Abstract : Alginate/lignin is an antioxidant biomaterial synthesized from alginate of brown algae and lignin of maize by-product by spray drying method. Alginate/lignin was evaluated for lignin content, alginate content, and its antioxidant activity according to the storage time, for example, storage at 25oC for 18 months and accelerated aging at 55oC for 137 days. The results showed that alginate/lignin was stable in content and antioxidant activity for 24 storage months. The significant decrease (p<0.05) in lignin content, alginate content, and antioxidant activity changed according to the linear model for the two storage methods. Alginate/lignin content decreased by under 3% after 24 storage months. Microorganisms of alginate/lignin increased according to the storage time and faster in the storage method at 25oC, compared to the accelerated aging method.