Development of decolorization and degreasing reagents for optical clearing that enables visualization of the three-dimensional microstructure inside foods

The combination of optical clearing and fluorescence observation as an imaging method shows promise for visualizing the microstructure inside foods, which is a key determinant of its quality. However, an efficient method of decolorization and degreasing during the sample-clearing step, which is essential for suppressing light scattering inside foods during fluorescence observation, remains unclear. In this study, by utilizing a simple yet effective high-throughput evaluation system, 22 different reagents that were prepared by varying the dilution concentration and mixing ratio of 10 different reagents were screened. As a result, new reagents which can effectively remove carotenoid pigments in durum-noodles, carotenoid pigments and chlorophyll in radish sprouts and spinach, and oil in deep-fried noodles were developed. The developed decolorizing reagent removed 98.5, 95.9, and 97.3 % of lutein from durum-noodles, radish sprouts, and spinach, respectively, and the developed degreasing reagent removed 99.6 % of oil from deep-fried noodles. Furthermore, we demonstrated that decolorization and degreasing to reduce light scattering can enable the acquisition of high-contrast microstructure images in the deeper part of foods using a versatile fluorescence microscope.