The calibration models of alcohol strength and titratable acidity
were developed using PLS regressions with leave-one-out cross
validation. The PLS regression is a technique that constructs new
predictor factors derived by taking into account the variation inspectral data that is relevant for explaining variation in the characteristics
of interest in original samples (Li, Zhang, & Atungulu,
2014; Williams, 2001), and it is also one of the standard methods
used to develop calibration equations to predict chemical compositions
of a sample from NIR spectra (Reeves, 2001).