Here, in this study, we strategically utilized low-energy mediated epitaxial deposition of Au⁰ atoms reduced by gallic acid over preformed gold nanorods (GNRs) seeds. It can be suggested that GNRs seed/Au³⁺ ratio influences the directional attachment of Au⁰ atoms to the GNRs. Alteration in the thickness of the GNRs upon deposition of Au⁰ in presence micromolar levels of antioxidant reduces the aspect ratio of the nanorods. Change in the aspect ratio altogether induces a blue-shift in the longitudinal surface plasmon resonance (LSPR) of the GNRs from the NIR region of the spectrum to the shorter wavelength. TEM imaging, DLS and zeta potential analyses confirms the morphological and surface-charge alterations after interaction with antioxidant. Based on the relation between blue-shift of the LSPR band and the concentration of gallic acid, the sensing platform achieves a linear detectable range of 1.25–35 μM with detection limit as low as 90 nM and the limit of quantification as 300 nM. The method has high selectivity against tested interferents and was found to be reproducible. The potential application of the developed sensor was validated by quantifying gallic acid in commercially available apple juice. High recovery (99.46–100.4%) was obtained, suggesting that the established assay which is reliable and facile can be successfully used for gallic acid detection real food samples. The developed method of tuning the aspect ratio of nanomaterial can be further extended for detection other anti-oxidant molecules.