Decanter technology can have a huge impact on juice recovery in future, according to results of commercial-scale tests.

Standard practices for the processing of grapes to juice include destemming, crushing, draining, pressing and settling or flotation. The result is always two fractions of juice: higher-quality free-run juice and lesser-quality press juice. New developments in decanter technology allow separation of juice, either directly after removal of the stems, or after some contact time. The juice is recovered without draining and/or pressing and the processing is continuous.

Worldwide, decanters are commonly used on many different products to remove solids from liquids. When the use of the Hiller decanter was first considered for commercial-scale grape processing, the idea was met with great resistance (especially from Germany). Yield and the quality of the juice obtained were the main concerns. After trialling the Hiller decanter for the past five vintages in South Africa, it can be concluded that it has the possibility of making a significant contribution to process optimisation in wineries. This article reports on three of the trials conducted in the past five years.

Materials and methods

The Hiller decanter used in the trials was a small unit, capable of processing 10 tonnes of grapes per hour. The grapes entered the system either destemmed and crushed, or destemmed and uncrushed. Separation of juice and solids happened within minutes. The pomace, mainly grape skins and pips, contained less than 50 ℓ of juice per tonne of grapes.

Trials were performed with Sauvignon Blanc and Chardonnay at Groote Post; Sauvignon Blanc at Boschendal; and Chardonnay and Pinot Noir for the production of Méthode Cap Classique (MCC) sparkling wine at Graham Beck, Robertson.

Analyses performed on both decanter and control juice and the resulting wines included: juice yield, total phenols, pH, titratable acidity (TA), potassium concentration, as well as informal sensory evaluations of the final wines. The analyses were performed by Wine Quality Consultants and Vinlab.

juicerecovery_figuur1_thumbnail

FIGURE 1. From grapes to juice in minutes.

 

FIGURE 2. Decanter processing principal.
FIGURE 3. Skins after separation of juice.
FIGURE 4. Almost no juice in skins after decanting. FIGURE 5. Pinot Noir (MCC juice) after settling and flotation: normal, decanter and press fraction. FIGURE 6. Chardonnay juice after separation: normal free run, from press and from decanter.

 

Results

Yield

In all the trials a higher yield of quality free-run juice was obtained when compared with standard processes. In general, the yield obtained from the decanter (only one fraction instead of two as in standard processing) exceeded 700 ℓ/tonne for dry-land grapes and 800 ℓ/tonne for irrigated vines. The free-run juice yield for standard processing was between 350 and 550 ℓ/tonne of grapes crushed, depending on the cultivar and the cellar infrastructure.

Analysis

The differences in degrees Balling, TA, pH and YAN (yeast assimilable nitrogen) between normal and decanter juice were insignificant. The decanter did not alter the juice composition for these parameters. Juice processed with the decanter had lower potassium and total phenol concentrations than standard processing. However, higher potassium and total phenol concentrations were observed in juice kept for longer than 30 minutes and at higher temperatures for both decanter and control juice.

Sensory

The wines made from the first decanter trials done at Groote Post with Sauvignon Blanc and Chardonnay grapes were used for the same blends as the standard processed wine. No negative quality effects were thus observed.

The 2013 trials with Sauvignon Blanc at Boschendal were judged by 14 experienced winemakers using the triangular taste method and ranking:

  • The judges were unable, with the triangular tasting, to indicate significant differences between the Hiller decanter and the control wines.
  • The ranking results of the wines were insignificant, with no preferred wine.

Wines (MCC base) were made from grapes processed at Graham Beck in Robertson:

  • On Chardonnay base wines the judges indicated with the triangular tests a slight difference between the Hiller decanter and the control wines.
  • The Hiller wines were preferred and showed more citrus and fresh fruit than the control Chardonnay wines.
  • The Pinot Noir MCC base wine from the Hiller decanter had less red colour than the control wine. The MCC wine made from decanter processing was as good as the control wine.

The way forward

Decanter technology allows for rapid juice processing in cellars, without the need for large and expensive equipment such as drainers and presses. The combination of high quality and high yield makes the system attractive for quality and bulk-wine producers alike.

Acknowledgements

We thank the following winemakers that helped with the development of the Hiller grape process by providing their cellar facilities and grapes:

  • Lukas Wentzel, Groote Post.
  • Len Knoetze and Renier van Greunen, Namaqua Wines.
  • Abé Beukes, Darling Cellars.
  • Kallie van Niekerk and Kobus Gerber, Distell.
  • JC Bekker, Lizelle Gerber and Bertho van der Westhuizen, Boschendal.
  • Bowen Botha and his team and Francois Weich, Robertson Wines.
  • Pieter Ferreira, Graham Beck Wines.

For further information, contact Hans Perabo or Brett Rightford at udec@udecprocess.com.

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