Dr. Serena Belfante – Laboratory Manager
Wine clarity is a fundamental condition for the consumer, so intervening with the collage process allows us to achieve four essential objectives:
- Clarify the wine;
- Improve filterability;
- Improve taste characteristics, such as astringency and bitterness;
- Stabilize the wine to avoid precipitation after bottling.
The process of removing unstable molecules is crucial in this process. In a wine, we can find negative and positive charges, and it is on these that the action of clarifiers is based. In our test, we compared our Kompact 120 bentonite with another commercial bentonite. This clarifier has a negative charge, which enables it to remove positively charged proteins, which are responsible for protein casse.
The process goes like this: the addition of the adjuvant creates aggregation, followed by neutralization of the charge and an increase in the hydrophobicity of the molecule, which results in its precipitation.
Fig 1. Molecular structure of bentonites
In Image 1, you can see the structure of bentonites, mineral colloids consisting of aluminum silicates. When placed in an aqueous medium, the bentonite swells and takes on a negative charge.
There are three types of bentonites commercially available:
- sodic, with high adsorption capacity and little compact deposition at the bottom of the reservoir due to the presence of numerous sodium ions;
- calcic, with lower adsorption capacity but more compact deposition than sodium bentonites, due to the presence of bivalent calcium ions (Ca++), which tend to compact;
- activated, that is, calcium bentonites subjected to sodium treatment. These are the most common because they are effective even at lower doses and require shorter rehydration times.
In our study we considered two types of sodium-activated bentonites: our Kompact 120 and another commercial bentonite, which we will refer to as “Bento 2” for illustrative purposes. We tested these two clarifiers on a heat-stressed control wine (80°C for 12-20 minutes), with an NTU value of about 90. The parameters we analyzed were deposit volume, deproteinizing action and clarifying efficacy.
For all parameters, Kompact 120 proved to be the most effective in removing the proteins responsible for wine opacity. In addition, it is important to mention that essedielle® bentonite takes only 2 hours to disperse and swell, unlike the classic 12-24 hours. The images below show an interesting fact: at the end of the treatment, the deposit is more compact, which results in significantly lower losses and higher effectiveness for Kompact 120. This also results in a lower upstream dosage, by about half.
Fig 2. Initial clarification stage after the addition of the two different additives
Fig 3. Evolution of clarification after 24 hours
Also crucial is the deproteinizing action. Clarification operations can take up to a week to complete, but we have noticed how Kompact 120 is able to remove more than 80% of protein in a single day. This once again confirms its effectiveness and speed in performing its function as a mineral colloid.
Finally, to confirm the data collected earlier, we checked the NTU value (see image 4). Starting from a wine with a turbidity of 90, we were able to achieve values of 20 NTU, resulting in a clean and clear wine and minimizing waste deposit.
Fig 4. Value of NTU after Kompact 120 vs. Bento 2