To improve the shelf life of low-salt Kochujang, Korean hot pepper paste, antimicrobial materials were added at different times before and after aging. The kochujang was then packaged and stored at $30^{circ}C$ for 15 weeks, and changes in microbiological and physiochemical properties were evaluated. Hunter a- and b-values decreased considerably during storage. The total color difference (${delta}E$) was greater in the ethanol-chitosan (EC) treatment than in the control and after pasteurization (A-P) treatment. Gas was produced until the seventh week of storage. The control and the A-P treatments produced more gas than the other treatments, and these had the largest number of yeasts and aerobic bacteria. The pH of the EC treatment was higher than that of the other treatments, and the A-P treatment had the highest level of titratable acidity. During storage, the oxidation-reduction potential was lower in the EC and ethanol-mustard-chitosan (EMC) treatments. The reducing sugar content decreased remarkably in the control and A-P treatments, with high production of ethanol. There was a significant change in the content of amino-type nitrogen in the control and A-P treatments, and the content of ammonia-type nitrogen was lowest in the EMC treatment. In the sensory test of kochujang, the ethanol-mustard (EM) and ethanol (E) treatments were significantly higher than the EC, control, and A-P treatments (p <0.05). EM or E alone was effective in extending the shelf life of kochujang when added before aging.