UV-C irradiation in the post-harvest period on Cabernet Sauvignon grapes

by | Jul 30, 2021 | Winetech Scan

The aim of this study was to investigate the effects of UV-C irradiation on Cabernet Sauvignon wine characteristics. Previous studies reported increases in anthocyanin concentrations in Summer Black, Red Globe and Isabel grapes and the researchers of this study was therefore interested what the effects could be on one of the world’s noble wine grape varieties and its wines.  UV-C irradiation in food is safe for human consumption, as it does not accumulate in food, nor does it make food radioactive.

Project layout

The study took place in Brazil. 60 kg Cabernet Sauvignon grapes were harvested at commercial maturity stage and sorted to remove unripe and ruptured grapes. The grapes were divided into three groups with four replicates each. One group served as control and the other two groups were exposed to 2 and 3 kJ m-2 UV-C irradiation. After irradiation the grapes were stored for three days under a natural atmosphere at +/- 20°C to develop a physiological response.

After the three days the grapes were subjected to a standard red winemaking protocol that included the addition of SO2 (50 ppm), pectinolytic enzyme and a fermenting yeast. Fermentation took eight days at 20°C. Cap management took place by stirring. At the end of fermentation another 50 ppm SO2 was added, and the wine was filtered, bottled and stored for six months at 18°C.

Physicochemical (RS, pH, alc. etc.), colour and sensory analyses were performed on the wines.

Main results

There were no significant differences between the wines in terms of their physicochemical parameters, meaning UV-C treatment does not affect it.

Both wines made from irradiated grapes had higher concentrations of anthocyanins and its derivatives and were preferred by tasters in terms of visual, aroma and taste attributes.

The higher UV-C treatment wine compared to the control had an increase of 22.52% monomeric anthocyanin (anthocyanin bound to glucose), 59.32% increase in pyranoanthocyanins (anthocyanins bound to fermentation products such as pyruvate, oxaloacetate or acetaldehyde), 92.31% increase in direct condensation products (anthocyanins bound to flavanols such as cathecin) and 62.78% in acetaldehyde mediated condensation products (anthocyanin-acetaldehyde-tannin complexes).

Significance of the study

This study, that was done on small scale, warrants further investigation into the possible commercial use of UV-C irradiation to increase red wine colour and sensory attributes of red wines without the need for picking grapes at high (over 24°Balling) sugars.

Reference

Gindri, R.V., Pauletto, R., Franco, F.W. et al. Grape UV-C irradiation in the postharvest period as a tool to improve sensorial quality and anthocyanin profile in ‘Cabernet Sauvignon’ wine. J Food Sci Technol (2021). https://doi.org/10.1007/s13197-021-05191-5

Image copyright: Pixabay

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