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Food Preservatives Detection and Development Direction
HC Food Industry Network With the improvement of living standards, the issue of food safety has received more and more attention from people, and people's requirements for food have become higher and higher. The food preservatives came into being as a result of the deterioration of the foods caused by the activity of microorganisms and the loss of their original nutritional value. Food preservatives are food additives that prevent spoilage caused by microorganisms and extend the period of food preservation. It is divided into chemical food preservatives and natural food preservatives . At present , there are 23 categories of food additives in China, more than 2,000 varieties, including acidity regulators, anti-caking agents, defoamers, antioxidants , bleaches , leavening agents , colorants, color protection agents, enzyme preparations, flavor enhancers, nutritional fortifiers, preservatives, sweeteners, thickeners, spices, etc.  . The important thing for food preservatives is that it can inhibit the occurrence of the most perishable effect under different conditions, especially when the general sterilization effect is insufficient. Mineral oil, coal tar, and tannin used for the preservation of fibers and wood, formaldehyde, mercury, toluene, butyl p-hydroxybenzoate, or balsam for biological samples . The use of preservatives in foods is limited, so many physical methods such as drying and salting are used. The special preservatives include organic acids such as acetic acid, vegetable oils containing oleic acid, and special essential oils such as mustard.
1. Current situation
Food preservatives are a type of food additive. Whether various food additives in foods will interact with each other to generate other harmful substances is currently inconclusive, but it is certain that some toxic compounds have been contaminated due to the impure raw materials used in the manufacture of additives, causing acute and chronic poisoning . . For example, the Morinaga milk powder incident in Japan is the use of excessively high levels of additives that cause high levels of arsenic in milk powder to cause poisoning in more than 10,000 babies. The accumulation of butyl hydroxy groups as antioxidants in the body poses potential hazards to the body  . Detecting the content of food preservatives can be used as a limit indicator for food addition , which helps to reduce the harm to human body.
2·Food Antiseptic benzoic acid detection method
2.1 UV spectrophotometry
The determination of benzoic acid, a food preservative, is usually carried out using ether-based alkali titration and steam distillation ultraviolet spectrophotometry. These two methods have complex procedures, long cycle times, and low recoveries. On the basis of the work of predecessors, ethyl ether extraction and ultraviolet spectrophotometry were used to determine . The sample analysis results show that this method is simple, accurate and fast. After sample processing and inspection, the minimum detection limit of the method is 0.0010 mg/mL and the recovery rate is 98%. The whole process of the assay can be completed in about 1 hour. Visible, UV spectrophotometry is relatively simple, accurate and fast.  Benzoic acid and sorbic acid are both conjugated organic compounds with strong absorption in the near ultraviolet region. High-performance liquid chromatography showed that, and confirmed by experiments, benzoic acid had maximum absorption at 230 nm and sorbic acid at 263 nm. On the other hand, benzoic acid and sorbic acid have suitable solubility in water. The solubility of benzoic acid at 10°C is 0.21g/100mL water: 0.28g/100mL water at 20°C; the solubility of sorbic acid at 20°C is 0.21g/100mL water: 0.25g/100mL water at 30°C, Therefore, the standards and samples can be processed into aqueous solutions. The combined determination of benzoic acid (sodium) and sorbic acid （potassium ) in acidic foods was achieved using a standard spectrophotometer using an ultraviolet spectrophotometer . This method is simple, rapid, and can be used as a company's own control and product inspection. The reference method.
2.2 Fluorescence Spectral Analysis
Aromatic compounds have conjugated unsaturated structures and can undergo π-π energy level transitions, and their fluorescence intensity is large. The greater the degree of π-electron conjugation in this system, the more non-localized the π-electron, the easier it is to be excited, and the more prone to fluorescence, the longer the fluorescence spectrum will shift. The excitation light is used as the light source to provide energy, so that the ground state molecule of the test object obtains energy and then transitions to the excited state. When the lowest vibration energy layer in the excited state returns to the ground state, fluorescence is generated and the fluorescence emission can be directly measured by the fluorescence analyzer. strength. Therefore, direct emission measurement can be used to measure the fluorescence emission intensity of benzoic acid to calculate the content of benzoic acid in the sample. The fluorescence spectrum analysis of benzoic acid content  explores the best test conditions and eliminates the influence of the external environment on the experimental results as much as possible. The optimal test conditions for this method ( excitation wavelength 225 nm , emission wavelength 310 nm, solution pH 2~3 ). This method is simple, accurate and highly sensitive. The recovery rate of benzoic acid was 99.38%~102.3%. Hu et al. reacted the preservative (1) in ammonium acetate-acetate buffer solution with formaldehyde and acetylacetone to form dihydropyridine derivatives (2); (2) characteristic absorption at 410 nm and fluorescence at 510 nm Sex. The content of the preservative (1) can be calculated by measuring the fluorescence intensity of the dihydropyridine derivative.
2.3 High performance liquid chromatography
Determination of benzoic acid and sorbic acid in jams by high performance liquid chromatography showed recoveries of 95%–104% . The detection limits of benzoic acid and sorbic acid were 25 mg/kg and 6.25 mg/kg, respectively. Simultaneous detection of benzoic acid, sorbic acid, p-hydroxymethyl and propyl parabens in food using high performance liquid chromatography. The target was washed with methanol-acetate buffer (pH=4.4). The detection wavelength was 254 nm within 23 minutes. It can be detected. Feng Hui et al. used high-performance liquid chromatography to detect the contents of benzoic acid, sorbic acid and saccharin sodium in pickled samples of pickled vegetables in accordance with the requirements of the national health related product hygiene supervision sampling plan. In the actual detection process, dual wavelength detection technology was used. New methods, such as supplementary qualitative methods, have improved the deficiencies in the quasi-determinism of the national standards testing methods. Chen Fahe et al. first reported the simultaneous determination of eight food additives commonly used in foods by solid-phase extraction-RP-HPLC , including benzoic acid, sorbic acid, sodium saccharin, acesulfame-K, lemon yellow , sunset yellow , carmine , Amaranth, the sample was sampled by AccuBond ODS-C18 solid phase extraction column and injected. After reversed-phase high-performance liquid chromatography, the average recoveries were between 78.1% and 112.5%, and the relative standard deviation was less than 5.  Liquid chromatography-mass spectrometry (HPLC-MS) is a new technique that has been developed in recent years. It combines high resolution of complex matrix compounds with liquid chromatography, and unique selectivity, sensitivity, and relative molecular mass of mass spectrometry. Quality and structure information in one, provides an effective analysis method for food quality testing. The chemically similar benzoic acid and benzoyl peroxide in flour were quantitatively determined by mass spectrometry and high performance liquid chromatography. The recoveries were 91.3% and 96.0%-99.3%, respectively.
2.4 Gas chromatography
Because the instruments used by HPLC are expensive and difficult to popularize, the scope of application is limited. Gas chromatography is also one of the most important rapid analytical techniques. It has excellent sensitivity and high resolution. For example, if glass wool is inserted into the glass mat of the injection section or a guard column is used before the analysis column, the analysis column can be prevented from being contaminated by non-volatile substances, prevent the interference of pollutants, and reduce the peak tailing effect to improve the gas phase. Chromatographic resolution, but also can extend the life of the column. Liu Yangxi and others used solid-phase microextraction and gas chromatography to analyze the ethyl p-hydroxybenzoate in the soy sauce. The ethyl para-hydroxybenzoate was used for the determination of the repeatability, less interference, high sensitivity, and recovery. The rate is between 97.2% and 103.4% and can be used for rapid monitoring and analysis of ethyl p-hydroxybenzoate in soy sauce. Wang Wenfang et al. used the splitless/splitter injection mode to determine sorbic acid and benzoic acid in beverages. The detection limits of sorbic acid and benzoic acid were 0.813 ug/mL and 0.606 ug/mL, respectively, and the relative standard deviations of the three parallel determinations of the samples were all less than 6.42%. The recoveries were between 87.0% and 97.8%.  Zhang Jianhua, etc. improved the chromatographic column packing of the gas chromatograph, using stainless steel columns, filled with ethylene glycol succinate, to obtain a good peak shape of benzoic acid and sorbic acid in food, the detection limit is 5μg/kg The recovery rate was 94%~103% . Dillurer Malik et al. used a 10m long, 100μm ID HP-5 melted silica capillary column to simultaneously determine six common preservatives by gas chromatography under rapid programmed temperature conditions . The average recovery of each component was 96.45%, the minimum detection limit was 1.2~10ug/mL, and the linear correlation coefficient was greater than 0.994.
2.5 Other methods
Due to the strong characteristic of infrared spectrum, the pretreatment is simpler and more convenient than the chromatographic method , and it is universally applicable. It can also test micro-samples, so it is also an effective method for analysis and identification.