Effect of Fungal Disease Damage on Acetaldehyde and Volatile Acidity in Wines Produced from Rkatsiteli, Chinuri and Khikhvi Grapes
Marina Khositashvili1* 
, Medea Ormotsadze1 ,
Lia Kotorashvili1 , and Gaga Buishvili2
Abstract. Fungal diseases of grapevine can substantially alter grape composition and, consequently, the quality parameters of the resulting wines. This study evaluated the effect of fungal disease damage on acetaldehyde concentration and volatile acidity in wines produced from three Georgian white grape cultivars: Rkatsiteli, Chinuri and Khikhvi. Healthy grapes and grapes showing fungal disease symptoms were processed by microvinification according to the classical European white-wine method. Alcoholic fermentation proceeded with indigenous yeasts and fermentation intensity was monitored gravimetrically. Acetaldehyde was determined by static headspace gas chromatography–mass spectrometry (HS–GC–MS), whereas volatile acidity was measured using official OIV methods. Volatile acidity increased in every wine produced from diseased grapes, although the magnitude of the effect depended on cultivar and juice fraction. The most pronounced increase occurred in Rkatsiteli wine, from 0.67 to 3.33 g/L, while acetaldehyde decreased slightly from 60 to 56 mg/L. In Chinuri and Khikhvi wines, acetaldehyde remained within 12–15 mg/L, whereas volatile acidity in diseased variants reached 1.37–1.54 g/L. The results indicate that increased volatile acidity is the clearest technological expression of fungal damage in the investigated wines. Because grapes affected by downy mildew and powdery mildew were not processed as separate experimental groups, the independent effects of the two diseases could not be distinguished and should be evaluated in a subsequent experiment.
Keywords: fungal grapevine diseases, Plasmopara viticola, Erysiphe necator, acetaldehyde, volatile acidity, Rkatsiteli, Chinuri, Khikhvi, wine quality