Investigation of beer foam with X-ray photoelectronspectroscopy: first insights

Abstract

This first investigation of beer foams using XPS enables a deeper insight than conventional analytics into the composition of beer foams as well as indications of criteria for good beer foam (NIBEM > 300 s; foam index, SKZ > 115). Due to the high sensitivity of this method, even the smallest amounts of residues can be detected in survey spectra. For an initial assessment, the total nitrogen content can be determined comparatively quick and easy, whereby a high value is obviously characteristic of good foams. The N 1s spectra can be employed to determine the quantity and size of proteins which are considered to be foam positive. A high O=C-N/C-NH₂ ratio might indicate long peptide chains and seems to be foam positive, as the results reveal. Other groups can also be identified, such as polyphenols, whose influence on the foam is also assessed. Furthermore, the results indicate that appropriate reference measurements could provide a more precise determination of the proteins and influencing factors.