 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

Zoning methods in relation to the plant

The characterization of the plant is the obliged pathway between the environment and the product. The responses of the plant amplify or reduce the variations of the environment, while determining directly the type and the quality of the products. These results are inscribed inside the Viticultural Terroir Unit (VTU). VTU is the complex interaction between the Basic Terroir Unit or BTU (interaction mesoclimate x soil/subsoil), the genotype (variety x rootstock), the management system, the oenological technologies. Thus, at the most complex level, a global biological triptych is found again : environment (source) x plant (structure) = produced and exchanged substances.

The colour pattern of flower arrangements influence wine tasters’ sensory description

The arrangements of flowers and wine counterparts are inextricably linked. Whether a fundamental aspect of tablescaping or acolytes to broader entertainment rituals, they have an entangled history since ancient times. The aim of this contribution is to verify the influence of visually delicate and robust flower arrangements on individual description of wines. Changes in the sensory description of wines were investigated during subjects’ (thirty-two participants) exposure to three different conditions: the presence of delicate, robust, or totally absent flower arrangements.

The estimation of the clear-sky effective PAR resources in a mountain area

Irrigation of vineyards is a matter of controversial arguments at areas of high quality wine production. Besides, the effects of the water in the plant are closer related to the water availability than to the irrigation regime.

Automated detection of downy mildew in vineyards using explainable deep learning

Traditional methods for identifying downy mildew in commercial vineyards are often labour-intensive, subjective, and time-consuming.

Water status response of Vitis vinifera L. cv Cabernet Sauvignon during the first years within the long-term VineyardFACE (Free Air Carbon dioxide Enrichment) study

Understanding grapevine responses to increasing atmospheric CO2 (aCO2) concentrations is crucial for assessing the impact of climate change on viticulture. Previously, at the VineyardFACE (Free Air Carbon dioxide Enrichment) experiment in Geisenheim, leaf gas exchange measurements were made as Vitis vinifera cv. Cabernet Sauvignon established from planting (2014 to 2016) under aCO2 or elevated CO2 (eCO2, aCO2 + 20%) concentrations. Contrary to many preceding observations with grapevines and other perennial plant species the young vines showed an increased intrinsic water use efficiency (WUEi) that was mainly associated with an increase in net assimilation (A) rather than a decrease in stomatal conductance (gs) under eCO2.