Membrane contactor: a sustainable technology to remove dissolved oxygen from wine and preserve wine aroma

Abstract

Oxygen management in wine is one of the most significant challenging issues for winemakers. Excessive dissolved oxygen can prematurely age wine, leading to the development of organoleptic defects. Membrane contactors (MC) composed of hydrophobic hollow microporous fibers are emerging as a promising technology for managing dissolved gases during winemaking. Operating at ambient temperature and atmospheric pressure, this technology offers a sustainable approach to controlling dissolved oxygen in wine, particularly in pre-bottling. However, concerns often arise regarding the potential impact of membrane technologies on the wine aroma Volatile Organic Compounds (VOCs). Currently, limited data exist on the effects of deoxygenating white and red wine using MC technology on their aromatic profiles. In this study, deoxygenation experiments were conducted on a white wine (cv. Greco) and a red wine (cv. Aglianico), both initially oxygenated to approximately 6 mg/L of dissolved oxygen. Deoxygenation was performed using two methods: polypropylene hollow fiber MC and the conventional technique of nitrogen sparging. In both treatments, the target dissolved oxygen level was set at 0.7 mg/L. Analyses of free and bound SO₂, acetaldehyde, and VOCs were conducted shortly after the treatments. After six months of bottle ageing, free and total SO₂ and total acetaldehyde were measured, and sensory analyses were performed. The odor profiles of the wines were assessed using the Rate All That Apply (RATA) method. Both Aglianico and Greco wines treated with deoxygenation exhibited lower acetaldehyde content and higher levels of free and total SO₂ compared to the control wines. This demonstrates the effectiveness of the deoxygenation treatment in preventing chemical oxidation and extending the protective action of SO₂. Among the VOCs analyzed – 43 in the white wine and 48 in the red one – none showed significant changes in concentration following the MC treatment. However, after six months of bottle ageing, differences in the odor profiles of treated and untreated wines became apparent. In the white wine, pre-bottling deoxygenated resulted in higher intensity scores for descriptors such as “exotic fruits” and “thiolic”, particularly when MC was used. Conversely, the control wine exhibited stronger intensities for “sweet odors” (e.g. honey, vanilla) and “dried fruits”. For the red wine, deoxygenation enhanced “red fruits” odors, compared to untreated wine. With its advantages in automation, precision, in-line integration, and gas efficiency, MC technology proves to be a viable alternative to sparging for oxygen management in winemaking, effectively preserving wine aroma compounds.