CN107367468A - A kind of free fatty acid determination method in edible oil - Google Patents
A kind of free fatty acid determination method in edible oil Download PDFInfo
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- CN107367468A CN107367468A CN201710655504.0A CN201710655504A CN107367468A CN 107367468 A CN107367468 A CN 107367468A CN 201710655504 A CN201710655504 A CN 201710655504A CN 107367468 A CN107367468 A CN 107367468A
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N21/00—Investigating or analysing materials by the use of optical means, i.e. using sub-millimetre waves, infrared, visible or ultraviolet light
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- G01N21/25—Colour; Spectral properties, i.e. comparison of effect of material on the light at two or more different wavelengths or wavelength bands
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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Abstract
The embodiments of the invention provide a kind of semiquantitative determination method of free fatty in edible oil, including：(1) free fatty in edible oil is extracted with extractant, obtains the extraction phase to be measured containing free fatty, wherein, the volume of the extractant is identical with the volume of edible oil；(2) extraction phase to be measured of designated volume is taken, and is separately added into nano-Au solution and cationic polymer solution thereto, color is fully mixed to and no longer changes, obtain Colorimetric System to be measured；(3) color of the color of the Colorimetric System to be measured respectively with Standard Colorimetric System is contrasted, determines the content range of free fatty in edible oil.Free fatty acid determination method, has advantages below in edible oil provided in an embodiment of the present invention：(1) analysis time of the invention is short, and semi-quantitative analysis can be completed within a few minutes, and compared with titration method, detection is more rapidly.(2) present invention is few using the amount of organic solvent, green.
Description
Technical field
The present invention relates to edible oil quality control technology field, more particularly to a kind of survey of free fatty in edible oil
Determine method.
Background technology
During free fatty (FFA) in edible oil occurs mainly with its processing and stored.Free fatty occurs
It is rotten to produce harmful H2O2.Therefore, in edible oil the content (total content) of free fatty usually as assessment
One critically important parameter of edible oil quality and economic value.The standard method detected at present mainly has U.S.'s oil product Science of Chemistry
The national standard method (GB/T 5530-2005) of meeting (AOCS), the European Community (EC) and China, these methods are similar, all
Recommendation is dissolved a sample in ethanol, and using highly basic as titrant, phenolphthalein is that indicator is surveyed to free fatty acid content
It is fixed.Titration method do not only exist it is time-consuming, consumption solvent the shortcomings of, and when oil samples color to be measured is deeper by titration method very
Hardly possible judges its titration end-point.In view of this, how the free fatty faster detected in edible oil turns into this area
Technical staff's urgent problem to be solved.
The content of the invention
Nanogold (AuNPs) refers to golden molecule of the diameter in 1~100nm, and research is found, when nanogold particle diameter exists
When in the range of 10-50nm, nano-Au solution takes on a red color.And after nanogold is assembled, its surface plasma body resonant vibration is inhaled
Red shift occurs for take-up, and correspondingly, nano-Au solution color experience is changed into blueness from red, and with the naked eye can is seen for this change
Examine.Importantly, their molar extinction coefficient is very high, three orders of magnitude higher than conventional organic coloring agent, therefore detect spirit
Sensitivity is high.
The surface of cationic polymer is general or can carry positive charge under certain condition, and this characteristic can cause scattered
The nanogold of state is assembled, and forms the nanogold of state of aggregation, so as to change the color of nano-Au solution, makes nano-Au solution face
Color is changed into blue (state of aggregation) from red (dispersed).
Present invention research finds the cationic polymer of micro-molar concentration (uM) rank, the dendroid polyamides in especially whole generation
Amine amine is easy to allow nanogold that clustering phenomena occurs；Nanogold (dispersed) solution colour is red, and central absorption wavelength exists
520nm；When adding certain density cationic polymer, such as the dendroid daiamid (PAMAM G1.0) in 1 generation thereto
After macromolecular, macromolecular makes nanogold particle cause nano-Au solution color in a short time there occurs clustering phenomena, such as
It is changed within 3-5 seconds blueness, now center maximum absorption wavelength is transferred to 650nm.Added when into nanogold (dispersed) solution
The aliphatic acid that concentration is identical but chain length is different, when adding above-mentioned cationic polymer, it is found that butyric acid and caproic acid are several to assembling
There is no inhibitory action, solution becomes blue immediately after adding PAMAM；But with the increase of carbon chain lengths, the aliphatic acid pair of addition
The inhibitory action of aggregation also increases, and shows as the color of solution without becoming blue completely, also keeps a certain degree of red, you can with
Suppress the generation of this aggregation to some extent.Present invention research is it has furthermore been found that carbon chain lengths are C16-C18 aliphatic acid pair
The aggregation rejection ability of nanogold approaches；Meanwhile the aliphatic acid in edible oil is mainly palmitic acid (C16-0), stearic acid (C18-
0), oleic acid (C18-1) and linoleic acid (C18-2) (GB 19111-2003；Journal of Agricultural and Food
Chemistry, 2011,59,10775-10780), in view of this, the embodiments of the invention provide the fat that dissociates in a kind of edible oil
The assay method of fat acid, to realize the free fatty that can faster detect in edible oil.Concrete technical scheme is as follows：
First aspect present invention provides a kind of fatty acid determination method of dissociating in edible oil, and it includes：
(1) free fatty in edible oil is extracted with extractant, obtains the extraction phase to be measured containing free fatty, its
In, the volume of the extractant is identical with the volume of edible oil；
(2) extraction phase to be measured of designated volume is taken, it is mixed with nano-Au solution and cationic polymer solution,
No longer change to color, obtain Colorimetric System to be measured；
(3) color of the color of the Colorimetric System to be measured and Standard Colorimetric System is contrasted, determined in edible oil
The content range of free fatty；
Wherein, the Standard Colorimetric System determines by the following method：
Standard liquid with the extractant from the different content of fatty acid of fatty acid standards preparation, in the standard liquid
Content of fatty acid, it is known that the fatty acid standards be selected from C16-C18 aliphatic acid；
The standard liquid of the designated volume is taken respectively, and itself and nano-Au solution and cationic polymer solution are mixed
Close, no longer change to color, obtain Standard Colorimetric System；The volume phase of the Standard Colorimetric System and the Colorimetric System to be measured
Together；And in the Standard Colorimetric System nanogold and the concentration of cationic polymer respectively with nanometer in the Colorimetric System to be measured
Gold is identical with the concentration of cationic polymer.
In a kind of embodiment of first aspect present invention, in step (3), free-fat in edible oil is determined
The content range of acid, it is specially：When the Colorimetric System to be measured color between two adjacent content of fatty acid standard liquid
When between the color of corresponding Standard Colorimetric System, determine the content of free fatty in edible oil in described two adjacent fat
Between fat acid content.
In actual applications, different content of fatty acid can be prepared according to the edible oil acidity value upper limit of national Specification
Standard liquid, such as, standard GB/T 19111-2003 regulation one-level, two level, three-level and level Four squeezing finished product edible corn
The acidity value (in terms of KOH, mg/g) of oil should be no more than 0.2,0.3,1.0,3.0；Content of fatty acid in corresponding standard liquid
Represented with aliphatic acid molar concentration, respectively 4.46mM, 6.70mM, 22.3mM and 67.0mM.In the case, in step
(3), can be by the standard colorimetric corresponding to the color of Colorimetric System to be measured and such as one-level, two level, three-level and level Four standard in
The color of system is compared；When the color of Colorimetric System to be measured is between the color corresponding to two neighboring rank, so that it may
To determine the content of the free fatty in edible oil between the two neighboring rank, it is possible to achieve containing for sxemiquantitative measures
It is fixed.In the present invention, standard liquid institute of the color of the described Colorimetric System to be measured between two adjacent content of fatty acid
Between the color of corresponding Standard Colorimetric System, it can be understood as the red phase (blue phase) that the Colorimetric System to be measured is presented
The red phase (blue phase) that the Standard Colorimetric System corresponding to standard liquid between two adjacent content of fatty acid is presented it
Between.
In a kind of embodiment of first aspect present invention, fatty acid standards are selected from palmitic acid, stearic acid, oil
At least one of acid and linoleic acid.
In a kind of embodiment of the present invention, after Standard Colorimetric System is made, its color can be passed through
Optional mode is recorded on carrier, such as can be recorded on card or sheet material, is made as with Standard Colorimetric System color
Standard color comparison card or standard colorimetric plate；The color of Standard Colorimetric System can be so preserved for a long time, treated when needing detection
When surveying the color gamut of Colorimetric System, as long as by its color contrast with standard color comparison card or standard colorimetric plate.Need
Bright, described carrier, can be with other any suitable for Standard Colorimetric System face is presented in addition to it can be card or sheet material
The carrier of the material of color.
In a kind of embodiment of the present invention, the color of the Colorimetric System to be measured and the face of Standard Colorimetric System
Color specifically can be with the calibration curve of Colorimetric System to be measured and the respective uv-visible absorption spectra of Standard Colorimetric System come table
Show.Specifically, absorbance A at 520nm can be passed through520To represent, or by passing through absorbance A at 650nm650Carry out table
Show.In this embodiment, as the A of the Colorimetric System to be measured520Standard liquid institute between two adjacent content of fatty acid is right
The A for the Standard Colorimetric System answered520Between when, determine the content of free fatty in edible oil in described two adjacent aliphatic acid
Between content.Or the A when the Colorimetric System to be measured650The mark corresponding to standard liquid between two adjacent content of fatty acid
The A of quasi- Colorimetric System650Between when, determine the content of free fatty in edible oil described two adjacent content of fatty acid it
Between.
, can be in advance by the absorbance of Standard Colorimetric System in order to further shorten the fatty acid determination time in edible oil
Peak value, such as A520Or A650Record, can be it is determined that the calibration curve of Colorimetric System to be measured when detection, such as A520
Or A650Afterwards, directly compared with the calibration curve of the Standard Colorimetric System recorded；Easily and fast.
In the inventive solutions, extractant should select fully, by free fatty from edible oil to extract
Take out, even if free fatty is transferred in extractant from edible oil, the extraction phase containing aliphatic acid is formed, in order to examine
Survey.Based on this, in a kind of embodiment of first aspect present invention, extractant is the mixed solvent of methanol and water, excellent
Selection of land, the volume ratio of methanol and water is 2 in the extractant：1, i.e., described extractant is 2 by volume ratio：1 methanol and water
Mix.
In a kind of embodiment of first aspect present invention, the grain of contained nanogold in the nano-Au solution
Footpath scope is 10-50nm；Preferably 10-20nm, more preferably 13nm.In the present invention, to the source of nanogold without limit
It is fixed, it is for instance possible to use reduction method for preparing nanometer gold solution；During reduction method for preparing nanometer gold, gold chloride is gone back in original
In the presence of agent, a certain size nanogold particle is polymerized to, forms the hydrophobic sol solution of electronegative nanogold, the nanogold is hydrophobic
Sol solution can be used as nano-Au solution use.Common reducing process has white phosphorus reducing process, ascorbic acid reduction, sodium citrate
Reducing process and tannic acid-reduction of sodium citrate method etc..Those skilled in the art can come according to actual need, such as the particle diameter of nanogold
It is determined that specific reducing process, the present invention is herein without determining.
The cationic polymer solution of the present invention can be used by cationic polymer being dissolved in solvent to obtain
Solvent can select water or organic solvent, the organic solvent can non-exclusively be selected from methanol, ethanol or acetonitrile etc..
In a kind of embodiment of first aspect present invention, cationic polymer is selected from, but not limited to, dendroid and gathered
Amide amine (PAMAM), hyperbranched poly propyleneimine (Poly (propyleneimine), PPI), hyperbranched polyethyleneimine
(PEI), at least one of polylysin (polylysine) and chitosan (chitosan)；In the another of first aspect present invention
In a kind of embodiment, cationic polymer is selected from dendroid daiamid；In another tool of first aspect present invention
In body embodiment, cationic polymer is selected from the dendroid daiamid in 1 generation, 2 generations, 3 generations and/or 4 generations.Gather for dendroid
The preparation method of amide amine, the present invention is herein without limiting.
In a kind of embodiment of first aspect present invention, in the Colorimetric System to be measured and the standard colorimetric
In system, the concentration of nanogold is 4.6 × 10-10M to 1.04 × 10-9M, preferably 6.0 × 10-10M to 1.0 × 10-9M；Sun from
The concentration of sub- polymer is 0.05-0.3uM, preferably 0.1-0.2uM.
In step (2), mixed when by the extraction phase to be measured of designated volume with nano-Au solution and cationic polymer solution
After conjunction, nanogold can change color in the presence of the aliphatic acid in cationic polymer and extraction phase to be measured；Usually, exist
After nano-Au solution and cationic polymer solution are mixed with extraction to be measured, vibration mixing about 3-5 minutes, color is basic
It is stable no longer to change.In a kind of embodiment of the present invention, extraction phase to be measured is gathered with nano-Au solution and cation
Polymer solution mixes, and is particularly preferred as：First extraction phase to be measured is mixed with nano-Au solution, after mixing, cation is added and gathers
Polymer solution；
Standard liquid is mixed with nano-Au solution and cationic polymer solution, is particularly preferred as：First by standard liquid
Mixed with nano-Au solution, after mixing, add cationic polymer solution.
In a kind of embodiment of first aspect present invention, especially using PAMAM as cationic polymer when,
PH value in the Colorimetric System to be measured and the Standard Colorimetric System is 4-10, is 4.6-7.2 preferably in pH value, in this scope
Interior, system has response to the content of aliphatic acid, and more preferably pH value is 5.2, sensitivity highest now.In this pH value,
It is more suitable for carrying out the detection of aliphatic acid.
Inventor on foregoing Research foundation further study show that, when nano-Au solution and cationic polymer is molten
Liquid mixes, and after forming nanogold-cationic polymerization objects system, adds aliphatic acid thereto, the concentration of aliphatic acid influences PAMAM pairs
AuNPs rejection abilities, concentration is bigger, and rejection ability is bigger, shows as the increase with fatty acid concentration, and state of aggregation AuNPs exists
Absorption value at 650nm reduces, meanwhile, dispersed AuNPs is in 520nm absorption value increase, as shown in Figure 1.Energy will be suppressed
Power is with the AuNPs of dispersed maximum absorbance A520With the maximum absorbance A of state of aggregation650Ratio A520/A650To weigh, and
Itself and the concentration of aliphatic acid (by taking oleic acid as an example) that is added are mapped, find it is linear in certain concentration range,
As shown in Figure 2.Illustrate that the content of aliphatic acid can be carried out quantitative detection based on this principle.The research of ultraviolet spectra is further
Prove, if using colorimetric determination, with the ratio A at 520nm with absorbance at 650nm520/A650(y) to the dense of aliphatic acid
Degree (x, μM) make linear regression (5 concentration levels), the slope of calibration curve is close, as shown in table 1, that is, these four aliphatic acid
Sensitivity it is close.
The carbon chain lengths of table 1 are the C16-C18 detection range of linearity and calibration curve
Based on above-mentioned research, second aspect of the present invention provides a kind of quantitative determination side of free fatty in edible oil
Method, it includes：
(A) N-1 parts into N part extractants are separately added into the fatty acid standards of different known quantities, obtain N part aliphatic acid
The different standard liquid of standard items content；The volume of N part standard liquids is identical, N >=3；The fatty acid standards are selected from C16-
C18 aliphatic acid；
(B) free fatty in N part edible oils is extracted respectively with N parts standard liquid, obtain the extraction of N parts testing sample
Phase, wherein, the volume of edible oil is identical with the volume of standard liquid；
(C) from N part testing sample extraction phases, it is V to obtain volume respectively1Test solution；N parts are tested in solution and divided
Do not mix with nano-Au solution and cationic polymer solution, no longer change to color, it is V to obtain N parts volume0Testing sample
Solution；In all testing sample solutions, the concentration of nanogold is identical, and the concentration of cationic polymer is identical；
(D) it is V by volume1Extractant and nano-Au solution and cationic polymer solution mixing, to color no longer
Change, it is V to obtain volume0Blank sample solution；The concentration and cationic polymerization of nanogold in the blank sample solution
The concentration of thing is identical with testing sample solution respectively；
(E) uv-visible absorption spectra test is carried out to N parts testing sample solution and blank sample solution respectively；It is determined that
The ratio A of every part of testing sample solution absorbance at 520nm and at 650nm520/A650；
(F) with A520/A650For ordinate, using the content of fatty acid standards added in testing sample solution as horizontal seat
Mark, the Standard entertion curve of mapping sample solution is drawn, the value of the ordinate of the point of intersection of the abscissa and ordinate is sky
The A of white sample solution520/A650；And according to formulaThe content of the free fatty in edible oil is determined, wherein, ρ tables
Show the content of the free fatty in edible oil, c represents the content of the point of intersection of Standard entertion curve and abscissa.Need to illustrate
, the value of the abscissa of the point of intersection of the abscissa and ordinate is 0, represents the aliphatic acid added in testing sample solution
The content of standard items is 0.
It should be noted that although cationic polymer makes the color of nano-Au solution become blue, but do not make to own
Nanogold particle produces reunion, is also partially in the nanogold particle of dispersed；Therefore, even if test system is only comprising extraction
Agent, nano-Au solution and cationic polymer solution, the ratio A of its absorbance520/A650It is not 0 yet.Based on this, in the present invention
Technical scheme in, by the A of blank sample solution520/A650As the value of abscissa and the ordinate of the point of intersection of ordinate, hand over
The value of abscissa at point remains as 0.
It should be noted that herein, the content of the free fatty in described edible oil is referred in edible oil
The total content of free fatty, also referred to as acidity value.
In a kind of embodiment of second aspect of the present invention, fatty acid standards are selected from palmitic acid, stearic acid, oil
At least one of acid and linoleic acid.
In a kind of embodiment of second aspect of the present invention, the extractant is the mixed solvent of methanol and water,
Preferably, the volume ratio of methanol and water is 2 in the extractant：1.
In a kind of embodiment of second aspect of the present invention, the grain of contained nanogold in the nano-Au solution
Footpath scope is 10-50nm；Preferably 10-20nm, more preferably 13nm.
In a kind of embodiment of second aspect of the present invention, cationic polymer be selected from dendroid daiamid,
At least one of hyperbranched poly propyleneimine, hyperbranched polyethyleneimine, polylysin and chitosan；Preferably, cation gathers
Compound is selected from dendroid daiamid；It is highly preferred that the dendroid that cationic polymer is selected from 1 generation, 2 generations, 3 generations and/or 4 generations is gathered
Amide amine.
In a kind of embodiment of second aspect of the present invention, in the testing sample solution, nanogold it is dense
Spend for 4.6 × 10-10M to 1.04 × 10-9M, preferably 6.0 × 10-10M to 1.0 × 10-9M；The concentration of cationic polymer is
0.05-0.3uM, preferably 0.1-0.2uM.
In a kind of embodiment of second aspect of the present invention, test solution is gathered with nano-Au solution and cation
Polymer solution mixes, and is specially：First test solution is mixed with nano-Au solution, after mixing, it is molten to add cationic polymer
Liquid.Inventor has found that when being mixed in this order, the linear relationship of ultraviolet spectral analysis is more preferable.
In a kind of embodiment of second aspect of the present invention, the Colorimetric System to be measured, the standard colorimetric body
PH value in system and the testing sample solution is 4-10, is 4.6-7.2 preferably in pH value, within this range, system is to fat
The content of acid has response, and more preferably pH value is 5.2, sensitivity highest now.In this pH value, it is more suitable for carrying out fat
The detection of acid.
In a kind of embodiment of second aspect of the present invention, the content of fatty acid standards in testing sample solution
≤10μM。
It should be noted that the second aspect of the present invention content related to first aspect is referred to the note of first aspect
Carry, the present invention is no longer repeated herein.
Explanation is needed further exist for, described " content " refers to certain composition included in predetermined substance herein
Amount, for example, the amount of free fatty is included in edible oil, or amount comprising fatty acid standards etc. in testing sample solution.
Herein, it there may come a time when that also referred to as content is concentration, especially occurs simultaneously in same calculation formula or similar scene
When content and concentration, concentration and content there should be identical unit as identical concept, concentration with content.
Free fatty acid determination method in edible oil provided in an embodiment of the present invention, it is possible to achieve sxemiquantitative is quantitative
Determine the content of free fatty in edible oil.And there is advantages below：
(1) analysis time of the invention is short, and semi-quantitative analysis can be completed within a few minutes, compared with titration method, detection
More rapidly.
(2) present invention is few using the amount of organic solvent, green.
(3) because AuNP has a high molar extinction coefficient, the sensitivity of quantitative analysis of the present invention is very high.
Brief description of the drawings
In order to illustrate more clearly about the embodiment of the present invention or technical scheme of the prior art, below will be to embodiment or existing
There is the required accompanying drawing used in technology description to be briefly described, it should be apparent that, drawings in the following description are only this
Some embodiments of invention, for those of ordinary skill in the art, on the premise of not paying creative work, can be with
Other accompanying drawings are obtained according to these accompanying drawings.
Fig. 1 is influence of the oleic acid concentration to nanogold-cationic polymerization objects system visible spectrum, wherein, curve 1-6 is corresponding
System in, the concentration of nanogold is 6.5 × 10-10M, PAMAM G1.0 concentration are 0.13uM；System corresponding to curve 1-6
In, the concentration of oleic acid is respectively:0、5uM、10uM、20uM、35uM、45uM；Curve 7 is concentration 6.5 × 10-10M nanogold is molten
Liquid；
Fig. 2 is the A of nanogold-cationic polymerization objects system corresponding to the oleic acid of various concentrations520/A650Calibration curve
Figure, wherein, the concentration of the nanogold in nanogold-cationic polymerization objects system is 6.5 × 10-10M, PAMAM G1.0's is dense
Degree is 0.13uM；
Fig. 3 is PAMAM G1.0 nuclear magnetic spectrograms (400MHz, CDCl prepared by embodiment 23, ppm),
Peak belongs to：δ2.35(m,8H,NCH 2CH2CONH),2.40(s,1,4H,NCH 2CH2N),2.65(m,8H,
CONHCH2CH 2NH2),2.81(m,8H,NCH2CH 2CONH),3.27(m,8H；CONHCH 2)。
Embodiment
Below in conjunction with the accompanying drawing in the embodiment of the present invention, the technical scheme in the embodiment of the present invention is carried out clear, complete
Site preparation describes, it is clear that described embodiment is only part of the embodiment of the present invention, rather than whole embodiments.It is based on
Embodiment in the present invention, those of ordinary skill in the art are obtained every other under the premise of creative work is not made
Embodiment, belong to the scope of protection of the invention.
It should be noted that although following examples are to be illustrated by taking PAMAM G1.0 as an example as cationic polymer
Technical scheme, still, for the PAMAM, especially 2-4 generations of other whole algebraically PAMAM, and hyperbranched poly third
The cationic polymers such as alkene imines, hyperbranched polyethyleneimine, polylysin and chitosan, it can similarly realize the skill of the present invention
Art scheme.
The preparation of the nano-Au solution of embodiment 1
By 1mL 1%HAuCl4It is added in 250mL round-bottomed flask, adds 99mL distilled water three times.Stirred in magnetic force
Lower heating is mixed, 1.5mL 1% sodium citrate solution is rapidly joined thereto after seething with excitement as reducing agent, treats color by pale yellow
Color stops stirring to solution after blueness fades to claret (solution backflow 25min) again and cooled down.This nano-Au solution is transferred to
In 100mL volumetric flasks, lucifuge is stored in 4 DEG C of refrigerators after being diluted to graduation mark with water three times.This nano-Au solution concentration is used up
Spectrometry is determined as 8.5 × 10-10M。
The PAMAM of embodiment 2 preparation
Using ethylenediamine as core, methanol is reaction dissolvent, is outwards expanded using divergent method.At room temperature ethylenediamine first with excess
Methyl acrylate carry out Michael addition reaction 24 hours, product is in 50 DEG C of decompression removal of impurities.The ester that the first step obtains again with mistake
The ethylenediamine of amount carries out ammoxidation 72 hours at room temperature, and product cleans in 72 DEG C of decompressions, obtains 0 generation dendroid and divides greatly
Son.1.0 generation dendritic macromoles can be obtained by being alternately repeated Michael addition reaction and ammoxidation.Product is through cleaning, doing
Freezen protective after dry.By NMR spectrum (- 400MHz NMR the spectrometer of A Bruker Advance III,
Rheinstetten Germany) characterized.As a result it is as shown in Figure 3.Prepared PAMAM G1.0 are prepared into concentration is
The 0.53uM aqueous solution.
The half-quantitative detection of free fatty in the edible corn oil of embodiment 3
Extractant is the mixed solution of methanol and water, volume ratio 2：1. by the extractant and food of isometric (being all 1mL)
Mixed with corn oil, vibrate 3 minutes, separate extraction phase to be detected with edible corn oil after being layered.
Nano-Au solution prepared by 1.5mL embodiments 1 is added in 5mL tool plug vial, is added under agitation
10 μ L extraction phases to be detected, after being sufficiently mixed, add the PAMAM G1.0 dendritic macromoles that 490 μ L concentration are 0.53uM
(prepared by embodiment 2), is sufficiently mixed after colour stable, obtains Colorimetric System to be measured (PAMAM G1.0 in Colorimetric System to be measured
Ultimate density is 0.13uM, and the concentration of nanogold is 6.5 × 10-10M)。
The standard liquid of free fatty, standard GB/T are prepared according to the edible oil acidity value upper limit of national Specification
19111-2003 provides that the acidity value (in terms of KOH, mg/g) of one-level, two level, three-level and level Four squeezing finished product edible corn oil should
No more than 0.2,0.3,1.0,3.0；Corresponding aliphatic acid molar concentration is respectively 4.46mM, 6.70mM, 22.3mM and
67.0mM.Using oleic acid as fatty acid standards, oleic acid is dissolved in extractant, 4 parts of standard liquids of above-mentioned concentration are made.
The nano-Au solution of the preparation of 1.5mL embodiments 1 is separately added into 5mL tool plug vial, adds 10 μ L marks under agitation
Quasi- solution, after being sufficiently mixed, adding the PAMAM G1.0 dendritic macromoles that 490 μ L concentration are 0.53uM, (embodiment 2 is made
It is standby), it is sufficiently mixed after colour stable, obtains 4 parts of Standard Colorimetric Systems (PAMAM G1.0 ultimate densities in Colorimetric System to be measured
For 0.13uM, the concentration of nanogold is 6.5 × 10-10M)。
The color contrast of Colorimetric System to be measured and 4 parts of Standard Colorimetric Systems is understood that the color of Colorimetric System to be measured is than one
The color of Standard Colorimetric System corresponding to level corn oil is more blue, it is thus determined that content of fatty acid in measured edible corn oil
It is not above the content of fatty acid (acidity value) that one-level squeezing finished product uses corn oil.
The quantitative detection of free fatty in the edible corn oil of embodiment 4
Extractant is the mixed solution of methanol and water, volume ratio 2：1.It is separately added into 5 2mL tool plug vials
The extraction agent solution of 0.5mL oleic acid, the concentration of wherein oleic acid is respectively 0,400,800,1200,1600 μM.Again respectively to above-mentioned
0.5mL edible corn oils are added in bottle, is vibrated 3 minutes after mixing, extraction phase is separated with edible corn oil after being layered, obtained
5 parts of testing sample extraction phases.The nano-Au solution of the preparation of 1.5mL embodiments 1 is separately added into 5mL tool plug vial,
The above-mentioned testing sample extraction phases of 10 μ L (test solution) are added under stirring condition, after being sufficiently mixed, adding 490 μ L concentration is
0.53uM PAMAM G1.0 dendritic macromoles (prepared by embodiment 2), are sufficiently mixed after colour stable, obtain 5 parts it is to be measured
Sample solution；
5mL tool plug vial in successively add 1.5mL embodiments 1 preparation nano-Au solution, 10 μ L extractants and
490 μ L concentration are 0.53uM PAMAM G1.0 dendritic macromoles (prepared by embodiment 2), are sufficiently mixed after colour stable,
Obtain blank sample solution；
With ultraviolet-uisible spectrophotometer (UV-2450, Shimadzu, Japan) to each testing sample solution and blank sample solution
Absorbance measurement is carried out, uv scan scope is 400-900nm, and with the ratio at 520nm with absorbance at 650nm
A520/A650(y) to oleic acid content (concentration) (x, μM) mapping in testing sample solution, the standard for drawing mapping sample solution adds
Enter curve, the value of the ordinate of the point of intersection of the abscissa and ordinate is the A of blank sample solution520/A650, its value is
0.58；The value of abscissa is 0 μM；Determine 15.25 μM of the content value c=... of the point of intersection of Standard entertion curve and abscissa；V1
=10 μ L；V0=2000 μ L；And according to formulaThe content for determining the free fatty in edible oil is 3050 μM.
Free fatty acid content in the standardized titration method of comparative example 1 measure edible corn oil
The measurement of total fatty acid content is detected with reference to standard GB/T/T 5530-2005：
(1) accurately weigh a certain amount of edible corn oil (detecting oil used in embodiment 4) to be placed in conical flask, add
The ethanol of 50mL 95%.
(2) add 2mL 1% phenolphthalein indicator, phenolphthalein indicator with 95% ethanol preparation, relief food plant
Oil and ethanol are sufficiently mixed.
(3) titrated, dripped while shaking up, until solution becomes pink with 0.01M standard potassium hydroxide solution
Keep 30s constant.
Measurement three times, obtains result such as following table：
The titration measurement of aliphatic acid in the edible corn oil of table 2
From the point of view of the testing result of embodiment 4 and documents 1, quantitative detecting method and conventional titration provided by the invention
The measurement result of method approaches, and therefore, traditional titration can be replaced to be used to enter the content of the free fatty in edible oil
Row detection.
Fatty acid determination method of dissociating in a kind of edible oil provided by the present invention is described in detail above.This
Apply specific embodiment in text to be set forth the principle and embodiment of the present invention, the explanation of above example is simply used
Understand the method and its central idea of the present invention in help.It should be pointed out that for the person of ordinary skill of the art, not
On the premise of departing from the principle of the invention, some improvement and modification can also be carried out to the present invention, these are improved and modification is also fallen into
The protection of the claims in the present invention.
Claims (10)
1. a kind of semiquantitative determination method of free fatty in edible oil, it is characterised in that including：
(1) free fatty in edible oil is extracted with extractant, obtains the extraction phase to be measured containing free fatty, wherein,
The volume of the extractant is identical with the volume of edible oil；
(2) extraction phase to be measured of designated volume is taken, it is mixed with nano-Au solution and cationic polymer solution, to face
Color no longer changes, and obtains Colorimetric System to be measured；
(3) color of the color of the Colorimetric System to be measured and Standard Colorimetric System is contrasted, determines to dissociate in edible oil
The content range of aliphatic acid；
Wherein, the Standard Colorimetric System determines by the following method：
Standard liquid with the extractant from the different content of fatty acid of fatty acid standards preparation, the fat in the standard liquid
Fat acid content is, it is known that the fatty acid standards are selected from C16-C18 aliphatic acid；
The standard liquid of the designated volume is taken respectively, and it is mixed with nano-Au solution and cationic polymer solution,
No longer change to color, obtain Standard Colorimetric System；The volume of the Standard Colorimetric System and the Colorimetric System to be measured is identical；
And in the Standard Colorimetric System nanogold and the concentration of cationic polymer respectively with nanogold in the Colorimetric System to be measured
It is identical with the concentration of cationic polymer.
2. the method as described in claim 1, it is characterised in that in step (3), determine containing for free fatty in edible oil
Scope is measured, is specially：When corresponding to standard liquid of the color between two adjacent content of fatty acid of the Colorimetric System to be measured
Standard Colorimetric System color between when, determine that the content of free fatty in edible oil contains in described two adjacent aliphatic acid
Between amount.
3. the method as described in claim 1, it is characterised in that the color of the Standard Colorimetric System is recorded on carrier.
4. the method as described in claim 1, it is characterised in that the color of the Colorimetric System to be measured and Standard Colorimetric System
Color is represented with the calibration curve of Colorimetric System to be measured and the respective uv-visible absorption spectra of Standard Colorimetric System.
A kind of 5. method for quantitatively determining of free fatty in edible oil, it is characterised in that including：
(A) N-1 parts into N part extractants are separately added into the fatty acid standards of different known quantities, obtain N part Fatty acid standards
The different standard liquid of product content；The volume of N part standard liquids is identical, N >=3；The fatty acid standards are selected from C16-C18's
Aliphatic acid；
(B) free fatty in N part edible oils is extracted respectively with N parts standard liquid, obtain N part testing sample extraction phases, its
In, the volume of edible oil is identical with the volume of standard liquid；
(C) from N part testing sample extraction phases, it is V to obtain volume respectively1Test solution；N parts are tested into solution respectively with receiving
Rice gold solution and cationic polymer solution mixing, no longer change, it is V to obtain N parts volume to color0Testing sample solution；
In all testing sample solutions, the concentration of nanogold is identical, and the concentration of cationic polymer is identical；
(D) it is V by volume1Extractant and nano-Au solution and cationic polymer solution mixing, no longer change to color,
It is V to obtain volume0Blank sample solution；The concentration of nanogold in the blank sample solution and cationic polymer it is dense
Degree is identical with testing sample solution respectively；
(E) uv-visible absorption spectra test is carried out to N parts testing sample solution and blank sample solution respectively；Determine every part
The ratio A of testing sample solution absorbance at 520nm and at 650nm520/A650；
(F) with A520/A650For ordinate, using the content of fatty acid standards added in testing sample solution as abscissa, paint
The Standard entertion curve of mapping sample solution processed, the value of the ordinate of the point of intersection of the abscissa and ordinate is blank sample
The A of solution520/A650；And according to formulaThe content of the free fatty in edible oil is determined, wherein, ρ represents edible
The content of free fatty in oil, c represent the content of the point of intersection of Standard entertion curve and abscissa.
6. the method as described in claim 1 or 5, it is characterised in that the extractant is the mixed solvent of methanol and water, preferably
Ground, the volume ratio of methanol and water is 2 in the extractant：1.
7. the method as described in claim 1 or 5, it is characterised in that the particle diameter of contained nanogold in the nano-Au solution
Scope is 10-50nm；Preferably 10-20nm, more preferably 13nm.
8. the method as described in claim 1 or 5, it is characterised in that cationic polymer is selected from dendroid daiamid, over-expense
Change at least one of PPI, hyperbranched polyethyleneimine, polylysin and chitosan；Preferably, cationic polymer
Selected from dendroid daiamid；It is highly preferred that cationic polymer is selected from the dendroid polyamide in 1 generation, 2 generations, 3 generations and/or 4 generations
Amine.
9. the method as described in claim 1 or 5, it is characterised in that in the Colorimetric System to be measured, the Standard Colorimetric System
In the testing sample solution, the concentration of nanogold is 4.6 × 10-10M to 1.04 × 10-9M；The concentration of cationic polymer
For 0.05-0.3uM.
10. the method as described in claim 1 or 5, it is characterised in that gather extraction phase to be measured with nano-Au solution and cation
Polymer solution mixes, and is specially：First extraction phase to be measured is mixed with nano-Au solution, after mixing, adds cationic polymer
Solution；
Standard liquid is mixed with nano-Au solution and cationic polymer solution, is specially：First by standard liquid and nanogold
Solution mixes, and after mixing, adds cationic polymer solution；
Test solution is mixed with nano-Au solution and cationic polymer solution, is specially：First will test solution and nanogold
Solution mixes, and after mixing, adds cationic polymer solution.
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