Sterilization of liquid foods by pulsed electric fields–an innovative ultra-high temperature process
نویسندگان
چکیده
The intention of this study was to investigate the inactivation of endospores by a combined thermal and pulsed electric field (PEF) treatment. Therefore, self-cultivated spores of Bacillus subtilis and commercial Geobacillus stearothermophilus spores with certified heat resistance were utilized. Spores of both strains were suspended in saline water (5.3 mS cm(-1)), skim milk (0.3% fat; 5.3 mS cm(-1)) and fresh prepared carrot juice (7.73 mS cm(-1)). The combination of moderate preheating (70-90°C) and an insulated PEF-chamber, combined with a holding tube (65 cm) and a heat exchanger for cooling, enabled a rapid heat up to 105-140°C (measured above the PEF chamber) within 92.2-368.9 μs. To compare the PEF process with a pure thermal inactivation, each spore suspension was heat treated in thin glass capillaries and D-values from 90 to 130°C and its corresponding z-values were calculated. For a comparison of the inactivation data, F-values for the temperature fields of both processes were calculated by using computational fluid dynamics (CFD). A preheating of saline water to 70°C with a flow rate of 5 l h(-1), a frequency of 150 Hz and an energy input of 226.5 kJ kg(-1), resulted in a measured outlet temperature of 117°C and a 4.67 log10 inactivation of B. subtilis. The thermal process with identical F-value caused only a 3.71 log10 inactivation. This synergism of moderate preheating and PEF was even more pronounced for G. stearothermophilus spores in saline water. A preheating to 95°C and an energy input of 144 kJ kg(-1) resulted in an outlet temperature of 126°C and a 3.28 log10 inactivation, whereas nearly no inactivation (0.2 log10) was achieved during the thermal treatment. Hence, the PEF technology was evaluated as an alternative ultra-high temperature process. However, for an industrial scale application of this process for sterilization, optimization of the treatment chamber design is needed to reduce the occurring inhomogeneous temperature fields.
منابع مشابه
Perspective of Micro Process Engineering for Thermal Food Treatment
Micro process engineering as a process synthesis and intensification tool enables an ultra-short thermal treatment of foods within milliseconds (ms) using very high surfacearea-to-volume ratios. The innovative application of ultra-short pasteurization and sterilization at high temperatures, but with holding times within the range of ms would allow the preservation of liquid foods with higher qu...
متن کاملApplication of pulsed electric field in non-thermal processing of milk
Pulsed electric field (PEF) is an innovative non-thermal technology which could be used as an alternative to the traditional thermal process to inactivate the microorganisms and enzymes in liquid foods such as milk. Compared to thermal processing, the PEF process is considered more energy efficient as the microbial or enzymatic inactivation is achieved at ambient or mild temperatures by the app...
متن کاملConventional and Innovative Processing of Milk for Yogurt Manufacture; Development of Texture and Flavor: A Review
Milk and yogurt are important elements of the human diet, due to their high nutritional value and their appealing sensory properties. During milk processing (homogenization, pasteurization) and further yogurt manufacture (fermentation) physicochemical changes occur that affect the flavor and texture of these products while the development of standardized processes contributes to the development...
متن کامل(Ultra) High Pressure Homogenization for Continuous High Pressure Sterilization of Pumpable Foods – A Review
Bacterial spores have a strong resistance to both chemical and physical hurdles and create a risk for the food industry, which has been tackled by applying high thermal intensity treatments to sterilize food. These strong thermal treatments lead to a reduction of the organoleptic and nutritional properties of food and alternatives are actively searched for. Innovative hurdles offer an alternati...
متن کاملSimulations of Coupled Electro-, Fluid- and Thermo-Dynamics and Lactoperoxidase Inactivation during Continuous Pulsed Electric Field Treatments
Pulsed electric field (PEF) processing has been developed for the inactivation of microorganisms in liquid foods at low to moderate temperatures. The efficiency of microbial decontamination by PEF is largely dependent on the applied electric field strength, exposure time and treatment temperature. Thus, detailed knowledge of the distribution of these process parameters is essential for successf...
متن کامل