PreservativeSorbic acid is also known as 2.4 hexadienoic acid and 2-propenyl acrylic acid. Structural formula CH3CH—CHCH—CHCOOH. White crystal, melting point 124.52°C. Odorless and tasteless. Soluble in ethanol, insoluble in water (15g/100g water.20℃, so there are many inconveniences in use. For this reason, it can be made Potassium salt with good water solubility and stable performance is used. Its antibacterial effect and range are the same as sorbic acid. Use sorbic acid and potassium carbonate in ethanol or aqueous solution to perform a neutralization reaction at a ratio of 1:0.5 to obtain potassium sorbate.
The preservative sorbic acid has inhibitory effects on molds, yeasts and aerobic bacteria, but it has an inhibitory effect on anaerobic Bacillus and Lactobacillus Waiting is almost ineffective. Sorbic acid is suitable for food preservatives below PH5.5, and the highest pH does not exceed 6.5. Sorbic acid and potassium sorbate can be used in soy sauce, vinegar, and jams (maximum dosage 1g/kg), low Salt soy sauce, pasta sauces, preserves, hawthorn cake, fruit juice, canned food (maximum usage range: 0-5g/kg). Fruit juices, sherbet, wine, fruit wine (maximum usage range: 0.6g/kg) ), as well as sparkling wine, soft drinks (maximum usage amount is 0, 4g/kg), etc. ADI is 0~23mg/kg body weight,
2. Production of sorbic acid and its salts
(1) Production method There are four production routes for sorbic acid, which are described below.
① Crotonaldehyde and malonic acid method. This method uses pyridine as the solvent at 90-100°C and reacts for 4 to 5 hours to obtain sorbic acid with a yield of 32%.
If calcium malonate is used instead of malonic acid, the yield can be improved.
② Crotonaldehyde and ketene method. In this method, in the presence of boron trifluoride etherate complex, Shanghai Chemical Industry uses crotonaldehyde and ketene as raw materials. It reacts at 0°C to form hexaenolactone, which is then reacted with sulfuric acid and hydrolyzed to form sorbic acid, with a yield of 70%. .
If metal oxides or carboxylates such as Zn, Cd, Ni, and Cu are used as catalysts, the yield will be improved. The United States, Japan, Germany and other countries mostly adopt this production route, but there are slight differences in catalysts and production processes.
③Crotonaldehyde and acetone method. This method uses Ba(OH)2•8H2O as the catalyst, and uses crotonaldehyde and acetone as raw materials to condense into 30% polyaldehyde resin and 70% polyaldehyde resin at 60°C. % of 3,5-dieneheptanone-2, which is oxidized with sodium hypochlorite to form 1,1,1-trichloro-3,5-dieneheptanone-2. Then react with sodium hydroxide to obtain sorbic acid with a yield of 90%, and obtain chloroform at the same time.
This process route is commonly used in my country
(1) Sorbital oxidation method. This method uses silver oxide as a catalyst and sorbaldehyde as the raw material for oxidation to produce sorbic acid.
Sorbital, the raw material, is made from the trimerization of acetaldehyde.
(2) The process flow takes the synthesis of sorbic acid from crotonaldehyde and propionic acid as an example. The process flow is shown in Figure 2-3.
Figure 2-3 Sorbic acid production process
1 – reaction kettle; 2 – condenser; 3.4 – centrifuge; 5 – crystallization kettle
In synthesis reactionKettlePut in 175kg crotonaldehyde, 250kg malonic acid, and 250KG pyridine in sequence, stir at room temperature for about 1 hour, and slowly heat to 90-100°C. React for 4 to 5 hours. After the reaction, the temperature is lowered. to below 10°C, slowly add 10% dilute sulfuric acid, and control the temperature not to exceed 20°C. Until the reactant becomes weakly acidic and has a pH of about 4 to 5, freeze, filter, and wash the crystal with water to obtain crude sorbic acid. Then use Recrystallize 3 to 4 times the amount of 60% ethanol to obtain about 75kg of sorbic acid. Neutralize with potassium carbonate or potassium hydroxide to obtain potassium sorbate.
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