Olfactometry approach to assess odorant compounds of grape spirits used for Port wine production-first results

Abstract

The production of Port Wine requires the addition of grape spirit to stop the fermentation, ensuring the desired sweetness. The grape spirit, a product of wine and wine by-products distillation, must comply several legal requirements, namely the sensory evaluation before its addition to the wine. Given that previous studies1 pointed out the contribution of grape spirit to the volatile composition of Port wines, the main purpose of this study was the assessment of the odorant compounds of several grape spirits used for Port wine production. The volatiles of grape spirits samples were previously extracted by liquid-liquid extraction and after concentrated. The extracts of volatile compounds were analysed by gas chromatography–olfactometry (GCO) to evaluate the most important aroma compounds and by gas chromatography−mass spectrometry (GC-MS) for compound identification. The GCO analysis was performed using the frequency detection method2, where a group of assessors sniffed the extracts. The individual aromagrams are summed and the odour’s intensity is estimated through the number of sniffers who detect an odour.
The GCO results of the grape spirits analysed, pointed out to the presence of several odorant compounds from different chemical families, namely esters, alcohols, terpenic and acids. Some of these volatile compounds are assigned with pleasant odour notes such as fruity, caramel, honey and floral while other are assigned with unpleasant and heavy odour notes such as cheese and foot odour. The majority of the identified compounds were originated from the fermentation process and were also found in other unaged distillate beverages such as freshly Cognac and Calvados3 or Tequila4.