Kinexus rheometer capabilities are really something to chew on
Written by: Steve Carrington
Thinking back to those early design meetings that the development team here at Malvern undertook at the inception of the Kinexus rheometer project, one of our key aims was to deliver a new rheometer platform that enabled total flexibility of control – to provide unique test capabilities that went beyond those previously available on rotational rheometer systems.
Market feedback was telling us that Industrial users would like the option to run under Standard Operating Procedure (SOP)-driven protocols, with ‘locked down’ tests that included specific user instructions and inputs to meet their particular requirements. At the other extreme, University researchers were asking for a completely open ‘programming-type’ test capability that would allow them to link instrument or rheological actions together in ways that ‘thought experiments’ allowed, but not their rheometer interface. Our challenge was to try to reconcile these requirements!
Two key ideas implemented on the Kinexus platform helped to facilitate the above. Firstly, the essential rheometer functions – rotational system (torque, speed and position); vertical system (gap and normal force); temperature system – are independently configurable and controllable, and interconnected by a synchronous, high speed raw data stream. Secondly, the rSpace software is driven by ‘sequences’ – which consist of fundamental rheological actions (or test building blocks) that can be linked together with other test actions, such as user feedback and choices, calculate values, loops and triggers, in order to build ‘intelligent’ tests. Set a sequence to be ‘run’ only, and a user operates under SOP-type conditions. With access to ‘edit’ sequence functionality, then researchers have the full design capabilities at their fingertips. Well, at the click of a mouse and with ‘drag and drop’ operation anyway.
It’s fascinating to see how our users are exploiting this control flexibility that Kinexus enables – take this recently published paper from Prof. Julian McClements’ group at Dept. of Food Science at the University of Massachusetts, Amherst, and ConAgra Foods, entitled ‘Instrumental mastication assay for texture assessment of semi-solid foods: Combined cyclic squeezing flow and shear viscometry’. Now that’s quite a mouthful, but what these researchers have done is developed a ‘mastication’ sequence in rSpace based on a combination of squeezing flow and shear viscometry cycles which is designed to mimic aspects of oral processing – or more simply, they’ve made a Kinexus ‘chew’!
The vertical system is programmed with compression (squeeze flow) and decompression stages at speeds which mimic the motion of the mouth, and the rotational system is programmed with a shear rate to mimic conditions occurring in the mouth during mastication. Repeat cycles depend on how long you typically chew a particular food type. Real oral conditions can be further simulated with the use of artifical saliva in the experiments.
Food types, including model systems were characterized rheologically in the first instance, and then subjected to the mastication sequence. The data obtained contains a variety of features that can be related to material properties, such as yield stress and elongational viscosity. The mastication sequence is effectively a tool that provides additional information related to changes in the textural attributes of semi-solid foods during chewing. By analysing material properties and textural attributes of foodstuffs, these can subsequently be correlated with sensory analysis and consumer attributes such as ‘thickness’, ‘creaminess’ or ‘smoothness’ of foods, and ultimately improved consumer satisfaction!
It is the control attributes of the Kinexus platform that opens up such test flexibility, offering capabilities beyond the norm for rheological analysis. What could that do for your sample testing? Food for thought maybe……