21 C.F.R. § 172.620
The food additive carrageenan may be safely used in food in accordance with the following prescribed conditions:
(a) The food additive is the refined hydrocolloid prepared by aqueous extraction from the following members of the families Gigartinaceae and Solieriaceae of the class Rodophyceae (red seaweed):
Chondrus crispus. Chondrus ocellatus. Eucheuma cottonii. Eucheuma spinosum. Gigartina acicularis. Gigartina pistillata. Gigartina radula. Gigartina stellata.
(b) The food additive conforms to the following conditions: