Rapid quantification of total polyphenol content in EVOO using NIR sensor with wavelength selection and FS-MLR

Olive oil quality is regulated by an European normative, and according to different chemical and organoleptic markers the olive oil can be labelled as lampante, virgin or extra virgin olive oil (EVOO), being the last the top-quality one. Since these parameters determine mainly the olive oil chemical stability, in the last years different works have studied the favourable influence of others olive oil minor components on the human health. Polyphenols are one of these minor components. This research has been carried out to study the correlation between the polyphenols contained into EVOO and its spectral response in the near infrared. The selection of the best correlated spectral wavelengths could be the first step to build a rapid and low-cost NIR sensor to be set up into the elaboration process in order to control the presence of these components. During the process, several olive oil variables such as temperature, humidity, turbidity... could affect to the NIR response. In this sense, this work has studied the influence of the olive oil turbidity on the error of polyphenol content prediction. For this study 63 olive oil samples obtained from an olive oil mill have been employed and the reference values were obtained by an external laboratory with chemical analysis. Spectra were filtered with an ANOVA analysis and the best correlated band was identified between 1690 and 1870 nm. The regression algorithm FSMLR was used and it got a RMSECV of 75 ppm, the R² coefficient was 0.94 and the RPD value was 4.76. The results get worse when samples with different turbidity indexes were used.