*2.3. NIRS Data Acquisition*

A compact, handheld NIR spectrometer device was used (MicroNIR OnSite, developed by VIAVI Solutions Inc., Monza, Italy), working from 900 to 1650 nm, with a resolution of 6 nm. Samples were scanned in transflectance mode, with a special accessory for liquids (MicroNIR side-view vial holder by VIAVI) in small glass vials. A dark measurement (acquired with the lamp turned off) and a white diffuse reflectance standard (a white reference with 99% reflectance) were used for calibration. Each spectrum was the average of 100 scans, with an integration time of 8.2 ms. All spectra were taken in duplicate. For the external validation, the average of two spectra was considered for each sample.
