An Automatic Cooling System to Cope with the Thermal–Radiative Stresses in the Pignoletto White Grape

Recent climatic extremes, characterized by hot and dry summers, threaten grape yield and berry composition, increasing the need for sustainable mitigation strategies. In this study, a fruit-zone cooling system was tested to reduce sunburn damage and improve vine performance. The system integrates proximal sensors and an automatic misting actuator, triggered when the air temperature exceeds 35 degrees C. Over two seasons (2022-2023), trials were conducted on Pignoletto vines subjected to four treatments: control (C), misted without defoliation (C + FOG), defoliated (DEF), and defoliated plus misted (DEF + FOG). The effects on microclimate, yield, berry sunburn, and berry composition were evaluated. Misting consistently reduced both air and berry temperature. Treated vines showed increased yield, mainly due to reduced sunburn and higher cluster weight. Although no clear differences in technological maturity were observed, misted vines tended to retain higher acidity under extreme heat. Flavonol synthesis was unaffected by cooling but stimulated by increased light exposure, being higher in defoliated vines. Volatile compounds analysis highlighted misting's moderating effect on oxidative stress and aroma profile shifts, particularly during the hotter season. Overall, the cooling system proved effective in mitigating summer stress, offering a promising tool for preserving yield and berry composition in white cultivars under climate change.