科研之友
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摘要
Ultrasound was assessed as a noninvasive method of detecting dynamic transitions occurring as a scouring high ice fraction ice slurry forces liquid food products through process lines. The attenuation of ultrasound waves passing through a test section was measured within a time window that captured waves with arrival time's characteristic of a direct path through the tubing and its contents. A recording transducer measuring the attenuated signal provided an output in volts, corresponding to the extent of attenuation. Water as a comparable substitute for a liquid food product gave typical values of 2.320.07V for mean amplitude of these waves. The passage of ice slurry reduced this value to 0.75 +/- 0.03V which represented a highly significant (P<0.001) reduction in transmission. Tomato soup under similar circumstances gave values of 1.93 +/- 0.09V reduced to 0.64 +/- 0.02V when ice slurry flowed between the transducers. Dynamic transitions involving yoghurt and yoghurt mixtures were also detectable except when the yoghurt and the ice slurry shared similar degrees of signal attenuation. Pipe geometry was typically found to introduce systematic changes to recorded values but these did not detract from the basic finding that significant differences were always found between flowing food products and ice slurry, except in the case of pure yoghurt in a large channel. Noninvasive monitoring of dynamic product to ice slurry transitions in food grade steel pipes by ultrasound is readily achievable and could become a method of choice for product recovery systems. Practical ApplicationsIce slurries can be used to clean out foodstuffs from processing lines and offer the possibility of product recovery from within lines that would otherwise be lost by traditional cleaning methods such as water flushing. This process ideally needs noninvasive monitoring in real time using on-line sensors. External ultrasound transducers allow noninvasive monitoring without changes to existing infrastructure. Food grade stainless steel presents a challenge to ultrasound due to the high impedance mismatch between it and liquid food products. Knowledge of the moment of transition is an advance on rudimentary timing methods and would help to minimise wastage with prevention of contamination in recovered product. Present work demonstrates that noninvasive ultrasound can detect dynamic transitions to ice slurry within steel pipes and ducts, opening the way for automated control processes to minimise wastage and maximise product recovery.
- 出版日期2017-4
