GiESCO 2019 banner
IVES 9 IVES Conference Series 9 GiESCO 9 Application of a fluorescence-based method to evaluate the ripening process and quality of Pinot Blanc grape

Application of a fluorescence-based method to evaluate the ripening process and quality of Pinot Blanc grape

Abstract

Context and purpose of the study – The chemical composition of grape berries at harvest is one of the most important factors that should be considered to produce high quality wines. Among the different chemical classes which characterize the grape juice, the polyphenolic compound, such as flavonoids, contribute to the final taste and color of wines. Recently, an innovative non-destructive method, based on chlorophyll fluorescence, was developed to estimate the phenolic maturity of red grape varieties through the evaluation of anthocyanins accumulated in the berry skin. To date, only few data are available about the application of this method on white grape varieties. The aim of the present study was to evaluate the quality and the ripening process of Pinot blanc grape by a non-destructive fluorescence-based sensor.

Material and methods – The study was performed on two vineyards of cv. Pinot blanc located in the Adige Valley (South Tyrol, Bolzano), in two consecutive vintages. The vineyard differed in the row orientation, east-west or north-south, and then on the sun light exposure of the grape-bunches. The grape phenolic maturity was assessed on intact berries by six measurements from bunch closure to harvest time. In each vineyard, 25 grape-bunches per row sides were flashed by Multiplex® 3.6 (Force-A, Orsay, France), for a total of 3 rows and 150 grape-bunches/measurement. The instrument indices of chlorophyll (SFR_R) and flavonols (FLAV_UV) were considered. Standard grape maturity tests were performed to assess total soluble solids (TSS) and total acidity content of the grape juice by spectroscopic method. At maturity the grapes were processed with a standard vinification protocol for white wines. Total polyphenolic content of wines was determined by a spectrophotometric analysis.

Results – A linear decrease of SFR_R index in the berry-skin during the grape ripening period was recorded. Interestingly, SFR_R values negative correlated with the TTS accumulation in Pinot blanc berries. On the other side, positive correlations between SFR_R and titratable acidity, malic acid and tartaric acid content, were observed. The FLAV_UV index showed an increasing linear trend during the grape ripening period. At harvest, significant difference in FLAV_UV index between the two vineyards was observed. Looking more deeply inside the data, the berry-skin FLAV_UV index significantly differed among the four sun-light expositions, with greater values recorded for the grape-bunches located in south and east sides of the vineyard rows. These results are in accordance with the available literature on the role flavonols as sun-burn protection compounds. Interestingly, the total polyphenolic content of the produced wines showed a positive correlation with the final FLAV_UV values measured in the berry-skin. In conclusion, the Multiplex® indices could improve precision viticulture strategies, such as the implementation of precision harvest practices. Indeed, SFR_R index could be used to indirectly evaluate the whole ripening process of white grapes in term of grape sugar content and acidity, while FLAV_UV could provide useful indications to winemakers about taste of final product. Future studies will be necessary to better correlate the berry-skin FLAV_UV values and the flavours of white wine.

DOI:

Publication date: September 29, 2023

Issue: GiESCO 2019

Type: Poster

Authors

Selena TOMADA1*, Florian PICHLER1, Julia MARTINELLI1, Giovanni AGATI2, Valentina LAZAZZARA3, Martin ZEJFART4, Fenja HINZ3, Ulrich PEDRI4, Peter ROBATSCHER3, Florian HAAS1

1 Department of Viticulture, Laimburg Research Centre, BZ, Italy
2 Istituto di Fisica Applicata ‘Nello Carrara’, CNR, FI, Italy
3 Laboratory for Flavours and Metabolites, Laimburg Research Centre, BZ, Italy
4 Department of Enology, Laimburg Research Centre, BZ, Italy

Contact the author

Keywords

chlorophyll, flavonols, grape, Multiplex®, quality, Pinot blanc.

Tags

GiESCO | GiESCO 2019 | IVES Conference Series

Citation

Related articles…

Physiological and growth reaction of Shiraz/101-14 Mgt to row orientation and soil water status

Advanced knowledge on grapevine row orientation is required to improve establishment, management and outcomes of vineyards on terroirs with different environmental conditions (climate, soil, topography) and in view of a future change to more extreme climatic conditions. The purpose of this study was to determine the combined effect of row orientation, plant water status and ripeness level on the physiological and viticultural reaction of Shiraz/101-14 Mgt.

Effects of mechanical leafing and deficit irrigation on Cabernet Sauvignon grown in warm climate of California

San Joaquin Valley accounts for 40% of wine grape acreage and produces 70% of wine grape in California. Fruit quality is one of most important factors which impact the economical sustainability of farming wine grapes in this region. Due to the recent drought and expected labor cost increase, the wine industry is thrilled to understand how to improve fruit quality while maintaining the yield with less water and labor input. The present study aims to study the interactive effects of mechanical leafing and deficit irrigation on yield and berry compositions of Cabernet Sauvignon grown in warm climate of California.

The effects of cane girdling on berry texture properties and the concentration of some aroma compounds in three table grape cultivars

The marketability of the table grapes is highly influenced by the consumer demand; therefore the market value of the table grapes is mainly characterized by its berry size, colour, taste and texture. Girdling could cause accumulation of several components in plants above the ringing of the phloem including clusters and resulting improved maturity. The aim of the experiments was to examine the effect of girdling on berry texture characteristics and aroma concentration.

Different yield regulation strategies in semi-minimal-pruned hedge (SMPH) and impact on bunch architecture

Yields in the novel viticulture training system Semi-Minimal-Pruned Hedge (SMPH) are generally higher compared to the traditional Vertical Shoot Positioning (VSP). Excessive yields have a negative impact on the vine and wine quality, which can result in substantial losses in yield in subsequent vintages (alternate bearing) or penalties in fruit quality. Therefore yield regulation is essential. The bunch architecture in SMPH differs from VSP. Generally there is a higher amount but smaller bunches with lower single berry weights in SMPH compared to VSP.

Grape composition and wine quality of Muscat Hamburg cultivar after a specific inactivated dry yeast application as adaptation strategy to climate change

In a climate change context, the management of Mediterranean vineyards should be adapted to the new environmental conditions. Predictive models underline that in the future the most of the Mediterranean vineyard regions is expected to experience further warming events producing challenges in ripening balanced fruit. It is already registered that in warm and dry summers, the ripening process is faster and the balance between phenolic and technological (sugar) maturity may not be the desirable. This study investigates the use of specific inactivated yeast derivatives sprayed on the entire canopies of field grown cv Muscat Hamburg vines.