Nondestructive detection of insect foreign bodies in finished tea products using THz-TDS combination of baseline correction and variable selection algorithms

Current technology of x-ray imaging detects hard foreign bodies (metal)effectively and extends to plastic, however, soft foreign bodies regarded as undetectable to x-ray imaging is still a challenge for food safety. Terahertz time-domain spectroscopy (THz-TDS) combined with baseline correction and variable selection were employed to discriminate insect foreign bodies in finished tea products. Compared with THz-TDS absorption coefficient, the accuracy was improved from 88.6% to 97.7% by the use of THz-TDS time-domain signals combined with adaptive iteratively reweighted penalized least squares (AirPLS) and Monte Carlo uninformative variable elimination (MC-UVE) algorithms. Conversely, variable selection algorithms failed to improve the performance of partial least square discrimination analysis (PLS-DA) model. The results suggested it was feasible to detect insect foreign bodies mixed in the finished tea products using THz time-domain signals combined with baseline correction and variable selection algorithms. This work provided an alternative method for low-density food foreign bodies detection using THz-TDS technology.Practical applications: THz time-domain signals directly applied to calibrate and predict during insect foreign bodies detection without consideration of additional parameter of sample thickness. THz-TDS system could fix to the tea packaging line for foreign bodies detection and control.