CN103776947A - Method for detecting malondialdehyde in food - Google Patents

Abstract

The invention provides a method for detecting malondialdehyde in food, in particular to a method for determining and analyzing the malondialdehyde in food by virtue of a high-efficiency liquid-phase chromatogram fluorescent detector detection way. By virtue of the obtained liquid-phase chromatogram, the content of malondialdehyde in the food can be detected on the basis of a peak reservation time and a peak area. By adopting the method, the content of the malondialdehyde in the food can be accurately controlled.

Description

A kind of detection method of malondialdehyde in food

Technical field

The invention relates to a detection technology for malondialdehyde in food, in particular to the separation and detection of malondialdehyde in food by high performance liquid chromatography.

Background technique

The fat in food has important nutritional value. It not only provides body calories and essential fatty acids needed by the human body, but also serves as a carrier for fat-soluble vitamins such as VA to facilitate their absorption, and can effectively improve the flavor and texture of food. Foods with high oil content, during processing and storage, produce unpleasant smell, bitter taste and some toxic compounds due to the action of oxygen in the air, light, microorganisms, enzymes, etc. Rancidity, commonly known as hard change. Grease rancidity can not only change the flavor of oil-containing foods, affect the nutritional value of oil-containing foods, but also have a certain impact on human health, and some products also have carcinogenic effects. Oxidation of oil will cause the deterioration and taste of fat in food, which will bring harm to food quality, nutritional value and safety in many aspects. First of all, the nutritional value of food is reduced, and the self-oxidation of food will destroy the fat-soluble vitamins and essential fatty acids in food, thus reducing the nutritional value of food; secondly, the self-oxidation of food will produce toxic metabolites.

Rancid fats contain a large amount of decomposition products lipid peroxide. Food poisoning caused by eating rancid fats or foods containing rancid fats (such as cakes, biscuits, instant noodles, etc.), the incubation period is generally 1-5 hours, and a few are 24 hours above. The characteristics of poisoning are sudden onset, rapid onset, nausea at first, followed by vomiting, diarrhea, abdominal pain, headache, fever and other symptoms. The oxidative decomposition products of food itself are toxic aldehydes and ketones, and aldehydes and ketones have adverse effects on the health and production capacity of livestock and poultry. Studies have shown that the polymers produced by oil oxidation cannot be absorbed and utilized by animals, resulting in toxic reactions and diarrhea; certain oxidation products can cause animal liver enlargement, reduce feed intake, and lower digestibility; Epithelial damage will directly lead to the decline of animal reproductive ability. The aldehydes produced by the rancid fat in the feed directly damage the hepatopancreas of fish and affect the normal liver function; irregular swimming, exophthalmos, enlarged gallbladder, light or turbid liver, and liver tissue can be observed in diseased fish. Large pieces of lytic necrosis, fibrosis, vacuolation, etc. Poultry eating feed containing lipid peroxide can cause yellow lipid disease, and cats can cause liver, heart, and kidney hypertrophy after eating, leading to liver degeneration or fatty liver. If mice are fed with fats containing alkenal hydroperoxide, the product of secondary oxidation of fats, the mice will die within 24 hours.

At present in my country, the physical and chemical indicators for evaluating whether oil-containing foods meet the national safety and health standards are peroxide value and acid value. The peroxide value mainly reflects whether oxidative hydrolysis rancidity has occurred in oil-containing foods. (milligram equivalent/kg) means rancidity; and acid value indicates the degree of rancidity of oil. The current national standard regards peroxide value and acid value as the main indicators for judging whether oil-containing foods are rancid, but in fact the above two indicators cannot really reflect whether oil-containing foods have become rancid. This is because the increase in peroxide value is an early indicator of oil rancidity. When the oil becomes rancid to a certain extent and the peroxide is further decomposed into aldehydes and ketones, the peroxide value will decrease again, but in fact the oil has deteriorated seriously; most It is inevitable that a small amount of free fatty acids exist in oils and fats, so the acid value of edible oils is rarely zero. It is not accurate to use peroxide value and acid value as indicators to evaluate whether oily foods are rancid. Malondialdehyde (MalondiaLdehyde, MDA) is a lipid peroxide generated during the oxidative rancidity of oils and fats. In the presence of peroxide decomposition factors such as heat, light, and heavy metals, it is further decomposed into an aldehyde. Important end-product of oxidative rancidity. With the deepening of oil oxidative rancidity, the content of malondialdehyde increased significantly compared with the peroxide value and acid value. Therefore, the index of malondialdehyde has the characteristics of sensitivity and good stability, and is the most sensitive index for objectively evaluating the rancidity of food oils.

At present, the determination methods of malondialdehyde include capillary electrophoresis, high performance liquid chromatography, fluorescence method and colorimetry. Capillary electrophoresis and high performance liquid chromatography are not popular at this stage due to expensive instruments, and colorimetry is cumbersome and time-consuming in sample processing. At present, the conventional TBA (thiobarbituric acid) value determination method is still widely used in China. The TBA value determination method refers to the color reaction between malondialdehyde, the main oxidation end product of fat, and thiobarbituric acid. , and has a characteristic absorption at 532nm, using the linear relationship between the absorption intensity and the concentration of malondialdehyde within a certain range, it can be used to measure the degree of fat oxidation, and it is a direct indicator reflecting the degree of oxidative deterioration of oil-containing products during storage , is also an important indicator reflecting the safety of fatty foods. This method is convenient and easy to operate. At present, there is a national standard "Determination of Malondialdehyde in Lard" which adopts the conventional TBA value determination method. However, the MDA content level determined by the conventional TBA value method is relatively high, which can be determined by improving the TBA value determination method, using high-performance liquid chromatography, and using a fluorescence detector.

MDA content level is an important index to evaluate the oxidation degree of food oil. As the final product of food oil oxidation, the determination of malondialdehyde content can more accurately reflect the actual oxidation degree of food. Moreover, malondialdehyde itself has certain hazards, is mutagenic to Salmonella, and is a carcinogenic promoter. So far, my country has not established corresponding national standards or industry standards for the determination of malondialdehyde content in food. Through the study of this technical standard, a more accurate measurement method can be provided for the evaluation of food oxidative rancidity, and technical support can be provided for food quality and safety monitoring.

Contents of the invention

The purpose of the present invention is to provide a fast and accurate detection method for malondialdehyde in food, aiming at the problem that it is difficult to detect rancidity and oxidation of high-fat food at present.

In order to realize the above-mentioned invention object, the present invention adopts following technical scheme: a kind of rapid detection method of malondialdehyde in detection food, it is characterized in that chromatographic column is C18 separation column (long 250mm, internal diameter 4.6mm, particle diameter 5 μ m), column temperature The temperature is 35°C, the mobile phase is acetonitrile+potassium dihydrogen phosphate solution=18+82(V+V), the flow rate is 1.0mL/min, and the fluorescence detector has an excitation wavelength of 525nm and an emission wavelength of 560nm. It was extracted with trichloroacetic acid mixture, and then derivatized with malondialdehyde and TBA solution. On-machine analysis, the retention time of the obtained peak is compared with the standard spectrum, and the content of malondialdehyde can be known by substituting the obtained peak area into the standard curve.

Compared with other high performance liquid chromatography detection methods, the present invention uses a fluorescence detector to detect the compound generated by MDA and TBA, which greatly improves the detection limit of MDA and solves the detection interference of MDA Serious technical difficulty makes the content of malondialdehyde in the food be measured accurately, and these special features of the present invention are not reported in domestic and foreign documents.

The present invention compares with the result that other efficient chromatography detects malondialdehyde content:

Detection object: the present invention detects malondialdehyde in food.

Detection range: the present invention is mainly applied to high-fat foods such as oils, cakes, dry-cured fish and meat products, walnuts, and peanuts.

Description of drawings

Fig. 1 is the high-performance liquid chromatogram of malondialdehyde standard substance.

Detailed ways

Take supermarket cured meat and walnut samples, and analyze and detect them according to the following operation procedures.

Weigh about 2g of sample, put it into a 250mL Erlenmeyer flask, accurately add 50mL of trichloroacetic acid mixture, shake at 180r/min for 30min, take about 20mL of extract in a 50mL centrifuge tube, and centrifuge at 5000r/min for 5min. Pipette 5 mL each of the above sample solution supernatant and malondialdehyde standard series solution into a 25.0 mL colorimetric tube, add 5.0 mL TBA solution, mix well, place in a 90°C water bath for 20 minutes, take it out, and place it in an ice water bath Cool rapidly, transfer to a centrifuge test tube, centrifuge at 12000r/min for 5min, take the supernatant and measure it on the computer, derivatize the standard series of malondialdehyde and the sample synchronously, and analyze it on the computer.

The method has good linearity and precision in the range of 0.02μg/mL-0.20μg/ml.

Claims (2)

1. the detection method of MDA in a food, it is characterized in that: the method comprises the following steps, chromatographic column is that (particle diameter 5 μ m) for long 250mm, internal diameter 4.6mm for C18 separating column, column temperature is 35 ℃, mobile phase is acetonitrile+potassium dihydrogen phosphate=18+82 (V+V), and flow velocity is 1.0mL/min, fluorescence detector, its excitation wavelength is 525nm, and emission wavelength is 560nm.Utilize trichloroacetic acid mixed liquor to extract, then by MDA and TBA solution derivatization.Take about 2g sample, accurately add 50mL trichloroacetic acid mixed liquor, 180r/min jolting 30min, gets about 20mL extract in 50mL centrifuge tube, the centrifugal 5min of 5000r/min.Pipette said sample solution supernatant, the each 5mL of MDA standard serial solution is placed in respectively in 25.0mL color comparison tube, add 5.0mL TBA solution, mix, be placed in 90 ℃ of water-baths and be incubated 20min, take out, cooling rapidly with ice-water bath, in immigration centrifuge tube, the centrifugal 5min of 12000r/min, the machine on supernatant of getting is measured, the synchronous derivatization of MDA standard series and sample, upper machine analysis.

2. the detection method of MDA in food according to claim 1, is characterized in that: utilize trichloroacetic acid mixed liquor to extract, then by MDA and TBA solution derivatization, recycling fluorescence detector detects.High performance liquid chromatography is that waters company produces, and pillar adopts the Atlantis T of Waters company ₃post, detection system is fluorescence detector system, and its excitation wavelength is 525nm, and emission wavelength is 560nm.The mobile phase using in testing process is acetonitrile and 50mmol/L potassium dihydrogen phosphate solution, and its ratio is deionized water: sodium hydroxide solution=18: 82.High fatty foods to be detected only needs ultrasonic extraction, dilution, filtration can go up machine testing, without the extraction processing of sample being carried out to organic solvent.

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