Fining is often considered an obsolete practice that can be replaced by sophisticated wine technologies that are respectful of wine quality. Even though this is partially true, fining remains the only and the most effective solution to reach wine stability and sensory balance in the most difficult circumstances. Choosing the right fining agent and using the correct dosage so as not to lose quality is crucial.
Fining can have different purposes.
Haziness is produced by solids in suspension. Solids can have different origins, they can be:
Filtration and centrifugation can be very good alternatives to fining for improving wine clarity. Fining agents that are the most effective for this application are gelatine, especially high molecular weight gelatine, isinglass, and egg albumin.
Gelatine is not just one product but a big family of products that differ in molecular weight, charge density, isoelectric point. High molecular weight gelatines are the most effective in improving wine clarity.
Isinglass does not require the use of co-fining agents like bentonite and silica sol unless it is necessary to accelerate the sedimentation. It is not sensitive to colloids and for this reason it is recommended for the clarification of wines containing glucans or neutral pectins.
Egg albumin is mainly used for red wine clarification because it respects wine structure. At pH above 3.6, its charge is significantly reduced and consequently its effectiveness.
Plant proteins are a good choice when producing vegetarian and vegan friendly wines.
Wine filtration can be made difficult by the presence of visible and invisible particles. Visible particles, solids or compounds out of solution, affect wine filterability but their removal is not a big issue. They can be eliminated with a good clarification that improves wine clarity, as mentioned above, or directly by filtration choosing the filtration material with the appropriate porosity and surface. Invisible particles are the real enemy of filtration. Low turbidity is naively considered synonymous with filterability, but often it is not like that. Wine is rich in colloids, particles that are small enough (size between 1 nm and 1 μm) to be invisible but that are able to interact with filtration membrane throughout various mechanisms and clog the filter. When dealing with a low turbidity wine with a high colmatation index, the problem arises from polysaccharides, proteins and color compounds in colloidal form. The correct preparation of the wine for filtration, especially in the case of cross flow filtration and microfiltration, requires a clarification to reduce colloid content and prevent membrane fouling.
Fining agent can be used to remove elements that can cause haziness and sediment formation or the appearance of sensory defects after bottling thus causing loss of wine value and disputes from customers. Choice of the fining agent used depends on the nature of the instability factor. Choice of the correct dosage requires running laboratory bench trials and the application of specific tests for evaluating the outcome of the treatment.
To safeguard the health of consumers, as knowledge advances, regulation imposes limits on the composition of wine. Nowadays it is well known that ochratoxin A (OTA) and biogenic amines can be present in wine in quantities that can have negative effects on human health. In the coming future, new substances may be added to the list of the unwanted compounds. Fining agents can help in reducing the content of these dangerous substances, thereby complying to legal limit.
Nowadays, correcting wine sensory imperfection can be done in a less invasive method with the help of yeast polysaccharides and tannins. Nevertheless, in the most severe situations, fining agents are still the best solution.