Yes, its safety when used as a food additive has been approved by the U.S. Food and Drug Administration (FDA), European Food Safety Authority (EFSA),  Joint FAO/WHO Expert Committee on Food Additives (JECFA), as well as other authorities.

FDA
We can see FDA approved disodium guanylate and disodium inosinate as a direct food additive that may be safely used as a flavor enhancer in foods. However, cannot find such information of I+G.

EFSA
Disodium 5′-ribonucleotides (E635) is listed in Commission Regulation (EU) No 231/2012 as an authorised food additive and categorized as “additives other than colours and sweeteners” (2)

Its usage level in food and beverages for human consumption needs to be re-evaluated together with IMP and GMP, which was requested since Oct, 2018. (3)

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