An innovative fiber structure has been developed to detect food additives, incorporating a hexahedral core and octagonal cladding air cavities. The effectiveness of the design was assessed through numerical simulations conducted using COMSOL Multiphysics software. The simulations utilized saccharin, sorbitol, and butyl acetate as analytes, covering frequencies ranging from 0.80 THz to 3.00 THz. A thorough analysis of key optical parameters, including power fraction, confinement loss, relative sensitivity, etc. is performed to estimate the sensor’s functioning. Notably, at the optimum frequency of 1.00 THz, the sensor design exhibited significant relative sensitivities such as 87.98% for saccharin, 89.80% for sorbitol, and 85.90%, for butyl acetate. Furthermore, the confinement loss was remarkably low for saccharin at 5.02 × 10^− 08 dB/m, sorbitol at 6.15 × 10^− 08 dB/m, and butyl acetate at 5.50 × 10^− 08 dB/m at 1.00 THz. Those parameters suggest that the proposed food chemical sensor is well-suited for real-world sensor technologies, based on the insights derived from this study.