The effects of antioxidants and gas sparging on New Zealand white wines

Abstract

AIM: This study aims to investigate the effects of different conditions of grape processing or fermentation on the aroma profile of New Zealand white wines.

METHODS: Experiments have been designed to study how glutathione and ascorbic acid impact on the aroma compounds of Sauvignon Blanc and Pinot Gris wines. Attention was also paid to the effectiveness of two gas sparging regimes (oxygen and nitrogen), applied during fermentation, on the removal of reductive sulfur aromas in Sauvignon Blanc wines.

RESULTS: Additions of glutathione to the grape juices increased the levels of polyfunctional mercaptans in the finished wines. The lowest levels of polyfunctional mercaptan compounds were found in the wines with little supplementary antioxidants added. A high level of the joint combination of ascorbic acid and glutathione provided the wines with even higher production of polyfunctional mercaptans. Increasing the amount of elemental sulfur addition to the grape must before pressing led to an increase in the formation of several thiol compounds, including some unwanted reductive compounds. Few changes were observed in the concentrations of aroma compounds when the juices were sparged with nitrogen during fermentation. Additions of oxygen during fermentation led to some decrease in the concentration of polyfunctional mercaptans for the 10 mg/L sulfur additions, but did not significantly remove reductive aroma compounds. 

CONCLUSIONS

This study has demonstrated a positive benefit to the formation of polyfunctional mercaptans with passionfruit/ tropical aromas, from additions of glutathione and ascorbic acid at harvest. The oxygen or nitrogen applied during fermentation did not result in the removal of undesirable reductive aroma compounds. Further trials are needed to examine increased oxygen as well as nitrogen dosages during fermentation, and their effects on reductive compounds.

DOI:

Publication date: September 15, 2021

Issue: Macrowine 2021

Type: Article

Authors

Xiaotong Lyu 

School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand,Leandro Dias ARAUJO, School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand Siew-Young QUEK, School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand Wessel. J. DU TOIT, Institute for Grape and Wine Sciences/Department of Viticulture and Oenology, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Paul. A. KILMARTIN*, School of Chemical Sciences, University of Auckland, Private Bag 92019, Auckland, New Zealand

Contact the author

Keywords

sauvignon blanc, pinot gris, antioxidants, glutathione, ascorbic acid, reductive compounds, oxygen, nitrogen, polyfunctional mercaptans

Citation

Related articles…

Identification, quantification and organoleptic impact of « dried fruit » molecular markers in Merlot and Cabernet Sauvignon grapes and in red wines

The aromas found in young Bordeaux red wines made with Merlot and Cabernet Sauvignon suggest a complex mixture of aromas of fresh red fruits such as cherry or blackberry for Merlot, and strawberry or blackcurrant for Cabernet Sauvignon. The aromas of these wines are closely linked with the maturity of the grapes. The climate change that has occurred during the last decade in Bordeaux has induced changes in the ripening conditions of grape berries. It is now widely admitted that over-ripening of the berries during hot and dry summers results in the development of characteristic flavors reminiscent of cooked fruits (fig, prune). The presence of these overriding odors found in both musts and young wines affects the quality and subtlety of the wine flavor and may shorten its shelf life.

Quantification of quercetin and quercetin-3-glucoside in Nebbiolo red wines

Quercetin-3-glucoside, a grape flavonol defence metabolite, is extracted during winemaking and may undergo subsequent degradation in wines. Hydrolysation reactions lead to the formation of the aglycone quercetin, which presents limited solubility in the wine matrix and can induce visible precipitations.

Towards more coherent rules for alcohol labelling in the European Union

In its 2020 beating cancer plan, the european commission announced plans for mandatory warning signs for alcoholic beverages. However, no concrete legislative proposal has been put forward so far. Instead, ireland passed national legislation in 2023 that requires warning signs for all alcoholic beverages from 2026. Despite significant effects for the common market, the eu commission did not this challenge this law in the so-called tris notification procedure. We argue that the commission’s inaction is consistent with the case law of the european court of justice: in the absence of harmonized rules, member states have a large margin of discretion to enact national health measures.

Berry shrivel causes – summarizing current hypotheses

Diverse ripening disorders affect grapevine resulting in high economic losses worldwide. The common obvious symptom is shriveling berries, however the shriveling pattern and the consequences for berry quality traits are distinct in each disorder. Among them, the disorder berry shrivel is characterized by a reduced sugar accumulation short after the onset of berry ripening leaving the clusters unsuitable for wine processing. Although our knowledge on BS increased recently, potential internal or external triggers contributing to the induction of BS are yet to be explored.

A climatic characterisation of the sub-Appellations in the Niagara Peninsula wine region

This study used climatic and topographic data to characterize the sub-appellations that have been recently delineated in the Niagara Peninsula viticulture area in order to assess their potential for ripening early to late season Vitis vinifera varieties. No major differences were found in the ripening-period mean temperatures, but major differences in the diurnal temperature ranges were observed.