Method for efficiently alkalizing cocoa powder

Abstract

The invention belongs to the field of food processing, and particularly relates to a method for efficiently alkalizing cocoa powder, which specifically comprises the following steps: completely mixing cocoa powder with water to obtain a cocoa powder aqueous solution, adding a NaOH solution to adjust the pH value of the system to 6.8-9.2 for alkalization, then immediately heating by using microwaves at the microwave heating power of 380-700W for 5-15min, and cooling to room temperature to obtain the cocoa powder. And after heating is completed, immediately putting the cocoa powder into an ice-water bath for cooling, and then performing freeze drying to finally obtain alkalized cocoa powder. The alkalized cocoa powder prepared by the method is brown in color, more phytochemicals (epicatechin, catechin, theobromine and the like) are reserved, the oxidation resistance is higher, the flavor is better, and the alkalized cocoa powder can be widely applied to the food processing fields of drinks, baking, desserts, candy making and the like.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and in particular relates to a method for efficiently alkalizing cocoa powder. Background Art

[0002] Cocoa is an ingredient and raw material extracted from the fruit of the cocoa tree (Theobroma cacao). It needs to go through a series of complex processes to become a product. The processing steps include fermentation, drying, baking and alkalization. These steps have an important impact on the flavor, color and health of the final product.

[0003] The raw material of the alkalization step can be a series of intermediate products of cocoa processing such as cocoa powder, cocoa beans, cocoa liquor, etc., wherein cocoa powder becomes an important alkalization raw material because of its low fat content and easy process control. Alkalization process is an important step in cocoa processing, which is to change the pH value of cocoa powder by using alkaline substances (such as sodium hydroxide, potassium carbonate, etc.), and then promote the progress of chemical reaction at a certain temperature, thereby affecting the color, flavor and solubility of cocoa, which can improve the organoleptic quality and functionality of cocoa powder, making it more suitable for different application requirements. But in the existing cocoa powder alkalization process, there is a problem that the heating treatment time is long and the nutrients are destroyed.

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

[0005] In the prior art of using cocoa powder for alkalization, patent CN101502292A provides an alkalization method for controlling the color and flavor of cocoa powder, which uses cocoa kernels or cocoa powder as raw materials, adds potassium carbonate solution, alkalizes under pressure, and then bakes at high temperature. Finally, the alkalized powder obtained by grinding and sieving with a mesh size less than or equal to 60 mesh is neutralized by alkalization, and the color of the cocoa powder is made consistent and uniform, and the flavor and quality are improved; however, this method uses pressurized conditions and only focuses on the color change of the cocoa powder after alkalization.

[0006] Xu Duo et al. investigated the effects of temperature, pressure, alkalization time, and concentration of alkalization liquid on the color of alkalized cocoa powder in the study "The Effect of Alkalization Conditions on the Color of Cocoa Powder" (China Oils and Fats, 2020). However, the drying process after alkalization adopted oven drying at 130°C. Oven drying under high temperature conditions will further change the color of the alkalized cocoa powder, which increases interference to the color evaluation of the alkalized cocoa powder.

[0007] In the study of the alkalization process of cocoa kernels / powder (Jiangnan University, 2008), Feng Yun first studied the relationship between different alkalization conditions and the color of cocoa powder after alkalization, and then preliminarily explored the impact of alkalization conditions on the flavor of cocoa powder; however, the article also mostly carried out alkalization under pressurized conditions, using a variety of alkalization solutions, and when exploring the impact 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, only the chemical substances related to the color and smell of cocoa powder were tested, and no attention was paid to the changes in the beneficial components in the cocoa powder after alkalization, and the impact of the cocoa powder alkalization method on the quality of cocoa powder was not explored.

[0008] In summary, the prior art has the following problems: long heating treatment time, destruction of nutrients, complicated alkalization steps under pressurized conditions, use of mixed alkalization of multiple alkali solutions, difficulty in controlling and detecting the pH value of the alkalized solution, and failure to use comprehensive indicators, such as the color of the cocoa powder after alkalization, nutrients and antioxidant capacity, to control the quality of the cocoa powder. Summary of the invention

[0009] In order to solve the above technical problems, the present invention uses cocoa powder as a raw material, uses a single sodium hydroxide solution to alkalize the cocoa powder under normal pressure conditions, and provides a preparation method that can improve the retention rate of effective ingredients in the cocoa powder. Compared with potassium carbonate solution, alkalization with sodium hydroxide solution can more effectively adjust the pH value of cocoa powder, reduce its acidity and improve its flavor, and make it have higher solubility, so the present invention selects sodium hydroxide solution.

[0010] The present invention also uses microwave heating to assist alkalization. The direction of the microwave field changes continuously at an extremely high frequency. The electric dipoles in the water molecules will try to rotate rapidly following the direction of the electric field. Due to the continuous change in the direction of the electric field, the dipoles will rotate rapidly and generate friction, directly generating heat. Similarly, the rapid movement and oscillation of Na+ and OH- ions in the microwave field will intensify the friction and collision in the solution, generate additional heat energy, and the ionic conductivity phenomenon further enhances the effect of microwave heating. This dual heating mechanism makes the heating speed fast and more uniform, and the heating time can be greatly shortened, minimizing the damage to the nutrients. At the same time, the microwaves directly act on the water-containing part or other polar molecules in the cocoa powder, making the vibration and rotation of these molecules more intense. This molecular-level activation can effectively reduce the energy barrier required for the reaction and accelerate the reaction rate. In addition, the penetration of microwaves can ensure that the cocoa powder is heated simultaneously inside and outside, unlike the traditional heating method that relies on heat conduction and easily leads to the phenomenon that the external temperature of the sample is high and the internal temperature is low. This uniform heating characteristic is particularly important for the alkalization process because it can make all parts of the cocoa powder react under the same conditions, ensuring consistent alkalization effects and improving the uniformity of product quality.

[0011] The invention uses ultra-high performance liquid chromatography-high resolution mass spectrometry to analyze the phytochemical components of non-alkalized and alkalized cocoa powders, detects the pH value, antioxidant capacity and other indicators of the cocoa powders, and conducts a comprehensive and integrated evaluation of the effective components of the alkalized cocoa powders.

[0012] The color change during the alkalization process usually indicates the change in the structure and content of polyphenolic compounds (especially flavonoids). Some studies have found polar or non-polar chromophores during the alkalization of cocoa. Among them, catechins and 6'-hydroxycatechins derived from their free radical state are the main reasons for the formation of red-brown colors. Therefore, polyphenolic substances such as catechins are considered to be potential markers of alkalization. Flavonoids have strong antioxidant capacity, can reduce blood lipids and cholesterol, can promote blood circulation, improve blood fluidity, and also have preventive and therapeutic effects on certain cancers. Therefore, by analyzing the color changes before and after the alkalization of cocoa, we can infer the changing trends of the content of polyphenolic compounds (especially flavonoids), and then evaluate how these changes affect the efficacy of cocoa products in terms of benefiting health.

[0013] To achieve the above technical effects, the first object of the present invention is to provide a method for alkalizing cocoa powder, comprising the following steps:

[0014] (1) mixing cocoa powder and water to obtain a cocoa powder aqueous solution;

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

[0016] (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is subjected to microwave heating, the microwave heating power is 380-700 W, the microwave heating time is 5-15 min (equivalent to continuously heating to 60-110° C.), and immediately placed in an ice water bath for cooling after the heating is completed, and then freeze-dried to finally obtain alkalized cocoa powder.

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

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

[0019] Furthermore, the cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 100-900 rpm for 3-10 min at 15-30° C.;

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

[0021] Furthermore, in step (2), the concentration of the NaOH solution is 1-10 M, 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 3-5 M, and the pH of the system is adjusted to 7.8-8.3.

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

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

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

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

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

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

[0029] (1) mixing cocoa powder and water to obtain a cocoa powder aqueous solution;

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

[0031] (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is subjected to microwave heating, the microwave heating power is 380-700 W, the microwave heating time is 5-15 min (equivalent to continuously heating to 60-110° C.), and immediately placed in an ice water bath for cooling after the heating is completed, and then freeze-dried to finally obtain alkalized cocoa powder.

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

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

[0034] Furthermore, the cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 100-900 rpm for 3-10 min at 15-30° C.;

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

[0036] Furthermore, in step (2), the concentration of the NaOH solution is 1-10 M, 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 3-5 M, and the pH of the system is adjusted to 7.8-8.3.

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

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

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

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

[0042] Beneficial Effects

[0043] 1. When polyphenols are heated above 80°C, their degradation rate is significantly accelerated, resulting in a significant decrease in their content; this phenomenon is particularly significant at temperatures above 90°C. The present invention uses microwave heating to assist in the alkalization of cocoa powder. The microwave power of 540W used in Example 1 of the present invention is used to heat for 10 minutes, which is equivalent to continuously heating to 90°C; this microwave heating speed is faster and the heating is more uniform, and the processing time of cocoa powder is also greatly shortened, minimizing the damage to the nutrients (such as polyphenols) in the cocoa powder.

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

[0045] 3. The method of the present invention uses an ice water bath to quickly cool the alkalized cocoa powder after microwave heating, so as to terminate the reaction immediately and prevent the occurrence of side reactions at high temperatures, thereby maintaining the purity and quality of the alkalized cocoa powder product as much as possible, while speeding up the entire production process and improving production efficiency.

[0046] 4. The present invention uses cocoa powder as raw material and adopts normal pressure conditions in the alkalization process, which simplifies the alkalization step, does not require complicated parameter settings, and is more suitable for large-scale production.

[0047] 5. The present invention uses a single sodium hydroxide solution for alkalization, which is easy to control and detect the pH value of the alkalized liquid, making the condition control of the alkalization process more precise. Compared with traditional alkalization, the alkalization time is shorter, the alkalization amount is less, and the efficiency is higher.

[0048] 6. The present invention adopts ultra-high performance liquid chromatography-high resolution mass spectrometry to analyze the phytochemical components of non-alkalized and alkalized cocoa powders, and detects the pH value, antioxidant capacity and other indicators of the cocoa powder, and conducts a comprehensive and integrated evaluation of the quality and nutritional value of the alkalized cocoa powder. DETAILED DESCRIPTION

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

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

[0051] 1. Method for determining the color of cocoa powder:

[0052] 3 g of cocoa powder was spread in a culture dish, and the color of the cocoa powder was measured using a colorimeter. The present invention selected color measurement parameters L*, a*, and b* as evaluation criteria: these parameters represent brightness (L*), red-green balance (a*), and yellow-blue balance (b*), respectively.

[0053] 2. pH determination method:

[0054] Take 1g of cocoa powder and stir it in 9mL of distilled water until there is no lumps in the suspension. After filtering, measure the pH of the sample with a calibrated pH meter.

[0055] 3. Determination method of phytochemical content:

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

[0057] 4. Determination method of antioxidant capacity:

[0058] The alkalized cocoa powder was defatted by n-hexane extraction, and the defatted cocoa powder was extracted with 80% methanol (the defatting treatment can reduce fat interference, improve the life of the chromatographic column, the separation effect and the sensitivity of the analysis, and ensure that the measurement results are more accurate and reliable), and then oscillated and mixed evenly with 0.1mM DPPH, and the absorbance was measured at 517nm after reacting for 15min in a dark environment; at the same time, a certain amount of defatted cocoa powder treated with 80% methanol and 7mM ABTS solution were vortexed and mixed, and after reacting for 6min in a dark condition, the absorbance was measured at 734nm, and finally the antioxidant capacity results of the alkalized cocoa powder were obtained.

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

[0060] The raw cocoa powder involved in the following embodiments was purchased from Tianjin Xianger Food Co., Ltd. with item number 00285.

[0061] Example 1 A method for efficiently alkalizing cocoa powder

[0062] (1) cocoa powder and deionized water were mixed at a mass volume ratio of 1:9 (g:mL), and stirred at 600 rpm for 5 min at room temperature to completely dissolve the cocoa powder in the water;

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

[0064] (3) After the stirring is completed, microwave heating is immediately performed at a power of 540 W. After microwave heating for 10 minutes (equivalent to continuous heating to 90° C.), a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

[0065] Table 1 Cocoa powder color and nutritional value results after alkalization

[0066]

[0067] The results are shown in Table 1. It can be seen from Table 1 that 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 better flavor. It can be widely used in food processing fields such as beverages, baking, desserts and candy making.

[0068] Example 2 Optimization of a method for efficiently alkalizing cocoa powder

[0069] This example optimizes the amount of alkali added, and other parameter conditions are the same as those in Example 1:

[0070] (1) Cocoa powder and deionized water were mixed at a mass volume ratio of 1:9 (g:mL), and stirred at 600 rpm for 5 min 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 the stirring is completed, microwave heating is immediately used, and the microwave heating power is set to 540 W and 700 W respectively. After heating for 10 minutes, a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

[0073] Table 2 Optimization results of alkali addition in the efficient alkalization method of cocoa powder

[0074]

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

[0076] NaOH plays an important role in the alkalization process of cocoa powder. The amount of alkali added directly affects the acidity of cocoa powder. By adding an appropriate amount of alkaline substances, the acidic components in the cocoa powder can be effectively neutralized and the taste can be improved. At the same time, adding an appropriate amount of alkali can make the color of the cocoa powder darker, presenting a more attractive brown or dark brown, and can also improve the solubility and dispersibility of cocoa powder in water, making the application of cocoa powder more extensive. However, adding too much alkali 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 Cocoa Powder Quality Requirements, the cocoa powder obtained when the alkali concentration is 0.96% is lightly alkalized cocoa powder; the cocoa powder obtained when the alkali concentration is 1.76% is medium alkalized cocoa powder; the cocoa powder obtained when the alkali concentration is 2.56% is heavily alkalized cocoa powder;

[0079] Specifically:

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

[0081] (2) When the alkali concentration is 1.76%, the alkalized cocoa powder reaches a moderate alkalization level, the color is brown, and 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 level of heavy alkalization, the color is dark brown, and the degree of destruction of phytochemicals is aggravated; however, the obtained product also further broadens its application, and can be used for the production of hot chocolate, baked cakes, chocolate candies, etc.

[0083] In summary, the optimal alkali concentration is 1.76%. At this time, the alkalized cocoa powder is brown in color, has a strong antioxidant capacity, and the nutrients epicatechin, catechin, epigallocatechin gallate and tyramine are less damaged; it can be used in the production of hot chocolate, brewing, coating, ice cream, baked cakes, etc.

[0084] Example 3 Optimization of a method for efficiently alkalizing cocoa powder

[0085] This example optimizes the microwave power, and other parameters are the same as those in Example 1:

[0086] (1) cocoa powder and deionized water were mixed at a mass volume ratio of 1:9 (g:mL), and stirred 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 4 M NaOH solution to adjust the pH of the system to 8.0, and continue stirring at 600 rpm for 5 min;

[0088] (3) After the stirring is completed, microwave heating is immediately used, and the microwave heating power is set to 0, 380, 540, and 700 W respectively. After the heating time is 10 minutes, a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

[0089] Table 3 Optimization results of microwave power in efficient alkalization method of cocoa powder

[0090]

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

[0092] The regulation of microwave power can accurately control the heating speed and temperature, thereby affecting the speed and effect of the alkalization reaction; appropriate power can ensure that the alkalization reaction is fully carried out, while avoiding the negative impact of excessive temperature on the quality of cocoa powder: if the microwave power is too high, the raw material absorbs too much energy, which will destroy the structure of the cocoa powder particles, not only affecting the alkalization reaction, but also may reduce the quality of the cocoa powder; if the power is too low, it may cause uneven heating, so that part of the cocoa powder cannot be fully alkalized, affecting the overall quality of the product; therefore, in this embodiment, the microwave power for controlling the alkalization is selected to be between 380W and 700W.

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

[0094] (1) When the microwave power is 0 W, the color of the alkalized cocoa powder is too light and the pH is too high. Although the phytochemicals are well retained 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 380 W, the alkalized cocoa powder is light brown in color, has a high degree of phytochemical retention, and has a high antioxidant capacity;

[0096] (3) When the microwave power is 540 W, the alkalized cocoa powder is brown in color, the degree of damage to phytochemicals is low, and the antioxidant capacity is high;

[0097] (4) When the microwave power is 700 W, the color of the alkalized cocoa powder is dark brown, the degree of destruction of phytochemicals is aggravated, and the antioxidant capacity is reduced;

[0098] In summary, the optimal microwave power is 540W. At this time, the color of the alkalized cocoa powder is brown, the degree of damage to phytochemicals is low, the antioxidant capacity is high, and it is widely used.

[0099] Example 4 Optimization of a method for efficiently alkalizing cocoa powder

[0100] This example optimizes the microwave time, and other parameters are the same as in Example 1:

[0101] (1) cocoa powder and deionized water were mixed at a mass volume ratio of 1:9 (g:mL), and stirred 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 4 M 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 the stirring is completed, microwave heating is immediately used, the microwave heating power is 540 W, and the heating time is set to 0, 5, 10, and 15 minutes respectively. Then, a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

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

[0105]

[0106]

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

[0108] The reason for regulating microwave time is similar to that for regulating microwave power. If the heating time is too long, the quality of the cocoa powder will be reduced; if the heating time is too short, it will be difficult to fully alkalize the cocoa powder. Therefore, in this embodiment, the microwave heating time for alkalizing the cocoa powder is controlled to be between 5min and 15min.

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

[0110] (1) When the microwave time is set to 0 min, the color of the alkalized cocoa powder is too light. Although the phytochemicals are well retained 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 alkalized cocoa powder obtained is light brown in color, with better retention of phytochemicals and higher antioxidant capacity, but it is only suitable for applications that require light-colored cocoa powder;

[0112] (3) When the microwave time was set to 10 min, the alkalized cocoa powder obtained was brown in color, with a lower degree of damage to phytochemicals and a higher antioxidant capacity;

[0113] (4) When the microwave time is 15 min, the color of the alkalized cocoa powder is brown, the degree of destruction of phytochemicals is aggravated, and the antioxidant capacity is reduced;

[0114] In summary, the optimal microwave time is 10 minutes. At this time, the color of the alkalized cocoa powder is brown, the degree of damage to phytochemicals is low, and the antioxidant capacity is high; it is widely used.

[0115] Example 5 Optimization of a method for efficiently alkalizing cocoa powder

[0116] This example optimizes the mass volume ratio of cocoa powder to deionized water, and the specific implementation method is the same as that of Example 1:

[0117] (1) Cocoa powder was mixed with deionized water at a mass volume ratio of 1:5, 1:9, and 1:20 (g:mL), and stirred at 600 rpm for 5 min at room temperature to completely dissolve the cocoa powder in the water;

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

[0119] (3) After the stirring is completed, microwave heating is immediately performed at a power of 540 W. After microwave heating for 10 minutes (equivalent to continuous heating to 90° C.), a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

[0120] The results are shown in Table 5:

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

[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, which can ensure the uniformity and sufficiency of the reaction while avoiding excessive dilution and ensuring the stable quality of the alkalized product. At a ratio of 1:5, the cocoa powder concentration is relatively high, which may lead to uneven mixing and incomplete reaction. At a ratio of 1:20, the cocoa powder is too dilute, which may weaken the effect of the alkalization reaction and make it difficult to achieve the ideal alkalization degree. On the other hand, it will also cause a waste of resources.

[0126] Example 6: Optimization of a method for efficiently alkalizing cocoa powder

[0127] This example optimizes the stirring rate of cocoa powder and deionized water, and the specific implementation method is the same as that of Example 1:

[0128] (1) Cocoa powder and deionized water were mixed at a mass volume ratio of 1:9 (g:mL), and stirred at 100, 200, 300, 600, and 900 rpm for 5 min at room temperature to completely dissolve the cocoa powder in the water;

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

[0130] (3) After the stirring is completed, microwave heating is immediately performed at a power of 540 W. After microwave heating for 10 minutes (equivalent to continuous heating to 90° C.), a sample is taken and immediately placed in an ice water bath for cooling, and then stored in a refrigerator for freezing and freeze drying to finally obtain alkalized cocoa powder.

[0131] The results are shown in Table 6:

[0132] Table 6: Effect of different stirring conditions

[0133]

[0134] The results show:

[0135] This comparative example compares the effects of different stirring speeds, and finally selects 600rpm as the stirring speed because it performs best in terms of mixing uniformity, solubility, and ease of operation. In contrast, a speed of 100-300rpm is too low, which will lead to insufficient mixing of cocoa powder and water, easy agglomeration and precipitation, poor dissolution effect, and ultimately inability to fully alkalize; and although 900rpm can stir quickly, it introduces too much air, resulting in excessive foam, affecting liquid stability and subsequent operations, while increasing equipment wear and energy consumption.

[0136] Comparative Example 1:

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

[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 compares the effects of different heating methods, and selects microwave heating as the heat source in the alkalization process because of its high heating efficiency, good uniformity, precise control, and ability to avoid degradation of effective substances to a certain extent, which is more ideal than other methods. Although ordinary industrial heating is widely used, it has a slow heating speed and is prone to causing the phenomenon of external heat and internal coldness, and the degree of damage to effective substances is also high; although infrared heating directly acts on the surface of the object, it has insufficient penetration and is difficult to heat evenly; although ultrasonic treatment can promote the reaction, it may cause excessive vibration, resulting in damage to the material structure or the generation of by-products; therefore, microwave heating has more advantages in energy efficiency and process control, and microwave heating is finally selected as the heating means for the alkalization method of the present invention.

[0143] Comparative Example 2:

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

[0145] Table 8: Effects of different cooling methods

[0146]

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

[0148] The results show that the main reason for the present invention to choose rapid cooling in an ice-water bath rather than slow cooling at room temperature is to terminate the reaction immediately and prevent the occurrence of side reactions at high temperatures, to maintain the purity and quality of the alkalized product as much as possible, and to speed up the entire production process, improve efficiency, and help to keep the physical and chemical indicators of different batches of products consistent; in contrast, slow cooling may not only cause 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 Example 1, except that the stirring condition in step (1) is adjusted to stirring under the condition of microwave power of 540 W and stirring speed of 600 rpm;

[0151] The results are shown in Table 9:

[0152] Table 9: Effect of different stirring conditions

[0153]

[0154] The results showed that: this comparative example compared the effects of stirring at room temperature and microwave conditions on the alkalization of cocoa powder. Ultimately, it was chosen to stir the mixture of cocoa powder and deionized water at room temperature rather than under microwave conditions. This was mainly to avoid structural changes or premature reactions of the cocoa powder caused by excessive heating. Stirring at room temperature can ensure that the cocoa powder is evenly dispersed 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 as above in the form of a preferred embodiment, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for alkalizing cocoa powder, characterized in that: The following steps are involved: (1) mixing cocoa powder and water to obtain a cocoa powder aqueous solution; (2) adding NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system; (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is subjected to microwave heating, the microwave heating power is 380-700W, the microwave heating time is 5-15min, and after the heating is completed, it is immediately placed in an ice water bath for cooling, and then freeze-dried to finally obtain alkalized cocoa powder.

2. The alkalization method according to claim 1, characterized in that The mass volume ratio of the cocoa powder to deionized water in step (1) is 1:3-1:20 (g:mL).

3. The alkalization method according to claim 1, characterized in that The cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 100-900 rpm for 3-10 min at 15-30°C.

4. The alkalization method according to claim 1, characterized in that The concentration of the NaOH solution in step (2) is 1-10 M, and the pH of the system is adjusted to 7.5-8.

5.

5. The alkalization method according to claim 1, characterized in that In step (2), the pH of the system is adjusted while stirring, the stirring speed is 100-900 rpm, and the stirring time is 3-10 min.

6. A method for increasing the retention of active ingredients in cocoa powder, characterized in that: The active ingredients include one or more of epicatechin, catechin, epigallocatechin gallate, theobromine, caffeine, tryptamine, 2-phenylethylamine, and tyramine; the method includes the following steps: (1) mixing cocoa powder and water to obtain a cocoa powder aqueous solution; (2) adding NaOH solution to the cocoa powder aqueous solution obtained in step (1) to adjust the pH of the system; (3) The cocoa powder aqueous solution after adjusting the pH of the system in step (2) is subjected to microwave heating, the microwave heating power is 380-700W, the microwave heating time is 5-15min, and after the heating is completed, it is immediately placed in an ice water bath for cooling, and then freeze-dried to finally obtain alkalized cocoa powder.

7. The method according to claim 6, characterized in that The mass volume ratio of the cocoa powder to deionized water in step (1) is 1:3-1:20 (g:mL).

8. The method according to claim 6, characterized in that The cocoa powder in step (1) is completely dissolved in water under the condition of stirring at 100-900 rpm for 3-10 min at 15-30°C.

9. The method according to claim 6, characterized in that The concentration of the NaOH solution in step (2) is 1-10 M, and the pH of the system is adjusted to 7.5-8.

5.

10. The method according to claim 6, characterized in that In step (3), the pH of the system is adjusted while stirring, the stirring speed is 100-900 rpm, and the stirring time is 3-10 min.

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