Fining of wine with gelatine, casein and potassium caseinate

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Fining of wine with gelatine, casein and potassium caseinate
by Charl Theron
As a result of the composition of wine, the natural racking thereof due to gravitation will take too long and practices such as fining, filtration and centrifugal force are commonly used to speed up the process. Apart from the fact that different fining agents have specific reactions to certain wine components, the specifications of a specific fining agent often play an important role.
Compounds or organisms such as yeast, bacteria, grape residue, tartrates, proteins, pectins, phenols, sulphur compounds, copper and iron may cause cloudiness or sediment in wine or initiate sensorial deterioration which may cause premature spoilage of the wine. Protein turbidity in bottled wine and phenolic compounds causing bitterness or astringency in wine are the most important reason for using fining agents. A fining agent may be defined as any exogenous compound added to a wine with the objective of clarifying the wine. If proteins have to be removed from wine, mineral compounds with a large molecule surface such as bentonite, diatomaceous earth or carbon are used, while fining agents with a protein base such as gelatine, casein, isinglass or eggwhite are required to remove phenolic compounds from the wine.
Four different fining agents with a protein base, namely solid gelatine, liquid gelatine, casein and potassium caseinate were compared in a project on the removal of astringency, bitterness and colour from wine. The influence of fining agents on sensorial quality of wine was also studied. In order to understand the differences between the fining agents, their physical characteristics were evaluated. The most important difference between the fining agents is molecular weight. Casein and potassium caseinate had the smallest (30 kilodaltons), liquid gelatine in the middle (less than 43 kilodaltons) with solid gelatine (more than 43 kilodaltons) having the biggest molecular weight. Commercially available gelatine varies considerably in terms of molecular weight.
Portuguese white and red wines were used in the trial. In the case of the white wine the dosages of the solid gelatine, casein and potassium caseinate were 8, 15 and 20 grams/100 litres respectively, while 5 millilitres liquid gelatine/100 litres wine were used. For the red wine the dosages were 10 - 20 grams/100 litres wine of the solid fining agents and 6 millilitres/100 litres wine of the liquid gelatine.
The results of the trial may be summarised as follows:
White wine

Bitterness was best removed by casein and neither type of gelatine was very effective.
Liquid gelatine removes the most astringency and colour.
Both types of gelatine and casein remove most of the yellow tinge from wines.
Liquid gelatine most improved the clarity of the wine.
Sensorially, liquid gelatine produced the best colour and condition, while solid gelatine best retained the aroma intensity. There was little difference between casein and potassium caseinate, but the wines that were thus fined performed the best overall.
Red wine

Bitterness was best removed, as with the white wines, by both casein fining agents, but gelatine was not very effective in this regard.
Liquid gelatine removed the most colour and the wines were the most astringent after fining.
Both casein fining agents had the least effect on the colour and taste of the wine.
The above clearly shows the importance of knowing which gelatine to use (Guerra, 2009).
Reference
Guerra, Bibiana. 2009. Choosing a fining agent. Wine Business Monthly, 15 August 2009: 30 - 33.

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