Application of In-Pipe Yeast Counting Analyzer in Medium to Small Breweries
By Curtis Holmes, Alaskan Brewing Company, Juneau, Alaska USA & H. A. Teass, Jr., McNab, Incorporated, Mount Vernon, New York USA
A presentation given by H. A. Teass at the Master Brewers' Association of the Americas District Caribbean 38th Annual Convention, May 1999
Descriptors: Yeast Pitching, Particle Counting, Yeast Pitching Uniformity, Diacetyl.
With regard to accurate pitching levels, the following requirements apply, which typically have not been met. This automatic pitching increases the performance of the brewery, simplifies the laboratory's requirements and increases the efficiency of the pitch. The new pitching system at Alaskan Brewing Company meets these requirements. Through careful design, the variability and the concentration of pitched yeast was improved by a factor of better than 10:1. This results in improved diacetyl concentration levels.
The Alaskan Brewing Company in Juneau, Alaska, had a requirement to improve the yeast pitching. In order to meet its needs the pitching accuracy had to be improved by a factor of approximately 500%.
The brewery's goal was to improve the pitching so as to meet a new standard of ±500,000 cells/ml for 95% of the time in its pitching system. This is done for the following reasons:
Requirements and Preconditions
Alaskan Brewing Company had several concerns. The pitching SKID must be, of course, completely sanitary, and introduction of contaminants must be avoided (open handling of yeast slurry). The floor space required by the SKID must be minimal. In no way must this SKID introduce an additional burden into the brewery by requiring extra operational personnel's attention or by an increase in time delay in the fermentation process. No production interruption by the SKID installation into the brewery could be allowed.
In order to meet these requirements, the conventional method of pitching was deemed not adequate to meet new requirements. With the conventional volumetric flow or by the yeast concentration level change in the tank, pitching adjustment was made by the laboratory dilution factor (in measurement of cell concentration and calculations). This subsequent adjustment by laboratory measurements was inexact and too costly.
It was noted that the yeast measurement by particle counter will give lower instantaneous cell values. The brewery had in place a yeast slurry delivery pump and it was run based on the time required to deliver a certain amount of gallons carrying a certain amount of cells/ml. In practice the laboratory would go measure the cells/ml in the slurry, calculations were made of how many gallons it would take to meet target, that was converted to in-pump operating time and the pump was started, yeast was delivered into the wort stream, and then into the fermenter.
In place of the laboratory yeast slurry (hand counting with a hemocytometer), a HSA4 was installed in the yeast pipe that would read 0 - 2 billion cells/ml total cell (or alternatively, live cell summary, Figure 1 - HSA4 v Hemocytometer). Likewise, in order to improve the pitching, a flowmeter was installed. On command, the pump would be turned on, the total number of cells being delivered to the wort stream would be counted "on the fly" and tallied (See Figure 2) and, when the predetermined delivery had been accomplished, the pump would automatically be turned off (slurry delivery can be independently adjusted to match wort flow). You can see by the illustration how this is accomplished (see attached Fig. 3-Yeast Process Skid). Yeast comes in the left hand side and passes through a hose into the SKID, its volume is measured, its concentration is measured and, with a computer, totalized. Then, using the yeast slurry pump, it is moved forward into the wort line and then into the fermenter.
For those yeast systems incorporating load cells on slurry tanks, the SKID could have the same effect. With additional processing, weight information could be used from the load cells' signal (in lieu of flow) in order to determine the volume delivered. Thus cell concentration can be determined. Either method (tank or flow meter) would arrive at the same improved result.
The unit was first installed in January 1999 (see photograph of the SKID in operation) and, as of the end of April, the new system has met its requirements for the new demands for yeast target accuracy (See Figure 4). In other discussions it is suggested that the laboratory practice of measuring the cells and dilution is a more difficult one than first imagined. This difficult laboratory task occurs in a production environment, where there is more work than time available.
Immediately upon hook-up, the brewery fully met its objectives. The variability of the pitch was immediately reduced (see Figure 4-Yeast Pitching Rates). Laboratory analysis was continued in parallel with the automatic analysis for verification only. We have now come to believe that the cell counter provides a more accurate count than the hemocytometer method. The results are as follows:
This project demonstrates that a small to large size brewery can more accurately pitch its yeast to very high standard. It is a cost effective method in accomplishing pitching and that it, in effect, eliminated the uncertain and time-consuming laboratory analysis of manually counting yeast cells . This resulted in high quality beer.
Broderick, Harold M., THE PRACTICAL BREWER, Master Brewers Association of the Americas, 1977
Teass, H.A., Byrnes, J., Valentine, A., "Correlation of Yeast Measurements Between Hemocytometer, Spin-Down and Coulter Counter Laboratory Analysis And In-Line Measurements With The McNab Cell Counter," McNab, Incorporated, Mount Vernon, New York, 1998
Kunze, Wolfgang, TECHNOLOGY BREWING AND MALTING, VLB Berlin, Germany, 1996
Pollock, J. R. A., BREWING SCIENCE (Volume 3), Food Science and Technology, Academic Press Inc. (London) Ltd., 1987
Following are questions posed to Mr. Teass after his presentation:
1) Q: What about the cleaning? Is it included?
2) Q: Micro control to avoid contamination?
3) Q: Viscosity vs. Cells counts (cells/ml)?
4) Q: Please give a name or reference of breweries that are using the system?
5) Q: What is a small brewery? The maximum output is?
6) Q: Comment on live and dead cells.
7) Q: Measuring particle size (count) on dark product.