A recent ‘ring test’ between laboratories of various suppliers showed a wide variability between laboratories. The repetitive nature of the stirring required in the test lends itself to automation and thereby to improved reproducibility and repeatability. It was therefore decided to develop an automatic JCC test.
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Results of ring tests were evaluated by the Analysis of Variance method using the ANOVA module within a Microsoft Excel spreadsheet.
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A further ring test (The External Ring Test) was then carried out comparing the Britannia Food Ingredients results with the results obtained by three companies who supply ingredient raw materials. All carried out essentially the same British Standard test and each laboratory was asked to analyse six samples in triplicate. Although the duplicate samples included were not significantly different, there were highly significant differences among the four laboratories.
Overall, the External Ring Test showed much higher standard errors and confidence limits than found in the Internal Ring Test (Table 2). The confidence limits for Tmax, arguably the most important parameter recorded, was 0.75 compared with 0.33 for the Internal Ring Test. Some of the differences between laboratories were due to potentially controllable differences, e.g. use of metal stirrers instead of glass and lack of air conditioning, but it was concluded that the main reason for the high variability is the very subjective nature of the test.
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