Transient heat modeling for non-destructive assessment of boiled eggs

It is not possible to differentiate between hard-boiled and soft-boiled eggs after processing. Therefore, transient heat of boiled eggs was tested during the production process in order to develop a model that could be used to differentiate between soft-boiled and hard-boiled eggs. Both types of boiled eggs (N=214) were produced in water at 90 °C for different times and then cooled down. The temperature gradients due to heat transfer during cooling in the ambient air were measured every 30 seconds. Results showed that a dimensionless parameter, called number of transfer units (NTU), changed in relation to time during the cooling process, and it was shown that this could be used as an independent variable. Classification models were established using linear discriminant analysis (LDA) and support vector machine classification (SVMC). Samples were divided into a calibration set (N=150) and a prediction set (N=64). The predictive accuracy of the models using LDA and SVMC for classifying eggs into soft-boiled or hard-boiled was 93.8% and 92.2%, respectively. Therefore, it was concluded that the classification models using LDA and SVMC had potential for use as a non-destructive method for classifying groups of eggs into soft-boiled and hard-boiled that could potentially be used in a commercial situation.