Method for removing hexanal in ginger oil

Abstract

The invention provides a method for removing hexanal in ginger oil, and belongs to the technical field of ginger oil separation and purification. The specific method comprises the following steps: mixing hexanal-containing ginger oil and lactic acid bacteria cell fermentation liquor according to a mass ratio of (5: 1)-(10: 1), continuously oscillating to form an emulsion, and reacting at 35-40 DEG C for 0.2-2 hours; and after the reaction is finished, adjusting the pH value of the reaction liquid to 6.8-7.5, standing to an obvious oil-water separation state, introducing into an oil-water separation system, and separating an oil phase to obtain the hexanal-removed ginger oil. According to the method, more than 95% of hexanal in the ginger oil can be removed, after the hexanal is removed, the fermentation liquor of the lactic acid bacteria does not influence the original components of the ginger oil, the flavor of the ginger oil is not changed, and the method is low in cost, simple to operate, reusable in lactic acid bacteria fermentation liquor and economic and practical.

Description

Technical Field

[0001] The invention relates to the technical field of separation and purification of ginger oil, and in particular to a method for removing hexanal in ginger oil. Background Art

[0002] Ginger oil, also known as ginger oil, is a pale yellow to yellow liquid with a distinctive odor and pungent flavor. It has the characteristic aroma of ginger. Its density is 0.877-0.888. Its refractive index is 1.488-1.494 (20°C). Its optical rotation is -28°C to 45°C. Its saponification value is ≤20. It is insoluble in water, glycerin, and ethylene glycol, but soluble in ethanol, ether, chloroform, mineral oil, and most animal and vegetable oils. The main components of ginger oil are zingiberene, shogaol, gingerol, zingerone, citral, phellandrene, and borneol. It is primarily used in the preparation of edible flavors, various alcoholic beverages, soft drinks, and candies, as well as in cosmetics such as perfumes.

[0003] Steam distillation is one of the most commonly used methods for extracting ginger oil. Its principle, based on the volatility and water insolubility of ginger oil, involves using steam to carry and separate the ginger oil. Ginger oil production methods primarily include traditional pressing, steam distillation, solvent extraction, and supercritical extraction. Ginger oil produced using different production processes using ginger as a raw material varies in composition, content, chemical properties, and edible properties. Ginger oil produced using steam distillation of dried ginger powder is called volatile ginger oil, also known as distilled ginger oil; ginger oil produced using organic solvent extraction is called concentrated ginger oil, also known as ginger resin; ginger oil produced using fresh ginger as a raw material through pressing and centrifugal separation is called cold-pressed ginger oil; and ginger oil obtained using supercritical carbon dioxide extraction is ginger essential oil or SFE\CO2 ginger oil.

[0004] The present invention studies ginger oil produced by steam distillation using dried ginger powder as raw material, and its preparation method complies with the provisions of the Chinese national standard GB 1886.29-2015. Because the ginger raw material contains a certain amount of impurities, the ginger oil prepared by this method will contain a small amount of hexanal during the production process. Hexanal is an organic compound with the chemical formula C6H 12 Hexanal (HEXA) is a colorless, transparent liquid primarily used in the synthesis of fragrances, the preparation of hexanoic acid, and as a gas chromatography reagent. It is a key component in the beany odor of soy products, the off-flavor of rabbit meat, and the off-flavor of meat products (a deterioration caused by heating and refrigeration cycles). High levels of hexanal can cause off-flavors in ginger essential oil, making the removal of hexanal from ginger oil produced by traditional steam distillation a technical challenge.

[0005] Hexanal has a molecular weight of 100.16, CAS number 66-25-1, a melting point of -56°C, and a boiling point of 127.9°C. It is insoluble in water but readily soluble in organic solvents such as ethanol and ether. Therefore, both chemical and physical methods are difficult to remove hexanal from ginger essential oil. The present invention successfully removes hexanal from ginger essential oil by using a microbial metabolism method, which is of great help in improving the quality of ginger essential oil. Summary of the Invention

[0006] In order to solve the problem of hexanal impurities appearing in the production of ginger oil due to uneven ginger raw materials, the present invention uses lactic acid bacteria fermentation liquid to react with ginger oil, and then performs oil-water separation after the reaction, thereby removing hexanal in the ginger oil, improving the odor perception of the ginger oil, removing the unpleasant odor caused by hexanal, and further improving the purity of the ginger oil.

[0007] The specific scheme of removing hexanal in ginger oil of the present invention comprises the following steps.

[0008] ① Inoculate at least one lactic acid bacteria into a sterilized liquid MRS culture medium, and culture it anaerobically at a constant temperature of 35-40°C for 24-48 hours to obtain an activated lactic acid bacteria liquid;

[0009] ② Preparation of lactic acid bacteria culture liquid: inoculate the activated lactic acid bacteria liquid on the sterile MRS liquid medium, ferment at 35-40°C, and stop fermentation when the glucose concentration is lower than 0.1%;

[0010] ③ The fermentation liquid is allowed to stand, and the sediment in the fermentation liquid is crushed to obtain lactic acid bacteria cell fermentation liquid;

[0011] ④ The ginger oil containing hexanal is mixed with the above-mentioned lactic acid bacteria cell fermentation liquid in a mass ratio of 5:1 to 10:1, and the mixture is continuously shaken to form an emulsion. The mixture is reacted at 35 to 40° C. for 0.2 to 2 hours. After the reaction is completed, the pH of the reaction liquid is adjusted to between 6.8 and 7.5. After standing until an obvious oil-water separation state is achieved, the mixture is passed into an oil-water separation system to separate the oil phase to obtain ginger oil from which the hexanal has been removed.

[0012] Wherein, the MRS culture medium contains 5-20 g / L of peptone, 10-50 g / L of glucose, and 2-8 g / L of sodium acetate.

[0013] During the fermentation process, the concentration of glucose in the culture medium was detected every 0.5 to 2 hours.

[0014] After the reaction is completed, the pH of the reaction solution is adjusted to between 6.8 and 7.5 using 0.05-2 M NaOH.

[0015] Wherein, in step ④, the standing temperature is 0-4°C.

[0016] Wherein, the lactic acid bacteria include Lactobacillus plantarum, Streptococcus thermophilus and Lactobacillus bulgaricus. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 The gas chromatograms of ginger oil before and after treatment in Example 1 are shown.

[0018] Figure 2 The gas chromatograms of ginger oil before and after treatment in Example 2 are shown.

[0019] Figure 3 The gas chromatogram of ginger oil before and after treatment in Example 3.

[0020] Figure 4 This is the gas chromatogram of ginger oil before and after treatment in Comparative Example 1.

[0021] Beneficial effects

[0022] Since ginger raw materials contain a certain amount of impurities, a small amount of hexanal will be produced in ginger oil produced by distillation. The average hexanal content is generally between 0.8 and 1%, which is related to each batch of ginger raw materials. A high hexanal content will cause a certain odor in the ginger oil. Therefore, removing hexanal from ginger oil becomes the key to purifying ginger oil in the factory.

[0023] The traditional method of washing with water can wash away most of the impurities in the ginger oil, but because hexanal is incompatible with water, traditional washing cannot remove the hexanal in the ginger oil. The present invention adopts the method of microorganism, first dissolves hexanal by lactobacillus fermentation liquid and metabolites, hexanal is turned into water-soluble material, then by washing with water, more than 95% of hexanal can be removed, after removal, according to the before and after comparison of volatile substances in the ginger oil, the fermentation liquid of lactobacillus does not affect the original composition of ginger oil, and its local flavor does not change. The inventor has also studied the fermentation mechanism of lactobacillus, and adopted 1% lactic acid to process ginger oil. It was found that 1% lactic acid aqueous solution can not effectively remove the hexanal in the ginger oil, which shows that it should be a certain lactobacillus metabolite that reacts with hexanal. Research also shows that the fermentation cell liquid of plant lactobacillus is better than that of thermophilic streptococcus and bulgaricus lactobacillus, and the material that specifically reacts with hexanal also needs to be purified and tested repeatedly, which may also be the result of the combined action of mixed substances.

[0024] According to the experimental results of the inventors, it was found that if the glucose content in the fermentation broth is too high, it will affect the flavor and volatile substances of the ginger oil. Glucose, as a highly reducing substance, is easy to participate in the later redox reaction. The culture medium of lactic acid bacteria has little effect on the experimental results.

[0025] The invention has low cost and simple operation and does not require special equipment. Current research results show that Lactobacillus plantarum is better. Different lactic acid bacteria have certain differences in effect, but all have the effect of reducing hexanal. Moreover, the lactic acid bacteria fermentation liquid can be reused, which is economical and practical. DETAILED DESCRIPTION

[0026] In order to make the objects, characteristics and advantages of the present invention more clear, the present invention will be further explained with reference to the accompanying drawings and specific embodiments below. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, modifications of various equivalent forms of the present invention by those skilled in the art will fall within the scope specified by the claims attached to this application.

[0027] This example uses an Agilent gas chromatograph-mass spectrometer, a vortex oscillator, and an oil-water separation system purchased from Zhejiang Qike Fluid Equipment Co., Ltd.

[0028] The plant lactobacillus used in Example 1 was purchased from Shandong Zhongke Jiayi Bioengineering Co., Ltd., specifically plant lactobacillus JVLP326. The plant lactobacillus used in Example 2 was isolated from Anhui Agricultural University with a preservation number of CCTCC No: M2020289. The mixed lactic acid bacteria used in Example 3 was purchased from Danisco, and the mixed strain model was YO-MIX505, specifically a composite strain of Streptococcus thermophilus and Lactobacillus bulgaricus. Other reagents were all food-grade additives.

[0029] In the examples, the ginger oil is ginger oil (0301) produced by our company, and the ginger is produced in Yulin, Guangxi or Luoping, Yunnan. The method for preparing ginger oil is shown in GB 1886.29-2015.

[0030] In the examples, the volatile components in ginger oil were determined using an Agilent gas chromatography-mass spectrometer, and the specific method is as follows.

[0031] ① Take the ginger essential oil sample and pass it through a 0.22μm filter membrane, absorb the filtrate, and wait for analysis on the machine.

[0032] ②Specific computer conditions are as follows:

[0033] Chromatographic column: Agilent HP-5MS, 30 m × 0.25 mm × 0.25 μm.

[0034] Inlet temperature: 250°C; column temperature: starting temperature 60°C, hold for 2 min, then increase the temperature to 150°C at a heating rate of 3°C / min; then increase the temperature to 180°C at a heating rate of 1°C / min; then increase the temperature to 220°C at a heating rate of 5°C / min, and hold the temperature for 5 min.

[0035] Carrier gas: helium, purity ≥99.999%, flow rate 1.0 mL / min.

[0036] Injection method and injection volume: split ratio 80:1, injection volume 0.2 μL.

[0037] Ionization method: electron bombardment ionization source (EI);

[0038] Ionization energy: 70 eV;

[0039] Transmission line temperature: 280°C;

[0040] Ion source temperature: 230°C;

[0041] Monitoring mode: Full scan (SCAN): Mass scanning range: 33~550amu.

[0042] ③ Spectral analysis: Fatty acid methyl esters were searched and compared with the computer standard spectrum library NIST.14.

[0043] Example 1

[0044] The present embodiment provides a method for removing hexanal in ginger oil, which specifically comprises the following steps:

[0045] 1. Activation of lactic acid bacteria: Inoculate the Lactobacillus plantarum JVLP326 strain into a sterilized liquid MRS culture medium and culture it anaerobically at a constant temperature of 37°C for 24-48 hours to obtain an activated Lactobacillus plantarum bacterial liquid.

[0046] 2. Preparation of lactic acid bacteria culture fluid: Take 10.0g of peptone, 20.0g of glucose, and 5.0g of sodium acetate, dissolve them in 1L of sterile water, and sterilize them by high pressure to obtain sterile MRS medium. Inoculate the plant lactobacillus culture fluid in the above-mentioned MRS medium, and ferment under the condition of 37°C. During the fermentation process, the concentration of glucose in the culture fluid is detected every 2h. Fermentation is stopped when the concentration of glucose is lower than 0.1%.

[0047] 3. After the fermentation liquid is allowed to stand for 1 hour, the precipitate in the fermentation liquid is crushed at room temperature to obtain lactic acid bacteria cell fermentation liquid.

[0048] 4. Take the ginger oil produced by yourself, mix it with the above-mentioned lactic acid bacteria cell fermentation liquid in a mass ratio of 6:1, and continuously shake it for 1 hour to form an emulsion. React at 37°C for 1 hour. After the reaction, adjust the pH of the reaction liquid to 7 with 0.1M NaOH solution. Let it stand at 0-4°C for 2-5 days until a relatively obvious oil-water separation state is achieved. Then, pass it into an oil-water separation system to separate the oil to obtain the treated ginger oil.

[0049] The volatile components in ginger oil before and after treatment were determined respectively. The specific results are as follows: Figure 1 shown.

[0050] Depend on Figure 1 It can be seen that the hexanal content of the ginger oil before treatment in this embodiment is 0.8490%. After treatment with the lactic acid bacteria fermentation broth, the hexanal content is reduced to 0.0770%. Basically, all the hexanal is removed, and the remaining hexanal can be ignored.

[0051] Table 1 is the peak area graph of 1 to 9 before treatment, and Table 2 is the peak area graph of 1 to 9 after treatment. According to the standard spectrum library NIST.14, the first peak is hexanal.

[0052] Table 1: Volatile matter content before treatment in Example 1 (excerpt)

[0053]

[0054] Table 2: Volatile matter content after treatment in Example 1 (excerpt)

[0055]

[0056] Example 2

[0057] This example provides a method for removing hexanal from ginger oil. The mixed lactic acid bacteria in this example were purchased from Danisco. The mixed strain model is YO-MIX505, specifically a composite strain of Streptococcus thermophilus and Lactobacillus bulgaricus. The method specifically includes the following steps:

[0058] 1. Activation of lactic acid bacteria: The mixed lactic acid bacteria were inoculated into the sterilized liquid MRS culture medium and cultured anaerobically at a constant temperature of 40°C for 24 hours to obtain an activated Lactobacillus plantarum bacterial liquid.

[0059] 2. Preparation of lactic acid bacteria culture fluid: Take 20.0g of peptone, 50.0g of glucose, and 8.0g of sodium acetate, dissolve them in 1L of sterile water, and sterilize them by high pressure to obtain sterile MRS medium. Inoculate the plant lactobacillus culture fluid in the above-mentioned MRS medium, and ferment under 40°C conditions. During the fermentation process, the concentration of glucose in the culture fluid is detected every 3h. Fermentation is stopped when the concentration of glucose is lower than 0.1%.

[0060] 3. After the fermentation liquid was allowed to stand for 0.5 h, the precipitate in the fermentation liquid was crushed at room temperature to obtain lactic acid bacteria cell fermentation liquid.

[0061] 4. Take the ginger oil produced by yourself, mix it with the above-mentioned lactic acid bacteria cell fermentation broth in a mass ratio of 10:1, and continuously shake it for 2 hours to form an emulsion. React at 40°C for 0.2 hours. After the reaction, adjust the pH of the reaction solution to 7.5 with 0.05M NaOH solution. Let it stand at 0-4°C for 2-5 days until a relatively obvious oil-water separation state is achieved. Then, pass it into an oil-water separation system to separate the oil to obtain the treated ginger oil.

[0062] The volatile components in ginger oil before and after treatment were determined respectively. The specific results are as follows: Figure 3 shown.

[0063] Depend on Figure 3 It can be seen that the hexanal content of the ginger oil before treatment in this embodiment is 0.9045%. After treatment with the lactic acid bacteria fermentation broth, the hexanal content is reduced to 0.0763%, which means that basically all the hexanal is removed and the remaining hexanal can be ignored.

[0064] Table 5 is a graph showing the peak areas of 1 to 9 before treatment, and Table 6 is a graph showing the peak areas of 1 to 9 after treatment. According to the standard spectrum library NIST.14, the first peak is hexanal.

[0065] Table 3: Volatile matter content before treatment in Example 2 (excerpt)

[0066]

[0067] Table 4: Volatile matter content after treatment in Example 2 (excerpt)

[0068]

[0069] Example 3

[0070] This embodiment provides a method for removing hexanal from ginger oil. The mixed lactic acid bacteria in this embodiment were purchased from Danisco. The mixed strain model is YO-MIX505, specifically a composite strain of Streptococcus thermophilus and Lactobacillus bulgaricus. The method specifically includes the following steps:

[0071] 1. Activation of lactic acid bacteria: The mixed lactic acid bacteria were inoculated into the sterilized liquid MRS culture medium and cultured anaerobically at a constant temperature of 35°C for 48 hours to obtain an activated mixed lactic acid bacteria liquid.

[0072] 2. Preparation of lactic acid bacteria culture medium: Take 5.0 g of peptone, 10.0 g of glucose, and 2.0 g of sodium acetate, dissolve them in 1 L of sterile water, and sterilize them by high pressure to obtain sterile MRS medium. Inoculate mixed lactic acid bacteria into the above MRS medium and ferment at 35°C. During the fermentation process, the glucose concentration in the culture medium is detected every 1 h. Fermentation is stopped when the glucose concentration is lower than 0.1%.

[0073] 3. After the fermentation liquid is allowed to stand for 2 hours, the precipitate in the fermentation liquid is crushed at room temperature to obtain lactic acid bacteria cell fermentation liquid.

[0074] 4. Take the ginger oil produced by yourself, mix it with the above-mentioned lactic acid bacteria cell fermentation liquid in a mass ratio of 5:1, and continuously shake it for 0.5 hours to form an emulsion. React at 35°C for 2 hours. After the reaction, adjust the pH of the reaction liquid to 6.8 with 0.1M NaOH solution. Let it stand at 0-4°C for 2-5 days until a relatively obvious oil-water separation state is achieved. Then, pass it into an oil-water separation system to separate the oil to obtain the treated ginger oil.

[0075] The volatile components in ginger oil before and after treatment were determined respectively. The specific results are as follows: Figure 2 shown.

[0076] Depend on Figure 2 It can be seen that the hexanal content of the ginger oil before treatment in this embodiment is 0.7815%. After treatment with the lactic acid bacteria fermentation broth, the hexanal content is reduced to 0.1606%, which means that basically all the hexanal is removed and the remaining hexanal can be ignored.

[0077] Table 3 is a graph showing the peak areas of 1 to 9 before treatment, and Table 4 is a graph showing the peak areas of 1 to 9 after treatment. According to the standard spectrum library NIST.14, the first peak is hexanal.

[0078] Table 5: Volatile matter content before treatment in Example 3 (excerpt)

[0079]

[0080] Table 6: Volatile matter content after treatment in Example 3 (excerpt)

[0081]

[0082] Comparative Example 1

[0083] To verify the effectiveness of lactic acid aqueous solution in removing hexanal from ginger oil, the inventors prepared a comparative example using 1% lactic acid treatment. Specifically, homemade ginger oil was taken and mixed with 1% lactic acid aqueous solution in a mass ratio of 6:1. The mixture was continuously shaken for 1 hour to form an emulsion. The mixture was reacted at 37°C for 1 hour. After the reaction, the pH of the reaction solution was adjusted to 7 with 0.1M NaOH solution. The mixture was allowed to stand at 0-4°C for 2-5 days until a relatively obvious oil-water separation state was achieved. The mixture was then passed into an oil-water separation system to separate the oil and obtain the treated ginger oil.

[0084] The volatile components in ginger oil before and after treatment were determined respectively. The specific results are as follows: Figure 4 shown.

[0085] Depend on Figure 4 It can be seen that the hexanal content of the ginger oil before treatment in this embodiment is 0.9601%. After treatment with the lactic acid aqueous solution, the hexanal content is reduced to 0.8484%. This shows that the lactic acid aqueous solution treatment cannot significantly reduce the hexanal content.

[0086] Table 7: Volatile substance content before treatment in Comparative Example 1 (excerpt, the second peak is hexanal)

[0087]

[0088] Table 8: Volatile substance content after treatment in Comparative Example 1 (the second peak is hexanal)

[0089]

Claims

1. A method for removing hexanal in ginger oil, characterized in that, The method for removing hexanal comprises the steps: ① Inoculate at least one lactic acid bacteria into a sterilized liquid MRS culture medium, and culture it anaerobically at a constant temperature of 35-40°C for 24-48 hours to obtain an activated lactic acid bacteria liquid; ② Preparation of lactic acid bacteria culture liquid: Inoculate the activated lactic acid bacteria liquid into the sterile MRS liquid medium, ferment at 35-40℃, and stop fermentation when the glucose concentration is lower than 0.1%; ③ The fermentation liquid is allowed to stand, and the sediment in the fermentation liquid is crushed to obtain lactic acid bacteria cell fermentation liquid; ④ The ginger oil containing hexanal is mixed with the above-mentioned lactic acid bacteria cell fermentation broth in a mass ratio of 5:1 to 10:1, and the mixture is continuously shaken to form an emulsion. The mixture is reacted at 35 to 40°C for 0.2 to 2 hours. After the reaction is completed, the pH of the reaction solution is adjusted to between 6.8 and 7.

5. After standing until an obvious oil-water separation state is achieved, the oil phase is separated to obtain the ginger oil from which the hexanal has been removed.

2. the method for removing hexanal in ginger oil according to claim 1, is characterized in that, The MRS culture medium contains 5-20 g / L of peptone, 10-50 g / L of glucose, and 2-8 g / L of sodium acetate.

3. The method for removing hexanal in ginger oil according to claim 1, wherein During the fermentation process, the glucose concentration in the culture medium was detected every 0.5 to 2 hours.

4. the method for removing hexanal in ginger oil according to claim 1, is characterized in that, After the reaction is completed, the pH of the reaction solution is adjusted to between 6.8 and 7.5 with 0.05-2 M NaOH.

5. the method for removing hexanal in ginger oil according to claim 1, is characterized in that, In step ④, the standing temperature is 0-4°C.

6. The method for removing hexanal in ginger oil according to claim 1, wherein The lactic acid bacteria include Lactobacillus plantarum, Streptococcus thermophilus and Lactobacillus bulgaricus.

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