How to increase pyrazines in Shiraz (or not)

by | Apr 17, 2021 | Winetech Scan

The aim of the study was to establish the influence of MOG (matter other than grapes) included in fermentation on the chemical and sensory profiles of Shiraz wines.

PROJECT LAYOUT:

Five different treatments:

  • Control – berries only
  • Berries and leaves (1% w/v)
  • Berries and rachis (2.6% w/v)
  • Berries and peduncles (1.5% w/v)
  • No fermentation on the skins (rosé)

Shiraz grapes from Adelaide Hills were harvested at 23.1°Brix and divided in 13 batches of 50 kg each. Two batches were used for controls and two for rosé fermentations. Remaining nine batches were used for triplicate MOG treatments. Wines were fermented with EC1118 and after completion sulphured, filtered, bottled under screwcap closures, and stored at 15°C. Chemical and sensory analyses were performed 14 months after completion of fermentation.

MAIN RESULTS:

  • The addition of leaves increased red fruit and confectionary aromas in the wines compared to the control.
  • The addition of peduncles enhanced green, overall fruit and floral aromas and flavours in the wines compared to the control.
  • The rachis treatment Shiraz wines were higher in astringency with capsicum / green stalks attributes.
  • The rachis treated wines had 9.7 and 5 ng/L IBMP and IPMP on average, respectively.

SIGNIFICANCE OF THE STUDY:

The study demonstrated for the first time the influence of winemaking practices on pyrazine levels in Shiraz, a cultivar not commonly associated with pyrazines and their sensory contribution. The researchers suggest that the extraction of methoxypyrazines from lignified or non-lignified rachis material should be investigated.

This line of research could be interesting for Sauvignon blanc, where capsicum aroma is considered a positive attribute.

REFERENCE:

Capone, D.L., Barker, A., Pearson, W., and Francis, I.L. (2021). Influence of inclusion of grapevine leaves, rachis and peduncles during fermentation on the flavour and volatile composition on Vitis vinifera cv. Shiraz wine. Australian Journal of Grape and Wine Research, published online: https://doi.org/10.1111/ajgw.12489

Image: Pixabay

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