The Sonochemistry Centre at Coventry University has a background of research into many different aspects of the effects of ultrasound in chemistry and processing.

Coventry University Sonochemistry Department

Among these are:

  • Chemical synthesis
  • Electrochemistry
  • Food technology
  • Fundamental studies of acoustics
  • Material processing
  • Materials extraction
  • Reactor design and modeling
  • Therapeutic ultrasound
  • Water treatment

It is the interest in the chemical and biological remediation of yeast in beer that has led us to embark on this project involving a preliminary laboratory assessment of the use of  frequency waves in the treatment of beer and lager.

Research into the use of ultrasound in environmental protection has received a considerable amount of attention with the majority of investigations focusing on the harnessing of cavitation effects for the destruction of biological and chemical pollutants in water.

Experimental Set Up

It was the view of the team that it would be impossible to mimic precisely the conditions pertaining to the installation of the StayClean System in a working cellar’s beerlines. It was necessary to construct a system that could not only be used in the laboratory but also cleaned (i.e. sterilised) regularly. To this end four radiofrequency coils were wound onto a 20 inch long sleeve of plastic tubing internal diameter 1 inch. The sample of yeast

(Candida utlis)  was then placed in a plastic tube of just under 1 inch diameter that served as the reaction vessel. This tubing could then be readily demounted and sterilized as required.

Suspensions of a yeast (Candida utlis) in a normal saline were exposed to radiowaves in a static (non-circulating) apparatus. Microbial suspensions were contained in the inner plastic tube (45ml volume) which was then inserted into the outer tube wrapper with 4 coils. The radiowave emitted cycled systematically across a range of frequencies, and its activity was confirmed by the use of a radio receiver that emitted an audible “buzz” in close proximity to the coils.

The effects of short and long term periods of exposure were studied by assessing:

  • Microbial viability, under normal and enhanced pressure, was assessed through the determination of biable counts. (Samples were taken periodically from the bottom of the inner tube, or from three sections within the tube).
  • Adhesion to surfaces, and the physical arrangement of cells in suspension (aggregation) was studied using microscopical examination.

Research Outcomes

Experiments using yeast showed that when exposing the cultures to radiowave using the radiowave emitter there were few clusters of cells and more single separated cells, in comparison to not using the radiowave emitter. There appeared to be a reduction in the formation of cell clumps in suspension. Adherent cells were less clustered or clumped in radiowave treated samples.

Time (h)

Untreated

Treated

0

Lots of cells in single and clustered form

Lots of cells in single and clustered form

1

Long chains of clustered cells separating into some single cells

Small clusters of cells and some single cells scattered

2

Long chain of cells with few single cells

Evenly spread single cells with small clusters

3

Few large clusters with some single cells

Lots of evenly spread single cells

4

Thin long strands of cells, and some single cells

Some clusters of cells and many single cells

24

Lots of cells, all aggregated together.

Very difficult to see, very small, cells aggregated together with single cells which are very difficult to distinguish.