Abstract
The nutritional effects of fruit juices, combined with the added value of a probiotic, provide a plant-based fortified functional food. Some process-related drawbacks are caused by the pH parameter, which will affect the survival of probiotics during their industrial processing and storage. By means of developing a monitoring method for probiotic activity, the present study aims to investigate the application of near-infrared spectroscopy (NIR) as a correlative analytical method for fermentation process tracking, in association with the different absorption patterns of bound water, explained by aquaphotomics. The data evaluated in the wavelength range of 1300-1600 nm indicate classification accuracies of 99-100% and 99-93% during calibration and validation, respectively, when applying PCA-LDA for discriminating the fermentation times, for each one of the single and mixed bacterial groups. During PLSR prediction, according to the fermentation times, the validation models developed for pH show coefficients of determination in the range of 0.96 to nearly 1 and root mean square errors of 0.05 and 0.19. On the other hand, for the PLSR prediction of log cell count (CFU/mL), validation modeling shows a coefficient of determination of 0.85 and a root mean square error of 0.23. All things considered, the results support the applicability of combining NIR and aquaphotomics as a bioprocess monitoring tool, which can be further implemented in different studies and industrial contexts.