Monitoring of apple juice fermentation process by 1H-NMR spectroscopy

Cider is a slightly alcoholic beverage obtained from the fermentation of apple juice, largely popular in Europe, North America, and Australia [1,2], constituting an important and promising segment of the fruit industry. In the presented study, a simultaneous characterization of bioactive compounds in apple juice, in the intermediate products of the cidermaking process and in still cider was performed for the first time using Nuclear Magnetic Resonance spectroscopy. Alongside sugar consumption, a progressive increase in different chemical compounds like trigonelline, chalcone, fumarate, caffeic acid, uracil, tyrosol and xanthine content was detected during the alcoholic fermentation process. Interestingly the presence of a relatively high tyrosol content was observed as well, thus conferring additional health benefits to cider [3]. The concomitant changes in phenolic compounds, amino acid and organic acid (malic, lactic, quinic, pyruvic, citric and succinic) content, represent an important task when monitoring the fermentation process in order to assessing the quality of the final product.