Preparation method and production method of water-based Chinese prickly ash flavor extracting solution

Abstract

The invention discloses a preparation method and a production method of a water-based zanthoxylum bungeanum flavor extracting solution, and relates to the technical field of food additives, and the preparation method comprises the following steps: (1) raw material treatment: crushing dried zanthoxylum bungeanum to a predetermined particle size; (2) frequency-division ultrasonic extraction: carrying out first-stage extraction on the mixture of the paprika powder and the edible alcohol by adopting low-frequency ultrasonic waves, and breaking cell walls to release effective components; performing second-stage extraction on the first-stage extraction liquid by adopting high-frequency ultrasonic waves to accelerate diffusion and dissolution of effective components; (3) solid-liquid separation: filtering to remove solid residues to obtain a primary extracting solution; (4) surface active agent embedding: adding a nonionic surface active agent into the primary extracting solution, and embedding the terpenoids; (5) gradient dilution: adding water for dilution by stages to avoid turbidity caused by polarity mutation of the solution; and composite color protection treatment: adjusting the diluent to a weakly alkaline condition, adding a magnesium ion displacer, a buffer agent, a stabilizer and a preservative, and maintaining the color of the solution stable.

Description

Technical Field

[0001] The present invention relates to the technical field of food processing, and more specifically, to a preparation method and a production method of a water-based pepper flavor extract. It is applicable to dissolving the special flavors of green peppers and red peppers into water-soluble beverages. Background Art

[0002] Pepper is an economic crop that can be used both as medicine and food, and its fruit is known as "one of the eight seasonings". For a long time, the aroma and taste components of pepper cannot be dissolved in water, which greatly limits the application range of pepper. The prior art discloses a method for ultrasonic-assisted extraction of the numbing flavor substances of pepper, but it does not solve the problems of poor dispersion of fat-soluble components in the water-based system and color change during long-term storage. The present invention significantly improves the stability and sensory quality of the water-based pepper flavor liquid through frequency-divided ultrasonic extraction, gradient dilution, and composite color protection technology. Summary of the Invention

[0003] The purpose of the present invention is to provide a preparation method and a production method of a water-based pepper flavor extract in order to solve the technical problems existing in the background art. The present invention first dissolves the aroma and taste components in pepper into edible alcohol through ultrasonic extraction technology to obtain an extract, and then adds a food-grade surfactant to the extract. After dilution with water and undergoing anti-corrosion and color protection treatments, it is the water-based pepper flavor extract. The extract can be added to various foods such as soft drinks, flour products, and chicken essence to impart the pepper flavor to the foods. When this product is used, it should be diluted at least 10 times (the addition amount of this product ≤ 10%).

[0004] The present invention realizes the above purpose through the following technical solutions:

[0005] A preparation method of a water-based pepper flavor extract includes the following steps:

[0006] (1) Raw material treatment: crushing the dried pepper to a predetermined particle size;

[0007] (2) Frequency-divided ultrasonic extraction:

[0008] Using low-frequency ultrasonic waves to perform the first-stage extraction on the mixture of pepper powder and edible alcohol to break the cell wall and release the active ingredients; the cavitation effect generated by the low-frequency ultrasonic waves breaks the cell wall of the pepper to release the active substances.

[0009] Using high-frequency ultrasonic waves to perform the second-stage extraction on the first-stage extraction liquid; promoting the dissolution of small molecules, making the solvent molecules move more violently, and the formed microscopic flow field can accelerate the diffusion of the active ingredients from the inside of the pepper to the solvent, shortening the extraction time.

[0010] The two-stage synergistic effect shortens the total extraction time by more than 30%. When using ultrasonic extraction, water-soluble heat preservation is adopted to ensure that the extraction temperature of edible alcohol is not lower than 50 °C and not higher than 55 °C.

[0011] (3) Solid-liquid separation: Filter to remove solid residues to obtain a primary extract.

[0012] (4) Surfactant embedding: Add a non-ionic surfactant to the primary extract to embed the dissolved terpene substances.

[0013] (5) Gradient dilution: Dilute by adding water in stages to prevent the solution from becoming turbid due to a sudden change in molecular polarity. Avoid turbidity caused by a sudden change in solution polarity. The dilution includes mixing the pre-diluted liquid with a large amount of water to form an aqueous-based extract.

[0014] (6) Composite color protection treatment: Adjust the diluted solution to a weakly alkaline condition and add a metal ion replacement agent, buffer, and preservative to maintain the color stability of the solution. The color protection includes: preparing a sodium bicarbonate buffer solution and using a preservative for anti-corrosion treatment to maintain its pH value at about 8.3, preventing the chlorophyll in the extract using Zanthoxylum schinifolium as the raw material from changing to pheophytin when the pH of the solution is less than 7 due to cell decomposition and microbial growth, resulting in color change. In addition, use the food additive zinc sulfate as a color protection agent to replace unstable magnesium ions with zinc ions.

[0015] The predetermined particle size in step (1) is the powder passing through a 3-4 mm sieve.

[0016] In step (2): The frequency of the low-frequency ultrasonic wave is 20-40 kHz, the power density is 100-300 W / L, and the extraction time is 40-45 minutes. The frequency of the high-frequency ultrasonic wave is 80-100 kHz, the power density is 100-300 W / L, and the extraction time is 10-15 minutes. The ultrasonic frequency is 80-100 kHz, and the two-stage ultrasonic power density is 100-300 W / L. The purpose of using ultrasonic waves with a higher frequency is to make the solvent molecules move more violently, and the formed microscopic flow field can accelerate the diffusion of active ingredients from the inside of the Chinese prickly ash to the solvent.

[0017] The concentration of the edible alcohol in step (2) is 95% (v / v), and the extraction temperature is 50-55 °C.

[0018] In step (4), the non-ionic surfactant is Tween 80, and the addition amount is less than 8‰ (w / w). Adding Tween 80 surfactant to wrap the terpene substances released from Chinese prickly ash can prevent the solution from becoming turbid when added to water. The addition amount of Tween 80 should comply with the limit in GB2760. Since the intended use of this product is not for direct consumption but for consumption after being added to food, and the addition amount of this product is 10%, the limit of the additives added to this product should be less than 10 times the limit for use in food specified in GB2760, so that after making it into a directly edible food, the additive limit is lower than the limit for use in food specified in GB2760.

[0019] In step (5), the gradient dilution includes:

[0020] Pre-dilution stage: The temperature of the pre-dilution water is 4 - 25°C, the mass of water is equal to the mass of the extract, and the stirring rate is 20 - 30 rpm; By pre-diluting (slowly adding water), the turbidity of the solution caused by polarity mutation is avoided, and the clarity of the solution is maintained.

[0021] Final dilution stage: Mix the pre-diluted solution and water at a mass ratio of 1:20.

[0022] In step (6):

[0023] The weak alkaline condition is pH 8.3 ± 0.2, which is achieved by adding 1% (w / w) sodium bicarbonate;

[0024] The metal ion displacing agent is zinc sulfate, and the addition amount is less than 0.06 g / L;

[0025] The buffer includes EDTA, and the addition amount is 0.3‰ (w / w);

[0026] The preservative is potassium sorbate, and the addition amount is 5‰ (w / w).

[0027] In step (6), the metal ion displacing agent displaces the magnesium ion in chlorophyll with zinc ion to stabilize the porphyrin ring structure.

[0028] In the product with green Chinese prickly ash as the raw material, adding zinc sulfate. Since the stability of zinc ion is stronger than that of magnesium ion in chlorophyll, zinc ion is used to displace magnesium ion to make the structure of its porphyrin ring stable, preventing the porphyrin ring of chlorophyll from disintegrating and changing the color.

[0029] Since the intended use of this product is not for direct consumption but for consumption after being added to food, and the addition amount of this product is 10%, the limit of the additives added to this product should be less than 10 times the limit for use in food specified in GB2760, so that after making it into a directly edible food, the additive limit is lower than the limit for use in food specified in GB2760.

[0030] The beneficial effects of the present invention compared with the prior art are as follows:

[0031] 1. Efficient extraction and process optimization:

[0032] Through the synergistic effect of frequency-divided ultrasonic waves (combination of low frequency 20 - 40 kHz and high frequency 80 - 100 kHz), the cavitation effect is utilized to destroy the cell walls of Chinese prickly ash to release active ingredients, and the high-frequency micro-flow field is used to accelerate dissolution. The total extraction time is shortened by more than 30%, and the extraction amount of numbing principle reaches 8.24 - 9.13 mg / g, significantly improving the extraction efficiency and component utilization rate.

[0033] 2. Breakthrough in the stability of the water-based system:

[0034] Non-ionic surfactants (such as Tween 80) are used to encapsulate lipophilic terpene substances, combined with the gradient dilution process (pre-dilution + final dilution), to avoid the turbidity of the solution caused by the sudden change in polarity, realizing the stable dispersion of Chinese prickly ash flavor components in the water-based system and expanding their applications in water-soluble foods such as soft drinks and flour products.

[0035] 3. Long-term color stability:

[0036] Through the composite color protection technology:

[0037] The weak alkaline buffer system (pH 8.3 ± 0.2) inhibits the demagnesiation reaction of chlorophyll;

[0038] Zinc sulfate replaces the magnesium ions in chlorophyll to stabilize the porphyrin ring structure;

[0039] EDTA chelates metal ions, and potassium sorbate inhibits the growth of microorganisms.

[0040] The above-mentioned synergistic effect enables the extract to maintain color stability within 60 days, which is significantly better than the traditional method.

[0041] 4. Safety and compliance:

[0042] The dosages of additives (such as potassium sorbate ≤ 5‰, zinc sulfate < 0.06 g / L) strictly follow the GB2760 standard, and the final product is diluted by more than 10 times during use to ensure that the terminal food meets the regulatory requirements and has both safety and flavor intensity.

[0043] 5. Potential for industrial application:

[0044] The process parameters are clear (such as ultrasonic power density 100 - 300 W / L, gradient dilution ratio, etc.), and the equipment has strong versatility and is suitable for large-scale production, providing technical support for the deep processing of Chinese prickly ash and the development of innovative foods. Detailed implementation methods

[0045] To make the objectives, technical solutions, and advantages of the implementation of the present invention clearer, the technical solutions in the implementation of the present invention will be clearly and completely described below. For those not specifying specific conditions in the examples, they are carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not indicating the manufacturer, they are all conventional products obtained through commercial purchase.

[0046] The present invention provides a method for preparing an aqueous-based prickly ash flavor extract, which comprises the following steps:

[0047] Crushing of dried prickly ash. After the prickly ash is dried, its seeds, branches, and impurities are screened out, and after being crushed by a pulverizer, dry prickly ash powder is obtained through a sieve hole with a pore size of 3 - 4 mm for standby.

[0048] First-stage ultrasonic extraction. Heat edible alcohol to 55°C, and perform ultrasonic extraction at a frequency of 25KHZ and a power of 200w / L in a water bath (water temperature 50°C - 55°C) for heat preservation. Utilize the cavitation effect of low-frequency ultrasonic waves to break the cell walls of prickly ash and separate the flavor and taste substances of prickly ash from the prickly ash cells. The ultrasonic extraction time is 45 minutes.

[0049] Second-stage ultrasonic extraction. The solution obtained from the first-stage ultrasonic extraction is continuously subjected to ultrasonic extraction at a frequency of 90KHZ and a power of 150W / L in a water bath (water temperature 50°C - 55°C) for heat preservation to promote the dissolution of small molecules, make the solvent molecules move more violently, and the formed microscopic flow field can accelerate the diffusion of active ingredients from the inside of prickly ash into the solvent.

[0050] Filtration. Filter out the prickly ash powder with a 0.45μm membrane to obtain the extract.

[0051] Pre-dilution. Add Tween 80, slowly stir the extract, and then slowly add pure water at room temperature and stir slowly. The amount of pure water added is equal to that of the extract. Set aside for use.

[0052] Add 0.05% EDTA, 0.01% potassium sorbate, and 0.06‰ zinc sulfate to pure water, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%) for standby.

[0053] Slowly add the pre-diluted solution to the above solution and stir.

[0054] Example 1

[0055] 1. Take 175g of dried green prickly ash, crush it through a 3mm sieve, and mix it with 500mL of 95% edible alcohol preheated to 55°C;

[0056] 2. Perform ultrasonic treatment at 25kHz and a power of 200W / L for 45 minutes;

[0057] 3. Switch to a power of 90 kHz and 150 W / L and continue to process for 12 min, then filter through a 0.45 μm membrane;

[0058] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0059] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm;

[0060] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0061] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0062] Example 2

[0063] 1. Take 150 g of dry green prickly ash, crush it through a 3 mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0064] 2. Ultrasonically treat at a power of 25 kHz and 200 W / L for 45 min;

[0065] 3. Switch to a power of 90 kHz and 150 W / L and continue to process for 12 min, then filter through a 0.45 μm membrane;

[0066] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0067] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm;

[0068] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0069] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0070] Example 3

[0071] 1. Take 125 g of dry green prickly ash, crush it through a 3 mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0072] 2. Ultrasonically treat at a power of 25 kHz and 200 W / L for 45 min;

[0073] 3. Switch to a power of 90 kHz and 150 W / L and continue to process for 12 min, then filter through a 0.45 μm membrane;

[0074] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0075] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, and stir at a speed of 20 rpm;

[0076] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0077] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0078] Example 4

[0079] 1. Take 175 g of dried green prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0080] 2. Ultrasonically treat it at 25 kHz and a power of 200 W / L for 30 min;

[0081] 3. Switch to 90 kHz and a power of 150 W / L and continue to treat for 12 min, and filter through a 0.45-μm membrane;

[0082] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0083] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, and stir at a speed of 20 rpm;

[0084] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0085] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0086] Example 5

[0087] 1. Take 175 g of dried green prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0088] 2. Ultrasonically treat it at 25 kHz and a power of 200 W / L for 20 min;

[0089] 3. Switch to 90 kHz and a power of 150 W / L and continue to treat for 12 min, and filter through a 0.45-μm membrane;

[0090] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0091] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, and stir at a speed of 20 rpm;

[0092] 6. Dilute the pre-diluent and pure water in a volume ratio of 1:10.

[0093] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0094] Example 6

[0095] 1. Take 175 g of dried wild prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C.

[0096] 2. Ultrasonically treat it at a power of 25 kHz and 200 W / L for 45 min.

[0097] 3. Switch to a power of 90 kHz and 150 W / L and continue to treat for 8 min, then filter through a 0.45-μm membrane.

[0098] 4. Add 8% Tween 80 to the filtrate and stir to mix.

[0099] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm.

[0100] 6. Dilute the pre-diluent and pure water in a volume ratio of 1:10.

[0101] 7. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0102] Example 7

[0103] 1. Take 175 g of dried wild prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C.

[0104] 2. Ultrasonically treat it at a power of 25 kHz and 200 W / L for 45 min.

[0105] 3. Switch to a power of 90 kHz and 150 W / L and continue to treat for 12 min, then filter through a 0.45-μm membrane.

[0106] 4. Add 8% Tween 80 to the filtrate and stir to mix.

[0107] 5. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm.

[0108] 6. Dilute the pre-diluent and pure water in a volume ratio of 1:10.

[0109] 7. Add 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0110] Example 8

[0111] 1. Take 175 g of dry green Chinese prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0112] 2. Perform ultrasonic treatment at a power of 200 W / L and a frequency of 25 kHz for 45 min;

[0113] 3. Switch to a power of 150 W / L and a frequency of 90 kHz, continue the treatment for 12 min, and filter through a 0.45-μm membrane;

[0114] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0115] 5. Add 500 mL of pre-dilution water at 22 °C at a rate of 4 L / min, and the stirring speed is 20 rpm;

[0116] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0117] 7. Add 0.05% EDTA, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0118] Example 9

[0119] 1. Take 175 g of dry green Chinese prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0120] 2. Perform ultrasonic treatment at a power of 200 W / L and a frequency of 25 kHz for 45 min;

[0121] 3. Switch to a power of 150 W / L and a frequency of 90 kHz, continue the treatment for 12 min, and filter through a 0.45-μm membrane;

[0122] 4. Add 8% Tween 80 to the filtrate and stir to mix;

[0123] 5. Add 500 mL of pre-dilution water at 22 °C at a rate of 4 L / min, and the stirring speed is 20 rpm;

[0124] 6. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0125] 7. Add 0.05% EDTA, 0.06‰ zinc sulfate, and 0.01% potassium sorbate.

[0126] Example 10

[0127] 1. Take 175 g of dry green Chinese prickly ash, crush it through a 3-mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0128] 2. Ultrasonically treat for 45 min at a power of 25 kHz and 200 W / L;

[0129] 3. Switch to a power of 90 kHz and 150 W / L and continue to treat for 12 min, then filter through a 0.45 μm membrane;

[0130] 5. Add 8% Tween 80 to the filtrate and stir to mix;

[0131] 6. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm;

[0132] 7. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0133] 8. Add 0.05% EDTA, 0.01% potassium sorbate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0134] Example 11

[0135] 1. Take 175 g of dry wild prickly ash, crush it through a 3 mm sieve, and mix it with 500 mL of 95% edible alcohol preheated to 55 °C;

[0136] 2. Ultrasonically treat for 45 min at a power of 25 kHz and 200 W / L;

[0137] 3. Switch to a power of 90 kHz and 150 W / L and continue to treat for 12 min, then filter through a 0.45 μm membrane;

[0138] 4. Add 500 mL of pre-diluted water at 22 °C at a rate of 4 L / min, with a stirring speed of 20 rpm;

[0139] 5. Dilute the pre-diluted solution and pure water in a volume ratio of 1:10;

[0140] 6. Add 0.05% EDTA, 0.01% potassium sorbate, 0.06‰ zinc sulfate, and adjust the pH to 8.3 with sodium bicarbonate (addition amount 1%).

[0141] Table 1 shows the comparison with different feeding ratios without adding EDTA / potassium sorbate / sodium bicarbonate / Tween 80 / zinc sulfate.

Claims

1. A method for preparing a water-based pepper flavor extract, characterized in that: The following steps are involved: (1) Raw material processing: crushing the dried pepper into a predetermined particle size; (2) Frequency division ultrasonic extraction: The mixture of pepper powder and edible alcohol is first extracted by low-frequency ultrasonic wave to destroy the cell wall and release the effective ingredients; The first extract is subjected to second extraction using high-frequency ultrasound to accelerate the diffusion and dissolution of the active ingredients; (3) Solid-liquid separation: filtering to remove solid residue and obtain primary extract; (4) Surfactant encapsulation: adding a nonionic surfactant to the primary extract to encapsulate the terpenoids; (5) Gradient dilution: by adding water in stages to dilute the solution, turbidity caused by sudden changes in solution polarity can be avoided; (6) Composite color protection treatment: adjust the diluent to a weakly alkaline condition, and add a magnesium ion replacer, a buffer, a stabilizer (compounding agent) and a preservative to maintain the color stability of the solution.

2. The preparation method according to claim 1, characterized in that: The predetermined particle size in step (1) is a powder that passes through a 3-4 mm sieve.

3. The preparation method according to claim 1, characterized in that: In step (2): The frequency of the low-frequency ultrasonic wave is 20-40kHz, the power density is 100-300W / L, and the leaching time is 40-45 minutes.

4. The preparation method according to claim 1, characterized in that: In step (2): the frequency of the high-frequency ultrasound is 80-100 kHz, the power density is 100-300 W / L, and the extraction time is 10-15 minutes.

5. The preparation method according to claim 1, characterized in that: The concentration of the edible alcohol in step (2) is 95% (v / v), and the extraction temperature is 50-55°C.

6. The preparation method according to claim 1, characterized in that: The non-ionic surfactant in step (4) is Tween 80, and the added amount is less than 5‰ (w / w).

7. The preparation method according to claim 1, characterized in that: The gradient dilution in step (5) comprises: Pre-dilution stage: the temperature of the pre-dilution water is 4-25°C, the mass of the water is equal to the mass of the extract, and the stirring rate is 20-30rpm; Final dilution stage: Mix the pre-dilution solution with water in a mass ratio of 1:

20.

8. The preparation method according to claim 1, characterized in that: In step (6): The weak alkaline condition is pH 8.3±0.2, which is achieved by adding 1% (w / w) sodium bicarbonate; The metal ion replacement agent is zinc sulfate, and the addition amount is less than 0.06g / L; The buffer includes EDTA, which is added in an amount of 0.3‰ (w / w); The preservative is potassium sorbate, and the added amount is 5‰ (w / w).

9. The preparation method according to claim 1, characterized in that: In step (6), the metal ion replacer replaces the magnesium ions in the chlorophyll with zinc ions to stabilize the porphyrin ring structure.