Thermal processing of raspberry pulp: Effect on the color and bioactive compounds

Abstract

The effect of heating on color degradation and the bioactive compounds, such as total monomeric anthocyanins (TMA), L-ascorbic acid (AA) and total polyphenols (TP), of raspberry pulp were investigated at 70, 80, 90 and 100 °C for 2 h. The changes in a* (redness-greenness), chroma (C*) and browning index (BI) color parameters followed a first-order reaction with activation energies of 39.39, 35.60 and 51.17 kJ mol−1, respectively. The degradation of TMA and AA also followed first order kinetics while TP did not show significant variations with thermal treatment. The activation energies of the TMA and AA changes were 28.36 and 29.47 kJ mol−1, respectively. In addition, the activation energies revealed that BI was the most sensitive parameter towards temperature changes, while the reaction rate constants (k) showed that AA had the highest degradation rate in comparison with the other parameters studied. The degradation of TMA showed a strong positive correlation with a*. The results obtained in this study may be useful to food processors for designing and optimizing thermal treatment conditions in order to obtain high quality raspberry pulp products.