South Africa Wine Technical Yearbook 2025

JANUARY/FEBRUARY

SHUTTERSTOCK

Sunscreen for Sauvignon blanc By Carien Coetzee

Many viticultural management practices directly affect fruit sunlight exposure and, therefore, sunburn incidence. Practices such as canopy management, row orientation, trellis and training systems, and soil and irrigation management strategies can all affect the degree of sunburn damage during extreme climatic conditions. However, sunburn protective applications are increasingly attracting attention in research and commercial settings, and international grape growers are getting creative in protecting their crops from the elements during extreme weather conditions. Some of these newer protective measures include the use of netting, antitranspirants, hydrocooling One of the particle film-forming particle technologies is an inert chemical reflectant named kaolin (aluminium phyllosilicate, Al 2 Si 2 O 5 (OH) 4 , nanoparticles), a white clay that can reflect ultraviolet and infrared radiation. When sprayed over the canopy, the light and temperature conditions around the leaves and bunches change, directly affecting the vine’s gas exchange rate. Its ability and particle film-forming products. Kaolin – a chemical light reflectant

Introduction Sunburn of grapes is a physiological disorder resulting from a combination of excessive photosynthetically active radiation, ultraviolet radiation and elevated temperatures that can be exacerbated by other stress factors such as water deficit. The appearance of brown and necrotic spots on the epidermis of grapes (which can further develop into the complete desiccation of the berries), severely affects the commercial value and yield of the cultivated fruit. Depending on the severity of the damage, wine grapes can be downgraded in quality due to sunburn damage, resulting in economic loss. Abstract Kaolin is a chemical reflectant that has the potential to significantly reduce berry temperature, sunburn and other berry damages associated with cluster solar exposure while maintaining the concentration of important constituents such as acidity and sugar and maintaining (or even improving) yield.

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TECHNICAL YEARBOOK 2025