Sorption equilibria of ethanol on cork

Area of Science:

• Materials Science
• Chemical Thermodynamics
• Food Science

Background:

• Cork is a natural material used as stoppers in winemaking.
• Understanding cork's interaction with wine components is vital for its performance.
• Ethanol and sulfur dioxide (SO₂) are key components in wine affecting stopper integrity.

Purpose of the Study:

• To investigate the thermodynamic properties of gaseous ethanol sorption on raw cork.
• To understand the impact of ethanol sorption on cork's reactivity under enological conditions.
• To evaluate the effect of pre-sorbed ethanol on sulfur dioxide sorption by cork.

Main Methods:

• Sorption-desorption isotherms were measured using thermogravimetry at 298 K.
• Sorption enthalpies were determined as a function of loading using calorimetry.
• Sulfur dioxide sorption was studied on cork pre-loaded with ethanol.

Main Results:

• Sorption-desorption isotherms showed a hysteresis loop, suggesting material swelling and ethanol absorption.
• Ethanol sorption enthalpy decreased with increasing loading, potentially due to endothermic swelling effects.
• Pre-sorbed ethanol (2 wt%) halved the amount of SO₂ sorbed, indicating competitive sorption mechanisms.

Conclusions:

• Cork's interaction with ethanol is complex, involving swelling that influences sorption thermodynamics.
• Ethanol presence in cork acts as a barrier to SO₂ sorption, not an enhancer.
• These findings provide insights into cork's suitability as a wine stopper material.