This study tended to construct new L-ascorbic acid (LAA) composites in low toxicity and high stability for feasible application. LAA is chemically very unstable, since it is easily oxidized into biologically inactive compounds naturally. Our finding showed that introduction of montmorillonite (MMT) could significantly attenuate its toxicity and to sustain the stability of LAA with economic feasibility for practical uses. In addition, as phosphoric acid was biologically compatible, it was used for the pretreatment of MMT to obtain a promising stabilization of LAA. Toxicity assessment also showed that MMT treated with low-concentration acids should be considered as biologically safe according to our assessment. Thus, using acid treated MMT to stabilize LAA in a long-term might be technically feasible for further uses. (c) 2008 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.