5 Use of Enological Additives for Colloid and Tartrate Salt Stabilization 145
susceptible individuals show lesions of the intestinal mucosa after consumption of
the gliadins of wheat. The drastic decrease in absorptive surface is the cause for
the malabsorption accompanied by weight loss and disturbance of growth (Cornell
et al. 1992; Sturgess et al. 1991). By using an ELISA immunotechnique, gluten-
antibodies were not able to recognize their antigens in the Muscat must treated with
20 g/hL gluten, these values corresponding to the detection limits of the ELISA
method used. This result clearly indicates the absence of residual gluten proteins
in the must (less than 1 mg/L, that is the limit of the kit detection). For the Codex
Alimentarius, a food is gluten-free when it contains less than 10 mg/L gluten. In this
assay, the white must clarified with wheat gluten derivatives may thus be considered
as gluten-free. These results seriously strengthen the interest one can take in the use
of gluten to clarify musts.
This study shows that gluten proteins (combined with bentonite and silica gel)
allowed very efficient clarification of the treated must whencompared with the
control must. More, the industrial scale trials showed that grape juice clarification
using the flotation technique was a little better with bentonite-gluten than with
the bentonite-fish gelatin combination which are the more commonly used fining
agents. This confirms the possibility for plant proteins to replace animal proteins, as
already observed for red and white wines (Marchal et al. 2002b,c).
5.1.5 Other Fining Agents
5.1.5.1 Polyvinyl Polypyrrolidone (PVPP)
PVPP is a high molecular weight fining agent made of crosslinked monomers of
polyvinlypyrrolidone. It complexes with phenolic and polyphenolic components
in wine by adsorption and attracts low molecular weight catechins. It removes
bitter compounds and browning precursors in both red and white wines. PVPP
is quick acting with no preparation required. Wines must be filtered to remove
the PVPP and wines may seem more astringent when the bitter compounds are
removed.
5.1.5.2 Kieselsol
Kieselsol is a generic name for aqueous suspensions of silicon dioxide. Kieselsol
is a byproduct of the glass industry. Kieselsols are produced in Germany and are
sold as 30% colloid solutions. The primary use of kieselsol is for clarification and
as a replacement for tannins during gelatinfining of white wines. Kieselsols are
negatively charged and electrostatically bind to and adsorb positively charged pro-
teins and initiate flocculation and settling. Several different kieselsol formulations
are available at a variety of pH levels. It isnecessary to use a kieselsol that is recom-
mended for wine. In general, kieselsol is used at a rate of seven times the amount of
gelatin. Gelatin should be added first, and fining trials must be done to insure proper
settling.