阅读说明：本技术 一种Pickering乳液 (Pickering emulsion ) 是由 贾原媛 王影 胡春蕊 李振北 于 2021-09-17 设计创作，主要内容包括：本发明公开了一种Pickering乳液,其特征在于由阔叶木纳米纤维素悬浮液和生姜精油按体积比7:3混合后经超声乳化制成；其中,所述阔叶木纳米纤维素悬浮液的固含量为0.50～0.55wt％；所述阔叶木纳米纤维素悬浮液中的阔叶木纳米纤维素的尺寸为100～200nm。本发明制备的乳液中阔叶木纳米纤维素的氧化程度更高、尺寸更小且粒径分布更均一,乳液在显著提高生姜精油的包埋含量的同时具备更强的稳定性,乳液滴尺寸在30天储存时间内更稳定、粒径分布更均一。此外,乳液能够在较长时间内有效保留生姜精油活性成分,提高生姜精油自身抗氧化能力,使其抗菌成分和风味物质得到更好的保护。(The invention discloses a Pickering emulsion which is characterized by being prepared by mixing broadleaf wood nano cellulose suspension and ginger essential oil according to the volume ratio of 7:3 and then ultrasonically emulsifying; wherein the solid content of the hardwood nanocellulose suspension is 0.50-0.55 wt%; the size of the hardwood nanocellulose in the hardwood nanocellulose suspension is 100-200 nm. The hardwood nanocellulose in the emulsion prepared by the method is higher in oxidation degree, smaller in size and more uniform in particle size distribution, the emulsion has stronger stability while the embedding content of the ginger essential oil is remarkably improved, and the emulsion is more stable in droplet size and more uniform in particle size distribution within 30 days of storage. In addition, the emulsion can effectively retain the active ingredients of the ginger essential oil for a long time, and improve the self oxidation resistance of the ginger essential oil, so that the antibacterial ingredients and flavor substances of the ginger essential oil are better protected.)

1. A Pickering emulsion is characterized in that: is prepared by mixing broadleaf wood nano cellulose suspension and ginger essential oil according to the volume ratio of 7:3 and then carrying out ultrasonic emulsification; wherein the solid content of the hardwood nanocellulose suspension is 0.50-0.55 wt%; the size of the hardwood nanocellulose in the hardwood nanocellulose suspension is 100-200 nm.

2. The Pickering emulsion of claim 1, wherein: the hardwood nanocellulose is obtained by the following steps:

1) soaking a hardwood pulp board in distilled water, and obtaining a cellulose suspension to be treated after defibering and ultrasonic crushing in sequence;

2) adding a proper amount of sodium periodate into the cellulose suspension to be treated, wherein the mass ratio of the sodium periodate to the solid cellulose in the suspension is 2:1, then stirring and reacting for at least 12 hours under the conditions of dark and water bath at 45 ℃, and the pH value of the system is maintained at 4.0 +/-0.1 in the reaction process;

3) centrifuging the reacted system, collecting the precipitate, and repeatedly carrying out distilled water dispersion, washing and centrifugation on the precipitate to obtain the hardwood nanocellulose.

3. The Pickering emulsion of claim 1, wherein: the hardwood nanocellulose suspension is obtained by the following steps:

1) soaking a hardwood pulp board in distilled water, and obtaining a cellulose suspension to be treated after defibering and ultrasonic crushing in sequence;

2) adding a proper amount of sodium periodate into the cellulose suspension to be treated, wherein the mass ratio of the sodium periodate to the solid cellulose in the suspension is 2:1, then stirring and reacting for at least 12 hours under the conditions of dark and water bath at 45 ℃, and the pH value of the system is maintained at 4.0 +/-0.1 in the reaction process;

3) centrifuging the reacted system and collecting precipitate, and repeatedly carrying out distilled water dispersion, washing and centrifugation on the precipitate to obtain the hardwood nanocellulose;

4) and dispersing the hardwood nanocellulose in distilled water to obtain the hardwood nanocellulose suspension.

4. The Pickering emulsion of claim 1, wherein: the hardwood nanocellulose suspension is obtained by the following steps:

1) soaking a hardwood pulp board in distilled water, and obtaining a cellulose suspension to be treated after defibering and ultrasonic crushing in sequence;

2) adding TEMPO, sodium bromide and sodium hypochlorite into the cellulose suspension to be treated, and then carrying out oxidation reaction, wherein the mass ratio of the TEMPO, the sodium bromide and the sodium hypochlorite to the solid cellulose in the suspension is 0.012-0.016: 1, 0.12-0.16: 1 and 6:1 respectively; ultrasonic vibration and mechanical stirring are simultaneously assisted in the reaction process, the pH value of the system is maintained at 10.0 +/-0.1 in the reaction process, and when the pH value of the system is not reduced any more, a proper amount of ethanol is added to stop the reaction;

3) centrifuging the reacted system, collecting precipitate, repeatedly dispersing the precipitate in distilled water after distilled water dispersion, washing and centrifugation, further dialyzing and removing impurities by using a 3500Da dialysis bag, homogenizing the suspension after impurity removal for at least 10 times at high pressure under the pressure of 400bar, wherein the processing time is 5min each time, and the suspension after homogenization is hardwood nanocellulose suspension.

The technical field is as follows:

the invention relates to the field of emulsion production processes, in particular to Pickering emulsion with ginger essential oil wrapped by hardwood nanocellulose.

Background art:

the ginger essential oil has the characteristics of enhancing the taste, removing the fishy smell, protecting the color and the like, can promote the secretion of digestive juice of a human body and enhance the appetite, and the active ingredients in the ginger essential oil also have the pharmacological activities of resisting bacteria and oxidation, inhibiting excitation of a central nervous system and the like, so the ginger essential oil can be applied to the industries of medicines, foods, spices, cosmetics and the like. However, if the ginger essential oil is exposed to light and air for a long time, the viscosity of the ginger essential oil is increased, meanwhile, the flavor substances in the ginger essential oil are volatile, and the active ingredients are also easily degraded or oxidized in the environment of illumination or oxygen, so that the optical activity of the ginger essential oil is reduced; in food applications, the biological activity of essential oils as natural preservatives is also reduced by interactions with other components of the food matrix, and is very limited in practical industrial applications.

The microcapsule embedding technology is a common method for improving the stability of plant essential oil, and the plant essential oil is wrapped by a wall material and then is subjected to spray drying treatment to prepare microcapsules, so that the stability of the plant essential oil can be effectively improved, and the retention time of flavor substances and active ingredients is prolonged. However, the microcapsule embedding technology has high requirements on wall material combination, a large amount of wall material raw materials are required to be consumed, and the spray drying process is complicated, so that further application is limited. Some novel essential oil embedding technologies emerging in recent years are only limited to embedding treatment of a small amount of essential oil, and the production process is complicated and the consumption cost is high.

The invention content is as follows:

in order to solve the problems, the invention aims to provide the Pickering emulsion with high ginger essential oil embedding content and good essential oil stability and active ingredient retention effect.

The technical scheme of the invention is as follows:

a Pickering emulsion is characterized by being prepared by mixing broadleaf wood nanocellulose suspension and ginger essential oil according to the volume ratio of 7:3 and then carrying out ultrasonic emulsification; wherein the solid content of the hardwood nanocellulose suspension is 0.50-0.55 wt%; the size of the hardwood nanocellulose in the hardwood nanocellulose suspension is 100-200 nm.

Preferably, the hardwood nanocellulose is obtained by:

1) soaking a hardwood pulp board in distilled water, and obtaining a cellulose suspension to be treated after defibering and ultrasonic crushing in sequence;

2) adding a proper amount of sodium periodate into the cellulose suspension to be treated, wherein the mass ratio of the sodium periodate to the solid cellulose in the suspension is 2:1, then stirring and reacting for at least 12 hours under the conditions of dark and water bath at 45 ℃, and the pH value of the system is maintained at 4.0 +/-0.1 in the reaction process;

3) centrifuging the reacted system, collecting the precipitate, and repeatedly carrying out distilled water dispersion, washing and centrifugation on the precipitate to obtain the hardwood nanocellulose.

More preferably, the hardwood nanocellulose (suspension) is obtained by:

1) soaking a hardwood pulp board in distilled water, and obtaining a cellulose suspension to be treated after defibering and ultrasonic crushing in sequence;

2) adding TEMPO, sodium bromide and sodium hypochlorite into the cellulose suspension to be treated, and then carrying out oxidation reaction, wherein the mass ratio of the TEMPO, the sodium bromide and the sodium hypochlorite to the solid cellulose in the suspension is 0.012-0.016: 1, 0.12-0.16: 1 and 6:1 respectively; ultrasonic vibration and mechanical stirring are simultaneously assisted in the reaction process, the pH value of the system is maintained at 10.0 +/-0.1 in the reaction process, and when the pH value of the system is not reduced any more, a proper amount of ethanol is added to stop the reaction;

3) centrifuging the reacted system, collecting precipitate, repeatedly dispersing the precipitate in distilled water after distilled water dispersion, washing and centrifugation, further dialyzing and removing impurities by using a 3500Da dialysis bag, homogenizing the suspension after impurity removal for at least 10 times at high pressure under the pressure of 400bar, wherein the processing time is 5min each time, and the suspension after homogenization is hardwood nanocellulose suspension.

The hardwood nanocellulose in the Pickering emulsion prepared by the method is higher in oxidation degree, smaller in size and more uniform in particle size distribution, the emulsion has stronger stability while the embedding content of the ginger essential oil is remarkably improved, and the emulsion is more stable in droplet size and more uniform in particle size distribution within 30 days of storage time. In addition, the emulsion can effectively retain the active ingredients of the ginger essential oil for a long time, and improve the self oxidation resistance of the ginger essential oil, so that the antibacterial ingredients and flavor substances of the ginger essential oil are better protected.

Description of the drawings:

FIG. 1 is a graph showing the trend of Zeta potential values of 2.0-cnf, 0.5-cnf, 1.0-cnf and 1.5-cnf of hardwood nanocellulose suspensions as a function of the amount of sodium periodate.

FIG. 2 is a graph showing the trend of Zeta potential values of hardwood nanocellulose suspensions 2-hcf, 6-hcf and 10-hcf as a function of sodium hypochlorite usage.

FIG. 3 is a graph showing the ESI profiles of emulsions 2.0-CNF, 0.5-CNF, 1.0-CNF and 1.5-CNF over 30 days.

FIG. 4 is a graph showing the ESI profiles of emulsions 2-HCF, 6-HCF, and 10-HCF over 30 days.

FIG. 5 is a graph of the relaxation time and peak intensity of the water component of emulsion 2.0-CNF as a function of time.

FIG. 6 is a graph of the relaxation time and peak intensity of the water components of emulsion 6-HCF as a function of time.

FIG. 7 is a comparison of the volatile content of ginger essential oil (active ingredient) in 15 days for emulsion 2.0-CNF and a control.

FIG. 8 is a comparison of the volatile content of ginger essential oil (active ingredient) in 15 days for emulsion 6-HCF and a control.

The specific implementation mode is as follows:

the technical solution and effects of the present invention will be further described with reference to the following embodiments and drawings.

Example 1

1. Preparing broadleaf wood nanocellulose:

1) soaking 5g of hardwood pulp board (oven-dried fiber) in 900-1000 g of distilled water, firstly defibering for 10min under the condition of 30000rpm by using a defibering instrument, then transferring into an ultrasonic cleaning tank with the rated power of 300W, and ultrasonically dispersing for 3min at the frequency of 30KHz at 25 ℃ to obtain a cellulose suspension to be treated with the mass fraction of 0.50-0.55 wt%;

2) adding a proper amount of sodium periodate into the cellulose suspension to be treated, wherein the mass ratio of the sodium periodate to the solid cellulose in the suspension is 2: 1; then stirring and reacting for 12 hours in a dark place (the surface of the reaction container is wrapped with aluminum foil) and under the condition of water bath at 45 ℃, and adjusting the pH of the system by using hydrochloric acid in the reaction process to maintain the pH of the system at 4.0 +/-0.1;

3) centrifuging the reacted system at 8000rpm, collecting precipitate, dispersing the precipitate with distilled water, washing, centrifuging at 8000rpm again, repeating the dispersing, washing and centrifuging processes for 3 times, and collecting the precipitate to obtain the hardwood nanocellulose (cellulose size is 100-200 nm).

2. Preparation of Pickering emulsion:

1) dispersing a proper amount of hardwood nanocellulose in distilled water to obtain a hardwood nanocellulose suspension with a solid content of 0.53 wt% of 2.0-cnf;

2) mixing 2.0-cnf hardwood nanocellulose suspension and ginger essential oil according to the volume ratio of 7:3, performing ultrasonic emulsification treatment, dispersing the mixture of the suspension and the ginger essential oil for 5 minutes by using an ultrasonic crusher with the power of 40W and the pulse of 50%, and repeating for 3 times; after the treatment, Pickering emulsion 2.0-CNF is obtained.

Example 2

1. Preparation of hardwood nanocellulose suspension:

1) soaking 5g of hardwood pulp board (absolutely dry fiber) in 900-1000 g of distilled water, firstly defibering for 10min under the condition of 30000rpm by using a defibering instrument, then transferring into an ultrasonic cleaning tank with the rated power of 300W, and ultrasonically dispersing for 3min at the frequency of 30kHz at 25 ℃ to obtain a cellulose suspension to be treated with the mass fraction of 0.50-0.55 wt%;

2) placing the cellulose suspension to be treated in a reaction vessel, and continuously adding 0.07g of TEMPO, 0.7g of sodium bromide and 30g of sodium hypochlorite for oxidation reaction; the reaction vessel is fixed in a cleaning tank of an ultrasonic cleaning device, the ultrasonic cleaning device is simultaneously connected with a mechanical stirring device, the oxidation reaction is carried out under the combined action of ultrasonic vibration with ultrasonic frequency of 30KHz and mechanical stirring with the rotating speed of 200rpm, and the reaction temperature is 25 ℃; sodium hydroxide is continuously supplemented to the system in the whole reaction process to maintain the pH value of the system at 10.0 +/-0.1, and when the pH value of the system is not reduced any more, 10mL of ethanol is added to stop the reaction.

3) Centrifuging the reacted system at 10000rpm, collecting precipitate, dispersing the precipitate with distilled water, washing, centrifuging again at 10000rpm, collecting,repeating the dispersing, washing and centrifuging processes until the impurities such as oxidant, ethanol and the like are completely removed; dispersing the washed and impurity-removed precipitate with distilled water again, dialyzing in a dialysis bag of 3500Da for further removing impurities, and replacing deionized water once per hour during dialysis until Cl^-Is completely removed (1% AgNO can be added dropwise into the dialyzed and purified suspension₃The solution is detected, no white precipitate is generated, and Cl is shown^-Is completely removed).

4) Homogenizing the suspension subjected to dialysis and impurity removal for at least 10 times at 400bar pressure by using a high-pressure homogenizer, wherein the processing time is 5min each time, and the suspension subjected to homogenization is hardwood nanocellulose (cellulose size is 150-200 nm) suspension 6-hcf.

2. Preparation of Pickering emulsion:

adjusting the solid content of hardwood nanocellulose suspension 6-hcf to 0.53 wt%, mixing with ginger essential oil according to the volume ratio of 7:3, performing ultrasonic emulsification treatment, dispersing the mixture of the suspension and the ginger essential oil for 5 minutes by using an ultrasonic crusher with the power of 40W and the pulse of 50%, and repeating for 3 times; after the treatment, Pickering emulsion 6-HCF was obtained.

Example 3

Testing of hydraulic diameter of cellulose suspension: reference example 1 method for preparing 2.0-cnf hardwood nanocellulose suspension, three hardwood nanocellulose suspensions of 0.5-cnf, 1.0-cnf and 1.5-cnf were prepared accordingly by adjusting the mass ratio of sodium periodate to solid cellulose in suspension to 0.5:1, 1:1 and 1.5:1, respectively, with only changing the addition amount of sodium periodate in the preparation step. In addition, referring to the method of example 2 for preparing hardwood nanocellulose suspensions 6-hcf, two hardwood nanocellulose suspensions, 2-hcf and 10-hcf, were prepared accordingly, with the mass ratio of sodium hypochlorite to solid cellulose in the suspension adjusted to 2:1 and 10:1, respectively, only by changing the amount of sodium hypochlorite added in the preparation step. In addition, a suspension of hardwood nanocellulose that had been subjected to sonication alone was used as a control.

The solid content of the hardwood nanocellulose suspension obtained by the method is adjusted to 0.1 wt%, and a nano-laser particle size analyzer is adopted for particle size determination and comparison. The measurement results are shown in tables 1 and 2: the hydraulic diameter of the suspension 2.0-cnf was 529.9nm, which was minimal compared to 0.5-cnf, 1.0-cnf and 1.5-cnf. Of the three samples 2-hcf, 6-hcf, and 10-hcf, the average hydraulic diameter of 10-hcf was the smallest, only 457.1 nm. The comparative nanocellulose suspension had a hydraulic diameter of 14357nm, which is much larger than the two above groups of suspensions.

TABLE 1 Hydraulic diameter comparison of suspensions 2.0-cnf, 0.5-cnf, 1.0-cnf and 1.5-cnf

NaIO4Dosage (g/g)	0.5	1.0	1.5	2.0	Control
						Hydraulic diameter (nm)	1568	1068.1	846.3	529.9	14357

TABLE 2 comparison of hydraulic diameters for suspensions 10-hcf, 2-hcf, and 6-hcf

NaClO amount (mmol/g)	2	6	10	Control
					Hydraulic diameter (nm)	1559	1002	457	14357

Example 4

Broad-leaved wood nano-cellulose suspension Zata potential test: the solid contents of the two groups of suspensions of example 3, 0.5-cnf, 1.0-cnf, 1.5-cnf, 2.0-cnf, and 2-hcf, 6-hcf, 10-hcf, were adjusted to 0.1 wt%, and 7mL of each suspension was placed in a cuvette and the Zeta potential was measured using a nanoscale laser particle sizer. The results of measurement are shown in FIGS. 1 and 2 (since the fibers adsorb OH in water)^-Therefore, the Zeta potential of each suspension was negative), in which the Zeta potential of 2.0-cnf was-31.80 mV, that of 10-cnf was-42.86 mV, and that of 2.0-cnf was much smaller than 10-cnf in absolute terms.

Example 5

And (3) determining the standing stability of the emulsion: reference example 1 the method for preparing Pickering emulsion 2.0-CNF, using hardwood nanocellulose suspension 0.5-CNF, 1.0-CNF, 1.5-CNF, 2-HCF and 10-HCF (solid content all 0.53 wt%) as raw material, mixing with ginger essential oil respectively, and then preparing five emulsions of 0.5-CNF, 1.0-CNF, 1.5-CNF, 2-HCF and 10-HCF after ultrasonic emulsification.

The emulsions 0.5-CNF, 1.0-CNF, 1.5-CNF, 2.0-CNF, 2-HCF, 6-HCF and 10-HCF were observed at room temperature for changes with time and the occurrence of delamination was observed. Photographs were taken of each emulsion sample at 0, 1, 7 and 30 days, respectively, and the height H of the emulsion phase was recorded using ImageJ 1.45s software_EAnd a total height H_TThe Emulsion stability index (ESI, Emulsion stability index) was calculated as follows:

ESI(％)＝(H_E/H_T)×100

the results of the emulsion stability test are shown in fig. 3 and 4: the ESI of 2.0-CNF at 30 days is still kept at about 90, which is obviously higher than that of 0.5-CNF, 1.0-CNF and 1.5-CNF; the ESI of 6-HCF at 30 days was still above 92, significantly higher than 2-HCF and 10-HCF.

Example 6

And (3) emulsion particle size determination: the particle size D of each emulsion sample was measured for each time period (0 day, 1 day, 7 days, and 30 days) while the emulsion stability of example 5 was measured_(3，2)And D_(4，3)And (5) performing measurement comparison. The measurement results are shown in tables 3 and 4: particle size D of 2.0-CNF in the same time period_(3，2)And D_(4，3)The particle diameter D of 6-HCF is always the smallest as compared with 0.5-CNF, 1.0-CNF and 1.5-CNF_(3，2)And D_(4，3)Maximum at the beginning of preparation, rapidly decreasing after 24h, slightly increasing in the following 1 to 7 days due to destabilization of the emulsion, gradually stabilizing in 7 to 30 days, and less than 2-HCF and 10-HCF at 30 days. The emulsion particle size measurement result is completely consistent with the emulsion stability measurement result of example 5.

TABLE 3 tendency of particle size of emulsions 2.0-CNF, 0.5-CNF, 1.0-CNF and 1.5-CNF to change with time

Note: particle diameter D_(3，2)And D_(4，3)Has a unit of μm

TABLE 4 tendency of particle size of emulsions 6-HCF, 2-HCF and 10-HCF over time

Note: particle diameter D_(3，2)And D_(4，3)Has a unit of μm

Example 7

Turbiscan Stability (TSI) test at the initial stage of emulsion preparation: the tendency of TSI values of the emulsions 2.0-CNF and 6-HCF to change with time within 6 hours of preparation was determined using a Turbiscan stability analyzer. The measurement results are shown in tables 5 and 6: the TSI values of 2.0-CNF and 6-HCF increased with time within 6 hours of preparation, to 21579s (6 hours) the TSI values of 2.0-CNF and 6-HCF increased to 1.76% and 1.28%, respectively, indicating that both emulsions had good stability, with better stability of 6-HCF.

TABLE 5 TSI values of emulsion 2.0-CNF trend over time

t(s*)	0	1193	2378	3573	4778	6013	7181	8379	9579	10902
											TSI(％)	0	0.1018	0.2050	0.3058	0.4045	0.4956	0.5684	0.6365	0.7132	0.8018
t(s)	12003	13177	14383	15579	16781	17983	19190	20406	21579
											TSI(％)	0.8713	0.9587	1.0543	1.1624	1.2855	1.4004	1.5147	1.6366	1.7555

S is time unit, second

TABLE 6 TSI values of emulsion 6-HCF trend over time

t(s*)	0	1209	2401	3600	4797	5983	7194	8394	9609	10805
											TSI(％)	0	0.1300	0.2398	0.3151	0.3933	0.4842	0.5613	0.6210	0.6780	0.7385
t(s)	11986	13181	14379	15577	16782	18001	19190	20407	21597
											TSI(％)	0.7954	0.8493	0.9132	0.9783	1.0318	1.0968	1.1605	1.2209	1.2782

S is time unit, second

Example 8

Low-field nuclear magnetic resonance test: low field NMR tests were performed on emulsions 2.0-CNF and 6-HCF over 6 hours of preparation. The test results are shown in fig. 5 and 6, the relaxation time and peak intensity of the emulsion 2.0-CNF between various water components only show small changes within 6 hours of the test time after preparation, and the relaxation time of free water is not obviously prolonged, which indicates that the emulsion system is stable; within the test time of 6 hours after the preparation of the emulsion 6-HCF, the relaxation time of the combined water in the system is hardly changed, the relaxation time of the free water is not changed, and only the signal peak intensity of the free water is increased by 0.90 percent, so that the emulsion 6-HCF has better stability than the emulsion 2.0-CNF.

Example 9

Testing the retention effect of the active ingredients of the essential oil: and (3) adopting a solid phase microextraction-gas chromatography-mass spectrometry method to measure the volatile amount of the ginger essential oil in the emulsions of 2.0-CNF, 6-HCF and a control. Wherein, the emulsion used as the contrast is prepared by mixing the suspension (solid content is 0.53 wt%) of hardwood nanocellulose which is only subjected to ultrasonic crushing treatment with ginger essential oil according to the volume ratio of 7:3 and then carrying out ultrasonic emulsification.

The measurement results are shown in fig. 7 and 8: compared with the control, the volatile amount of each volatile component of the ginger essential oil in 15 days of the emulsion 2.0-CNF is obviously lower; the volatile content of the emulsion 6-HCF except (+) -BETA-cedrene is higher than that of the control, and the volatile content of the other volatile components is even lower than that of the emulsion 2.0-CNF, so that the emulsion has excellent retention effects on active ingredients of essential oil and flavor substances.