Non-destructive detection of tea stalk and insect foreign bodies based on THz-TDS combination of electromagnetic vibration feeder

Background and objectives:Current technology of X-ray imaging can recognize hard foreign materials(FMs)such as metal and high-density plastic.However,low-density foreign bodies are still a challenge for food quality and safety assessment.Materials and methods:An electromagnetic vibration feeder aided by terahertz time-domain spectroscopy(THz-TDS)and imaging was inves-tigated for non-destructively detecting tea stalk and insect FMs mixed with tea leaves.Results:THz time-domain signals were employed directly to develop the K-nearest neighbor model with a precision of 100%,accuracy of 95.6%and recall of 98.7%in predicting the unknown samples.High contrast THz-TDS images were obtained by the separation method for the samples using electromagnetic vibration feeder.The characteristic parameters of the ratio of maximum length(L)to maximum width(W)and hue extracted from THz-TDS images indicated significant difference between tea leaves and FMs.Conclusions:The results suggested that electromagnetic vibration feeder combination with THz-TDS was feasible for detecting FMs in fin-ishingteaproducts.