Assessing food by-products macrocomposition by FTIR microspectroscopy.

Food by-products offer a promising opportunity for extracting valuable compounds that can be used in the food, pharmaceutical, and polymer industries. However, unpredictable variations in the chemical composition and spatial distribution of the various components within these biological matrices create challenges for new valorization processes. These inconsistencies can lead to variable recovery efficiency and differing quality of extracts. Understanding the chemical composition and spatial distribution of these components is essential, as it will facilitate the effective valorization of these by-products in future applications. Fourier transform infrared (FTIR) microspectroscopy was employed to evaluate the chemical composition and structural organization of industrial food by-products, specifically potato trimmings, carrot pomace, and brewer's spent grain. Frozen sectioning was employed as a sample preparation method. Hierarchical cluster analysis was applied to differentiate the spectral information from the background, allowing the determination of representative average spectra with good reproducibility across sample replicates. Derivative FTIR spectra further revealed previously hidden information by resolving overlapping signals, such as multiple bands in the 1750-1550 cm region, facilitating the assignment of functional groups to compounds of interest such as proteins, lipids, or pectin and the creation of chemical images. However, some macroconstituents exhibited overlapping absorbance peaks, complicating the precise identification of individual components. Despite this limitation, FTIR microspectroscopy provided valuable semi-quantitative information on the composition of these by-products. The results demonstrated that chemical imaging by FTIR microspectroscopy is a valuable tool for food by-product evaluation, providing insight into their composition and supporting the potential for their valorization in industrial applications.