Chemometric analysis of the volatile fraction evolution of Portuguese beer under shelf storage conditions

• A methodology for monitoring and detecting the onset of meaningful changes on beer volatile profile is proposed.
• No significant variations are detected in beer during the first 6 months in bottle.
• A discussion is presented on the limitations of current variable contribution methods.

In this work we present a multivariate statistical analysis of the evolution of the volatile fraction of Portuguese beer over an extended period of 1 year under standard shelf storage conditions, using gas chromatography coupled with mass spectrometry (GC–MS). A systematic methodology is proposed for detecting the onset of meaningful changes in chemical composition during shelf storage and to monitor its evolution along time. We also put forward and discuss chemometric procedures for analyzing the contributions of different chemical components in the definition of dynamic ageing trends. In summary, the chemometric analysis reveals that the chemical composition of beer presents a statistically meaningful deviation from the reference scenario after a period of 7 months, although the deviation trend has its onset during the 6th month. The analysis performed also underlines the limitations of current variable contribution methods, and an alternative procedure was proposed based on the analysis in the original domain which finally led to a consistent and interpretable clustering structure of the volatile fraction compounds. Esters and higher alcohol compounds stand up on a cluster arrangement suggesting that their strict control can effectively point out meaningful changes on beer aroma. Organic acids, namely caprylic, capric and acetic acids can also be very helpful in that sense.