More than leaving stems in
Whole-cluster fermentation means fermenting intact grape bunches to some degree rather than removing every berry from its stem. Producers may use all, some or none of the clusters, and that decision can change from parcel to parcel and vintage to vintage.
Stems can influence aroma, tannin and the physical environment of fermentation. Their ripeness and condition matter as much as the percentage used.
How it may show in the wine
Some wines gain lift, spice or a different architecture of tannin; others may show herbal or stemmy notes. No single flavor proves that whole clusters were used, and the technique is not automatically a marker of quality.
The better tasting question
Instead of asking whether whole cluster is good, ask what it contributes here. Does it bring perfume, energy and shape into balance with the fruit—or does the method call attention to itself?
Sources & further reading
Australian Wine Research Institute · Whole bunch fermentation ↗
