Lactic acid is an important organic chemical compound with a global production of 275,000 tonnes per year and naturally available in humans and animals. Lactic acid is also known as milk acid and primarily found in milk products. Lactic acid plays an important role in biochemical processes and was first isolated in 1780 by the Swedish chemist Carl Wilhelm Scheele. Lactic acid is a carboxylic acid and is formed by exertion of glycogen by muscle cells in the human body. In 1856, Louis Paster found that microorganism Lactobacillus plays an important role in the manufacturing of Lactic acid. Lactic acid acid fermentation is considered as one of the important mechanisms in the food industry for its sour taste, improved microbiological stability and safety of food.
Lactic acid is produced on an industrial scale by fermentation or a synthetic method.
The fermentation process requires carbohydrates, nutrients, and a microorganism to produce lactic acid via fermentation. The carbohydrates used in fermentation consist mainly of hexoses or compounds which can be easily split into hexoses, e.g. glucose, and sugar. The nutrients required include soluble peptides and amino acids, phosphates and ammonium salts, and vitamins. Fermentation occurs between 5.0 and 6.5 pH. Lime, calcium carbonate, ammonium hydroxide, and sodium hydroxide are typically used to neutralize the lactic acid produced to maintain constant pH. Thus, calcium lactate, ammonium lactate, or sodium lactate salts are formed in the fermentation broth. Lactic acid yields are between 85 and 95% based on fermentable sugars. After fermentation, the lactic acid broth needs to be purified for its intended use.
Chemical Synthesis: The commercial process is based on lactonitrile. It involves base-catalyzed addition of hydrogen cyanide to acetaldehyde to produce lactonitrile. This is a liquid-phase reaction and occurs at atmospheric pressures. The crude lactonitrile is then recovered and purified by distillation and is hydrolyzed to lactic acid using either concentrated hydrochloric or sulfuric acid, producing the corresponding ammonium salt as a by-product. This crude lactic acid is esterified with methanol, producing methyl lactate. The latter is recovered and purified by distillation and hydrolyzed by water under acid catalysts to produce lactic acid, which is further concentrated, purified, and shipped under different product classifications, and methanol, which is recycled
Lactic acid is able to nourish the skin, used as a wet agent, and PH regulator.
Lactic acid is used in detergent industry as a good descaler property, soap-scum remover and as a natural antibacterial agent.
Lactic acid is found in a wide range of food applications such as bakery products, beverages, meat products, confectionery, dairy products, salads, dressings, ready meals, etc. In food industry, lactic acid is used as a pH regulator, preservative and as a flavoring agent. In the meat industry, lactic acid is used in the form of sodium or potassium lactate to extend shelf life, control pathogenic bacteria enhance, protect meat flavor, improve water binding capacity and reduce sodium. Lactic acid is used in the beverage industry to convert the naturally present malic acid to lactic acid and to reduce the sharpness. Lactic acid is used in preventing spoilage of preserved food vegetables and other preserved vegetables in brine solution. Lactic acid can also act as a preservative for salads and dressings for maintaining microbial stability and safety. Lactic acid is used to enhance natural savory flavors. In confectionery and dairy products, lactic acid is used in enhancing mild acid taste, improvement of quality, reduced stickiness and longer shelf life. Lactic acid can act as an excellent acidification agent for many dairy products.
Lactic acid can be used in the production of new pesticide, environmental protection as it has a high biological activity in soil and crop and is non-toxic.
Lactic acid is used in the tobacco industry as it can improve the quality of tobacco and maintain the humidity of tobacco. Lactic acid can also be used to produce biodegradable plastics.