L-threonine

L-threonine (CAS Number 72-19-5) is one of the 20 standard amino acids found in proteins. It is classified as an essential amino acid, meaning humans cannot synthesize it and must obtain it through diet. L-threonine is a polar, uncharged amino acid containing a hydroxyl group, which contributes to its flavor-active properties. The compound is white to off-white crystalline powder with a slightly sweet taste and is soluble in water.

In the food industry, L-threonine serves multiple functions. As a flavor enhancer and flavoring agent, it contributes umami and sweet notes to food formulations, making it valuable in soups, broths, meat products, and savory snacks. It is also used as a nutrient supplement in fortified foods, beverages, and nutritional supplements to increase the amino acid profile of products. The food industry sources L-threonine primarily through bacterial fermentation using microorganisms such as *Corynebacterium glutamicum*, which is recognized as safe for food production. Additionally, L-threonine is used in animal feed formulations, particularly for poultry and swine, to optimize growth and nutrient utilization.

L-threonine has a well-established safety profile due to its status as a naturally occurring amino acid found in all protein-containing foods. The FDA has not classified L-threonine as Generally Recognized as Safe (GRAS), though this reflects the absence of a formal GRAS petition rather than safety concerns. The additive database shows zero adverse events reported to the FDA and zero recalls associated with L-threonine, indicating no documented safety issues from food use.

Scientific research supports the safety of L-threonine at typical dietary levels. As an essential amino acid, the body metabolizes L-threonine through normal amino acid metabolism pathways. The European Food Safety Authority (EFSA) has evaluated amino acids used as food additives and found them safe at levels consistent with food use. Toxicological studies on L-threonine have not identified concerns at food-relevant exposure levels. Like all amino acids, excessive supplementation beyond physiological requirements is not recommended, but this applies to intentional supplementation rather than food additive levels.

L-threonine is approved for use in food in the European Union under Regulation (EC) No 1333/2008 and is listed in the EU's Food Additive Database. In the United States, while not formally GRAS-listed, L-threonine is permitted in food under FDA regulations as a nutrient supplement and flavoring ingredient due to its natural occurrence and safety history. Japan and other major food markets similarly permit L-threonine in food applications. The additive is produced through Generally Recognized as Safe (GRAS) fermentation processes using approved microorganisms.

Research on amino acid metabolism demonstrates that L-threonine is efficiently utilized by the human body when consumed through food sources. Studies examining amino acid-supplemented foods show that L-threonine at typical additive levels (generally less than 1% by weight) does not produce adverse effects. Fermentation production methods have been extensively validated for food safety. The absence of any reported adverse events or regulatory actions across multiple decades of food use supports the safety profile of L-threonine as a food additive at permitted levels.