A process for producing an oxidized nanofibrillar cellulose hydrogel is disclosed, wherein the process comprises oxidizing cellulose pulp fibers in the presence of hypochlorite as an oxidant and a heterocyclic nitroxyl radical as a catalyst； and disintegrating the oxidized cellulose pulp fibers to obtain a nanofibrillar cellulose hydrogel； wherein all steps of the process after oxidizing are performed under aseptic conditions. An oxidized nanofibrillar cellulose hydrogel and a system for producing the same are also disclosed.
