Yes, its safety used as a food additive has been approved by the U.S. Food and Drug Administration (FDA). Plant protein products are approved by the FDA 21CFR§170.3.

What are the Possible Health Risks?
It is common that sometimes consumers have questions whether hydrolyzed soy protein or HVP is bad for our health and what are the side effects. The possible side effects lie on MSG and 3-MCPD.

MSG
As HVP contains MSG so MSG symptom complex is a possible side effect for people allergic to it.

3-MCPD
3‐MCPD (3-monochloropropane-1,2-diol or 3-chloropropane-1,2-diol) is also known as chloropropanols. It has been reported to be carcinogenic, nephrotoxic, and reproductively toxic.

It is formed in the production of acid-HVP, which needed to heat at high temperatures for hours. It is the by-product by the reaction of the lipids in the soy protein with chloride.

3-MCPD is found in soy sauce and other related products with added acid-HVP while the naturally fermented soy sauce almost without it.

http://www.chinafooding.com/Soy_Protein_Concentrate