Colorimetric flow visualization of in-package pasteurization.

Brandon, H., Puskarz, S. and Gardner, R.

Abstract
A method has been devised that makes visible the movement of liquid within a bottle during tunnel pasteurization. Bottles are filled with distilled water at pH 9 and a mixed pH indicator solution containing Thymol Blue and Bromocresol Green is added to form a boundary layer at the bottom of the bottle. As the solution within the bottle moves under the influence of thermal currents etc., this movement is shown by colour changes over the range red, orange, yellow, green and blue. Photographs show the colour changes during pasteurization. The flow pattern is divided into four primary regions: a mixing region at the top, a main core, a boundary layer rising along the wall and a layer near the bottom of the container in which thermals rise from the heated surface. Changes occurring in these regions allow the degree of mixing to be measured quantitatively. Features of the flow field previously undetected have now been measured. Colorimetric flow visualization should find extensive application in the brewing industry for the investigation of processes that involve heating, cooling, mixing and filling.
Keywords : analysis bottle content distribution flow pasteurisation