In white wine grape processing the quality of the pressed juice can impact the fermentation performance as well as the quality of the wine produced. Solids management is a common practice and targeted solids as percent solids or NTU are frequent measurables. Excessive lees volume post-settling can be a source of loss of yield or increased burden on lees processing in juice recovery operations.
An important but often unmeasured component of white juice is phenolics. Excess phenolics can cause immediate and subsequent issues. Compromised fruit or later harvesting decisions can lead to over extraction of phenolics from winegrapes in processing. In addition, with economic concerns about yield, aggressive pressing regimens can lead to an increased phenolic load in the juice and wine. Phenolics can negatively impact yeast fermentation performance, physical properties of white wine color and sensory impacts including bitterness and aggressive mouthfeel.
An early and effective fining of white juice can reduce undesirable phenolics, alleviate color and pinking concerns as well as preserve delicate aromatics which can be stripped by a later more aggressive fining in the wine finishing process. In this trial the use of several fining agents will be investigated with quantitative measurables including lees compaction and time, A280, A420-A520, catechin level and aromatic volatile preservation.
The experimental control will be unfined juice processed by standard winery practices while the treatment will involve the use of a fining agent post-press but prior to fermentation initiation.