Chardonnay Riesling

The effect of pre-ferment glutathione addition on Chardonnay and Riesling wine characteristics

Kathleen Cuijvers1, Ross Sanders2,3, Allie Kulcsar1, Marlize Bekker1, Dimitra Capone2,3, Damian Espinase Nandorfy1 , David Jeffery2,3 , Simon Schmidt1 1 The Australian Wine Research Institute, PO Box 197, Glen Osmond (Adelaide) SA 5064, Australia, 2 Department of Wine and Food Science, University of Adelaide, PMB 1 Glen Osmond, SA 5064, Australia, 3 Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide Corresponding author’s email: [email protected]

Background Conclusions Glutathione (GSH) is a natural product which can participate in • Glutathione loss during fermentation was 60–100 mg/L (Figure redox reactions and act as a precursor to a range of aroma A). compounds. The OIV has posted guidelines on the addition of • No differences in GSH loss between pre- and post-ferment GSH to musts or prior to bottling to protect against oxidation additions were observed (Figure A). phenomena. However, questions remain about the fate of GSH • GSH addition during fermentation had a significant impact on under different addition scenarios and what the impacts might wine flavour profiles: be in varieties other than Sauvignon Blanc. o GSH was associated with ‘flint’ and ‘cheesy’ descriptors in Aims Chardonnay (Figure B). 1. Determine the effects of GSH addition during fermentation o GSH was associated with ‘flint’ and ‘box hedge/cat pee’ on the organoleptic qualities of finished Chardonnay and descriptors in Riesling (Figure D). Riesling wine. • During bottle ageing, a large amount of hydrogen sulfide (H2S) was released (Figures C and E). 2. Evaluate interactions with SO2 in evolution of wine chemistry. o In-bottle H2S development was more pronounced in wines 3. Determine the persistence of GSH during wine maturation. bottled with low SO2 regimes. o In-bottle H2S development was more pronounced in Winemaking Chardonnay. Pilot-scale Chardonnay and Riesling wines were made with the following treatments: Chardonnay Riesling

0.6 mg/L

molecular SO2 B) Sensory assessment D) Sensory assessment Pre-inoculation GSH addition Yellow Colour Pink Tinge 4.5 0.8 mg/L 4.5 Overall Fruit Overall Fruit Fruit Aftertaste Fruit Aftertaste 4 molecular SO2 4 Aroma Aroma Chardonnay 3.5 3.5 Tropical Fruit and Bitter Taste 3 3 Aroma Riesling 2.5 Stone Fruit 0.6 mg/L 2.5 Acidity 2 Aroma 2 Strawberry molecular SO2 Viscosity 1.5 1.5 Aroma Post-inoculation GSH 1 addition 1 0.5 0.8 mg/L 0.5 Overall Fruit Blossom Floral Stone Fruit Stone Fruit 0 0 Flavour Aroma molecular SO2 Flavour Aroma

Overall Fruit Yellow Analysis Flavour Confection… Capsicum Pungent Finished wine was analysed by a trained Aroma Box Hedge/Cat Drain Aroma descriptive sensory panel 3 months post-bottling. Pee Aroma Box Hedge/Cat Honey Aroma Chemical analyses were performed at 3 months, Honey Aroma Flint Aroma Pee Aroma 18 months and 22 months post-bottling. Cheesy/Baby Flint Aroma Sick Aroma

Control Pre-Inoculation Post-Inoculation Control Pre-Inoculation Post-Inoculation

High SO2 High SO2 High SO2 High SO2 High SO2 High SO2

Low SO2 Low SO2 Low SO2 Low SO2 Low SO2 Low SO2

C) Post-fermentation H2S development E) Post-fermentation H2S development

A) Evolution of GSH concentration in Chardonnay and Riesling during fermentation and wine ageing

Reference Resolution OIV-OENO 445-2015 addition of glutathione to must.

The AWRI and the University of Adelaide are members of the Wine Innovation Cluster.