Raman Imaging Spectroscopy as a Tool To Investigate the Cell Damage on Aspergillus ochraceus Caused by an Antimicrobial Packaging Containing Benzyl Isothiocyanate

Raman imaging spectroscopy is a nondestructive analytical method that can be a useful tool to obtain detailed information about the molecular composition and morphology of biological samples. Its high spatial resolution was used to collect spectra of Aspergillus ochraceus, a mold producer of ochratoxin A (OTA), in order to investigate the cell damage caused on it by the action of the antimicrobial benzyl isothiocyanate (BITC). The study was performed in both direct contact and vapor phase, in order to check the use of BITC as active agent in food packaging material. The results showed that there were morphologic alteration and a characteristic Raman spectrum on spore and hyphae exposed to BITC. BITC was accumulated in the mold cells where it caused an enormous amount of alterations in cellular components (lipids, proteins, saccharides, amino acids...) and cellular functions (cell cycle, respiration, metabolism, transcription of genes, fluidity of the cellular wall). All these structural, composition, and metabolic changes will affect the production of OTA. Pattern recognition with chemometrics using principal component analysis (PCA) demonstrated an excellent separation between control and BITC treated samples, both in spores and hyphae. PCA results also showed two different affection levels when samples were exposed to BITC in the vapor phase.