A kind of preparation method of lemon extract

Abstract

The invention discloses a preparation method of a lemon extract, and relates to the technical field of plant extraction. The method comprises the following steps: S1, steam distilling lemon peel after enzymolysis to obtain lemon essential oil and extraction residue; S2, crushing lemon pulp to obtain lemon juice and lemon pulp; S21, freeze-drying the lemon pulp to obtain powder; S22, extracting after mixing powder, lemon juice and organic solvent; obtaining an organic phase; S23, concentrating and drying the organic phase to obtain limonin; enzymolysis selects at least one of cellulase, pectinase and hemicellulase. The overall preparation process of the present invention is simple, low in energy consumption, easy to control operating process conditions, easy to realize industrial production, and is a lemon extraction method with great application prospects; the method prepares lemon essential oil, limonin and lemon pectin in the same process flow, and realizes full resource utilization.

Description

Technical Field

[0001] The invention belongs to the technical field of plant extraction, and in particular relates to a method for preparing a lemon extract. Background Art

[0002] At present, the methods for extracting lemon essential oil include pressing, organic solvent extraction, steam distillation, supercritical fluid extraction, etc. However, the extraction rate of direct pressing is usually low; the organic solvent extraction method is prone to cause the loss of volatile components when removing the solvent; although the supercritical fluid extraction method is time-saving, the instrument and equipment cost is high, and there are certain limitations in its application in production practice; steam distillation is the recommended method of the "Chinese Pharmacopoeia", but it takes a long time. Therefore, exploring a method for extracting lemon essential oil with simple operation, high extraction rate and low cost is still the key to the comprehensive utilization of lemon products.

[0003] Lemon pectin is a natural high molecular compound. Lemon pectin usually exists in a partially methylated state, and its basic structure is D-pyranosylgalacturonic acid. At present, the extraction methods of pectin can be summarized as boiling water extraction, acid extraction, ion exchange, microbial method and enzymatic hydrolysis, among which acid extraction is the most widely used. The traditional acid extraction process has many disadvantages: pectin molecules are prone to hydrolysis during the extraction process, which reduces the relative molecular weight of pectin and affects the yield and quality of pectin. The use of a large amount of acid during extraction not only corrodes the equipment but also causes environmental pollution. At the same time, the acid extraction method also has the following problems: the process is long, more solvents are added, and solvent residues; therefore, the development of the acid extraction process is limited.

[0004] Limonin is a type of triterpenoid secondary metabolite found in Rutaceae and Meliaceae plants, and is also the main substance that causes the bitter taste of citrus juice. At present, about 300 limonin compounds have been isolated, and through the study of many compounds, it has been found that it has strong biological activity. Limonin has the ability to scavenge DPPH (1,1-Diphenyl-2-picrylhydrazyl radical, 1,1-diphenyl-2-trinitrophenylhydrazine). The active ingredient free radical directly resists the division and proliferation of cancer cells, achieving anti-cancer and anti-cancer effects. At the same time, limonin also has insecticidal, antiviral, antibacterial, hypnotic, anti-anxiety, sedative, appetite-increasing, digestive function-improving and insect repellent effects. The current methods for separating limonin all use expensive resins, which makes industrial production difficult. Secondly, these methods usually require 4-5 column chromatography cycles to complete, which is cumbersome to operate and will result in huge energy and raw material losses. Thirdly, due to the large number of operations, the product yield is greatly reduced. Finally, the high performance liquid phase method is used in the final purification stage of the related technology, otherwise the purity of the obtained product is low.

[0005] Therefore, the present invention provides a method for preparing a lemon extract to solve the problems raised in the above background technology. Summary of the invention

[0006] The object of the present invention is to provide a method for preparing a lemon extract to solve at least one aspect of the problems and defects raised in the above background technology.

[0007] Specifically, the present invention provides a method for preparing a lemon extract, comprising the following steps:

[0008] S1, enzymatically hydrolyzing lemon peel and then steam distilling to obtain lemon essential oil and extract residue;

[0009] S11, mixing the extraction residue and water, separating the solid and the liquid, and collecting the first liquid phase;

[0010] S12, treating the first liquid phase with a cation exchange resin to obtain a second liquid phase;

[0011] S13, decolorizing and ultrafiltering the second liquid phase to obtain an ultrafiltrate;

[0012] S14, mixing the ultrafiltrate and ethanol aqueous solution, performing filter pressing, distillation, and drying to obtain pectin;

[0013] S2, crushing the lemon pulp to obtain lemon juice and lemon pulp;

[0014] S21, freeze-drying the lemon pulp to obtain powder;

[0015] S22, mixing the powder, lemon juice and an organic solvent and extracting to obtain an organic phase;

[0016] S23, concentrating and drying the organic phase to obtain limonin;

[0017] The enzymatic hydrolysis uses at least one of cellulase, pectinase and hemicellulase;

[0018] There is no particular order for step S1 and step S2.

[0019] According to one technical solution of the extraction method technical solution of the present invention, at least the following beneficial effects are achieved:

[0020] The present invention extracts lemon peel and lemon pulp in different ways to obtain different lemon extracts;

[0021] The preparation method of the present invention utilizes the specificity of enzymes and selects corresponding enzymes to degrade components of cell walls before steam distillation extraction, so that effective components bound in cells are dissolved, thereby achieving the purpose of rapid extraction; after the steam distillation treatment, water is added to dissolve pectin in lemon peel, and components such as cellulose, hemicellulose and lignin are precipitated, thereby achieving preliminary purification of pectin.

[0022] The present invention also utilizes cation exchange resin to extract pectin, thereby greatly improving the extraction rate of pectin;

[0023] The overall preparation process of the invention is simple, has low energy consumption, and the operating process conditions are easy to control and easy to realize industrial production, and is a lemon extraction method with great application prospects; the method can prepare lemon essential oil, limonin and lemon pectin in the same process flow, thereby achieving full utilization of resources.

[0024] According to some embodiments of the present invention, the lemon peel is obtained by peeling lemons.

[0025] According to some embodiments of the present invention, the lemon pulp is obtained by peeling fresh lemons.

[0026] According to some embodiments of the present invention, the lemon extract is at least one of lemon essential oil, lemon pectin and limonin.

[0027] According to some embodiments of the present invention, cellulase is used for the enzymatic hydrolysis.

[0028] According to some embodiments of the present invention, the pH of the enzymatic hydrolysis is 4.5-5.5.

[0029] According to some embodiments of the present invention, the temperature of the enzymatic hydrolysis is 40°C to 50°C.

[0030] According to some embodiments of the present invention, the mass ratio of the added amount of the enzyme to the lemon peel is 0.8-1.1:100.

[0031] According to some embodiments of the present invention, the liquid-to-solid ratio is 10-15:1.

[0032] The liquid-to-solid ratio refers to the volume-to-mass ratio of water to lemon peel.

[0033] According to some embodiments of the present invention, the mass volume ratio of the lemon peel to water is 1 g: 10 mL to 15 mL.

[0034] According to some embodiments of the present invention, the enzymatic hydrolysis time is 45 min to 70 min.

[0035] According to some embodiments of the present invention, the steam distillation time is 70 min to 140 min.

[0036] Steam distillation is used to separate components such as pectin and cellulose from lemon peel.

[0037] According to some embodiments of the present invention, the pH of the first liquid phase in step S12 needs to be adjusted to 1-2.

[0038] According to some embodiments of the present invention, the mass ratio of the cationic resin to the lemon peel is 0.1 to 0.15:1.

[0039] According to some embodiments of the present invention, the cationic resin is at least one of a 732 type cationic resin and a C100 type cationic resin.

[0040] According to some embodiments of the present invention, the treatment temperature in step S12 is 70°C to 80°C.

[0041] According to some embodiments of the present invention, the processing time in step S12 is 1 hour to 1.5 hours.

[0042] According to some embodiments of the present invention, activated carbon is used for decolorization in step S13.

[0043] According to some embodiments of the present invention, the mass ratio of the activated carbon to the second liquid phase is 0.5 to 1:100.

[0044] According to some embodiments of the present invention, the decolorization time in step S13 is 1 h to 1.5 h.

[0045] According to some embodiments of the present invention, the volume fraction of the ethanol aqueous solution in step S14 is 80% to 95%.

[0046] According to some embodiments of the present invention, the molecular weight cut-off of the ultrafiltration in step S13 is 10,000 Daltons.

[0047] According to some embodiments of the present invention, the ultrafiltration pressure in step S13 is 0.3 MPa to 0.4 MPa.

[0048] According to some embodiments of the present invention, in step S14, the ultrafiltrate and the ethanol aqueous solution are mixed and then stirred.

[0049] According to some embodiments of the present invention, the stirring time is 1 h to 1.5 h.

[0050] According to some embodiments of the present invention, a gel is formed after the stirring.

[0051] According to some embodiments of the present invention, the pressure of the filter pressing in step S14 is 0.1 MPa to 0.5 MPa.

[0052] According to some embodiments of the present invention, the distillation temperature in step S14 is 65°C to 75°C.

[0053] According to some embodiments of the present invention, the drying in step S14 is spray drying.

[0054] According to some embodiments of the present invention, the inlet air temperature of the spray drying is 180°C to 190°C.

[0055] According to some embodiments of the present invention, the outlet air temperature of the spray drying is 80°C to 90°C.

[0056] According to some embodiments of the present invention, the extraction is followed by standing at 0°C to 5°C.

[0057] According to some embodiments of the present invention, the standing time is 3 h to 5 h.

[0058] According to some embodiments of the present invention, the freeze-drying temperature in step S21 is -10°C to -40°C.

[0059] According to some embodiments of the present invention, the organic solvent in step S22 is ethyl acetate.

[0060] According to some embodiments of the present invention, in step S2, the lemon pulp is crushed by a juicer and then filtered by gauze to obtain a filtered precipitate and a liquid;

[0061] The liquid is then centrifuged to obtain a centrifugal precipitate;

[0062] The pellet after centrifugation was combined with the pellet after filtration. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] In order to facilitate understanding by those skilled in the art, the present invention is further described below with reference to the accompanying drawings.

[0064] Figure 1 The present invention is a flow chart of the preparation of lemon extract according to an embodiment of the present invention. DETAILED DESCRIPTION

[0065] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0066] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0067] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased from the market.

[0068] The detection method of limonin glycosides is as follows:

[0069] High performance liquid chromatography: Agilent 1260 chromatograph was used, a 250 mm × 4.6 mm column was selected, and the detection wavelength was set to 210 nm.

[0070] A (3 mM phosphoric acid) and B (acetonitrile) were used as mobile phases with a flow rate of 1 mL / min.

[0071] Gradient elution, the elution gradient is as follows:

[0072] From 0min to 7min, the volume fraction of A changes from 85% to 79%;

[0073] From 7 to 8 minutes, the volume fraction of A remains at 79%;

[0074] From 8 to 16 minutes, the volume fraction of A changes from 79% to 70%;

[0075] From 16min to 25min, the volume fraction of A changes from 70% to 65%.

[0076] Take an appropriate amount of limonin glycoside reference substance, weigh it accurately, and add methanol to make a solution containing 0.1 mg per 1 mL as the reference substance. Take 5 mg of this product, weigh it accurately, and place it in a 10 mL volumetric bottle;

[0077] Dissolve in methanol and dilute to scale, shake well. Accurately measure 5mL, place in a 25mL volumetric flask, add methanol and dilute to scale as the test sample. Accurately pipette 10μL of the reference solution and the test solution respectively, inject into the liquid chromatograph, and measure to obtain.

[0078] Example 1

[0079] This embodiment is a method for preparing a lemon extract. Figure 1 As shown, it consists of the following steps:

[0080] S1. Raw material pretreatment: 5 kg of lemons are put into a fruit peeler to peel and collect the lemon peels; the peeled fresh lemons are crushed and the solid phase and the liquid phase are separated to obtain clarified lemon juice and lemon pulp;

[0081] S2, essential oil extraction: lemon peel was enzymatically hydrolyzed (enzymatic hydrolysis temperature 45 ° C, enzymatic hydrolysis pH 5, enzyme addition amount 1%, the mass ratio of added enzyme to lemon peel was 1:100, the added cellulase was Xiasheng FFG-0666, the liquid-to-solid ratio (i.e., the volume mass ratio of water to lemon peel) was 15 mL: 1 g, and the enzymatic hydrolysis time was 50 min), and the lemon essential oil was extracted by steam distillation, and the steam distillation time was 70 min;

[0082] S3, limonin pretreatment: freeze-drying the lemon solid phase (lemon pulp) obtained in step S1 at a freeze-drying temperature range of -10°C to -40°C, and crushing into powder;

[0083] S4, extraction and purification of limonin: Combine the powder obtained in S3 and the lemon liquid in S1, stir and extract with 5 times the amount of ethyl acetate, let stand at low temperature and collect the ethyl acetate layer after stratification, the low temperature standing temperature is 0℃ to 5℃, and the time is 4h. Remove the solvent from the ethyl acetate layer until there is no solvent smell, and concentrate and dry to obtain powder;

[0084] S5, pectin extraction and decolorization: After the essential oil is extracted from the lemon peel, add 3 times the weight of the lemon peel to the remaining phase of the steam distillation, mix and homogenize, centrifuge, and take the supernatant;

[0085] The supernatant was taken and adjusted to pH 1.5, and a cation exchange resin was added for stirring extraction. The cation exchange resin was C100, and the mass ratio of the resin to the lemon peel was 10:100. The cation exchange resin was stirred for extraction for 1 hour at a temperature of 75°C. The solid-liquid separation was performed, and the liquid phase was collected to obtain an extract.

[0086] Activated carbon (the amount of activated carbon is 0.5% of the extract) is added to the extract for 1 hour. After the decolorized solution is ultrafiltered, the ultrafiltration step is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa to 0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0087] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. Press filter (the pressure of the press filter is 0.25 MPa) to obtain a filtrate. Distill the filtrate (the temperature is 65°C), spray dry the gelled product obtained by distillation, control the inlet air temperature to 187°C, and the outlet air temperature to 83°C to prepare a dry pectin product, which is crushed and passed through an 80-mesh sieve to obtain a finished pectin powder.

[0088] The extraction rate of the dry pectin in this embodiment is 36.9%.

[0089] The essential oil extraction rate in this embodiment is 2.35%.

[0090] In this example, the extraction rate of limonin was 80.19% and the purity was 90.71%.

[0091] Example 2

[0092] This embodiment is a method for preparing a lemon extract, which consists of the following steps:

[0093] S1. Raw material pretreatment: 5 kg of lemons are put into a fruit peeler to peel and collect the lemon peels; the peeled fresh lemons are crushed and the solid phase and the liquid phase are separated to obtain clarified lemon juice and lemon pulp;

[0094] S2, essential oil extraction: lemon peel was enzymatically hydrolyzed (enzymatic hydrolysis temperature 45 ° C, enzymatic hydrolysis pH 5, enzyme addition amount 0.8%, enzyme to lemon peel mass ratio 0.8:100, the added cellulase was Xiasheng FFG-0666, liquid-to-solid ratio (i.e., volume mass ratio of water to lemon peel) 15mL:1g, enzymatic hydrolysis time 50min), and lemon essential oil was extracted by steam distillation, and the steam distillation time was 70min;

[0095] S3, limonin pretreatment: freeze-drying the lemon solid phase (lemon pulp) obtained in step S1 at a freeze-drying temperature range of -10 to -40°C, and crushing into powder;

[0096] S4, extraction and purification of limonin: combine the powder obtained in S3 and the lemon liquid in S1, stir and extract with 5 times the amount of ethyl acetate, let stand at low temperature for stratification, collect the ethyl acetate layer, let stand at low temperature for 4 hours at a temperature of 0°C to 5°C, remove the solvent from the ethyl acetate layer until there is no solvent smell, and concentrate and dry to obtain powder;

[0097] S5, pectin extraction and decolorization: After the essential oil is extracted from the lemon peel, add 3 times the weight of lemon peel water to the remaining phase of steam distillation, mix and homogenize, centrifuge, and take the supernatant;

[0098] The supernatant was taken and adjusted to pH 1.5, and a cation exchange resin was added for stirring extraction. The cation exchange resin was 732, and the mass ratio of the resin to the lemon peel was 10:100. The cation exchange resin was stirred for extraction for 1 hour at a temperature of 80°C. The solid-liquid separation was performed, and the liquid phase was collected to obtain an extract.

[0099] Activated carbon (the amount of activated carbon is 0.5% of the extract) is added to the extract for 1 hour, and the decolorized solution is ultrafiltered. The ultrafiltration is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa-0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0100] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. After filter pressing (the pressure of filter pressing is 0.25 MPa), distillation (temperature is 70°C) is performed. The gelled product obtained after distillation is spray-dried. The inlet air temperature is controlled at 187°C and the outlet air temperature is controlled at 83°C to prepare a pectin dry product. The pectin powder product is obtained by crushing and passing through an 80-mesh sieve.

[0101] The extraction rate of the dry pectin in this example is 37.1%.

[0102] The essential oil extraction rate in this embodiment is 2.23%.

[0103] In this example, the extraction rate of limonin was 80.27% and the purity was 90.15%.

[0104] Example 3

[0105] This embodiment is a method for preparing a lemon extract, which consists of the following steps:

[0106] S1. Raw material pretreatment: 10 kg of lemons are put into a fruit peeler to peel and collect the lemon peels; the peeled fresh lemons are crushed and the solid phase and the liquid phase are separated to obtain clarified lemon juice and lemon pulp;

[0107] S2, essential oil extraction: lemon peel was enzymatically hydrolyzed (enzymatic hydrolysis temperature 50 ° C, enzymatic hydrolysis pH 5, enzyme addition amount 0.8%, enzyme to lemon peel mass ratio of 0.8:100, the added cellulase is Xiasheng FFG-0666, liquid-to-solid ratio (i.e., volume mass ratio of water to lemon peel) 15mL:1g, enzymatic hydrolysis time 60min), and lemon essential oil was extracted by steam distillation, and the steam distillation time was 70min;

[0108] S3, limonin pretreatment: freeze-drying the lemon solid phase (lemon pulp) obtained in step S1 at a freeze-drying temperature range of -10 to -40°C, and crushing into powder;

[0109] S4, extraction and purification of limonin: combine the powder obtained in S3 and the lemon liquid in S1, stir and extract with 5 times the amount of ethyl acetate, let stand at low temperature for stratification, collect the ethyl acetate layer, let stand at low temperature for 4 hours at a temperature of 0°C to 5°C, remove the solvent from the ethyl acetate layer until there is no solvent smell, and concentrate and dry to obtain powder;

[0110] S5, pectin extraction and decolorization: After the essential oil is extracted from the lemon peel, add 3 times the weight of lemon peel water to the remaining phase of steam distillation, mix and homogenize, centrifuge, and take the supernatant;

[0111] The supernatant was adjusted to pH 2, and a cation exchange resin was added for stirring extraction. The cation exchange resin was 732, and the mass ratio of the resin to the lemon peel was 10:100. The cation exchange resin was stirred for extraction for 12 h at a temperature of 75°C. The solid-liquid separation was performed, and the liquid phase was collected to obtain an extract.

[0112] Activated carbon (the amount of activated carbon is 1% of the extract) is added to the extract for 1 hour, and the decolorized solution is ultrafiltered. The ultrafiltration is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa-0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0113] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. After filter pressing (the pressure of filter pressing is 0.25 MPa), distillation (temperature is 70°C) is performed. The gelled product obtained after distillation is spray-dried. The inlet air temperature is controlled at 187°C and the outlet air temperature is controlled at 83°C to prepare a dry pectin product, which is then crushed and passed through an 80-mesh sieve to obtain a finished pectin powder.

[0114] The extraction rate of the dry pectin in this embodiment is 37.4%.

[0115] The essential oil extraction rate in this embodiment is 2.25%.

[0116] In this example, the extraction rate of limonin was 80.33% and the purity was 90.77%.

[0117] Example 4

[0118] This embodiment is a method for preparing a lemon extract, which consists of the following steps:

[0119] S1. Raw material pretreatment: 10 kg of lemons are put into a fruit peeler to peel and collect the lemon peels; the peeled fresh lemons are crushed and the solid phase and the liquid phase are separated to obtain clarified lemon juice and lemon pulp;

[0120] S2, essential oil extraction: lemon peel was enzymatically hydrolyzed (enzymatic hydrolysis temperature 45 ° C, enzymatic hydrolysis pH 5, enzyme addition amount 1%, the mass ratio of enzyme to lemon peel was 1:100, the added cellulase was Xiasheng FFG-0666, the liquid-to-solid ratio (i.e., the volume mass ratio of water to lemon peel) was 15 mL: 1 g, and the enzymatic hydrolysis time was 60 min), and the lemon essential oil was extracted by steam distillation, and the steam distillation time was 70 min;

[0121] S3, limonin pretreatment: freeze-drying the lemon solid phase (lemon pulp) obtained in step S1 at a freeze-drying temperature range of -10 to -40°C, and crushing into powder;

[0122] S4, extraction and purification of limonin: combine the powder obtained in S3 and the lemon liquid in S1, stir and extract with 5 times the amount of ethyl acetate, let stand at low temperature for stratification, collect the ethyl acetate layer, let stand at low temperature for 4 hours at a temperature of 0°C to 5°C, remove the solvent from the ethyl acetate layer until there is no solvent smell, and concentrate and dry to obtain powder;

[0123] S5, pectin extraction and decolorization: After the essential oil is extracted from the lemon peel, add 3 times the weight of lemon peel water to the remaining phase of steam distillation, mix and homogenize, centrifuge, and take the supernatant;

[0124] The supernatant was taken and adjusted to pH 2, and a cation exchange resin was added for stirring extraction, the cation exchange resin was C100, the mass ratio of the resin to the lemon peel was 10:100, the cation exchange resin was stirred for extraction for 1.3 h, the temperature was 78°C, the solid-liquid separation was performed, and the liquid phase was collected to obtain an extract;

[0125] Activated carbon (the amount of activated carbon is 1% of the extract) is added to the extract for 1 hour, and the decolorized solution is ultrafiltered. The ultrafiltration is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa-0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0126] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. After filter pressing (the pressure of filter pressing is 0.25 MPa), distillation (temperature is 75°C) is performed. The gelled product obtained by distillation is spray-dried. The inlet air temperature is controlled at 187°C and the outlet air temperature is controlled at 83°C to prepare a dry pectin product, which is then crushed and passed through an 80-mesh sieve to obtain a finished pectin powder.

[0127] The extraction rate of the dry pectin in this embodiment is 36.7%.

[0128] The essential oil extraction rate in this embodiment is 2.34%.

[0129] In this example, the extraction rate of limonin was 80.26% and the purity was 90.65%.

[0130] Comparative Example 1

[0131] This comparative example is a method for preparing a lemon extract, which differs from Example 1 in that the enzymatic hydrolysis operation before steam distillation is removed, that is, the process parameters of step S2 in this comparative example are as follows:

[0132] S2. Essential oil extraction: extract lemon essential oil by steam distillation of lemon peel (liquid-to-solid ratio (i.e., volume-to-mass ratio of water to lemon peel) 15 mL: 1 g, steam distillation time 70 min).

[0133] The extraction rate of lemon essential oil in this comparative example is 1.78%.

[0134] Comparative Example 2

[0135] This comparative example is a method for preparing a lemon extract, which differs from Example 1 in that the pH of the supernatant in step S5 of this comparative example is not adjusted, that is, the process parameters of step S5 of this comparative example are as follows:

[0136] S5, pectin extraction and decolorization: After the essential oil is extracted from the lemon peel, add 3 times the weight of lemon peel water to the remaining phase of steam distillation, mix and homogenize, centrifuge, and take the supernatant;

[0137] The supernatant was added with a cation exchange resin for stirring extraction, the cation exchange resin was C100, the mass ratio of the resin to the lemon peel was 10:100, the cation exchange resin was stirred for extraction for 1 hour, the temperature was 70-80°C, the solid-liquid separation was performed, the liquid phase was collected, and an extract was obtained;

[0138] Activated carbon (the amount of activated carbon is 1% of the extract) is added to the extract for 1 hour, and the decolorized solution is ultrafiltered. The ultrafiltration is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa-0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0139] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. Press filter (the pressure of the press filter is 0.25MPa) and distill at a temperature of 65°C-75°C to recover the ethanol. The obtained gel is spray-dried with the inlet air temperature controlled at 187°C and the outlet air temperature controlled at 83°C to prepare a dry pectin product, which is then crushed and passed through an 80-mesh sieve to obtain a finished pectin powder.

[0140] The pectin extraction rate in this comparative example is 32.21%.

[0141] Comparative Example 3

[0142] This comparative example is a method for preparing a lemon extract, which differs from Example 1 in that: in step S5 of this comparative example, pectin is extracted by microwave method, that is, the process parameters of step S5 of this comparative example are as follows:

[0143] S5. Pectin extraction and decolorization: put the lemon peel residue into water 3 times the weight of the tare, adjust the pH to 2, and extract the pectin by microwave method, the microwave power is 700 W, and the microwave extraction time is 5 min;

[0144] Activated carbon (the amount of activated carbon is 1% of the extract) is added to the extract for 1 hour, and the decolorized liquid is ultrafiltered. The ultrafiltration is to remove the waste residue by cross-flow filtration at a pressure of 0.03MPa-0.04MPa in a roll-type ultrafiltration device capable of retaining substances with a molecular weight of more than 10,000 Daltons to obtain an ultrafiltrate;

[0145] Add 90% ethanol by volume to the ultrafiltrate and stir for 1 hour to form a gel. After filter pressing (the pressure of filter pressing is 0.25 MPa), distillation (temperature is 65°C) is performed. The gelled product obtained by distillation is spray-dried. The inlet air temperature is controlled at 187°C and the outlet air temperature is controlled at 83°C to prepare a dry pectin product, which is then crushed and passed through an 80-mesh sieve to obtain a finished pectin powder.

[0146] The pectin extraction rate in this comparative example is 22.67%.

[0147] Comparative Example 4

[0148] This comparative example is a method for preparing a lemon extract, which differs from Example 1 in that: in step S3 of this comparative example, the lemon solid phase is not freeze-dried, but is dried at high temperature to prepare a powder, that is, the process parameters of step S3 of this comparative example are as follows:

[0149] S3, limonin pretreatment: drying the lemon solid phase (lemon pulp) obtained in step S1 at a drying temperature of 80° C. and crushing into powder;

[0150] The extraction rate of limonin in this comparative example is 65.84% and the purity is 75.21%.

[0151] In summary, the present invention adopts enzyme-assisted steam distillation essential oil extraction, low-temperature extraction of limonin, and acid-method resin extraction of lemon pectin, and can prepare lemon essential oil, limonin and lemon pectin in the same process flow, and the resource utilization is sufficient; the process of extracting lemon essential oil by enzyme-assisted steam distillation is based on the characteristics of plant raw material cell wall composition, and the high specificity of enzyme reaction is utilized to select corresponding enzymes to degrade the components of cell wall before steam distillation extraction, so that the effective components bound in the cell are dissolved, thereby achieving the purpose of rapid extraction; acid method and resin are used to extract pectin, and the extraction rate is significantly improved. The overall preparation process is simple, energy consumption is low, the operating process conditions are easy to control, and it is easy to realize industrial production. It is a lemon extraction method with great application prospects.

[0152] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a lemon extract, characterized in that: The following steps are involved: S1, enzymatically hydrolyzing lemon peel and then steam distilling to obtain lemon essential oil and extract residue; S11, mixing the extraction residue and water, separating the solid and the liquid, and collecting the first liquid phase; S12, treating the first liquid phase with a cation exchange resin to obtain a second liquid phase; S13, decolorizing and ultrafiltering the second liquid phase to obtain an ultrafiltrate; S14, mixing the ultrafiltrate and ethanol aqueous solution, performing filter pressing, distillation, and drying to obtain pectin; S2, crushing the lemon pulp to obtain lemon juice and lemon pulp; S21, freeze-drying the lemon pulp to obtain powder; S22, mixing the powder, lemon juice and an organic solvent and extracting to obtain an organic phase; S23, concentrating and drying the organic phase to obtain limonin; The enzymatic hydrolysis uses cellulase; The temperature of the enzymatic hydrolysis is 40°C to 50°C; The order of step S1 and step S2 is not important; In step S12, the pH of the first liquid phase needs to be adjusted to 1-2; The pH of the enzymatic hydrolysis is 4.5-5.5; The cationic resin is at least one of a 732 type cationic resin and a C100 type cationic resin; The treatment temperature in step S12 is 70°C to 80°C; The volume fraction of the ethanol aqueous solution in step S14 is 80% to 95%; The organic solvent in step S22 is ethyl acetate.

2. The method for preparing the lemon extract according to claim 1, characterized in that: In step S13, activated carbon is used for decolorization.

3. The method for preparing the lemon extract according to claim 1, characterized in that: The pressure of the filter press in step S14 is 0.1 MPa~0.5 MPa.

4. The method for preparing the lemon extract according to claim 1, characterized in that: After the extraction, the mixture is allowed to stand at 0°C to 5°C.

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