Study of Combined Ultrasound-microwave Effect on Chemical Compositions and E. coli Count of Rose Aromatic Water

Since the rose water is used in food, pharmaceutical, and cosmetic products, its microbiological control is necessary. Conventional pasteurization methods cause undesirable changes in taste, smell, medicinal properties and nutritional value with decreasing the amount of essential oil, because of high temperatures. In this study, the effects of the microwave power, temperature, ultrasound power, and ultrasonic exposure were evaluated during rose water pasteurization process on its chemical compositions and E. coli content. In order to determine the microbial inactivation by microwave and ultrasound, E. coli at a concentration of 2 × 106 per mL was inoculated to rose aromatic water. The results showed that each variable on the inactivation of E. coli and energy consumption per microbial reduction cycle had a significant effect. The optimum values of microwave power, temperature, ultrasound power, and ultrasound exposure time were obtained 326.24 W, 43.32 °C, 100 W and 4 min, respectively. The chemical composition assessment was done by GC/MS analysis. Phenethyl alcohol is one of the main components of rose water which was completely lost in the conventional pasteurization method, while in pasteurization process by combined method, it showed an acceptable decrease as compared with raw rose water. Furthermore, the proposed method caused minimal changes in the chemical compositions of the rose water as compared to the conventional heating methods.