Sunblock for wine grapes

While in Malta and the rest of the northern hemisphere vines are winter dormant, some antipodean vignerons are busy slapping on sunblock on their ripening grape crop as the summer heat flares up.While in Malta and the rest of the northern hemisphere vines are winter dormant, some antipodean vignerons are busy slapping on sunblock on their ripening grape crop as the summer heat flares up.

While a certain amount of warmth and sunshine is necessary to ripen grapes, too much can cause damage. Extreme heatwaves and premature vintages are occurring more frequently in foreign wine regions where the mercury often rockets over 45°C.

Exposed grapes can get damaged by ultraviolet and infrared radiation from intense sunlight. Scorching heat will worsen the situation because leaves wilt and as a result provide less shade, causing grape berries to shrivel or suffer sunburn.

This may lead to excessive grape sugar levels resulting in unbalanced wines with a lack of acidity, too much alcohol and undesirable phenolic and other off flavours.

In Malta, where sea breezes have a cooling effect, smart viticulturists mitigate any possible damage by employing canopy management to ensure protection for grape bunches from the sun by the vine’s own leaves (pretty much like wearing a sombrero). But in hotter countries, growers are rising to the challenge of adaptation to limit serious harm to their harvest by applying sunscreen onto grapes.

The unusual practice has little in common with the story I heard 10 years ago – and chuckled about – of a hip Napa winery applying a home-brew concoction of aloe vera and yucca extract. Nowadays, agricultural sun creams are mass-produced and apparently used more regularly in sweltering vineyards, especially in the hot Hunter Valley, Barossa and Eden Valley regions of Down Under.

Recent research shows that the newly-developed applications actually work. Protective sprays consist of mainly dissolved organic kaolin clays and are applied on to the vine’s fruit zone. When the clay solution dries, it forms a dry deposit which paints grape berries and lush, green vineyards whitish to reflect the sunlight which in turn reduces heat stress.

Grapes are not the only fruit sensitive to intense ultraviolet rays. Sun protection is also applied to other plant crops such as apples, pears, melons and tomatoes in many countries around the world.

The use of grape sunblock overseas may alarm some wine lovers. However, the clay-based powder precipitates during the vinification process and the manufacturers of these protective products claim the application does not by itself affect the wine’s flavour.

This article first appeared in The Times of Malta, Friday  29 January 2016

 

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