CN103439420B - A kind of method identifying edible oil inferior - Google Patents
A kind of method identifying edible oil inferior Download PDFInfo
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- CN103439420B CN103439420B CN201310353934.9A CN201310353934A CN103439420B CN 103439420 B CN103439420 B CN 103439420B CN 201310353934 A CN201310353934 A CN 201310353934A CN 103439420 B CN103439420 B CN 103439420B
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Abstract
The invention discloses a kind of method identifying edible oil inferior, the present invention utilizes HPSEC method to detect the contents level of endogenous macromolecule contaminant in edible oil inferior, GC-MS method is utilized to detect endogenous low carbon number fatty acid in edible oil inferior and exogeneous small molecule pollutant, its testing result comprehensive, judge the quality of edible oil quality, these two kinds of detection methods are supplemented mutually, accurate judgement can be made except to unrefined edible oil inferior and qualified edible oil product, also can identify refining edible oil inferior, for edible oil inspection inferior provides strong technical support.The inventive method is applicable to the detection of the endogenous macromolecule contaminant of lower content in the lower edible oil inferior of degree of oxidation.The inventive method operating process is simple, and instrument and equipment is less demanding, is beneficial to and applies in basic unit.
Description
Technical field
The present invention relates to a kind of method identifying edible oil inferior.
Background technology
Edible oil occupies critical role in China's diet structure, is the main source of body fat acid, is also to provide the important substance of dish color, smell and taste.Positive what is called " bavin, rice, oil, salt, sauce, vinegar, tea " is life, and visible " oil " critical role in people's daily life, therefore the quality of oil is directly connected to the quality of people's lives.But along with the exposure in the media of all kinds of edible oils inferior, (as being detected frying oil arsenic about KFC, McDonald in Taiwan Province in July, 2009, acrylamide content exceeds standard event, " waste oil " event in March, 2010 and in September, 2010 brand tea oil height carcinogen benzopyrene content overproof event etc.), cause the generally worry of people to edible oil safety, even arrive the stage of " talking oil colours to become ".
All kinds of edible oil inferior is broadly divided into following four classes: one is hogwash fat (i.e. waste oil), is by the greasy floating thing in sewer or hotel, the leftovers of restaurant, the oil of leftovers through simply processing, extracting; Two is again by the oil used after frying oil use exceedes certain number of times; Three is lard oils of disease, the meat of dead pig, internal organ and skin; Four is the oil of deterioration in storage.
Edible oil inferior is after the refining process such as separation, filtration, decolouring, moisture evaporation, sterilization, be difficult to itself and common corrected oil to make a distinction from sense organ, traditional organoleptic detection, means such as namely seeing, hear, taste, listen cannot correctly differentiate edible oil inferior.Present stage, main optional following methods differentiated edible oil inferior:
1, thin-layered chromatography.The chief component triglyceride of grease in deterioration process or experience high temperature or to contact with air or light is irradiated, causes its oxicracking to generate a large amount of polar material.Utilize thin-layered chromatography to carry out detection to these polar materials and can distinguish normal edible oil and poor oil, its advantage is easy and simple to handle, and testing cost is low, is applicable to on-site examination.But its detection sensitivity is low, and the polar material in edible oil inferior can be removed in refining process, causes this method to detect refining edible oil inferior and loses efficacy.
2, fatty acid spectrogram statistical method.Normal edible oil has metastable fatty acid composition spectrogram, and poor oil is mixed and disorderly miscella, add putrid and deteriorated cause its fatty acid form spectrogram and normal oils variant, statistics is utilized to set up normal edible oil fatty acid profile storehouse, sample fatty acid profile carries out Auto-matching with spectrum storehouse, thus differentiates whether it is poor oil.Sample collection of illustrative plates Auto-matching can be carried out after setting up in the method spectrum storehouse.But it is not suitable for the detection of blending stock, and need a large amount of dissimilar qualified edible oil collection of illustrative plates to set up spectrum storehouse, workload is huge, also cannot apply at present.
3, based on the quick screening method of nanocomposite optical sensing technology.The method used time is short, easy and simple to handle, and fast sieve cost is low.But the positive charge material self contained due to peanut oil, blending wet goods has a strong impact on the generation of fast sieve result, makes the method not be suitable for the fast sieve of this type of oil; In addition, the extraneous pollutant accidentally introduced easily produces interference to fast sieve result, increases false positive probability; And the positively charged exogenous pollution thing in edible oil inferior is removed in refining process, this method is caused to sieve inefficacy soon to refining edible oil inferior.
4, GC-MS method.Edible oil inferior is in oxidation deterioration process or experience high temperature or to contact with air or light is irradiated, cause its Fatty acid compositions generation acute variation, unsaturated triglyceride generation oxicracking in grease, low carbon number fatty acid (C<14) ratio significantly increases.These low carbon number fatty acid can detect with GC-MS.Meanwhile, some other exogeneous small molecule pollutant also can be detected simultaneously.GC-MS method all can make accurate judgement to unrefined poor oil.But the low carbon number fatty acid in edible oil inferior and other small molecule contaminants are removed in refining process, cause this method to detect refining edible oil inferior and lost efficacy.Consider that the edible oil inferior flowing to dining table is at present generally the edible oil inferior of refining, therefore, unrefined edible oil inferior can not be only limitted to the monitoring target of edible oil, also should carry out the qualification of refining edible oil inferior.
5, efficient spatial exclusion chromatography (HPSEC).Triglyceride because polymerization, cracking cause each deterioration thing molecular weight different, can utilize efficient spatial exclusion chromatography (HPSEC) to be separated it, detect with differential refraction detector in deterioration process.Utilize HPSEC method to the quality control of edible oil, abroad carried out studying quite widely, domesticly in recent years also carry out systematic study.Different according to pre-treating method, HPSEC method is mainly divided three classes: polar compound preenrichment method, and it is highly sensitive, but sample pre-treatments is complicated, non-polar component information dropout; Non-polar component preenrichment method, it is highly sensitive, but sample pre-treatments is complicated, polar compound information dropout; Complete oily sampling system, its object information completely, but detection sensitivity is low, be only applicable to the sample of macromolecule polyalcohol content >3.0%, and research shows, a lot of edible oil inferior due to its degree of oxidation not high, polymer content, lower than 3%, therefore cannot utilize the method to detect.
6, other conventional index detection method, as acid value, peroxide value, conductivity, index of refraction and melting point method, but research finds, all cannot meet the detection needs of poor oil.
Visible, different detection method respectively has relative merits, all cannot meet the detection demand of edible oil inferior at present, in order to ensure the safe reliability of edible oil, urgently explores the method effectively detecting edible oil inferior further.
Summary of the invention
The object of the present invention is to provide a kind of method identifying edible oil inferior.
The technical solution used in the present invention is:
Identify a method for edible oil inferior, comprise the following steps:
1) treat sample oil and carry out HPSEC analysis, adopt complete oily sample introduction, go out the content of polymkeric substance with calculated by peak area, its content >=2.0%, be judged to be edible oil inferior, if < 2.0%, then carry out next step and detect;
2) treat sample oil and carry out GC-MS analysis, the low carbon number fatty acid of C < 14 and the content of external source small molecule contaminants is gone out with calculated by peak area, content >=0.1%, be judged to be edible oil inferior, if < 0.1%, be then judged to be qualified edible oil.
Preferably, in step 1), treat that the pre-treating method of sample oil is as follows: get and treat sample oil 50mg, add 2mL tetrahydrofuran and dissolve, then add appropriate anhydrous sodium sulfate, place 5 ~ 10 min, 0.22 μm of filtering with microporous membrane, completes the pre-treatment of sample oil.
Preferably, the sample size that HPSEC analyzes is 5 μ L.
Preferably, the chromatographic condition that HPSEC analyzes is: chromatographic column is Shodex GPC KF-402HQ, and column temperature is 35 DEG C, and mobile phase is tetrahydrofuran, and flow velocity is 0.2mL/min, and detecting device is differential refraction detector.
Preferably, step 2) in, the GC conditions that GC-MS analyzes is: chromatographic column is HP-5 MS capillary column (30mm × 0.25mm × 0.25 μm), and heating schedule is 80 DEG C and keeps 1min, 20 DEG C/s rises to 180 DEG C, keep 15min, 5 DEG C/s rises to 250 DEG C, keeps 20min, injector temperature 250 DEG C, sample size is 0.3 μ L, and carrier gas is He, and carrier gas flux is 1mL/min; Mass Spectrometry Conditions is: EI ion gun, ion source temperature 230 DEG C, ionization voltage 70ev, interface temperature 230 DEG C, mass range 29 ~ 500m/z.
Preferably, step 2) in, treat that the pre-treating method of sample oil is as follows: get and treat sample oil 50mg, add the Liu Suan – methanol solution that 1.5 ~ 3.0mL concentration is 0.5mol/L, 45 ~ 55 DEG C of water-bath 8 ~ 15min, add 2 ~ 4mL n-hexane extraction, and distilled water washs, then dry through anhydrous sodium sulfate dehydration, complete the pre-treatment of sample.
The invention has the beneficial effects as follows:
The present invention utilizes HPSEC method to detect the contents level of endogenous macromolecule contaminant in edible oil inferior, GC-MS method is utilized to detect endogenous low carbon number fatty acid in edible oil inferior and exogeneous small molecule pollutant, its testing result comprehensive, judge the quality of edible oil quality, these two kinds of detection methods are supplemented mutually, accurate judgement can be made except to unrefined edible oil inferior and qualified edible oil product, also can judge the refining edible oil inferior that current literature procedure and national standard method all cannot judge, for edible oil inspection inferior provides strong technical support.
The present invention adopts complete oily sample introduction, the analysis of micro-HPSEC method, and relative to common HPSEC method, detection sensitivity is higher, is applicable to the detection of the endogenous macromolecule contaminant of lower content in the lower edible oil inferior of degree of oxidation.
The inventive method operating process is simple, and instrument and equipment is less demanding, is beneficial to and applies in basic unit.
Accompanying drawing explanation
Fig. 1 is micro-HPSEC method analysis result in embodiment 1;
Fig. 2 is GC-MS method analysis result in embodiment 1.
Embodiment
By sources edible oil contamination thing inferior can be divided into two large classes: a class is triglyceride autoxidation product, is called contaminating endogenous thing; One class is other pollutant introduced in edible oil and extraneous contact process, is called exogenous pollution thing.
Utilize separately exogenous or endogenous Testing index to carry out detection and there is following problem: (1) comes from the oxidation deterioration of fresh food oil due to contaminating endogenous thing, this deterioration process is being continuous print from fresh qualified edible oil in edible oil process inferior, be difficult in theory to find can absolutely accurate divide both boundary, therefore adopt the detection method of Endogenous index, false positive is difficult to avoid; (2) kind due to edible oil inferior is extremely complicated with source, and any exogenous material enters into edible oil inferior and all there is contingency, does not have a ubiquity, uses exogenous finger object detection method to certainly exist undetected, namely there is false negative.Therefore, the effective ways improving discriminating edible oil accuracy rate inferior should be the detection methods of the multi objective system adopting Endogenous index to combine with exogenous index.
The present invention utilizes HPSEC method (to comprise oxidation triglyceride polymkeric substance and the nonpolar polymkeric substance of triglyceride to endogenous macromolecule contaminant not removable in refining raw food oil process inferior, be referred to as polymkeric substance) contents level detect, GC-MS method is utilized to detect endogenous low carbon number fatty acid and exogeneous small molecule pollutant in thick refining edible oil inferior, its testing result comprehensive, judges that edible oil quality is good and bad.These two kinds of detection methods are supplemented mutually, comprehensively can monitor unrefined edible oil inferior and refining edible oil inferior.
Further, relative to common HPSEC method, micro-HPSEC method detection sensitivity is higher, is applicable to the detection of the endogenous macromolecule contaminant of lower content in the lower edible oil inferior of degree of oxidation.Therefore, the present invention adopts micro-HPSEC to detect.Meanwhile, consider that the integrality of information judges most important for the testing result of edible oil inferior, the present invention utilizes complete oily sampling system to detect endogenous macromolecule contaminant in edible oil inferior.The foundation formulated as edible oil criterion inferior is supported, as edible oil inferior when we judge polyglycerol three ester content >=2.0% according to lot of experimental data.
Below in conjunction with specific embodiment, set forth content of the present invention further, but be not limited to this.
embodiment 1
1, sample oil is treated
Normal edible oil: large supermarket buys certain brand edible oil.
Edible oil inferior: collect from middle-size and small-size restaurant.
Refining edible oil inferior: get edible oil inferior and react 40min, 10min respectively with 85% phosphoric acid and 30% NaOH under 75 DEG C of conditions, add 5 ~ 6% distilled water and stir 3 min, centrifugal 5min under 4000r/min condition, 105 DEG C, 0.1 MPa is evacuated to grease in without emulsification pellucidity; Atlapulgite is added, 110 DEG C of decolouring 30min by oil quality 3%; 250 DEG C, logical nitrogen, 0.1 MPa deodorization 1h, obtain refining edible oil inferior.
2, micro-HPSEC method is analyzed
(1) sample pre-treatments
Take oil sample 50mg to be checked, add 2 mL tetrahydrofurans (THF) and dissolve, add a small amount of anhydrous sodium sulfate, place 5min, with 0.22 μm of filtering with microporous membrane, complete pre-treatment.
(2) chromatographic condition:
Chromatographic column: Shodex GPC KF-402HQ,
Liquid phase pump: Agilent 1260 ultra high efficiency liquid phase pump,
Mobile phase: THF,
Flow velocity: 0.2 mL/min,
Column temperature: 35 DEG C,
Detector temperature: 35 DEG C,
Sample size: 5 μ L.
Respectively normal edible oil, edible oil inferior and refining edible oil inferior are carried out micro-HPSEC method and are detected, result as shown in Figure 1, the detection collection of illustrative plates that wherein, A is normal edible oil, B is unrefined edible oil inferior, C is refining edible oil inferior., according to B, micro-HPSEC method is not high to unrefined edible oil Detection accuracy inferior; But according to C, the triglyceride dimer in edible oil inferior for refining, tripolymer can be separated with triglyceride by the method, thus Stoichiometric Polymerization thing content.The testing result of three kinds of edible oils is respectively: A:0.76%, B:1.96%, C:5.30%.Visible, relative to unrefined edible oil inferior, the micro-HPSEC method Detection accuracy of refining edible oil inferior increases on the contrary, refining process is described on this method testing result not only without impact, can improve its accuracy rate on the contrary, this may be because the pyroprocess in refining causes macromolecule polyalcohol content to increase further.
3, GC-MS analyzes
(1) sample pre-treatments
Get oil sample 50mg to be checked, put in tool plug test tube, add about 2mL Liu Suan – methyl alcohol (0.5mol/L) solution, in 55 DEG C of heating water bath 10min after mixing, add 2mL n-hexane extraction.Draw upper liquid, distill washing twice with 4mL, get upper liquid, dry through anhydrous sodium sulfate dehydration, with 0.22 μm of filtering with microporous membrane, to obtain final product.
(2) GC-MS condition
Instrument: Agilent GC-MS combined instrument (model 7890A-5975C).
GC conditions chromatographic column: HP-5 MS capillary column (30mm × 0.25mm × 0.25 μm); Heating schedule: 80 DEG C keep 1min, and 20 DEG C/Sec rises to 180 DEG C, keeps 15 min, and 5 DEG C/Sec rises to 250 DEG C, keep 20min; Injector temperature: 250 DEG C; Sample size: 0.3 μ L; Carrier gas: He; Carrier gas flux: 1mL/min; Split ratio: 40:1; Molten Ji postpones: 4min.
Mass Spectrometry Conditions: EI ion gun; Ion source temperature 230 DEG C; Ionization voltage 70ev; Interface temperature 230 DEG C; Mass range 29 ~ 500m/z.
Respectively GC-MS analysis is carried out to normal edible oil, edible oil inferior and refining edible oil inferior, result as shown in Figure 2, the GC-MS collection of illustrative plates that A is normal edible oil, B is edible oil inferior, C is refining edible oil inferior, the testing result of three kinds of edible oils is respectively: A:0%, B:0.594%, C:0.039%.According to B, detect through GC-MS, in edible oil inferior, low carbon number fatty acid and exogeneous small molecule compound form many assorted peaks, its content > 0.1%, thus can be judged to be edible oil inferior.According to C, because the low carbon number fatty acid in edible oil inferior and other small molecule contaminants are removed in refining process, cause this method to detect refining edible oil inferior and lost efficacy.
embodiment 2
Adopt multiple determination system, micro-HPSEC/GC-MS joint-detection carried out to the edible oil of variety classes, separate sources:
1) treat sample oil and carry out micro-HPSEC analysis, go out the content of polymkeric substance with calculated by peak area, its content >=2.0%, be judged to be edible oil inferior, if < 2.0%, then carry out next step and detect;
2) treat sample oil and carry out GC-MS analysis, the low carbon number fatty acid of separation of C < 14 and external source small molecule contaminants, with its content of calculated by peak area, content >=0.1%, be judged to be edible oil inferior, if < 0.1%, be then judged to be qualified edible oil.
Trace HPSEC and GC-MS analytical approach is with embodiment 1, and its result is as shown in table 1.
Table 1 multiple determination system is to edible oil testing result
Claims (5)
1. identify a method for edible oil inferior, it is characterized in that, comprise the following steps:
1) treat sample oil and carry out HPSEC analysis, adopt complete oily sample introduction, go out the content of polymkeric substance with calculated by peak area;
2) treat sample oil and carry out GC-MS analysis, go out the low carbon number fatty acid of C < 14 and the content of external source small molecule contaminants with calculated by peak area;
Comprehensive HPSEC and GC-MS testing result, judges that edible oil quality is good and bad;
Step 2) in, the GC conditions that GC-MS analyzes is: the HP-5 MS capillary column of chromatographic column to be specification be 30m × 0.25mm × 0.25 μm, heating schedule is 80 DEG C and keeps 1min, and 20 DEG C/s rises to 180 DEG C, keeps 15min, 5 DEG C/s rises to 250 DEG C, keep 20min, injector temperature 250 DEG C, sample size is 0.3 μ L, carrier gas is He, and carrier gas flux is 1mL/min; Mass Spectrometry Conditions is: EI ion gun, ion source temperature 230 DEG C, ionization voltage 70ev, interface temperature 230 DEG C, mass range 29 ~ 500m/z.
2. the method for qualification according to claim 1 edible oil inferior, it is characterized in that: in step 1), treat that the pre-treating method of sample oil is as follows: get and treat sample oil 50mg, add 2mL tetrahydrofuran to dissolve, add appropriate anhydrous sodium sulfate again, place 5 ~ 10 min, 0.22 μm of filtering with microporous membrane, completes the pre-treatment of sample oil.
3. the method for qualification according to claim 2 edible oil inferior, is characterized in that: the sample size that HPSEC analyzes is 5 μ L.
4. the method for qualification according to claim 2 edible oil inferior, it is characterized in that: the chromatographic condition that HPSEC analyzes is: chromatographic column is Shodex GPC KF-402HQ, and column temperature is 35 DEG C, and mobile phase is tetrahydrofuran, flow velocity is 0.2mL/min, and detecting device is differential refraction detector.
5. the method for qualification according to claim 1 edible oil inferior, it is characterized in that: step 2) in, treat that the pre-treating method of sample oil is as follows: get and treat sample oil 50mg, add the Liu Suan – methanol solution that 1.5 ~ 3.0mL concentration is 0.5mol/L, 45 ~ 55 DEG C of water-bath 8 ~ 15min, add 2 ~ 4mL n-hexane extraction, and distilled water washs, then dry through anhydrous sodium sulfate dehydration, complete the pre-treatment of sample.
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| CN102539551A (en) * | 2010-12-14 | 2012-07-04 | 上海良友（集团）有限公司 | Method for detecting restaurant and kitchen waste oil mixed in edible vegetable oil |
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