Chemical and morphological characterization of Chardonnay and Gewürztraminer grapes and changes during chamber-drying under controlled conditions

In this work, the morphological and chemical properties of Chardonnay and Gewürztraminer aromatic grapes (northern Spain) have been studied with the aim to assess their response to chamber-drying under controlled conditions and compare it with that of Pedro Ximenez grapes (southern Spain). Morphological characteristics, such as weight, size and roundness, and other of the skin such as thickness, enabled discrimination of the two types of grapes varieties. Changes in browning index, colour, antioxidant activity, aroma compounds determined by GC-MS and flavan-3-ols and flavonols concentrations determined by HPLC-DAD were studied during drying. Based on the results, Chardonnay and Gewürztraminer grapes contained increased amounts of flavan-3-ol derivatives, which are the greatest contributors to polymerization and condensation reactions. Also, their smaller size resulted in faster drying and leads to sugary musts that were lighter-coloured, less brown and more aromatic than Pedro Ximenez grapes.