Production of pomegranate (Punica granatum L.) juice concentrate by various heating methods: colour degradation and kinetics

Pomegranate juice was concentrated by various heating methods. The final juice concentration of 60.5 °Brix was achieved in 23, 108 and 190 min by using microwave, rotary vacuum and atmospheric heating processes, respectively. The colour change during concentration processes was investigated. Total colour differences, Hunter L, a and b parameters were used to estimate the extent of colour loss. All Hunter colour parameters decreased with time. It was observed that the severity of colour loss was higher in rotary vacuum heating process than the others. The zero-order, first-order and a combined kinetics model were applied to the changes in colour parameters. Results indicated that variation in TCD followed both first-order and combined kinetics models, and parameters L, a and b followed only combined model.