Influence of processing parameters on aroma profile of conventional and ecological Cabernet-Sauvignon red wine during concentration by reverse osmosis

Abstract

AIM: Wine aroma represents one of the most important quality parameter and it is influenced by various factors (viticulture and vinification techniques, climate or storage conditions etc.). Wines produced from conventionally and ecologically grown grapes of same variety have different chemical composition and aroma profile [1]. Aroma profile of wine can be also influenced by additional treatment of wine, such as concentration of wine by reverse osmosis (RO). Reverse osmosis represents a pressure-driven membrane separation technique that separates the initial wine on the retentate or concentrate that is retained on the membrane, and permeate that passes through it [2]. Wine permeate usually containes water, ethanol, acetic acid and several low molecular weight compounds that can pass through the membrane. This property enables the use of reverse osmosis membranes for wine concentration, partial dealcoholization, acetic acid or aroma correction [3,4].

METHODS: The aim of this study was to investigate the influence of four different pressures (2.5, 3.5, 4.5 and 5.5 MPa) and two temperature regimes (with and without cooling) on aroma profile of conventional and ecological Cabernet Sauvignon red wine during concentration by reverse osmosis. The reverse osmosis process was conducted on a plate-and-frame membrane filter Alfa Laval LabUnit M20, equipped with 6 composite RO98pHt membranes. The aroma compounds in initial wines and obtained retentates were analyzed on gas chromatograph with mass spectrometer. The solid-phase microextraction (SPME) method was used for sampling.

RESULTS: In the initial wines and their RO retentates, 45 aroma compounds were identified and divided into six groups: acids, alcohols, terpenes, carbonyl compounds, esters and volatile phenols. A certain loss of total aroma compounds was observed in conventional and ecological wine retentates, comparing to the corresponding initial wine. Higher working pressures (4.5 and 5.5 MPa) and the regime with cooling resulted in higher retention of total aroma compounds than the opposite processing parameters. Individual compounds retention depended also on their chemical properties and their interactions with the membrane surface. Reverse osmosis membranes proved to be highly permeable for acetic acid or undesirable 4-ethylphenol and 4-ethylguaiacol that made them applicable for their correction or removal. Initial wine composition influenced the retention of aroma compounds during reverse osmosis of red wines. Slightly higher retention of total acids, alcohols and terpenes was observed in conventional wine retentates than in the ecological one. The retention of carbonyl compounds, esters and volatile phenols was slightly higher during concentration of ecological wine than the conventional wine.

CONCLUSIONS:

The aroma profile of the wine retentate depends on initial wine aroma profile and applied processing parameters during reverse osmosis process (pressure, temperature, membrane type).