Grapevine & Wine 03/10/2011

The use of dregs in winemaking and some possible alternatives

The employment of dregs has always been very discussed in enology, mainly for the intrinsic difficulties of the process. But today there are alternatives

Most probably some wine enthusiasts are turning their nose up at discussing about the use of dregs; but they are becoming more and more used to add some aromas and to stabilize the color.
Dregs are the deposits that form in few tens of hours after the movement of wine at the end of fermentation. Two kinds of dregs do exist:
The large particles
The small particles, normally composed by yeasts

The composition of fresh dregs is normally very variable, but the components released in the wine are always nucleotides, fat acids, amino acids, peptides, polysaccharides, glycoproteins (mannoproteins). These components have positive consequences on the sensory profile and the stability of the wine, in particular for the tartaric and proteic deposits and the color.

The quality of dregs, hence their enologic value, depends on many parameters, such as the sanitary conditions of the grapes, the extraction technique, the choice of the yeast and the optimization of the yeast population for a good management of the fermentation. It also depends on the choice of the malolactic bacteria, the movement and the temperature of the wine during the ageing. The refinement of dregs is very complex; as a matter of fact, the traditional refinement, done in barrique, is prone to the development of damaging microorganisms called Brettanomyces.

For these reasons there is now extensive research on possible alternatives for a more rational employment of dregs.
In the context of a research project on the ageing in barrique, the Institut Coopératif du Vin tested the adding of Active Dried Yeasts (LSA) and white wine dregs as an alternative to the classic refinement. The results were very encouraging, especially on the sensory profile. Five or six months after the adding of LSAs, wines show a more integrated wine, more fruity aromas, less astringency and an increased mouth volume. The adding of dregs allowed the development of the sense of smoothness, sugary and volume. All the same, the choice of the dose to be added is crucial, and it should not go over the 1-2%. Finally, the success of this technique is also determined by some important precautions, like tasting dregs in order to avoid sulfur smells, strongly acidifying and sulfitizing them, and eliminating the suspension as soon as possible.

A further possibility is the simultaneous adding of inactive yeasts and glucanase, which allowed the production of wines rich in total polysaccharides, with enhanced color and stable tone. The polymerization degree (mDP) was lower. Adding glucanase only, even if allows getting wines with a more intense color, produces less polysaccharides as compared with the previous solution. The measure of the gelatin index and the tasting demonstrate that this option leads to more astringent wines.
The adding of tannins alone is the treatment that increases the most the color, but this comes together with an increment in the gelatin index, hence of astringency.
Given these results, the optimal treatment results the contemporary adding of inactive yeasts and glucanase.

di Graziano Alderighi