Investigating isothermal DSC method to distinguish between cocoa butter and cocoa butter alternatives

摘要

In the article thermal behaviours of cocoa butter and representatives of the 3 classes of cocoa butter alternative fats were investigated using isothermal DSC-method. Besides traditional parameters, Avrami transformation and polar qualification system (adapted from NIR-technique) were used for data evaluations. Using a new parameter, t_(max)~*, the influence of the temperature change could be avoided. This parameter gave 100% success in classification of the investigated confectionery fats (p<0.05). In comparison with traditional Avrami parameters such as n and lgk measured at different temperatures, a new parameter (t~*) gave the best result in distinguishing confectionery fats (approx. 71% correctly classified). The classification improved using lgk and n together (79%). Better classification could be achieved using polar qualification system. The percentage of correctly classified cases was 87.5% using either the point or the surface method (p<0.05). In every case there was a clear borderline between cocoa butter-CBE fat and CBR-CBS fats. Comparing Avrami method and PQS, it can be concluded that the latter is a more successful method in classification of unknown fat samples (pure cocoa butter alternative fats only). However PQS does not give any information about thermal behaviour of the sample.