Real-time process control for food processors

Real-time process control for food manufacturing has come closer, due to pioneering research work at University College Dublin into viscosity measurement techniques for characterising the flow and mixability of highly non-Newtonian fluids. At the heart of the researchers’ experiments is the TorqSense transducer made by Sensor Technology in Oxon, which monitors the constantly changing flow characteristics of materials as diverse as tomato sauce, chocolate, pasta sauce and chicken tikka massala as they are mixed.

Many foods are presented in a sauce or as a neo-liquid and can be produced in a process-type environment. But to date, real-time control has been virtually impossible due to the non-uniform nature of the food, which may contain particulates, fibres, vegetables, meat, nuts, raisins, biscuits, etc.

Real-time process control is vital if food processors are to achieve the ultimate in product quality, but to achieve this the sensor has to be able to detect the changes with sufficient sensitivity, yet be robust enough for regular wash-downs and general industrial abuse. Of course it must not compromise hygiene standards and regimes either.

TorqSense uses surface acoustic waves (SAW) techniques to provide non-contact monitoring of instantaneous rotary torque, allowing accurate modelling of the instantaneous load changes. It is, in effect, a frequency-dependent strain gauge operating at ultrasound frequencies and consists of a transducer mounted on the mixer’s rotating shaft to monitor variations in its resonance frequency as the torsional load varies. An RF (radio frequency) link is used for wireless transmission of signals to an adjacent pick-up so that rotation is unhindered.

TorqSense embraces all the advantages of SAW technology, including no load imparted to the drive mechanism under investigation, a broader signal bandwidth than other analog-based technologies and elimination of electronic interference.