Examination of the usefulness of empirical kinetic equations for describing the formation of 5-HMF in grapefruit juice

Formation of 5-hydroxy-methyl-furfural in grapefruit juice was investigated at four temperatures and five heat-treatment time periods. Measured data were evaluated by relatively new methods: search for an adequate transformation by minimizing the ratio of variances around regression lines and within groups; applying the method of mean square of successive differences, Bartlett's test for homogeneity, unweighted and weighted regression analysis. Reaction order, according to the empirical kinetics of formation was n = 0·31. Rate constants at four temperatures and one common initial trasformed concentration were also determined. Special analysis based on the least squares method provided activation energy and reference rate constant. Original concentrations varied according to power functions of slightly autocatalytic nature.