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RESEARCH PRODUCT

PLS-NIR determination of total sugar, glucose, fructose and sucrose in aqueous solutions of fruit juices

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Abstract An analytical procedure has been developed for the direct determination of sugars in fruit juice samples. The method is based on the partial least-squares (PLS) treatment of first derivative near infrared (NIR) spectroscopic data obtained between 1200 and 2450 nm, using 1 mm pathlength cell and a multicomponent calibration set, including seven binary mixtures and 10 ternary mixtures of glucose, fructose and sucrose. The limit of detection values found are of the order of 0.2 g/100 ml for total sugar and 0.2, 0.4 and 0.5 g/100 ml for glucose, fructose and sucrose, respectively. Relative standard deviation values obtained vary from 0.4% to 2.3% for six independent measurements of individual sugar concentrations from 15.4 to 2.4 g/100 ml and 0.03% for total sugar of the order of 20 g/100 ml. Average recovery percentages of 99 ± 2 for total sugar and between 98 ± 4 and 100 ± 4 for single sugar determinations evidence the applicability of the methodology developed for the analysis of juice samples.