Foamability of bentonite treated wines: impact of new acacia gum fractions obtained by ionic exchange chromatography (IEC)

Abstract

Foam is a key aspect of quality of sparkling wines. Bentonite is usually added to the wine to prevent protein haze, but reducing its foamability [1]. New skills are searching to avoid this undesirable event [2]. Acacia senegal gum (Asen) is an exudate from Acacia trees, which can be used to stabilize red wine color. Asen can be fractionated, and the most widely used method is Hydrophobic Interaction Chromatography (HIC) to obtain low (HIC-F1), medium (HIC-F2) and high (HIC-F3) molar mass fractions. The effect of these fractions on the foamability of bentonite-treated wines was studied, showing positive or negative effects depending on the fraction and the wine [3].

Asen can also be fractionated by Ion Exchange Chromatography (IEC) giving a high (IEC-F1) and low (IEC-F2) molar mass fractions [4]. A synthetic wine (SYWI) was prepared (12 % v/v ethanol, 3 g·L-1 of tartaric acid). 8 base wines from Spain (3) and France (5) were made by the traditional white winemaking method. They were treated with bentonite (20 g·hL-1), stirred gently for a few hours, kept in cold storage (10 days, 4 °C), racked and filtered (1 μm). IEC-fractions were added to SYWI (60 g·hL-1) and to wines (30 and 10 g·hL-1). The foaming parameters were compared by shake test and by a classical gas-sparging method (Mosalux), being the qualitative aspect of foam also observed.

In SYWI, IEC-F1 improves the foamability during the total shake test. Both fractions enhance its Maximum Foam Height (HM) and the Foam Stability Height at 5 minutes (HS) measured by Mosalux. IEC-F1 provides less compact foam with larger bubble. In Spanish wines, IEC-F1 increases the foamability during the total shake test. IEC-F1 also improves it in French wines, but weaker and differently depending on the wine. The foamability is punctually enhanced by IEC-F2 in some wines, but it is greatly decreased in 1 French wine. The dose reduction decreases the improving impact of IEC-F1 on the foamability of the French selected wine but not in the Spanish selected wine. IEC-F1 increases HM and HS in both selected wines, whereas IEC-F2 improves HS only in the Spanish selected wine.

Concluding, the addition of IEC-F1 increases foamability for all the studied wines, but very differently depending on the wine. IEC-F2 addition shows positive, neutral or even negative effects depending on the wine. Dose of IEC-F1 may also play a key role depending on the wine.

References:

[1] Marchal et al. J. Agric. Food Chem., 2002, 50, 1420
[2] Martí-Raga et al. J. Agric. Food Chem., 2016, 96, 4962
[3] Apolinar-Valiente et al. J. Agric. Food Chem., Under Review
[4] Apolinar-Valiente et al. Food Hydrocoll., 2019, 89, 864