A breakthough in liquid engineering

Related tags Viscosity

Research work at University College Dublin has brought real time
process control for food manufacture a significant step closer. The
study into viscosity measurement techniques for characterising the
flow and mixability of highly non-Newtonian fluids could allow food
manufacturers to better understand the changes in food with
sufficient sensitivity, writes Anthony Fletcher.

The scientists believe that the research could represent a breakthrough in food production. Many foods are presented in a sauce or as what physicist could describe 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,"​ said PJ Cullen, who leads the research team. "To achieve this the sensor has to be pretty special 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."

Cullen and his colleagues have simulated food processing techniques in a number of different laboratory rigs, one of the most used being a helical ribbon mixer similar to those employed by manufacturers for mixing ingredients together. Often the key requirement is to mix sufficiently to achieve a uniform dish, but not to waste time and energy by over-mixing.

"We do this by monitoring the torque on the mixer's shaft, as it will move to a steady state (within the characteristics of the given recipe) once fluid uniformity is achieved,"​ he said.

A central component of the researchers' experiments is the Torqsense transducer made by UK-based Sensor Technology. The equipment monitors the constantly changing flow characteristics of materials as diverse as tomato ketchup, chocolate, pasta sauce and chicken tikka massala as they are mixed.

Torqsense uses Surface Acoustic Waves 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.

Ireland's national economy has always had a strong agricultural element. In recent years, considerable value has been added to this by the nation becoming one of Europe's foremost manufacturers of processed ingredients and ready meals.

Related topics Processing & packaging

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