CN1309433C - Method for distinguishing agricultural products or food with radiation treatment or not - Google Patents

Abstract

The invention discloses a method for distinguishing irradiated and non-irradiated agricultural products and food. The method comprises the steps of: 1) removing carbonate in the sample to be tested with hydrochloric acid, and removing organic matter in the sample to be tested with H ₂ O ₂ to obtain a mineral having a particle diameter of 3-8 μm for removing carbonate and organic matter. substance; 2) measure the peak area integral value of the thermoluminescence luminescence curve of the mineral matter that removes carbonate and organic matter, expressed in _G1 , and then measure the mineral matter after being irradiated by an irradiation dose of 1kGy The peak area integral value of the thermoluminescent luminescence curve is represented by _G2 ; if the ratio of _G1 to _G2 is greater than or equal to 0.10, the sample to be tested is an irradiated agricultural product or food, such as _G1 and _G2 The ratio of is less than 0.10, then the sample to be tested is an agricultural product or food that has not been irradiated. The method of the invention has the advantages of high sensitivity, simple sample preparation, short detection period, no need for reference objects, high accuracy and the like.

Description

A method of distinguishing between irradiated and non-irradiated agricultural and food products

technical field

The invention relates to a method for distinguishing irradiated and non-irradiated agricultural products and food, in particular to a method for distinguishing irradiated and non-irradiated agricultural products and food by thermoluminescent analysis method.

Background technique

Food irradiation is a new type of food preservation technology that emerged after the Second World War, and it has a history of more than half a century. It uses the physical, chemical and biological effects of ionizing radiation on substances in food storage to achieve the purpose of killing insects, sterilizing bacteria, inhibiting germination, delaying ripening, quarantine control of parasite infection and improving hygiene quality. Since food irradiation has the advantages of energy saving, high efficiency, no temperature rise, safety and reliability, and good sensory quality of food, it is also a supplement and improvement to traditional food processing technology, and it shows an extremely broad prospect in the current food processing and preservation field. prospect. With the rapid development of international trade globalization and irradiated food commercialization, more and more countries and organizations pay more and more attention to whether food has been irradiated (Grolichova M, Dvorak P, Musilova H. Employing Ionizing Radiation to Enhance Food Safety-a Review. Acta Vet. Brno, 2004, 73: 143-149; Lutter R. Food Irradiation--The Neglected Solution to Food-Borne Illness. Science, 1999, 286: 2275-2281; Chen Qixun. Progress in food irradiation in China , Beijing: Atomic Energy Press, 1998: 1-21). Therefore, the research on the detection method of irradiated food is also imperative. This is not only the need for consumers' right to know, but also the need to eliminate technical barriers to international trade and promote the commercialization of irradiated food.

Under the support and organization of the International Atomic Energy Agency, extensive research has been carried out on the detection technology of irradiated food. At present, there are nine methods that can be used to detect irradiated food: electron spin resonance method, high performance liquid chromatography, gas-mass coupling method, thermoluminescence luminescence method, laser imaging detection method, and DNA cleavage product detection method. (J Raffi, M Kent. Method of identification of irradiated foodstuffs, in: L. Nollet (Ed.). Handbook of Food Analysis, Marcel Dekker. New York, 1996: 1889-1906). Most of these methods are based on the physical, chemical, biological and physiological changes in food caused by irradiation. Especially since the late 1980s, Sanderson discovered that the minerals in food are actually the source of thermoluminescence. Since all foods exposed to soil or sandstorms contain mineral residues, theoretically, almost all agricultural products can be thermoluminescent. The superiority and wide applicability of this method are more prominent, and this technology also has the characteristics of no reference object, specific irradiation and high sensitivity. However, with the improvement of people's living standards and the processing capacity of enterprises, the mineral pollution sources of seasoning products are becoming less and less, and the existing extraction technology is difficult to meet the needs of thermoluminescence analysis.

Differentiation of irradiated and non-irradiated food and agricultural products using thermoluminescence analysis begins with the extraction of minerals. Impurities such as organic matter and carbonates included in the extracted minerals will cause "burr" peaks in the thermoluminescence curve, resulting in a larger integral value; plus the response of carbonate crystals in the low-dose and high-dose ranges Different degrees will also bring large errors to the test results. Therefore, the removal of organic matter and carbonate in the experimental materials is a key step in the extraction of minerals, which has a greater impact on the test results.

Contents of the invention

The object of the present invention is to provide a method for distinguishing between irradiated and non-irradiated agricultural products and foods.

The method for distinguishing irradiated and non-irradiated agricultural products and food provided by the present invention comprises the following steps:

1) remove the carbonate in the sample to be tested with hydrochloric acid, use H ₂ O ₂ to remove the organic matter in the sample to be tested, obtain the mineral matter that removes the carbonate and the organic matter;

2) Measure the peak area integral value of the thermoluminescent luminescence curve of the mineral matter that has removed carbonate and organic matter, expressed as _G1 , and then measure the thermal energy of the mineral matter after being irradiated with an irradiation dose of 1kGy. The peak area integral value of the luminescence and luminescence curve, expressed in _G2 ; if the ratio of _G1 to _G2 is greater than or equal to 0.10, the sample to be tested is an irradiated agricultural product or food, such as the ratio of _G1 to _G2 If it is less than 0.10, the sample to be tested is an agricultural product or food that has not been irradiated.

The samples to be tested of the agricultural products can be taken from the surface rinse of the agricultural products, and can also be taken from any part of the agricultural products.

The food sample to be tested can be taken from any part of the food.

The particle size of minerals that remove carbonates and organics will directly affect the inhomogeneity of dose absorption. Too small particles have a strong surface effect, which makes the thermoluminescent signal too strong. Too large particles have too little surface effect, Make the thermoluminescent signal too weak. In order to obtain a thermoluminescent signal with suitable intensity, the method also includes removing the mineral matter obtained in step 1) after obtaining the minerals in step 1) and before the step 2). The mineral matter of carbonate and organic matter carries out the step of flotation as follows: the mineral matter of removing carbonate and organic matter obtained in deionized water suspension step 1), after standing for 5-10 minutes, removes the precipitate, and the supernatant After standing still for 1-2 hours, the supernatant liquid is removed, and the precipitate obtained is minerals with a particle diameter of 3-8 μm and the removal of carbonate and organic matter.

Said hydrochloric acid is a common chemical reagent, and its weight percentage concentration is 36%.

The H ₂ O ₂ is a common chemical reagent with a concentration of 30% by weight.

The peak area integral value of the thermoluminescence luminescence curve is the peak area integral value in the range of 150°C-260°C.

The measurement parameters of the thermoluminescent luminescence curve are: S·A=4.56, D=2, F=2; the heating rate is 15°C per second; the first residence time is 8s, and the temperature is maintained at 135°C; the second residence time is 12s , the temperature was maintained at 350°C.

The present invention combines direct acidification and oxidation with water to directly rinse the surface method to remove carbonates and organics in the sample to be tested, remove organics and carbonates that affect the integral value of the peak area, and greatly reduce the error of the test results. And it does not use expensive sodium tungstate solution to reduce the cost; the invention obtains uniform and pure minerals with a particle diameter of 3-8 μm and removes carbonate and organic matter through flotation, so that the intensity of the thermoluminescence signal is appropriate, making The test repeatability is strong and the result is accurate. The method of the invention has the advantages of high sensitivity, simple sample preparation, short detection period, no need for reference objects, high accuracy and the like. The method of the invention can be used to detect whether the food from which minerals can be separated has been irradiated, and is especially suitable for agricultural products.

Description of drawings

Fig. 1 is the G ₁ /G ₂ statistical diagram of 85 samples.

Fig. 2 is the first thermoluminescence luminescence curve G ₁ of unirradiated Chinese hot pepper.

Fig. 3 is the second thermoluminescent luminescence curve G ₂ of unirradiated Chinese hot pepper flakes.

Fig. 4 is the thermoluminescence first luminescence curve G ₁ of irradiated potatoes.

Fig. 5 is the second thermoluminescence luminescence curve G ₂ of irradiated potatoes.

Detailed ways

The methods described in the following examples are conventional methods unless otherwise specified.

Embodiment 1, the method for distinguishing irradiated food and non-irradiated food

1. Separation and extraction of minerals

RGD-3 thermoluminescence analyzer (Chinese People's Liberation Army Chemical Defense Research Institute); KQ-100 ultrasonic generator (Kunshan Ultrasonic Instrument Co., Ltd.); LD4-2 low-speed centrifuge (Beijing Medical Centrifuge Factory); SG-202 Electric drying oven (Shanghai Shenguang Instrument Co., Ltd.). All reagents used in the experiment were of analytical grade.

Potatoes (purchased in the free market) were divided into two parts, one part (1) was not irradiated, and the other part (2) was irradiated at 0.1 kGy; Chinese spicy slices (Meiquan Food Co., Ltd.) were not irradiated; Soup (Baifen Food Co., Ltd.) was irradiated by 10kGy; barley grass powder (Hengshui Barley Flour Factory) was irradiated by 6kGy; pollen (Honey Bee Research Institute, Chinese Academy of Agricultural Sciences) was irradiated by 4kGy.

1. Mineral separation and extraction of agricultural products with a large amount of mineral soil-potato samples: wash the surface of the potato samples with water, collect the washing liquid in a beaker, and after standing for 24 hours, slowly pour out the supernatant, connect the beaker and the sediment Put them together in a 50-60°C oven for drying. Then, put the dried precipitated sample into a mortar and grind it gently (to prevent the local temperature from being too high), pass through a 200-mesh sieve, and pour the sample under the sieve into a beaker. Due to the complex composition of mineral samples, organic matter and carbonates have a great influence on the thermoluminescence signal, and must be removed by acidification and oxidation. Acidify and oxidize the above-mentioned sample passed through a 200-mesh sieve, and the process is as follows: add 10 ml of deionized water and 10 ml of 36% hydrochloric acid (excessive) to a beaker containing 10 g of the soil sample, stir for 10 min, then add 20 ml of 30% H ₂ O ₂ (excessive) was left to react for 24 hours, then filled with deionized water to fill the cup, poured out the supernatant and added deionized water every 4 hours, and repeated this 4-5 times until the pH of the supernatant was 7. Since the test uses the fine particle method to measure the thermoluminescence, the size of the fine particles will directly affect the unevenness of dose absorption, and the fine particles that are too small have a strong surface effect, which makes the thermoluminescent signal too strong. According to Stokes law, the flotation fine particle diameter is 3-8um. Therefore, flotation is carried out. The flotation process is: add deionized water to the soil sample that has been acidified and oxidized to remove organic matter and carbonate to fill the cup, shake it well, and let it stand for 10 minutes. The particles larger than 8um have settled to the bottom of the cup. Pour the supernatant into another beaker and let it stand for 1 hour. Then pour out the supernatant, and the sediment at the bottom of the beaker is fine particles with a diameter of 3-8um. Finally, transfer it to a small beaker with acetone (analytically pure), let it stand for precipitation, discard the acetone solution, put the precipitated minerals together with the small beaker in an oven at 50-60°C for drying, weigh 5 mg and put it into the sample tube. To be measured by thermoluminescence.

2. Mineral separation and extraction of spices and dehydrated vegetable samples: take 100g of spicy slices, seafood soup, barley grass powder, and pollen samples, and directly acidify and oxidize them according to the following method: add 50ml of 36% hydrochloric acid (excessive), After stirring for 10 minutes, add 100ml of 30% H ₂ O ₂ (excessive amount), and use 30KHz ultrasonic treatment, then let it settle for 4 hours, discard the organic matter in the upper layer and centrifuge, discard the supernatant, and collect the precipitate. Flotate the sediment by the method of step 1 flotation. A 5 mg mineral sample was obtained, to be measured by thermoluminescence analysis.

2. Thermoluminescence Luminescence Curve Measurement

Pour the sample mineral extract obtained in step 1 into the thermoluminescence measuring small dish evenly, and turn on the RGD-3 thermoluminescence analyzer. The measurement parameters of the instrument are selected as: S·A=4.56, D=2, F=2; the heating rate is 15°C per second; the first residence time is 8s, and the temperature is maintained at 135°C; the second residence time is 12s, and the temperature is maintained at 350°C . The luminescence peak takes the peak area integral value in the range of 150°C-260°C. The measured luminescence curve is the first luminescence curve, and G ₁ is used to represent the integrated value of the peak area. Then all the samples that had measured _G1 were collected into the sample tube for irradiation. The irradiation device used the Institute of Atomic Energy Utilization, Chinese Academy of Agricultural Sciences ⁶⁰ Coγ irradiation source, the dose was 1kGy, and the dosimeter was a silver dichromate dosimeter. Then, the second thermoluminescence measurement is carried out under the same conditions, and the obtained luminescence curve is the second luminescence curve, and the integrated value of the peak area is represented by _G2 . The thermoluminescent analysis data of the sample are shown in Table 1:

Table 1 Thermoluminescent analysis data table of different samples to be tested sample one measurement secondary measurement G ₁ /G ₂ Irradiation G _{1 G2} potatoes (1) 354500 7185700 0.049 unirradiated potatoes (2) 1146100 5696300 0.200 photographed Medium spicy slices 419000 10048400 0.040 unirradiated seafood soup 1329100 1041100 1.280 photographed Barley Grass Powder 583800 720800 0.800 photographed pollen 1376400 2769500 0.500 photographed

The results show that: compared with the unirradiated sample, the data difference of the peak area integral value ratio (G ₁ /G ₂ ) of the luminescence curve is obvious, and the G ₁ /G ₂ of the two unirradiated samples are far less than 0.10, while the G ₁ /G ₂ of the four irradiated samples are all greater than 0.10. With reference to the actual dose of food irradiation at home and abroad, and according to the detection accuracy of the measuring instrument itself, it is set that any food with an irradiation dose above 0.10kGy (including 0.10kGy) is considered as irradiated food; if the food itself Or if one of the excipients received radiation dose less than 0.10kGy, it is considered that the food has not received radiation. Therefore, when the minerals extracted from the sample receive an irradiation dose of 1 kGy, if the ratio G ₁ /G ₂ of the peak area integral value of the luminescence curve is less than 0.10, it is determined that the food has not received irradiation, and the smaller the ratio, the higher the dose received. The less likely it is; if G ₁ /G ₂ is greater than or equal to 0.10, it is determined that the sample has been irradiated, and the larger the ratio, the higher the received dose.

The thermoluminescence first and second luminescence curves of unirradiated spicy slices are shown in Fig. 2 and Fig. 3 . The peak area products of the first and second luminescence curves between 150°C and 260°C are 419000 (G ₁ ) and 10048400 (G ₂ ), respectively, G ₁ /G ₂ =0.040; and the curve shapes of the two are relatively obvious It can be judged that this sample has not been irradiated, which is consistent with the actual situation. The thermoluminescence first and second luminescence curves of the irradiated potato (2) sample are shown in Fig. 4 and Fig. 5 . According to the experimental operating conditions, the peak area products of the first and second luminescence curves between 150°C and 260°C are 1,146,100 (G ₁ ) and 5,696,300 (G ₂ ), G ₁ /G ₂ =0.20; The shapes of the curves are relatively similar, and it can be determined that the potatoes are irradiated samples, which is consistent with the actual situation. From the comparison of the two groups of figures, it can be seen that there are many "burrs" on the first luminescence curve of the sample, while the second luminescence curve remains basically smooth. The appearance of burrs is closely related to the purity of the extracted minerals in the sample. The more impurities (mainly organic matter and carbonate) contained in the extracted minerals, the greater the possibility of burrs. In the first stage, minerals can ash most of the impurities at a high temperature of more than 200 degrees, and then irradiate a certain dose, and the obtained second luminescence curve is basically smooth; but under the condition of less than 150 degrees, as the temperature gradually There will be a low-temperature peak when the temperature rises, which is the result that the shallower electrons escape first after the sample is irradiated with a certain dose.

Therefore, in order to prove the accuracy and effectiveness of the detection criterion, 85 samples of solid and liquid food, as well as dry and fresh fruits and vegetables were selected from the 6 categories of food that are allowed to be irradiated according to the national regulations. The described method extracts mineral matter, has carried out thermoluminescent detection and analysis, and wherein 45 samples accept the irradiation dosage that actual technology needs, and the result is shown in Figure 1, shows that after 45 irradiated samples are detected by thermoluminescence analyzer , the ratios of G ₁ /G ₂ were all greater than 0.1, and the correct rate of discrimination was 100%; after identification of 40 unirradiated samples, the ratios of G ₁ /G ₂ of 38 unirradiated samples were all less than 0.1, and 2 The ratios of G ₁ /G ₂ of the unirradiated samples were all equal to 0.1, and the correct rate of discrimination was 95%. Finally, a qualitative judgment basis is obtained through statistics: that is, when G ₁ /G ₂ ≥ 0.10, it is determined that the sample has been irradiated, and the larger the ratio, the greater the radiation dose received; while G ₁ /G ₂ <0.10 When , it is judged that the sample is not irradiated, and the smaller the ratio, the less likely it is to be irradiated.

Claims (6)

1. A method for distinguishing irradiated and non-irradiated agricultural products and food, comprising the following steps: 1) remove the carbonate in the sample to be tested with hydrochloric acid, and remove the organic matter in the sample to be tested with H ₂ O ₂ to obtain minerals with a particle diameter of 3-8 μm for removing carbonate and organic matter; 2) Measure the peak area integral value of the thermoluminescent luminescence curve of the mineral matter that has removed carbonate and organic matter, expressed as _G1 , and then measure the thermal energy of the mineral matter after being irradiated with an irradiation dose of 1kGy. The peak area integral value of the luminescence and luminescence curve, expressed in _G2 ; if the ratio of _G1 to _G2 is greater than or equal to 0.10, the sample to be tested is an irradiated agricultural product or food, such as the ratio of _G1 to _G2 If it is less than 0.10, the sample to be tested is an agricultural product or food that has not been irradiated. 2. The method according to claim 1, characterized in that: the method for preparing minerals with a particle diameter of 3-8 μm and removing carbonates and organic matter comprises the following flotation step: suspending with deionized water 1) The mineral matter that removes carbonate and organic matter obtained in 1), after standing for 5-10 minutes, remove the precipitation, after the supernatant liquid was left standstill for 1-2 hours, remove the supernatant liquid, the precipitation obtained is that the particle diameter is 3- 8 μm of minerals to remove carbonates and organic matter. 3. The method according to claim 1 or 2, characterized in that the concentration of the hydrochloric acid is 36% by weight. 4. The method according to claim 1 or 2, characterized in that the concentration of H ₂ O ₂ by weight is 30%. 5. The method according to claim 1 or 2, characterized in that: the integral peak area value of the thermoluminescence luminescence curve is the integral peak area value in the range of 150°C-260°C. 6. The method according to claim 1 or 2, characterized in that: the measurement parameters of the thermoluminescence luminescence curve are selected as: S·A=4.56, D=2, F=2; the heating rate is 15°C per second ; The first residence time is 8s, and the temperature is maintained at 135°C; the second residence time is 12s, and the temperature is maintained at 350°C.

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