Quantitative Detection of Free Proline as a Marker for Haze Stability in Beer

Date of Award


Degree Type


Degree Name

Master of Science (MS)



First Advisor

Benjamin J. Alper, Ph.D.


Proteins that contain high quantities of the amino acid proline are one of the most important components in the prediction and characterization of beer haze driven by protein and polyphenol interaction. Despite this fact, little thought has been given to the effect that proline in its free amino acid form may have on beer haze, and model system studies have concluded against any involvement of free proline in haze formation. In this study, free proline concentrations were determined in beer samples, and a connection to haze stability was seen through positive correlation to accelerated shelf-life data and inverse correlation to data derived from a haze stability test commonly known as the sensitive protein assay. Free proline levels were found to deviate less over the shelf-life of products from the same or similar manufacturing lots, while data from sensitive protein tests fluctuated more with time and temperature of storage. Mathematical correction for sample storage time and temperature to sensitive protein results strengthened the correlation to free proline concentration, suggesting that free proline can be used to measure shelf stability of a beer at any point in the lifetime of the product with similar results. No correlation was observed between beer haze and total free amino nitrogen levels, reinforcing the free proline-specific nature of these results. The findings in this study suggest that free proline may inhibit haze progression and should be reconsidered as part of the greater model for protein-polyphenol haze generation in beer.


Master's thesis submitted to the faculty of Sacred Heart University's Chemistry Program in partial fulfillment of the requirements for the degree of Master of Chemistry.