Quantification Of α- And β- Hop Acids Utilizing Electrospray Ionization Mass Spectrometry
Hops acids are important ingredients in the beer brewing process due to their addition of sensory attributes such as bitterness and aroma. Industry standard methods, set forth by the American Society of Brewing Chemists (ASBC), utilizes both High Performance Liquid Chromatography with Ultraviolet detection (HPLC-UV) and Ultraviolet/Visible Spectroscopy (UV/Vis) to successful describe the hop acid concentration and Hop Storage Index (HSI). However, these methods either employ large amounts of toxic solvents, lack the level of sensitivity for quantification of the acids, and include length separation-to-detection times. Research conducted used electrospray ionization and mass spectrometry (ESI-MS) to improve the speed, efficiency, and selectivity of hop acid analysis. ESI-MS is limited to concentration dependent ion suppression effects. Through a standard addition of α and β calibration standards, using the analysis technique, a maximum concentration of 5 μM per acid was found to be the limit at which suppression effects would not affect the detection. Furthermore, Check samples provided by the ASBC were then analyzed resulting in a performance statistically within one standard deviation to the national averages of the standard HPLC-UV method. ESI-MS analyses were completed in 3 minutes as compared to the 30 minutes of separation-to-detection time of HPLC-UV and required 400 μL per run as compared to the 10 mL a typical HPLC-UV consumes or the 9 mL needed per UV/VIS test.