Treatment with different fining agents of white musts from spoiled wine grapes

Abstract

Fining agents have evolved significantly over the last twenty years. The need for winemakers to have objective references about the new products has prompted this study. The experiment consists in comparing the new fining products (charcoal, pea proteins, derivatives of chitin and composite products generally mixing PVPP + various proteins + bentonite) with reference products such as casein and PVPP and with non-treated controls. Fining agents were applied during clarification of 15 different musts obtained from wine grapes affected by different degrees and types of rot: fresh and dry Botrytis cinerea rot, powdery mildew and Botrytis contaminated with other fungi (Aspergillus, Penicillium, Basidiomycetes), giving the bunches offflavours that were earthy and resembled fresh mushrooms. This study highlights the importance of good clarification of musts. The quality of control wines, without any treatment, increases with the clarity of the must. In most experiments, clarification of the must around 50 Nephelometric Turbidity Units (NTU) can eliminate or reduce any organoleptic defects in wine without fining. Use of pectolytic enzymes may be necessary in order to reach this level of clarity. The new allergen-free fining agents have the same effectiveness as reference products such as casein and polyvinylpolypyrolidone (PVPP). Composite products are more efficient than pea protein alone and less than products including charcoal. However, the improvement of aromatic quality goes hand in hand with loss of body and persistence.