DUAL‐MODE COMBINED INFRA RED AND AIR‐COUPLED ULTRASONIC TECHNIQUE FOR REAL‐TIME INDUSTRIAL PROCESS CONTROL WITH SPECIAL REFERENCE TO THE FOOD INDUSTRY

This paper describes the use of air‐coupled ultrasound and Near Infra red (NIR) as complimentary techniques for food quality assessment. A major study has been performed, in collaboration with four industrial food companies, to investigate the use of air‐coupled ultrasound and NIR to both detect foreign bodies, and to measure certain parameters of interest, such as the amount of a certain additive. The research has demonstrated that air‐coupled ultrasound can be used in on‐line situations, measuring food materials such as chocolate and cheese. It is also capable of performing measurements on moving sealed metal cans containing food, and is able to detect foreign bodies with the top removed, as encountered just before sealing. NIR has been used as a complimentary technique to test food materials where propagation of air‐coupled ultrasound was found to be difficult. This could be due to the presence of air pockets within the food material, as in the case of bread dough.