# Chemical and sensory effects of macro-oxygenation and air sparging coupled with oxidation-reduction potential (ORP) monitoring in Syrah wines

## TL;DR

This study explores how different oxygenation techniques during Syrah wine fermentation affect chemical and sensory properties.

## Contribution

The study introduces a novel approach combining macro-oxygenation and ORP monitoring to enhance wine quality.

## Key findings

- Macro-oxygenation increases phenolics and preserves esters in Syrah wines.
- Redox-controlled air sparging reduces perceived reduction and enhances floral aromas.
- Syrah wines can tolerate a wide oxygen range during fermentation without negative effects.

## Abstract

The chemical and sensory effects of different cap management regimes and ORP modulation during red wine alcoholic fermentation were investigated in Syrah wines produced with punch downs (PD); air sparging triggered at oxidation-reduction potential (ORP) –40 mV (RedoxCon); macro‑oxygenation with oxygen (MOX); and double-rate macro‑oxygenation with oxygen (2MOX). RedoxCon received 1125 % and 513 % more O2/L than MOX and 2MOX. ORP values were lowest in MOX and 2MOX, leading to wines with 30 % and 11 % more color, 41 % and 27 % more tannin, and 31 % and 32 % more total phenolics relative to PD and RedoxCon, respectively. MOX and 2MOX contained 61 % and 53 % more esters than PD, whereas terpenoids were higher in PD and RedoxCon. RedoxCon enhanced spicy and floral aromas, 2MOX intensified fruit aromas; both MOX and 2MOX increased reduction aroma. Macro‑oxygenation enhanced phenolics and preserved esters by maintaining lower redox environments than the other treatments and possibly lessening volatile stripping. Cool climate Syrah can accommodate oxygen additions over an 11-fold range during alcoholic fermentation, resulting in wines with distinct chemical and sensory features.

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•Macro-oxygenation boosts the phenolic profile of Syrah wines.•Macro-oxygenation preserves sulfur dioxide and glutathione in Syrah wines.•Redox-controlled air sparging (-40 mV) lowered perceived reduction in Syrah wines.•Redox-controlled air sparging (−40 mV) increased floral aroma in Syrah wines.•Syrah wines can accommodate a 11-fold range of O2 add during ferment.

Macro-oxygenation boosts the phenolic profile of Syrah wines.

Macro-oxygenation preserves sulfur dioxide and glutathione in Syrah wines.

Redox-controlled air sparging (-40 mV) lowered perceived reduction in Syrah wines.

Redox-controlled air sparging (−40 mV) increased floral aroma in Syrah wines.

Syrah wines can accommodate a 11-fold range of O2 add during ferment.