Disodium inosinate

Disodium inosinate (E631 ) is the disodium salt of inosinic acid with the chemical formula C10H11N4Na2O8P. It is used as a food additive and often found in instant noodles, potato chips, and a variety of other snacks.

Commercial disodium inosinate may either be obtained from bacterial fermentation of sugars or prepared from animal products. The Vegetarian Society reports that production from meat or fish is more widespread, but the Vegetarian Resource Group reports that all three "leading manufacturers" claim to use fermentation.

Use as a food additive
Disodium inosinate is used as a flavor enhancer, in synergy with monosodium glutamate (MSG) to provide the umami taste. It is often added to foods in conjunction with disodium guanylate; the combination is known as disodium 5′-ribonucleotides.

As a relatively expensive product, disodium inosinate is usually not used independently of glutamic acid; if disodium inosinate is present in a list of ingredients, but MSG does not appear to be, it is possible that glutamic acid is provided as part of another ingredient or is naturally occurring in another ingredient like tomatoes, Parmesan cheese, or yeast extract.

Origin
Inosinate is naturally found in meat and fish at levels of 80–800 mg/100 g. It can also be made by fermentation of sugars such as tapioca starch.

Some sources claim that industrial levels of production are achieved by extraction from animal products, making E631 non-vegetarian. However, an interview by the Vegetarian Resource Group reports that all three "leading manufacturers" (one being Ajinomoto) claims to use an all-vegetarian fermentation process. Producers are generally open to providing information on the origin. E631 is in some cases labeled as "vegetarian" in ingredients lists when produced from plant sources.

Toxicology and safety
In the United States, consumption of added 5′-ribonucleotides averages 4 mg per day, compared to 2 g per day of naturally occurring purines. A review of literature by an FDA committee found no evidence of carcinogenicity, teratogenicity, or adverse effects on reproduction.

In 2004, disodium inosinate was proposed to be removed from the food additive list by Codex Alimentarius Commission. This change did not go through: it is still present in the 2009 Codex Alimentarius list.