Aliatul Najwa Binti Ramli, , creator author. text my 2025 2025 monographic eng xiii, 58 pages : illustrations ; Vitamin C can degrade easily when reacting with environmental factor like heat, light and oxygen. Hence the use of preservatives is important to ensure the quality and the shelf-life of the product. Preservatives that is often use is synthetic preservative. However it may give adverse side effets to the consumer. Thus, this scenario had lead to the increasing demand for the use of safer and more natural option to replace the synthetic preservatives by replacing them with natural preservatives. In this study, peppermint oil was choosen as natural preservatives due it antimicrobial properties. This research focus on investigating the impact of various concentrations of peppermint oil on the physicochemical properties of ascorbic acid syrup and to determine the optimal concentration of peppermint oil for maintaining the quality and stability of ascorbic acid syrup. To achieve these objective, four sample of ascorbic acid syrup with different concentration of natural preservatives is formulated (0.25% v/v, 0.50% v/v, 75% v/v and 1.0% v/v). After that, testing was done on each sample to know the quality and stability of the ascorbic acid with the natural preservative choosen for four weeks. The test conducted were pH, density,viscosity at four different temperature (20°C,30°C,40°C and 50°C) and iodometric titration to know the content of Vitamin C of the sample over time. Based on the result, it is shown that pH of all samples showing icreasing trend due to the alkaline properties of the ascorbic acid. The sample 1.0% have the highest pH among all sample due to the high concnetration of peppermint oil. Density show decreasing trend where it as the concentration of peppermint oil increase the density value is decrease. The desity test also shows something is wrong with the ascorbic acid syrup formulation since all the sample have low density value than the recommended by the pharmacopea(1.1-1.3g/ml). Additional formulation adjustment will be needed to achieve better quality for consumer compliance. Viscosity test on the other hand, shows increasing trend over the rise of concentration of peppermint oil at room temperature. All sample also shows to have stable decrease in viscosity across the tempertaure rise where all sample shows to be in range stated by the authorities. Furthermore, as concnetration of peppermint oil increase from 0.00% to 0.75% peppermint oil, the content of ascorbic acid remain stable over time and have a lower percentage losses over time. However, at higher concentration of peppermint oil (1.0%) the trend shows that it have lower effectiveness in preserving the ascorbic acid content than sample 0.75% v.v/ where this possible happen due to diminishing return or potential destabilizing effects to the ascorbic acid syrup. Hence, based on the result, it is found that the most optimum concentration is 0.75%. Recommendation that can be done to improve the experiment are to optimize the formulation of the ascorbic acid syrup to imporve density, conducting long term stability test and conduct microbial test for example like Total Viable Cound (TVC) to determine the total number of viable bacteria and fungi that are present in the syrup. specialized Aliatul Najwa Binti Ramli Faculty of Chemical and Process Engineering Technology Final Year Report (Bachelor of Manufacturing Engineering Technology (Pharmaceutical) with Hons.) -- Universiti Malaysia Pahang Al-Sultan Abdullah - 2025 Include bibliographical reference Faculty of Chemical and Process Engineering Technology Dissertations Universities and colleges Dissertations Theses Dissertations THE0010765 (Local) UMPSA 260727 20260727105705.0 eng