Seasonal changes in monoterpenes of 'Muscat of Alexandria' grape juice during berry development

Seasonal changes in monoterpene concentrations in the juice of Muscat of Alexandria grape were investigated. Volatile monoterpenes were analyzed by trapping them in the headspace with Tenax-TA. Reproductive results were obtained when headspace gas was trapped at 40 °C for 180 min. In the headspace trapping method, the concentration of each monoterpene was slightly lower compared to those extracted with n-pentane directly from juice. Clear peak separations were obtained by gas chromatography. Linalool increased rapidly from 30 days after veraison and reached a maximum in late September, it then declined. Geraniol increased slowly from the stone hardening stage to the overripe stage. Percentages of linalool and geraniol to total monoterpene at harvest were 66.3 and 27.0, respectively.