M-76: Aspects of in-line instrument measuring principles for alcohol determination, with introduction of a new low-cost method

J. NORTHROP (1), J. Bloder (2); (1) Anton Paar USA, Ashland, VA, U.S.A.; (2) Anton Paar GmbH, Graz, Austria


In most countries, alcohol is one of the most important beer components to measure for regulatory and taxation purposes. The history and further development of the methods and most important theoretical and practical aspects of in-line alcohol measurement are described in this paper. Historically in the laboratory, distillation and density/refractive index methods were used. In the late 1980s, sound velocity and the alcohol combustion cell started replacing the refractive index. By the end of the 1990s NIR started replacing them and is now the most commonly used method in the laboratory. In-line instruments using NIR or density/sound velocity were introduced in the late 1980s. New NIR methods using ATR are now also popular. The most important theoretical and practical aspects of NIR, density, sound velocity, and refractive index measuring principles and how these are used for measuring in-line alcohol content will be discussed in detail. Additionally, how other beer components influence measurement accuracy, how process conditions like flow and temperature influence performance, and what additional parameters can be measured or calculated from the measured values are addressed. As total cost of ownership gains importance, a low-cost method based on sound velocity is introduced. The accuracy, practical experience, and results of this measurement in a craft brewery are discussed. This presentation is a review. Work was completed at Anton Paar GmbH, Graz, Austria, from data collected from craft and larger breweries in the United States and Austria.

J. P. Northrop has been the senior technical sales representative for Anton Paar USA for more than seven years and is responsible for all U.S. brewery operations sales through the Anton Paar Process Instrumentation Solutions Group. He has an ACS certified bachelor’s degree in polymer chemistry from The College of William and Mary in Virginia (1996), as well as a master’s degree in organic chemistry from the University of Delaware (1999) and an MBA in finance from the Fox School of Business, Temple University, Pennsylvania (2004).

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