Impact of equivalent sterilization processes with different time- temperature combinations on the chemical, physical and sensory properties of carrot juice

Thermal preservation is widely used for the stabilization of fruit and vegetable juices. However, this method can potentially impair product quality and it is necessary to categorize and quantify these changes in order to optimize the treatment process. Here, carrot juice was treated with different time temperature combinations selected to achieve equivalent microbiological lethality. Different temperatures were selected - low temperature long time (LTLT) with 90 and 95 °C and high temperature short time (HTST) with 120 and 125 °C. The thermally treated juice exhibited significant differences in physical, chemical and sensory parameters in contrast to untreated juice. HTST treatment had less of a negative effect on the juice. A significant deterioration in odor, appearance and taste was observed after the LTLT treatment compared to an untreated reference juice. The juice exhibited elevated acid taste, a shift in olfactory profile from white to red vegetables and diminished homogeneity. Significant changes in sugar composition, pH, carotenoids and color were also observed during this treatment. The juice that had been treated with LTLT exhibited a higher amount of monosaccharides, a lower pH value, a reduced quantity of carotenoids and a perceptible difference in color in comparison to the untreated and fresh juice. Therefore, it can be concluded that varying temperatures show different effects on juice quality, despite the same microbiological lethal effect. This must be taken into account when designing the pasteurization process.