Application status and future development trend of food preservatives in China In the food industry, the preservation of various foods has always been an important problem to be solved urgently. It is estimated that about 20% ~ 30% of China's annual grain losses are caused by various kinds of corruption. Food corruption will not only make food lose its nutritional value, but also cause food poisoning. There are many reasons for food corruption, including physical, chemical, enzymatic and microbial factors. Among them, the role of microorganisms is the most serious. In order to prolong the shelf life of food, people use different means to inactivate microorganisms and delay or prevent their growth during food processing. Adding preservatives is one of the convenient and very effective food preservation methods, so it is widely used. Since the reform and opening up, the production of food preservatives in China has been developing for more than 20 years, and the output has been increasing and the technology has been improving. Quality improvement. At present, commonly used food preservatives are mainly divided into chemical food preservatives and natural food preservatives. 1 chemical food preservatives are mostly chemical preservatives used in China's market at present. Commonly used are: benzoic acid (sodium), sorbic acid (potassium), paraben, propionate, sulfurous acid and its salts, nitrate and nitrite. 1. 1 benzoic acid and its sodium salt benzoic acid, also known as benzoic acid, have the antibacterial mechanism of disturbing the respiratory system of microbial cells. It is difficult to circulate between acetic acid coenzyme A→ acetic acid and acetic acid oxalic acid → citric acid in TCA cycle, which hinders the normal physiological function of cell membrane. Benzoic acid combines with aminoacetic acid in human body to produce hippuric acid, which is eliminated in urine and will not accumulate. Because its effective component is undissociated benzoic acid molecule, it has good application effect in acidic food. Effective for yeast and mold. However, its use is controversial because of reports of superimposed poisoning. Although it is still allowed in various countries, the scope of application is getting narrower and narrower. For example, Japan has restricted or even partially banned the use of sodium benzoate in imported food, and Japan has stopped production. Because of its low price, it is still widely used in China. Mainly used to preserve soda, juice, soy sauce, canned food and alcohol. 1.2 sorbic acid and its potassium salt sorbic acid are unsaturated fatty acids, and its bacteriostatic mechanism is to form valence bonds with sulfhydryl groups of enzymes in microbial cells, so that it loses its activity and destroys the enzyme system, thus inhibiting the growth of microorganisms. Sorbic acid can participate in normal metabolism in the body, and is eventually oxidized into CO2 and water, which is basically harmless to the human body. And has no adverse effect on food flavor. It is recognized as one of the safest chemical preservatives in the world at present, and has been allowed to be used in all countries and regions. Because its active ingredient is undissociated sorbic acid molecules, it works well under acidic conditions. Sorbic acid mainly inhibits mold and yeast, but it can't play a role in the case of too many microorganisms. Therefore, it is suitable for foods with good sanitary conditions and few microorganisms. Sorbic acid is more expensive than benzoic acid, so its application is limited. At present, it is only used in high-end food. 1.3 p-hydroxybenzoic acid esters (methyl, ethyl, propyl, isopropyl, butyl, isobutyl, heptyl, etc. ) also known as nipagin esters, its antibacterial mechanism is basically the same as benzoic acid. It mainly inhibits the activities of microbial cell respiratory system and electron transfer enzyme system, and can destroy the structure of microbial cell membrane, thus achieving antiseptic effect. The antiseptic effect of p-hydroxybenzoic acid esters does not change with pH value, and the effect is better in the range of pH4~8. They can be used to replace acid preservatives, and their toxicity is lower than that of benzoic acid (but higher than that of sorbic acid). Because of its phenolic hydroxyl structure, its antibacterial performance is stronger than benzoic acid and sorbic acid, and it also has a strong effect on mold and yeast. The biggest disadvantage is that it has a special smell and its solubility in water is poor. Its solubility decreases with the increase of ester-based carbon chain length (for example, methyl ester is 0.25 g/ 100 g, heptyl ester is only 1.5 mg/ 100g), and its antibacterial effect is similar to that of methyl ester. Toxicity is inversely proportional to the length of alcohol chain. It can be quickly absorbed in gastrointestinal tract and hydrolyzed into p-hydroxybenzoic acid, which is excreted with urine. At present, China's national standards stipulate that only ethyl ester and propyl ester in the paraben series can be used in food. 1.4 propionate is converted into propionic acid in vivo, and monomer propionic acid molecules can form high osmotic pressure outside mold cells, which makes mold cells dehydrated and lose fertility. It can penetrate the cell wall of mold and inhibit intracellular activity. At the same time, propionic acid is a normal component of food and a normal intermediate of human metabolism, which is easily absorbed by the digestive system, has no accumulation and is not excreted with urine. After oxidation, ω-can combine with coenzyme A to form succinic acid or ester, and participate in the cyclic metabolism of tricarboxylic acid into CO2 and water. Because the effective component of propionate is propionic acid, it must be in an acidic environment to produce antibacterial effect. In food, mainly used in bread and cakes, the dissociation constant is low. It is ineffective for yeast, so it does not affect the normal fermentation of bread [4]. However, China has been unable to produce propionic acid for a long time, mainly relying on imports. In recent years, China has just started industrial production of propionate, but the output is very low. The application of propionate in food is limited. Sulfuric acid and its salts mainly include sulfite, pyrosulfite and sulfur dioxide. Its effective component is sulfurous acid molecule. The sterilization mechanism of sulfurous acid is to consume O2 in food, make aerobic microorganisms die due to lack of oxygen, and inhibit the activity of enzymes in some microbial physiological activities. Because the residual sulfur dioxide after the use of sulfite will cause serious allergic reactions, especially for asthma patients, FDA prohibits it as a preservative in raw fresh fruits and vegetables in 1986. In China, some foods are processed with. 1.6 nitrate and nitrite, and a small amount of nitrate or nitrite is a common food preservation method. Nitrate and nitrite are indispensable preservatives in cured bacon (traditional meat in China). They not only make food have unique color and fragrance, but also have antibacterial effect, which can inhibit the growth of bacteria and the formation of spores, especially Botox. However, nitrate and nitrite can react with other substances in bacon to produce nitroamines that may cause cancer. The content of nitrate in food is generally very small and will not cause poisoning. The bacteria in human intestine can transform nitrate into nitrite, which has great influence on human health. In recent ten years, with the progress of science and technology and the continuous improvement of analytical methods, people have gradually discovered that chemical preservatives, which used to be considered safe, are actually carcinogenic or potentially carcinogenic. For example, NaNO2, which is used for meat coloring and preservation, can easily form a strong carcinogenic N- nitrosamine compound with proline in the digestive system. Triazole compounds have a good antiseptic effect on fruits, but they may cause cancer. For another example, if sulfur dioxide remains in food, it will cause serious allergic reactions. Natural food preservatives are based on the fact that most chemical food preservatives remain in the body and have certain toxicity and special smell. In China, the safety of food preservatives has been paid more and more attention, and the chemical preservatives that can be used as food preservatives are increasingly restricted, which greatly hinders the production, transportation and storage of food. It is urgent to research and develop efficient and nontoxic natural food preservatives. With the continuous development of biotechnology, natural bio-food preservatives produced by extraction, enzyme transformation or fermentation from metabolites of plants, animals or microorganisms have been paid more and more attention. It is also the main direction of preservative market in China in the future. 2. 1 botanical food preservatives At present, the research on botanical natural food preservatives in China is extremely active and has achieved gratifying results. The reason is that China is rich in natural plant resources, among which there are many substances with antibacterial biological activity. It has great potential market value. At present, the following botanical preservatives have made progress. 2. 1. 1 Spices generally refer to the roots, barks, seeds or fruits of aromatic plants growing in tropical or subtropical regions, which have the functions of flavoring and enhancing fragrance, and many of them have different antibacterial and antiseptic effects. Through the research in recent years, it is found that these spices can inhibit bacteria and prevent corrosion. What really works is its essential oil, but at present, the essential oil or extract of spices is mostly used in the research and development of food preservatives. Yang Ronghua and others concluded that the antibacterial components of spices mainly include eugenol, eugenol acetate, allyl isothiocyanate, thymol, carvacrol, isoborneol, anethole, cinnamaldehyde, vanillin, capsaicin and salicylaldehyde. The study on the antibacterial properties of aromatic plant essential oil shows that the solubility in water phase is directly related to the ability of effective components in essential oil to penetrate cells into bacteria, and the antibacterial properties are based on the double-layer antibacterial agent on bacterial cell membrane. Terpenes in essential oil reduce the stability of biofilm, thus interfering with the enzymatic reaction of energy metabolism. 2. 1.2 Chinese herbal medicines, including general herbs, have reached more than 5,000 kinds in China, and about 700-800 kinds are commonly used, most of which are plant medicines. Chinese herbal medicine has always been recognized as beneficial to health and has a specific therapeutic effect. Using traditional Chinese medicine with a long history as food preservative has the advantages of low toxicity and being more acceptable to consumers. Over the years, Chinese scholars have done a lot of research on the antibacterial effects of Chinese herbal medicines, and found that many Chinese herbal medicines have antibacterial effects with a wide range of antibacterial activities. It has a strong inhibitory effect on common pathogenic bacteria such as Neisseria gonorrhoeae, Candida albicans, Shigella dysenteriae, Staphylococcus aureus, Escherichia coli, typhoid Bacillus, Aspergillus niger, Aspergillus flavus, Aspergillus japonicus, Aspergillus versicolor, Huang Qing-producing mold, Chaetomium, Curvularia, Cladosporium and Penicillium citri. At present, it is found that Chinese herbal medicine has the strongest antibacterial ability, followed by rhubarb, scutellaria baicalensis, folium Isatidis, folium Artemisiae Argyi and Penicillium. Followed by Cortex Phellodendri, Radix Scrophulariae, Fructus Forsythiae, Rhizoma Anemarrhenae, Verbena, Mume, Pulsatilla, Herba Artemisiae Scopariae, Taraxacum, etc. There are few literatures on safety evaluation of natural food preservatives and antibacterial components in Chinese herbal medicines. As for the mechanism of action, it is generally believed that antibacterial components in Chinese herbal medicines are mostly hydrophobic small molecular organic compounds, which interfere with microbial cell membranes and even dissolve. So as to inhibit or kill microorganism. 2. 1.3 Pectin, a product of pectin decomposition, is a kind of water-soluble natural polymer, which mainly exists in the peels of lemons, oranges, grapefruit, oranges, grapes and other waste residues such as beets and apples. Professor Hiroshi Yokozuka of Yamanashi University in Japan and others found that pectin decomposition products obtained by enzymatic decomposition of pectin have a significant inhibitory effect on the proliferation of bacteria in food, especially Escherichia coli. At present, pectin decomposition products, together with other natural preservatives, have been widely used in the preservation of pickled vegetables, salted fish, beef patties and other foods abroad. Chinese scholar Li Xuehong and others used apple pomace as raw material to prepare pectin decomposition products through acid-water hot extraction, direct enzymolysis of pectin extract and atmospheric concentration. It has obvious inhibitory effect on food spoilage bacteria such as Escherichia coli, Bacillus subtilis, Azimuth, Proteus, Bacillus megaterium, Staphylococcus aureus, lactic acid bacteria, etc., and its minimum inhibitory concentration is below 0.0 1.48%, but it has no inhibitory effect on yeast and mold. The antibacterial performance of pectinase hydrolysate is directly related to its enzymatic hydrolysis degree, indicating that the antibacterial performance of pectinase hydrolysate is related to molecular weight. The effective antibacterial component should be low molecular weight polygalacturonic acid. The specific antibacterial mechanism needs further study. Pectinase hydrolysate can be used for pickling vegetables, noodle soup products and dairy products, and has ideal antiseptic effect. At the same time, the process is simple and easy to operate, and the processing cost is low. It is a new natural food preservative with great development value. At present, the domestic research is still at the laboratory level, and there is no large-scale production of pectin hydrolysate in the market. 2. 1.4 Ginkgo biloba extract from other plants: Ginkgo biloba is one of the endemic plants in China. Gong Xia and other studies show that the minimum inhibitory concentrations of Ginkgo biloba extract on common pathogenic bacteria in food are Staphylococcus aureus 8%, Proteus 6%, Escherichia coli 6%, Bacillus subtilis 6%, Aeromonas 5% and Salmonella 6% respectively. At the same time, the higher the concentration, the higher the bacteriostatic rate, and the longer the same concentration is used, the higher the bacteriostatic rate, and it has thermal stability. Water chestnut peel extract: Many scholars have studied the antibacterial effect and application effect of water chestnut extract prepared from water chestnut skin. Ceng Ying and others boiled with water and ethyl acetate. The bacteriostatic circle of the extract was determined by filter paper method. The experiment shows that the alcohol extract of horseshoe skin acid has strong antibacterial effect. The minimum inhibitory concentrations of the preparation to common food-contaminated bacteria and fungi were 0.365438 0.25% and 2.5%, respectively, and the bacteriostatic effect was greater than that of sodium benzoate, with good thermal stability. After being treated with 12 1℃ and 15 min, it still has strong antibacterial effect. Wu Jianzhong and others used the same process route to extract fresh-keeping components from bamboo leaves with water and organic solvents. The minimum inhibitory concentration of the bamboo leaf extract on common pathogenic bacteria is 0.2%. At the same time, some scholars have isolated antibacterial extracts from other plants with antibacterial effects, such as ginger, cinnamon, clove, Lindbergh, red yeast, sweet pepper, pepper and so on. 2.2 Animal food preservative 2.2. 1 protamine is a small and simple alkaline spherical protein found in fish sperm cells. It can inhibit the growth of Bacillus subtilis, Bacillus megaterium, Bacillus licheniformis, Bacillus coagulans, Lactobacillus plumule, Lactobacillus casei and Streptococcus faecalis. It is found that protamine can interact with some protein involved in nutrient transport or biosynthesis system on cell membrane, which destroys the function of these protein, thus inhibiting cell metabolism and leading to cell death. Protamine has high antibacterial ability in neutral and alkaline media. Its thermal stability is also quite high, and it still has certain activity when heated at 12 1℃ 15 min. At the same time, its bacteriostatic range and food preservation range are wide. It has a strong inhibitory effect on Bacillus subtilis, Bacillus, Lactobacillus casei, Lactobacillus plumule, lactic acid bacteria, mold, spore thermophilic bacteria and gram-positive bacteria, but it has a strong inhibitory effect on gram-negative bacteria. Followed by dishes, spices and so on. Protamine combined with other natural additives has a more significant antibacterial effect. 2.2.2 Chitosan, also known as chitin, is a polysaccharide extracted from crab shells and shrimp shells. Chitosan has a wide range of antibacterial effects. When the concentration is 0.4%, it has a strong inhibitory effect on Escherichia coli, Proteus vulgaris, Bacillus subtilis and Staphylococcus aureus. Preservatives made of chitosan, copper acetate and adipic acid have more obvious antibacterial effect and do not affect food flavor. Chitosan is insoluble in water, usually soluble in vinegar, and is mainly used for curing food. Chitin approved for use in China 19 1 year is nontoxic. It is an excellent natural preservative for fruits and vegetables. In recent years, many research papers on the preparation and application of chitin and its derivatives have been published in domestic related publications. With the in-depth study on the antibacterial mechanism of chitin, its application will be more and more extensive. 2.2.3 Propolis is the material basis for the existence, reproduction and development of bees. Scientists from all over the world have confirmed through research that propolis is an activator of immune factors. It contains flavonoids and a variety of active ingredients, which can significantly improve human immunity and has good preventive and therapeutic effects on diabetes, cancer, hyperlipidemia, leukemia and other stubborn diseases. At the same time, propolis has a strong inhibitory and killing effect on viruses, germs and molds, and has no toxic and side effects on normal cells. Therefore, adding propolis to food is not only a natural advanced nutrient, but also a natural food additive. 2.3 microbial food preservative 2.3. 1 lysozyme produced by Streptomyces globosa is a kind of hydrolase that specifically acts on microbial cell walls. Its mechanism is to destroy the cell wall of bacteria, yeast and mold, and break the glycosidic bond and peptide bond in the cell wall. Eventually, cells die. Lysozyme is a non-toxic, harmless, highly safe and highly alkaline protein with certain health care functions. It can selectively decompose microorganisms without affecting other substances. The enzyme has a strong decomposition effect on gram-positive bacteria such as Bacillus subtilis and radiation-resistant micrococcus, and also has a certain degree of dissolution effect on gram-negative bacteria such as Escherichia coli, Streptococcus mutans and Vibrio parahaemolyticus. The most effective concentration is 0.05%. At present, lysozyme is generally extracted from egg white in China, which is expensive, mainly used for scientific research and rarely used for food preservation. 2.3.2 Nisin is a polypeptide compound composed of various amino acids, which can be absorbed and utilized by human body as a nutrient. 5438+0969, FAO/WHO Joint Expert Committee on Food Additives (FAL/ WHO) confirmed that nisin can be used as a food preservative. 1The document approved by the Ministry of Health of China in March, 1992 pointed out: "It can be scientifically considered that nisin is safe as a food preservative". It can effectively inhibit many gram-positive bacteria that cause food spoilage. Such as Botox, Staphylococcus aureus, Streptococcus hemolyticus, Listeria, Bacillus stearothermophilus, have special effects on gram-positive bacteria that produce spores. The antibacterial effect of nisin is to interfere with the normal function of cell membrane, leading to cell membrane infiltration, nutrient loss and membrane potential decline, thus leading to the death of pathogenic bacteria and spoilage bacteria cells. It is a non-toxic natural preservative. It has no adverse effect on the color, aroma, taste and taste of food. It has been widely used in dairy products, canned products, fish products and alcoholic beverages. 2.3.3 Natamycin is a white to milky white odorless and tasteless crystalline powder made by Streptomyces natamycin through controlled fermentation. It usually exists in enol structure. Its mechanism of action is to combine with ergosterol and other sterol groups of fungi, thus preventing ergosterol biosynthesis, distorting cell membrane and eventually leading to leakage and cell death. The surface treatment of dough with natamycin in baked goods can obviously prolong the shelf life. Adding a certain amount of natamycin in the production of sausage, beverage and jam can not only prevent mildew, but also not interfere with other nutrients. 2.3.4 ε- polylysine ε-polylysine research abroad has been relatively mature, especially in Japan, China has just started. It is a natural biological metabolite with good bactericidal ability, thermal stability and great commercial potential. In Japan, ε -polylysine has been approved to be added to food as a preservative. Widely used in the preservation and antisepsis of instant rice, wet cooked noodles, cooked vegetables, seafood, sauces, soy sauce, fish fillets and biscuits. Xu Honghua and others in China studied the preservation effect of ε -polylysine on milk. When 420 mg/L ε-polylysine is mixed with 2% glycine, the preservation effect is the best, and it can be stored for 1 1 day, which is still at a high level. At the same time, it is found that ε-polylysine has obvious synergistic effect with other natural bacteriostats, which can improve its bacteriostatic ability. In the United States, researchers suggested that ε -polylysine should be used as a preservative in food. Practice has found that ε -polylysine can interact with protein or acidic polysaccharide in food, resulting in the loss of antibacterial ability. Moreover, the emulsifying ability of ε -polylysine is weak, so ε -polylysine is limited to starchy foods. At present, China is still in the stage of laboratory research and development. Because China is rich in natural resources of animals, plants and microorganisms, it has obvious advantages to develop natural extracts to prepare preservatives compared with European and American countries. With the increasing restrictions on the use of most chemical preservatives, China's natural animal and plant and microbial preservative products will surely be favored by the international market. But at the same time, we also see that most of the natural preservatives used at present are crude products, and the content of their effective components often changes with the changes of seasons and geographical environment. It is not clear what some natural preservatives are. Needless to say, pure products are isolated for toxicological evaluation. In addition, there are few reports on the detailed grouping, bacteriostasis or antibacterial mechanism of natural preservatives, which need further subdivision by food scientists. Discussion With the improvement of living standards of Chinese residents, food safety has been paid more and more attention, and the development of new efficient and nontoxic preservatives is the focus of the development of food preservative industry in China. According to this purpose, the current development direction of food preservatives in China is as follows: ① In-depth study of sorbic acid, propionic acid and their salts, the key is to improve the production technology and reduce the production cost; (2) vigorously develop new natural food preservatives, explore their mechanism of action, and develop efficient and low-cost production technologies; (3) Study a new natural compound preservative to further improve the anti-corrosion efficiency; ④ The existing safe and efficient varieties were modified by molecules to develop better varieties.