder after alkalization as much as possible. At the same time, it can speed up the entire production process and improve production efficiency.

[0046] 4. This invention uses cocoa powder as raw material and adopts normal pressure conditions during the alkalization process, which simplifies the alkalization steps, eliminates the need for complicated parameter settings, and is more suitable for large-scale production.

[0047] 5. This invention uses a single sodium hydroxide solution for alkalization, which makes it easy to control and detect the pH value of the alkalization solution, making the conditions of the alkalization process more precisely controlled. Compared with traditional alkalization, the alkalization time is shorter, the amount of alkali consumed is less, and the efficiency is higher.

[0048] 6. This invention uses ultra-high performance liquid chromatography-high resolution mass spectrometry to analyze the phytochemical components of unalkalized and alkalized cocoa powder, and detects indicators such as pH and antioxidant capacity of cocoa powder, so as to comprehensively evaluate the quality and nutritional value of alkalized cocoa powder. Detailed Implementation

[0049] The preferred embodiments of the present invention are described below. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0050] The test methods involved in the following embodiments are as follows:

[0051] I. Methods for determining the color of cocoa powder:

[0052] Take 3g of cocoa powder and spread it evenly in a petri dish. Use a colorimeter to measure the color of the cocoa powder. In this invention, the color measurement parameters L*, a*, and b* are selected as the evaluation criteria: these parameters represent brightness (L*), red-green balance (a*), and yellow-blue balance (b*), respectively.

[0053] II. Methods for pH measurement:

[0054] Take 1g of cocoa powder and stir it in 9mL of distilled water until a lump-free suspension is formed. After filtration, measure the pH of the sample using a calibrated pH meter.

[0055] III. Methods for determining the content of phytochemicals:

[0056] The content of the analyte is calculated by measuring the peak area or peak height ratio of the internal standard and the analyte using high performance liquid chromatography tandem high resolution mass spectrometry.

[0057] IV. Methods for determining antioxidant capacity:

[0058] The alkalized cocoa powder was defatted using hexane extraction. The defatted cocoa powder was then extracted with 80% methanol (defatting reduces fat interference, improves column life, separation efficiency, and analytical sensitivity, ensuring more accurate and reliable results). The extracted cocoa powder was then shaken and mixed thoroughly with 0.1 mM DPPH solution. After reacting in the dark for 15 min, the absorbance was measured at 517 nm. Simultaneously, a certain amount of the 80% methanol-treated defatted cocoa powder was vortexed and mixed with 7 mM ABTS solution. After reacting in the dark for 6 min, the absorbance was measured at 734 nm. The antioxidant capacity of the alkalized cocoa powder was then obtained.

[0059] Raw materials and equipment involved in the embodiments:

[0060] The cocoa powder used in the following examples was purchased from Tianjin Xiang'er Food Co., Ltd., item number 00285.

[0061] Example 1: A method for efficient alkalization of cocoa powder

[0062] (1) Mix cocoa powder and deionized water at a mass-to-volume ratio of 1:9 (g:mL) and stir at 600 rpm for 5 minutes at room temperature to completely dissolve the cocoa powder in the water.

[0063] (2) Add 1.1 mL of 4M NaOH solution to adjust the pH of the system to 8.0, and continue stirring at 600 rpm for 5 min;

[0064] (3) After stirring, microwave heating is used immediately. The microwave heating power is 540W. After microwave heating for 10 minutes (equivalent to continuous heating to 90℃), the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, finally obtaining alkalized cocoa powder.

[0065] Table 1. Results of color and nutritional value of cocoa powder after alkalization.

[0066]

[0067] The results are shown in Table 1. As can be seen from Table 1, the alkalized cocoa powder prepared in this embodiment is brown in color, retains more phytochemicals (epicatechin, catechin, theobromine, etc.), has strong antioxidant capacity, and has a better flavor. It can be widely used in food processing fields such as beverages, baking, desserts and candy making.

[0068] Example 2: Optimization of an efficient alkalization method for cocoa powder

[0069] This embodiment optimized the amount of alkali added; other parameters and conditions were the same as in Example 1.

[0070] (1) Mix cocoa powder and deionized water at a mass-volume ratio of 1:9 (g:mL) and stir at 600rpm for 5min at room temperature to completely dissolve the cocoa powder in the water.

[0071] (2) Add 0.6 mL, 1.1 mL, and 1.6 mL of 4 M NaOH solution respectively to adjust the pH of the system to 6.8, 8.0, and 9.2 respectively, and continue stirring at 600 rpm for 5 min;

[0072] (3) After stirring, microwave heating is used immediately. The microwave heating power is set to 540W and 700W respectively. After heating for 10 minutes, the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, finally obtaining alkalized cocoa powder.

[0073] Table 2 Results of Optimization of Alkali Dosage in High-Efficiency Alkalinization Method for Cocoa Powder

[0074]

[0075] Note: Alkali concentration refers to the mass of NaOH solids in the added NaOH solution: the mass of cocoa powder; temperature refers to the temperature equivalent to continuous heating at the corresponding microwave power and microwave time.

[0076] NaOH plays a crucial role in the alkalization process of cocoa powder. The amount of alkali added directly affects the acidity of the cocoa powder. By adding an appropriate amount of alkaline substance, the acidic components in the cocoa powder can be effectively neutralized, improving the taste. Simultaneously, adding an appropriate amount of alkali can deepen the color of the cocoa powder, resulting in a more appealing brown or dark brown hue. It can also improve the solubility and dispersibility of cocoa powder in water, broadening its applications. However, excessive alkali addition may have adverse effects on human health. Therefore, in this embodiment, the NaOH concentration is controlled within the range of 0.96%-2.56%.

[0077] The results of this embodiment are shown in Table 2:

[0078] According to GB / T 20706-2023 Quality Requirements for Cocoa Powder, cocoa powder with an alkali concentration of 0.96% is lightly alkalized cocoa powder; cocoa powder with an alkali concentration of 1.76% is mediumly alkalized cocoa powder; and cocoa powder with an alkali concentration of 2.56% is heavily alkalized cocoa powder.

[0079] Specifically:

[0080] (1) When the alkali concentration is 0.96%, the alkalized cocoa powder reaches the degree of light alkalization and the color is light brown. At this time, the phytochemicals (epicatechin, catechin, theobromine, etc.) are less damaged and have stronger antioxidant capacity. While meeting the requirements for application in red coating, baking, ice cream, etc., the damage to the nutrients in cocoa powder is minimized.

[0081] (2) When the alkali concentration is 1.76%, the alkalized cocoa powder reaches the degree of medium alkalization, and the color is brown. The degree of damage to phytochemicals (epicatechin, catechin, theobromine, etc.) is still at a low level, but the antioxidant capacity is strong. At this time, the alkalized cocoa powder has a better flavor and can be used for the production of hot chocolate, brewing, coating, ice cream, baking cakes, etc.

[0082] (3) When the alkali concentration is 2.56%, the alkalized cocoa powder reaches the degree of heavy alkalization, and the color is dark brown. The phytochemicals are more severely damaged. However, the resulting product has a wider range of applications and can be used to make hot chocolate, baked cakes, chocolate candies, etc.

[0083] In summary, the optimal alkali concentration is 1.76%. At this concentration, the cocoa powder turns brown after alkalization, exhibits strong antioxidant capacity, and suffers less damage to nutrients such as epicatechin, catechin, epigallocatechin gallate, and tyramine. Applications include the production of hot chocolate, brewing, coatings, ice cream, and baked cakes.

[0084] Example 3: Optimization of an efficient alkalization method for cocoa powder

[0085] This embodiment optimizes the microwave power; other parameters are the same as in Embodiment 1.

[0086] (1) Mix cocoa powder and deionized water at a mass-volume ratio of 1:9 (g:mL) and stir at 600 rpm for 5 min at room temperature to completely dissolve the cocoa powder in the water;

[0087] (2) Add 1.1 mL of 4M NaOH solution to adjust the pH of the system to 8.0, and continue stirring at 600 rpm for 5 min;

[0088] (3) After stirring, microwave heating is used immediately. The microwave heating power is set to 0, 380, 540 and 700W respectively. After heating for 10 minutes, the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, finally obtaining alkalized cocoa powder.

[0089] Table 3. Microwave power optimization results in the efficient alkalization method for cocoa powder

[0090]

[0091] Note: Temperature refers to the temperature equivalent to continuous heating at the corresponding microwave power and microwave time.

[0092] Microwave power control allows for precise control of heating speed and temperature, thus affecting the rate and effectiveness of the alkalization reaction. Appropriate power ensures the alkalization reaction proceeds fully while avoiding excessively high temperatures that could negatively impact cocoa powder quality. Excessive microwave power leads to excessive energy absorption by the raw materials, damaging the structure of cocoa powder particles and potentially affecting the alkalization reaction and reducing cocoa powder quality. Insufficient power may result in uneven heating, preventing some cocoa powder from fully alkalizing and affecting the overall product quality. Therefore, this embodiment selects a microwave power between 380W and 700W for alkalization.

[0093] The results of this embodiment are shown in Table 3, specifically:

[0094] (1) When the microwave power is 0W, the alkalized cocoa powder obtained is too light in color and too high in pH. Although the phytochemicals are well preserved and the antioxidant capacity is high, the application is relatively narrow and can only be used in applications that require light-colored cocoa powder.

[0095] (2) When the microwave power is 380W, the alkalized cocoa powder is light brown in color, with a high degree of retention of phytochemicals and high antioxidant capacity.

[0096] (3) When the microwave power is 540W, the alkalized cocoa powder is brown in color, the phytochemicals are less damaged, and the antioxidant capacity is higher.

[0097] (4) When the microwave power is 700W, the alkalized cocoa powder is dark brown in color, the phytochemicals are more severely damaged, and the antioxidant capacity is reduced.

[0098] In summary, the optimal microwave power is 540W. At this power, the cocoa powder after alkalization is brown in color, the phytochemicals are less damaged, the antioxidant capacity is higher, and it has a wide range of applications.

[0099] Example 4: Optimization of an efficient alkalization method for cocoa powder

[0100] This embodiment optimizes the microwave time; other parameters are the same as in Embodiment 1.

[0101] (1) Mix cocoa powder and deionized water at a mass-volume ratio of 1:9 (g:mL) and stir at 600 rpm for 5 min at room temperature to completely dissolve the cocoa powder in the water;

[0102] (2) Add 0.6 and 1.1 mL of 4M NaOH solution respectively to adjust the pH of the system to 6.8 and 8.0, and continue stirring at 600 rpm for 5 min;

[0103] (3) After stirring, microwave heating is used immediately. The microwave heating power is 540W, and the heating time is set to 0, 5, 10 and 15 minutes respectively. After that, the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, and finally alkalized cocoa powder is obtained.

[0104] Table 4. Optimization results of microwave time in the efficient alkalization method for cocoa powder

[0105]

[0106]

[0107] Note: Alkali concentration refers to the mass of NaOH solids in the added NaOH solution: the mass of cocoa powder; temperature refers to the temperature equivalent to continuous heating at the corresponding microwave power and microwave time.

[0108] The reasons for adjusting microwave time are similar to those for adjusting microwave power. If the heating time is too long, it will reduce the quality of cocoa powder; if the heating time is too short, it will be difficult for the cocoa powder to be fully alkalized. Therefore, in this embodiment, the microwave heating time for alkalizing cocoa powder is controlled between 5 min and 15 min.

[0109] The results of this embodiment are as follows, specifically:

[0110] (1) When the microwave time is set to 0 min, the alkalized cocoa powder obtained is too light in color. Although the phytochemicals are well preserved and the antioxidant capacity is high, the application is relatively narrow and can only be used in applications that require light-colored cocoa powder.

[0111] (2) When the microwave time is set to 5 min, the resulting alkalized cocoa powder is light brown in color, retains phytochemicals well, and has high antioxidant capacity, but it is only suitable for applications that require light-colored cocoa powder.

[0112] (3) When the microwave time is set to 10 min, the resulting alkalized cocoa powder is brown in color, with less damage to phytochemicals and higher antioxidant capacity.

[0113] (4) When the microwave time is 15 min, the alkalized cocoa powder is brown in color, indicating that the phytochemicals are more severely damaged and the antioxidant capacity is reduced.

[0114] In summary, the optimal microwave time is 10 minutes. At this time, the cocoa powder turns brown after alkalization, the phytochemicals are less damaged, and the antioxidant capacity is high; it has a wide range of applications.

[0115] Example 5: Optimization of an efficient alkalization method for cocoa powder

[0116] This embodiment optimizes the mass-to-volume ratio of cocoa powder to deionized water, and the specific implementation method is the same as in Embodiment 1:

[0117] (1) Mix cocoa powder and deionized water at mass-volume ratios of 1:5, 1:9, and 1:20 (g:mL), and stir at 600 rpm for 5 minutes at room temperature to completely dissolve the cocoa powder in the water.

[0118] (2) Add 1.1 mL of 4M NaOH solution to adjust the pH of the system to 8.0, and continue stirring at 600 rpm for 5 min;

[0119] (3) After stirring, microwave heating is used immediately. The microwave heating power is 540W. After microwave heating for 10 minutes (equivalent to continuous heating to 90℃), the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, finally obtaining alkalized cocoa powder.

[0120] The results are shown in Table 5:

[0121] Table 5: Effect of different amounts of ionized water added

[0122]

[0123]

[0124] The results show:

[0125] The optimal mass-to-volume ratio of cocoa powder to deionized water is 1:9. At this ratio, suitable reaction conditions and equilibrium points can be obtained during the alkalization process, ensuring both the uniformity and completeness of the reaction while avoiding excessive dilution and ensuring the stability of the alkalization product. A 1:5 ratio results in a higher concentration of cocoa powder, which may lead to uneven mixing and incomplete reaction. A 1:20 ratio results in too diluted cocoa powder, which may weaken the alkalization reaction and make it difficult to achieve the ideal degree of alkalization, while also wasting resources.

[0126] Example 6: Optimization of an efficient alkalization method for cocoa powder

[0127] This embodiment optimizes the stirring rate of cocoa powder and deionized water, and the specific implementation method is the same as in Embodiment 1:

[0128] (1) Mix cocoa powder and deionized water at a mass-to-volume ratio of 1:9 (g:mL), and stir at 100, 200, 300, 600 and 900 rpm for 5 minutes at room temperature to completely dissolve the cocoa powder in the water.

[0129] (2) Add 1.1 mL of 4M NaOH solution to adjust the pH of the system to 8.0, and continue stirring at 600 rpm for 5 min;

[0130] (3) After stirring, microwave heating is used immediately. The microwave heating power is 540W. After microwave heating for 10 minutes (equivalent to continuous heating to 90℃), the sample is taken and immediately placed in an ice water bath to cool. Then it is stored in a refrigerator to freeze and freeze-dry, finally obtaining alkalized cocoa powder.

[0131] The results are shown in Table 6:

[0132] Table 6: Effects of different stirring conditions

[0133]

[0134] The results show:

[0135] This comparative study examined the effects of different stirring speeds, ultimately selecting 600 rpm as the optimal stirring speed due to its superior performance in terms of mixing uniformity, solubility, and ease of operation. In contrast, speeds of 100-300 rpm were too low, leading to insufficient mixing of cocoa powder and water, resulting in clumping and sedimentation, poor dissolution, and ultimately, incomplete alkalization. While 900 rpm provided rapid stirring, it introduced excessive air, causing excessive foaming, which affected liquid stability and subsequent operations, while also increasing equipment wear and energy consumption.

[0136] Comparative Example 1:

[0137] The specific implementation method is the same as in Example 1, except that the microwave heating method in step (3) is adjusted to be ordinary industrial heating, infrared heating, and ultrasonic treatment respectively:

[0138] The results are shown in Table 7:

[0139] Table 7: Effects of Different Heating Methods

[0140]

[0141] The results show:

[0142] Comparative Example 3 compared the effects of different heating methods. Microwave heating was chosen as the heat source in the alkalization process because it offers high heating efficiency, good uniformity, precise control, and can, to some extent, prevent the degradation of effective substances, making it more ideal than other methods. While conventional industrial heating is widely used, it is slow and prone to causing external heating followed by internal cooling, resulting in significant damage to the effective substances. Infrared heating, although acting directly on the surface of the object, lacks penetration and is difficult to heat uniformly. Ultrasonic treatment, while promoting the reaction, may lead to excessive vibration, causing structural damage or the formation of byproducts. Therefore, microwave heating has advantages in energy efficiency and process control, and was ultimately chosen as the heating method for the alkalization process of this invention.

[0143] Comparative Example 2:

[0144] The specific implementation method is the same as in Example 1, except that the cooling method in step (3) is adjusted to slow cooling at room temperature: the results are shown in Table 8:

[0145] Table 8: Effects of Different Cooling Methods

[0146]

[0147] Note: Temperature refers to the temperature equivalent to continuous heating at the corresponding microwave power and microwave time.

[0148] The results show that the main reason for choosing rapid cooling in an ice-water bath instead of slow cooling at room temperature in this invention is to terminate the reaction immediately and prevent the occurrence of side reactions at high temperatures, maintain the purity and quality of the alkalization product as much as possible, accelerate the entire production process, improve efficiency, and ensure that the physicochemical properties of different batches of products remain consistent. In contrast, slow cooling may not only lead to side reactions but also prolong the process time, which is not conducive to the stability of product performance.

[0149] Comparative Example 3:

[0150] The specific implementation method is the same as that in Example 1, except that the stirring conditions in step (1) are adjusted to stirring under microwave power of 540W and stirring speed of 600rpm.

[0151] The results are shown in Table 9:

[0152] Table 9: Effects of Different Stirring Conditions

[0153]

[0154] The results showed that this comparative study compared the effects of stirring at room temperature and microwave conditions on the alkalization of cocoa powder. The final choice was to stir the mixture of cocoa powder and deionized water at room temperature rather than under microwave conditions, mainly to avoid structural changes or premature reactions in the cocoa powder caused by overheating. Stirring at room temperature ensures uniform dispersion of the cocoa powder and maintains its natural properties. In addition, operation at room temperature is more stable and controllable, reducing the risk of uneven reaction and facilitating the subsequent alkalization process.

[0155] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Anyone skilled in the art can make various modifications and alterations without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be determined by the claims.

Claims

1. A method for alkalizing cocoa powder, characterized in that, Includes the following steps: (1) Mix cocoa powder and water at a mass-to-volume ratio of 1:9 (g:mL) and stir at 600 rpm for 5 min at room temperature to obtain a cocoa powder aqueous solution; (2) Add NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system to 7.5-8.5; wherein, the concentration of NaOH is 4 M, and the mass ratio of NaOH solid to cocoa powder in the system is 0.96%~2.56% (w / w). (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is microwave heated with a microwave heating power of 540 W and a microwave heating time of 10 min. After heating, it is immediately placed in an ice water bath to cool and then freeze-dried to finally obtain alkalized cocoa powder.

2. A method for increasing the retention of effective components in alkalized cocoa powder, characterized in that, The active ingredients include one or more of epicatechin, catechin, epigallocatechin gallate, theobromine, caffeine, tryptophan, 2-phenylethylamine, and tyramine; the method includes the following steps: (1) Mix cocoa powder and water at a mass-to-volume ratio of 1:9 (g:mL) and stir at 600 rpm for 5 min at room temperature to obtain a cocoa powder aqueous solution; (2) Add NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system to 7.5-8.5; wherein, the concentration of NaOH is 4 M, and the mass ratio of NaOH solid to cocoa powder in the system is 0.96%~1.76% (w / w). (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is microwave heated with a microwave heating power of 540 W and a microwave heating time of 10 min. After heating, it is immediately placed in an ice water bath to cool and then freeze-dried to finally obtain alkalized cocoa powder.

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