 IVES 9 IVES Conference Series 9 The use of fluorescence spectroscopy to develop a variability index and measure grape heterogeneity

The use of fluorescence spectroscopy to develop a variability index and measure grape heterogeneity

Abstract

AIM This work aims to investigate fluorescence spectroscopy as a tool to assess grape homogenates to discriminate between samples of varying maturities and to develop an index to objectively characterise the level of grape heterogeneity present in any given vineyard.

METHODS Cabernet-Sauvignon grape bunches were sampled every ten days from veraison through to harvest from the Coonawarra Geographical Indication of South Australia in 2020. After sorting into maturity classes using density baths,1 berries were homogenised and an Aqualog spectrophotometer was used to record the excitation emission matrix (EEM)2 of each maturity class at each sample date. The pre-processed EEM data underwent parallel factor analysis (PARAFAC) to identify the relevant fluorescence regions that discriminated samples based on maturity. The grape homogenate EEM dataset was then used to formulate a variability index.

RESULTS Chlorophyll and anthocyanin fluorescence signals were identified from EEM data at excitation wavelengths in the range 250 – 700 nm and emission wavelengths between 400 – 800 nm in grape homogenate samples using PARAFAC. Discrimination between samples depending on maturity was achieved using PARAFAC. The variability index was calculated and levels of grape heterogeneity were quantified.

CONCLUSIONS

This work demonstrated the possibility of using grape homogenate EEM data, particularly in the region of chlorophyll and anthocyanin fluorescence, to objectively measure grape heterogeneity by developing a variability index. Grape heterogeneity has been shown to impact Cabernet-Sauvignon wine chemical profile and sensory characteristics.3 Therefore, a tool to analyse grape heterogeneity within a winery could aid viticultural and winemaking decisions to achieve wines of targeted quality and style.

DOI:

Publication date: September 7, 2021

Issue: Macrowine 2021

Type: Article

Authors

Claire Armstrong

Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide. ,Adam GILMORE, HORIBA Instruments Inc., Piscataway, United States. Paul BOSS, CSIRO Agriculture and Food and Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide. Vinay PAGAY, Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide. David JEFFERY, Australian Research Council Training Centre for Innovative Wine Production, The University of Adelaide.

Contact the author

Keywords

chemometrics, colour, grape maturity, parafac, vineyard variability

Citation

Aromatic profile of six different clones of Chardonnay grape berries in Minas Gerais (Brazil)

Aromas are one of the key points in food analysis since they are related to character, quality and consequently consumer acceptance. It is not different in the winery industry, where the aromatic profile is a combination of viticultural and oenological practices. Based on the development of more aromatic clones and on the potential to produce sparkling wines at Caldas, in the southern region of Minas Gerais (Brazil) (21°55´S and 46°23´W, altitude 1,100m), the aim of this work was the determination of volatile compounds in six different clones of Chardonnay grape berries to better understand which compounds add bouquet to the wine, and additionally comprehend the impacts of the edaphoclimatic and annual conditions on the improvement of grape-growing and winemaking practices.

Use of computational modelling for selecting adsorbents for improved fining of wine

The occurrence of faults and taints in wine, such as those caused by microbial spoilage or various taints, have resulted in significant financial losses to wine producers. The wine industry commits significant financial resources towards fining and taint removal processes each year. Fining involves the addition of one or more adsorptive substrates to juice or wine to bind certain components, thus reducing their concentration [1]. However, these processes are often not selective and can also remove desirable flavour and aroma compounds.

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.

Physiological response to drought and heat stress in the leaves of table grape varieties

Increasingly pronounced climate changes, including prolonged drought periods, pose a significant challenge to the cultivation of table grape varieties.

A applied viticultural zoning, based on the “secteurs de la reference” methodology, in the Cognac vineyard (France)

Dans les Charentes, en réponse à une crise de production du vignoble destiné à la production de Cognac, un plan de diversification viticole pour des vins de pays de qualité est mis en place. Il nécessite une connaissance des sols et de leurs caractéristiques viticoles pour orienter le choix des types de vins et adapter l’itinéraire technique de production.