Mid-infrared as a new tool for detecting adulteration in fruit products

This paper illustrates the use of attenuated total reflectance (ATR) spectra of fruit purees or jams, and diffuse reflectance (DRIFT) spectra of jams, to provide the chemical information necessary to check the composition and authenticity of these products. The fingerprint region contains information reflecting the carbohydrate, acid, and pectin content. Although differences between products from different fruit types, or between genuine and adulterated samples, can be seen in the spectra by eye, the samples cannot be identified unambiguously by visual inspection. Statistical methods can aid this identification, however. An example of the use of principal component analysis is presented, enabling genuine raspberry purees to be distinguished from raspberry purees doctored by the addition of sucrose solution to a level of about 6% sucrose.