Method for improving stability of lycium ruthenicum murr. anthocyanin by lycium barbarum acid, application and lycium ruthenicum murr. processing product

Abstract

This invention belongs to the field of goji berry processing technology, specifically relating to a method, application, and processed products of black goji berries that utilize citric acid to improve the stability of anthocyanins in black goji berries. The method involves adding citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) to black goji berry anthocyanins, utilizing intramolecular or intermolecular co-coloring interactions to inhibit anthocyanin degradation and color deterioration of the product. Compared to existing technologies, this represents a leap from "temporary color protection" to "relatively long-lasting stability." It is effective in complex systems: equally effective in black goji berry juice (a real food matrix containing various components such as sugars, acids, and phenols), and even more so. Citric acid (AA-2βG) is naturally found in goji berries and other solanaceous plants, and there are no safety concerns regarding its use as a food additive.

Description

Technical Field

[0001] This invention belongs to the field of wolfberry processing technology, specifically relating to a method, application, and processed products of black wolfberry that utilizes citric acid to improve the stability of anthocyanins. Background Technology

[0002] Anthocyanins are a class of natural water-soluble pigments widely found in plants, possessing various biological activities. However, their chemical properties are extremely unstable, easily degraded by external conditions such as light, temperature, oxygen concentration, pH, and metal ions. Black goji berries (Lycium ruthenicum Murr.) are rich in uniquely structured petunia-based acylated anthocyanins, which are their core coloring substances and bioactive components. However, during processing (such as pulping, heat concentration, and sterilization) and storage, the anthocyanins in black goji berries are highly susceptible to degradation, causing the product's color to deteriorate from purplish-black or purplish-red (depending on concentration and pH) to brownish-red, severely restricting the quality and shelf life of its processed products.

[0003] Currently, color-protecting agents such as ascorbic acid (VC) and citric acid are commonly used in production, but their color-protecting effect is limited, and the color retention time is short, making it difficult to meet the product's shelf-life requirements. Therefore, developing a method to effectively and stably improve the stability of anthocyanins in black goji berries has significant application value. Summary of the Invention

[0004] In view of this, the present invention provides a method, application and processed products of black goji berries that utilize citric acid (AA-2βG) to improve the stability of anthocyanins in black goji berries, in order to solve the technical problem that the color protection effect is limited and the color maintenance time is not long when using color protection agents such as ascorbic acid (VC) and citric acid in the prior art, which makes it difficult to meet the shelf life requirements of the products.

[0005] To achieve the above objectives, this application adopts the following approach:

[0006] A method for improving the stability of anthocyanins in black goji berries using citric acid involves adding citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) to black goji berry raw materials or their processed products. The citric acid interacts with the anthocyanins in black goji berries via intramolecular or intermolecular co-coloring effects, thereby inhibiting the degradation of anthocyanins and the deterioration of the product's color.

[0007] Preferably, the black goji berry raw material or its processed products include fresh black goji berries, pulp, juice, powder, extracts, as well as food, health products or beverages prepared using black goji berries as raw material.

[0008] Preferably, the concentration of citric acid (AA-2βG) added is 0.3 mg / mL to 1.5 mg / mL.

[0009] Preferably, the addition method involves dissolving citric acid and then adding the dissolved citric acid to the black goji berry raw material or its processed product in a normal way, and then mixing it thoroughly with the black goji berry raw material or its processed product by shaking or stirring, avoiding excessive stirring.

[0010] Preferably, the method is used to maintain or enhance the red hue (a value) of processed black goji berry products, reduce their brightness value (L value), and protect the product color.

[0011] Application of citric acid (AA-2βG) in products that improve the stability of anthocyanins in black goji berries, protect the color of processed black goji berry products, or inhibit the degradation of anthocyanins in black goji berries.

[0012] Preferably, the product is a food additive, color protectant, antioxidant, or auxiliary material used in the processing of black goji berries.

[0013] A processed product of black goji berries with highly stable anthocyanins, comprising black goji berry raw material and citric acid (AA-2βG).

[0014] Preferably, the product is black goji berry juice, black goji berry pulp, black goji berry powder, or black goji berry extract solution.

[0015] Preferably, the amount of citric acid (AA-2βG) added is such that its concentration in the processed black goji berry product reaches 0.3 mg / mL-1.5 mg / mL.

[0016] The technical solution adopted in this application can achieve the following beneficial effects:

[0017] The aforementioned methods, applications, and processed products of black goji berries utilize citric acid to enhance the stability of anthocyanins. Citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) is added to the raw materials or processed products of black goji berries. This utilizes the intramolecular or intermolecular co-coloring effect of citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) with the anthocyanins of black goji berries, inhibiting anthocyanin degradation and color deterioration. The method provided in this application can significantly extend the color-protecting time of raw materials or processed products of black goji berries. Compared with existing technologies, it achieves a leap from "short-term color protection" to "relatively long-lasting stability." It is equally effective, and even more so, in black goji berry juice (a real food matrix containing various components such as sugars, acids, and phenols). Furthermore, citric acid (AA-2βG) is naturally present in goji berries and other solanaceous plants, and as a food additive, it poses no safety concerns and will not cause drastic pH fluctuations or produce harmful intermediate products like vitamin C. Attached Figure Description

[0018] Figure 1The structural formula of petunidin-3-O-[rhamnopyranosyl-(trans-p-coumaroyl)]-5-O-(β-D-glucopyranoside), the main anthocyanin in black wolfberry.

[0019] Figure 2 The structural formula is 2-O-β-D-glucosyl-L-ascorbic acid (AA-2βG).

[0020] Figure 3 This is a graph showing the light intensity (L) of solutions with different concentrations of vitamin C added in Comparative Example 1 of this application.

[0021] Figure 4 This is a graph showing the light intensity (L) of solutions with different concentrations of citric acid added in Example 1 of this application.

[0022] Figure 5 This is a graph showing the redness value (a) of solutions with different concentrations of VC added in Comparative Example 1 of this application.

[0023] Figure 6 This is a graph showing the redness value (a) of solutions with different concentrations of citric acid added in Example 1 of this application.

[0024] Figure 7 This is a graph showing the detection of anthocyanins in the solution after adding different concentrations of vitamin C in Comparative Example 1 of this application.

[0025] Figure 8 This is a graph showing the detection of anthocyanins in the solution after adding different concentrations of citric acid in Example 1 of this application.

[0026] Figure 9 This is a graph showing the light intensity (L) of solutions with different concentrations of vitamin C added in Comparative Example 2 of this application.

[0027] Figure 10 This is a graph showing the light intensity (L) of solutions with different concentrations of citric acid added in Example 2 of this application.

[0028] Figure 11 This is a graph showing the redness value (a) of solutions with different concentrations of VC added in Comparative Example 2 of this application.

[0029] Figure 12 This is a graph showing the redness value (a) of solutions with different concentrations of citric acid added in Example 2 of this application. Detailed Implementation

[0030] To facilitate understanding of this application, a more comprehensive description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are also given. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to enable a more thorough and complete understanding of the disclosure of this application.

[0031] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0032] Please refer to Figure 1 and Figure 2 In one specific embodiment, this application provides a method for improving the stability of anthocyanins in black goji berries using citric acid (AA-2βG). Citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) is added to black goji berry raw materials or their processed products. Citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) interacts with anthocyanins in black goji berries via intramolecular or intermolecular co-coloring, thereby inhibiting the degradation of anthocyanins and the deterioration of the product's color.

[0033] The specific operation process is as follows: First, prepare the raw materials of black goji berries or their processed products to be processed. The "raw materials or their processed products" can be fresh black goji berries, pulp, juice, powder, extracts, and foods, health products, beverages, etc., produced using these as raw materials. Then, add a certain amount of citric acid (AA-2βG) to the above materials. Finally, mix the citric acid (AA-2βG) thoroughly with the materials by shaking and stirring, taking care to avoid excessive stirring to prevent the introduction of too much oxygen or structural damage due to violent mechanical action. When mixing the obtained citric acid with the black goji berry raw materials, the temperature should be controlled between 4℃ and 25℃, and light should be avoided. The core purpose is to maximize the protection of the activity and structural stability of anthocyanins in black goji berries, avoiding unnecessary degradation in the early stages of processing. A low-temperature environment helps maintain the natural conformation of anthocyanins (amberic cation form), making it easier for them to form effective co-color binding with citric acid molecules. If the temperature is too high, the anthocyanin conformation changes, and the co-coloring efficiency will be greatly reduced; high temperatures will accelerate the oxidation reaction. Anthocyanins are prone to irreversible degradation under oxidative conditions, causing their color to change from red / purple to brown.

[0034] The mechanism of action of this application is intramolecular or intermolecular auxiliary color interaction.

[0035] Specifically, copigmentation is a natural chemical phenomenon in anthocyanin stabilization. Anthocyanin molecules exist in solution in an equilibrium where they reversibly convert between colored yellow molasses salt forms (red / purple) and colorless / partially colorless methanolic pseudobase forms (colorless) and hydrated chalcone forms (pale yellow). Copigmentation refers to the stacking of anthocyanins with other colorless or pale-colored organic molecules (called "copigmenting factors") through non-covalent bonds (mainly hydrophobic interactions, π-π stacking) to form a "sandwich" structure. In this application, citric acid (AA-2βG) serves as a copigmenting factor. Citric acid (AA-2βG) possesses a suitable aromatic / hydrophobic region, allowing it to undergo π-π stacking with the planar structure of petunia-type aromatic acid-acylated anthocyanins unique to black goji berries, forming a stable complex. Black goji berry anthocyanins themselves possess aromatic acid acyl groups (such as coumarin groups), which can fold back and stack with the anthocyanin core. Citrate acid (AA-2βG) may further enhance or stabilize this folded conformation. The AA-2βG molecule acts as an external "sandwich," inserting itself between two anthocyanin molecules, or between one anthocyanin and another cochromogenic factor, forming a multilayered stack. The most water-vulnerable reaction site (C2 position) in the anthocyanin molecule is shielded by the AA-2βG molecule, significantly reducing the rate at which anthocyanins react with water to form a colorless methanolic pseudobase. This prevents subsequent CO bond ring-opening to form chalcones, and ultimately degradation into colorless or brown products such as coumarins and benzoic acid.

[0036] Therefore, citric acid (AA-2βG) tightly protects the unstable anthocyanin core structure through non-covalent stacking, making it more difficult for water molecules to attack, thus maintaining a bright red color for a long time.

[0037] The aforementioned method, application, and processed products of black goji berries utilize citric acid (AA-2βG) to enhance the stability of anthocyanins. This involves adding citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) to the raw black goji berry material or its processed products. Citric acid (2-O-β-D-glucosyl-L-ascorbic acid, AA-2βG) interacts with anthocyanins via intramolecular or intermolecular co-coloring, inhibiting anthocyanin degradation and color deterioration. The method provided in this application can significantly extend the color-protecting time of the raw black goji berry material or its processed products. Compared to existing technologies, it achieves a leap from "short-term color protection" to "relatively long-lasting stability." It is equally effective, and even more so, in black goji berry juice (a real food matrix containing various components such as sugars, acids, and phenols). Furthermore, citric acid (AA-2βG) is naturally present in goji berries and other solanaceous plants, and as a food additive, it poses no safety concerns and will not cause drastic pH fluctuations or produce harmful intermediates like vitamin C.

[0038] Specifically, the concentration of citric acid (AA-2βG) added is 0.3 mg / mL to 1.5 mg / mL.

[0039] Furthermore, the method is used to maintain or enhance the red hue (a value) of processed black goji berry products, reduce their brightness value (L value), and protect the product's color.

[0040] The α value (redness value) is one of the core indicators for evaluating the color quality of black goji berry products. A higher α value indicates a stronger red hue and an appearance closer to the purplish-red characteristics of fresh black goji berries. A lower α value indicates that the product is deteriorating towards browning. Under the method of this invention, the α value of black goji berry products with added citric acid (AA-2βG) is significantly maintained during storage. The preservation of the red hue directly affects consumers' first impression of the product's freshness and quality, and is crucial for the market acceptance of processed black goji berry juice, pulp, wine, and other products.

[0041] The L-value (brightness value) reflects the lightness or darkness of a product. Fresh black goji berries, due to their high anthocyanin content, exhibit a deep purplish-black color and a low L-value. As anthocyanins degrade, the product color lightens and turns brown, and the L-value increases. The method of this invention can significantly inhibit the increase of the L-value in processed black goji berry products during storage. The deep purplish-black color is a typical appearance characteristic that distinguishes black goji berries from other goji berry varieties (such as red goji berries), and maintaining this characteristic is crucial for product market positioning.

[0042] Anthocyanins are both the coloring agents of black goji berries and their core active ingredients (possessing various biological activities such as anti-tumor, hypoglycemic, and antioxidant effects). Maintaining anthocyanin content means simultaneously preserving the product's color quality and nutritional value. The method of this invention can effectively inhibit the degradation of anthocyanins in processed black goji berry products. Maintaining anthocyanin content ensures the content of active ingredients that can be labeled on the product label, supporting the product's functional claims and market competitiveness.

[0043] This embodiment improves the stability of anthocyanins in black goji berries by achieving three defined effects (maintaining the α value, reducing the L value, and maintaining the anthocyanin content).

[0044] Application of citric acid (AA-2βG) in products that improve the stability of anthocyanins in black goji berries, protect the color of processed black goji berry products, or inhibit the degradation of anthocyanins in black goji berries.

[0045] When citric acid (AA-2βG) is applied to the processing of black goji berries, it can effectively maintain or even enhance the red hue of processed black goji berry products, inhibit the increase in brightness value of processed black goji berry products during storage, and inhibit the degradation of anthocyanins in black goji berries.

[0046] Furthermore, the product is a food additive, color protectant, antioxidant, or auxiliary material used in the processing of black goji berries.

[0047] A processed product of black goji berries with highly stable anthocyanins, comprising black goji berry raw material and citric acid (AA-2βG).

[0048] This product maintains the distinctive purplish-red appearance of black goji berries throughout its shelf life, unlike traditional products which brown rapidly. Furthermore, due to the presence of citric acid (AA-2βG), its L value decreases, keeping the product a deep purplish-black. This product preserves the iconic dark color of black goji berries, enhancing market recognition. Moreover, its color after storage is closer to its initial state when freshly prepared, resulting in high color fidelity and a better consumer experience.

[0049] Specifically, the product is black goji berry juice, black goji berry pulp, black goji berry powder, or black goji berry extract solution.

[0050] Specifically, the amount of citric acid (AA-2βG) added is such that its concentration in the processed black goji berry product reaches 0.3 mg / mL-1.5 mg / mL.

[0051] The following specific experimental examples further illustrate the technical solution and effects of the present invention. It should be noted that the following experimental examples are only for further explanation of the present invention and do not limit the technical solution of the present invention.

[0052] Comparative Example 1

[0053] Accurately weigh 0.5 g of black goji berry anthocyanin extract (containing 1.0% proanthocyanidins) into a beaker, prepare VC solutions with concentrations of 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% and add them to the beakers respectively. Mix and dissolve the solutions in a 100 mL volumetric flask. After the prepared solutions are placed under room temperature and light for 1 day, 2 days, and 3 days, the color and anthocyanin content are measured.

[0054] Example 1

[0055] Accurately weigh 0.5 g of black goji berry anthocyanin extract (containing 1.0% proanthocyanidins) into a beaker. Prepare citric acid (AA-2βG) solutions with concentrations of 0%, 0.3%, 0.6%, 0.9%, 1.2%, and 1.5% and add them to the beakers respectively. Mix and dissolve the solutions in 100 mL volumetric flasks. After standing for 1 day, 2 days, and 3 days respectively, measure the color and anthocyanin content.

[0056] The L (brightness) and a (redness) values ​​of the solutions in Comparative Example 1 and Example 1 were measured using a CM-5 spectrophotometer, and the results are as follows: Figures 3 to 6As shown; the absorbance of the solutions in Comparative Example 1 and Example 1 was measured at 510 nm and 700 nm using the pH differential method, respectively. The detection results are as follows. Figure 7 and Figure 8 As shown.

[0057] like Figures 3 to 6 As shown, unlike the addition of vitamin C which increases the L value and decreases the a value, the addition of citric acid (AA-2βG) decreases the L value and increases the a value, with the color-protecting effect becoming more pronounced with prolonged storage. At a concentration of 1.5 mg / mL of citric acid (AA-2βG), the redness a value of the AA-2βG group was 20.4% higher than that of the vitamin C group after 1 day of storage, and 1.6 times higher after 3 days.

[0058] like Figure 5 and Figure 6 As shown, the anthocyanin content in each group with added citric acid (AA-2βG) remained stable over 3 days without significant decrease, while the anthocyanin content in each group with added vitamin C decreased significantly over time.

[0059] The results showed that citric acid (AA-2βG) had excellent protective effects on the color and content of anthocyanins in black wolfberry, and its effect was significantly better than that of vitamin C.

[0060] Comparative Example 2

[0061] Dried black goji berries were rehydrated at a ratio of 1:10, then juiced. Before pulping, different concentrations of vitamin C were added to soak the berries. The concentrations of added vitamin C were 0, 0.3, 0.6, 0.9, 1.2, and 1.5 mg / mL, respectively. Black goji berry juice was then prepared according to the normal process. After the prepared black goji berry juice was placed under room temperature and light for 1, 2, and 3 days, its color and anthocyanin content were measured.

[0062] Example 2

[0063] Dried black goji berries were rehydrated at a ratio of 1:10, then juiced. Before pulping, different concentrations of citric acid (AA-2βG) were added to soak the berries. The concentrations of citric acid (AA-2βG) added were 0, 0.3, 0.6, 0.9, 1.2, and 1.5 mg / mL, respectively. Black goji berry juice was then prepared according to the normal process. The prepared black goji berry juice was left to stand under room temperature and light for 1 day, 2 days, and 3 days, and its color and anthocyanin content were measured.

[0064] The L (brightness) and a (redness) values ​​of the solutions in Comparative Example 2 and Example 2 were measured using a CM-5 spectrophotometer, and the results are as follows: Figures 9 to 12 As shown in Table 1.

[0065]

[0066] like Figures 9 to 12 As shown, the L value of black goji berry juice with added citric acid (AA-2βG) showed a decreasing trend, and the a value at high concentration was close to the initial value, indicating that the red color was maintained. However, the a value of the high concentration group with added vitamin C decreased significantly after 3 days.

[0067] As shown in Table 1, under the same storage time and concentration, the color difference value ∆E of the VC group was higher than that of the citric acid (AA-2βG) group, indicating that the color of the citric acid (AA-2βG) group was closer to the initial color of freshly prepared samples.

[0068] The above results indicate that, in actual food matrix systems, citric acid (AA-2βG) has a significantly better color-protecting effect on black goji berry juice than vitamin C, especially when the mass concentration of citric acid (AA-2βG) is between 0.9 mg / mL and 1.5 mg / mL, the effect is optimal.

[0069] In summary, the method provided by this invention, by adding lycopene acid (AA-2βG) during the processing of black goji berries, can effectively improve the stability of anthocyanins, protect the color of the product, overcome the shortcomings of the prior art, and has high value for industrial application.

[0070] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in the present invention, and such modifications or substitutions should all be covered within the scope of protection of the present invention.

Claims

1. A method for improving the stability of anthocyanins in black goji berries using citric acid, characterized in that, Adding citric acid to black goji berry raw materials or their processed products allows citric acid to interact with anthocyanins from black goji berries via intramolecular or intermolecular color-enhancing effects, thereby inhibiting the degradation of anthocyanins and the deterioration of the product's color.

2. The method for improving the stability of anthocyanins in black goji berries using citric acid according to claim 1, characterized in that, The black goji berry raw materials or their processed products include fresh black goji berries, pulp, juice, powder, extracts, as well as food, health products or beverages prepared using black goji berries as raw materials.

3. The method for improving the stability of anthocyanins in black goji berries using citric acid according to claim 1, characterized in that, The concentration of citric acid added is 0.3 mg / mL-1.5 mg / mL.

4. The method for improving the stability of anthocyanins in black goji berries using citric acid according to claim 1, characterized in that, The method of addition is to dissolve citric acid and then add the dissolved citric acid to the black goji berry raw material or its processed products in a normal way. The mixture is then shaken or stirred to ensure thorough mixing with the black goji berry raw material or its processed products, avoiding over-stirring.

5. The method for improving the stability of anthocyanins in black goji berries using citric acid according to claim 1, characterized in that, The method is used to maintain or enhance the red hue (a value) of processed black goji berry products, reduce their brightness value (L value), and protect the product's color.

6. Application of citric acid in products used to improve the stability of anthocyanins in black goji berries, protect the color of processed black goji berry products, or inhibit the degradation of anthocyanins in black goji berries.

7. The application according to claim 6, characterized in that, The product is a food additive, color protectant, antioxidant, or auxiliary material used in the processing of black goji berries.

8. A processed product of black goji berries with highly stable anthocyanins, characterized in that, It contains black goji berry raw materials and lycopene.

9. The processed black goji berry product according to claim 8, characterized in that, The product is black goji berry juice, black goji berry pulp, black goji berry powder, or black goji berry extract solution.

10. The processed black goji berry product according to claim 9, characterized in that, The amount of citric acid added is such that its concentration in the processed black goji berry product reaches 0.3 mg / mL-1.5 mg / mL.

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