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A new process developed by German chemistry teacher Jürgen Neisius to recover aromas from fermentation gases has now been patented. His method is said to surpass previous techniques: Many of the volatile aromas are lost in the carbon dioxide produced during alcoholic fermentation, especially at higher fermentation temperatures. Since most of the fermentation gas consists of non-condensable carbon dioxide, coolers used in distillation technology, for example, can only recover a few aromas. In Neisius' invention, the fermentation gas is brought directly into material contact with a cryogenic "washing liquid" rich in alcohol. This cryconcentrate is obtained by freezing a wine of the same grape variety at -30°C, the ice is separated.
In this process, known as "gas washing", condensation and absorption complement each other and yield a significantly higher aroma yield. At the beginning of fermentation, the fermentation gas condensate contains mainly primary aromas (terpenoids), later more secondary aromas (esters). These can be collected separately and then selectively recirculated. Afterwards, the ice or its meltwater must be added back to the wine to avoid unauthorised alcohol enrichment. The flavours obtained in this way can also be used to flavour other products, such as dealcoholised wines or wine-based beverages.
The process can also be applied to the production of fortified wines, where the washing liquid consists of the spirit of the wine, which is then used to stop the fermentation. For distillates, the aromas can be enhanced if the washing liquid is a distillate of the same type.
(al / Source: The Winemaker; Photo: 123rf)