Flexible SERS sensors nowadays are promising detection tools due to their facile utility in terms of onsite inspections and their safe disposal after use. Noble plasmonic gold nanoparticles (AuNPs) being the icon of SERS sensors have been immobilized on flexible substrate based on polymer polycarbonate (PC) with the physical vapor deposition process (PLD). Fine control of AuNPs decoration within the PC substrate was obtained by varying the laser number of pulses from 200 to 5000 number of pulses (NLP). Characterization of morphology, structural and optical properties of the fabricated Au-PC sensor were investigated with sophisticated analytical instruments. Rhodamine 6G test molecule were used to identify the optimum deposition condition leading to the best SERS sensitivity. The highest SERS activity was for sensors prepared with 3000 NLP (Au-PC 3000NLP). Furthermore, the efficiency of the designed sensor was tested against the detection of a food additive like Butylated Hydroxylanisole (BHA) with various concentrations, ranging from 1000 to 10ppm. The developed flexible SERS sensor exhibited an ultra-low detection level of BHA down to 10 ppm, which is very low compared with reported literatures. In conclusion, it was demonstrated that the developed Au-PC flexible SERS sensor could be employed in real-life applications related to food safety for rapid on-site verifications to maintain food quality as well as public health.