In recent years, people have paid more and more attention to food safety and quality. The food mentioned here is food in a broad sense, including primary agricultural products, such as grains, oilseeds, vegetables, aquatic products, livestock and poultry products, fruits, etc., as well as processed foods, such as canned food, ham sausage, edible oil, instant noodles, pickles and condiments. More and more laboratories carry out food testing. In these laboratories, due to the different nature and testing items, there are different requirements for the purchase and selection of instruments in the process of laboratory preparation and development. According to the working experience in these years and the experience of various laboratory inspections, this paper puts forward some personal suggestions on the configuration of instruments and equipment in food testing laboratories for the reference of relevant personnel.
enterprise laboratory
the enterprise laboratory can be set according to the variety of products produced, the number of testing items and the size of production scale, and the configuration of laboratory instruments and equipment can be complicated and simple. For such a laboratory, the configuration of instruments and equipment can meet the product quality inspection of enterprises.
food inspection can be divided into two major items, one is to test the quality of products; The second is to test the hygiene items of products, which are relatively difficult and costly.
(1) Quality items include: water content, salt content, sugar content, protein content, fat content, fiber content, vitamin content, acidity, etc. For the detection of these projects, if the funds are limited, chemical analysis can be used, and only the simplest equipment such as oven, water bath, electric furnace, agitator, pulverizer and pH meter can be configured. If the funds are sufficient or there are many inspection batches, there are corresponding special instruments for the corresponding inspection items. In addition, there are some general instruments available for purchase, such as: UV/visible spectrophotometer, near infrared analyzer, automatic titrator, etc. Fluorescent photometers are sometimes needed to detect vitamins A and E.. To detect nutrient elements, such as calcium, zinc and iron, you can purchase an atomic absorption spectrometer-flame detector.
(2) Health items include: microorganisms, additives, harmful elements, pesticide residues, veterinary drug residues, toxins, etc. For general food enterprises, microbial testing laboratories should be built.
a) Microbiology
The layout of microbial laboratories should be in accordance with the requirements of biological laboratory standards. Necessary equipment includes clean table, incubator, autoclave, electric furnace, etc. Other equipment is configured according to specific testing items. If you have less money, you can buy domestic ones, but if you have more money, you can consider buying imported ones. The prices of the two are quite different.
b) additives and harmful elements
some items can be chemically treated, such as nitrite, sulfur dioxide, heavy metal content and total arsenic. However, in order to meet the current national food hygiene requirements, gas chromatography-hydrogen flame detector and liquid chromatography-ultraviolet/visible light detector should be purchased, so that common preservatives (benzoic acid, sorbic acid, etc.), sweeteners (sodium cyclamate, saccharin sodium, etc.) and pigments (lemon yellow, carmine, etc.) can be detected. Buy an atomic absorption spectrometer-graphite furnace detector, which can detect harmful elements such as lead, chromium, cadmium, copper and nickel respectively, and also need an atomic fluorescence spectrometer to detect arsenic and mercury.
c) residual pesticides
it is indispensable to detect residual pesticides by gas chromatography. To detect organochlorine pesticides, an electron capture ECD detector is needed; To detect organophosphorus pesticides, a flame photometric FPD detector or a nitrogen and phosphorus NPD detector is required. At present, there are more and more items for pesticide residue detection. In order to improve universality, it is suggested to configure capillary column shunt/undivided flow into the sample port and install capillary column. Compared with the traditional packed column chromatographic column, the capillary column has many analytical items and good resolution, which can reduce the frequent replacement of chromatographic column and improve the analysis efficiency. There are more and more pesticide residue items to be detected in the products produced by export food processing enterprises. In order to ensure the quality of raw materials and products, gas chromatography-mass spectrometry can be configured. Generally, only electron bombardment EI source is needed, and a negative chemical NCI source can be provided if necessary. Whether to choose quadrupole mass spectrometry or ion trap mass spectrometry is acceptable, and both instruments have their own advantages and disadvantages. It still depends on the specific work.
d) Residual veterinary drugs
If there are few items and many batches for the detection of residual veterinary drugs, an enzyme-linked immunosorbent assay (ELISA) can be considered, which has the advantages of small investment, simple operation and high detection sensitivity. The use of ELISA also has some disadvantages. First, the kit is a long-term consumable, and the cost will be higher if the test batch is small. Second, the specificity is not good, and there may be false positives. Third, if there are many test items in a relatively long period of time, the cost is even higher than that of instrument analysis. For export food enterprises with a certain scale, in order to meet the detection limit requirements of developed countries such as the European Union, the United States and Japan, it is best to configure a liquid chromatography-tandem mass spectrometer. The first instrument is suggested to be equipped with a triple quadrupole mass spectrometer, which has high sensitivity and good reproducibility. The instrument doesn't have to pursue high configuration, just enough, but its sensitivity, stability and anti-pollution performance are better. It's best to buy a model with more users and a user group similar to their own testing items. First of all, it shows that there is no problem in testing the items to be tested by this model instrument, and secondly, it is convenient for future technical exchanges.
commercial laboratories
compared with enterprise laboratories, commercial laboratories detect more commodities and items than enterprises, so the configuration of instruments and equipment should be more perfect than enterprise laboratories in terms of categories and quantity. The configuration of instruments and equipment can not only meet the needs of current testing, but also be ahead of schedule, otherwise it will be difficult to get customers back when they come to you and are pushed away by you.
1) For testing quality items, it is usually necessary to consider the standards used or configure corresponding testing instruments and equipment according to customers' requirements (refer to paragraph 1. Quality items of enterprise laboratories). Because different commodities and different customers may put forward different testing standards or methods for the same project, for the testing of these projects, if the method provides for chemical analysis, only the simplest equipment needs to be configured (refer to paragraph 1. Enterprise Laboratory Quality Project). If the funds are sufficient or there are many inspection batches, and the corresponding detection methods are instrumental, corresponding special instruments can be configured, such as moisture analyzer, Kjeldahl nitrogen analyzer, quick fat analyzer, sugar meter, viscometer, fatty acid analyzer, etc. General instruments can also refer to a paragraph of enterprise laboratory quality project. If necessary, a special analyzer such as amino acid analyzer can also be configured.
2) See the relevant paragraph of "1. Enterprise Laboratories" for the laboratory configuration of health project testing. Personally, I think that liquid chromatography-tandem mass spectrometry and gas chromatography-mass spectrometry are indispensable for a modern commercial laboratory, which are the conditions required by the instructions and standards for issuing positive reports on banned agricultural and veterinary drug residues. If there is a large scale and many testing items, each type of instrument should also be equipped with multiple sets. At this time, we should consider the complementarity of instrument performance, such as: liquid chromatography-tandem mass spectrometry with a distribution spray ionization source and an atmospheric pressure chemical ionization source; Gas chromatography-mass spectrometry is equipped with one electron bombardment source and one negative chemical ionization source. There are many elements and miscellaneous samples, and plasma emission spectrometry-mass spectrometer and gas chromatography-tandem mass spectrometer can also be considered. If morphological analysis is to be done, plasma emission spectrometry-mass spectrometer should also be able to be combined with liquid chromatography or gas chromatography.
Industry Laboratories
Industry laboratories in China (referring to government regulation laboratories) are all affiliated to administrative leading bodies in different industries, so they all have some administrative effects. In recent years, the government has attached great importance to food safety and increased investment, so the hardware of the laboratory has been greatly improved. At present, a relatively complete industrial laboratory (above the provincial and municipal level) should be equal to or better than the general commercial laboratory in terms of the types and quantity of analysis and testing equipment, and in order to improve the analysis efficiency, it can also improve the configuration of pretreatment equipment, such as microwave digestion (including microwave extraction), automatic solid-phase extractor, gel chromatography purifier, solvent accelerated extractor, high-speed freezing centrifuge, high-speed homogenizer, nitrogen blower and so on. These pretreatment equipments are more efficient and automatic (samples can be processed automatically in the evening), and the reproducibility of the results will be improved.
As China's administrative supervision system is in line with the international developed countries, our industry laboratories are increasingly participating in the capacity comparison activities of some international authoritative organizations, and the testing methods and results are carried out in accordance with international common practices. In addition, in order to adapt to the development of food safety testing, many laboratories began to develop new analytical methods. Therefore, industrial laboratories will be equipped with higher-end analytical instruments, such as high-resolution mass spectrometer, to make the final test results more accurate.