Chemical characterization of differential sensory compounds in alcoholic and non-alcoholic lager beers: effects of dealcoholization process

Abstract

This thesis has focused on the study of the characteristic flavour compounds of commercial lager regular (alcoholic) and alcohol-free beers, with special emphasis in the differential flavour compounds between both beer types, and in those volatile compounds that are removed during the vacuum distillation process, which is the alcohol free beer production process more frequently used by Spanish breweries. In the Introduction, the state-of-the-art of the methods and systems used in alcohol-free beer production is described, the main factors affecting the organoleptic characteristics of alcohol-free beers as compared to alcoholic beers are reported in a published review by the authors, and, finally, the analytical techniques currently used in beer compound analysis are reviewed in a published paper. The experimental work of this thesis is report in three sections, each containing the corresponding papers that are either already published or submitted: Section 1: this section tackles with the methodology and results of an untargeted comparative analysis of commercial beer compounds by using UPLC-QToF-MS measurements and a metabolomics approach for differentiation between regular and alcohol-free beers. Section 2: reports the methodology used and results obtained in the analysis and profile characterization of volatile flavour compounds in diverse commercial regular and non alcohol beers by HS-SPMEGC-MS. Beers produced in Czech Republic and Spain are compared. Section 3: covers the methodology used and results obtained in a lab-scale set up of a dealcoholization process by vacuum distillation for routine sampling before, during and after the process. Volatile compound analysis of original beers, distillates and residual dealcoholized product was carried out by HS-SPME/GC-MS. Sixteen beers were used in these experiments. From these sixteen beers, two of them were chosen for sampling at different time periods during the process and analytical data were transferred to the chemical process simulation software HYSYS (Aspen Inc.). Experimental results were fit using the simulation program to a theoretical model with the aim to determine whether such model could be used in predicting the changes in the volatile profile at given pressure and temperature during the dealcoholization process.