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
Safety
Fumaric acid and its calcium, ferrous, magnesium, potassium, and sodium salts may be safely used in food. (11)

Uses
It can be used for antimicrobial agent, curing or pickling agent, flavoring agent or adjuvant, leavening agent and a PH control agent in food. (12)  

EFSA
In food
Fumaric acid (E297) is listed in Commission Regulation (EU) No 231/2012 as an authorised food additive and categorized as “additives other than colours and sweeteners” (13)

Uses

The following foods may contain with E297 and its maximum level (14):

Food Category    Maximum Level
Fruit-flavoured desserts    4000
Sugar confectionery    1000
Chewing gum    2000
Decorations, coatings and fillings    1000
Fillings and toppings for fine bakery ware    2500
Instant products for preparation of flavoured tea and herbal infusions    1000
Gel-like desserts, fruit-flavoured desserts, dry powdered dessert mixes    1000
In feed
Fumaric acid is currently authorised as a preservative in feedingstuffs for all animal species. It is considered safe for pigs and poultry provided that an expected use level of 20 000 mg/kg in complete diets for pigs and poultry is not exceeded. (15)

UK Food Standards Agency
Categorized in “Others” (16)

Food Standards Australia New Zealand
It is an approved ingredient with the code number 297 in Australia and New Zealand. (17)

JECFA
Function class: food additive, flavouring agent, acidity regulator. (18)

Acceptable daily intake: ADI “not specific” set in 1989 and no safety concern at current levels of intake when used as a flavouring agent in the safety re-valuation in 1999. (19)

 

http://www.chinafooding.com/Fumaric_Acid