Sorbic acid «E200» and its salts like potassium sorbate «E202» are commonly used as preservatives in food. Potassium sorbate may find more frequent applications because of its greater solubility in water. Moreover, Researches during the 1950s demonstrated the impressive effectiveness of sorbate against many microorganisms such as bacterial species, yeasts and molds…. However, microbial inhibition by sorbate is variable, which could lead to defective food products. This study is focused on the investigation of antimicrobial activity of potassium sorbate in presence of numerous microbial species, in different concentrations of sorbate, pH and temperature, in order to define the suitable conditions. Potassium sorbate has been provided by QUIMIDROGA, LC-MS analyze confirmed its purity. The product has been then characterized by X-ray, ATR, UV and 1H-RMN. For the first time, the optimized geometry of potassium sorbate was approved with the Gaussian 09 software using DFT functional. The theoretical vibrational frequencies and optimized geometric parameters have been calculated using (DFT/B3LYP-D3), (DFT/M05-2X) and (DFT/M06-2X) with 6-311+G(d) basis set. Considerable level of correlation with the corresponding experimental results has been noticed when using DFT/M06-2X with 6-311+G(d) basis set (R2 = 0.99913). Furthermore, TD-DFT approach and NBO analyzes were used to explore the excited states of sorbate anion in liquid phase, using SMD model. NMR chemical shifts of the molecule are determined by the gauge independent atomic orbital method. Nucleophilic sites are found by molecular electrostatic potential. HOMO, LUMO and HOMO-LUMO gap, recorded from -6.30 to 1.55 eV, are used to calculate global reactivity descriptors according to FMO theory. The results show that charging easily transfers in sorbate, and this affects its biological activity, which can explains experimental results on antibacterial and antifungal activities.