Alternative processing techniques for pasteurization of liquid foods: Microwave, ohmic heating and ultraviolet light

The objectives of this study were to reduce the microbial contamination of fruit juice, different treatments were applied in order to treat microorganisms efficiently without degradation of bioactive nutrient values and to reduce unnecessary waste and time.;This dissertation is divided in five chapters: Chapter one reviews numerous studies of the impacts of batch or continuous flow ohmic and microwave heat treatments as a novel technology on nutritional values, enzymatic inactivation, and microbial destruction. Profiles during processing were needed to predict the effect of using different temperatures. Additionally, UV-light is tested an alternative to traditional pasteurization for inactivation of microorganisms.;Chapter two includes continuous flow ohmic heating for pasteurization of raisin juice. This study attempted to establish kinetic models of raisin juice inoculated with E. coli K-12 that was treated using a continuous flow ohmic heater (50, 60, 70, and 80°C) with different residence times (23 to 208 s). The results showed that continuous flow ohmic heating was more efficient compared to conventional heating at the same conditions to reduce the microbial and PME activity, and it minimized the loss of total phenolic acids and antioxidant values in raisin juice.;Chapter three covers simulation to validate the percentage of antioxidants levels and heat distribution of grape juice when pasteurized by ohmic heating with different residence times by comparing experimental data with numerical simulation. The result showed the outlet temperature profiles of 60, 70 and 80°C were similar to simulation data within 2-3°C. However, the correlation coefficient between experimental and simulation data for antioxidant levels after ohmic treatments was above of 0.92.;Chapter four aimed to investigate the effect of continuous flow microwave heating on the reduction of microorganisms in kava juice to extend the shelf life. Chemical and microbial properties of treated juice were analyzed using key parameters such as microbial counts, kavalactones, and pectin methylesterase activities. The results obtained from this chapter showed that continuous flow microwave heating was confirmed to be more efficient than the conventional method for the inactivation of microorganisms and pectin methylesterase, and there was no indicator to show significant deterioration of kava juice quality.;Chapter five involves apple juice inoculated with E. coli K-12 and exposed with pulsed ultraviolet (PUV) and non-pulsed ultraviolet (NPUV) modes as continuous and batch light treatments for 11 to 51 ml/min and 5 to 15 mins respectively. The highest log reductions of E. coli K-12 in apple juice after PUV and NPUV as continuous system were 3.35 and 3.99, respectively, at 11ml/min. Also, log reductions reached 0.85 and 1.35 in samples pasteurized by PUV and NPUV, respectively, as batch systems after 15 mins. In addition, there was no significant difference between PUV and NPUV as continuous and batch systems.