terclim by ICS banner
IVES 9 IVES Conference Series 9 CHANGES IN CU FRACTIONS AND RIBOFLAVIN IN WHITE WINES DURING SHORT-TERM LIGHT EXPOSURE: IMPACTS OF OXYGEN AND BOTTLE COLOUR

CHANGES IN CU FRACTIONS AND RIBOFLAVIN IN WHITE WINES DURING SHORT-TERM LIGHT EXPOSURE: IMPACTS OF OXYGEN AND BOTTLE COLOUR

Abstract

Copper in white wine can be associated with Cu(II) organic acids (Cu fraction I), Cu(I) thiol species (Cu fraction II), and Cu sulfides (Cu fraction III). The first two fractions are associated with the repression of reductive aromas in white wine, but these fractions gradually decrease in concentration during the normal bottle aging of wine. Although exposure of white wine to fluorescent light is known to induce the accumulation of volatile sulfur compounds, causing light-struck aroma, the influence on the loss of protective Cu fractions is uncertain. Riboflavin is known to be a critical initiator of photochemical reac-tions in wine, but the rate of its decay under short-term light exposure in different coloured bottles and for wine of different oxygen concentrations is not well understood. This study aims to gain insights into the rate of change in Cu fractions and riboflavin concentrations during the exposure of white wine with different oxygen concentrations and/or different bottle colours to light over a period of days to months.

A Chardonnay wine with an addition of 0.5 mg/L riboflavin, 0.3 mg/L Cu and different concentrations of oxygen (10 and 0.5 mg/L) was exposed to fluorescent light at 20°C in Flint coloured bottles. The wine was also investigated using other coloured bottles (Arctic blue, French green, Antique green and Amber) with the minimum oxygen concentration. The Cu fractions were quantified using colorimetry and riboflavin concentrations measured by ultrahigh-performance liquid chromatography. The results showed that for wine in Flint bottles with low oxygen, light exposure accelerated the decrease in Cu fraction I and II, with the change in Cu fraction I being most pronounced (i.e., a 10-fold decrease in 24 hours). In contrast, high oxygen concentrations resulted in no light-induced decrease in Cu fractions I or II. Riboflavin concen-trations became depleted after only 20 hours of irradiation under high oxygen concentrations, while 0.07 mg/L remained in the wine with low oxygen. The darker coloured wine bottles slowed the changes observed for Cu fractions and riboflavin from a minimum period of hours (i.e., for Flint bottles) to a maxi-mum period of months (i.e., for Amber bottles). Although light is known to induce light-struck aroma in wine, this study has demonstrated it can also accelerate the removal of protective fractions of Cu and this has implications for the general reductive development of wine.

DOI:

Publication date: February 9, 2024

Issue: OENO Macrowine 2023

Type: Article

Authors

Isara Vongluanngam1,2,3*, Xinyi Zhang1,2, John W. Blackman1,2, Leigh Schmidtke1,2,3, Kerry L. Wilkinson3,4, Andrew C. Clark1,2,3

1. School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Locked Bag 588, Wagga Wagga, NSW 2678, Australia
2. Gulbali Institute, Charles Sturt University, Wagga Wagga, NSW 2678, Australia
3. The Australian Research Council Training Centre for Innovative Wine Production, University of Adelaide (Waite Campus), South Australia 5064
4. Discipline of Wine Science and Waite Research Institute, The University of Adelaide, PMB 1, Glen Osmond, SA 5064, Aus-tralia

Contact the author*

Keywords

Riboflavin, Cu fractions, Wine bottle colour, Photo-degradation

Tags

IVES Conference Series | oeno macrowine 2023 | oeno-macrowine

Citation

Related articles…

MODULATION OF YEAST-DERIVED AROMA COMPOUNDS IN CHARDONNAY WINES USING ENCAPSULATED DIAMMONIUM PHOSPHATE TO CONTROL NUTRIENT RELEASE

Yeast-derived aroma compounds are the result of different and complex biochemical pathways that mainly occur during alcoholic fermentation. Many of them are related -but not limited- to the availability of nutrients in the fermentation medium and linked to nitrogen metabolism and biomass produced. Besides, the metabolic phase of yeast also regulates the expression of many enzymes involved in the formation of aroma active compounds. The work investigates the overall effect of continuous supplementation of nutrients during alcoholic fermentation of a grape must on the volatile composition of wines.

Read More

CHEMICAL DRIVERS OF POSITIVE REDUCTION IN NEW ZEALAND CHARDONNAY WINES

According to winemakers, wine experts and sommeliers, aromas of wet stone, mineral, struck match and flint in white wines styles, such as those produced from Vitis vinifera L. cv. Chardonnay, are considered to be hallmarks of positive reduction.1,2 In recent years, the production of Chardonnay styles defined by aroma characteristics related to positive reduction has become more desirable among wine experts and consumers. The chemical basis of positive reduction is thought to originate from the concentration of specific volatile sulfur compounds (VSCs), including methanethiol (MeSH) imparting mineral and chalk notes,3 and benzenemethanethiol (BMT) responsible for struck match and flint.1,4

Read More

METHYL SALICYLATE, A COMPOUND INVOLVED IN BORDEAUX RED WINES PRODUCED WITHOUT SULFITES ADDITION

Sulfur dioxide (SO₂) is the most commonly used additive during winemaking to protect wine from oxidation and from microorganisms. Thus, since the 18th century, SO₂ was almost systematically present in wines. Recently, wines produced without any addition of SO₂ during all the winemaking process including bottling became more and more popular for consumers. A recent study dedicated to sensory characterization of Bordeaux red wines produced without added SO₂, revealed that such wines were perceived differently from similar wines produced with using SO₂ and were characterized by specific fruity aromas and coolness1,2.

Read More

IMPACT OF MINERAL AND ORGANIC NITROGEN ADDITION ON ALCOHOLIC FERMENTATION WITH S. CEREVISIAE

During alcoholic fermentation, nitrogen is one of essential nutrient for yeast as it plays a key role in sugar transport and biosynthesis of and wine aromatic compounds (thiols, esters, higher alcohols). The main issue of a lack in yeast assimilable nitrogen (YAN) in winemaking is sluggish or stuck fermentations promoting the growth of alteration species and leads to economic losses. Currently, grape musts are often characterized by low YAN concentration and an increase of sugars concentration due to global warming, making alcoholic fermentations even more difficult. YAN depletion can be corrected by addition of inorganic (ammonia) or organic (yeast derivatives products) nitrogen during alcoholic fermentation.

Read More

PAIRING WINE AND STOPPER: AN OLD ISSUE WITH NEW ACHIEVEMENTS

The sensory characteristics of wine are a topic studied by several researchers over time, but it continues to be a current and challenging subject. These characteristics are fundamental for the consumer acceptability, which has increasingly aroused their interest to modulate them in line with current market trends and innovation demands. The wine physical-chemical and sensory properties depend on a wide set of factors: they begin to be designed in the vineyard and are later constructed during the various stages of winemaking. Afterwards, the wine is placed in bottles and stored or commercialized.

Read More