When it comes to antioxidants, you may be a little unfamiliar with it, but we are exposed to it every day in our daily lives. Antioxidants need to be added to our edible oils and industrial products, and even what we like to eat Some fruits, honey, and tea you drink are natural antioxidants; many people feel dangerous when it comes to chemical agents. In fact, antioxidants themselves are harmless and can be added to food, and antioxidants are It is a very broad concept. The well-known vitamin E, tea polyphenols, etc. are also considered antioxidants. In order to give everyone a basic understanding of it, the editor will briefly introduce the ingredients and classification of antioxidants.
Classification of antioxidants:
(1) Antioxidants can be divided into synthetic antioxidants (such as BHA, BHT, PG, etc.) and natural antioxidants (such as tea Phenol, phytic acid, etc.).
(2) Antioxidants can be divided into three categories according to solubility: oil-soluble, water-soluble and compatibility. Oil-soluble antioxidants include BHA, BHT, etc.; water-soluble antioxidants include ascorbic acid, tea polyphenols, etc.; compatible antioxidants include ascorbyl palmitate, etc.
(3) Antioxidants can be divided into free radical absorbers, metal ion chelators, oxygen scavengers, peroxide decomposers, enzyme antioxidants, ultraviolet absorbers or singlet oxygen quenchers according to their mode of action. Killers, etc.
The antioxidants commonly used in our lives include 2,6-di-tert-butylcresol, butylhydroxyanisole (BHA), dibutylhydroxytoluene (BHT), tert-butylhydroquinone ( TBHQ) etc.
Antioxidant ingredients:
The following is the most widely used 2,6-di-tert-butylcresol 2 as an example. We can see it from its different production methods. ingredient ratio. (1) Put p-cresol and tert-butyl alcohol into the reaction kettle at a molar ratio of 1:1.1 and heat to dissolve. Under the action of the catalyst phosphoric acid, react under strong stirring at 65-70°C; after the reaction is completed, the reaction product is first washed with 10% sodium hydroxide solution until it is alkaline, and then washed with water until it is neutral; the solvent is removed and recrystallized with ethanol The finished product is obtained. CH3C6H4OH+(CH3)3COH[H3PO4]→BHT
(2) Pour isobutylene into a mixture of 98% p-cresol and 2% concentrated sulfuric acid, and react at 65~70°C for 5 hours; use 60 ℃ hot water to wash away the acid, and then wash with 10% NaOH and hot water until neutral to obtain a crude product. Dissolve the crude product in 50% hot ethanol, add 0.5% thiourea, filter while hot, spin dry, and dry to obtain the finished product. The yield is as high as 90% to 95%, the purity is 99.5%, and the melting point is >69.5°C. In industry, the main and auxiliary towers are connected in series. First, add paracresol and catalyst into the main and auxiliary towers. Control the temperature of the main tower at 65-80°C and the auxiliary tower at 50-70°C.
Isobutylene gas is introduced from the bottom of the main tower, and most of it reacts with p-cresol in the main tower. The remaining part comes out from the top of the main tower and enters the bottom of the auxiliary tower to further react with p-cresol. The reaction period of the main tower is controlled at 4 to 5 hours. When the reaction is completed, stop passing the isobutylene gas, add 20% NaOH solution, and bubble with compressed gas. The neutralized alkylated product is separated through a distillation tower (8 theoretical plates) to obtain crude product. The latter is dissolved in 95% ethanol, ion exchanged to remove inorganic salts, cooled to 10-20°C for crystallization, separation, and vacuum drying to obtain a product with a melting point greater than 69°C. CH3C6H4OH+(CH3)2C=CH2[H2SO4]?→BHT
Uses of food antioxidants
Food antioxidantsFood antioxidants are usually used in grease and oil-containing foods, such as fried instant noodles, etc. Antioxidants in fried foods. Because its function is to prevent or delay the oxidation and deterioration of food, it cannot change the result of oxidation, so it must be added before the oil is oxidized. While using phenolic antioxidants, adding certain acidic substances such as citric acid and phosphoric acid can significantly improve the antioxidant effect. These acidic substances are called synergists. It is generally believed that they can chelate trace metal ions that promote oxidation, thus playing an antioxidant and synergistic role.
Due to the high toxicity of synthetic antioxidants such as BHA and BHT, domestic and international attention is paid to the research and development of natural antioxidants. In addition to studying the extraction of phytic acid for application, we are also vigorously studying the extraction of rice bran, sesamol and other antioxidant substances from rice bran oil and sesame residue.
In addition, research is also conducted on amino acids, peptides, spices, melanoidins and various complex antioxidants. Among synthetic antioxidants, ascorbic acid and its sodium salt are safe and harmless and have significant effects. Although erythorbic acid and its sodium salt have no nutritional effect, their antioxidant effect is the same as that of ascorbic acid and its sodium salt, and the price is lower, which is conducive to further development and application. Generally speaking, an appropriate amount of antioxidants are harmless to the human body, but if too much is added, it will cause certain toxicity. Common phenolic antioxidants have very low toxicity. Compared with the oxidative deterioration of food, adding antioxidants is generally beneficial to food safety. Many natural antioxidants such as vitamins E?, C. Tea polyphenols and other tea polyphenols are not only non-toxic, but also greatly beneficial to human health, so you don’t need to panic too much about the chemical additives when purchasing food. The above is a basic introduction to antioxidant ingredients. I hope it can be helpful to you. .