Another concept involves a cylindrical bar of titanium with opposing piezoelectric transducers attached at each end. One such system consists of a hollow tube sealed at one end and driven at the other by a standard piezo transducer.
Generally, commercial tube reactors are constructed of stainless steel and the choices for pipe cross-section are rectangular, pentagonal, hexagonal and circular.Īn alternative arrangement is via the coaxial insertion of a radially emitting bar into the pipe containing the flowing liquid this would require minimal change to existing pipework. In this way the sound energy generated from transducers bonded to the outside of the tube is transferred directly into the flowing liquid. Essentially the liquid to be processed is passed through a pipe with ultrasonically vibrating walls. The systems that are particularly suitable for general usage in the food industry are resonating tube reactors. This results in lengthy processing times to achieve pasteurization and so few companies will process viscous foods without agitation. The effect is to form an insulating layer that impairs heat transfer if there is no mixing inside the containers. Irrespective of the method used, heat transfer from the media to the product thermal center is poor, because of the viscous boundary layers that develop on the inside surface of the containers.
The disadvantage is that the containers need to be strong enough to withstand high temperatures (80–100☌) and the swings in pressure differential. The advantage of the former method is that both food and container are pasteurized during the process, which allows the integral package to be commercially sterile and the potential shelf life extended. a closed vessel) and fill into individual containers. G Tucker, in Encyclopedia of Food Sciences and Nutrition (Second Edition), 2003 Batch Processing Considerationsīatch systems fall into two main categories, the most common being where the viscous food is pasteurized in its container, and the alternative is to carry out the processing within a large container (e.g.