Partial dealcoholisation of red wine by reverse osmosis-evaporative perstraction: impact on wine composition

Abstract

Around the world, the alcohol content of wine has been steadily increasing; partly as a consequence of climate change, but also due to improvements in viticultural management practices and winemaking techniques [1,2]. Concurrently, market demand for wines with lower alcohol levels has increased as consumers seek to reduce alcohol intake for social and/or health reasons [3]. As such, there is increasing demand for both innovative methods that allow winemakers to produce ‘reduced alcohol wines’ (RAW) and a better understanding of the impact of such methods on the composition of RAW. This study therefore aimed to investigate compositional changes in two red wines resulting from partial alcohol removal following treatment by one such method, involving a combination of reverse osmosis and evaporative perstraction (RO-EP). An RO-EP technique (and apparatus) was proposed in the 2008 US Patent application by Wollan [4]. In this system, wine is fractionated by reverse osmosis (RO) to generate ‘retentate’ (i.e. concentrated wine) and ‘permeate’ streams. Retentate is circulated back to the feed tank, while permeate is degassed, moderately heated (to 45–55°C), and passed through a hydrophobic hollow fibre membrane; with water flowing across the downstream face of the membrane, as a ‘stripping’ liquid. During RO, ethanol vapour diffuses through membrane pores and is subsequently condensed in the ‘strip’ water, such that the ethanol content of the permeate decreases. Treated permeate is then returned to the feed tank, ultimately giving RAW. Depending on the processing parameters of RO-EP treatment, the alcohol level of RAW can be as much as 1 to 2% (v/v) lower than untreated wine. To date, few studies have considered the impact of RO-EP on wine composition. In this study, two red wines were partially dealcoholised by RO-EP and wine (before and after treatment), retentate, permeate (before and after EP) and strip water samples collected for compositional analysis. Wine colour was measured using spectrophotometric methods; with other compositional changes determined by WineScan, high performance liquid chromatography and gas chromatography-mass spectrometry analyses. Compositional data will be presented, to provide insight into the chemical changes that occur during dealcoholisation of red wine by RO-EP.

References: 1. Pickering, G.J. (2000) Low- and reduced-alcohol wine: A review. Journal of Wine Research, 2000. 11(2): p. 129-144. 2. Godden, P. and Muhlack, R. (2010) Trends in the composition of Australian wine, 1984–2008. Australian and New Zealand Grapegrower and Winemaker, 558, 47–61. 3. Rowley M. (2013) Market analysis for lower alcohol Australian wine. Wine and Viticulture Journal, 28, 63–64. 4. Wollan, D. Alcohol reduction in beverages. Patent Number: US 2008/0272041 A1, 2008.