Presented at the 107th Master Brewers Association of the Americas Anniversary Convention, Cincinnati, Ohio USA

The Model KSA, shown above, does not require recalibration per beer brand.  The alcohol analyzer hardware uses the field proven fittings first introduced in 1967 and widely installed in breweries.

The brewery community has an increased interest in sanitary ethyl alcohol measurement.

There has been a history of alcohol measurement using indirect density methods, off-line, or semi-on-line laboratory techniques. This new near-infrared (MR) alcohol analyzer was specifically designed as a production floor unit, eliminating complexities resulting from the earlier NIR units that were adapted from laboratory design and thinking. This reduction in complication and complexity - as well as increased stability - gives simpler, more reliable results with repeatability. It is also less susceptible to interferences.

Data presented measures varying concentrations of:

1. color
2. solids
3. sugars
4. alcohol,

and their effect on the KSA instrument's readings.

Introduction

This poster concentrates on overcoming the pitfalls formerly associated with NIR measurement as it applies in the brewery filter room.

Several manufacturers had previously tried to develop NIR monitors. However, these instruments could not operate continuously nor compensate for interference from such items as sugar, turbidity and color without operator assistance. Interferences will cause an uncompensated instrument to provide false readings. These hidden interference sensitivities become readily apparent to the brewmaster when he sees the inconsistent readings.

Objective

The KSA Monitor, manufactured by McNab, Inc., is based on the near-infrared absorption method of alcohol measurement.

Many liquids have absorption characteristics in the near-infrared or infrared spectrum, absorbing NIR energy at certain frequencies (bands of absorption.) Certain chemical concentrations can be measured by the levels of absorption shown in the NIR spectrum.

Alcohol's unique NIR spectrum allows the choice of frequencies to isolate the alcohol from the other infrared components which might be found in beer.

Concentration of alcohol can be measured in absorption bands following the Lambert-Beer Law of optics where absorption is proportional to the loss coefficient of alcohol, the light path length, and the concentration of alcohol. However, this assumes the lack of interference.

The objective of this poster is to show how this NIR instrument's suppression of unwanted interferences leads to a high degree of success in alcohol monitoring.

Method

This work was done in a laboratory where the KSA instrument had been mounted on a pipe sealed at both ends to account for light entry and loss of alcohol.

Measurements were done at approximately 0 degrees C, except where otherwise noted.

Data

Beer color concentration may cause an uncompensated on-line instrument to provide different readings from an adjusted lab instrument (the lab technician will typically use switch selection to adjust out color effects.) An unattended on-line instrument, however, has no technician to make adjustments, and no way of knowing what brew is passing through the pipes at any one instant. Thus, what is a manual task in the lab needs to be done automatically on line, else the interference – here color – will cause false readings.

Graph 1 shows the alcohol readings provided by the McNab Model KSA when fluid color is altered.

Turbidity is another interference problem. Lab instructions often are to "filter out the offending turbidity using filter paper." While such filtering is easily accomplished in the lab, it is not so on line.

Graph 2 shows alcohol readings provided by McNab's Model KSA when turbidity is varied.

Present gravity has traditionally been measured using hydrometers, which are subject to ratio effects of alcohol, alcohol and sugar, or sugar. It is most desirable to have an alcohol meter that will measure independent to the presence of sugars, specifically sugars which would not have been converted to alcohol (non-fermentable sugars, such as dextrins.)

Graph 3 displays KSA readings when increasing amounts of sucrose are added to the solution.

Graph 4 shows the KSA's readings when alcohol is added to the solution. Correlation between volumetric lab standards and instrument readings range between .992 to .999 (depending upon the instrument's scope.)

Each of these aspects must be addressed, and sensitivity or insensitivity to these interferences needs to be appropriate to allow for accurate, unattended on-line meter readings.

Conclusions

This poster presents data that shows independence between actual alcohol readings of the KSA NIR alcohol meter with respect to changes in color, turbidity, and sugar (density-Plato.)

Summary

The laboratory findings reported here indicate that the Model KSA will provide accurate alcohol content measurement regardless of the identified interferences, and the improvements offered by the KSA instrument will allow greater latitude in the measurement of beer types without the necessity of recalibration per brand.

This on-line instrument, due to its ability to just see alcohol, can be used to identify which brands are currently in process, and identify interfaces between multiple brands.

The KSA's ability to identify brand changes in-line allows the brewmaster to more efficiently produce the multiple brands demanded by today's markets within the same brewery capacity enhancing plant efficiency and allowing for better response to consumer demand.