Characterisation of Barley Transformation into Malt by Three-Way Factor Analysis of near Infrared Spectra

Abstract

Data collected for the spectral study of time series can be presented as a three-way array in which the three modes are the batches, time and wavelengths. The parallel factor analysis (PARAFAC) model is relevant for the analysis of three-way data tables, while the malting process consists of the time transformation of barley into malt. Furthermore, samples were collected on each day of an industrial malting process and their near infrared spectra were recorded in diffuse reflectance mode from 1100 to 2500 nm. The time and the wavelength modes associated with the first component showed that the spectra intensities allowed the classification of samples according to time. A study of the other loading vectors weighted by their coefficients on the time-mode explain some phenomena taking place during malting [the appearance of soluble substances (1950 nm), β-glucan degradation (2240–2360 nm), moisture modification (1450 and 1950 nm)…]. PARAFAC allowed us to separate batches according to the malting process to which they were submitted. Batches were also differentiated according to the chemical modification rate that occurred as expressed by the biochemical analyses results of the final malts. This work shows that PARAFAC can be a useful tool in the study of time series.