 IVES 9 IVES Conference Series 9 Macrowine 9 Macrowine 2021 9 Chemical diversity of 'special' wine styles: fortified wines, passito style, botrytized and ice wines, orange wines, sparkling wines 9 The effects of antioxidants and gas sparging on New Zealand white wines

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

Leaf necrosis induced by the insecticide carbaryl in Vitis rupestris ‘B38’

Carbaryl is an acetylcholine esterase inhibitor-type insecticide used for pest control on grapevine. We repeatedly observed the occurrence of interveinal leaf necrosis following carbaryl spray application in a Vitis rupestris x Vitis riparia F1 hybrid progeny vineyard. Spray applications induced necrosis in this progeny under both Missouri and New York field conditions an approximate one-to-one sensitive-to-insensitive segregation ratio and with 42% concordance. Results of subsequent in vitro experiments established causality between carbaryl treatment and leaf necrosis and confirmed the pattern of segregation observed in the field. We consistently map this phenotype to a major QTL on chromosome 16 of the female parent V. rupestris ‘B38’ regardless of whether we used field or in vitro-generated phenotype data.

Exploring the impact of different closures on tannin evolutions by using metabolomic approach

Condensed tannins (CTs), polymers of flavan-3-ols, are a class of polyphenolic compounds that play a significant role in the organoleptic qualities of red wines, particularly influencing color, astringency and bitterness. These properties are highly dependent on size and structure of these compounds.

Impact of press fractioning on Pinot noir and Pinot meunier grape juice and wine compositions and colour

The separation of different grape juice press fractions is an important step in the production of sparkling base wines. A complete press cycle for this style of wine is a series of pressure increases (squeezes) resulting in variations in juice composition during the press cycle. After alcoholic fermentation, wines obtained from grape juices also exhibit strong differences for numerous characteristics. Nevertheless, there is no statistical study of the impact of the press cycle on grape juices and wine colour/composition. So, the aim of this study (vintage 2018) was to investigate the changes in composition and colour parameters of Pinot noir and Pinot meunier grapes juices, as well as their corresponding wines, during the pressing cycle.

Lactiplantibacillus plantarum – A versatile tool for biological deacidification

Malolactic fermentation (MLF) is a secondary wine fermentation conducted by lactic acid bacteria (LAB). This fermentation is important in winemaking as it deacidifies the wine, converting L-malic acid into L-lactic acid and carbon dioxide, and it contributes to microbial stability. Wine pH is highly selective, and at pH below 3.5 generally only strains of O. oeni can survive and express malolactic activity, while under more favorable growth conditions above pH 3.5, species of Lactobacillus and Pediococcus may conduct the MLF. Among the LAB species Lactiplantibacillus plantarum strains have shown most interesting results under hot climate conditions, not only for their capacity to induce MLF, but also for their homo-fermentative properties towards hexose sugars, which makes them suitable for induction of MLF in high pH and high alcohol wines, when inoculated at the beginning of alcoholic fermentation.

Altered lignans accumulation in a somatic variant of Tempranillo with increased extractability of polyphenols during winemaking

Vegetative propagation of grapevines can generate spontaneous somatic variations, providing a valuable source for cultivar improvement. In this context, natural variation in the composition of phenolic compounds in grapevine berries and seeds stands as a pivotal factor in crafting wines with diverse oenological profiles from the same cultivar. To deepen on the understanding of the physiological and genetic mechanisms driving somatic variation in grape phenolics, here we characterized a somatic variant from Tempranillo Tinto, the clone VN21, that exhibits an intense reduced berry skin cuticle and increased extractability of phenolic compounds during wine fermentation.