Shikimic acid concentration in white wines produced with different processing protocols from fungus-resistant grapes growing in the Alps

Shikimic acid (SHA) has been used for years as variety marker in fraud control, especially for 'Pinot Noir', 'Pinot Gris' and 'Pinot Blanc' with very low amounts. Until now no data for the hybrid grapes 'Bronner', 'Helios', 'Johanniter', 'Muscaris', 'Solaris' and 'Souvignier Gris' from the Viticultural Institute of Freiburg (Germany) were published. These white varieties with resistance against downy and powdery mildew are increasingly planted in some Alpine Italian regions. Data obtained from white wines of different vintages and vineyards in Trentino by HPLC showed that 'Johanniter' had the highest average content of SHA, while 'Solaris' and 'Muscaris' had much lower levels. These data are compared with previously published data for Italian wines of 19 white varieties and new data for 'Müller-Thurgau' and 'Yellow Muscat' wines. For a subset of 10 grape batches the influence of four different winemaking protocols on the amount of SHA was investigated. Increasing levels were found in the expected order from direct pressing to pressing of crushed-destemmed grapes (+28 %), short maceration of crushed-destemmed grapes before pressing (+37 %) and a 7-day skin-contact fermentation (+107 %).