Vacuum distillation of Muscaris pomace: temperature effects on aroma composition

The consumption of wine in traditional wine-producing countries like Italy, Spain, and France is decreasing. However, there is an increasing demand for non-alcoholic or low-alcohol wines, which has become a growing trend. This shift in consumption patterns has raised interest from both, companies and researchers. As the popularity of these products grows, so does the development of technologies to remove alcohol from wine. Currently, there are two main approaches for complete dealcoholization of wine for commercial use: membrane techniques, such as osmotic distillation, reverse osmosis (often coupled with another method), and dialysis, or distillation techniques, such as SCC (Spinning Cone Column) or vacuum distillation.

One of the major challenges with these technologies is the loss of aromatic compounds during processing. Several strategies have been developed to either reduce this aroma loss or to enhance aromas using other materials.

One potential solution for improving aroma compounds in dealcoholized wine is to use by-products of the winemaking process, namely pomace, which consists of grape skins, seeds, and stems. Pomace can make up 15-30% of the total weight of the processed grapes. There are three types of pomaces: non-fermented pomace, semi-fermented pomace and fermented pomace. To extract aromas from pomace, various methods can be employed, such as distillation (at atmospheric or reduced pressure), pressing, supercritical fluid extraction, or solvent/enzyme extraction. The aim of this research is to investigate the differences in aroma extraction from pomace at different temperatures under vacuum conditions. For the experiment, Muscaris’s pomace from the Rheingau (Germany) was used. The pomace was acidified and fermented (Lalvin EC1118 ), and then it was treated by vacuum distillation. A total of 2.5 kg of pomace was processed at 50 mbar, with extractions performed at four different temperatures: 25, 35, 45, and 90°C. The vacuum distillation process was stopped once 100 mL of distillate has been collected. All aroma extracts were analysed by gas chromatography (GC) to compare the differences in aroma composition across the various extraction methods. Moreover, GC analysis for methanol was also carried out to determine whether there was a possible increase in  methanol, over the legal limit, in case of addition of the aroma in a dealcholised wine. This analysis will provide understandings into the best conditions for extracting aromas from pomace.