Part II: Obtaining Accurate Viscosity Measurements for Food & Beverages

Editor’s Note: Part I of this article was posted April 4 in the News section here.

Viscosity measurements were used at a brewery in Montreal to detect the specific point at which the transition from yeast to beer takes place during the purge of a fermentation tank. Accurate measurements led to significant reductions in loss of beer production time and maintenance. The case study below offers more details.

Case Study: Brewery Takes the Guesswork Out of Fermentation
Once the fermentation process is complete during beer brewing at a Montreal brewery, the yeast used in the process settles and is deposited at the bottom of the tank. The tank is then emptied by pumping the yeast out and sending it out to be reclaimed and recycled. A portion of what is left is directed to a centrifuge to separate the small amount of remaining yeast from the beer, and then the rest of the batch goes directly to filtration. The problem is that it can be difficult to determine at which specific point during this pumping process all the yeast has passed, leaving only the beer.

Since both yeast and beer are brown, it is a tricky operation to determine with certainty which is which. An operator would view the pumping process through a glass section of pipe, spot the subtle color change between yeast and beer, and stop the process at the point he guessed the separation occurred.

In addition, operators had to guess the quantity of yeast in the tank and add more or less based on temperature, yeast type, and pH. Since yeast production is never stable from one batch to another, the brewer also had to pump different quantities from each batch, depending on the type of beer, and send it to recycling, while sending a different quantity to the centrifuge. The centrifuge process also took too much time and did not filter away the proteins that regularly clog up the filters.

If operators guess incorrectly and miss transition, they can end up either sending beer to the yeast recycling operation, which means losing beer (and also getting penalties from the company buying their reclaimed yeast), or sending yeast to the filtration operation where it stresses the filters, quickly plugging them. When this happens, operators have to stop to clean the filters costing time and money. Using the centrifuge to separate yeast from beer can take as long as three hours per batch. In addition to wasting time, the manual system led to a great deal of waste of beer – they estimated about $100,000 worth of product was lost per year.

A beer brewery installed KROHNE”s Viscoline to help determine the specific point at which the transition from yeast to beer takes place during pumping process.

The brewery was looking for a way to detect the specific point at which the transition from yeast to beer takes place during the pumping process. They installed a sanitary 2-inch Viscoline made by KROHNE Inc. on the main line, just below the main transfer pump.

A solenoid valve was also installed. This is controlled using the viscosity reading in real-time. Concentrated yeast is much more viscous than beer, so it measures at very high levels, and this is directed to the recycling operation. When the measurement drops down, it is beer, which goes directly to filtration. This completely circumvents the centrifuge process, thereby saving time and beer.

The brewery saved about three hours per operation per batch. They are no longer assessed penalties from the yeast recycling company, and no longer lose more than $100,000 worth of beer each year. Because the filters no longer have to handle high yeast concentrations, there is two times less filter plugging. The brewery installed three units, and in its three-month summer season savings equaled three times its investment for a one-month payback.

The brewery was so pleased by the successful results that it decided to go for an even more precise yeast detection threshold, less than 1 percent, and they are now able to use the indicator to detect a viscosity variation of one-tenth of a CP, which represents a significant drop from 2 percent down to 0.25 percent yeast content in each batch of beer. The new process means the brewery saves $1 for every 4 barrels of beer produced.

Olivier Réglat is the VP of Technologies at Vionec Technologies. He has 12 years of field experience in process viscosity measurement with non-Newtonian fluids, and is one of the inventors of the Viscoline technology. Joe Incontri is the Director of Marketing, Americas, at KROHNE Inc. and has been with the company for 10 years.