What are E627, E631 and E635?
They are flavour enhancers — the ribonucleotides, used alongside monosodium glutamate to deepen savoury taste. E627 is disodium guanylate, E631 is disodium inosinate, and E635 is a blend of the two. They are authorised across the EU and UK and are not regarded as a toxicity concern.
The family is larger than the three numbers people search for. E626 is guanylic acid and E627 its disodium salt; E630 is inosinic acid and E631 its disodium salt; E634 and E635 are the calcium and sodium ribonucleotide blends. The GOV.UK/FSA register of approved additives lists every one of them under the same functional class: flavour enhancers.
What makes them worth understanding is that they are almost never used alone. Ribonucleotides are synergists — they multiply the effect of glutamate rather than contributing much taste of their own. A blend of roughly 98% monosodium glutamate and 2% ribonucleotides has been described as having about four times the flavour-enhancing power of MSG by itself. That is why E631 sits next to E621 on a crisp packet, an instant noodle sachet or a stock cube, and rarely appears on its own.
So if you arrived here after reading "E631" off a label and wondering whether it is something to worry about, the short answer is that the safety file is unremarkable. The genuinely useful question is a different one — and it is the question the number is worst at answering: what was it made from?
The part the E-number does not tell you
Disodium inosinate can be manufactured two entirely different ways. It can be produced by bacterial fermentation of sugars — the route the major manufacturers use today, the same kind of process that makes MSG from starch or molasses. It can also be prepared from animal tissue, historically meat or sardines, by hydrolysing the inosinic acid naturally present in muscle and neutralising it with sodium.
Both routes produce the same molecule, and both are labelled the same way. "E631" and "disodium inosinate" are the only words EU labelling requires, and neither carries any information about origin. There is no suffix, no asterisk, no separate code for the fermented version.
This is less a labelling oversight than a labelling philosophy. Regulation (EC) No 1333/2008 identifies additives by what they are chemically, because that is what determines their safety assessment and their permitted use levels. Origin enters the picture only for allergen declaration — and inosinate of fish origin is purified past the point where it is treated as a fish allergen — so origin falls outside what the number is designed to communicate.
The consequence is specific and worth stating plainly: a product can be free of every declared animal ingredient, carry no allergen warning, and still contain an additive of animal origin. E631 is the most common way that happens.
So is E631 vegan?
It depends on the batch, and the label cannot tell you. That is an unsatisfying answer, but it is the honest one, and the disagreement runs through the advocacy organisations too — the Vegetarian Society has treated animal-derived production as widespread, while the Vegetarian Resource Group reports that the leading manufacturers all say they ferment. Both may be describing the market accurately at different moments.
What follows practically is a rule of thumb rather than a verdict. If a product carries a certified vegan or vegetarian mark, the certifier has asked the supplier the question you cannot ask from the aisle, and the E631 in that product came from fermentation. If it does not, E631 is a reason to write to the manufacturer rather than a reason to assume the worst — or to put the packet back, if you would rather not find out.
The same caution applies, for the same reason, to a second group: people avoiding pork or fish on religious grounds. The ambiguity is identical, and so is the resolution — certification, or a direct question to the producer.
This is precisely why Ingredo.app flags E631 and E635 as a caution for the vegan profile rather than as a hard block. A hard block would claim we know the product contains an animal-derived ingredient. We do not know that, and neither does the label. A caution says the opposite and more useful thing: this one is genuinely unresolved, and here is why.
Gout, purines and the open regulatory file
There is one group for whom these additives have a real physiological relevance, and it has nothing to do with the vegan question. Inosinate and guanylate are purine nucleotides, and the body metabolises purines to uric acid. For someone managing gout or hyperuricaemia, that places foods heavy in E627, E631 and E635 in the same conversation as the other purine-rich foods a clinician will already have raised.
The quantities in a serving of crisps are small next to a plate of liver or a portion of anchovies, and nobody should reorganise a diet around a crisp packet. But if you are already tracking purine intake, the flavour-enhancer block on a label is a legitimate thing to notice, and it is not something most additive guides mention.
On the regulatory side, the ribonucleotides have never carried a numerical intake limit. Their authorisation rests on a Scientific Committee on Food assessment that set a group acceptable daily intake of "not specified" — the category regulators use when toxicity is low enough that no numerical ceiling was judged necessary. EFSA’s programme of re-evaluating older additives under Regulation (EU) No 257/2010 has reached the glutamates, where a group ADI of 30 mg per kg of body weight per day was set in 2017; the ribonucleotide review has not yet reported.
Read that as a file still open rather than a warning. "Not specified" is a favourable outcome, not a gap, and a pending re-evaluation is the system working as designed.
How Ingredo.app reads the ribonucleotides
E627, E631 and E635 are flagged for origin ambiguity, not for toxicity — and as a caution rather than a block, because the label genuinely does not settle the question.
Vegan — caution
- May be produced by bacterial fermentation, or from meat or fish
- The E-number and the additive name are identical either way
- A certified vegan mark resolves it; the ingredient list alone does not
Worth knowing if you manage gout
- Purine nucleotides, metabolised by the body to uric acid
- Small amounts per serving, but they accumulate across heavily seasoned processed foods
Not flagged by
- Any allergen module — inosinate of fish origin is purified past the point of allergen declaration
- Our additive tier — no EU ban, restriction or mandatory warning attaches to E626–E635
Frequently asked questions
Either bacterial fermentation of sugars, or animal tissue — historically meat or sardines. The major manufacturers today say they use fermentation, but both routes remain in commercial use and produce a chemically identical substance. The label shows only "E631" or "disodium inosinate," which reads the same in both cases.
Not reliably, and the ingredient list cannot tell you. Because disodium inosinate can be made from meat or fish as well as by fermentation, a product containing it is confirmed vegan only by a certification mark or by asking the manufacturer. This is the main reason a product with no visible animal ingredient can still fail a vegan check.
E627 is disodium guanylate, E631 is disodium inosinate, and E635 is disodium 5’-ribonucleotides — a blend of the other two. All three are flavour enhancers used to amplify glutamate, and all three carry the same origin ambiguity, since the inosinate portion of E635 can be animal-derived.
Because ribonucleotides are synergists rather than standalone flavourings. They boost the savoury effect of glutamate far more than they contribute taste themselves — a mix of about 98% MSG and 2% ribonucleotides has roughly four times the enhancing power of MSG alone. Manufacturers use them together to reach a given intensity with less total additive.
They are authorised additives in the EU and UK, and their approval rests on a group acceptable daily intake of "not specified" — the classification used when toxicity is low enough that no numerical limit was judged necessary. EFSA’s re-evaluation of the ribonucleotides under the additive review programme has not yet reported.
It is reasonable to be aware of it. Inosinate and guanylate are purines, which the body converts to uric acid, so heavily seasoned processed foods containing them belong in the same picture as other purine sources. The amounts per serving are modest next to organ meats or oily fish, and dietary management of gout is a conversation for your clinician.
No. E631 is a ribonucleotide, chemically unrelated to glutamate, though the two are usually formulated together. The FDA has found no conclusive evidence that MSG causes the reactions once attributed to it, and there is no separate body of evidence attributing such reactions to the ribonucleotides.
The same uncertainty applies. Because disodium inosinate can be prepared from meat, a product containing it is not shown to be free of pork-derived material by the ingredient list alone. Certification, or a direct question to the manufacturer, is the only way to establish it.