Evaluation of the pure apple juice content in commercial apple beverages using FTMIR-ATR and potential curves

An attenuated total reflectance Fourier-transform mid-infrared procedure (FTMIR-ATR, 1250 to 900 cm(-1)) has been developed to evaluate the amount of pure apple juice employed to prepare commercial apple juice-based beverages. Samples were classified according to their percentage of pure apple juice using a multivariate technique called potential curves. The two classification patterns defined by the loadings are associated with the general sugar content and the sucrose vs. fructose-plus-lucose ratio. In order to apply the methodology to some commercial beverages synthetic blanks were needed to correct for sugar added to the original juice. The procedure was validated using either laboratory prepared juices (2%, 4%. 6%, 8%, 10%, 16%, 20%, 25%, 50%, 70%, and 100% v/v apple juices), commercial 100% pure juices or commercial soft drinks. The contents of the three main sugars ranged from 0.03-4.65 g 100 mL(-1) for sucrose, 0.05-6.25 g 100 mL(-1) for glucose, and 0.13-6.5 g 100 mL(-1) for fructose. The methodology is fast, precise, and offers useful qualitative information.