Detection of aflatoxin B1 level and revelation of its dynamic accumulation process using visible/near-infrared hyperspectral and microscopic imaging

Abstract

Understanding and controlling the dynamic process of aflatoxin B₁ (AFB₁) accumulation by Aspergillus flavus (A. flavus) remains challenging. In this study, the A. flavus development and AFB₁ accumulation were investigated using visible/near-infrared (Vis/NIR) hyperspectral imaging (HSI) on culture media, Potato Dextrose Agar (PDA), PDA + l-glutamine (Gln), and PDA + rapamycin (RAPA). In addition, the levels of AFB₁ in various heterogeneous regions of colonies were measured and their microscopic morphology was characterized. In the temporal and spatial domains, fungal colonies exhibited a concentric circular response pattern. A continuous increase in AFB₁ content was observed in the PDA and PDA + Gln groups as culture time increased. The growth of A. flavus and aflatoxin accumulation were promoted by adding Gln to PDA. However, adding RAPA inhibited the development of fungi and the production of AFB₁. The distribution of AFB₁ across the fungal colony was uneven, and this heterogeneity was associated with the aging and autolysis of the hyphae. Principal component analysis showed that spectral bands of 480, 623, 674, 726 nm were related to the color changes of hyphae and spores during colony growth; however, wavelengths of 840, 882, 867, 972 nm were key bands related to changes in nutritional composition. Multiple preprocessing techniques and modeling methods employed to construct regression models for predicting AFB₁ contents showed that the first-derivative and partial least squares regression (PLSR) provided the best results. A visualization map of AFB₁ levels established using the optimal model showed a spatial pattern similar to the measurement results. This study highlights the application potential of Vis/NIR HSI for monitoring A. flavus growth and AFB₁ content.