Identification and differentiation of haze substances using Raman microspectroscopy

The identification of turbidity or haze is an important part of brewery analytics. Haze can be caused by various issues throughout the brewing process and identifying the composition can pinpoint the origin. Haze analytics are commonly based on enzymatic or microscopic methods, which can be inaccurate or laborious. Raman microspectroscopy (RMS) presents a promising alternative for detecting haze particles. It is fast, easy to use and requires little sample preparation. Here, the applicability of RMS at 532 nm and 785 nm to identify potentially haze‐forming particles has been evaluated. At 532 nm, measurements were taken with standard microscope slides. Due to the high fluorescent background of normal glass at an excitation wavelength of 785 nm, fused quartz microscope slides were used at this wavelength. Starch, arabinoxylan, cellulose, yeast β‐glucan, barley β‐glucan, gliadin, ferulic acid, proline, glutamine, calcium oxalate and PVPP were identified at 532 nm. The same substances when analysed at 785 nm resulted in problems with weak carbohydrate spectra of the β‐glucans and arabinoxylan. All the other substances could be analysed at 785 nm. Catechin, which produced fluorescence noise at 532 nm could be identified at 785 nm. Although there is an issue with the intense fluorescence noise of some beer components, Raman microspectroscopy has great potential in haze analysis and potentially in wider brewery analyses. © 2020 The Authors. Journal of the Institute of Brewing published by John Wiley & Sons Ltd on behalf of The Institute of Brewing & Distilling