Application of Ultrasound-Assisted Thermal Processing for Preservation and Quality Retention of Liquid Foods
Abstract:A continuously working pilot plant-scale prototype was used to evaluate the effects of continuous-flow ultrasoundtemperature treatment for bacterial decontamination of model suspensions and various liquid food systems such as milk, fruit, and vegetable juices. Escherichia coli K12 DH 5 α and Lactobacillus acidophilus were used as test microorganisms. In addition, treated juices were investigated for damage caused by heat or ultrasound-induced degradation of sensory and nutritional properties after treatment and storage. Changes in color and destruction of heat-labile and slightly oxidizable L-ascorbic acid content were monitored as an index to measure processing effects. Results were assessed with respect to the total energy requirement and compared with those using a conventional, indirect heating method having similar processing conditions. For the bacteriological process evaluation, the temperature- and time-dependent process lethality was used as the basis; for the quality- and energy-related investigations, the degree of bacterial inactivation was used. At identical degrees of bacterial inactivation, the ultrasound-assisted thermal treatments required a lower processing temperature than treatment with conventional thermal processing. However, according to energy balances, the total energy consumption was not reduced compared to conventional heating. Indications for a positive influence on shelf life, with improvements in surface color stability (lightness) and L-ascorbic acid retention, were found among quality parameters of treated orange juice.
Document Type: Research Article
Affiliations: Department of Food Biotechnology and Food Process Engineering, Berlin University of Technology, Ko¨nigin-Luise-Str. 22, D-14195 Berlin, Germany
Publication date: September 1, 2003
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