Investigation of bread staling by handheld NIR spectroscopy in tandem with 2D-COS and MCR-ALS analysis

•Use of handheld NIR spectroscopy for time-resolved measurements of white bread.•Investigation of bread staling using 2D-COS and MCR-ALS analysis of NIR spectra.•Interpretation of the sequence of structural changes in bread as a function of the observed spectroscopic changes. The present investigations were carried out using the technique of handheld near-infrared (NIR) spectroscopy for time-dependent diffuse-reflection measurements of the cut face of a fresh baguette. The critical structural factors in the staling process of bread are the crystallization of amylopectin in starch and the decrease of water content by evaporation and diffusion from core to crust. To monitor the synchronicity and sequence of these changes, Two-Dimensional Correlation Spectroscopy (2D-COS) was applied. Due to the significant variation of spectral changes at different stages of the aging process, the spectra were split into two sets of 0 – 6/6 – 48 hr. 2D-COS analysis allowed to differentiate the detailed sequence of the following structural events for these time intervals: crystallization of amylopectin/evaporation of weakly and strongly hydrogen-bonded water/reorganization of starch OH-functionalities. Furthermore, Multivariate Curve Resolution-Alternating Least Squares (MCR-ALS) was used to investigate the changes in the spectra profile as a function of aging time.