Ice cider fingerprinting using optical spectroscopy and simple laboratory measurements

Ice cider is a high value specialty product that was developed in Quebec, Canada. It is typically very sweet and has an intense apple taste due to specific production practices. Other fruit wines can be produced at a lower cost, and there is a need for ice cider authentication methods. An experiment was conducted to determine the uniqueness of ice cider in terms of physico-chemistry. Simple laboratory procedures were considered in addition to infrared and fluorescence spectroscopy. One hundred bottles with vintages from 2001 to 2015 were collected. Besides, 11 comparable apple wines (CAW) were selected, including quiet, fortified, aperitif and fire ciders. In addition, 36 'laboratory wines' (LW) were prepared by mixing various juices, ethanol and sugars. A linear discriminant analysis with variable selection was performed to classify products as ice cider or not. Input variables were results from laboratory test or scores from principal component analysis of spectra. Ninety four percent of ice ciders and 45% of CAW were correctly identified by simple laboratory tests but the method was not specific as 6 LWs were confused with ice cider. Infrared spectroscopy or fluorescence at 280, 330, 415 and 460 nm excitation wavelengths allowed for correct classification of 95% of samples and all LW. Infrared was poor at distinguishing CAW (45% correct classification) while fluorescence was better (73% correct classification). Measuring intrinsic fluorescence represents an opportunity for a simple and low cost instrument for the authentication of ice cider.