Method for testing greased or mineral-oiled foodstuffs and use thereof
By using polypropylene oil-absorbing blue film and specific heat treatment, the problem of distinguishing between oil spots and water spots in traditional methods has been solved, achieving low-cost, low-false-rate qualitative detection of coated grease or mineral oil grains, with a detection limit of 0.04%.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-04-10
- Publication Date
- 2026-03-20
AI Technical Summary
There is a lack of accurate and effective quantitative methods for detecting coated oils or mineral oils in grains. Traditional testing methods are difficult to distinguish between oil stains and water stains due to the absorption of moisture by oil-absorbing paper products, resulting in high detection limits and high false positive rates.
Polypropylene oil-absorbing blue film was used to replace traditional oil-absorbing paper. Through heat treatment, it was made to absorb only oil and not moisture. Combined with specific heating conditions and multiple sampling judgments, oil spots were accurately displayed, and the detection limit was reduced to 0.04%.
It enables low-cost and simple-to-operate qualitative detection of coated grease or mineral oil grains, reduces the false judgment rate, and achieves a detection limit of 0.04%, making it suitable for a wide range of applications.
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Abstract
Description
TECHNICAL FIELD
[0001] The present application relates to the field of agricultural product quality and safety. More particularly, it relates to a method for testing grain coated with oil or mineral oil and its application. BACKGROUND
[0002] At present, the detection of coated grain mainly focuses on the analysis of mineral oil-coated rice at home and abroad. The methods include saponification, thin layer chromatography, gas chromatography, gas chromatography-tandem mass spectrometry, gas chromatography-liquid chromatography and near infrared spectroscopy. The standard GB / T 21309-2007 "Coated oil or paraffin rice test" in China only has a qualitative method, and there is no accurate and effective quantitative method. The qualitative detection method uses newspaper as experimental material, but during the heating process, the oil or paraffin of the coated rice seeps out with the evaporation of water vapor inside the rice. The newspaper absorbs water as well as oil and paraffin, affecting the identification of oil spots, and the detection limit is 0.08%. There are reports that a handful of rice is wrapped with oil absorption paper, then gently kneaded, and finally the oil stain residue on the oil absorption paper is observed. The household oil absorption paper on the market is mainly made of silicone oil and non-woven fabric, and the transparency of the paper surface is inconsistent, which makes it difficult to judge. The test limit is more than 0.2%, and the effect is not good. SUMMARY
[0003] Based on the above problems, one object of the present application is to provide a method for testing grain coated with oil or mineral oil. The test method can qualitatively test whether the test grain is coated with oil or mineral oil and other illegal added non-food substances, overcome the problem of difficult differentiation between water and oil spots caused by different absorption of water by oil absorption paper in traditional test methods, reduce misjudgment, and the detection limit of the test method can reach 0.04%. At the same time, the test method also has the advantages of low cost, simple operation and strong practicability.
[0004] Another object of the present application is to provide an application of the test method described above in the qualitative test of grain coated with oil or mineral oil.
[0005] In the present application, grain coated with oil or mineral oil and other chemical illegal additives on the outer surface is defined as coated grain. The coating treatment can improve the sensory properties of old grain, making it more glossy in appearance, so as to cover up the original features of old grain such as dull color, and achieve the purpose of using inferior goods as good ones and confusing real with fake. The present application is a method for qualitatively testing such coated grain.
[0006] To achieve the first object, the present application adopts the following technical solution:
[0007] The present application discloses a method for testing grain coated with oil or mineral oil, comprising the following steps:
[0008] S1, take n oil absorption blue films on the object plate, then take n samples from the grain to be tested in parallel and place them on the oil absorption blue film respectively;
[0009] S2, fold each oil absorption blue film, so that the grain to be tested is completely laid and wrapped in the oil absorption blue film;
[0010] S3, the oil absorption blue film wrapped with the grain to be tested is heated, and after the heating is completed, the grain to be tested wrapped in the oil absorption blue film is poured out, and the oil spot on the oil absorption blue film is observed;
[0011] Wherein, n is a positive integer.
[0012] The application creatively uses commercially available oil absorption blue film, especially polypropylene oil absorption blue film, for the detection of oil or mineral oil coated grain. The oil absorption blue film can replace the oil absorption paper products (such as newsprint, printing paper, letter paper, baking and barbecue silicon oil paper or pp non-woven oil absorption cloth) used in traditional inspection methods. Because the background color of the oil absorption blue film is blue, the oil spot is obvious. And the traditional oil absorption paper product may absorb both water and oil, which makes it difficult to distinguish the spots on the oil absorption paper product in the inspection method. The oil absorption blue film of the application only absorbs oil and does not absorb water, which can eliminate the problem of distinguishing water spots and oil spots, so that researchers can make correct judgments. Further research by the inventor found that by controlling the heating conditions, the detection limit of the oil absorption blue film can be controlled at 0.04%, which is significantly lower than that of traditional oil absorption paper products. Therefore, it is expected to be widely used in qualitative inspection of oil or mineral oil coated grain.
[0013] Further, to prevent accidental errors and facilitate the evaluation of technicians, the skilled person in the art can independently select n as an odd number greater than or equal to 3.
[0014] Further, the inspection method further comprises determining the oil spot condition:
[0015] If the number of oil absorption blue films with oil spots is 0, the result is negative;
[0016] If the number of oil absorption blue films with oil spots is greater than 0 and less than n / 2, repeat steps S1-S3. If the number of oil absorption blue films with oil spots is still less than n / 2, the result is negative, indicating that the grain to be tested is not oil or mineral oil coated grain;
[0017] If the number of oil absorption blue films with oil spots is greater than n / 2, the result is positive, indicating that the grain to be tested is oil or mineral oil coated grain.
[0018] Exemplarily, when n is 3, the oil spot condition in the test method is determined, if the number of the oil-absorbing blue film with oil spots is 0, the result can be directly determined as negative, indicating that the tested grain is not the grain coated with oil or mineral oil; if the number of the oil-absorbing blue film with oil spots is 1, steps S1-S3 are repeated, if the number of the oil-absorbing blue film with oil spots is 0 or 1 after repeated experiments, the result is determined as negative, indicating that the tested grain is not the grain coated with oil or mineral oil; if the number of the oil-absorbing blue film with oil spots is 2 or 3, the result is determined as positive, indicating that the tested grain is the grain coated with oil or mineral oil.
[0019] Further, the oil-absorbing blue film is selected from a polypropylene oil-absorbing blue film.
[0020] Further, the oil includes but is not limited to vegetable oil; exemplarily, the vegetable oil includes but is not limited to one or more of rice bran oil, soybean oil and peanut oil.
[0021] Further, the mineral oil is selected from saturated hydrocarbons and aromatic hydrocarbons with carbon atom number of 10-50, in experiments, commercially available mineral oil can be directly selected, or commercially available liquid paraffin (hydrocarbon mixture with carbon atom number of about 16-30) obtained by deep chemical refining of mineral oil can be selected, and the conclusions obtained by the test method are not different.
[0022] Further, the grain includes one or more of rice, soybean, mung bean, red bean, pea and black bean.
[0023] Further, the heating temperature is 55℃±5℃, and the heating time is 15min-90min; preferably, the heating temperature is 55℃±2℃, and the heating time is 60min, which can make the detection limit of the oil-absorbing blue film lower, and can also greatly shorten the detection time.
[0024] Further, the detection limit of the test method is 0.04%.
[0025] Further, in order to make the tested grain closely adhere to the oil-absorbing blue film, a cover plate can be placed on the oil-absorbing blue film; the material of the cover plate and the carrier plate can be glass, and the carrier plate and the cover plate need to be clean and dry; those skilled in the art can understand that the outer peripheral size of the carrier plate and the cover plate should be larger than the outer peripheral size of the oil-absorbing blue film, so as to ensure that the oil-absorbing blue film can be completely placed in the carrier plate and the cover plate.
[0026] To achieve the above-mentioned second object, the application adopts the following technical scheme:
[0027] The application discloses an application of the test method in qualitative testing of grain coated with oil or mineral oil.
[0028] The beneficial effects of the present application are as follows:
[0029] The present application provides a test method for greased or mineral oil food, which has the following advantages:
[0030] 1. A low-cost oil-absorbing blue film, especially a polypropylene oil-absorbing blue film, is selected as a new experimental material. The oil-absorbing blue film only absorbs oil and does not absorb water, eliminating the problem of water vapor exuding and remaining on the experimental material, which affects the correct judgment of researchers.
[0031] 2. The oil-absorbing blue film has a blue background color, and the oil spot appears more clearly, with a lower detection limit of 0.04%.
[0032] 3. The test method is simple to operate and has strong practicality.
[0033] 4. The test method is expected to be widely used in qualitative testing of greased or mineral oil food. BRIEF DESCRIPTION OF DRAWINGS
[0034] Figure 1 The detection experiment physical map of embodiment 1 of the present application is shown.
[0035] Figure 2 The detection experiment physical map of embodiment 2 of the present application is shown.
[0036] Figure 3 The detection experiment physical map of embodiment 3 of the present application is shown.
[0037] Figures 4-1 to 4-5 The verification report of the blind sample inspection is shown.
[0038] Figure 5 The detection experiment physical map of embodiment 4 of the present application is shown. DETAILED DESCRIPTION
[0039] In order to more clearly illustrate the present application, the present application will be further described below in combination with preferred embodiments and drawings. Those skilled in the art should understand that the specific description below is illustrative rather than limiting, and should not limit the protection scope of the present application.
[0040] The technical solutions of the present application will be described below in combination with some specific embodiments, wherein the experimental materials used in the embodiments include:
[0041] The polypropylene oil-absorbing blue film is purchased from Jingdong, with the brand of Kelingke Li and the importer being Johnson & Johnson (China) Co., Ltd.
[0042] The newsprint is purchased from Taobao, with the manufacturer being Linyi Sunshine Paper Co.
[0043] The printing paper is purchased from Taobao, with the brand of Jia Yin and the manufacturer being Fen Ouhui Chuan (China) Co., Ltd.
[0044] The pp non-woven oil-absorbing cloth is purchased from Taobao, and the manufacturer is Hangzhou Jiuxutian Technology Co., Ltd.
[0045] The letter paper is obtained from the stock letter paper of the National Food and Material Reserve Bureau Scientific Research Institute;
[0046] The baking and roasting silicone oil paper is purchased from Taobao, the brand is Fabaoge, and the manufacturer is Linyi Youji Baking Products Co., Ltd.
[0047] The following is the coating process of the present application in the preparation of coated grain:
[0048] 0.04 g of oil or mineral oil is weighed and placed in a ziplock bag, and the oil or mineral oil is spread evenly on the inside of the ziplock bag. 100 g of grain weighed in the ziplock bag is manually shaken for 3 min, and then shaken for 8 h by a mixing machine to obtain 0.04% coated oil or mineral oil grain.
[0049] 0.12 g of oil or mineral oil is weighed and placed in a ziplock bag, and the oil or mineral oil is spread evenly on the inside of the ziplock bag. 100 g of grain weighed in the ziplock bag is manually shaken for 3 min, and then shaken for 8 h by a mixing machine to obtain 0.12% coated oil or mineral oil grain.
[0050] 0.2 g of oil or mineral oil is weighed and placed in a ziplock bag, and the oil or mineral oil is spread evenly on the inside of the ziplock bag. 100 g of grain weighed in the ziplock bag is manually shaken for 3 min, and then shaken for 8 h by a mixing machine to obtain 0.2% coated oil or mineral oil grain.
[0051] In the present application, the oil selected in the examples is rice bran oil or soybean oil, the mineral oil selected is commercially available mineral oil or commercially available liquid paraffin, and the grain selected is rice or mung bean.
[0052] Example 1
[0053] Select commercially available different oil-absorbing paper products as experimental materials to test, and take 0.2% coated oil rice as the test rice to observe the oil spot of various oil-absorbing paper products. The following test method takes polypropylene oil-absorbing blue film as an example for description, and other oil-absorbing paper products (such as newsprint, printing paper, pp non-woven oil-absorbing cloth, baking and roasting silicone oil paper, letter paper) can be tested by replacing the polypropylene oil-absorbing blue film according to the test steps. The test method comprises the following steps:
[0054] S1, take three polypropylene oil-absorbing blue films and place them on a clean and dry glass plate, then take three parallel samples from the test rice, each weighing 1 g, and evenly spread them on the three polypropylene oil-absorbing blue films;
[0055] S2, fold the three polypropylene oil absorption blue films, so that the to-be-tested rice is completely wrapped in the polypropylene oil absorption blue films, and then press the cover with another glass plate;
[0056] S3, transfer the polypropylene oil absorption blue film wrapped with the to-be-tested rice to a constant temperature drying box, heat at 55℃±2℃ for 60min, take out after the end, pour out the to-be-tested rice wrapped in the polypropylene oil absorption blue film, and observe the oil spot on the polypropylene oil absorption blue film;
[0057] The oil spot of different oil absorption paper products is shown in Table 1, and the actual figure of the obtained oil spot is shown in Figure 1 .
[0058] Table 1
[0059]
[0060] It can be found from Table 1 and Figure 1 that only the polypropylene oil absorption blue film provided by the application has a relatively clear and accurate oil spot appearance among the commercially available oil absorption paper products; the newsprint, printing paper and letter paper will also absorb water when absorbing oil, so that the spots appearing cannot be determined whether they are oil spots or water spots; the baking and barbecue silicone oil paper is affected by the material, and the transparency is different, Figure 1 only the circled part can accurately spread the oil spot, but the resolution is low, which increases the detection limit; the pp non-woven oil absorption cloth will only present an oil spot, but the spot is very light and the resolution is very low.
[0061] Example 2
[0062] Select polypropylene oil absorption blue film as experimental material, 0.04% greasy or liquid paraffin rice as to-be-tested rice, and respectively investigate the oil spot appearance under different heating times (15min, 30min, 45min, 60min and 90min), the steps are as follows:
[0063] S1, take three polypropylene oil absorption blue films and place them on a clean and dry glass plate, then take three parallel samples from the to-be-tested rice, each taking 1g, and evenly lay them on the three polypropylene oil absorption blue films after sampling;
[0064] S2, fold the three polypropylene oil absorption blue films, so that the to-be-tested rice is completely wrapped in the polypropylene oil absorption blue films, and then press the cover with another glass plate;
[0065] S3, transfer the polypropylene oil absorption blue film wrapped with the to-be-tested rice to a constant temperature drying box, heat at 55℃±2℃, the heating time is adjusted according to the investigation parameters, take out after the end of heating, pour out the to-be-tested rice wrapped in the polypropylene oil absorption blue film, and observe the oil spot on the polypropylene oil absorption blue film.
[0066] The results are shown in Table 2 and Figure 2 After screening the heating time, it is found that when the heating temperature is 55℃±2℃, and the heating time is more than 60min, the test method of the application can clearly and accurately detect the oil spots, and the oil spots are obvious.
[0067] Table 2
[0068]
[0069] Example 3
[0070] The polypropylene oil absorption blue film was selected as the experimental material, and the rice coated with different amounts of oil, liquid paraffin or mineral oil (coating amount: 0%, 0.04%, 0.12% and 0.2%) was used as the to-be-tested rice to investigate the oil spot situation under different coating amounts, and the steps were as follows:
[0071] S1, three polypropylene oil absorption blue films were placed on a clean and dry glass plate, and then three parallel samples were taken from the to-be-tested rice, each taking 1g, and the samples were evenly laid on the three polypropylene oil absorption blue films after sampling;
[0072] S2, the three polypropylene oil absorption blue films were bent to completely wrap the to-be-tested rice in the polypropylene oil absorption blue film, and then another glass plate was used for capping;
[0073] S3, the polypropylene oil absorption blue film wrapped with the to-be-tested rice was transferred to a constant temperature drying box and heated at 55℃±2℃ for 60min, and then taken out. The to-be-tested rice wrapped in the polypropylene oil absorption blue film was completely poured out, and the oil spot situation on the polypropylene oil absorption blue film was observed.
[0074] The results are shown in Table 3 and Figure 3 The results show that the rice coated with oil, liquid paraffin or mineral oil at a coating level of 0.04% or above can form obvious oil spots on the surface of the polypropylene oil absorption blue film, and the coating of 0.04% oil, liquid paraffin or mineral oil can change the surface gloss of the rice, indicating that this coating amount as the detection limit can meet the application requirements and has practical significance. Therefore, the detection limit of the polypropylene oil absorption blue film is 0.04%.
[0075] Table 3
[0076]
[0077] Later, the inventors also prepared 7 blind samples according to the coating process for coating the coated grain, which were sample 1 to sample 7, and sent to a qualified laboratory (Hebei Grain and Oil Quality Inspection Center) for verification. The coating level of the prepared samples is shown in Table 4, and the verification report is shown in Figures 4-1 to 4-5The verification report shows that the results shown in the verification report are consistent with the results of the test method disclosed in the present application, indicating that the polypropylene oil-absorbing blue film can be used for testing oil or mineral oil coated food, but newsprint cannot detect 0.04% oil or mineral oil coated food because the detection limit is more than 0.08%.
[0078] Table 4
[0079]
[0080] Example 4
[0081] The polypropylene oil-absorbing blue film was selected as the experimental material, and green beans coated with different amounts of oil, liquid paraffin or mineral oil (coating amount of 0%, 0.04%, 0.12% and 0.2%) were used as the test green beans to investigate the oil spot situation under different coating amounts. The steps are as follows:
[0082] S1, take three polypropylene oil-absorbing blue films and place them on a clean and dry glass plate, then take three parallel samples from the test green beans, each taking 1g, and evenly spread them on the three polypropylene oil-absorbing blue films;
[0083] S2, fold the three polypropylene oil-absorbing blue films to completely wrap the test green beans in the polypropylene oil-absorbing blue films, then use another glass plate to cover them;
[0084] S3, transfer the polypropylene oil-absorbing blue film wrapped with the test green beans to a constant temperature drying oven and heat at 55℃±2℃ for 60min, then take it out, pour out the test green beans wrapped in the polypropylene oil-absorbing blue film, and observe the oil spot situation on the polypropylene oil-absorbing blue film.
[0085] The results are shown in Table 5 and Figure 5 The results show that green beans coated with oil, liquid paraffin or mineral oil at a coating level of 0.04% or above can form obvious oil spots on the surface of the polypropylene oil-absorbing blue film, and green beans coated with oil, liquid paraffin or mineral oil at a coating level of 0.04% can change the surface gloss of the green beans, indicating that this coating amount as the detection limit can meet the application requirements and has practical significance. Therefore, the detection limit of the polypropylene oil-absorbing blue film is 0.04%.
[0086] Table 5
[0087]
[0088] Example 5
[0089] 20 rice samples on the market were detected and analyzed by the standard method, 6 of which had obvious oil spots, and the detection results were positive. Then the 6 positive samples were quantitatively detected by liquid chromatography-gas chromatography method, and paraffin was detected in two of the positive samples, with a content of 1.7 mg / kg and 2.0 mg / kg, and paraffin was not detected in the other 4 positive samples, which may be samples coated with oil. Among the 14 negative samples, 6 were northeast japonica rice, and the northeast japonica rice had a high oil content, indicating that the standard method was not false positive for rice with high oil content; 8 samples were south indica rice, indicating that the standard was applicable to rice detection in different regions.
[0090] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. For those skilled in the art, other different forms of changes or variations can be made on the basis of the above description, and all the embodiments cannot be exhausted here. Any obvious changes or variations derived from the technical solutions of the present application are still within the protection scope of the present application.
Claims
1. A method for testing grains coated with grease or mineral oil, characterized in that, Includes the following steps: S1. Take n oil-absorbing blue films and place them on the carrier plate. Then take n parallel samples from the grain to be tested and place them on the oil-absorbing blue films respectively. S2. Fold each oil-absorbing blue film so that the grain to be tested is completely laid flat and rolled up inside the oil-absorbing blue film; S3. Heat the oil-absorbing blue film containing the grain to be tested. After the heat treatment, pour out all the grain to be tested that is wrapped in the oil-absorbing blue film and observe the oil spots on the oil-absorbing blue film. Where n takes the value of an odd number greater than or equal to 3; The testing method also includes determining the condition of oil stains: If the number of oil-absorbing blue films that show oil spots is 0, the result is considered negative. If the number of oil-absorbing blue films in the oil spots is greater than 0 and less than n / 2, repeat steps S1-S3. If the number of oil-absorbing blue films in the oil spots is still less than n / 2, the result is determined to be negative. If the number of oil-absorbing blue films in the oil spots is greater than n / 2, the result is considered positive. The heating temperature is 55℃±5℃, and the heating time is 60min-90min.
2. The testing method according to claim 1, characterized in that, The oil-absorbing blue film is selected from polypropylene oil-absorbing blue film.
3. The testing method according to claim 1, characterized in that, The oil is selected from vegetable oils.
4. The testing method according to claim 3, characterized in that, The vegetable oil is one or more of rice bran oil, soybean oil, and peanut oil.
5. The testing method according to claim 1, characterized in that, The grains mentioned are one or more of the following: rice, soybeans, mung beans, red beans, peas, and black beans.
6. The testing method according to claim 1, characterized in that, The detection limit of the test method is 0.04%.
7. The application of the test method as described in any one of claims 1-6 in the qualitative test of coated oils or mineral oil grains.