Aroma-Active Compounds Contributing to Aged Riesling Character

The Riesling varietal, which originates from the Rhine region of Germany, is globally one of the most popular white wine grapes. Young Riesling wines are favoured for their fruity and floral character; however, lesser-known aged Rieslings possess a more complex aroma profile with notes of sherry, maple, and a balanced petrol character. Several fruity esters and alcohols are known to contribute to the tropical fruit and floral character of young Rieslings, but the odorants that contribute to the complexity of aged Rieslings are not well characterised. Thus, the goal of this study was to employ aroma extract dilution analysis (AEDA) and stable isotope dilution assays (SIDA) to identify and quantitate the key odorants that contribute to the aroma of a ten-year-old Joh. Jos. Prüm Riesling. This study afforded 34 odorants with flavour dilution (FD) factors greater than 1, with 2-phenylethylanol (floral, rose) and ethyl butanoate (fruity) having the highest FD factor of 1024. Upon quantitation by SIDA, the odorant with the highest odour activity value (OAV) was wine lactone (coconut, OAV 460) followed by ethyl octanoate (fruity, OAV 240) and ethyl hexanoate (fruity, OAV 97). Other odorants with OAVs greater than 1, which may contribute to the complex aroma of the aged Riesling, included 5-ethyl-3-hydroxy-4-methyl-(5H)-furan-2-one (sherry, OAV 33), 1,1,6 -trimethyl-1,2-dihydronapthalene (petrol, OAV 6.4), and 3-methylbutan-1-ol (malty, OAV 3.6). This study has provided a comprehensive evaluation of key odorants contributing to the characteristic aroma of a bottle-aged Riesling and provides a foundation for future studies to probe the influence of each odorant in the overall aroma of aged Riesling.