The potential of NIR spectroscopy for the detection of the adulteration of orange juice

Near‐infrared spectroscopy was used to investigate the adulteration of 65 authentic concentrated orange juice samples obtained from Brazil and Israel. These samples were adulterated with 100 g kg−1 additions (ie 100 g added to 900 g) of (1) orange pulpwash, (2) grapefruit juice, and (3) a synthetic sugar/acid mixture and with 50 g kg−1 additions (ie 50 g added to 950 g) of (4) orange pulpwash, and (5) grapefruit juice. All samples were scanned on the NIR systems 6500 spectrophotometer over the 1100‐2498 nm wavelength range. Principal component analysis was used to reduce each spectrum to 20 principal components. Factorial discriminant analysis was used to distinguish between the different sample groups. Using orange juice and orange juice adulterated at the 100 g kg−1 level, accurate classification rates of 94–95% were obtained. To classify samples adulterated at the 50 g kg−1 level, the calibration development sample set had to be augmented by the inclusion of samples adulterated at this lower level—after this augmentation, an accurate classification rate of 94% was obtained. The results demonstrated that the application of principal component and factorial discriminate analysis to NIR reflectance spectra can detect the adulteration of orange juice with an average accuracy of 90%. Furthermore, not one adulterated sample was predicted as being an authentic orange juice throughout the entire test regime.