II.3.4.14 Adsorbant copolymer treatment (PVI/PVP)

Classification:

• PVI/PVP copolymer: processing aid

Definition:

The addition of polyvinylimidazole – polyvinylpyrrolidone copolymers (PVI/PVP) in order to reduce copper, iron and heavy metal contents.

Objectives:

a)        To prevent defects caused by too high metal contents (for example ferric casse).

b)       To reduce undesirable, high concentration of metals due to:

• Must contaminated by metal cations
• Metal cation contamination during must or wine treatment from winemaking equipment
• Enrichment in copper following the treatment of wines by copper sulphate.

Prescriptions:

a)        The amount used should be less than 500 mg/l.

b)       When musts and wine are treated with PVI/PVP polymers, the accumulated dosage should be less than 500 mg/l.

c)        The copolymers should be eliminated after no more than 2 days after the addition taking into account the precautionary principle and separated from the wine by filtering before bottling

d)       The adsorbant copolymers used should comply with the prescriptions of the International Oenological Codex and in particular monomers limits.

e)       The  implementation of the procedure shall be placed under the responsibility of an oenologist or a specialised technician.

Recommendation of the OIV:

Admitted.