Comparative Study of Dark Beer Before and After Freeze Drying Rehydration Cycle

The aim of the study was to compare dark beer before and after a freeze drying rehydration cycle. The pH, colour, and concentrations of extract, organic acids, and phenolic compounds were determined. Dark beer before and after freeze drying was analysed using standard brewing analysis methods of the Mitteleuropäische Brautechnische Analysenkommision (MEBAK) and two types of chromatography: high-performance liquid chromatography (HPLC) and gas chromatography mass spectrometry (GC/MS). Increase of pH was not observed in dark beer after freeze drying. Dissolved powdered beer in deionised water was clear, dark brown, without sediments, and reproduced the original commercially available dark beer, with original extract substance content 8.88%. Concentrations of the following organic acids were determined: oxalic, tartaric, quinic, malic, ascorbic, lactic, acetic, citric, fumaric, and succinic. Volatile compounds by GC/MS analysis were isolated from dark beer before and after freeze drying.