146 R. Marchal and P. Jeandet
5.1.5.3 Isinglass
Isinglass is a positively charged fining agent derived from the air bladder of fish. It
is available as sheet or flocculated isinglass. The flocculated form is the easiest form
to work with, because it does not have to be rinsed to remove fishy odors. Isinglass
is used principally in white still and sparkling wines to clean up the aromas, improve
clarity and modify the finish without significantly modifying tannin levels. Usage
levels are typically from 1 g/hL to 3 g/hL (Marchal et al. 2003).
5.1.5.4 Casein
Casein is nearly insoluble and must be dissolved at pH 11. Potassium caseinate
is water-soluble and is preferred for this reason. Sodium caseinate is usually not
used because it increases the sodium content of wine. Casein is a positively charged
protein that flocculates in acidic mediasuch as wine. When added to wine, casein
adsorbs and mechanically removes suspended materials as it settles. In general,
casein is used to remove undesirable odors, to bleach color and to clarify white
wines. It is sometimes used as a substitute for carbon in color modification of juice
and white wine. Usage levels are typically 10–30 g/hL.
5.1.5.5 Carbon
Activated carbons are nonspecific adsorptive agents made from wood. The sponge-
like carbon binds with weakly polar molecules, especially those containing benzene
rings. Carbon effectively removes phenolic compounds, especially small phenolic
compounds. Compounds larger than dimers are too large to be adsorbed. Stripping
of wine is often a problem with carbon because of its low selectivity and great
care has to be taken with its use. Carbon also contains a large quantity of air, and
oxidation sometimes follows carbon addition if the carbon is not quickly and thor-
oughly removed. The addition of carbon to juice rather than wine helps to diminish
carbon-induced oxidation. Usage levels are typically 10–50 g/hL.
5.1.6 Equipment for the Addition of Fining Agents to Wine
The efficaciousness of fining is dependent uponthe agent, the method of preparation
and addition, the quantity employed, the pH, the metal content, the temperature, the
age of the wine, and also previous treatments undergone by the wine. Fining is a
surface action performed by the agent (adsorption); therefore, the method of hydra-
tion and addition of the agent is of extreme importance. Four common methods
of adding fining agents are: (1) through a “Y” on the suction side of a positive
displacement pump while transferringor mixing; (2) through an “in line” propor-
tioning pump; (3) through a “T” into a Guth-type tank mixer; (4) added slowly in
slurry form to a barrel using a dowel to stir in a figure-eight motion through the
bung hole (Zoecklein 1988b).