Application of NIR spectroscopy and chemometrics in quality control of wild berry fruit extracts during storage

Extracts of wild berry fruits (Bilberry, Cranberry, Raspberry and Strawberry) were analysed using the near infrared spectroscopy (NIRS). NIRS can be used quantitatively and qualitatively to detect, identify, and qualify raw materials like berry fruits and to control their quality. The spectra of fruit products were measured by diffuse trans-reflectance and raw spectra were used for chemometric analysis. The range of NIR used in this research was 904–1699 nm with the aim to use the potential of near-infrared spectroscopy to detect differences between berry-fruits themselves, differences between the sample based on the preparation procedure as well if it is possible to detect the staleness of the samples (fresh and one month old). NIR is a fast and non-destructive analytical method that in association with chemometric modelling becomes a powerful tool for application in food industry. The chemometric methods applied to the recorded NIR data were classification analysis based on principal component (PC) scores and partial last squared regression (PLSR) model. Analyses of the spectrums reveals changes in specific wavelengths of 904-1181 nm that are related to the 3rd CH overtone and 2nd overtone of the OH stretch of H2O as well as in the range of 14341635 nm which correspond to C–H combinations and the 1stovertone of the bonds. The simple PLS regression showed that the influence of the storage on the NIR spectra of samples is high (R2=0.79). This study showed that near infrared spectroscopy has potential to distinguish extracts based on unprocessed freshwild berry fruit extracts, sample preparation procedure and their quality decrease affected by the storage. All findings indicate the advisability of use of NIR for on-line monitoring of product quality and selection.