Bergamot waste residue pectin recovery method and product thereof

Abstract

The invention discloses a bergamot waste residue pectin recovery method and a product thereof, and the method comprises the following steps: taking fresh bergamot waste residue, freeze-drying, and crushing; adding into a surfactant-organic acid solution, and uniformly stirring; performing ultrasonic treatment; performing constant-temperature water bath extraction; adding distilled water for diluting and uniformly stirring, centrifuging and collecting supernate, and concentrating the supernate in a rotary evaporator under the conditions of reduced pressure and low temperature, so as to obtain concentrated pectin leach liquor of the bergamot waste residues; and adding ethanol into the concentrated pectin extract liquid of the bergamot waste residues in a stirring state, fully stirring, sealing, standing in a low-temperature environment, and centrifugally collecting precipitates to obtain wet pectin of the bergamot waste residues. According to the method, the pectin is recovered from the bergamot waste residues in an organic acid environment in combination with the synergistic effect of an ultrasonic cell crushing technology and a surfactant for the first time, so that the pectin recovery efficiency is remarkably improved; and the process is green and safe and has good application prospects.

Description

Technical Field

[0001] The invention relates to the technical field of pectin recovery, in particular to a method for recovering pectin from bergamot waste residues and a product thereof, and in particular to an efficient and green method for recovering pectin from bergamot waste residues and pectin recovered by the method. Background Art

[0002] Pectin is an anionic acidic macromolecular heteropolysaccharide composed of D-galacturonic acid residues and some heteropolysaccharides linked by more than 100 α-(1-4) glycosidic bonds, and exists in all higher plants. Pectin is mainly covalently bound to cellulose, hemicellulose, lignin, etc. to form protopectin, which is a structural substance of plants and plays a vital role in maintaining the structure and hardness of plants. Pectin can be used as a natural additive in the food and medical industries. The FAO / WHO Joint Committee on Food Additives has recognized pectin as a safe and non-toxic natural food additive, and there is no need to limit the daily intake.

[0003] Bergamot (Citrus medica var. sarcodactylis), also known as Buddha's hand fruit, is an evergreen small tree of the Rutaceae family. It is named for its finger-like fruit shape. It is mainly distributed in Guangdong, Guangxi, Sichuan, Fujian and Jinhua, Zhejiang in China. Its volatile essential oil is also widely used in the food, cosmetics and pharmaceutical industries, and has a positive effect on improving depression and anti-oxidation. However, the treatment of bergamot waste residues generated during the processing process has become a key issue in improving the sustainability and economic benefits of its processing industry.

[0004] As a type of citrus, bergamot waste is rich in organic substances such as pectin. Traditional pectin extraction methods mostly use inorganic acid extraction, which is simple and mature. However, traditional extraction methods are cumbersome, time-consuming, and labor-intensive, and may involve volatile and harmful organic solvents or strong acid and alkali solutions, which are not in line with the concept of green, environmental protection, and sustainable development. In recent years, new extraction technologies have been used for pectin extraction, including microwave-assisted extraction, ultrasound-assisted extraction, subcritical water extraction, and enzyme-assisted extraction, which have become alternatives to traditional extraction methods.

[0005] Therefore, a method for recovering pectin from bergamot waste residue with convenient extraction, green process and high recovery efficiency is of great practical significance. Summary of the invention

[0006] Due to the above-mentioned defects in the prior art, the present invention provides a method for recovering pectin from bergamot waste residues, which is convenient for extraction, has a green process and high recovery efficiency. Specifically, under an organic acid environment, the method combines ultrasonic cell crushing technology with the synergistic effect of surfactants to recover pectin from bergamot waste residues, which significantly improves the efficiency of recovering pectin from bergamot waste residues. At the same time, degradable solvents are used to reduce the use of inorganic reagents, thereby ensuring the safety, greenness, environmental protection and sustainable development of the recovery process, and overcoming the defects of cumbersome operation and environmentally unfriendly process of traditional extraction processes.

[0007] In order to achieve the above object, the present invention provides the following technical solutions:

[0008] A method for recovering pectin from bergamot waste residue comprises the following steps:

[0009] (1) taking fresh bergamot waste residue, freeze-drying and crushing to obtain bergamot waste residue powder;

[0010] (2) adding the bergamot waste residue powder into the surfactant-organic acid solution and stirring evenly;

[0011] (3) subjecting the mixture obtained in step (2) to ultrasonic treatment;

[0012] (4) extracting the mixture obtained in step (3) in a constant temperature water bath;

[0013] (5) adding distilled water to the mixture obtained in step (4) to dilute and stir evenly, collecting the supernatant by centrifugation, and concentrating the supernatant in a rotary evaporator under reduced pressure and low temperature conditions to obtain a concentrated pectin extract from bergamot waste residue;

[0014] (6) Add ethanol to the concentrated pectin extract from the bergamot waste residue obtained in step (5) under stirring, and stir thoroughly to allow pectin to precipitate. The mixture is sealed and allowed to stand at low temperature, and the precipitate is collected by centrifugation to obtain wet pectin from the bergamot waste residue.

[0015] The method for recovering pectin from bergamot waste residues of the present invention recovers pectin from bergamot waste residues in an organic acid environment by combining ultrasonic cell pulverization technology with the synergistic effect of a surfactant. The surfactant is an effective auxiliary agent for extracting bioactive compounds (for example, polysaccharides and flavonoids). When the concentration of the surfactant is equal to or higher than the critical micelle concentration of the surfactant, the composite system will form micelles, and these micelles can establish chemical and physical interactions with hydrophilic or lipophilic substances, thereby promoting the transfer of target compounds from the medium. Since pectin has different chemical structures within a wide range of polarities, a suitable surfactant can be used for auxiliary extraction. At the same time, the ultrasonic cell pulverization technology and the synergistic effect of the surfactant can be used to fully recover the pectin in the bergamot waste residues, which significantly improves the efficiency of recovering pectin from the bergamot waste residues. The solvents used in the process are all degradable. Compared with the traditional process, the use of inorganic reagents is greatly reduced, ensuring the safety, greenness, environmental protection and sustainable development of the recovery process, overcoming the defects of the traditional extraction process of cumbersome operation and non-environmental process, and having good application prospects.

[0016] As the preferred technical solution:

[0017] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (1), the crushing refers to crushing the freeze-dried fresh bergamot waste residue to a size of 40 mesh or more;

[0018] The bergamot waste residue is derived from squeezing, steam distillation, supercritical CO 2 The pomace obtained during the extraction of bergamot essential oil by fluid extraction, solvent extraction, etc.

[0019] In the method for recovering pectin from bergamot waste residue as described above, in step (2), the solid-liquid ratio of the bergamot waste residue powder to the surfactant-organic acid solution is 1:20-1:60 g / mL, the concentration of the surfactant in the surfactant-organic acid solution is 2-10 g / L, the surfactant is Tween 20 (TW20), polyethylene glycol 400 (PEG400), saponin (SAP), sodium α-olefin sulfonate (AOS) or cetyltrimethylammonium chloride (CTAC), etc., and the organic acid refers to citric acid, tartaric acid, acetic acid or lactic acid solution with a pH of 2.0 obtained by titration with 1 mol / L sodium hydroxide solution.

[0020] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (3), the ultrasonic treatment is performed in an ultrasonic cell pulverizer;

[0021] The power of the ultrasonic cell pulverizer is 100~500W, the ultrasonic time is 10~18min, and the ultrasonic on and off time is 1s.

[0022] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (4), the extraction temperature is 60-95° C., and the extraction time is 40-120 min.

[0023] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (5), the centrifugal speed is 8000-10000 r / min, and the centrifugal time is 10-15 min.

[0024] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (6), the ethanol is an ethanol aqueous solution with a volume percentage of 60-95%, the volume of the ethanol is three times that of the concentrated pectin extract from bergamot waste residue, the low temperature environment is 0-4°C, and the standing time is 12-24h.

[0025] The above-mentioned method for recovering pectin from bergamot waste residues further comprises:

[0026] (7) The bergamot waste pectin is washed with ethanol and then dried to a constant weight to obtain the bergamot waste pectin.

[0027] In the above-mentioned method for recovering pectin from bergamot waste residue, in step (7), the ethanol is an ethanol aqueous solution with a volume percentage of 60%, the washing is performed no less than 3 times, and the drying refers to freeze drying or drying at 40°C.

[0028] In addition, the present invention also provides pectin recovered by the method for recovering pectin from bergamot waste residue as described above, wherein the pectin is wet pectin, pectin extract or dry pectin.

[0029] The above technical solution is only a feasible technical solution of the present invention, and the protection scope of the present invention is not limited thereto. Those skilled in the art can reasonably adjust the specific design according to actual needs.

[0030] The above invention has the following advantages or beneficial effects:

[0031] (1) The method for recovering pectin from bergamot waste residue of the present invention is the first in the field of bergamot pectin recovery to propose a method for recovering pectin in a synergistic manner by combining ultrasonic cell crushing technology with surfactants under an organic acid environment, which can achieve full recovery of pectin in bergamot waste residue; it significantly improves the efficiency of recovering pectin from bergamot waste residue, and the solvents used in the process are all degradable. Compared with the traditional process, the use of inorganic reagents is greatly reduced, ensuring the safety, greenness, environmental protection and sustainable development of the recovery process, and overcoming the defects of the traditional extraction process that is cumbersome to operate and not environmentally friendly.

[0032] (2) The method for recovering pectin from bergamot waste residue of the present invention has a simple process, a high pectin recovery rate, safe and readily available raw materials, an environmentally friendly process, and good application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The present invention and its features, appearance and advantages will become more apparent by reading the detailed description of non-limiting embodiments with reference to the following drawings. The same reference numerals indicate the same parts in all the drawings. The drawings are not drawn to scale, and emphasis is placed on illustrating the subject matter of the present invention.

[0034] Figure 1 is the standard curve of galacturonic acid;

[0035] Figure 2 The process flow chart of the method for recovering pectin from bergamot waste residue of the present invention is as follows;

[0036] Figure 3 This is a comparison chart of the recovery rates of pectin from bergamot waste residue in Examples 1 to 5;

[0037] Figure 4 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Comparative Examples 1 to 4;

[0038] Figure 5 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Examples 4, 6 to 9;

[0039] Figure 6 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Examples 4, 10 to 13;

[0040] Figure 7 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Examples 4, 14 to 17;

[0041] Figure 8 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Examples 4, 18 to 21;

[0042] Fig. 9 This is a comparison chart of the recovery rates of pectin from bergamot waste residues in Examples 4, 22 to 25;

[0043] Fig.10 This is a comparison chart of the pectin recovery rates from bergamot waste residues in Examples 4, 26 to 29. DETAILED DESCRIPTION

[0044] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0045] The determination methods of pectin content and calculation methods of pectin yield involved in the following examples and comparative examples are as follows:

[0046] 1) Measurement principle

[0047] Pectin content determination method: refer to the Agricultural Industry Standard of the People's Republic of China NY / T2016-2011 "Determination of Pectin Content in Fruits and Their Products (Spectrophotometry)". Using D-galacturonic acid as the standard, the pectin content was determined by carbazole-colorimetry. Pectin is hydrolyzed to generate galacturonic acid, which forms a stable purple-red complex with carbazole in a concentrated sulfuric acid medium. A standard curve of absorbance A and galacturonic acid concentration is established at the maximum absorption wavelength of 525nm, and the standard curve equation is obtained, so as to calculate the pectin content in the sample according to the equation.

[0048] 2) Preparation of galacturonic acid standard curve Accurately pipette 0, 1, 2, 3, 4, 5 mL of the standard stock solution, dilute to a 50 mL volumetric flask with distilled water, and prepare standard solutions with concentration gradients of 0, 20, 40, 60, 80, and 100 mg / L. Pipette 1 mL of each standard solution of different concentrations into a 25 mL glass test tube, add 0.25 mL of 1 g / L carbazole-ethanol solution to produce a white flocculent precipitate, shake the test tube continuously, and then quickly add 5.0 mL of concentrated sulfuric acid and shake well. Immediately place the test tube in an 85°C water bath oscillator for 20 minutes, take it out and quickly cool it in cold water. Within 1.5 hours, use an ultraviolet spectrophotometer to measure the absorbance of the standard solution at a wavelength of 525 nm, and draw a standard curve with the galacturonic acid concentration as the horizontal axis (X) and the absorbance value as the vertical axis (Y). The galacturonic acid standard curve is obtained (as shown in the figure). Figure 1 As shown), and the linear regression equation is y=0.01093x+0.0053(R²=0.9997).

[0049] 3) Determination of pectin content of samples

[0050] Take the supernatant after centrifugation during separation and concentration, dilute it to a certain concentration, take 1mL of the dilution into a 25mL glass test tube, add 0.25mL of carbazole-ethanol solution, and develop the color with the standard solution color development method. Within 1.5 hours, use a spectrophotometer to measure its absorbance at a wavelength of 525nm, and calculate the pectin content in the pectin extract according to the standard curve, in terms of galacturonic acid. Perform a blank test at the same time as the above method, and use the blank to adjust to zero.

[0051] (1)

[0052] In formula (1):

[0053] P: Pectin content in the sample (calculated as galacturonic acid)

[0054] C: Galacturonic acid concentration calculated according to the standard curve (mg / L)

[0055] N: dilution factor of pectin extract

[0056] V: Total volume of pectin extract (mL)

[0057] M: sample weight (g).

[0058] Example 1

[0059] A method for recovering pectin from bergamot waste residues, comprising the following steps (eg Figure 2 shown):

[0060] 1) Raw material processing: Take fresh bergamot waste residue, remove moisture by freeze drying, crush and pass through a 40-mesh sieve to obtain dry powder;

[0061] 2) Mixing of feed and liquid: Use Tween 20 (TW20) at a concentration of 4 g / L and citric acid with a pH of 2.0 (obtained by titration with 1 mol / L sodium hydroxide solution) to prepare a surfactant-organic acid solution as a solvent, mix at a feed-liquid ratio of 1:30 g / mL, and stir evenly;

[0062] 3) Ultrasonic disruption: Place the mixture obtained in step 2) in an ultrasonic cell disruptor, turn on and off the ultrasound for 1 second, power 200 W, and ultrasound for 14 minutes;

[0063] 4) Hot water extraction: The mixture obtained in step 3) was extracted in a constant temperature water bath at 80°C for 60 minutes;

[0064] 5) separation and concentration: adding an appropriate amount of distilled water to dilute the mixture obtained in step 4) and stirring evenly, centrifuging at a speed of 10000 r / min for 15 min, collecting the supernatant, and concentrating the supernatant in a rotary evaporator under reduced pressure and low temperature conditions to obtain a concentrated pectin extract of bergamot waste residue;

[0065] 6) Alcohol precipitation purification: add three times the volume of 95% ethanol to the concentrated pectin extract obtained in step 5) under rapid stirring, and stir thoroughly to precipitate the pectin, seal, and stand at 3°C ​​for 12 hours, and collect the precipitate by centrifugation to obtain bergamot waste residue wet pectin;

[0066] 7) Washing and drying: The pectin obtained in step 6) is washed three times with 60% ethanol, and dried at 40° C. to a constant weight to obtain pectin, which is then weighed.

[0067] Example 2

[0068] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 1, except that Tween 20 (TW20) is replaced by polyethylene glycol 400 (PEG400).

[0069] Example 3

[0070] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 1, except that Tween 20 (TW20) is replaced by saponin (SAP).

[0071] Example 4

[0072] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 1, except that Tween 20 (TW20) is replaced by sodium α-olefin sulfonate (AOS).

[0073] Example 5

[0074] A method for recovering pectin from bergamot waste residue is basically the same as Example 1, except that Tween 20 (TW20) is replaced by cetyltrimethylammonium chloride (CTAC).

[0075] The recovery rates of pectin from bergamot waste residues in Examples 1 to 5 are shown in Table 1 and Figure 3 As shown;

[0076] Table 1

[0077]

[0078] From the above comparison results, it can be seen that when sodium α-olefin sulfonate is used as the surfactant compounding solvent, the recovery rate of bergamot waste pectin is the highest, that is, in comparison, sodium α-olefin sulfonate is a suitable surfactant type for recovering bergamot waste pectin.

[0079] Comparative Example 1

[0080] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 1, except that, in step 2), Tween 20 (TW20) is not added, and citric acid with a pH of 2.0 (obtained by titration with 1 mol / L sodium hydroxide solution) is directly used as a solvent.

[0081] Comparative Example 2

[0082] A method for recovering pectin from bergamot waste residue is basically the same as that of comparative example 1, except that the citric acid in step 2) is replaced by acetic acid.

[0083] Comparative Example 3

[0084] A method for recovering pectin from bergamot waste residue is basically the same as that of comparative example 1, except that the citric acid in step 2) is replaced by tartaric acid.

[0085] Comparative Example 4

[0086] A method for recovering pectin from bergamot waste residue is basically the same as that of comparative example 1, except that the citric acid in step 2) is replaced by lactic acid.

[0087] The recovery rates of pectin from bergamot waste residues in Comparative Examples 1 to 4 are shown in Table 2 and Figure 4 As shown;

[0088] Table 2

[0089]

[0090] From the above comparison results, it can be seen that when citric acid is used as the extraction solvent, the recovery rate of bergamot waste pectin is the highest, that is, in comparison, citric acid is a suitable organic acid type for recovering bergamot waste pectin.

[0091] Example 6

[0092] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction time in step 4) is 40 minutes.

[0093] Example 7

[0094] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction time in step 4) is 80 minutes.

[0095] Example 8

[0096] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction time in step 4) is 100 minutes.

[0097] Example 9

[0098] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction time in step 4) is 120 minutes.

[0099] The recovery rates of pectin from bergamot waste residues in Examples 4, 6 to 9 are shown in Table 3 and Figure 5 shown.

[0100] Table 3

[0101]

[0102] Example 10

[0103] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction temperature in step 4) is 60°C.

[0104] Embodiment 11

[0105] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction temperature in step 4) is 70°C.

[0106] Example 12

[0107] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction temperature in step 4) is 90°C.

[0108] Embodiment 13

[0109] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the extraction temperature in step 4) is 95°C.

[0110] The recovery rates of pectin from bergamot waste residues in Examples 4, 10 to 13 are shown in Table 4 and Figure 6 shown.

[0111] Table 4

[0112]

[0113] Embodiment 14

[0114] A method for recovering pectin from bergamot waste residue is basically the same as Example 4, except that the solid-liquid ratio in step 2) is 1:20 g / mL.

[0115] Embodiment 15

[0116] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the solid-liquid ratio in step 2) is 1:40 g / mL.

[0117] Example 16

[0118] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the solid-liquid ratio in step 2) is 1:50 g / mL.

[0119] Embodiment 17

[0120] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the solid-liquid ratio in step 2) is 1:60 g / mL.

[0121] The recovery rates of pectin from bergamot waste residues in Examples 4, 14 to 17 are shown in Table 5 and Figure 7 shown.

[0122] Table 5

[0123]

[0124] Embodiment 18

[0125] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic power in step 3) is 100W.

[0126] Embodiment 19

[0127] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic power in step 3) is 300W.

[0128] Embodiment 20

[0129] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic power in step 3) is 400W.

[0130] Embodiment 21

[0131] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic power in step 3) is 500W.

[0132] The recovery rates of pectin from bergamot waste residues in Examples 4, 18 to 21 are shown in Table 6 and Figure 8 shown.

[0133] Table 6

[0134]

[0135] Embodiment 22

[0136] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic time in step 3) is 10 minutes.

[0137] Embodiment 23

[0138] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic time in step 3) is 12 minutes.

[0139] Embodiment 24

[0140] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic time in step 3) is 16 minutes.

[0141] Embodiment 25

[0142] A method for recovering pectin from bergamot waste residue is basically the same as that of Example 4, except that the ultrasonic time in step 3) is 18 minutes.

[0143] The recovery rates of pectin from bergamot waste residues in Examples 4, 22 to 25 are shown in Table 7 and Fig. 9 shown.

[0144] Table 7

[0145]

[0146] Embodiment 26

[0147] A method for recovering pectin from bergamot waste residue is basically the same as Example 4, except that the concentration of sodium α-olefin sulfonate (AOS) in step 2) is 2 g / L.

[0148] Embodiment 27

[0149] A method for recovering pectin from bergamot waste residue is basically the same as Example 4, except that the concentration of sodium α-olefin sulfonate (AOS) in step 2) is 6 g / L.

[0150] Embodiment 28

[0151] A method for recovering pectin from bergamot waste residue is basically the same as Example 4, except that the concentration of sodium α-olefin sulfonate (AOS) in step 2) is 8 g / L.

[0152] Embodiment 29

[0153] A method for recovering pectin from bergamot waste residue is basically the same as Example 4, except that the concentration of sodium α-olefin sulfonate (AOS) in step 2) is 10 g / L.

[0154] The recovery rates of pectin from bergamot waste residues in Examples 4, 26 to 29 are shown in Table 8 and Fig.10 shown.

[0155] Table 8

[0156]

[0157] Application of principal component analysis to screen experimental factors and levels of pectin recovery from bergamot waste:

[0158] Principal component analysis method was used to screen the experimental factors and levels of pectin recovery from bergamot waste:

[0159] 1) The results of the pectin yield of bergamot waste residue under each single factor condition are shown in Table 9 below:

[0160] Table 9

[0161]

[0162] 2) IBM SPSS Statistics 26 software was used to perform standardized analysis on the pectin yield data of bergamot waste residue, and the standardized values ​​were obtained, as shown in Table 10 below:

[0163] Table 10

[0164]

[0165] 3) Four principal components were extracted by IBM SPSS Statistics 26 software. The first principal component accounted for 66.701%, followed by the second principal component, which accounted for 23.676%. The remaining components accounted for less than 10%, as shown in Table 11 below:

[0166] Table 11

[0167]

[0168] As can be seen from Table 12, the top three factors affecting the correlation of the pectin recovery rate of bergamot waste residue in the first principal component are: extraction time, surfactant concentration, and ultrasonic power. The greater the correlation, the greater the impact on the recovery rate of pectin from bergamot waste residue. In the second principal component, the correlation is greater between extraction temperature, ultrasonic time, and solid-liquid ratio. Since the first principal component occupies a larger proportion, the main factors in the first principal component: extraction time, surfactant concentration, and ultrasonic power are selected for response surface experiments.

[0169] Table 12

[0170]

[0171] 4) IBM SPSS Statistics 26 software was used to perform data normalization eigenvector analysis on the relevant values ​​in the component matrix, as shown in Table 13 below:

[0172] Table 13

[0173]

[0174] And build the relationship between the components and the original rate of each factor, multiply the normalized vector of each factor by the standardized rate value, and transform it into and The two indicators reflect the influence of each level on the pectin yield of bergamot waste residue, and then the principal component score is obtained, the expression is:

[0175] (2)

[0176] (3)

[0177] (4)

[0178] in, is the eigenvalue of the nth principal component, X 1 ~X 10is the value of each rate index after standardization, and F is the comprehensive evaluation index of the principal component calculated by taking the ratio of the eigenvalue corresponding to each principal component to the sum of the total eigenvalues ​​of the extracted principal components as the weight. The results are shown in Table 14 below:

[0179] Table 14

[0180]

[0181] It can be seen from Table 14 that the first and second principal components f 1 It shows a trend from rising to falling, which is the same as the trend of F score. 1 and f 2 The obtained comprehensive evaluation index F has a high score in experimental levels 2 to 4 and is consistent with f 1 and f 2 The scores of the two experiments were similar, indicating that the recovery rate of pectin from bergamot waste residue could reach the maximum value at the 2nd to 4th experimental levels. Therefore, these three levels were selected for response surface experiments.

[0182] Combined with the above experimental results, Design-Expert 13.0 software was used to take extraction time, ultrasonic power and surfactant concentration as independent variables, and the recovery rate of pectin from bergamot waste residue as the response value, and the Box-Behnken method was used to construct a three-factor three-level experimental design table, as shown in the following table; at the same time, combined with the better conditions in other single-factor experimental results: extraction temperature 80℃, ultrasonic time 14 min, solid-liquid ratio 1:40 g / mL, a response surface experiment was carried out.

[0183] Table 15

[0184]

[0185] The regression model analysis predicted by Design-Expert 13.0 software showed that the optimal process for recovering pectin from bergamot waste residue was: extraction time 60min, ultrasonic power 200W, surfactant concentration 4g / L, under which the recovery rate of bergamot waste residue pectin was 33.52%. To test the feasibility of this condition, three parallel verification experiments were carried out under this condition, and the recovery rate of pectin from bergamot waste residue was 32.18±1.42%, which was relatively small compared with the predicted value, indicating that the model had a good fit and the data had a certain reference value.

[0186] Comparative Example 5

[0187] A method for recovering pectin from bergamot waste residue is basically the same as that of comparative example 1, except that deionized water is used as solvent in step 2) and the solid-liquid ratio is 1:40 g / mL.

[0188] Comparative Example 6

[0189] A method for recovering pectin from bergamot waste residue is basically the same as Comparative Example 1, except that in step 2), hydrochloric acid with a pH of 2.0 obtained by titrating with a 1 mol / L sodium hydroxide solution is used as a solvent, and the solid-liquid ratio is 1:40 g / mL.

[0190] The pectin recovery rates of bergamot waste residues in the optimal embodiment (i.e., embodiment 15) and comparative examples 5 and 6 are shown in Table 16 below.

[0191] Table 16

[0192]

[0193] Those skilled in the art should understand that those skilled in the art can implement variations by combining the prior art and the above embodiments, which will not be described in detail here. Such variations do not affect the essential content of the present invention, and will not be described in detail here.

[0194] The above describes the preferred embodiments of the present invention. It should be understood that the present invention is not limited to the above-mentioned specific embodiments, and the devices and structures that are not described in detail should be understood to be implemented in a common manner in the art; any technician familiar with the art can use the above-disclosed methods and technical contents to make many possible changes and modifications to the technical solutions of the present invention without departing from the scope of the technical solutions of the present invention, or modify them into equivalent embodiments of equivalent changes, which does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention are still within the scope of protection of the technical solutions of the present invention.

Claims

1. A method for recovering pectin from bergamot waste residue, characterized in that: The following steps are involved: (1) taking fresh bergamot waste residue, freeze-drying and crushing to obtain bergamot waste residue powder; (2) adding the bergamot waste residue powder into the surfactant-organic acid solution and stirring evenly; (3) subjecting the mixture obtained in step (2) to ultrasonic treatment; (4) extracting the mixture obtained in step (3) in a constant temperature water bath; (5) adding distilled water to the mixture obtained in step (4) to dilute and stir evenly, collecting the supernatant by centrifugation, and concentrating the supernatant in a rotary evaporator under reduced pressure and low temperature conditions to obtain a concentrated pectin extract from bergamot waste residue; (6) Add ethanol to the concentrated pectin extract from the bergamot waste residue obtained in step (5) under stirring, and stir thoroughly to allow pectin to precipitate. The mixture is sealed and allowed to stand at low temperature, and the precipitate is collected by centrifugation to obtain wet pectin from the bergamot waste residue.

2. A method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (1), the crushing refers to crushing the freeze-dried fresh bergamot waste residue to a size of 40 mesh or more; The bergamot waste residue is the pomace obtained from the process of extracting bergamot essential oil by pressing, steam distillation, supercritical CO2 fluid extraction and solvent extraction.

3. A method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (2), the solid-liquid ratio of the bergamot waste residue powder to the surfactant-organic acid solution is 1:20~1:60 g / mL, the concentration of the surfactant in the surfactant-organic acid solution is 2~10 g / L, the surfactant is Tween 20, polyethylene glycol 400, saponin, sodium α-olefin sulfonate or hexadecyltrimethylammonium chloride, and the organic acid refers to citric acid, tartaric acid, acetic acid or lactic acid solution with a pH of 2.0 obtained by titration with 1 mol / L sodium hydroxide solution.

4. A method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (3), the ultrasonic treatment is performed in an ultrasonic cell pulverizer; The power of the ultrasonic cell pulverizer is 100~500W, the ultrasonic time is 10~18min, and the ultrasonic on and off time is 1s.

5. The method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (4), the extraction temperature is 60-95° C., and the extraction time is 40-120 min.

6. The method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (5), the centrifugal speed is 8000-10000 r / min, and the centrifugal time is 10-15 min.

7. The method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: In step (6), the ethanol is an ethanol aqueous solution with a volume percentage of 60-95%, the volume of the ethanol is three times that of the concentrated pectin extract of bergamot waste residue, the low temperature environment is 0-4°C, and the standing time is 12-24h.

8. The method for recovering pectin from bergamot waste residue according to claim 1, characterized in that: Also includes: (7) The bergamot waste pectin is washed with ethanol and then dried to a constant weight to obtain the bergamot waste pectin.

9. The method for recovering pectin from bergamot waste residue according to claim 8, characterized in that: In step (7), the ethanol is an ethanol aqueous solution with a volume percentage of 60%, the washing is performed no less than 3 times, and the drying refers to freeze drying or drying at 40°C.

10. The pectin recovered by the method for recovering pectin from bergamot waste residue according to any one of claims 1 to 9, characterized in that: The pectin is wet pectin, pectin extract or dry pectin.

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