Volatile organic compounds investigation in Müller Thurgau wines obtained from vineyard treated with biochar

Abstract

Context and purpose of the study – Volatile Organic Compounds (VOCs) are responsible for the flavor and aroma of a wine. The sensory qualities of the wines depend not only on grape intrinsic characteristics, but also on extrinsic factors including the soil composition. Previous studies have shown that the application of pyrogenic carbon (biochar) can lead to a change in soil parameters. For that reason, one of the goals of the ERDF funded project «WoodUp» is the characterization and reutilization of the locally produced biochar for agricultural purposes. In this study wine quality is investigated to better understand how the chemical and physical modification of the soil can influence the wine VOCs profile from Müller-Thurgau, after biochar application.

Material and methods – Wines obtained from vineyard treated with different amounts of biochar were analyzed (3.9 kg/ m² dry matter compost, 2.5 kg/m² dry matter biochar, 5 kg/m² dry matter biochar, 2.5 kg/m² dry matter biochar plus 3.9 kg/ m² dry matter compost, 5 kg/m² dry matter biochar plus 3.9 kg/ m² dry matter compost and the untreated as control). Samples, 1.5 ml of each wine, were placed into 20 ml glass vial with the addition of 0.45 g of NaCl and 5 μl of 2-octanol (123 ppm) as internal standard. The volatile composition of wines was determined by using headspace solid phase microextraction (HS-SPME) coupled with gas chromatography–mass spectrometry (GC–MS) in full scan mode. The headspace was sampled using a DVB/CAR/PDMS 50/30 μm fibre; chromatography was performed on either a 30 m ×0.25 mm id×0.25 μm ZB-WAX column (Phenomenex, UK). Samples were analyzed in triplicate.

Results – Preliminary data analysis of the full scan acquisition allowed the identification of 47 volatile compounds in wine samples. Tentative compound identification was based on at least 70% quality match with NIST 17 database information for each compound. In addition, experimental Retention Indexes were calculated and compared with the theoretical ones. Among the identified compounds we find acids, esters, alcohols and some terpenes. More detailed data analysis is necessary to identify the differences on wines aroma compounds produced starting from different treated vineyard and to understand the influence of the soil composition on wine characteristics.